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  • An integrated multiple reaction monitoring strategy based on predicted precursor ions and characteristic product ions for global profiling Rubiaceae-type cyclopeptides in three Rubia species
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-21
    Qirui Bi; Qiao Liu; Sha Han; Lu Zhang; Longsheng Xing; Xuejia Zhang; Zhe Wang; Yuanyuan Miao; Ninghua Tan

    Complexity and diversity of natural compounds make it a challenge for globally profiling constituents in multiple species plants, especially for minor new compounds. Rubiaceae-type cyclopeptides (RAs) are one kind of active constituents and characteristic components in Rubia plants, particularly Rubia cordifolia (RC), which is one kind of traditional Chinese medicines. In this study, a new multiple reaction monitoring strategy (PPCP-MRM) based on predicted precursor ions and characteristic product ions was developed to globally profile RAs in RC and its two main adulterants, including Rubia alata (also named Jinjiancao in Chinese) (RAJ) and Rubia podantha (RP). Moreover, characteristic components of these species have been found by targeted relative quantitative analysis of RAs by LC-MS. In total, 39 RAs have been structurally annotated based on fragment ions in MS2 data, including 19 new compounds. In addition, 7 RAs as the chemical markers were found to distinguish these three Rubia species. The results indicated that this PPCP-MRM integrated strategy is a powerful tool for comprehensive analysis of RAs and screening chemical markers for Rubia species discrimination, which would be useful for distinguishing Rubia adulterants. Furthermore, this developed strategy could also be a useful tool for analysis of other cyclopeptides.

    更新日期:2020-01-21
  • A functionalized magnetic covalent organic framework for sensitive determination of trace neonicotinoid residues in vegetable samples
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-18
    Junyu Lu; Rui Wang; Jingyi Luan; Yijun Li; Xiwen He; Langxing Chen; Yukui Zhang

    A functionalized magnetic covalent organic framework containing the nitro groups (Fe3O4@COF-(NO2)2) with core-shell structure was synthesized for magnetic solid phase extraction (MSPE) of six neonicotinoid insecticides residue in vegetable samples. The structure of Fe3O4@COF-(NO2)2 was investigated by various characterization techniques. The Fe3O4@COF-(NO2)2 exhibits the excellent thermal and chemical stability, high surface area (254.72 m2•g−1), total pore volume (0.19 cm3•g−1), high magnetic responsivity (27.7 emu•g−1), which can be used as an ideal adsorbent for rapid isolation and enrichment of target analytes. A sensitive method was developed by using Fe3O4@COF-(NO2)2-based MSPE coupled with HPLC with UV detection. It offered good linearity within the range of 0.1-30 ng•mL−1, low limits of detection (S/N=3) of 0.02-0.05 ng•mL−1. Furthermore, high enrichment factors of 170-250 for six neonicotinoid insecticides were obtained. The applicability of Fe3O4@COF-(NO2)2 is demonstrated for measuring trace neonicotinoid residues in vegetable samples with satisfactory recoveries, which ranged from 77.5 to 110.2 %. The results indicated that the Fe3O4@COF-(NO2)2 microspheres offer great potential for efficient extraction of neonicotinoid insecticides from complex samples.

    更新日期:2020-01-21
  • Implementation of a ultraviolet area imaging detector for analysis of polyvinyl alcohol microbubbles by capillary electrophoresis
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-18
    Leila Josefsson; David Goodall; Åsa Emmer

    Contrast agents are widely used to enhance the image quality in clinical imaging using e.g. ultrasound. The contrast agents used for ultrasound imaging are mainly microbubbles (MBs) with a soft or hard shell encapsulating a core of gas. In the present study, MBs with a hard shell of polyvinyl alcohol (PVA), and a core of air were analysed in a capillary electrophoretic system using a UV area imaging detector. The detector was operating at 3 wavelengths; 214 nm, 255 nm and 525 nm, and the highest absorbance for individual PVA-MBs were obtained at 214 nm. Two detection windows and a vertical loop capillary position enabled tracking of the PVA-MBs both in an upward and a downward flow direction, where PVA-MBs had different flow distributions and slightly higher average flow velocity upwards, attributed to temperature differences in the capillary that was part within the instrument and part outside. The tracking also allowed counting and quantification of the PVA-MBs. Separation of PVA-MBs from proteins present in human blood plasma was achieved, with multi-wavelength imaging showing best contrast at 525 nm. The PVA-MBs absolute values of negative zeta potential and anionic mobility when injected from plasma in the pH 12 background electrolyte are higher than those obtained for MBs injected from buffer, consistent with their increased negative charge due to a protein corona coating of the PVA-MBs.

    更新日期:2020-01-21
  • A strategy of untargeted foodomics profiling for dynamic changes during Fu brick tea fermentation using ultrahigh-performance liquid chromatography-high resolution mass spectrometry
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-17
    Wei Jia; Qingyun Shi; Lin Shi; Junzhe Qin; James Chang; Xiaogang Chu

    During a microbial fermentation process, the chemical composition of Fu brick tea changed substantially. To better profile the unique changes of metabolites and lipids in Fu brick tea at different fermentation stages, a multifaceted strategy combining untargeted foodomics with UHPLC-Q-Orbitrap analysis was developed. The discriminative tea metabolites and lipids were determined by statistical analysis and online database matching. A total of 12 characteristic components (3 metabolic and 9 lipid variables) were found to differ significantly among samples. Quantitative analysis showed that, except for trimyristin and incensole acetate, the content of these compounds gradually increased and finally stabilized with increasing fermentation time. The simultaneous determination of metabolites and lipids in this study provided detailed information for the analysis of multi-component changes in a complex matrix.

    更新日期:2020-01-21
  • Rapid Extraction Method of Polycyclic Aromatic Compounds in Soil using Basic Silica Selective Pressurized Liquid Extraction
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-17
    Ivan A. Titaley; Ulrika Eriksson; Maria Larsson

    Complex chemical mixtures found in soils at contaminated sites typically includes polycyclic aromatic compounds (PACs), thus posing potential environmental and human health risks. Pressurized liquid extraction (PLE) followed by silica clean-up is one of the most often used extraction methods for PACs in soil. While silica clean-up provide satisfactory recovery of oxygenated polycyclic aromatic hydrocarbons (OPAHs), this technique provides limited recovery of azaarenes. In this work, we used PLE and in-cell clean up with basic silica to increase the recovery of OPAHs and azaarenes. The optimized selective pressurized liquid extraction (SPLE) method used 4 g basic silica, dichloromethane, 100% flush volume, 100 and 120°C extraction temperatures, with two static cycles for each temperature, no rinse in between the two extractions, and 20 and 120 s purge for the first and second extraction temperature, respectively. The method was validated for a wide range of PAC groups, including OPAHs, azaarenes, alkylated PAHs, and sulfur heterocycles (SPACs), in total 87 PACs, using certified reference material and in comparison to the results from previous inter-laboratory data. Our SPLE method yielded results that are in agreement with certified values and inter-laboratory data from prior analysis. The SPLE method also yielded lower variation than the results from the inter-laboratory data for analysis of OPAH and azaarenes, suggesting better precision than previous methods. More importantly, the SPLE method increases sample analysis throughput as extra clean-up step is not necessary anymore. The SPLE method was then successfully applied to rapidly screen PACs in three soil samples.

    更新日期:2020-01-17
  • Introducing Online Multicolumn Two-dimensional Liquid Chromatography Screening for Facile Selection of Stationary and Mobile Phase Conditions in both Dimensions
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-16
    Heather Wang; Hayley R. Lhotka; Raffeal Bennett; Miraslava Potapenko; Chad J. Pickens; Benjamin F. Mann; Imad A. Haidar Ahmad; Erik L. Regalado

    Baseline separation and analysis of multicomponent mixtures of closely related pharmaceuticals using a single column selectivity can often be challenging, requiring the combination of orthogonal stationary and mobile phase methods to monitor all the species and optimize reaction outcomes. In recent years, two-dimensional liquid chromatography (2D-LC) has become a valuable tool for improving peak capacity and selectivity. Though powerful, standard 2D-LC instrumentation and software can often lead to tedious method development and has a requirement for very specific expertise that is poorly suited for a fast-paced industrial environment. In this regard, the introduction of an automated online 2D-LC setup that could screen multiple columns in both dimensions without manual intervention will undeniably serve to streamline column/mobile phase selection and secure the viability of 2D-LC as a mainstay instrument for industrial applications. Herein, we introduce and investigate a multicolumn online 2D-LC approach that simplifies column screening and method development dramatically. This setup incorporates 6-position column selection valve technology whose functionality enables us to combine multiple columns in the first and second dimensions. This strategy in conjunction with diode array detection (DAD) in both dimensions and mass spectrometry (MS) acquisition in the second dimension serves to explore different columns and mobile phases as a framework for screening targeted compounds in multicomponent mixtures without having to perform chromatographic purification. Multiple online heartcutting achiral RPLC – achiral RPLC and achiral RPLC – chiral RPLC coupled to DAD and ESI-MS methods combining several stationary phase selectivity in an automated fashion are successfully applied to the separation and analysis of complex mixtures of drug substances, where in many instances, traditional 1D-ultra-high performance liquid chromatography (UHPLC) fails or delivers sub-optimal results. This automated online multicolumn 2D-LC workflow enables rapid and efficient identification of column/eluent combinations, as well as sample analysis across multiple column in both dimensions overnight with a single click.

    更新日期:2020-01-17
  • Comments on “Classification of biphasic solvent systems according to Abraham descriptors for countercurrent chromatography”
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-15
    William E. Acree; Brittani Churchill; Michael H. Abraham

    Abraham model correlations reported by Marlot and coworkers for the 1-octanol/water, 1-butanol/water, ethyl acetate/water, and heptane/methanol biphasic partitioning systems are compared to previously published Abraham model correlations. The previously published correlations for the fore-mentioned partitioning systems are based on more experimental data points, and exhibit much better descriptive ability as evidenced by much smaller standard deviations/standard errors and larger squared correlation coefficients.

    更新日期:2020-01-16
  • Aqueous extraction followed by dispersive solid phase extraction with in situ derivatization for the determination of aflatoxins in traditional Chinese medicines
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-15
    Nan Wang; Chunfeng Duan; Shenghong Li; Xuhui Geng; Kun Ding; Yafeng Guan

    A green sample preparation method based on aqueous extraction followed by dispersive solid phase extraction (d-SPE) with in situ derivatization (ISD) was developed for the determination of aflatoxins (AFs) in traditional Chinese medicines (TCMs). AFs in TCMs were extracted by alkaline aqueous solution and converted to substituted coumaric acids. Then, mixed-mode anion exchange (MAX) sorbent was used to isolate and enrich the substituted coumaric acids. During the elution by acetonitrile/trifluoroacetic acid solution, AFs were reconstructed and in situ derivatized. Several parameters affecting the procedure were evaluated. The developed preparation method coupled with high performance liquid chromatography-fluorescence detection was successfully applied for AFs determination in TCMs. The limit of detection (LOD) reached 10 pg/mL for AFs. Good linearity was obtained in three orders of magnitude with correlation coefficients ranging from 0.9996 to 0.9999. The relative recoveries of the method were between 72.7%-114.5% with intra- and inter-day relative standard deviations (RSDs) less than 9.5% and 10.1%, respectively. The method was successfully applied to determine AFs in 15 kinds of TCMs in China, with the results verified by IAC standard method.

    更新日期:2020-01-15
  • Dual-retention mechanism of dopamine-related compounds on monolithic stationary phase with zwitterion functionality
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-15
    Martina Komendová; Jiří Urban

    Seven retention models have been selected to describe a dual-retention behavior of ten dopamine-related compounds on polymer-based monolithic stationary phase with zwitterion sulfobetaine functionality. Regression quality, as well as a statistical significance of individual regression parameters, have been evaluated. Better regression performance showed two four-parameter models when compared to three-parameter models. On the other hand, limited number of experimental points disqualified statistical robustness of four-parameter models. Among three-parameter models, retention description introduced by Horváth and Liang provided comparable quality of regression at significantly improved robustness. Multivariate analysis of the best three-parameter models provided the description of physicochemical properties of dopamine precursors and metabolites. Principal component analysis and logistic regression allowed structural characterization of dopamine-related compounds based solely on regression parameters extracted from an isocratic elution data. Both polarity and type of functional groups has been correctly assigned for 3-methoxytyramine that has not been part of an evaluation study. Among applied dual-retention models, Horváth´s model, initially developed to describe a retention of ionic compounds on nonpolar stationary phases, provided robust regression of experimental data and allowed an extraction of structural characteristics of dopamine-related compounds

    更新日期:2020-01-15
  • Purification of supercoiled p53-encoding plasmid using an arginine-modified macroporous support
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-15
    J.F.A. Valente; A. Sousa; G.A. Azevedo; J.A. Queiroz; F. Sousa

    p53 is a tumour suppressor gene that has been explored for cancer gene therapy as a possible alternative to the common treatments. The use of plasmid DNA (pDNA) to carry the therapeutic gene has been considered, but it is requisite to preserve its supercoiled (sc) structure, for eliciting a more effective gene expression and therapeutic action. The purification of the sc pDNA using amino acids-based affinity chromatography has been successfully applied, exploring different amino acids and supports. From these studies, it stood out the selectivity of arginine for the recognition of sc pDNA. However, some limitation on the binding capacity was found in the arginine-agarose support, and in the case of monoliths, some fouling and clogging can limit sequential runs. By using macroporous support modified with arginine it was expected to take advantage of the selectivity of the ligand combined with the flow properties and binding capacity offered by the support. The arginine-modified macroporous support was characterized by SEM, EDX and FTIR also to verify the correct immobilization of arginine, and then used for pDNA purification. The support showed to be effective on the sc p53-pDNA isolation, and the robustness was also achieved by accomplishing the purification of plasmids with different sizes, only by slightly adjusting the experimental conditions. Regarding the dynamic binding capacity of the arginine-modified macroporous support, it was achieved an improvement of more than 50% in the pDNA binding capacity when compared with their homologous arginine-agarose commercial matrix, suggesting potential economic feasibility in case of scale-up.

    更新日期:2020-01-15
  • Ultrasound-assisted synthesis of clover-shaped nano-titania functionalized covalent organic frameworks for the dispersive solid phase extraction of N-nitrosamines in drinking water
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-15
    Yun Zhang; Yong-Gang Zhao; Nadeem Muhammad; Ming-Li Ye; Yan Zhu

    In this study, three batches of nano-titania functionalized covalent organic frameworks were acquired depending on different solvothermal reaction stages (24 h, 48 h and 72 h), which were named as single roll-up shaped nano-titania functionalized COFs (SSTF-COFs), double roll-up shaped nano-titania functionalized COFs (DSTF-COFs) and clover-shaped nano-titania functionalized covalent organic framework (CSTF-COFs), respectively. After comparing their extraction performances, the more efficient and stable CSTF-COFs were selected as sorbent for the dispersive solid phase extraction (dSPE) of eight target N-nitrosamines in drinking water, followed by the determination with liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS). Owing to the introduction of hydroxy groups, CSTF-COFs showed high extraction efficiency for N-nitrosamines with a wide range of polarities through hydrogen bonding interaction, hydrophobic interaction and hydrophilic interaction. Under optimum conditions, the developed method provided relatively low limits of detection (0.13-2.45 ng/L) and satisfactory recoveries (88.6-105.5 %), with relative standard deviations (RSDs) less than 8.3 %. Therefore, with the assistance of CSTF-COFs, trace levels of N-nitrosamines were quantitatively and sensitively determined in 31 out of 460 bottled drinking water samples in a sensitive and convenient way.

    更新日期:2020-01-15
  • A flow distribution and collection feature for ensuring scalable uniform flow in a chromatography device
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-15
    Raja Ghosh; Guoqiang Chen; Umatheny Umatheva; Paul Gatt

    We discuss how the efficiency of a chromatography device could be enhanced by incorporating a new feature which ensures flow uniformity. The overall flow of fluid within the device, which has a cuboid shape, could be visualized as a combination of two z patterns. The device is therefore designated as cuboid z2. The reason for flow uniformity is explained using a simple mathematical model, and based on computational fluid dynamic (CFD) simulations. The cuboid z2 device substantially outperformed its equivalent column in terms of separation efficiency metrics such as the number of theoretical plates, reduced plate height, and attributes of non-interacting solute tracer peaks. The results discussed in this paper clearly indicate the suitability of using the cuboid z2 device for high-resolution chromatographic separations. The z2 flow enhancing feature would also be broadly applicable to any situation requiring uniform flow in three-dimensional porous media. In addition to superior fluidic attributes, the cuboid z2 device is expected to have other advantages such as compactness and scalability.

    更新日期:2020-01-15
  • A new strategy for the preparation of mixed-mode chromatographic stationary phases based on modified dialdehyde cellulose
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-13
    Jie Gao; Guoying Luo; Zhan Li; Hui Li; Liang Zhao; Hongdeng Qiu

    A new strategy for the preparation of mixed-mode chromatographic stationary phases based on modified dialdehyde cellulose was proposed. Two novel mixed-mode chromatographic stationary phases, dicarboxyl cellulose-modified silica (DCC/SiO2) and (S)-α-phenylethylamine-bonded DCC/SiO2 ((S)-α-PEA/DCC/SiO2), were prepared by utilizing the easy functionalization characteristics of dialdehyde cellulose. The chromatographic evaluation showed that DCC/SiO2 column could be used in hydrophilic interaction liquid chromatography (HILIC) and ion exchange chromatography (IEC) modes, (S)-α-PEA/DCC/SiO2 column could be used in HILIC, IEC and chiral separation modes. The DCC/SiO2 column and (S)-α-PEA/DCC/SiO2 column exhibited excellent chromatographic performance by separating strongly polar compounds, phenylamines and chiral compounds in the above separation modes. The preparation method of modified dialdehyde cellulose-based mixed-mode chromatographic stationary phases was simple, and also provided a new idea for the development of the subsequent novel mixed-mode chromatographic stationary phases.

    更新日期:2020-01-14
  • Hyphenation of capillary zone electrophoresis with mass spectrometry for proteomic analysis: optimization and comparison of two coupling interfaces
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-13
    Marie-Jia Gou; Gwenaël Nys; Gaël Cobraiville; Alice Demelenne; Anne-Catherine Servais; Marianne Fillet

    Capillary electrophoresis tandem mass spectrometry (CE-MS/MS) is an interesting tool for proteomic analysis as the separation principle is orthogonal to liquid chromatography tandem mass spectrometry (LC-MS/MS). The combination of both techniques can bring complementary information to enlarge proteome coverage. In this study, sample preconcentration techniques were investigated in order to improve sample loading and therefore sensitivity. Dynamic pH junction (DPJ) was found to be the most interesting approach by using 200 mM ammonium acetate (NH4Ac) adjusted to pH 10.0 as sample matrix. The use of DPJ allowed the identification of more peptides and proteins compared to conventional injections. Moreover, the sheath liquid (SL) composition was optimized in order to enhance signal intensity. A nanoflow SL interface (EMASS-II) was compared to the traditional coaxial SL interface (Triple tube) in terms of number of identified and proteins as well as detection sensitivity (peak area and peak height). MS acquisition was performed using both data-dependent acquisition (DDA) and data-independent acquisition (DIA) modes. The results showed that the combined use of these two acquisition modes provided additional information in terms of identification. Moreover, the use of EMASS-II interface allowed the identification of approximately two times more peptides and proteins. Besides, there was an improvement in sensitivity using EMASS-II as peak height and peak area were improved by 4 and 6-fold, respectively, compared to the Triple tube. Altogether, by combining an efficient sample preconcentration method, a nanoflow CE-MS interface and a hybrid ion-mobility qTOF mass spectrometer, a satisfying sequence coverage was obtained by analyzing 1 µg of E. coli proteome digest.

    更新日期:2020-01-14
  • Cationic polyelectrolyte/graphene oxide as an efficient sorbent for the extraction and analysis of trace acidic herbicides in vegetables
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-13
    Xiudan Hou; Hui Yu; Shihai Yan; Junxia Xiao; Min Sun; Wei Wu

    The facile preparation and characterization of a cationic polyelectrolyte (polydiallyldimethylammonium chloride, PDDA) fabricated graphene oxide-grafted silica microsphere ([email protected]@Sil) with high positive charge density as the sorbent for the high selective capture of acidic herbicides were reported. The theoretical calculation showed that there were strong adsorption energies between the PDDA and analytes, and the main interaction was the hydrogen bonding from O-H‧‧‧Cl and C=O‧‧‧H-C. Static- and dynamic- state adsorption results indicated that acidic herbicides were the monolayer coverage onto the [email protected]@Sil due to the electrostatic attraction between the sorbent and analytes, and electrostatic repulsion among analytes. Under the optimized conditions obtained with the single-factor experiment and response surface methodology, this established method was used for the enrichment and determination of herbicides in two vegetables. Method detection limits were in the range of 0.75-1.50 μg L−1 indicating that the introduction of PDDA provided the excellent extraction capacity toward acidic herbicides. The obtained results exhibited that the developed method was feasible, reliable, selective and accurate for the determination of acidic herbicides in real samples.

    更新日期:2020-01-13
  • Air-assisted liquid-liquid microextraction based on solidification of floating deep eutectic solvent for the analysis of ultraviolet filters in water samples by high performance liquid chromatography with the aid of response surface methodology
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-13
    Kaige Zhang; Shuangying Li; Yunhe Wang; Jing Fan; Guifen Zhu

    For this work, a novel air-assisted liquid-liquid microextraction based on solidification of floating deep eutectic solvent (AA-LLME-SFDES), coupled with a high performance liquid chromatography (HPLC) method was developed for the detection of benzophenone and salicylate ultraviolet filters in water samples. Three types of fatty acid-based hydrophobic deep eutectic solvents (DESs) with low viscosity, low-density, and melting point close to room temperature were prepared and employed as extraction solvents. This air-assisted liquid-liquid microextraction was carried out in a glass centrifuge tube. Subsequently, the glass tube was introduced into ice-water bath and held for 3 min, during which the upper DES phase was solidified. The water phase was easily extracted using a syringe equipped with a long needle, and later, the glass tube was removed from ice-water bath. The solidified DES phase was immediately melted at room temperature and used for HPLC analysis. The response surface methodology was employed to optimize some influencing parameters such as the volume of the extraction solvent, the pH value of sample solution, the number of extraction cycles, and the addition of salt. A quadratic model, namely a central composite design, was used to replace the conventional single factor analysis. It was found that under optimal conditions, the limits of determination and quantification were 0.045-0.54 µg L−1 and 0.15-2.0 µg L−1, respectively. The relative standard deviations for inter-day (n=5) and intra-day (n=5) precision were ≤ 4.2%, whereas the enrichment factors for the ultraviolet filters were obtained from 41 to 50. Furthermore, this novel method was successfully employed for the detection of benzophenone and salicylate ultraviolet filters from real water samples. The recoveries ranged from 87.5% to 105.8%, whereas the RSDs were lower than 3.6%.

    更新日期:2020-01-13
  • Energy-efficient and environment-friendly method to prepare monodispersed silica stationary phases for simultaneous separation of compound drugs
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-13
    Zhixia Huo; Qian-Hong Wan; Lei Chen

    An energy-efficient and environment-friendly approach to prepare porous monodispersed micro-sized silica particles with methyltrimethoxysilane (MTMS) as the precursor is described. The particles were synthesized by a two-step hydrolysis/condensation procedure, with post-synthetic aging and calcination for methyl group removal. They show uniform spherical morphology, narrow particle size distribution (D90/10, 1.2-1.6), tailored particle size (3, 5, 7 μm) and mesopore structure (10, 13 nm), which can be directly used as packing materials for HPLC without size classification. C18, sulfonate, and C18/sulfonate mixed-mode stationary phases were produced by a green vapor deposition method based on the synthesized silica particles. The newly synthesized C18 phase exhibits mechanical stability, kinetic behavior and separation performance expected from the commercial C18 column. The C18/sulfonate phase exhibits prominent mixed-mode retention behavior which can be applied to the simultaneous separation of multiple substances in the compound drugs.

    更新日期:2020-01-13
  • Alternative Method to Study the Radial Dispersion in Liquid Chromatography Columns. Part II: Experimental
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-12
    Yoachim Vanderheyden; Ken Broeckhoven; Gert Desmet

    The present contribution reports on the practical implementation and validation of a new experimental method to determine the radial dispersion (Drad) in packed bed liquid chromatography columns, as well as on the results obtained with it. A first important validation was that the measured Drad-values were independent of the applied relative central flow rate (varied from 25% to 57%). The obtained Drad-values did not vary significantly when changing the concentration of the injected tracer to check potential mass overloading effects (25, 50 or 75 ppm of tracer for the acetophenone measurements; 12.5 and 25 ppm of tracer for the toluene measurements). And yet another important validation step was the observation that the Drad-values clearly converged to the value of Deff for velocities going to zero, as physically and theoretically expected. Plotting the obtained results as a plot of Drad/Dmol versus the reduced velocity ν, a quasi-linear relationship is obtained. The slope of the curve (β = 0.38 and β = 0.46 for toluene and acetophenone, respectively) is significantly larger than the value that is most frequently cited in engineering literature. However, the obtained β-values and Drad/Dmol-values still fall within the broad range of β- and Drad/Dmol-values cited in literature.

    更新日期:2020-01-13
  • Rational design of affinity ligands for bioseparation
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-11
    Manuel JB Matos; Ana S Pina; ACA Roque

    Affinity ligands have been the cornerstone in protein purification. The selective nature of the molecular recognition interactions established between a ligand and its target provide the basis for efficient capture and isolation of purification processes. The plethora of affinity adsorbents available in the market reflects the importance of affinity chromatography in the bioseparation industry. Ligand discovery relies on the implementation of rational design techniques, which provides the foundation for the engineering of novel affinity ligands. The main goal for the design of affinity ligands is to discover or improve functionality, such as increased stability or selectivity. However, the methodologies must adapt to the current needs, namely to the number and diversity of biologicals being developed, and the availability of new tools for big data analysis and artificial intelligence. In this review, we offer an overview on the evolution of rational design techniques, dating back to the years of early discovery up to the current and future trends in the field.

    更新日期:2020-01-13
  • A biphasic system based on guanidinium ionic liquid: Preparative separation of eicosapentaenoic acid ethyl ester and docosahexaenoic acid ethyl ester by countercurrent chromatography
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-11
    Chen Fan; Lijiao Wen; Xueli Cao

    Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are high nutritional components. Evidence for unique effects of them is increasing. Further understanding of their independent biological functions urgently needs more efficient separation techniques. Nowadays, most of the commercially available fish oil products are the mixture of eicosapentaenoic acid ethyl ester (EPAEE) and docosahexaenoic acid ethyl ester (DHAEE). It will be convenient to directly separate esterified EPA and DHA without saponification pretreatment. However, it is of great challenge to separate EPAEE and DHAEE because of their extremely fat-soluble nature and the equivalent chain length rule. In this research, the suitability of green guanidinium ionic liquid (IL) in countercurrent chromatography (CCC) solvent system for the separation of them was evaluated for the first time. Compared with imidazolium IL and phosphonium IL, guanidinium IL based non-aqueous biphasic system showed more outstanding separation performance. The separation mechanism was elucidated in depth through quantum mechanical calculations. It was found that guanidinium IL acted a crucial role in the CCC separation, which resulted in difference of partition behavior of EPAEE and DHAEE via different hydrogen-bonding affinity. EPAEE and DHAEE were successfully separated by solvent system (n-heptane/methanol/propylguanidinium chloride ([C3Gun]Cl, 1:1:5%, v/v/m)) with high purity (> 95%) in one step, which was not achieved beforehand. Moreover, an easy recycling procedure of IL had also been devised, which significantly reduced waste generated. It opens up a new way for reasonable design water-free two-phase solvent system for efficient separation of very non-polar lipid compounds.

    更新日期:2020-01-13
  • A crosslinked, low pH-stable, mixed-mode cation-exchange like stationary phase made using the thiol-yne click reaction
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-11
    Erin P. Shields; Stephen G. Weber

    Mixed-mode cation-exchange stationary phases are useful for the separation of mixtures containing hydrophobic, acidic, and basic molecules. To ensure that weak organic bases are protonated and carboxylic acids are neutral low pH mobile phases are required. Mixed-mode stationary phases that are stable at pH < 3 are needed. We synthesized a crosslinked structure along the surface of thiol functionalized silica gel particles using the thiol-yne click reaction. The alkyne, 1,7-octadiyne, was added to the 3-mercaptopropyl silica gel, then crosslinked using 1,6-hexanedithiol. Elemental analysis showed low octadiyne ligand surface coverage, but, stoichiometrically, three sulfurs were added to each octadiyne ligand during the crosslinking step, indicating that crosslinking occurred. The effect of the crosslinking on the stability was tested with a 50:50 (v/v) pH 0.50 5% TFA aqueous:acetonitrile mobile phase at 70 °C for six days, over 35000 column volumes. The stationary phase showed good stability with the retention of triphenylene decreasing only 20% during that time. The Tanaka test showed that the phase has a methylene selectivity of 1.20 ± 0.04, a high shape selectivity of 2.71 ± 0.03, and a 3.98 ± 0.05 cation-exchange factor at pH 2.70. The phase has a selectivity factor for nitrobenzene and benzene of 1.41 ± 0.01, indicating the electron donating charge transfer characteristic of the phase. The mixed-mode characteristics of the phase were investigated using a mixture of the monoamine neurotransmitters norepinephrine, dopamine, and serotonin. Baseline resolution of the monoamines could be obtained using a simple 20 mM potassium phosphate (pH 2.70)/methanol mobile phase. Altering both the methanol content and the potassium ion concentration altered the retention of the monoamines indicating mixed-mode cation exchange characteristic of the crosslinked stationary phase.

    更新日期:2020-01-13
  • A new sensitive method for the simultaneous chromatographic separation and tandem mass spectrometry detection of anticoccidials, including highly polar compounds, in environmental waters
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-10
    D. Mooney; C. Coxon; K.G. Richards; L. Gill; P.-E. Mellander; M. Danaher

    A sensitive and selective method was developed and validated for the determination of 26 anticoccidial compounds (six ionophores and twenty chemical coccidiostats) in surface and groundwater samples at parts-per-quadrillion (pg L−1) to parts-per-trillion (ng L−1) levels by ultra-high performance liquid chromatography with tandem mass spectrometry detection (UHPLC-MS/MS). A range of different analytical columns and mobile phase compositions were evaluated to enhance selectivity and retention of a number of highly polar and basic anticoccidials along with other non-polar coccidiostats. A combined separation, including these problematic polar compounds, was achieved on a phenyl-hexyl column, by binary gradient elution with water/acetonitrile using ammonium formate and formic acid as additives. The anticoccidial residues were extracted from raw, unfiltered, water samples (250 mL) using polymeric divinylbenzene solid phase extraction (SPE) cartridges, with subsequent elution (methanol:acetonitrile:ethyl acetate, 40:40:20, v/v) and concentration prior to determination. The method recovery (at a concentration representative of realistic expected environmental water concentrations based on literature review) ranged from 81–105%. The method was successfully validated for 26 anticoccidials, at four concentration levels, in accordance to Commission Decision 2002/657/EC and SANTE/11813/2017 guidelines. Trueness and precision, under within-laboratory reproducibility conditions, ranged from 88–111% and 0.9–10.3% respectively.

    更新日期:2020-01-11
  • High-Resolution Capillary Electrophoresis Separation of Large RNA Under Non-Aqueous Conditions
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-10
    Tian Lu; Lee Klein; Sha Ha; Richard R. Rustandi

    Large RNAs including messenger RNAs (mRNAs) are promising candidates for development of new drug products and vaccines. Development of high resolution methods for direct analysis of large RNAs, especially for purity in general and size or length in particular, is critical to support new drug development and manufacture. However, resolution based on size or length for large RNAs is limited even by capillary electrophoresis (CE), which is one of the most efficient separation methods for nucleic acids in general. This paper presents a capillary gel electrophoresis (CGE) method for separating large RNA molecules by size or length under strongly denaturing, non-aqueous conditions. We believe that our work constitutes the first time that a gel suitable for CGE prepared with high molecular weight polymers and using only formamide as solvent has been successfully employed to analyze large RNAs on the basis of their size or length with high resolution. With an eye toward application for mRNAs in particular, separation conditions in this work were optimized for RNAs approximately 2000 nucleotides (nt) in length. As compared to a standard CGE method using an aqueous gel, resolution for commercially-available RNA ladder components at 1500 and 2000 nt is increased approximately 6-fold. The impacts of polymer type, molecular weight of the polymer, and polymer concentration on the separation were studied and optimized. Analysis of the results presented here also provides guidance for optimization of separation conditions for RNAs with different sizes as needed for particular applications in the future.

    更新日期:2020-01-11
  • Quantification of prostaglandins in rat uterus by Ultra High-Performance Liquid Chromatography/Mass Spectrometry based on derivatization with analogous reagents
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-10
    Ke Ye; QiXin Jiang; Yawen Lu; Xiaodong Wen; Jie Yang

    Prostaglandins (PGs) are vitally important unsaturated fatty acids involved in arachidonic acid (AA) metabolism, participating in numerous pathophysiological processes, especially in maintaining the homeostasis of uterus. Therefore, quantitative analysis of PGs is of great importance for uncovering potential mechanisms of PGs related diseases. However, methods for determining PGs in uterine samples have not been reported. In this study, an ultra high-performance liquid chromatography/mass spectrometry (UHPLC-MS/MS) method was established to quantify PGs in uterine samples, using N,N-Dimethylethylenediamine (DMED) and N,N-Diethylethylenediamine (DEED) as derivatization reagents. The derivatization could be finished at 37 °C for 30 min catalyzed by 1-N,N,N',N'-Tetramethyl-O-(7-azabenzotriazol-1-yl) uronium hexafluorophosphate (HATU). This is a mild condition suitable for most of biological samples. The DMED labeling of PGs could significantly enhance their response compared to those of underived ones. This method exhibited excellent linearity (R2>0.997) and precision for the determination of PGs in uterine samples (CV≤12.9 %). The recoveries of PGs were ranged from 83.0-100 % and matrix effects were ranged from 86.3-106 %, indicating DEED labeled standards could be used as internal standards for PGs quantification. With the proposed method, we successfully quantified PGs in rat uterus. The results showed their levels were significant changed in abnormal uterine bleeding (AUB) rats, suggesting that PGs might be involved in the pathological process of AUB. This established analogous reagents derivatization based UHPLC-MS/MS method could be used as a powerful tool to monitor PGs, providing insights to the precise mechanism of PG action on the endometrium.

    更新日期:2020-01-11
  • Characterization of E 472 food emulsifiers by high-performance thin-layer chromatography with fluorescence detection and mass spectrometry
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-10
    Claudia Oellig; Katharina Link; Wolfgang Schwack

    Esters of fruit acids including acetic acid and mono- and diacylglycerols (MAG and DAG), also known as E 472 emulsifiers, are used in the food industry as food additives to adjust techno-functional properties like viscosity, emulsion stability and foaming stability in various products, mainly dairy products. Based on the respective fruit acids, E 472 emulsifiers are classified in several categories with acetic acid esters (ACETEM, E 472a), lactic acid esters (LACTEM, E 472b), citric acid esters (CITREM, E 472c), and mono- and diacetyl tartaric acid esters (DATEM, E 472e) as the most prominent representatives. Besides fruit acid esters, E 472 emulsifiers mainly comprise MAG, DAG, triacylglycerols (TAG), free fatty acids (FFA), free fruit acids and free glycerol in different amounts. Here we present an innovative and sensitive method for the characterization of the composition of E 472 emulsifiers by high-performance thin-layer chromatography with fluorescence detection (HPTLC–FLD). For HPTLC–FLD, technical emulsifiers were simply dissolved and analyzed on HPTLC silica gel plates after a two-fold development and derivatization with primuline, enabling the easy characterization and direct visual comparison of the emulsifier pattern (fingerprint) through the fluorescent lipid components under UV 366 nm. Thus, the HPTLC–FLD fingerprint approach represents a simple tool for the comparison of different samples, batches and categories of E 472. Coupling of HPTLC to mass spectrometry moreover enabled the identification of constituents of interest.

    更新日期:2020-01-11
  • Photochemical synthesis of magnetic covalent organic framework/carbon nanotube composite and its enrichment of heterocyclic aromatic amines in food samples
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-10
    Ruiyu Liang; Yuling Hu; Gongke Li

    The layered cladding sea cucumber-like covalent organic framework incorporated magnetic carbon nanotube ([email protected]) was prepared by photochemical synthesis. The magnetic composite was fabricated by filling magnetic nanoparticles inside carbon nanotubes and depositing covalent organic framework shell on the outside. The composites exhibited large specific surface area, high stability and adsorption capacity for heterocyclic aromatic amines. Therefore, [email protected] was applied as adsorbent for magnetic solid phase extraction to enrich the heterocyclic aromatic amines from complex food samples prior to the determination by ultra-high performance liquid chromatography-tandem mass spectrometry. The adsorption mechanism between [email protected] and heterocyclic aromatic amines was discussed and verified by Gaussian simulation. The effect of adsorbent amount, extraction conditions and desorption conditions on the efficiency of pretreatment were optimized. The established method revealed wide linear range and high sensitivity with the LODs ranging from 0.0058 to 0.025 ng/g. Furthermore, the developed method was successfully applied to determine heterocyclic aromatic amines in fried chicken and roast beef. Satisfactory recoveries were obtained, which demonstrated the promising potential of [email protected] as good adsorbent for pretreatment of trace analytes.

    更新日期:2020-01-11
  • Alternative Method to Study the Radial Dispersion in Liquid Chromatography Columns. Part I: Theory
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-10
    Yoachim Vanderheyden; Ken Broeckhoven; Gert Desmet

    We report on an alternative experimental method to determine the transversal or radial dispersion coefficient (Drad) in packed bed columns for liquid chromatography. The method uses a recently developed type of column end-fitting with an impermeable segmentation ring that splits the incoming flow in a central and peripheral part. Using this device and continuously sending a tracer-laden flow through the central inlet and a tracer-less flow through the peripheral inlet, a steady-state radial dispersion pattern is established which can be used to determine the degree of radial dispersion. The present part of the study lays the theoretical foundation for the method and shows the parameter sensitivity of the different possible data analysis variants. In addition, computational fluid dynamics simulations have been used to validate the established procedure (agreement between true and determined Drad-value better than 0.4%) as well as to study the effect of the most important error sources: the presence of the annular flow segmentation ring and the almost inevitable occurrence of mismatches between the central and the peripheral in- and outlet flows. In the latter case, a combined read-out method can be proposed that nearly perfectly compensates for the flow mismatch error (remaining error on the Drad-value smaller than 3%).

    更新日期:2020-01-11
  • Chromatographic Behavior of Bivalent Bispecific Antibodies on Hydrophobic Interaction Chromatography Columns
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-10
    Lucas K. Kimerer; Timothy M. Pabst; Alan K. Hunter; Giorgio Carta

    The elution behavior of bivalent bispecific antibodies (BiSAb) comprising an immunoglobulin G framework genetically fused to a pair of single chain variable fragments (scFvs) was studied on hydrophobic interaction chromatography (HIC) columns using ammonium sulfate gradients. Each of the BiSAb molecules studied exhibited a three-peak elution behavior regardless of the location of scFv attachment to the framework IgG. Collecting and re-injecting each of the isolated peaks and eluting with the same gradient resulted in the same three-peak profile indicating that the behavior is reversible. Analogous behavior was observed for HIC resins with different functional ligands, matrix structures, and particle sizes. Residence time, operating temperature, and hold time were shown, to affect the elution behavior. While three peaks were obtained at short residence times and room temperature, residence times longer than about 27 min or at 45°C resulted in a single merged peak indicating that the underlying mechanism occurs on time scales comparable to that of chromatographic separation. Holding the protein on the resins prior to elution enriched the late eluting peak indicating that multiple binding states formed on the chromatographic surface are responsible for this behavior. Tryptophan auto-fluorescence measurements show that stronger binding forms have increased solvent exposure indicating that surface-catalyzed conformational changes play a role. A model was developed to describe the interplay of chromatographic separation and slow conformational changes.

    更新日期:2020-01-11
  • Influence of the Pre-elution of Solute in Initial Mobile Phase on Retention Time and Peak Compression under Linear Gradient Elution
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-09
    Weiqiang Hao; Kai Wang; Bangyi Yue; Qiang Chen; Yibo Huang; Jianjun Yu; Dashuai Li

    Under gradient elution the solute will firstly migrate in initial mobile phase due to dwelling time (tD) of the system. The pre-elution of solute in initial mobile phase can be accounted for by a dimensionless value of tD/(t0kφ0), where t0 and kφ0 denote dead time and retention factor in initial mobile phase, respectively. The influence of tD/(t0kφ0) on retention time (tR) and peak compression factor (G) are discussed under linear gradient elution. A general expression for G is proposed, and two analytical forms of it which are suited for linear solvent strength model (LSSM) and quadratic solvent strength model (QSSM) respectively are presented. The well-known Poppe equation for G which is derived under LSSM is extended by taking tD/(t0kφ0) into account. The expression for G under QSSM takes into account the curvature in the plot of logarithmic retention factor vs. mobile phase composition. By taking twelve compounds degraded from lignin as analytes, the experimental and predicted chromatograms are found to be well consistent. It is shown that tD/(t0kφ0) has more effects on the prediction of tR than that of G.

    更新日期:2020-01-11
  • In situ neutron scattering of antibody adsorption during protein A chromatography
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-09
    Maria Papachristodoulou; James Doutch; Hoi Sang Beatrice Leung; Andy Church; Thomas Charleston; Luke A. Clifton; Paul D. Butler; Christopher J. Roberts; Daniel G. Bracewell

    A deeper understanding of the nanoscale and mesoscale structure of chromatographic adsorbents and the distribution of proteins within the media, is critical to a mechanistic understanding of separation processes using these materials. Characterisation of the media's architecture at this scale and protein adsorption within, is challenging using conventional techniques. In this study, we propose a novel resin characterisation technique that enables in-situ measurement of the structure of the adsorbed protein layer within the resin, under typical chromatographic conditions. A quartz flow-through cell was designed and fabricated for use with Small Angle Neutron Scattering (SANS), in order to measure the nanoscale to mesoscale structures of a silica based protein A chromatography resin during the monoclonal antibody sorption process. We were able to examine the pore-to-pore (˜133 nm) and pore size (˜63 nm) correlations of the resin and the in-plane adsorbed antibody molecules (˜ 4.2 nm) correlation at different protein loadings and washing buffers, in real time using a contrast matching approach. When 0.03 M sodium phosphate with 1 M urea and 10 % isopropanol buffer, pH 8, was introduced into the system as a wash buffer, it disrupted the system's order by causing partial unfolding of the adsorbed antibody, as evidenced by a loss of the in-plane protein correlation. This method offers new ways to investigate the nanoscale structure and ligand immobilisation within chromatography resins; and perhaps most importantly understand the in-situ behaviour of adsorbed proteins within the media under different mobile phase conditions within a sample environment replicating that of a chromatography column.

    更新日期:2020-01-11
  • Template-directed fabrication of zeolitic imidazolate framework-67-derived coating materials on nickel/titanium alloy fiber substrate for selective solid-phase microextraction
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-09
    Junliang Du; Rong Zhang; Feifei Wang; Xuemei Wang; Xinzhen Du

    Novel solid-phase microextraction fibers were fabricated by electrochemical deposition of cobalt on the pretreated nickel/titanium alloy (NiTi) fiber substrate and subsequent in situ growth of zeolitic imidazolate framework-67 (ZIF-67) followed by annealing treatment. The [email protected] coating was used as a precursor and template for controlled fabrication of the [email protected] coatings including [email protected]3O4 and carbonaceous composite coatings. . The extraction performance of the [email protected] coatings was evaluated using typical aromatic compounds coupled to high-performance liquid chromatography with UV detection. The results clearly demonstrate that the extraction selectivity is subject to the surface elemental composition of the ZIF-67-derived coatings. In view of long-term stability and good extraction selectivity, the [email protected] coating was selected for the enrichment and determination of polycyclic aromatic hydrocarbons (PAHs). Under the optimized conditions, the calibration curves were linear in the range of 0.05-100 μg•L−1 with the correlation coefficients above 0.998. Limits of detection were 0.005-0.042 μg•L−1. Furthermore, the intra-day and inter-day repeatability of the proposed method with the single fiber varied from 2.3% to 5.8% and from 3.3% to 6.9%, respectively. The fiber-to-fiber reproducibility ranged from 4.1% to 8.5%. The proposed method was suitable for selective enrichment and determination of target PAHs from real water samples. Moreover, the fabricated fiber showed precisely controllable growth and 150 extraction and desorption cycles.

    更新日期:2020-01-11
  • Comprehensive Characterisation of Ylang-Ylang Essential Oils According to Distillation Time, Origin, and Chemical Composition Using a Multivariate Approach Applied to Average Mass Spectra and Segmented Average Mass Spectral Data
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-09
    Leo Lebanov; Shiladitya Chatterjee; Laura Tedone; Sean C. Chapman; Matthew R. Linford; Brett Paull

    Analysis of the complex essential oil samples using gas chromatography hyphenated with mass spectrometry (GC-MS) generate large three-way data arrays. Processing such large data sets and extracting meaningful information in the metabolic studies of natural products, requires application of multivariate statistical techniques (MSTs). From the GC-MS raw data several different input data sets for the MSTs can be created, total chromatogram average mass spectrum (TCAMS), segmented average mass spectrum (SAMS) and chemical composition. Herein, we compared the performance of MSTs on average mass spectrum based data sets, TCAMS and SAMS, against chemical composition and attenuated total reflectance - Fourier transformation infrared (ATR-FTIR) spectroscopy in the evaluation of quality of ylang-ylang essential oils, based on their grade, geographical origin and chemical composition, using principal component analysis (PCA), partial least squares regression (PLS) and discriminatory analysis (PLS-DA). PCA based on TCAMS, SAMS and chemical composition showed clear trends amongst the samples based on increase in grade (distillation time). PLS-DA applied to TCAMS, SAMS and ATR-FTIR discriminated between all geographical origins. Predicted relative abundances of 18 most important compounds, using PLS regression models on TCAMS, SAMS and ATR-FTIR, were successfully applied to ylang-ylang essential oil quality assessment based on comparison with the ISO 3063:2004 standard, where SAMS data set showed superior performance, compared to other data sets.

    更新日期:2020-01-09
  • Retention of polypropylene stereoisomers in solvent gradient interaction chromatography on porous graphitic carbon as influenced by temperature and mobile phase composition
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-09
    Anthony Ndiripo; Harald Pasch

    The behavior of isotactic, syndiotactic and atactic polypropylene stereoisomers on porous graphitic carbon (PGC) at different column temperatures is investigated with 1-decanol, decalin and decane as the adsorption promoting solvents using gradient interaction chromatography (SGIC). Column temperatures between 120 – 180°C are investigated for the three adsorption promoting solvents with 1,2,4-trichlorobenzene (TCB) as the desorption promoting solvent. Owing to the different stereochemistry of the isomers, their interaction with the atomic level flat surface (ALFS) of porous graphitic carbon is observed to be different when injected from the three different adsorption promoting solvents. Atactic and isotactic polypropylene are not separable when 1-decanol is used as the adsorption solvent but can be separated from syndiotactic PP at column temperatures of between 120 – 180°C. The three stereoisomers have almost similar elution volumes when decalin is used as the adsorption promoting solvent between 120 – 170°C. Decane allows for both adsorption and desorption of the stereoisomers at distinct peak elution volumes at the studied column temperatures of 120 – 160°C. Furthermore, it is shown that increasing the column temperature while maintaining other chromatographic conditions can either decrease or increase retention depending on the adsorption promoting solvent. More importantly, retention is influenced by adsorption conditions (temperature and adsorption promoting solvent) which may affect macromolecular conformations upon injection onto the PGC stationary phase. This is the first study on PP stereoisomers highlighting this behaviour.

    更新日期:2020-01-09
  • Scale up of a chromatographic capture step for a clarified bacterial homogenate – influence of mass transport limitation and competitive adsorption of impurities
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-08
    Michał Kołodziej; Dominik Georg Sauer; Jürgen Beck; Wojciech Kazimierz Marek; Rainer Hahn; Alois Jungbauer; Astrid Dürauer; Wojciech Piątkowski; Dorota Antos

    A model-based approach for scaling up chromatographic capture step was developed. The purification of human basic fibroblast growth factor protein 2 (FGF2) from an E.coli homogenate on a cation exchange resin was selected as a case study. Non-ideal effects accompanying the capture operation were examined, including: reduction in the protein diffusivity in the presence of the homogenate, competitive adsorption between FGF2 and undefined impurities, and flow behavior in external column volumes. The viscosity of the homogenate was measured as a function of dilution degree and shear stress, and its contribution to the diffusivity reduction was quantified. A dynamic model was formulated which accounted for underlying kinetic and thermodynamic dependencies. The model parameters were determined for a lab scale system using a small 2-mL column. The model was successfully used to scale up the capture operation from the lab scale column to a preparative bench scale column of about 1 L volume.

    更新日期:2020-01-08
  • Biocompatible solid-phase microextraction coupled to liquid chromatography triple quadrupole mass spectrometry analysis for the determination of phthalates in marine invertebrate
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-07
    Francesco Saliu; Simone Montanto; Marina Lasagni; Paolo Galli

    This paper describes the development and validation of a new procedure for the determination of phthalates in marine invertebrates, based on biocompatible solid-phase microextraction (BioSPME) followed by liquid chromatography coupled to mass spectrometry. The importance of this application relies on the current use of marine organisms as bioindicators for microplastic contamination through the detection of phthalates in their tissues. Challenges originate from the availability and/or possible restriction on the use of the biological materials, the need for user- friendly procedures for simplifying and speeding up operations in the marine environments, and the ubiquitous presence of phthalates in the laboratory environments that may cause background contamination. BioSPME served as an effective solution to all these issues, owing to the extreme minimization of the sample manipulation. Sampling operations were limited to the direct transfer of small amounts of the biological materials (150 mg) inside glass vials capped with aluminium lids; extractions were carried out by ultrasonication in acetone followed by dilution in ultrapure water and BioSPME clean-up; Electrospray (ESI) LC-MS/MS was employed for the final analytical determinations on the purified extracts. Tests were carried out on samples belonging to three different phyla, namely Cnidaria, Porifera, and Mollusca obtained from Maldivian coral reef environments and used for a current microplastic contamination biomonitoring project. Overall, very good sensitivity and repeatability, with negligible back contamination of the blanks were observed. The limits of detections were between 0.2 and 2.1 ng/g and precision, calculated as relative standard deviation (RSD), was below 14% for all the tested phthalates.

    更新日期:2020-01-07
  • A sensitive two-step stacking by coupling field-enhanced sample injection and micelle to cyclodextrin stacking for the determination of neutral analytes
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-07
    Caijing Liu; Jing Li; Lidan Zhu; Linmin Lian; Luyi Jiang; Hanbing Li; Jizhong Yan; Chu Chu

    To promote the detection sensitivity of neutral analytes, a sensitive two-step stacking strategy by coupling field-enhanced sample injection and micelle to cyclodextrin stacking in reverse migrating micelles MEKC has been established by selecting jujuboside A and B as models. The stacking mechanism, affecting factors as well as analytical performances of the proposed method were investigated. Compared with typical injection, the sensitivity enhancement factors of this method were up to 140- and 152-fold for jujuboside A and B, respectively. The enhancements were 8-10 times better than only single stacking strategy by MCDS. The LODs were 0.2-0.3 μg mL−1, interday and intraday %RSD were both lower than 4.3%, and a good linearity (r>0.999) was obtained. Feasibility in real samples analysis was evaluated by using Semen Ziziphi Spinosae dispensing granule and rat's urine. The results suggested that the strategy was simple, reliable, sensitive and promising for the analysis of neutral analytes in complex sample matrix.

    更新日期:2020-01-07
  • Aging-related lipidomic changes in mouse serum, kidney, and heart by nanoflow ultrahigh-performance liquid chromatography-tandem mass spectrometry
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-03
    Jung Yong Eum; Jong Cheol Lee; Sun Shin Yi; Il Yong Kim; Je Kyung Seong; Myeong Hee Moon

    Aging refers to the intracellular accumulation of reactive oxygen species that damages proteins, DNA, and lipids. As alterations in lipid metabolism may trigger metabolic disorders and the onset of metabolic diseases, changes in lipid profiles can be closely related to aging. In this study, a comprehensive lipidomic comparison between 4- and 25-month-old mice was performed to investigate age-induced changes in the lipid profiles of mouse serum, kidney, and heart using nanoflow ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. Quantitative analysis of 279 of the 542 identified lipids revealed significant changes upon aging, mainly showing decreased levels in the three types of samples. Exceptionally, most triacylglycerols showed significant increases in heart tissue. The kidney was influenced more by aging than the serum and heart. The highly abundant lipids in each lipid class with significant decreases (> 2-fold, p < 0.01) were lysophosphatidic acid 18:1, lysophosphatidylinositol 20:4, and ceramide d:18:1/24:0 in serum; lysophosphatidylglycerol 16:0 in heart tissue; and eight phosphatidylethanolamines (20:4, 22:6, 36:2, 36:3, 38:4, 38:5, 38:6, 40:6, and 40:7), two cardiolipins (72:7 and 72:8), and lysophosphatidylcholine 18:0 in kidney tissue. The findings indicate the potential of lipidomic analysis to study characteristic age-related lipid changes.

    更新日期:2020-01-04
  • Highly selective monitoring of in-source fragmentation sapogenin product ions in positive mode enabling group-target ginsenosides profiling and simultaneous identification of seven Panax herbal medicines
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-03
    Chun-xia Zhang; Xiao-yan Wang; Zhao-zhou Lin; Hong-da Wang; Yue-xin Qian; Wei-wei Li; Wen-zhi Yang; De-an Guo

    In-source fragmentation of ginsenosides in the positive ESI mode (pISF-G) frequently occurs, which results in little fragment information useful for the structural elucidation. We are aimed to unveil the genesic mechanism and explore its potential significance in quality control of Ginseng and the related compound formulae. By applying six high-resolution mass spectrometers from Agilent, Waters, and Thermo Fisher, we could primarily demonstrate the susceptibility of pISF-G. The ion clusters in the positive full-scan MS1 spectra were generated from the protonated sapogenins by successive elimination of H2O, and showed specificity for ginsenoside classification. Selective ion monitoring (SIM) of the sapogenin product ions could delineate group-target ginsenoside profiles from Ginseng. A high-selectivity characteristic chromatogram (CC) was elaborated for Ginseng, on the VionTM IMS-QTOF mass spectrometer by IM (ion mobility) separation and quadrupole filtering of four sapogenin fragments (m/z 407.37/CCS 206.24 Å2; m/z 423.36/CCS 211.26 Å2; m/z 439.36/CCS 209.60 Å2; m/z 457.37/CCS 217.81 Å2). Chemometric analysis, based on the CC data of seven Ginseng drugs (P. ginseng, P. quinquefolius, P. notoginseng, Red ginseng, leaf of P. ginseng, P. japonicus, and P. japonicus var. major), disclosed 35 marker compounds. We could readily discriminate among P. ginseng, P. quinquefolius, and P. notoginseng, in 15 different compound formulae by identifying these marker compounds on both the Vion IMS-QTOF and QTrap 4500 mass spectrometers. Conclusively, SIM of the pISF-G sapogenin product ions renders a new concept of CC enabling the group-target profiling of ginsenosides and authentication of Ginseng and the related compound formulae.

    更新日期:2020-01-04
  • The effect of pH on antibody retention in multimodal cation exchange chromatographic systems
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-03
    Julie Robinson; David Roush; Steven M. Cramer

    The present paper builds upon previous work on mAb domain contributions to multimodal (MM) chromatography by examining how pH can impact mAb surface properties and retention in these systems. Linear salt gradient experiments were carried out between pH 5-7 for several mAbs with different pI and surface hydrophobicities in four different MM CEX resins at two ligand densities. mAb retention showed an inverse, non-linear correlation with pH. Changing pH affected the elution order, creating unique windows of selectivity in each of the MM CEX resins. One mAb showed a pH-dependent spectrum of domain contributions, demonstrating that pH can be used to tune the relative importance of the (Fab)2 and Fc domains for some mAbs in MM systems. Positive, negative, and hydrophobic patches were calculated between pH 5-7 for the mAbs. Visualizing these patches on the protein surface demonstrated that each mAb showed a unique distribution of surface charge and hydrophobicity that changed with pH. The sum of patch areas was tracked across this pH range to quantitatively understand how pH impacted these important surface properties. The quantitative analysis then was narrowed to consider only patches in the CDR loops, which were hypothesized to be an important interaction site for some mAbs in these systems. Interestingly, differences in the titration of CDR loop patches for each mAb were shown to be a result of Histidine titrations and patches in this region were qualitatively correlated with experimental trends including the observed elution order reversals. These results indicate that pH potentially can be employed as a lever for the strategic design of multimodal steps to create flow through, bind and elute, or weak partitioning operations with important implications for the design of integrated and/or continuous downstream purification processes. Furthermore, the ability to tune domain contributions in MM separations using pH creates intriguing possibilities for current downstream challenges such as the removal of product-related impurities, as well as the purification of bispecific mAbs.

    更新日期:2020-01-04
  • Evaluation of sulfonic acid functionalized covalent triazine framework as a hydrophilic-lipophilic balance/cation-exchange mixed-mode sorbent for extraction of benzimidazole fungicides in vegetables, fruits and juices
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-02
    Wenjie Zhao; Xiaoyu Wang; Jianhua Guo; Yun Guo; Chen Lan; Fuwei Xie; Shanying Zong; Lijun He; Shusheng Zhang

    The functionalization of covalent organic frameworks (COFs) enhances chemical properties and expands future applications. Herein, a facile strategy for sulfoacid-functionalized COF is presented through post-modification of covalent triazine frameworks (CTFs) platform. The magnetic solid phase extraction (MSPE) material is obtained by anchoring in situ Ni particles on CTF support (Ni/CTF-SO3H) possessing a dual retention mechanism combining hydrophilic-lipophilic-balance (HLB) and cation-exchange interaction. We established the (Ni/CTF-SO3H)-MSPE method for selectively enriching carbendazim (CBZ) and thiabendazole (TBZ) from food samples and reducing matrix effect simultaneously. The method detection limit is 1.23-7.05 µg kg−1 for CBZ and TBZ in vegetable, fruit and juice samples, determined by high-performance liquid chromatography-ultraviolet detector. The recoveries of spiked CBZ and TBZ in the samples are 80.2-115.1% and RSDs 6.0-11.4%, depending on both analytes and samples. Our work provides a unique perspective in the development of functionalized COFs as a versatile HLB/cation-exchange mixed-mode SPE sorbent for extraction of basic analytes in complex matrix.

    更新日期:2020-01-02
  • Separation of Twelve Posaconazole Related Stereoisomers by Multiple Heart-cutting Chiral-chiral Two-Dimensional Liquid Chromatography
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-02
    Feng Xu; Yao Xu; Guizheng Liu; Meng Zhang; Shangshang Qiang; Jingwu Kang

    Posaconazole represents a triazole antifungal agent which is used to treat various fungal infections. It contains four chiral centers leading to 16 stereoisomers. With the convergent synthesis route, only 11 related stereoisomeric impurities may potentially exist in the active pharmaceutical ingredient (API). It is a challenge to separate all the stereoisomers in one run. To address this problem, a multiple heart-cutting chiral-chiral two-dimensional liquid chromatography (2D-LC) method was developed. The multiple heart-cutting 2D-LC separation was implemented on 2D-LC system with three chiral columns with immobilized polysaccharide chiral stationary phases, namely Chiralpak IB, IC and IF3. In the system, the column Chiralpak IB was used as the 1D separation column and IC and IF3 columns were used parallelly for the 2D separation. The twelve stereoisomers were all well separated in one run by the multiple heart-cutting chiral-chiral 2D-LC system.

    更新日期:2020-01-02
  • Potential of topological descriptors to model the retention of polychlorinated biphenyls in different gas chromatography stationary phases, including ionic liquid-based columns
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-02
    J. Escobar-Arnanz; M.L. Sanz; M. Ros; J. Sanz; L. Ramos

    The aim of this study was to develop a statistical model based on a set of intuitive topological descriptors that will help to determine the influence of the polychlorinated biphenyls (PCBs) structural features on the chromatographic behavior of these analytes in a variety of gas chromatographic stationary phases, including the highly polar ionic liquid (IL)-based SLB-IL76 and SLB-IL60 columns. The model was developed using the stepwise multiple linear regression method, and constructed through several levels of increasing complexity to make evident the relative influence of the selected descriptors. The proposed model was easy to implement and provided similar satisfactory results irrespective of the dependent variables used (i.e., retention index or retention time) or the chromatographic conditions applied (i.e., pseudo-isotherm and programmed temperature) for IL-based phases. The model also allowed the correct prediction of the elution order of selected PCBs in these and other less polar phases evaluated (i.e., SW-10, DB-17, ZB-5 and HT-8). To our knowledge, this is the first models based on topological descriptors described in the literature that provided a satisfactory fitting of the PCB behavior in IL-based phases. Our results indicated that the mechanism governing the chromatographic separation of PCBs in these highly polar columns showed significant differences compared with those observed in other less polar stationary phases.

    更新日期:2020-01-02
  • Enantiomeric fraction evaluation of the four stereoisomers of difethialone in biological matrices of rat by two enantioselective liquid chromatography tandem mass spectrometry methods: chiral stationary phase or derivatization
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-02
    Isabelle Fourel; Etienne Benoit; Virginie Lattard

    The need for the control of rodent populations with anticoagulant rodenticides remains actual, and enantioselective analytical methods are mandatory to understand ecotoxicity issues of those chiral pesticides. This study presents two enantioselective methods to achieve the residue levels and differentiated persistence of the four stereoisomers of difethialone (called in this work E1-trans, E2-cis, E3-cis and E4-trans), which is one of the most toxic second generation anticoagulant rodenticide. Their enantiomeric fraction evaluation in biological matrices of rats was determined by two LC-MS/MS methods. The first one (chiral-LC-MS/MS) combined a chiral column employed in reversed-phase mode (with acetonitrile-water mobile phase) to be compatible with mass spectrometry detection. The second one was also a LC-MS/MS method but with a reversed phase column after a derivatization step with (1S)-(−)-camphanic chloride. Extraction process combined Solid-Liquid extraction and sorbent cartridges. The methods were fully validated. The chiral column was chosen as a reference method for our laboratory because it was quicker and cheaper, and enantioresolution and sensitivity were better. This chiral-LC-MS/MS method was used to measure the enantiomeric fraction of the four stereoisomers of difethialone in rodent biological matrices (liver, plasma, blood and feces) of female rats treated with 3.5 mg/kg of difethialone. The results showed that metabolism is not the same for all the stereoisomers: cis-E3-difethialone was the most persistent, and E4-trans-difethialone was the most quickly eliminated. This chiral-LC-MS/MS method will be used to study the pharmacokinetics of the four stereoisomers of difethialone, and for ecotoxicological surveillance to evaluate the specific persistence of each stereoisomer of difethialone in case of secondary exposure of wildlife non-target species.

    更新日期:2020-01-02
  • Quantitation of Amino Sugar Stereoisomer and Muramic Acid Biomarkers by Hydrophilic Interaction Liquid Chromatography-Mass Spectrometry
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-02
    T.C. VandenBoer; R.A.Di Lorenzo; R.F. Hems; K.E.R. Dawe; S.E. Ziegler; C.J. Young

    A rapid separation and quantitation of the stereoisomer amino sugars glucosamine, galactosamine, and mannosamine, along with muramic acid, is needed. These compounds, when their quantities are accurate, can be used to understand the origin and fate of natural organic matter (NOM) in the environment. These target molecules are biomarkers of fungi and bacteria and allow the deconvolution of microbial transformations and degradation of NOM in a wide variety of environmental matrices. Analytical methods applied to this suite of biomarkers are needed to understand carbon and nitrogen biogeochemistry with a changing global climate. Traditional separations of these analytes by gas chromatography require sample derivatization, as does reverse phase liquid chromatography. In contrast, ion chromatography can separate the analytes directly, but requires a separate analytical method to quantify muramic acid. In this work we present a direct analysis of all these molecules using hydrophilic liquid interaction chromatography. Solvent composition, buffer strength, pH, flow rate, and column temperature were optimized. The method can separate these four compounds and the biopolymeric precursor molecule N-acetylglucosamine in a single run in under 8 minutes with equivalent resolution to the best previously reported separations that did not require derivatization prior to analysis. Detection of the analytes was performed by both tandem and time-of-flight mass spectrometry. The method was assessed for its quantitative capabilities through i) peak area assignment, ii) check standards with ratios of the target analytes likely to be present in real samples, iii) an injection internal standard, and iv) quantitative analysis of real soil hydrolysates by external calibration and standard addition approaches. Across their expected analytical ranges the response for each analyte was highly linear with good accuracy (< 25 %) and precision (< 15 %) over three orders of magnitude. Detection limits of 20 µg L−1 were found for galactosamine and 5 µg L−1 for the remainder of the analytes, comparable to the majority of other methods reported in the literature. Overall, this new approach can directly and rapidly quantify amino sugars recovered in environmental hydrolysates.

    更新日期:2020-01-02
  • Versatile modules enable automated multi-column purifications on the ÄKTA pure chromatography system
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-02
    Bastian Franke; Tuomo Frigård; Stephan Grzesiek; Shin Isogai

    Protein purification processes in basic research using ÄKTATM liquid chromatography systems are often limited to single sample injections and simple one-column purifications. Because many target proteins in structural biology require complex purification protocols the work easily becomes laborious. To streamline and accelerate downstream protein production, an ALIASTMautosampler and a modular sample in-line dilution process coupled to ion-exchange chromatography were incorporated into the workflow to automate two of the most commonly performed purification strategies - ion exchange to size exclusion and nickel-ion metal affinity to size exclusion. The chromatographic setup enabled purification of a large array of cytosolic and membrane proteins from small-scale expression cultures produced in insect cells necessary to develop and optimize isotope-labeling strategies for nuclear magnetic resonance spectroscopy applications, resulting in a reduction in experiment time of about 20% per run for both cytosolic and membrane protein purification schemes. However, when queuing multiple samples the throughput increased by 66% and 75%, respectively. In addition, a novel system configuration is presented, where two column valves can be operated independently. This allows for the design of purification loops to increase purity of the target protein.

    更新日期:2020-01-02
  • Wayne State University Experimental Descriptor Database for Use with the Solvation Parameter Model
    J. Chromatogr. A (IF 3.858) Pub Date : 2020-01-01
    Colin F. Poole

    The solvation parameter model is a well established quantitative structure-property relationship model suitable for describing the contribution of intermolecular interactions in a wide range of separation, chemical, biological and environmental processes. The model employs six descriptors for neutral compounds to describe their capability to interact with their environment of which only one, McGowan's characteristic volume (V) is available by calculation for compounds with a known structure. The other five descriptors are derived from experimental data, the refractive index at 20 °C for the excess molar refraction (E), at least for liquids, and the dipolarity/polarizability (S), hydrogen-bond acidity or basicity (A and B) and gas-liquid partition constant on n-hexadecane at 25 °C (L) typically from chromatographic measurements using gas, liquid or micellar electrokinetic chromatography, liquid-liquid partition, or solubility. In this article a descriptor database is assembled utilizing gas and reversed-phase liquid chromatography retention factors and liquid-liquid partition constants determined in a single laboratory to facilitate control over the experimental techniques employed together with a general set of selection tools to identify systems likely to result in unreliable experimental values for specific compounds. The assembled descriptors for a wide range of varied compounds are expected to be more robust for characterizing separation systems than those currently in use.

    更新日期:2020-01-02
  • Carbon nanotube sponges as an enrichment material for aromatic volatile organic compounds
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-31
    Yeonhee Jang; Juyeon Bang; Yeong-Sik Seon; Dong-Wook You; Jun-Sik Oh; Kwang-Woo Jung

    Sensitive methods are required for in situ monitoring of volatile organic compounds (VOCs). Herein, carbon nanotube (CNT) sponges were investigated as a new type of adsorbent for enriching trace aromatic VOCs. A square pillar configuration (3 mm × 3 mm × 45 mm, 5 mg) of a CNT sponge was enclosed in a glass tube (4 mm i.d.). After accumulating the sample vapor, a direct current pulse (26 V, 0.5–3.0 s) through the CNT sponge allowed narrow desorption bandwidths of 0.48−0.84 s (with a photoionization detector) and 1.2 s (with a flame ionization detector) and high desorption efficiency (>96.5%). Gas chromatographic analysis of a nine-component VOC mixture (100 mL adsorption volume) gave enrichment factors of 88 (benzene) to 323 (toluene and m-xylene) with detection limits in the range of 0.9−2.6 ppb (v/v). These results demonstrate that CNT sponges are a promising preconcentrator material for trace detection of VOCs. The adsorption breakthrough experiments exhibited good correlation with the kinetic adsorption and Langmuir isotherm models. The maximum adsorption capacities of the CNT sponge increased in the order benzene (0.13 mg/g) < toluene (2.45 mg/g) < ethylbenzene (13.90 mg/g) < o-xylene (14.31 mg/g), with R2 values of >0.95. The rollup phenomena observed during multicomponent adsorption were explained by the competitive displacement or adsorption affinities of aromatic VOCs. The feasibility of the CNT sponge preconcentrator in a real environment was tested for interfering species (NO2 and NH3), laboratory air, and a human breath sample and demonstrated similar performance as in the controlled nine-component tests.

    更新日期:2020-01-01
  • Determination of the lanthanides, uranium and plutonium by means of on-line high-pressure ion chromatography coupled with sector field inductively coupled plasma-mass spectrometry to characterize nuclear samples
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-31
    Nancy Nazem Wanna; Karen Van Hoecke; Andrew Dobney; Mirela Vasile; Thomas Cardinaels; Frank Vanhaecke

    High-pressure ion chromatography (HPIC) was coupled with sector field inductively coupled plasma-mass spectrometry (SF-ICP-MS) to separate plutonium (Pu), uranium (U), neodymium (Nd) and gadolinium (Gd) nuclides from isobaric nuclides and to quantify them with high sensitivity. In this study, mixed bed ion exchange columns CG5A and CS5A were used, from which Pu and U were eluted first using 1 M nitric acid. The lanthanides were then separated using a gradient of 0.1 - 0.15 M oxalic acid with the pH adjusted to 4.5. The HPIC-SF-ICP-MS method was validated using different sample matrices, i.e. spent nuclear fuel and soil. The method was found to be repeatable and gave rise to transient signals suitable for quantification of nuclide-specific concentrations using external calibration. In terms of accuracy, the HPIC-SF-ICP-MS measurement results were in good agreement with those obtained using thermal ionization mass spectrometry (TIMS). Finally, the method provides an improvement in sample throughput (≤ 60 minutes per sample) and reduces exposure of the operator to radiation compared to off-line gravitational chromatography followed by TIMS.

    更新日期:2019-12-31
  • The relationship between polymer structures on silica particles and the separation characteristics of the corresponding columns for hydrophilic interaction chromatography
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-31
    Ashin Taniguchi; Saki Tamura; Tohru Ikegami

    Silica particles with various pore sizes were modified with poly(acrylamide) via surface-initiated atom-transfer radical polymerization (SI-ATRP) under different reaction conditions. Twenty different columns were prepared and characterized according to a test method for hydrophilic interaction liquid chromatography (HILIC) columns. Hydrophilic retention by the SI-ATRP columns was much higher than that of poly(acrylamide) columns prepared via free-radical polymerization and many commercially available HILIC columns. The SI-ATRP columns displayed greater selectivity for –OH groups than any of the HILIC columns based on their α(U/2dU) values. SI-ATRP functionalization was used to increase the polymer chain density on the silica particles, which suggested a brush-type morphology, and improved hydrophilic selectivity. This indicated that hydrophilic retention and selectivity could be controlled by adjusting the morphology of the organic stationary phase. This stationary phase design strategy was validated experimentally by the effective separation of highly hydrophilic analytes. The findings of this study will greatly contribute to the creation of better separation media.

    更新日期:2019-12-31
  • Stereoselective separation of isomeric sertraline with analytical countercurrent chromatography
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-30
    Wenyu Sun; Yang Jin; Chaoyue Wang; Shanshan Zhao; Xiang Wang; Meng Luo; Jizhong Yan; Shengqiang Tong

    Sertraline is an antidepressant in a group of drugs called selective serotonin reuptake inhibitors. Four stereoisomeric compounds would be produced in its synthetic preparation due to two chiral carbons on its chemical structures. In the present work, stereoselective liquid-liquid extraction of isomeric sertraline with substituted cyclodextrins as stereoselective extractant was investigated. Factors affecting the distribution performance, including organic solvents, types of extractants, pH value, buffer solution of aqueous phase, concentration of extractant and temperature, were investigated. Under optimized conditions, a stereoselectivity of 1.404 was obtained for cis-sertraline and a stereoselectivity of 2.373 was obtained for trans-sertraline when hydroxypropyl-β-cyclodextrin was used as the stereoselective extractant, and a stereoselectivity of 1.685 was achieved for trans-sertraline with methyl-β-cyclodextrin as extractant. An unusual stereoselective combination was observed for trans-sertraline and cis-sertraline when sodium carbonate buffer was used. Successful stereoselective separation of trans-sertraline and cis-sertraline, (1S, 4R) and (1R, 4S)-sertraline by analytical countercurrent chromatography with methyl-β-cyclodextrin as stereoselective selector was achieved, using a biphasic solvent system composed of n-hexane : 0.1 mol L−1 citrate buffer solution with pH7.6 (1:1, v/v).

    更新日期:2019-12-30
  • Establishing repeatability and ruggedness of chiral separations in micellar electrokinetic chromatography mass spectrometry: Combined use of covalently bonded capillary column and molecular micelles
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-30
    Ferdoushi Akter; Shahab A. Shamsi

    Although micellar electrokinetic chromatography-mass spectrometry (MEKC-MS) using bare silica capillary filled with molecular micelles is an advantageous hyphenated technique for chiral analysis, it is still in the developmental stage. This is mainly because of the lower repeatability of retention time and peak area associated with the difficulty in controlling electroosmotic flow on bare silica capillaries. Besides the lower robustness and electrospray erosion of the fused-silica capillary tip, the lifetime is limited for 10-15 runs per capillary column. We have tested a new MEKC-MS method to eradicate this problem using a covalently bonded 2-acrylamido-2-methyl-1-propane-sulfonic acid (AMPS) column filled with free floating molecular micelles, polysodium N-undecenoxy carbonyl-L-leucinate (poly-L-SUCL). Simultaneous enantiomeric separations and MS/MS detection of three β-blockers [atenolol (ATEN), metoprolol (METO) and, pindolol (PINDO)] was achieved within 25 min with improved column lifetime of at least 45-50 runs. Excellent repeatability of retention time was observed for β-blockers, as evidenced by the relative standard deviation of less than 2% and 3 % for intra-capillary and inter-capillary column, respectively. The linear calibration range of both β-blockers was simultaneously established using enantiomers of PINDO as an internal standard. The limit of detection and the lower limit of quantitation were 0.2 μg/mL and 0.5 μg/mL, respectively, for both ATEN and METO. Acceptable recovery of the enantiomeric content of the commercial METO tablet (98-99.5%) and ATEN tablet (89-92.5%) were obtained with adequate system suitability for the precision of peak area (≤10% RSD) under optimum conditions. The developed MEKC-MS approach was extended, which provided broader repeatibility of chiral separation to a panel of primary, secondary and tertiary amines as well as one anionic chiral compound.

    更新日期:2019-12-30
  • A Simple and Rapid Method for the Determination of Lead Dioxide in Minium by Headspace Gas Chromatographic Technique
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-28
    Wei-Qi Xie; Yi-Xian Gong; Shi-Wen Huang; Kong-Xian Yu

    This paper demonstrated a simple and rapid approach for the determination of lead dioxide in minium using a headspace gas chromatographic (GC) technique. This new approach was based on the measurement of carbon dioxide from the redox reaction between lead dioxide and oxalic acid in a sealed headspace vial. The obtained results indicated that the new approach had good measurement accuracy (relative errors ≤ 8.71%) and precision (RSD ≤ 2.86%). Moreover, the limit of quantification (LOQ) and limit of detection (LOD) for this new approach were respectively 0.34 % and 0.10 %, and the recoveries ranged from 97.9 to 101.7%. The new approach is low-cost and reliable, which has potential for use in the analysis of lead dioxide in minium and related products.

    更新日期:2019-12-29
  • Fundamental Distribution Coefficient Data and Separations Using Eichrom Extraction Chromatographic Resins
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-28
    Mathew Snow; Jessica Ward

    Distribution coefficient (Kd) data provides the analyst with a powerful set of tools for designing elemental chemical separations. While considerable Kd data exists in the literature for traditional anion and cation exchange resins, a comprehensive Kd study for the majority of the periodic table has not been published to date for several newer Eichrom extraction chromatographic resins. Kd values for the sorption of 41 different of elements on TEVA, TRU, UTEVA, and Diphonix resin were determined in this work. The power of Kd data in designing chemical separations is then demonstrated through development of separation methods for several challenging chemical separations including U/Mo/Te, Zr/Nb/Mo, and Cd isolation. Separation methodologies are finally applied to soil samples, where the ability for each separation to perform under complex matrix conditions is evaluated.

    更新日期:2019-12-29
  • Determination of sulfonylurea pesticide residues in edible seeds used as nutraceuticals by QuEChERS in combination with ultra-high-performance liquid chromatography-tandem mass spectrometry
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-27
    Maykel Hernández-Mesa; Ana M. García-Campaña

    This work proposes a novel Quick, Easy, Cheap, Effective, Rugged, y Safe (QuEChERS) method in combination with ultra-high performance liquid chromatography-tandem mass spectrometry for the determination of sulfonylurea residues in edible seeds. The chromatographic separation of nine sulfonylureas was accomplished in less than 5.5 min, using a Luna Omega C18 column (50 × 2.1 mm, 1.6 µm). Mobile phase was supplied at 0.55 mL/min and consisted of 0.01% (v/v) aqueous acetic acid as eluent A and a mixture methanol/acetonitrile (80/20, v/v) as eluent B. Column temperature was established at 25°C. A QuEChERS procedure was investigated as sample treatment for sulfonylureas extraction and sample clean-up. Different clean-up agents (i.e. PSA, Z-Sep+, EMR-Lipid and C18) were evaluated, selecting Z-Sep+ (25 mg) as the best option. The proposed method provided an extraction efficiency greater than 86.2%, while absolute matrix effect was lower than 50.1%. Matrix-matched calibration curves were required for analyte quantification. The analytical method was characterized according to SANTE/11813/2017 guideline, and including limits of detection and quantification, precision, and trueness. Linear dynamic ranges were established from 5 to 150 µg/kg for all analytes. Linearity (R2 ≥ 0.9974) and precision in terms of repeatability and intermediate precision (relative standard deviation ≤ 14.7%) are reported. The reporting limit was established at 5 µg kg−1, which is above the limits of quantification of the proposed method (≤ 1.64 µg kg−1) and below the maximum residue levels currently established by European legislation. In general, trueness is within the range of 70-120%. Despite greater recoveries were obtained at the reporting limit (i.e. 120-138%), relative standard deviations lower than 20% were obtained at this concentration level, so fulfilling the requirements of SANTE/11813/2017 guideline. This work represents the first analytical method intended for the analysis of sulfonylureas in sunflower, pumpkin and chia seeds, which are complex matrices due to their high content of fat as well as of growing interest due to their current commercialization as nutraceuticals.

    更新日期:2019-12-27
  • Suspect screening of 200 hazardous substances in plastic toys using ultra-high-performance liquid chromatography-hybrid quadrupole time-of-flight mass spectrometry
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-27
    Xianshuang Meng; Nan Zhang; Xiaojie Sun; Zengyuan Niu; Yulin Deng; Jianqiang Xu; Hua Bai; Qiang Ma

    There is an urgent need for the development of efficient and comprehensive analytical methods for organic chemical compounds due to their increasing number and diversity in children's toy products. The presence of these chemicals in toys poses an extreme risk for the health and development of children. In this study, an analytical methodology has been developed using ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS). This hybrid instrumentation together with an in-house accurate-mass database and a mass spectral library, allows for wide-scope screening and identification of hazardous substances in plastic toys. A total number of 200 compounds belonging to eight chemical families were investigated, such as coloring agents, plasticizers, fragrance allergens, nitrosamines, primary aromatic amines, flame retardants, perfluorinated compounds, and endocrine disruptors. Following a straightforward and efficient dissolution/precipitation method for sample preparation, chemical screening and confirmation were conducted by comparing the experimentally measured exact mass, retention time, and isotopic pattern with the accurate-mass database and by matching the acquired MS/MS spectra against the mass spectral library. The matrix effect, linearity, sensitivity, precision, and recovery of the proposed method were properly evaluated. The obtained limits of detection (LODs) and quantitation (LOQs) were in the range of 0.01–0.98 mg kg−1 and 0.03–2.99 mg kg−1, respectively. The applicability of the developed protocol was verified through the analysis of 55 real plastic toy products.

    更新日期:2019-12-27
  • Two dimensional chromatography mass spectrometry: quantitation of chiral shifts in metabolism of propranolol in bioanalysis
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-26
    Lukas C. Harps; Sonja Schipperges; Felix Bredendiek; Bernhard Wüst; Andreas Borowiak; Maria Kristina Parr

    In this study a heart-cutting 2D-LC method was successfully developed and optimized in order to discriminate and quantitate (S)-propranolol, (R)-propranolol, and its hydroxy metabolites, namely the isomeric (S)-4’-hydroxy propranolol, (R)-4’-hydroxy propranolol, (S)-5’-hydroxy propranolol, (R)-5’-hydroxy propranolol, (S)-7’-hydroxy propranolol, and (R)-7’-hydroxy propranolol in one chromatographic run. Thereby, experiments investigating chiral discrimination in ring hydroxylation of propranolol were made feasible. Analysis of human urine samples after administration of a single oral dose of 40 mg of propranolol clearly revealed considerable chiral shifts in propranolol and its 4-, 5-, and 7-hydroxy metabolites. Furthermore, the excretion rates of the individual (S)- and (R)-enantiomers were continuously monitored over 24 hours post administration. Studies were performed utilizing a 2D-LC system hyphenated to a triple quadrupole mass spectrometer. The chromatographic system was endued with a reversed phase column (phenyl-hexyl) in first dimension and a teicoplanin based chiral column in second dimension. The method was basically validated and successfully evaluated as robust. Calibration was performed achieving accuracy between 80 % and 120 %. Maximal excretion rates of (S)-propranolol, (R)-propranolol, (S)-4’-hydroxy propranolol, (R)-4’-hydroxy propranolol, (S)-5’-hydroxy propranolol, (R)-5’-hydroxy propranolol, and (R)-7’-hydroxy propranolol were 237 ng/min, 281 ng/min, 4 ng/min, 4 ng/min, 1 ng/min, 9 ng/min, and 3 ng/min, respectively.

    更新日期:2019-12-27
  • An effective configuration for automated magnetic micro solid-phase extraction of phenylurea herbicides from water samples followed by high-performance liquid chromatography
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-26
    Mohammad Saraji; Leila Mohammadipour; Narges Mehrafza

    In this study, a new automated magnetic micro solid-phase extraction was introduced. A Tygon tube was folded and fixed around the pole of a cylindrical magnet. Nanosized magnetic sorbents modified with diphenyldichlorosilane were uniformly immobilized on one side of the inner wall of the tube. Sample solution and desorption solvent were passed through the tube using a peristaltic pump. Four phenylurea herbicides (tebuthiuron, monolinuron, isoproturon, and monuron) were used as the model compounds to evaluate the method performance. HPLC-UV was used to separate and quantify the analytes. The effective parameters influencing the performance of the extraction process (i.e., extraction and desorption flow rates, eluent and sample volumes, type of eluent and sample ionic strength) were investigated. The limit of detection was 0.04 μg L−1 for all studied compounds. Calibration curves were linear in the range of 0.1-500 μg L−1 with a determination coefficient between 0.9988 and 0.9999. Intra-day, inter-day and batch-to-batch precisions expressed as relative standard deviation were less than 7%. Several environmental water samples were investigated to assess the applicability of the method for real sample analysis.

    更新日期:2019-12-27
  • Simultaneously quantitative analysis of peptides and chemical components in Cervus and Cucumis polypeptide injection (Songmeile®) using reversed phase liquid chromatography-hydrophilic interaction liquid chromatography–tandem mass spectrometry
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-26
    Wenjing Liu; Yan Cao; Yi Ren; Xia Xu; Liqun He; Ruixue Xia; Pengfei Tu; Yitao Wang; Yuelin Song; Jun Li

    Co-occurrences of peptides and chemical components are usually observed in complicated matrices. Notably, those traditional Chinese medicine prescriptions (TCMPs) contain both plant and animal ingredients. It is still challenging to simultaneously monitor peptides and chemical components attributing to their different liquid chromatographic (LC) and mass spectrometric (MS) behaviors. Herein, efforts were made to pursue an eligible approach enabling simultaneous determination of peptides and chemical components in a TCMP namely Cervus and Cucumis polypeptide injection (CCPI, Songmeile®) that is prepared from the acid hydrolytic peptide-enriched extract of Sika deer (Cervus nippon Temminck) bone and the aqueous extract of muskmelon (Cucumis melo L.) seeds. Reversed phase liquid chromatography and hydrophilic interaction liquid chromatography were serially connected (RPLC-HILIC) to achieve comprehensive retention and separation. Sensitive detection was accomplished with selected reaction monitoring (SRM) mode, and multiply charged and singly charged ion transitions were defined for peptides and chemical components, respectively. Inter-batch variations of CCPI were evaluated in an authentic compound-independent manner. In particular, online energy-resolved MS was proposed to pursue optimal parameters for five targeted peptides after that CCPI peptidome was profiled using nanoLC-LTQ Orbitrap Velos Pro MS. A so-called universal metabolome standard (UMS) sample was built for calibration curve construction and subsequently applied to acquire the quasi-contents of all 31 analytes, including five peptides and 26 chemical components, in ten batches of CCPI (CCPI1–CCPI10). The quantitative dataset revealed mild fluctuation for the quasi-content profiles of analytes-of-interest within different batches. More importantly, RPLC-HILIC–SRM is a promising method to fully address the demands of simultaneous measurement of peptides and chemical components in complicated matrices, and it might be a robust analytical tool for in-depth quality evaluation of CCPI as well as other TCMPs.

    更新日期:2019-12-27
  • Separation optimization in HPLC analysis implemented in R programming language
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-24
    Ch. Zisi; A. Pappa-Louisi; P. Nikitas

    A complete package of functions in the R-language has been written for professional separation optimization of complex mixtures of ionized and/or non-ionized solutes. The package includes functions for (a) base-line correction of experimentally recorded chromatograms, (b) modeling of chromatographic peak shapes and retention data, (c) prediction of the retention time of the test analytes and/or their chromatograms, and (d) separation optimization under either isocratic or single and/or double gradient elution conditions by changing the organic modifier(s) content and/or eluent pH. The optimization functions presented in this study offer two different modes for selection of optimal separation conditions: automatic and manual mode. In the automatic mode, the optimal separation conditions are determined by maximizing the resolution within separation time preset by the analyst. In the manual mode, the optimal separation conditions are selected via scatter or contour plots. The foreknowledge of the precise dependence of resolution and separation time upon one or two retention parameters of interest, provided by the proposed computer-assisted separation optimization method, gives chromatographers a feel of confidence for the selection of the optimal conditions for a desired separation. An illustrative video given in the Supplementary material may encourage a novice practitioner in R (software) programming language to follow the proposed separation optimization procedure in a real HPLC analysis.

    更新日期:2019-12-25
  • Molecularly imprinted polymer thin-film as a micro-extraction adsorbent for selective determination of trace concentrations of polycyclic aromatic sulfur heterocycles in seawater
    J. Chromatogr. A (IF 3.858) Pub Date : 2019-12-24
    Hassan Y. Hijazi; Christina S. Bottaro

    A tailor-made porous molecularly imprinted polymer (MIP) thin-film was prepared by in situ photo-radical polymerization on a glass slide and used as a microextraction adsorbent. Detection was carried out using gas chromatography-mass spectrometry (GC-MS) to afford a method suitable for the selective determination of trace concentrations of polycyclic aromatic sulfur heterocycles (PASHs) in seawater. PASHs are one of the most problematic aromatic organic pollutants, as they are considered more persistent and toxic compared to other analogous aromatic compounds in the environment. The optimized thin-film consisted of a 2-thiophenecarboxaldehyde pseudo-template with 1-vinylimidazole (1-Vim) as the functional monomer, bisphenol A dimethacrylate (BPADMA) as the cross-linker, acetonitrile as the porogen, and polyethylene glycol to boost porosity through formation of interpenetrating polymer networks. The adsorption behaviours of the thin-film, including adsorption kinetics, binding isotherms, and selectivity of MIP thin-film were investigated in detail. The highest imprinting factors (2.3-3.0) and adsorption capacity for targeted PASHs were achieved at a template:monomer:cross-linker ratio of 1:4:8. The method with no sample or film pretreatment showed very good reproducibility for the extraction of PASHs from spiked seawater samples (RSDs ≤ 6.0%, n = 3), was linear (R2>0.9960) over a range of 0.5-40 µg L−1, and gave limits of detection n the range of 0.029-0.166 µg L−1.

    更新日期:2019-12-25
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