Liquid chromatography coupled to tandem mass spectrometry for detecting ten allergens in complex and incurred foodstuffs J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-20 M. Planque, T. Arnould, M. Dieu, P. Delahaut, P. Renard, N. Gillard
Food allergy is a considerable heath problem, as undesirable contaminations by allergens during food production are still widespread and may be dangerous for human health. To protect the population, laboratories need to develop reliable analytical methods in order to detect allergens in various food products. Currently, a large majority of allergen-related food recalls concern bakery products. It is therefore essential to detect allergens in unprocessed and processed foodstuffs. In this study, we developed a method for detecting ten allergens in complex (chocolate, ice cream) and processed (cookie, sauce) foodstuffs, based on ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS). Using a single protocol and considering a signal-to-noise ratio higher than 10 for the most abundant multiple reaction monitoring (MRM) transition, we were able to detect target allergens at 0.5 mg/kg for milk proteins, 2.5 mg/kg for peanut, hazelnut, pistachio, and cashew proteins, 3 mg/kg for egg proteins, and 5 mg/kg for soy, almond, walnut, and pecan proteins. The ability of the method to detect 10 allergens with a single protocol in complex and incurred food products makes it an attractive alternative to the ELISA method for routine laboratories.
Solvent Front Position Extraction procedure with thin-layer chromatography as a mode of multicomponent sample preparation for quantitative analysis by instrumental technique J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-20 A. Klimek-Turek, E. Sikora, T.H. Dzido
A concept of using thin-layer chromatography to multicomponent sample preparation for quantitative determination of solutes followed by instrumental technique is presented. Thin-layer chromatography (TLC) is used to separate chosen substances and their internal standard from other components (matrix) and to form a single spot/zone containing them at the solvent front position. The location of the analytes and internal standard in the solvent front zone allows their easy extraction followed by quantitation by HPLC.
Applications of 2, 2, 2 Trifluoroethanol as a Versatile Co-solvent in Supercritical Fluid Chromatography for Purification of Unstable Boronate Esters, Enhancing Throughput, Reducing Epimerization, and for Additive Free Purifications J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-20 Kathiravan Asokan, Khaja Mohinddin Shaikh, Shahaji Sopan Tele, Siddheshwar Kisan Chauthe, Shabana Ansar, Muthalagu Vetrichelvan, Roshan Nimje, Anuradha Gupta, Arun Kumar Gupta, Ramakanth Sarabu, Dauh-Rurng Wu, Arvind Mathur, Lakshmikant Bajpai
Analysis and purification of boronic acid pinacol esters by RPLC is very challenging due to their degradation in aqueous and alcoholic solvents. These compounds are difficult to purify by SFC too as they are equally sensitive to traditional co-solvents like methanol, ethanol, and 2-propanol. 2,2,2 trifluoroethanol (TFE), which has been reported for the purification of a few alcohol sensitive compounds, was evaluated as a co-solvent in this study for the purification of chiral and achiral boronate esters by SFC. Examples of twelve compounds were presented in this paper where degradation of boronic acid pinacol esters was successfully controlled by replacing methanol with TFE as the co-solvent in SFC. A separate study showed that TFE can also control the epimerization of the enantiomers of 3 substituted 1,4 benzodiazepine analogues during the purification process. In addition to above benefits, 2,2,2trifloroethanol showed improved selectivity and resolution for most of the compounds. With its stronger solvent strength compared to other alcohols, TFE could also be used to reduce the co-solvent percentage needed for elution and to shorten retention time of highly polar samples which did not elute even in 50% of other co-solvents in SFC. A case study of compound B demonstrated that TFE provided a reduced co-solvent percentage and a shorter cycle time with much improved resolution as compared to methanol, thus resulting in higher loading and throughput with reduction of total solvent consumption.
Mechanical characterisation of agarose-based chromatography resins for biopharmaceutical manufacture J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-20 Mauryn C. Nweke, R. Graham McCartney, Daniel G. Bracewell
Mechanical characterisation of agarose-based resins is an important factor in ensuring robust chromatographic performance in the manufacture of biopharmaceuticals. Pressure-flow profiles are most commonly used to characterise these properties. There are a number of drawbacks with this method, including the potential need for several re-packs to achieve the desired packing quality, the impact of wall effects on experimental set up and the quantities of chromatography media and buffers required. To address these issues, we have developed a dynamic mechanical analysis (DMA) technique that characterises the mechanical properties of resins based on the viscoelasticity of a 1 ml sample of slurry. This technique was conducted on seven resins with varying degrees of mechanical robustness and the results were compared to pressure-flow test results on the same resins. Results show a strong correlation between the two techniques. The most mechanically robust resin (Capto Q) had a critical velocity 3.3 times higher than the weakest (Sepharose CL-4B), whilst the DMA technique showed Capto Q to have a slurry deformation rate 8.3 times lower than Sepharose CL-4B. To ascertain whether polymer structure is indicative of mechanical strength, scanning electron microscopy images were also used to study the structural properties of each resin. Results indicate that DMA can be used as a small volume, complementary technique for the mechanical characterisation of chromatography media.
Chemomics-based marker compounds mining and mimetic processing for exploring chemical mechanisms in traditional processing of herbal medicines, a continuous study on Rehmanniae Radix J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-20 Li Zhou, Jin-Di Xu, Shan-Shan Zhou, Hong Shen, Qian Mao, Ming Kong, Ye-Ting Zou, Ya-Yun Xu, Jun Xu, Song-Lin Li
Exploring processing chemistry, in particular the chemical transformation mechanisms involved, is a key step to elucidate the scientific basis in traditional processing of herbal medicines. Previously, taking Rehmanniae Radix (RR) as a case study, the holistic chemome (secondary metabolome and glycome) difference between raw and processed RR was revealed by integrating hyphenated chromatographic techniques-based targeted glycomics and untargeted metabolomics. Nevertheless, the complex chemical transformation mechanisms underpinning the holistic chemome variation in RR processing remain to be extensively clarified. As a continuous study, here a novel strategy by combining chemomics-based marker compounds mining and mimetic processing is proposed for further exploring the chemical mechanisms involved in herbal processing. First, the differential marker compounds between raw and processed herbs were rapidly discovered by untargeted chemomics-based mining approach through multivariate statistical analysis of the chemome data obtained by integrated metabolomics and glycomics analysis. Second, the marker compounds were mimetically processed under the simulated physicochemical conditions as in the herb processing, and the final reaction products were chemically characterized by targeted chemomics-based mining approach. Third, the main chemical transformation mechanisms involved were clarified by linking up the original marker compounds and their mimetic processing products. Using this strategy, a set of differential marker compounds including saccharides, glycosides and furfurals in raw and processed RR was rapidly found, and the major chemical mechanisms involved in RR processing were elucidated as stepwise transformations of saccharides (polysaccharides, oligosaccharides and monosaccharides) and glycosides (iridoid glycosides and phenethylalcohol glycosides) into furfurals (glycosylated/non-glycosylated hydroxymethylfurfurals) by deglycosylation and/or dehydration. The research deliverables indicated that the proposed strategy could advance the understanding of RR processing chemistry, and therefore may be considered a promising approach for delving into the scientific basis in traditional processing of herbal medicines.
A chromatographic study on the exceptional chiral recognition of 2-(benzylsulfinyl)benzamide by an immobilized-type chiral stationary phase based on cellulose tris(3,5-dichlorophenylcarbamate) J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-16 Simone Carradori, Daniela Secci, Cristina Faggi, Roberto Cirilli
In previous studies, Okamoto et al. described the results of the exceptionally large chiral recognition of 2-(benzylsulfinyl)benzamide onto a coated-type chiral stationary phase based on cellulose tris(3,5-dichlorophenylcarbamate). As a continuation and deepening of those studies, here the sulfoxide and a small set of its structural analogues were analyzed on the commercially available Chiralpak IC-3 chiral stationary phase based upon the same polysaccharide derivative as the chiral selector but immobilized onto silica support. The chromatographic results obtained using different mobile phases consisting of pure methanol, ethanol and 2-propanol or binary mixtures n-hexane-2-propanol, which are prohibited with the progenitor coated-type chromatographic support, permitted to identify the NH2 of the amide group as the key structural element of the (S)-enantiomer of 2-(benzylsulfinyl)benzamide for obtaining a very high affinity for the IC-3 chiral stationary phase.
Is vacuum ultraviolet detector a concentration or a mass dependent detector? J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-15 Huian Liu, Guy Raffin, Guillaume Trutt, Jérôme Randon
The vacuum ultraviolet detector (VUV) is a very effective tool for chromatogram deconvolution and peak identification, and can also be used for quantification. To avoid quantitative issues in relation to time drift, such as variation of peak area or peak height, the detector response type has to be well defined. Due to the make-up flow and pressure regulation of make-up, the detector response (height of the peak) and peak area appeared to be dependent on experimental conditions such as inlet pressure and make-up pressure. Even if for some experimental conditions, VUV looks like mass-flow sensitive detector, it has been demonstrated that VUV is a concentration sensitive detector.
Mixed functional monomers-based monolithic adsorbent for the effective extraction of sulfonylurea herbicides in water and soil samples J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-15 Miao Pei, Xiangyu Zhu, Xiaojia Huang
Effective extraction is a key step in the determination of sulfonylurea herbicides (SUHs) in complicated samples. According to the chemical properties of SUHs, a new monolithic adsorbent utilizing acrylamidophenylboronic acid and vinylimidazole as mixed functional monomers was synthesized. The new adsorbent was employed as the extraction phase of multiple monolithic fiber solid-phase microextraction (MMF-SPME) of SUHs, and the extracted SUHs were determined by high-performance liquid chromatography with diode array detection (HPLC-DAD). Results well evidence that the prepared adsorbent could extract SUHs in environmental waters and soil effectively through multiply interactions such as boronate affinity, dipole-dipole and π-π interactions. Under the optimized extraction conditions, the limits of detection for target SUHs in environmental water and soil samples were 0.018–0.17 μg/L and 0.14–1.23 μg/kg, respectively. At the same time, the developed method also displayed some analytical merits including wide linear dynamic ranges, good method reproducibility, satisfactory sensitivity and low consume of organic solvent. Finally, the developed were successfully applied to monitor trace SUHs in environmental water and soil samples. The recoveries at three fortified concentrations were in the range of 70.6–119% with RSD below 11% in all cases. The obtained results well demonstrate the excellent practical applicability of the developed MMF-SPME-HPLC-DAD method for the monitoring of SUHs in water and soil samples.
Extraction of essential oil from Bunium Persicum (Boiss.) by instant controlled pressure drop (DIC) J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-15 Elnaz Feyzi, Mohammad H. Eikani, Fereshteh Golmohammad, Bahram Tafaghodinia
Essential oils extraction from Bunium Persicum (Boiss) was performed using instant controlled pressure drop (in French: Détente Instantanée Contrôlée or DIC) thechnology and optimum extraction conditions were obtained. Response surface methodology (RSM) was used to determine the optimal conditions and the results were 20 s heating time, 3.5 bar pressure, 0.44 mm particle diameter and 9 cycles. Essential oils extraction was also compared with Hydrodistillation (HD), ultrasound-assisted extraction (UAE) and Soxhlet (SOX) extraction. Results show higher efficiency of the DIC than other methods and more oxygenated components were observed. Impact of DIC, HD, UAE and SOX on the morphological structure of the plant was studied by SEM. Antioxidant activity and total phenolic content (TPC) of the extract were determined and comapred by HD. Results show that DIC facilitates achieving to higher TPC and more antioxidant activity.
Synthesis and Chromatographic Characteristics of Iminodisuccinic Acid-functionalized Silica Stationary Phase J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-15 Bin Chen, Ning Zhang, Chen Li, Rong Li, An Fan
In this study, we developed a multifunctional chromatographic medium by using iminodisuccinic acid (IDS) as ligand, γ-glycidoxypropyltrimethoxysilane (γ-GLDP) as spacer arm and silica as matrix. The medium was characterized by fourier transform infrared spectrometry (FT-IR). Binding capacity of IDS on chromatographic medium was determined by potentiometric titration. The effect of mass ratios (w/w) between silica and IDS on the medium synthesis was discussed. The optimal ratio of matrix, spacer arm and ligand was 1.5 g: 2.0 mL: 4.6 g. Based on different chromatographic modes, protein mixtures of bovine serum albumin, ribonuclease and lysozyme were successfully separated with IDS-Silica column and IDS-Cu(II)-Silica column, respectively. To examine metal chelating behavior of IDS-Silica stationary phase, optimal geometries and related parameters of complexes formed by IDS with Fe3+, Cu2+, Ni2+, Zn2+, Co2+ and Ca2+ were achieved by quantum computing. The stabilities of the complexes were predicted according to the results of theoretical calculation. Sorption capacities of IDS-Silica stationary phase for metal ions were determined by using offline frontal chromatography (FC) combined with inductively coupled plasma atomic emission spectrometry (ICP-AES). A good agreement was found between simulating results and experimental observations. The order of chelating strength of IDS-Silica medium for metal ions was Fe3+ > Cu2+ > Ni2+ > Zn2+ > Co2+ > Ca2+. Compared with IDA-Silica, Asp-Silica and Glu-Silica stationary phases, IDS-Silica displayed a stronger chelating property for metal ion.
Ion-pairing reversed-phase chromatography coupled to inductively coupled plasma mass spectrometry as a tool to determine mercurial species in freshwater fish J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-15 Heyong Cheng, Xiaopan Chen, Lihuan Shen, Yuanchao Wang, Zigang Xu, Jinhua Liu
Most of analytical community is focused on reversed phase high performance liquid chromatography (RP-HPLC) for mercury speciation by employing mobile phases comprising of high salts and moderate amounts of organic solvents. This study aims at rapid mercury speciation analysis by ion-pairing RP-HPLC with inductively coupled plasma mass spectrometry (ICP-MS) detection only using low salts for the sake of green analytical chemistry. Two ion-pairing HPLC methods were developed on individual usage of positively and negatively charged ion-pairing reagents (tetrabutylammonium hydroxide –TBAH and sodium dodecylbenzene sulfonate –SDBS), where sodium 3-mercapto-1-propysulfonate (MPS) and l-cysteine (Cys) were respectively added in mobile phases to transform mercury species into negative and positive Hg-complexes for good resolution. Addition of phenylalanine was also utilized for rapid baseline separation in combination of short C18 guard columns. Optimum mobile phases of 2.0 mM SDBS + 2.0 mM Cys + 1.0 mM Phe (pH 3.0) and 4.0 mM TBAH + 2.0 mM MPS + 2.0 mM Phe (pH 6.0) both achieved baseline separation of inorganic mercury (Hg2+), methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg) on two consecutive 12.5-mm C18 columns. The former mobile phase was selected for mercury speciation in freshwater fish because of short separation time (3.0 min). Detection limits of 0.015 for Hg2+, 0.014 for MeHg, 0.028 for EtHg and 0.042 μg L−1 for PhHg were obtained along with satisfactory precisions of peak height and area (1.0-2.8% for 5.0 μg L−1 Hg-mixture standard). Good accordance of determined values of MeHg and total mercury in a certified reference material of fish tissue (GBW 10029) with certified values as well as good recoveries (91–106%) proved good accuracy of the proposed method. An example application to freshwater fish indicated its potential in routine analysis, where MeHg was presented at 3.7–20.3 μg kg−1 as the dominate species.
Determination of orientin in Trollius chinensis using ultrasound-assisted extraction and high performance liquid chromatography: Several often-overlooked sample preparation parameters in an ultrasonic bath J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-15 Mengxia Wei, Lei Yang
The erratic pressure intensities and cavitation exhibited in an ultrasonic bath pose various during practical application. To achieve the most efficient experimental design, this manuscript aims to discover violently sites that are subject to theeffect of slight changes in position on cavitation and ultrasound intensity distributed in the ultrasonic bath. In addition, optimization several often over-looked ultrasound parameters and experimental conditions, areintended to place the reaction vessel properly and operate under suitable experimental conditions to obtain the maximum yield of target analyte. In this study, an investigation of the various ultrasound intensities and cavitation in ultrasonic bath space were conducted with the help of the orientin yield using ultrasound-assisted extraction. Conventional parameters such as the volume fraction of ethanol, liquid-solid ratio, ultrasound irradiation power, time and frequency, and reaction temperature were investigated, all of which affect the extractive yield factors. Also several often over-looked parameters such as the extraction vessel position in the ultrasonic bath base, the distance between the bottom of the extraction vessel and the ultrasonic bath base, the diameter, the shape and the texture of the extraction vessel, height of the liquid medium and the ultrasound propagating medium salt concentration in the ultrasonic bath were tested exhaustively in this study. These results can therefore serve as a guide to optimize the usage of the ultrasonic bath for future applications.
Impact of CO2-Solvent Separators on the Degradation of Benzyl-2,3-Dihydroxypiperidine-1-Car-boxylate During Preparative Supercritical-Fluid Chromatographic (SFC) Purification J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-14 Kathiravan Asokan, Harshavardhan Naidu, Ratalababu Madam, Khaja Mohiuddin Shaikh, Manjunath Reddy, Hemantha Kumar, Pravin S. Shirude, Muruganantham Rajendran, Ramakanth Sarabu, Dauh-Rurng Wu, Lakshmikant Bajpai, Yingru Zhang
During a preparative separation of the cis enantiomeric pair of benzyl-2,3-dihydroxypiperidine-1-carboxylate using supercritical-fluid chromatography (SFC) with methanol modifier, significant degradation of the products in the collected fractions was observed when a Waters SFC-350® (Milford, MA, USA) was used, but same was not observed when a Waters SFC-80q® (Milford, MA, USA) was used. Through a systematic investigation, we discovered that the compound degraded over time under an acidic condition created by the formation of methyl carbonic acid from methanol and CO2. The extent of the product degradation was dependent on the time and the concentration of CO2 remained in the product fraction, which was governed by the efficiency of CO2–methanol separation during the fraction collection. Hence, we demonstrated that the different designs of CO2–solvent separator (high pressurized cyclone in Waters SFC-350® and low-pressurized vortexing separator in Waters SFC-80q®®) had a significant impact on the degradation of an acid-sensitive compound. The acidity caused by CO2 in methanol was supported by diminished degradation after a nitrogen purging or after neutralizing the collected fractions with a base. Three different solutions to overcome the degradation problem of the acid sensitive compounds using SFC-350® with the high pressurized separator were investigated and demonstrated. The degraded products were isolated as four enantiomers and their relative stereochemistry were established based on 2D NMR data along with the plausible mechanism of degradation.
High-Performance Thin-layer chromatography HPTLC-direct bioautography as a method of choice for alpha-amylase and antioxidant activity evaluation in marine algae J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-14 Snezana Agatonovic-Kustrin, David W. Morton
High-Performance Thin-layer chromatography (HPTLC) combined with DPPH<img border="0" alt="radical dot" src="https://cdn.els-cdn.com/sd/entities/rad"> free radical method and α-amylase bioassay was used to compare antioxidant and antidiabetic activities in ethanol and ethyl acetate extracts from 10 marine macroalgae species (3 Chlorophyta, 4 Phaeophyta and 3 Rhodophyta) from Blue Lagoon beach (Malaysia). Samples were also evaluated for their phenolic and stigmasterol content. On average, higher antioxidant activity was observed in the ethyl acetate extracts (55.1 mg/100 g gallic acid equivalents (GAE) compared to 35.0 mg/100 g GAE) while, as expected, phenolic content was higher in ethanol extracts (330.5 mg/100 g GAE compared to 289.5 mg/100 g GAE). Amounts of fucoxanthin, stigmasterol and α-amylase inhibitory activities were higher in ethyl acetate extracts. Higher enzyme inhibition is therefore related to higher concentrations of triterpenes and phytosterols (Note: these compounds are more soluble in ethyl acetate). Ethyl acetate extracts from Caulerpa racemosa and Padina minor, had the highest α-amylase inhibitory activity, and also showed moderately high antioxidant activities, stigmasterol content and polyphenolic content. Caulerpa racemose, being green algae, does not contain fucoxanthin, while Padina minor, being brown algae, contains high amounts of fucoxanthin. Therefore, it is very unlikely that fucoxanthin contributes to α-amylase inhibitory activity as previously reported.
Application of enzymatic probe sonication for selenium speciation in animal feeds J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-14 Zhiming Xiao, Sheng Li, Jiangpeng Guo, Zhenghua Rao, Chengxin Liu, Zheng Jia, Decheng Suo, Shi Wang, Yang Li, Xia Fan
Enzymatic probe sonication (EPS) was investigated as a novel and alternative technology for the extraction of five Se species SeCys2, MeSeCys, Se (IV), SeMet and Se (VI) from animal feeds. The critical parameters of EPS such as enzyme types, ultrasonic power, sample/enzyme ratio, extraction time and temperature were carefully optimized. Under current conditions, one sample can be extracted in 60s, in contrast to several hours required by the conventional enzymatic methods Moreover, the extraction is performed in pure water, no further temperature control or pH adjustment is needed, and therefore the risk of species interconvertion is drastically reduced or inhibited. The Se species were separated and quantitatively determined by high-performance liquid chromatography-hydride generation atomic fluorescence spectrometry (HPLC-HG-AFS), which allows the separation of organic and inorganic Se species in a single chromatographic run. The newly developed method was successfully applied to the determination of Se species in 18 feed samples collected from markets and local farms. Concerning the feed samples studied, the results of this work suggest that stricter measures should be taken to control the Se-enriched feed supplements in terms of Se species.
Retention and Effective Diffusion of Model Metabolites on Porous Graphitic Carbon J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-14 Daniel B. Lunn, Young J. Yun, James W. Jorgenson
The study of metabolites in biological samples is of high interest for a wide range of biological and pharmaceutical applications. Reversed phase liquid chromatography is a common technique used for the separation of metabolites, but it provides little retention for polar metabolites. An alternative to C18 bonded phases, porous graphitic carbon has the ability to provide significant retention for both non-polar and polar analytes. The goal of this work is to study the retention and effective diffusion properties of porous graphitic carbon, to see if it is suitable for the wide injection bands and long run times associated with long, packed capillary-scale separations. The retention of a set of standard metabolites was studied for both stationary phases over a wide range of mobile phase conditions. This data showed that porous graphitic carbon benefits from significantly increased retention (often > 100 fold) under initial gradient conditions for these metabolites, suggesting much improved ability to focus a wide injection band at the column inlet. The effective diffusion properties of these columns were studied using peak-parking experiments with the standard metabolites under a wide range of retention conditions. Under the high retention conditions, which can be associated with retention after injection loading for gradient separations, Deff/Dm ∼ 0.1 for both the C18-bonded and porous graphitic carbon columns. As C18 bonded particles are widely, and successfully utilized for long gradient separations without issue of increasing peak width from longitudinal diffusion, this suggests that porous graphitic carbon should be amenable for long runtime gradient separations as well.
Quantification of more than 150 micropollutants including transformation products in aqueous samples by liquid chromatography-tandem mass spectrometry using scheduled multiple reaction monitoring J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-13 Nina Hermes, Kevin S. Jewell, Arne Wick, Thomas A. Ternes
A direct injection, multi analytical residue method separated in two chromatographic runs was developed utilizing scheduled analysis to simultaneously quantify 154 compounds, 84 precursors and 70 Transformation products(TPs)/metabolites. Improvements of the chromatographic data quality, sensitivity and reproducibility were achieved by scheduling the analysis of each analyte into pre-determined retention time windows. This study shows the influence of the scan time on the dwell time and the number of data points per peak as well as the effect on the precision of analysis. Lowering the scan time decreased dwell time to a minimal value, however, this had no negative effects on the precision. Increasing the number of data points per peak by decreasing the scan time led to more accurate peak shapes. A final set of parameters was chosen to obtain a minimum of 10 data points per peak to guarantee accurate peak shape and thus reproducibility of analysis. A validation of the method was performed for different water matrices yielding very good linearity for all substances, with limits of quantification mainly in the low to mid ng/L-range and recoveries mainly between 70–125% for surface water, bank filtrate as well as influents and effluents of wastewater treatment plants. The analysis of environmental samples and wastewater revealed the occurrence of selected precursors and TPs in all analyzed matrices: 95% of the compounds in the target list could be quantified in at least one sample. The relevance of TPs and metabolites such as valsartan acid and clopidogrel acid was also confirmed by their detection in all aqueous matrices. Wastewater indicators such as acesulfame and diclofenac were detected at elevated concentrations as well as substances such as oxipurinol which so far were not in the focus of monitoring programs. The developed method can be used for rapid analysis of various water matrices without any sample enrichment and can aid the assessment of water quality and water treatment processes.
Targeted profiling of hydrophilic constituents of royal jelly by Hydrophilic Interactions Liquid Chromatography-tandem Mass Spectrometry. J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-13 Athanasia Pina, Olga Begou, Dimitris Kanelis, Helen Gika, Stavros Kalogiannis, ChrysaTananaki, Georgios Theodoridis, Anastasia Zotou
In the present work a Hydrophilic Interaction Liquid Chromatography-tandem Mass Spectrometry (HILIC-MS/MS) method was developed for the efficient separation and quantification of a large number of small polar bioactive molecules in Royal Jelly. The method was validated and provided satisfactory detection sensitivity for 88 components. Quantification was proven to be precise for 64 components exhibiting good linearity, recoveries R% >90% for the majority of analytes and intra- and inter-day precision from 0.14 to 20% RSD. Analysis of 125 fresh royal jelly samples of Greek origin provided useful information on royal jelly’s hydrophilic bioactive components revealing lysine, ribose, proline, melezitose and glutamic acid to be in high abundance. In addition the occurrence of 18 hydrophilic nutrients which have not been reported previously as royal jelly constituents is shown.
A MODIFIED POISSON-BOLTZMANN EQUATION APPLIED TO PROTEIN ADSORPTION J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-13 Marlon de Souza Gama, Mirella Simões Santos, Eduardo Rocha de Almeida Lima, Frederico Wanderley Tavares, Amaro Gomes Barreto Barreto Jr
Ion-exchange chromatography has been widely used as a standard process in purification and analysis of protein, based on the electrostatic interaction between the protein and the stationary phase. Through the years, several approaches are used to improve the thermodynamic description of colloidal particle-surface interaction systems, however there are still a lot of gaps specifically when describing the behavior of protein adsorption. Here, we present an improved methodology for predicting the adsorption equilibrium constant by solving the modified Poisson-Boltzmann (PB) equation in bispherical coordinates. By including dispersion interactions between ions and protein, and between ions and surface, the modified PB equation used can describe the Hofmeister effects. We solve the modified Poisson-Boltzmann equation to calculate the protein-surface potential of mean force, treated as spherical colloid-plate system, as a function of process variables. From the potential of mean force, the Henry constants of adsorption, for different proteins and surfaces, are calculated as a function of pH, salt concentration, salt type, and temperature. The obtained Henry constants are compared with experimental data for several isotherms showing excellent agreement. We have also performed a sensitivity analysis to verify the behavior of different kind of salts and the Hofmeister effects.
In situ immobilization of layered double hydroxides as stationary phase for capillary electrochromatography J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-12 Xinhong Yu, Wei Zhou, Zilin Chen
Layered double hydroxides (LDHs) have gained much attention in absorption and extraction fields due to their special structure and properties like high porosity, large surface area and excellent anion exchange capacity. However, LDHs are rarely used in capillary electrochromatography (CEC) by date due to the lack of appropriate immobilization method. In this work, by utilizing the unique coordination bonding between metal ions on LDHs and catechol groups on polydopamine layer, a polydopamine modification method was developed for in situ immobilization of LDHs on the inner surface of fused silica capillary. The formation of CoAl-LDHs on polydopamine-immobilized capillary has been characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The CoAl-LDHs-modified open-tubular capillary exhibited good separation performance towards neutral compounds by cation-π interaction and hydrophobic interaction. More interestingly, by virtue of the coordination interaction between metal ions on LDHs layer and phenolic hydroxyl groups, the LDHs-modified capillary has shown good separation efficiency towards various phenolic compounds. Repeatability of the column was studied, with the relative standard deviations for intra-day, inter-day and column-to-column lower than 4.3%.
Applicability of retention modelling in hydrophilic-interaction liquid chromatography for algorithmic optimization programs with gradient-scanning techniques J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-11 Bob W.J. Pirok, Stef R.A. Molenaar, Rianne E. van Outersterp, Peter J. Schoenmakers
Computer-aided method-development programs require accurate models to describe retention and to make predictions based on a limited number of scouting gradients. The performance of five different retention models for hydrophilic-interaction chromatography (HILIC) is assessed for a wide range of analytes. Gradient-elution equations are presented for each model, using Simpson’s Rule to approximate the integral in case no exact solution exists. For most compound classes the adsorption model, i.e. a linear relation between the logarithm of the retention factor and the logarithm of the composition, is found to provide the most robust performance. Prediction accuracies depended on analyte class, with peptide retention being predicted least accurately, and on the stationary phase, with better results for a diol column than for an amide column. The two-parameter adsorption model is also attractive, because it can be used with good results using only two scanning gradients. This model is recommended as the first-choice model for describing and predicting HILIC retention data, because of its accuracy and linearity. Other models (linear solvent-strength model, mixed-mode model) should only be considered after validating their applicability in specific cases.
Preparative fractionation of dextrin by polyethylene glycol: Effects of initial dextrin concentration and pH J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-11 Xiuting Hu, Yu Wang, Chengmei Liu, Zhengyu Jin, Yaoqi Tian
Polyethylene glycol (PEG) was further applied for fractionating dextrin prepared from cassava starch. The initial dextrin concentration and pH of the dextrin solutions were crucially considered in this study with the average molecular-weight dispersity (DMa) as the index. The results showed that the initial dextrin concentration significantly affected the mass fraction and the molecular weight distribution of each dextrin fraction obtained from gradient PEG precipitation. However, the initial dextrin concentration, which ranged from 0.9% to 3.6%, did not affect the DMa of the dextrin fractions. Furthermore, the DMa of the fractions obtained at pHs 4.00, 4.96, 6.00, 6.92, 7.99, 8.96, and 9.91, was 1.364, 1.341, 1.305, 1.286, 1.273, 1.311, and 1.404, respectively, while the dispersity of the parent dextrin was 2.052. These results suggest that the preparative approach, gradient PEG precipitation, is applicable in acidic, neutral, and alkaline environments, and that a weakly alkaline environment is optimal for dextrin fractionation.
Rapid method for the quantification of 13 Sulphonamides in milk by conventional high-performance liquid chromatography with diode array ultraviolet detection using a column packed with core-shell particles J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-11 Antonio Armentano, Simona Summa, Sonia Lo Magro, Carmen Palermo, Donatella Nardiello, Diego Centonze, Marilena Muscarella
In the present study, a column packed with core-shell particles was used for the separation and the quantification of 13 sulphonamides in milk by conventional high-performance liquid chromatography coupled with diode array ultraviolet detection (HPLC/UV-DAD). Preliminary experiments were carried out to investigate selectivity of different stationary phases. Best results were achieved using a C18 column packed with 2.6 μm core-shell particles (diameter 4.6 mm, length 75 mm). A binary gradient elution based on acetate buffer solution at pH 4.50 and a mixture of methanol acetonitrile 50:50 (v/v) was employed at the flow rate of 1.2 mL min−1 with an injection volume of 6 μL. These chromatographic conditions allowed the efficient separation of 13 sulphonamides in about 8 minutes. To evaluate the suitability of the method for official control analysis, the most important validation parameters were investigated according to the European Decision 657/2002/EC as established for analysis of drug residues in food. Sulphonamides were recovered from milk samples by a simple and quick preparation procedure consisting of an extraction step with chloroform/acetone and a purification step with n-hexane. Mean recoveries from raw milk ranged between 55% and 86% at the Maximum Residual Limit of 100 μg kg−1, and RSDs% resulted lower than Thompson and Horwitz RSD% reference values for all sulphonamides. The LOQ value (2.7–15 μg kg−1) was low enough to satisfy legal limits suggested by European Regulation 37/2010/EC.
Graphene deposited onto aligned ZnO nanorods as an efficient coating for headspace solid-phase microextraction of gasoline fractions from oil samples J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-11 Congying Wen, Mengmeng Li, Wangbo Li, Zizhou Li, Wei Duan, Yulong Li, Jie Zhou, Xiyou Li, Jingbin Zeng
The content of gasoline fraction in oil samples is not only an important indicator of oil quality, but also an indispensable fundamental data for oil refining and processing. Before its determination, efficient preconcentration and separation of gasoline fractions from complicated matrices is essential. In this work, a thin layer of graphene (G) was deposited onto oriented ZnO nanorods (ZNRs) as a SPME coating. By this approach, the surface area of G was greatly enhanced by the aligned ZNRs, and the surface polarity of ZNRs was changed from polar to less polar, which were both beneficial for the extraction of gasoline fractions. In addition, the ZNRs were well protected by the mechanically and chemically stable G, making the coating highly durable for use. With headspace SPME (HS-SPME) mode, the G/ZNRs coating can effectively extract gasoline fractions from various oil samples, whose extraction efficiency achieved 1.5-5.4 and 2.1-8.2 times higher than those of a G and commercial 7-μm PDMS coating respectively. Coupled with GC-FID, the developed method is sensitive, simple, cost effective and easily accessible for the analysis of gasoline fractions. Moreover, the method is also feasible for the detection of gasoline markers in simulated oil-polluted water, which provides an option for the monitoring of oil spill accident.
Comprehensive Lipidomic Analysis of Human Plasma using Multidimensional Liquid- and Gas-Phase Separations: Two-dimensional Liquid Chromatography–Mass Spectrometry vs. Liquid Chromatography–Trapped-Ion-Mobility–Mass Spectrometry J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-10 Anna Baglai, Andrea F.G. Gargano, Jan Jordens, Ynze Mengerink, Maarten Honing, Sjoerd van der Wal, Peter J. Schoenmakers
Recent advancements in separation science have resulted in the commercialization of multidimensional separation systems that provide higher peak capacities and, hence, enable a more-detailed characterization of complex mixtures. In particular, two powerful analytical tools are increasingly used by analytical scientists, namely online comprehensive two-dimensional liquid chromatography (LC × LC, having a second-dimension separation in the liquid phase) and liquid chromatography-ion mobility-spectrometry (LC-IMS, second dimension separation in the gas phase). The goal of the current study was a general assessment of the liquid-chromatography − trapped-ion-mobility − mass spectrometry (LC-TIMS-MS) and comprehensive two-dimensional liquid chromatography − mass spectrometry (LC × LC-MS) platforms for untargeted lipid mapping in human plasma. For the first time trapped-ion-mobility spectrometry (TIMS) was employed for the separation of the major lipid classes and ion-mobility-derived collision-cross-section values were determined for a number of lipid standards. The general effects of a number of influencing parameters have been inspected and possible directions for improvements are discussed. We aimed to provide a general indication and practical guidelines for the analyst to choose an efficient multidimensional separation platform according to the particular requirements of the application. Analysis time, orthogonality, peak capacity, and an indicative measure for the resolving power are discussed as main characteristics for multidimensional separation systems.
High-performance thin-layer chromatographic methods in the evaluation of the antioxidant and anti-hyperglycemic activity of Myrmecodia platytyrea as a promising opportunity in diabetes treatment J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-10 S. Agatonovic-Kustrin, D.W. Morton, A. Adam, H.H. Mizaton, H. Zakaria
The steady increase of diabetes is becoming a major burden on health care systems. As diabetic complications arise from oxidative stress, an antioxidant therapy along with anti-diabetic drugs is recommended. Myrmecodia or ant plant is highly valued as a traditional medicine in West Papua. It is used as an alternative treatment for diabetes, as the substances produced by ants can reduce blood sugar levels. The aim of this study was to develop and establish high-performance thin-layer chromatographic (HPTLC)-bioautographic methods to measure the antioxidant and hypoglycemic effects in different extracts from Myrmecodia platytyrea and to compare them with sterol content. Antioxidant activity in methanol, ethanol, dichloromethane (DCM) and ethyl acetate (EA) extracts were measured with a direct HPTLC-2,2-diphenyl-1-picrylhydrazyl free radical (DPPH<img border="0" alt="radical dot" src="https://cdn.els-cdn.com/sd/entities/rad">) assay, while hypoglycemic effects were assessed using a newly developed α-amylase inhibitory activity assay. Stigmasterol is observed, after derivatization with anisaldehyde, as purple colored zones under visible light at hRF values of 0.66. The highest antioxidant activity was observed in the ethanol extract which is rich in polyphenols and flavonoids, while the DCM extract did not show antioxidant activity, but had significant α-amylase inhibitory activity. The highest α-amylase inhibitory activity was observed in the EA and DCM extracts and was related to their stigmasterol content.
Use of chromatographic and electrophoretic tools for assayinFfigg elastase, collagenase, hyaluronidase, and tyrosinase activity J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-09 Syntia Fayad, Philippe Morin, Reine Nehmé
Elastase, collagenase, hyaluronidase and tyrosinase, are very interesting enzymes due to their direct implication in skin aging and as therapeutic hits. Different techniques can be used to study these enzymes and to evaluate the influence of effectors on their kinetics. Nowadays, analytical techniques have become frequently used tools for miniaturizing enzyme assays. The main intention of this article is to review chromatographic and electrophoretic tools that study the four enzymes above mentioned. More specifically, the use of high-performance liquid chromatography and capillary electrophoresis and their derivative techniques for monitoring these enzymes will be investigated. The advantages and limitations of these assays will also be discussed. The original use of microscale thermophoresis and thin layer chromatography in this domain will also be covered.
Determination of phthalic acid esters in water samples using core-shell poly(dopamine) magnetic nanoparticles and gas chromatography tandem mass spectrometry ☆ J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-08 Javier González-Sálamo, Bárbara Socas-Rodríguez, Javier Hernández-Borges, Miguel Ángel Rodríguez-Delgado
In this work, the first application of core-shell poly(dopamine) magnetic nanoparticles as sorbent for the extraction of a group of eleven phthalic acid esters of interest (i.e. diethyl phthalate (DEP), dipropyl phthalate (DPP), dibutyl phthalate (DBP), bis-isopentyl phthalate (DIPP), bis-n-pentyl phthalate (DNPP), benzylbutyl phthalate (BBP), dicyclohexyl phthalate (DCHP), di-(2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP), diisononyl phthalate (DINP) and diisodecyl phthalate (DIDP)) and one adipate (bis (2-ethylhexyl) adipate, DEHA) from different water samples (Milli-Q, mineral, tap, pond and waste water) is proposed. Analysis were carried out by gas chromatography triple quadrupole tandem mass spectrometry. Parameters that affect the extraction performance were optimized following a step by step approach, being the optimum conditions the extraction of water at pH 6, with 60 mg of sorbent and the elution with 6 mL of dichloromethane. The methodology was validated for the five selected water samples using DBP-d4 as internal standard. Determination coefficients of matrix-matched calibration curves were above 0.9904 in all cases while relative recovery values ranged between 71 and 120%, with relative standard deviation values below 19%. The limits of quantification of the method ranged between 9 and 20 ng/L. Matrix effects were found for most analytes and water samples. Real water samples were also analyzed, finding DEP and DBP at concentrations below 4.20 and 1.23 μg/L, respectively, in mineral, tap and waste water. DCHP, DEHP and BBP were also found in some of the samples at concentrations below the LOQs of the method.
Liquid chromatography coupled to quadrupole-Orbitrap high resolution mass spectrometry based method for target analysis and suspect screening of non-ionic surfactants in textiles J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-07 Xin Luo, Li Zhang, Zengyuan Niu, Xiwen Ye, Zhixu Tang, Shuwei Xia
In this study, we describe a high-throughput and sensitive method for textiles analysis, using liquid chromatography coupled to quadrupole-Orbitrap high resolution mass spectrometry (LC-Q-Orbitrap HRMS), for the simultaneously quantitative analysis of 40 target alkylphenol polyethoxylates (APEO) oligomers with reference standards and screening of 160 alcohol polyethoxylates (AEO) oligomers without standards in textiles. The APEOs contain nonylphenol ethoxylates (NPEOs) and octylphenol ethoxylates (OPEOs) with an EO number of ethylene oxide of 1-20, while AEOs focus on C11EOs-C18EOs with an EO number of 1-20. After ultrasonic extraction in methanol, the extract was directly separated using a core-shell CORTECS C18+ column and analyzed by Full MS/dd-MS2 (data dependent acquisition) scan in ESI positive mode. Two best sensitivity experimental conditions for APEOs with short EO chains (AP(EO)1-2) and long EO chains (AP(EO)3-20) were investigated, respectively. Most APEO oligomers had wide concentration ranges and the correlation coefficients (R2) were higher than 0.999. The limit of quantitation (LOQ) values for NP(EO)3-20 oligomers ranges from 16.00 to 52.80 μg/kg and for OP(EO)3-20 oligomers is from 2.40 to 8.00 μg/kg. LOQ for NP(EO)1 and NP(EO)2, OP(EO)1 and OP(EO)2 was 2.40 mg/kg and 0.24 mg/kg, 1.20 mg/kg and 0.16 mg/kg, respectively. The average recovery for each APEO oligomer in cotton and polyester matrix was between 78% and 110% at three spiked levels and the relative standard deviation (RSD %) was below 10%. As to AEOs suspects, a HRMS compound database containing 160 AEO oligomers was built and several parameters such as exact m/z, isotopic patterns, predicted product ions and predicted retention time were used for screening and confirmation. The established method was successfully applied for analysis of 40 commercial textile samples. Compared with OPEOs, NPEOs, especially NP(EO)3-15 oligomers, were widely detected in samples and the total concentration ranged from 1.56 to 1376.31 mg/kg. AEOs were also found in most samples, among which C12-14, C16 and C18 compounds appeared more frequently and the EO chains mainly ranged from 3 to 15.
Explicit role of ionic strength in retention behavior of polystyrene latex particles in sedimentation field-flow fractionation: Slip boundary model J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-07 Kyunil Rah, Sujeong Han, Jaeyeong Choi, Chul Hun Eum, Seungho Lee
We investigate an explicit role of the ionic strength in the retention behaviors of polystyrene (PS) latex particles in sedimentation field-flow fractionation (SdFFF) by hinging upon the retention theory recently developed  as<img height="20" border="0" style="vertical-align:bottom" width="157" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0021967317315650-si4.gif">R=(Ro+vb*)/(1+vb*). Here R is an experimental retention ratio, and Ro is the analytical expression of the standard retention theory based on the parabolic flow velocity. The reduced boundary velocity<img height="15" border="0" style="vertical-align:bottom" width="14" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0021967317315650-si5.gif">vb* is expressed in terms of the ionic strength I of the carrier liquid as <img height="20" border="0" style="vertical-align:bottom" width="132" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0021967317315650-si6.gif">vb*=vb,o*/(1+εI), where <img height="17" border="0" style="vertical-align:bottom" width="83" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S0021967317315650-si7.gif">vb,o*=0.070and ε = 60 mM−1 for all the PS latex systems under investigation. We then apply this to study the explicit ionic strength effect on the retention behaviors of PS beads of 200, 300, 400, and 500 nm, respectively. As a primary result, the strong dependence of the retention ratio on the ionic strength can be quantitatively accounted for in an excellent accuracy: The slip effect at the channel surface is significant, particularly when I ≲ 0.5 mM, without showing any distinguishable dependence on the specific additives to control I, such as FL-70, SDS, NaNO3, and NaN3. Based on the present study, we put forward an experimental means to estimate the ionic strength of an aqueous solution using an FFF technique.
Specific recognition of polyphenols by molecularly imprinted polymers based on a ternary deep eutectic solvent J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-07 Najing Fu, Xiao Liu, Xueyan Hui, Nian Fu, Baokun Tang
Typically, a target compound is selected as a template for a molecularly imprinted polymer (MIP); however, some target compounds are not suitable as templates because of their poor solubility. Using the tailoring properties of a deep eutectic solvent (DES), the insoluble target compound caffeic acid was transformed into a ternary choline chloride–caffeic acid–ethylene glycol (ChCl–CA–EG) DES, which was then employed as a template to prepare MIPs. The ternary DES-based MIPs were characterized by Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy, and atomic force microscopy. The effects of time, temperature, ionic strength, and pH on the recognition processes for four polyphenols (caffeic acid, protocatechuic acid, catechin, and epicatechin) by 13 ChCl–CA–EG ternary DES-based MIPs was investigated using high-performance liquid chromatography. The recognition specificity of the MIPs for CA was significantly better than that for the other polyphenols, and the MIPs exhibited obvious characteristics of chromatographic packing materials. In addition, the recognition processes mainly followed a second-order kinetics model and the Freundlich isotherm model, which together indicated that the MIPs mainly recognized the polyphenols by chemical interactions including ion exchange, electron exchange, and new bond formation. Furthermore, the specific recognition ability of the MIPs for polyphenols, which was better than those of C18, C8, or non-molecularly imprinted polymer adsorbents, was successfully applied to the recognition of polyphenols in a Radix asteris sample. The transformation of an insoluble target compound in a polymeric DES for MIP preparation and recognition is a novel and feasible strategy suitable for use in further MIP research developments.
Unprecedented sensitivity of the planar yeast estrogen screen by using a spray-on technology J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-07 Andreas Schoenborn, Pascal Schmid, Sarah Bräm, Georg Reifferscheid, Marina Ohlig, Sebastian Buchinger
The planar yeast estrogen screen (p-YES) can serve as a highly valuable and sensitive screening tool for the detection of estrogenic compounds in various sample matrices such as water and wastewater, personal care products and foodstuff. The method combines the separation of sample constituents by thin layer chromatography with the direct detection of estrogenic compounds on the surface of the HPTLC-plate. The previous protocol using the immersion of a normal phase silica HPTLC-plate in a cell suspension for bio-autography resulted in blurred signals due to the accelerated diffusion of compounds on the wet surface of the HPTLC-plate. Here, the application of the yeast cells by spraying on the surface of the HPTLC-plate is described as an alternative approach. The presented method for the hyphenation of normal phase thin layer chromatography with a yeast estrogen screen results in much sharper signals compared to reports in previous publications. Satisfying results were achieved using cultures with cell densities of 1000 FAU. Due to the reduced signal broadening, lower limits of quantification for estrogenic compounds were achieved (Estrone (E1) = 2 pg/zone, 17β-estradiol (E2) = 0.5 pg/zone, 17α-ethinylestradiol (EE2) = 0.5 pg/zone and Estriol (E3) = 20 pg/zone). As demonstrated, it is possible to characterize profiles of estrogenic activity of wastewater samples with high quality and reproducibility. The improved sensitivity opens the stage for applications using native samples from waste- or even surface water directly applied on HPTLC-plates without the need for prior sample treatment by e.g. solid phase extraction.
Power Partial-Discard Strategy to Obtain Improved Performance for Simulated Moving Bed Chromatography J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-07 Ji-Woo Chung, Kyung-Min Kim, Tae-Ung Yoon, Seung-Ik Kim, Tae-Sung Jung, Sang-Sup Han, Youn-Sang Bae
A novel power partial-discard (PPD) strategy was developed as a variant of the partial-discard (PD) operation to further improve the separation performance of the simulated moving bed (SMB) process. The PPD operation varied the flow rates of discard streams by introducing a new variable, the discard amount (DA) as well as varying the reported variable, discard length (DL), while the conventional PD used fixed discard flow rates. The PPD operations showed significantly improved purities in spite of losses in recoveries. Remarkably, the PPD operation could provide more enhanced purity for a given recovery or more enhanced recovery for a given purity than the PD operation. The two variables, DA and DL, in the PPD operation played a key role in achieving the desired purity and recovery. The PPD operations will be useful for attaining high-purity products with reasonable recoveries.
Determination of the Content of Alkyl Ketene Dimer in Its Latex by an Ionic-Liquid Assisted Headspace Gas Chromatography J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-07 Ning Yan, Xiao-Fang Wan, Xin-Sheng Chai, Run-Quan Chen, Chun-Xia Chen
This paper reports on an ionic-liquid assisted headspace gas chromatographic (HS-GC) for the determination of the content of alkyl ketene dimer (AKD) in its latex samples, in which the GC system was equipped with a thermal conductivity detector (TCD). The method was based on the AKD hydrolysis conducted in 1-butyl-3-methylimidazolium chloride (ionic-liquid) added medium at 100 °C for 10 min in a closed headspace sample vial, and the measured CO2 (the resulting product of the hydrolysis) by HS-GC. The results showed that the present method has a good measurement precision (RSD < 2.3%) and accuracy (recoveries from 96 − 105%), and the limit of quantitation (LOQ) is 0.9%. The present method is very suitable to be used for the routine check of AKD content in its latex sample in mill applications. The study also showed that the content of AKD in the tested commercial latex samples were in the range of 3.5 to 12%.
Comprehensive profiling of minor tyrosinase inhibitors from Gastrodia elata using an off-line hyphenation of ultrafiltration, high-speed countercurrent chromatography, and high-performance liquid chromatography J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-06 Zhiqiang Wang, Seung Hwan Hwang, Soon Sung Lim
In the present study, a novel hyphenation of ultrafiltration (UF), high-speed countercurrent chromatography (HSCCC), and high-performance liquid chromatography (HPLC) was developed for comprehensive profiling and characterization of the minor tyrosinase inhibitors from Gastrodia elata (GE). A small quantity of GE extract was first fractionated by HSCCC, using elution solvents with a wide range of polarities to enrich minor compounds; then, the fractions were profiled by UF-HPLC to generate a comprehensive 2D chromatogram of the distribution of bioactive components. To determine the binding affinities of these bioactive components, the binding degree (BD%) was calculated by peak area reduction, in which a higher BD% indicates a higher binding affinity to tyrosinase. Among the 212 metabolites, 49 were identified as tyrosinase ligands, 17 of which showed high binding affinity. According to the 2D chromatogram, these 17 candidates were isolated by semiprep-HPLC for characterization of their structure using off-line hyphenated ultraviolet (UV), electron ionized mass spectrometry (EIMS), proton nuclear magnetic resonance (1H NMR). Their activities were further validated by functional assays. In conclusion, the approach developed here can comprehensively identify both major and minor bioactive constituents from natural products, and provide meaningful suggestions to direct further research. Compared to conventional approaches, this approach, developed by hyphenating several techniques, is a highly efficient means for comprehensive profiling of potent minor compounds extracted from natural products.
Broad screening of illicit ingredients in cosmetics using ultra-high-performance liquid chromatography-hybrid quadrupole-Orbitrap mass spectrometry with customized accurate-mass database and mass spectral library J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-02 Xianshuang Meng, Hua Bai, Teng Guo, Zengyuan Niu, Qiang Ma
Comprehensive identification and quantitation of 100 multi-class regulated ingredients in cosmetics was achieved using ultra-high-performance liquid chromatography (UHPLC) coupled with hybrid quadrupole-Orbitrap high-resolution mass spectrometry (Q-Orbitrap HRMS). A simple, efficient, and inexpensive sample pretreatment protocol was developed using ultrasound-assisted extraction (UAE), followed by dispersive solid-phase extraction (dSPE). The cosmetic samples were analyzed by UHPLC-Q-Orbitrap HRMS under synchronous full-scan MS and data-dependent MS/MS (full-scan MS1/dd-MS2) acquisition mode. The mass resolution was set to 70,000 FWHM (full width at half maximum) for full-scan MS1 and 17,500 FWHM for dd-MS2 stage with the experimentally measured mass deviations of less than 2 ppm (parts per million) for quasi-molecular ions and 5 ppm for characteristic fragment ions for each individual analyte. An accurate-mass database and a mass spectral library were built in house for searching the 100 target compounds. Broad screening was conducted by comparing the experimentally measured exact mass of precursor and fragment ions, retention time, isotopic pattern, and ionic ratio with the accurate-mass database and by matching the acquired MS/MS spectra against the mass spectral library. The developed methodology was evaluated and validated in terms of limits of detection (LODs), limits of quantitation (LOQs), linearity, stability, accuracy, and matrix effect. The UHPLC-Q-Orbitrap HRMS approach was applied for the analysis of 100 target illicit ingredients in 123 genuine cosmetic samples, and exhibited great potential for high-throughput, sensitive, and reliable screening of multi-class illicit compounds in cosmetics.
Automated single-ion peak fitting as an efficient approach for analyzing complex chromatographic data J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-02 Gabriel Isaacman-VanWertz, Donna T. Sueper, Kenneth C. Aikin, Brian M. Lerner, Jessica B. Gilman, Joost A. de Gouw, Douglas R. Worsnop, Allen H. Goldstein
Chromatography provides important detail on the composition of environmental samples and their chemical processing. However, the complexity of these samples and their tendency to contain many structurally and chemically similar compounds frequently results in convoluted or poorly resolved data. Data reduction from raw chromatograms of complex environmental data into integrated peak areas consequently often requires substantial operator interaction. This difficulty has led to a bottleneck in analysis that increases analysis time, decreases data quality, and will worsen as advances in field-based instrumentation multiply the quantity and informational density of data produced. In this work, we develop and validate an automated approach to fitting chromatographic data within a target retention time window with a combination of multiple idealized peaks (Gaussian peaks either with or without an exponential decay component). We compare this single-ion peak fitting approach to drawn baseline integration methods of more than 70,000 peaks collected by field-based chromatographs spanning across a wide range of volatilities and functionalities. Accuracy of peak fitting under real-world conditions is found to be within 10%. The quantitative parameters describing the fit (e.g. coefficients, fit residuals, etc.) are found to provide valuable information to increase the efficiency of quality control and provide constraints to accurately integrate peaks that are significantly convoluted with neighboring peaks. Implementation of the peak fitting method is shown to yield accurate integration of peaks otherwise too poorly resolved to separate into individual compounds and improved quantitative metrics to determine the fidelity of the data reduction process, while substantially decreasing the time spent by operators on data reduction.
Preconcentration and Partial Separation of Nitroaromatic Vapors using a Methyltrimethoxysilane-Based Sol-Gel J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-04 Michelle M. Cerreta, Kevin J. Johnson, Braden C. Giordano
Typical trace vapor analysis involves sorbent trapping, followed by desorption and chromatographic separation. This communication describes a method for streamlining this process by combining sorbent sampling/preconcentration with partial separation achieved through temperature-programmed thermal desorption. A novel sorbent trap was formulated in which tubular glass liners for a programmable-temperature gas chromatograph inlet were coated with a sol-gel based polymer stationary phase synthesized from methyltrimethoxysilane precursor and installed into the inlet, which was directly connected to a mass-selective detector by a fused silica capillary transfer line. This method is shown to achieve partial separation of two nitroaromatic vapors in a total 3–5 min analysis time, which represents a tenfold improvement in speed in terms of the overall cycle time compared to an analogous conventional vapor analysis method. Both analytes proved to have a high dynamic range and loading capacity, with nitrobenzene achieving both high and low sampling extremes (0.32 ng to 4 μg sampling concentration) with only a slight compromise in peak broadening. The multivariate curve resolution by alternating least squares algorithm (MCR-ALS) was shown to successfully resolve the overlapped elution profiles of the two nitroaromatic test vapors examined in this study.
Gas chromatographic sulphur speciation in heavy crude oil using a modified standard D5623 method and microfluidic Deans switching J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-04 Nicole E. Heshka, Joanne M. Choy, Jinwen Chen
A modification to American Society for Testing and Materials (ASTM) method D5623 is proposed to enable successful and repeatable analysis of heavy crude oil samples. A two-dimensional gas chromatography configuration was implemented, with separation of sulphur compounds occurring on two columns. A Deans switch is used to enable heart-cutting of volatile sulphur compounds onto a DB-Sulfur stationary phase, and separation occurs concurrently with the backflushing of the primary column. The use of a sulphur-selective detector increases selectivity, and 22 volatile sulphur species are quantified in less than 15 minutes, which is almost half the time of the original ASTM method. Samples ranging from light distillation cuts to whole crudes (boiling from 100 °C to >750 °C) were analyzed with minimal sample preparation. The calculated limit of detection was 0.7 mg/kg, repeatability was 3% relative standard deviation (RSD), and a linear range of 1–250 mg/kg was obtained, with an R2 value of 0.994 or better, depending on the compound.
Optimization and application of fabric phase sorptive extraction coupled to ultra-high performance liquid chromatography tandem mass spectrometry for the determination of cytostatic drug residues in environmental waters J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-04 Sergio Santana-Viera, Rayco Guedes-Alonso, Zoraida Sosa-Ferrera, José Juan Santana-Rodríguez, Abuzar Kabir, Kenneth G. Furton
Every year, hundreds of tons of organic pollutants reach the environment through effluents released from wastewater treatment plants worldwide, and many of these compounds have harmful effects on the aquatic ecosystem. A new class of emerging pollutants of high concern is cytostatic drugs, which are designed to treat different types of cancers by attacking cells. Environmental concentrations of cytostatic drugs are known to be in the range of ng L−1, and for this reason, it is imperative to develop analytical methods of extraction and preconcentration to allow for subsequent instrumental analysis of these drugs.In this work, a rapid, simple and green method for the analysis of seven cytostatic drug compounds that are commonly used in anti-cancer therapies was developed using a novel extraction process based on a powerful miniaturized technique, fabric phase sorptive extraction (FPSE) coupled to ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC–MS/MS).The major parameters that affect the extraction process were optimized. The new method shows good linearity, with a relative standard deviation (RSD) of less than 12%. Relative recoveries higher than 40% were obtained for the studied compounds, and the detection limit of the method was within the values at which these compounds are usually found in environmental water (0.20 ng L−1 to 80 ng L−1). The Limit of Quantification ranged from 0.68 to 267 ng L−1. Significant suppression of the signal due to the matrix effect, a common shortcoming attributed to interference from the extraction process as well as the use of ionization mode, was not observed. Subsequently, the method was applied to real wastewater samples from an effluent obtained from a hospital area and three wastewater treatment plants located in Gran Canaria Island, Spain.
Simultaneous determination of three pesticide adjuvant residues in plant-derived agro-products using liquid chromatography-tandem mass spectrometry J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-01 Hui Li, Zejun Jiang, Xiaolin Cao, Hang Su, Hua Shao, Fen Jin, A.M. Abd El-Aty, Jing Wang
Herein, an accurate and reliable isotope-labelled internal standard method was developed and validated for simultaneous determination of three polar pesticide adjuvants, namely 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone in plant-derived agro-products. Matrices, including apple, cabbage, tomato, cucumber, rice, and wheat were extracted with a modified quick, easy, cheap, effective, rugged, and safe “QuEChERS” method and purified with a new clean-up sorbent (Z-Sep). A hydrophilic interaction liquid chromatography column (HILIC), exhibiting a lipophilic-hydrophilic character, was used to separate the three analytes over 10 min using liquid chromatography–tandem mass spectrometry (LC–MS/MS). Matrix effects in various matrices were evaluated and an isotope-labelled internal standard method was employed to compensate for ion enhancement/suppression effects. At three fortification levels (2.0, 5.0, and 20.0 μg/kg), the mean recoveries ranged from 78.5 to 112.1% with relative standard deviations (RSDs) < 11.0% for all tested analytes. The limits of detection (LODs) and quantification (LOQs) were 0.04–0.45 and 0.12–1.58 μg/kg in various matrices, respectively. The developed experimental protocol was successfully applied to monitor different samples purchased from local markets in Beijing, China. In conclusion, the developed method exhibited both high sensitivity and satisfactory accuracy and is suitable for the simultaneous determination of the three tested pesticide adjuvant residues in agro-products of plant origin.
Dispersive magnetic immunoaffinity extraction. Anatoxin-a determination ☆ J. Chromatogr. A (IF 3.981) Pub Date : 2017-11-01 Tinh Le, Francesc A. Esteve-Turrillas, Sergio Armenta, Miguel de la Guardia, Guillermo Quiñones-Reyes, Antonio Abad-Fuentes, Antonio Abad-Somovilla
Specific monoclonal antibodies were coupled with magnetic Sepharose-based beads and used, for the first time. The methodology was applied to preconcentrate anatoxin-a from water and the later determination by ion mobility spectrometry (IMS). Dispersive magnetic immunoaffinity (d-MagIA) extraction methodology provided a limit of detection of 0.02 μg L−1 and a satisfactory precision with a relative standard deviation lower than 15%. Recoveries were evaluated at 0.5, 1.0 and 5.0 μg L−1 anatoxin-a with quantitative values from 91 to 115%. Additionally, isobaric interferences with phenylalanine were completely avoided by the use of the developed d-MagIA extraction coupled to IMS determinations.
Online extraction of antihypertensive drugs and their metabolites from untreated human serum samples using restricted access carbon nanotubes in a column switching liquid chromatography system J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-31 Henrique Dipe de Faria, Carolina Tosin Bueno, Jose Eduardo Krieger, Eduardo Moacyr Krieger, Alexandre Costa Pereira, Paulo Caleb Júnior Lima Santos, Eduardo Costa Figueiredo
A novel analytical method was developed to determine 5 antihypertensive drugs of different pharmacological classes (angiotensin-converting enzyme inhibitors, calcium channel blockers, α-2 adrenergic receptor agonists, angiotensin II receptor blockers, and aldosterone receptor antagonists) and some of their metabolites in human serum. The untreated samples were directly analyzed in a column switching system using an extraction column packed with restricted access carbon nanotubes (RACNTs) in an ultra-high performance liquid chromatography coupled to a mass spectrometer (UHPLC-MS/MS). The RACNTs column was able to exclude approximately 100% of proteins from the samples in 2.0 min, maintaining the same performance for about 300 analytical cycles. The method was validated in accordance with Food and Drug Administration (FDA) guidelines, being linear for all the determined analytes in their respective analytical ranges (coefficients of determination higher than 0.99) with limits of detection (LODs) and quantification (LOQs) ranging from 0.09 to 10.85 μg L−1 and from 0.30 to 36.17 μg L−1, respectively. High recovery values (88-112%) were obtained as well as suitable results for inter and intra-assay accuracy and precision. The method provided an analytical frequency of 5 samples per hour, including the sample preparation and separation/detection steps. The validated method was successfully used to analyze human serum samples of patients undergoing treatment with antihypertensive drugs, being useful for pharmacometabolomic, pharmacogenomic, and pharmacokinetic studies.
Bifunctionalized ordered mesoporous organosilica synthesized in deep eutectic solvent for extraction of triazine herbicides from watermelon J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-31 Zan Li, Jun Jia, Mingwei Wang, Hua Zhang, Hongyuan Yan, Fengxia Qiao
A C8-and-amino-bifunctionalized ordered mesoporous organosilica (C8-AMS) was prepared in a deep eutectic solvent—a green solvent—that was used as the reaction medium for this procedure instead of organic solvents or other catalyst for the first time. This method provided a nontoxic way for C8 grafting and obtaining an ordered mesoporous organosilica material with both hydrophilic and hydrophobic groups. Besides advantages such as its large surface area, regular and uniform pore size, and hydrothermal stability, the obtained bifunctionalized C8-AMS also have two main functional groups in the obtained structure, C8 and amino, which enriched the adsorption mechanism of the material and as a result improved the adsorption selectivity of C8-AMS. Its performance as an adsorbent was estimated in extracting trace triazine herbicides from watermelon using solid-phase extraction (SPE) followed by high-performance liquid chromatography (HPLC). The proposed method provided satisfactory features in terms of linearity (0.01–2.00 μg g−1), limits of detection (2.9–5.1 ng g−1), accuracy (recovery: 85.7–101.7%), and precision (intra-day and inter-day RSDs: 1.68–2.60% and 3.05–4.01%).
Effect-directed fingerprints of 77 botanicals via a generic high-performance thin-layer chromatography method combined with assays and mass spectrometry J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-29 S. Krüger, L. Hüsken, R. Fornasari, I. Scainelli, G.E. Morlock
Quantitative effect-directed profiles of 77 industrial and fresh botanicals like herbs, spices, vegetables and fruits, widely used as food ingredients, dietary supplements or traditional medicine, gave relevant information on their quality. It allows the assessment of food, dietary supplements and phytomedicines with regard to potential health-promoting activities. In contrary to sum parameter assays and targeted analysis, chromatography combined with effect-directed analysis allows assignment of single active compounds and evaluation of their contribution to the overall activity, originating from a food or botanical sample. High-performance thin-layer chromatography was hyphenated with UV/Vis/FLD detection and effect-directed analysis, using the 2,2-diphenyl-1-picrylhydrazyl radical, Gram-negative Aliivibrio fischeri, Gram-positive Bacillus subtilis, acetylcholinesterase and tyrosinase assays. Bioactive compounds of interest were eluted using an elution head-based interface and further characterized by electrospray ionization (high-resolution) mass spectrometry. This highly streamlined workflow resulted in a hyphenated HPTLC-UV/Vis/FLD-EDA-ESI+/ESI−-(HR)MS method. The excellent quantification power of the method was shown on three compounds. For rosmarinic acid, contents ranged from 4.5 mg/g (rooibos) to 32.6 mg/g (rosemary), for kaempferol from 0.6 mg/g (caraway) to 4.4 mg/g (wine leaves), and for quercetin-3-glu from 1.1 mg/g (hawthorn leaves) to 17.7 mg/g (thyme). Mean repeatabilities (%RSD, n = 2) for all three compounds were mostly ≤5.0% and intermediate precisions (%RSD, n = 3) on different days were mostly ≤8.0%.
A dispersive liquid-liquid microextraction based on solidification of floating organic droplet followed by injector port silylation coupled with gas chromatography-tandem mass spectrometry for the determination of nine bisphenols in bottled carbonated beverages J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-28 Kapil Mandrah, G.N.V. Satyanarayana, Somendu Kumar Roy
In the present study, a method has been efficiently developed for the first time to determine nine bisphenol analogues [bisphenol A (BPA), bisphenol C (BPC), bisphenol AF (BPAF), bisphenol E (BPE), bisphenol F (BPF), bisphenol G (BPG), bisphenol M (BPM), bisphenol S (BPS), and bisphenol Z (BPZ)] together in bottled carbonated beverages (collected from the local market of Lucknow, India) using dispersive liquid-liquid microextraction process. This is based on solidification of floating organic droplet (DLLME-SFO) followed by injector port silylation coupled with gas chromatography–tandem mass spectrometry. The process investigated parameters of DLLME-SFO (including the type of extraction and disperser solvents with their volumes, effect of pH, ionic strength, and the sample volume), factors influencing to injection port derivatization like, collision energy, injector port temperature, derivatizing reagent with sample injection volume, and type of organic solvent. BPA, BPF, BPZ, and BPS were detected in each sample; whereas, other bisphenols were also detected in some carbonated beverage samples. After optimizing the required conditions, good linearity of analytes was achieved in the range of 0.097–100 ng mL−1 with coefficients of determination (R2) ≥ 0.995. Intra-day and inter day precision of the method was good, with relative standard deviation (% RSD) ≤ 10.95%. The limits of detection (LOD) and limits of quantification (LOQ) values of all bisphenols were ranged from 0.021–0.104 ng mL−1 and 0.070–0.343 ng mL−1, respectively. The recovery of extraction was good (73.15–95.08%) in carbonated beverage samples and good enrichment factors (96.36-117.33) were found. Thus, the developed method of microextraction was highly precise, fast, and reproducible to determine the level of contaminants in bottled carbonated beverages.
Determination of γ-hydroxybutyrate in human urine samples by ion exclusion and ion exchange two-dimensional chromatography system J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-28 Junwei Liu, Zhifen Deng, Zuoyi Zhu, Yong Wang, Guoqing Wang, Yu-an Sun, Yan Zhu
A two-dimensional ion chromatography system was developed for the determination of γ-hydroxybutyrate (GHB) in human urine samples. Ion exclusion chromatography was used in the first dimensional separation for elimination of urine matrices and detection of GHB above 10 mg L−1, ion exchange chromatography was used in the second dimensional separation via column-switching technique for detection of GHB above 0.08 mg L−1. Under the optimized chromatographic conditions, the ion exclusion and ion exchange chromatography separation system exhibited satisfactory repeatability (RSD < 3.1%, n = 6) and good linearity in the range of 50–1000 mg L−1 and 0.5–100 mg L−1, respectively. By this method, concentrations of GHB in the selected human urine samples were detected in the range of 0-1.57 mg L−1. The urine sample containing 0.89 mg L−1 GHB was selected to evaluate the accuracy; the spiked recoveries of GHB were 95.9-102.8%. The results showed that the two-dimensional ion chromatography system was convenient and practical for the determination of GHB in human urine samples.
Standing wave design and optimization of a simulated moving bed chromatography for separation of xylobiose and xylose under the constraints on product concentration and pressure drop J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-28 Chung-gi Lee, Jae-Hwan Choi, Chanhun Park, Nien-Hwa Linda Wang, Sungyong Mun
The feasibility of a simulated moving bed (SMB) technology for the continuous separation of high-purity xylobiose (X2) from the output of a β-xylosidase X1→X2 reaction has recently been confirmed. To ensure high economical efficiency of the X2 production method based on the use of xylose (X1) as a starting material, it is essential to accomplish the comprehensive optimization of the X2-separation SMB process in such a way that its X2 productivity can be maximized while maintaining the X2 product concentration from the SMB as high as possible in consideration of a subsequent lyophilization step. To address this issue, a suitable SMB optimization tool for the aforementioned task was prepared based on standing wave design theory. The prepared tool was then used to optimize the SMB operation parameters, column configuration, total column number, adsorbent particle size, and X2 yield while meeting the constraints on X2 purity, X2 product concentration, and pressure drop. The results showed that the use of a larger particle size caused the productivity to be limited by the constraint on X2 product concentration, and a maximum productivity was attained by choosing the particle size such that the effect of the X2-concentration limiting factor could be balanced with that of pressure-drop limiting factor. If the target level of X2 product concentration was elevated, higher productivity could be achieved by decreasing particle size, raising the level of X2 yield, and increasing the column number in the zones containing the front and rear of X2 solute band.
Density dependence of retention factors of trans-stilbene oxide for chiral separation by supercritical fluid chromatography J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-28 Toshitaka Funazukuri, Yuna Ono, Junichi Sakabe, Chang Yi Kong
Retention factors for two enantiomers of trans-stilbene oxide, k1 and k2, were measured with a chiral AD-H column using two syringe pumps to feed CO2 and methanol as a co-solvent at various temperatures, pressures and co-solvent mole fractions to determine the effects of these operating conditions on the retention factors. The retention factors k1 and k2 are for the (R,R)- and (S,S)-forms, respectively. When the isothermal compressibilities of a mixture of CO2 and MeOH were lower than 0.01, far from the critical locus of the CO2 and methanol mixture, both retention factors were well expressed with the solvent density and temperature with an average absolute relative deviation of 1–2%. In the vicinity of the critical locus, however, where the isothermal compressibilities were much larger than 0.01, the relationship between retention factor and density was complicated. Both retention factors were proportional to the isothermal compressibility, irrespective of methanol mole fraction at each temperature.
Partition constant database for totally organic biphasic systems J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-27 Colin F. Poole
A database of partition constants for more than 300 compounds of industrial, environmental and biological interest in nineteen totally organic biphasic systems is reported. The biphasic systems consist of the polar organic solvents acetonitrile, methanol, N,N-dimethylformamide, dimethyl sulfoxide, formamide, propylene carbonate, ethylene glycol, ethanolamine and 3,3,3-trifluoroethanol with n-heptane or n-hexane (10 systems), isopentyl ether (5 systems), 1,2-dichloroethane (2 systems) and 1-octanol (2 systems) of suitable low mutual solubility. The solvation parameter model is used to identify compounds with extreme partition constant values and to develop a selection guide based on the cluster analysis of the model system constants to identify biphasic systems for liquid–liquid extraction.
Determination of reversed-phase high performance liquid chromatography based octanol-water partition coefficients for neutral and ionizable compounds: Methodology evaluation J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-27 Chao Liang, Jun-qin Qiao, Hong-zhen Lian
Reversed-phase liquid chromatography (RPLC) based octanol-water partition coefficient (logP) or distribution coefficient (logD) determination methods were revisited and assessed comprehensively. Classic isocratic and some gradient RPLC methods were conducted and evaluated for neutral, weak acid and basic compounds. Different lipophilicity indexes in logP or logD determination were discussed in detail, including the retention factor logkw corresponding to neat water as mobile phase extrapolated via linear solvent strength (LSS) model from isocratic runs and calculated with software from gradient runs, the chromatographic hydrophobicity index (CHI), apparent gradient capacity factor (kg’) and gradient retention time (tg). Among the lipophilicity indexes discussed, logkw from whether isocratic or gradient elution methods best correlated with logP or logD. Therefore logkw is recommended as the preferred lipophilicity index for logP or logD determination. logkw easily calculated from methanol gradient runs might be the main candidate to replace logkw calculated from classic isocratic run as the ideal lipophilicity index. These revisited RPLC methods were not applicable for strongly ionized compounds that are hardly ion-suppressed. A previously reported imperfect ion-pair RPLC method was attempted and further explored for studying distribution coefficients (logD) of sulfonic acids that totally ionized in the mobile phase. Notably, experimental logD values of sulfonic acids were given for the first time. The IP-RPLC method provided a distinct way to explore logD values of ionized compounds.
Miniaturized matrix solid-phase dispersion followed by liquid chromatography-tandem mass spectrometry for the quantification of synthetic dyes in cosmetics and foodstuffs used or consumed by children ☆ J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-27 Eugenia Guerra, Maria Llompart, Carmen Garcia-Jares
Miniaturized matrix solid-phase dispersion (MSPD) followed by liquid chromatography tandem mass spectrometry (LC–MS/MS) has been proposed for the simultaneous analysis of different classes of synthetic dyes in confectionery and cosmetics intended for or mostly consumed by children. Selected compounds include most of the permitted dyes as food additives as well as some of the most frequently used to color cosmetic products in accordance with the respective European directives. MSPD procedure was optimized by means of experimental design, allowing an effective, rapid and simple extraction of dyes with low sample and reagents consumption (0.1 g of sample and 2 mL of elution solvent). LC-MS/MS was optimized for good resolution, selectivity and sensitivity using a low ionic strength mobile phase (3 mM NH4Ac-methanol). Method performance was demonstrated in real samples showing good linearity (R ≥ 0.9928) and intra- and inter-day precision (%RSD ≤ 15%). Method LODs were ≤ 0.952 μg g−1 and ≤0.476 μg g−1 for confectionery and cosmetic samples, respectively. Recoveries of compounds from nine different matrices were quantitative. The validated method was successfully applied to 24 commercial samples (14 cosmetics and 10 foods) in which 9 of the selected dyes were found at concentrations up to 989 μg g−1, exceeding in some cases the regulated maximum permitted limits. A non-permitted dye, Acid Orange 7, was found in one candy.
Integrated microreactor for enzymatic reaction automation: an easy step toward the quality control of monoclonal antibodies. J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-27 Yoann Ladner, Silvia Mas, Gaelle Coussot, Killian Bartley, Jérôme Montels, Jacques Morel, Catherine Perrin
The main purpose of the present work is to provide a fully integrated miniaturized electrophoretic methodology in order to facilitate the quality control of monoclonal antibodies (mAbs). This methodology called D-PES, which stands for Diffusion-mediated Proteolysis combined with an Electrophoretic Separation, permits to perform subsequently mAb tryptic digestion and electrophoresis separation of proteolysis products in an automated manner. Tryptic digestion conditions were optimized regarding the influence of enzyme concentration and incubation time in order to achieve similar enzymatic digestion efficiency to that obtained with the classical methodology (off-line). Then, the optimization of electrophoretic separation conditions concerning the nature of background electrolyte (BGE), ionic strength and pH was realized. Successful and repeatable electrophoretic profiles of three mAbs digests (Trastuzumab, Infliximab and Tocilizumab), comparable to the off-line digestion profiles, were obtained demonstrating the feasibility and robustness of the proposed methodology. In summary, the use of the proposed and optimized in-line approach opens a new, fast and easy way for the quality control of mAbs.
Metal-organic frameworks as stationary phase for application in chromatographic separation J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-27 Juan Zhang, Zilin Chen
Metal-organic frameworks (MOFs) as a subclass of coordination polymers, have attracted wide interest in various field. Herein, we focus on its application in chromatographic separation due to its excellent physical and chemical properties such as large surface area, high porosity, uniform pore sizes and structural diversity. In 2014, a review was published to summarize the most significant advances in MOFs, and their applications in separation science. The present review was an extensive update on applications of MOFs in chromatographic separation from 2014 to the present such as high-performance liquid chromatography (HPLC), capillary electrochromatography (CEC), nano-liquid chromatography (nano-LC), and gas chromatography (GC). Besides, the typical applications of MOFs in solid-phase microextraction (SPME) were also discussed. Except the presentation of experimental data, the limitations and prospects were also summarized in this review, which can offer an outlook and reference on further study of applications of MOFs.
Column-to-column packing variation of disposable pre-packed columns for protein chromatography J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-26 Susanne Schweiger, Stephan Hinterberger, Alois Jungbauer
In the biopharmaceutical industry, pre-packed columns are the standard for process development, but they must be qualified before use in experimental studies to confirm the required performance of the packed bed. Column qualification is commonly done by pulse response experiments and depends highly on the experimental testing conditions. Additionally, the peak analysis method, the variation in the 3D packing structure of the bed, and the measurement precision of the workstation influence the outcome of qualification runs. While a full body of literature on these factors is available for HPLC columns, no comparable studies exist for preparative columns for protein chromatography. We quantified the influence of these parameters for commercially available pre-packed and self-packed columns of disposable and non-disposable design. Pulse response experiments were performed on 105 preparative chromatography columns with volumes of 0.2–20 ml. The analyte acetone was studied at six different superficial velocities (30, 60, 100, 150, 250 and 500 cm/h). The column-to-column packing variation between disposable pre-packed columns of different diameter-length combinations varied by 10-15%, which was acceptable for the intended use. The column-to-column variation cannot be explained by the packing density, but is interpreted as a difference in particle arrangement in the column. Since it was possible to determine differences in the column-to-column performance, we concluded that the columns were well-packed. The measurement precision of the chromatography workstation was independent of the column volume and was in a range of ± 0.01 ml for the first peak moment and ± 0.007 ml2 for the second moment. The measurement precision must be considered for small columns in the range of 2 ml or less. The efficiency of disposable pre-packed columns was equal or better than that of self-packed columns.
Development of Carbotrap B-packed needle trap device for determination of volatile organic compounds in air J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-26 Ali Poormohammadi, Abdulrahman Bahrami, Maryam Farhadian, Farshid Ghorbani Shahna, Alireza Ghiasvand
SECOND DIMENSION COLUMN ENSEMBLE PRESSURE TUNING IN COMPREHENSIVE TWO-DIMENSIONAL GAS CHROMATOGRAPHY J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-26 Khan M. Sharif, Chadin Kulsing, Ademario I. da silva Junior, Philip J. Marriott
A pressure tunable (PT) coupled column ensemble has been implemented for the second dimension (2D) separation in comprehensive two dimensional gas chromatography (GC × PTGC). This process requires two columns to be connected by a pressure junction, as a replacement for a single narrow bore, short column in 2D. Various 2D1 and 2D2 columns may be selected to provide complementary selectivity (polarity) compared to the 1D column. The tunable residence time arising from differential pressure drop in each 2D column results in a tunable fractional contribution of each column in the 2D separation. A sample mixture comprising different chemical classes, including alkanes and alcohols, is used to identify the feasibility and extent of selectivity tuning possible in GC × PTGC. The column length is also varied due to the imposed challenge of wraparound in the PT coupled column system as pressures are adjusted in the 2D separation. Different experimental parameters, stationary phase materials and column lengths have been applied to investigate and understand the separation behaviour of the 2D PT coupled column GC × GC system. Results are discussed considering analyte retention time, peak width, linear velocity and the contribution of each 2D column. A specific and unexpected example of GC × GC separation was demonstrated where the peak positions of polar and apolar compounds could almost swap their 2D retention position by application of PT. Kerosene was analysed as an example of complex sample analysis by GC × PTGC system. This process is shown to be a practical approach for altering different stationary phase selectivities in a single 2D arrangement in GC × GC.
Multiresidue determination of pesticides in crop plants by the quick, easy, cheap, effective, rugged, and safe method and ultra-high-performance liquid chromatography tandem mass spectrometry using a calibration based on a single level standard addition in the sample J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-26 Mariela S. Viera, Tiele M. Rizzetti, Maiara P. de Souza, Manoel L. Martins, Osmar D. Prestes, Martha B. Adaime, Renato Zanella
In this study, a QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method, optimized by a 23 full factorial design, was developed for the determination of 72 pesticides in plant parts of carrot, corn, melon, rice, soy, silage, tobacco, cassava, lettuce and wheat by ultra-high-performance liquid chromatographic tandem mass spectrometry (UHPLC–MS/MS). Considering the complexity of these matrices and the need of use calibration in matrix, a new calibration approach based on single level standard addition in the sample (SLSAS) was proposed in this work and compared with the matrix-matched calibration (MMC), the procedural standard calibration (PSC) and the diluted standard addition calibration (DSAC). All approaches presented satisfactory validation parameters with recoveries from 70 to 120% and relative standard deviations ≤ 20%. SLSAS was the most practical from the evaluated approaches and proved to be an effective way of calibration. Method limit of detection were between 4.8 and 48 μg kg−1 and limit of quantification were from 16 to 160 μg kg−1. Method application to different kinds of plants found residues of 20 pesticides that were quantified with z-scores values ≤ 2 in comparison with other calibration approaches. The proposed QuEChERS method combined with UHPLC–MS/MS analysis and using an easy and effective calibration procedure presented satisfactory results for pesticide residues determination in different crop plants and is a good alternative for routine analysis.
A modified QuEChERS cleanup method followed by liquid chromatography-tandem mass spectrometry for the rapid analysis of perchlorate, bromate and hypophosphite in flour J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-25 Yanping Xian, Xindong Guo, Xiangchang Hou, Li Wang, Yuluan Wu, Liwei Chen, Hao Dong, Bin Wang
A selective, sensitive and useful method, based on modified QuEChERS cleanup combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) in the negative-ion electrospray ionization (ESI−) mode, was developed and validated for the simultaneous determination of three inorganic anions including perchlorate (ClO4−), bromate (BrO3−) and hypophosphite (H2PO2−) in flour. The extraction parameters and LC–MS/MS conditions were optimized by single-factor experiment and sorbent combination in modified QuEChERS clean-up was optimized through response surface analysis. Three target analytes were separated on a normal-phase Phenomenex Luna Silica (2) column (150 mm × 2.0 mm, 5 μm, 100 Å) with the mobile phase of a mixture of 5 mmol/L ammonium acetate water solution and acetonitrile, detected by MS/MS under multiple reaction monitoring and quantified by external standard method. The developed method was validated in terms of the sensitivity, linearity, accuracy and precision, and matrix effect. The method showed a good linearity (R2 > 0.999) for all analytes in their respective concentration ranges. The ILOQs and MLOQs for perchlorate, bromate and hypophosphite were 0.1, 0.5, 5.0 μg/L and 2.0, 6.0, 60.0 μg/L, respectively. The average recoveries of three target analytes from the negative samples spiked at three different concentrations were in a range from 84.6% to 104.9%. The intra-day precision (n = 6) and inter-day precision (n = 5) of the target analytes were in the ranges of 2.9%–6.9% and 6.4%–8.2%. The matrix effect of this method was observed between 0.83 and 1.17 and was acceptable. The validated method was successfully applied to determine the concentrations of these inorganic anions in flour. Results found that perchlorate and hypophosphite were detected in 33 out of 50 and 7 out of 50 flour samples.
Unravelling the effects of multiple experimental factors in metabolomics, analysis of human neural cells with Hydrophilic Interaction Liquid Chromatography hyphenated to High Resolution Mass Spectrometry ☆ J. Chromatogr. A (IF 3.981) Pub Date : 2017-10-25 Víctor González-Ruiz, Julian Pezzatti, Adrien Roux, Luc Stoppini, Julien Boccard, Serge Rudaz
This work introduces a strategy for decomposing variable contributions within the data obtained from structured metabolomic studies. This approach was applied in the context of an in vitro human neural model to investigate biochemical changes related to neuroinflammation. Neural cells were exposed to the neuroinflammatory toxicant trimethyltin at different doses and exposure times. In the frame of an untargeted approach, cell contents were analysed using HILIC hyphenated with HRMS. Detected features were annotated at level 1 by comparison against a library of standards, and the 126 identified metabolites were analysed using a recently proposed chemometric tool dedicated to multifactorial Omics datasets, namely, ANOVA multiblock OPLS (AMOPLS). First, the total observed variability was decomposed to highlight the contribution of each effect related to the experimental factors. Both the dose of trimethyltin and the exposure time were found to have a statistically significant impact on the observed metabolic alterations. Cells that were exposed for a longer time exhibited a more mature and differentiated metabolome, whereas the dose of trimethyltin was linked to altered lipid pathways, which are known to participate in neurodegeneration. Then, these specific metabolic patterns were further characterised by analysing the individual variable contributions to each effect. AMOPLS was highlighted as a useful tool for analysing complex metabolomic data. The proposed strategy allowed the separation, quantitation and characterisation of the specific contribution of the different factors and the relative importance of every metabolite to each effect with respect to the total observed variability of the system.
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