MCEE: a data preprocessing approach for metabolic confounding effect elimination Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-24 Yitao Li, Mengci Li, Wei Jia, Yan Ni, Tianlu Chen
It is well recognized that physiological and environmental factors such as race, age, gender, and diurnal cycles often have a definite influence on metabolic results that statistically manifests as confounding variables. Currently, removal or controlling of confounding effects relies heavily on experimental design. There are no available data processing techniques focusing on the compensation of their effects. We therefore proposed a new method, Metabolic confounding effect elimination (MCEE), to remove the influence of specified confounding factors and make the data more accurate. The method consists of three steps: metabolites grouping, confounder-related metabolites selection, and metabolites modification. Its effectiveness and advantages were evaluated comprehensively by several simulated models and real datasets, and were compared with two typical methods, the principal component analysis (PCA)- and the direct orthogonal signal correction (DOSC)-based methods. MCEE is simple, effective, and safe, and is independent of sample number, association degree, and missing value. Hence, it may serve as a good complement to existing metabolomics data preprocessing methods and aid in better understanding the metabolic and biological status of interest.
Speciation analysis of arsenic in seafood and seaweed: Part II—single laboratory validation of method Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-23 Mesay Mulugeta Wolle, Sean D. Conklin
Single laboratory validation of a method for arsenic speciation analysis in seafood and seaweed is presented. The method is based on stepwise extraction of water-soluble and non-polar arsenic with hot water and a mixture of dichloromethane and methanol, respectively. While the water-soluble arsenicals were speciated by anion and cation exchange liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS), the non-polar arsenicals were collectively determined by ICP-MS after digestion in acid. The performance characteristics and broad application of the method were evaluated by analyzing eight commercial samples (cod, haddock, mackerel, crab, shrimp, geoduck clam, oyster, and kombu) and four reference materials (fish protein (DORM-4), lobster hepatopancreas (TORT-3), mussel tissue (SRM 2976), and hijiki seaweed (CRM 7405-a)) representing finfish, crustaceans, molluscs, and seaweed. Matrices spiked at three levels in duplicates were also analyzed. The stepwise extraction provided 76–106% extraction of the total arsenic from the test materials. The method demonstrated satisfactory repeatability for analysis of replicate extracts prepared over several days. The accuracy of the method was evaluated by analyzing reference materials certified for both total arsenic and a few arsenicals; the experimental results were 90–105% of the certified values. Comparison between the total water-soluble arsenic and the sum of the concentrations of the chromatographed species gave 80–92% mass balance. While spike recoveries of most arsenicals were in the acceptance range set by CODEX, a few species spiked into cod, haddock, and shrimp were poorly recovered due to transformation to other forms. After thorough investigations, strategies were devised to improve the recoveries of these species by averting their transformations. Limits of quantification (LOQ) for the extraction and quantification of 16 arsenicals using the current method were in the range 6–16 ng g−1 arsenic.
Toward miniaturized analysis of chemical identity and purity of radiopharmaceuticals via microchip electrophoresis Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-22 Jimmy Ly, Noel S. Ha, Shilin Cheung, R. Michael van Dam
Miniaturized synthesis of positron emission tomography (PET) tracers is poised to offer numerous advantages including reduced tracer production costs and increased availability of diverse tracers. While many steps of the tracer production process have been miniaturized, there has been relatively little development of microscale systems for the quality control (QC) testing process that is required by regulatory agencies to ensure purity, identity, and biological safety of the radiotracer before use in human subjects. Every batch must be tested, and in contrast with ordinary pharmaceuticals, the whole set of tests of radiopharmaceuticals must be completed within a short-period of time to minimize losses due to radioactive decay. By replacing conventional techniques with microscale analytical ones, it may be possible to significantly reduce instrument cost, conserve lab space, shorten analysis times, and streamline this aspect of PET tracer production. We focus in this work on miniaturizing the subset of QC tests for chemical identity and purity. These tests generally require high-resolution chromatographic separation prior to detection to enable the approach to be applied to many different tracers (and their impurities), and have not yet, to the best of our knowledge, been tackled in microfluidic systems. Toward this end, we previously explored the feasibility of using the technique of capillary electrophoresis (CE) as a replacement for the “gold standard” approach of using high-performance liquid chromatography (HPLC) since CE offers similar separating power, flexibility, and sensitivity, but can readily be implemented in a microchip format. Using a conventional CE system, we previously demonstrated the successful separation of non-radioactive version of a clinical PET tracer, 3′-deoxy-3′-fluorothymidine (FLT), from its known by-products, and the separation of the PET tracer 1-(2′-deoxy-2′-fluoro-β-D-arabinofuranosyl)-cytosine (D-FAC) from its α-isomer, with sensitivity nearly as good as HPLC. Building on this feasibility study, in this paper, we describe the first effort to miniaturize the chemical identity and purity tests by using microchip electrophoresis (MCE). The fully automated proof-of-concept system comprises a chip for sample injection, a separation capillary, and an optical detection chip. Using the same model compound (FLT and its known by-products), we demonstrate that samples can be injected, separated, and detected, and show the potential to match the performance of HPLC. Addition of a radiation detector in the future would enable analysis of radiochemical identity and purity in the same device. We envision that eventually this MCE method could be combined with other miniaturized QC tests into a compact integrated system for automated routine QC testing of radiopharmaceuticals in the future.
Compact devices for generation of reference trace VOC mixtures: a new concept in assuring quality at chemical and biochemical laboratories Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-22 Alessia Demichelis, Céline Pascale, Maricarmen Lecuna, Bernhard Niederhauser, Guido Sassi, Maria Paola Sassi
Volatile organic compounds (VOCs) in gas mixtures at trace level (nmol/mol) are routinely measured by chemical and biochemical laboratories as climate indicators, indoor air quality pollutants from building materials emissions, contaminants in food and beverages, and biomarkers in body fluids (blood, urine, breath) of occupational exposure or human diseases. Current analytical instruments used for measurements are gas chromatographs equipped with various injector and detector configurations. The assurance of measurement quality is done by using a huge amount of certified liquid VOC standard solutions (or gaseous VOC standard cylinders) with multiple dilutions to reach the required trace level. This causes high standard uncertainty in instrument calibrations, high cost, and high consumption of analysis and laboratory personal time. In this paper, we present the implementation of portable generators producing VOC gas standards at trace level for automatic and direct calibration of VOC detectors employed in various contexts, removing the need for preparation of matrix calibration standards in cylinders. Two compact devices in-house developed by two national metrology institutes—the Istituto Nazionale di Ricerca Metrologica (INRIM) and the Federal Institute of Metrology (METAS)—are here used to dynamically generate reference gas mixtures in an SI traceable way. The two devices are based on different technologies: diffusion and permeation, for INRIM and METAS, respectively. A metrological characterization is given and the practical implementation at chemical and biochemical laboratories is discussed.
A near-infrared fluorescent sensor with large Stokes shift for rapid and highly selective detection of thiophenols in water samples and living cells Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-01-23 Rongjin Zeng, Qian Gao, Fenmin Cheng, Yunshan Yang, Peisheng Zhang, Shu Chen, Heping Yang, Jian Chen, Yunfei Long
The development of simple methods with high sensitivity and selectivity to differentiate toxic aromatic thiols (thiophenols) from aliphatic thiols (cysteine, homocysteine, and glutathione) and hydrogen sulfide (H2S) is of great significance. Herein, we report on the fabrication of a novel near-infrared (NIR) fluorescent sensor for rapid and highly selective detection of thiophenols through the photoinduced electron transfer (PET) mechanism. In the presence of the thiophenols, an obvious enhancement of NIR fluorescence at 658 nm could be visualized with the aid of nucleophilic aromatic substitution (SNAr) reaction. The sensor displays large Stokes shift (~ 227 nm), fast response time (< 30 s), high sensitivity (~ 8.3 nM), and good biocompatibility. Moreover, the as-prepared sensor possesses an excellent anti-interference feature even when other possible interferents exist (aliphatic thiols and H2S) and has been successfully utilized for thiophenol detection in both water samples and living cells.
A sensitive method using SPME pre-concentration for the quantification of aromatic amines in indoor air Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-01-20 Vincent Lucaire, Jean-Jacques Schwartz, Olivier Delhomme, Ruben Ocampo-Torres, Maurice Millet
Monitoring the levels of aliphatic and aromatic amines (AA) in indoor air is important to protect human health because of exposure to these compounds through diet and inhalation. A sampling and analytical method using XAD-2 cartridges and gas chromatography coupled to mass spectrometry used for assessing 25 AA in different smoking and non-smoking indoor environment was developed. After sampling and delivering 1 m3 of air (6–8 h sampling), an adsorbent was ultrasonically extracted with acetonitrile, concentrated to 1 mL and diluted in 25 mL of water (pH = 9; 5% NaCl), and then extracted for 40 min at 80 °C using a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber and injected in a GC/MS system. With this method, 22 of the 25 AA can be analyzed with detection limits up to five times lower than that of classic liquid injection. Benzylamine, 3-aminophenol, and 4-aminophenol were not detected with the solid-phase micro-extraction (SPME) method. It can be assumed that aminophenols required a derivatization step for their analysis by GC as these molecules were not detected regardless of the injection mode used.
G-quadruplex aptamer selection using capillary electrophoresis-LED-induced fluorescence and Illumina sequencing Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-01-29 Audrey Ric, Vincent Ecochard, Jason S. Iacovoni, Audrey Boutonnet, Frédéric Ginot, Varravaddheay Ong-Meang, Véréna Poinsot, Laurent Paquereau, François Couderc
One of the major difficulties that arises when selecting aptamers containing a G-quadruplex is the correct amplification of the ssDNA sequence. Can aptamers containing a G-quadruplex be selected from a degenerate library using non-equilibrium capillary electrophoresis (CE) of equilibrium mixtures (NECEEM) along with high-throughput Illumina sequencing? In this article, we present some mismatches of the G-quadruplex T29 aptamer specific to thrombin, which was PCR amplified and sequenced by Illumina sequencing. Then, we show the proportionality between the number of sequenced molecules of T29 added to the library and the number of sequences obtained in Illumina sequencing, and we find that T29 sequences from this aptamer can be detected in a random library of ssDNA after the sample is fractionated by NECEEM, amplified by PCR, and sequenced. Treatment of the data by the counting of double-stranded DNA T29 sequences containing a maximum of two mismatches reveals a good correlation with the enrichment factor (fE). This factor is the ratio of the number of aptamer sequences found in the collected complex sample divided by the total number of sequencing reads (aptamer and non-aptamer) plus the quantity of T29 molecules (spiked into a DNA library) injected into CE.
Extraction and detection of bisphenol A in human serum and urine by aptamer-functionalized magnetic nanoparticles Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-01-26 Yu Su, Chenggang Shao, Xielin Huang, Jinxia Qi, Renshan Ge, Huaqin Guan, Zhenkun Lin
A new type of magnetic nanoparticles (MNPs), as the absorbents of bisphenol A (BPA), was prepared by functionalization of Fe3O4@SiO2 with BPA-specific aptamer in this work. ssDNA aptamer was immobilized on the Fe3O4@SiO2 surface through biotin-avidin interactions, playing a role of the specific probe for BPA. The resultant materials (Apt-MNPs) exhibited outstanding magnetic responsibility and can be separated efficiently by the magnetic field. Experimental results also showed that Apt-MNPs had large adsorption capacity and high competitive selectivity for the targeted compound BPA. Furthermore, Apt-MNPs were adopted as the specific absorbents to extract and enrich BPA from human serum and urine samples. Therefore, an efficient detection method of BPA was developed in combination with high-performance liquid chromatography (HPLC). The linearity of the method was over a range of 5–10,000 ng mL−1 with a correlation coefficient of 0.99997, and the limit of detections (LODs) for serum and urine were 2.0 and 1.0 ng mL−1, respectively. The recoveries of BPA in the spiked human serum and urine samples were 90.8 ± 7.3% (RSD) and 92.3 ± 1.5%, respectively. Our results demonstrated that Apt-MNPs were high-performance adsorbents for extracting and enriching BPA, resulting in fast and efficient detection of BPA in serum and urine samples.
Multiplex highly sensitive immunochromatographic assay based on the use of nonprocessed antisera Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-01-20 Nadezhda A. Byzova, Alexandr E. Urusov, Anatoly V. Zherdev, Boris B. Dzantiev
The format of an immunochromatographic multiassay is first proposed with native antisera and a universal conjugate of antispecies antibodies with gold nanoparticles. This format allows (1) the exclusion of purification and conjugation stages for specific antibodies and (2) significant reduction of the concentration of specific antibodies in the system. The independent use of specific antibodies and a conjugated marker provided a low detection limit and high signal intensity. The proposed format was implemented for the simultaneous detection of two herbicides. The instrumental limits for the detection of atrazine and chlorsulfuron were 0.1 and 0.7 ng/mL, respectively, and the analysis time was 20 min. The suitability of the test system for monitoring these herbicides in nontreated apple and blackcurrant juices is shown. The assay technique is simple, sensitive, and easily transferrable to any other antigen.
Simultaneous quantification of endogenous and exogenous plasma glucose by isotope dilution LC-MS/MS with indirect MRM of the derivative tag Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-01-23 Lingling Yu, Chao Wen, Xing Li, Shiqi Fang, Lichuan Yang, Tony Wang, Kaifeng Hu
Quantification of endogenous and exogenous plasma glucose can help more comprehensively evaluate the glucose metabolic status. A ratio-based approach using isotope dilution liquid chromatography tandem mass spectrometry (ID LC-MS/MS) with indirect multiple reaction monitoring (MRM) of the derivative tag was developed to simultaneously quantify endo-/exogenous plasma glucose. Using diluted D-[13C6] glucose as tracer of exogenous glucose, 12C6/13C6 glucoses were first derivatized and then data were acquired in MRM mode. The metabolism of exogenous glucose can be tracked and the concentration ratio of endo/exo-genous glucose can be measured by calculating the endo-/exo-genous glucose concentrations from peak area ratio of specific daughter ions. Joint application of selective derivatization and MRM analysis not only improves the sensitivity but also minimizes the interference from the background of plasma, which warrants the accuracy and reproducibility. Good agreement between the theoretical and calculated concentration ratios was obtained with a linear correlation coefficient (R) of 0.9969 in the range of D-glucose from 0.5 to 20.0 mM, which covers the healthy and diabetic physiological scenarios. Satisfactory reproducibility was obtained by evaluation of the intra- and inter-day precisions with relative standard deviations (RSDs) less than 5.16%, and relative recoveries of 85.96 to 95.92% were obtained at low, medium, and high concentration, respectively. The method was successfully applied to simultaneous determination of the endo-/exogenous glucose concentration in plasma of non-diabetic and type II diabetic cynomolgus monkeys.
Sensitive electrochemical detection of microRNA-21 based on propylamine-functionalized mesoporous silica with glucometer readout Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-01-20 Kun Deng, Yong Zhang, Xuedong Tong
A new homogeneous electrochemical sensing system was developed for sensitive detection of microRNA-21 (miRNA-21) based on target-induced glucose release from propylamine-functionalized mesoporous silica nanoparticle (MSN) with glucometer readout. Glucose molecules (as the signal tracers) were initially gated into the pores through the interaction of the negatively charged anchor DNA with the aminated MSN. Upon addition of target miRNA, the analyte competitively hybridized with anchor DNA to form the RNA-DNA duplex, thus resulting in detachment of anchor DNA from the MSN accompanying the pore opening. The loaded glucose molecules released out from the pores because of concentration gradients, which could be detected by using a portable personal glucometer (PGM). Experimental results indicated that the PGM signal increased with the increasing miRNA level, and exhibited a good linear dependence on the miRNA-21 concentration from 50 pM to 5.0 nM with a detection limit of 19 pM under optimum conditions. Additionally, multifunctional mesoporous silica nanoparticles also showed good stability and favorable selectivity, and satisfactory accuracy for the miRNA detection in cell lysates with quantitative real-time polymerase chain reaction (qRT-PCR). Such good analytical performance endows it as a promising scheme for the efficient and convenient detection of miRNA in clinical diagnosis and therapy.
Trace analysis of pesticide residues in sediments using liquid chromatography–high-resolution Orbitrap mass spectrometry Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-01 Christina I. Nannou, Vasiliki I. Boti, Triantafyllos A. Albanis
The present study describes the optimization and validation of an analytical method based on quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction and purification with dispersive solid-phase extraction (dSPE) before analysis, followed by ultrahigh-performance liquid chromatography–high-resolution linear ion trap/Orbitrap (LTQ Orbitrap) mass spectrometry for the determination of 18 pesticides in sediment. To optimize process efficiency, parameters such as pH, extraction salts, sediment amount, and cleanup sorbents were evaluated. Identification was based on both accurate mass and retention time, and further confirmation was achieved by mass spectrometry fragmentation. The optimized analytical method demonstrated good validation characteristics, such as accuracy (recoveries from 70.8% to 106.2%), method quantification limits (below 10 ng g-1 for 89% of the pesticides selected), linearity (coefficient of determination greater than 0.9921 in all cases), precision (repeatability and reproducibility with standard deviations below 18% and 21%, respectively), and matrix effect (signal suppression was exhibited for almost all analytes). The overall method performance, expressed as process efficiency, ranged from 58.8% to 102.1%. The validated method was successfully applied to real samples collected along two rivers in northwestern Greece, revealing the presence of three selected pesticides but at levels below the method quantification limit.
Spatially resolved chemical analysis of cicada wings using laser-ablation electrospray ionization (LAESI) imaging mass spectrometry (IMS) Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-01-30 Jessica K. Román, Callee M. Walsh, Junho Oh, Catherine E. Dana, Sungmin Hong, Kyoo D. Jo, Marianne Alleyne, Nenad Miljkovic, Donald M. Cropek
Laser-ablation electrospray ionization (LAESI) imaging mass spectrometry (IMS) is an emerging bioanalytical tool for direct imaging and analysis of biological tissues. Performing ionization in an ambient environment, this technique requires little sample preparation and no additional matrix, and can be performed on natural, uneven surfaces. When combined with optical microscopy, the investigation of biological samples by LAESI allows for spatially resolved compositional analysis. We demonstrate here the applicability of LAESI-IMS for the chemical analysis of thin, desiccated biological samples, specifically Neotibicen pruinosus cicada wings. Positive-ion LAESI-IMS accurate ion-map data was acquired from several wing cells and superimposed onto optical images allowing for compositional comparisons across areas of the wing. Various putative chemical identifications were made indicating the presence of hydrocarbons, lipids/esters, amines/amides, and sulfonated/phosphorylated compounds. With the spatial resolution capability, surprising chemical distribution patterns were observed across the cicada wing, which may assist in correlating trends in surface properties with chemical distribution. Observed ions were either (1) equally dispersed across the wing, (2) more concentrated closer to the body of the insect (proximal end), or (3) more concentrated toward the tip of the wing (distal end). These findings demonstrate LAESI-IMS as a tool for the acquisition of spatially resolved chemical information from fragile, dried insect wings. This LAESI-IMS technique has important implications for the study of functional biomaterials, where understanding the correlation between chemical composition, physical structure, and biological function is critical.
Simultaneous dispersive liquid-liquid microextraction derivatisation and gas chromatography mass spectrometry analysis of subcritical water extracts of sweet and sour cherry stems Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-01-31 Jaroslava Švarc-Gajić, Sabrina Clavijo, Ruth Suárez, Aleksandra Cvetanović, Víctor Cerdà
Cherry stems have been used in traditional medicine mostly for the treatment of urinary tract infections. Extraction with subcritical water, according to its selectivity, efficiency and other aspects, differs substantially from conventional extraction techniques. The complexity of plant subcritical water extracts is due to the ability of subcritical water to extract different chemical classes of different physico-chemical properties and polarities in a single run. In this paper, dispersive liquid-liquid microextraction (DLLME) with simultaneous derivatisation was optimised for the analysis of complex subcritical water extracts of cherry stems to allow simple and rapid preparation prior to gas chromatography-mass spectrometry (GC-MS). After defining optimal extracting and dispersive solvents, the optimised method was used for the identification of compounds belonging to different chemical classes in a single analytical run. The developed sample preparation protocol enabled simultaneous extraction and derivatisation, as well as convenient coupling with GC-MS analysis, reducing the analysis time and number of steps. The applied analytical protocol allowed simple and rapid chemical screening of subcritical water extracts and was used for the comparison of subcritical water extracts of sweet and sour cherry stems.
High-performance non-enzymatic catalysts based on 3D hierarchical hollow porous Co 3 O 4 nanododecahedras in situ decorated on carbon nanotubes for glucose detection and biofuel cell application Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-01 Shiyue Wang, Xiaohua Zhang, Junlin Huang, Jinhua Chen
In this work, high-performance non-enzymatic catalysts based on 3D hierarchical hollow porous Co3O4 nanododecahedras in situ decorated on carbon nanotubes (3D Co3O4-HPND/CNTs) were successfully prepared via direct carbonizing metal-organic framework-67 in situ grown on carbon nanotubes. The morphology, microstructure, and composite of 3D Co3O4-HPND/CNTs were characterized by scanning electron microscopy, transmission electron microscopy, micropore and chemisorption analyzer, and X-ray diffraction. The electrochemical characterizations indicated that 3D Co3O4-HPND/CNTs present considerably catalytic activity toward glucose oxidation and could be promising for constructing high-performance electrochemical non-enzymatic glucose sensors and glucose/O2 biofuel cell. When used for non-enzymatic glucose detection, the 3D Co3O4-HPND/CNTs modified glassy carbon electrode (3D Co3O4-HPND/CNTs/GCE) exhibited excellent analytical performance with high sensitivity (22.21 mA mM−1 cm−2), low detection limit of 0.35 μM (S/N = 3), fast response (less than 5 s) and good stability. On the other hand, when the 3D Co3O4-HPND/CNTs/GCE worked as an anode of a biofuel cell, a maximum power density of 210 μW cm−2 at 0.15 V could be obtained, and the open circuit potential was 0.68 V. The attractive 3D hierarchical porous structural features, the large surface area, and the excellent conductivity based on the continuous and effective electron transport network in 3D Co3O4-HPND/CNTs endow 3D Co3O4-HPND/CNTs with the enhanced electrochemical performance and promising applications in electrochemical sensing, biofuel cell, and other energy storage and conversion devices such as supercapacitor.
Multiresidue analysis of oestrogenic compounds in cow, goat, sheep and human milk using core-shell polydopamine coated magnetic nanoparticles as extraction sorbent in micro-dispersive solid-phase extraction followed by ultra-high-performance liquid chromatography tandem mass spectrometry Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-01 Bárbara Socas-Rodríguez, Javier Hernández-Borges, Antonio V. Herrera-Herrera, Miguel Ángel Rodríguez-Delgado
In this work, the suitability of Fe3O4 nanoparticles coated with polydopamine was evaluated as sorbent for the extraction of a group of 21 compounds with oestrogenic activity including seven phytoestrogens, six mycotoxins as well as four synthetic and four natural oestrogens from different types of milk, including sheep milk, in which the evaluation of oestrogenic compounds have never been developed before. Extraction was carried out using magnetic micro-dispersive solid-phase extraction after a previous deproteinisation step. Separation, determination and quantification of the target analytes were achieved by ultra-high-performance liquid chromatography coupled to triple quadrupole-tandem mass spectrometry. The methodology was validated for five milk samples using 17β-estradiol-2,4,16,16,17-d5 as internal standard for natural and synthetic oestrogens, β-zearalanol-10,10,11,12,12-d5 for mycotoxins and prunetin for phytoestrogens. Recovery values ranged from 70 to 120% for the five types of matrices with relative standard deviation values lower than 18%. Limits of quantification of the method were in the range 0.55–11.8 μg L−1 for all samples.
Performance of combined fragmentation and retention prediction for the identification of organic micropollutants by LC-HRMS Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-01-30 Meng Hu, Erik Müller, Emma L. Schymanski, Christoph Ruttkies, Tobias Schulze, Werner Brack, Martin Krauss
In nontarget screening, structure elucidation of small molecules from high resolution mass spectrometry (HRMS) data is challenging, particularly the selection of the most likely candidate structure among the many retrieved from compound databases. Several fragmentation and retention prediction methods have been developed to improve this candidate selection. In order to evaluate their performance, we compared two in silico fragmenters (MetFrag and CFM-ID) and two retention time prediction models (based on the chromatographic hydrophobicity index (CHI) and on log D). A set of 78 known organic micropollutants was analyzed by liquid chromatography coupled to a LTQ Orbitrap HRMS with electrospray ionization (ESI) in positive and negative mode using two fragmentation techniques with different collision energies. Both fragmenters (MetFrag and CFM-ID) performed well for most compounds, with average ranking the correct candidate structure within the top 25% and 22 to 37% for ESI+ and ESI− mode, respectively. The rank of the correct candidate structure slightly improved when MetFrag and CFM-ID were combined. For unknown compounds detected in both ESI+ and ESI−, generally positive mode mass spectra were better for further structure elucidation. Both retention prediction models performed reasonably well for more hydrophobic compounds but not for early eluting hydrophilic substances. The log D prediction showed a better accuracy than the CHI model. Although the two fragmentation prediction methods are more diagnostic and sensitive for candidate selection, the inclusion of retention prediction by calculating a consensus score with optimized weighting can improve the ranking of correct candidates as compared to the individual methods.
Quantification of organic solvents in aquatic toys and swimming learning devices and evaluation of their influence on the smell properties of the corresponding products Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-20 Christoph Wiedmer, Andrea Buettner
Based on the observation that the characteristic odour of inflatable aquatic toys for children is predominantly caused by residues of hazardous organic solvents, the concentrations of cyclohexanone, isophorone and phenol were determined in a selection of 20 products obtained from online suppliers located in Germany. Analytes were extracted with dichloromethane after the addition of non-labelled internal standards, and the volatile fraction was isolated using solvent-assisted flavour evaporation (SAFE). Extracts were then concentrated by Vigreux distillation and analysed by means of gas chromatography with mass spectrometric detection (GC-MS). Furthermore, each sample was evaluated regarding its specific olfactory properties by an expert sensory panel. While some samples did not contain significant amounts of solvents, cyclohexanone concentrations above the lower limit of quantification (LLOQ) were determined in nine samples with six samples containing high concentrations ranging from about 1 to 7 g/kg cyclohexanone. Isophorone concentrations above the LLOQ were observed in eight samples. Thereby, six products contained between 0.3 and 1.6 g/kg isophorone and the remaining two samples contained even about 5 g/kg isophorone, each. Likewise, phenol concentrations exceeded the LLOQ in 14 cases, with four samples containing elevated amounts ranging from about 140 to 280 mg/kg phenol.
Ionic liquid phases with comprehensive two-dimensional gas chromatography of fatty acid methyl esters Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-17 Siriluck Pojjanapornpun, Yada Nolvachai, Kornkanok Aryusuk, Chadin Kulsing, Kanit Krisnangkura, Philip J. Marriott
New generation inert ionic liquid (iIL) GC columns IL60i, IL76i and IL111i, comprising phosphonium or imidazolium cationic species, were investigated for separation of fatty acid methyl esters (FAME). In general, the iIL phases provide comparable retention times to their corresponding conventional columns, with only minor selectivity differences. The average tailing factors and peak widths were noticeably improved (reduced) for IL60i and IL76i, while they were slightly improved for IL111i. Inert IL phase columns were coupled with conventional IL columns in comprehensive two-dimensional GC (GC × GC) with a solid-state modulator which offers variable modulation temperature (TM), programmable TM during analysis and trapping stationary phase material during the trap/release (modulation) process, independent of oven T and column sets. Although IL phases are classified as polar, relative polarity of the two phases comprising individual GC × GC column sets permits combination of less-polar IL/polar IL and polar IL/less-polar IL column sets; it was observed that a polar/less-polar column set provided better separation of FAME. A higher first dimension (1D) phase polarity combined with a lower 2D phase polarity, for instance 1D IL111i with 2D IL59 gave the best result; the greater difference in 1D/2D phase polarity results in increasing occupancy of peak area in the 2D space. The IL111i/IL59 column set was selected for analysis of fatty acids in fat and oil products (butter, margarine, fish oil and canola oil). Compared with the conventional IL111, IL111i showed reduced column bleed which makes this more suited to GC × GC analysis of FAME. The proposed method offers a fast profiling approach with good repeatability of analysis of FAME.
Utilizing hyaluronic acid as a versatile platform for fluorescence resonance energy transfer-based glucose sensing Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-17 Minghao Ge, Pengli Bai, Mingli Chen, Jingjing Tian, Jun Hu, Xu Zhi, Huancai Yin, Jian Yin
Here, we utilized the ultrasonic emulsification technique to generate hyaluronic acid microspheres incorporating a fluorescence-based glucose biosensor. We synthesized a novel lanthanide ion luminophore based on Eu3+. Eu sulfosuccinimidyl dextran (Eu-dextran) and Alexa Fluor 647 sulfosuccinimidyl-ConA (Alexa Fluor 647-ConA) were encapsulated in hyaluronic acid hydrogel to generate microspheres. Glucose sensing was carried out using a fluorescence resonance energy transfer (FRET)-based assay principle. A proportional fluorescence intensity increase was found within a 0.5–10-mM glucose concentration range. The glucose-sensing strategy showed an excellent tolerance for potential interferents. Meanwhile, the fluorescent signal of hyaluronic acid microspheres was very stable after testing for 72 h in glucose solution. Overall, hyaluronic acid microspheres encapsulating sensing biomolecules offer a stable and biocompatible biosensor for a variety of applications including cell culture systems, tissue engineering, detection of blood glucose, etc.
Sensitive colorimetric assay for uric acid and glucose detection based on multilayer-modified paper with smartphone as signal readout Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-17 Xu Wang, Fang Li, Ziqi Cai, Kaifan Liu, Jing Li, Boyang Zhang, Jianbo He
In this work, a multilayer-modified paper-based colorimetric sensing platform with improved color uniformity and intensity was developed for the sensitive and selective determination of uric acid and glucose with smartphone as signal readout. In detail, chitosan, different kinds of chromogenic reagents, and horseradish peroxidase (HRP) combined with a specific oxidase, e.g., uricase or glucose oxidase (GOD), were immoblized onto the paper substrate to form a multilayer-modified test paper. Hydrogen peroxide produced by the oxidases (uricase or GOD) reacts with the substrates (uric acid or glucose), and could oxidize the co-immoblized chromogenic reagents to form colored products with HRP as catalyst. A simple strategy by placing the test paper on top of a light-emitting diode lamp was adopted to efficiently prevent influence from the external light. The color images were recorded by the smartphone camera, and then the gray values of the color images were calculated for quantitative analysis. The developed method provided a wide linear response from 0.01 to 1.0 mM for uric acid detection and from 0.02 to 4.0 mM for glucose detection, with a limit of detection (LOD) as low as 0.003 and 0.014 mM, respectively, which was much lower than for previously reported paper-based colorimetric assays. The proposed assays were successfully applied to uric acid and glucose detection in real serum samples. Furthermore, the enhanced analytical performance of the proposed method allowed the non-invasive detection of glucose levels in tear samples, which holds great potential for point-of-care analysis.
Characterization of a novel miniaturized burst-mode infrared laser system for IR-MALDESI mass spectrometry imaging Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-17 Måns Ekelöf, Jeffrey Manni, Milad Nazari, Mark Bokhart, David C. Muddiman
Laser systems are widely used in mass spectrometry as sample probes and ionization sources. Mid-infrared lasers are particularly suitable for analysis of high water content samples such as animal and plant tissues, using water as a resonantly excited sacrificial matrix. Commercially available mid-IR lasers have historically been bulky and expensive due to cooling requirements. This work presents a novel air-cooled miniature mid-IR laser with adjustable burst-mode output and details an evaluation of its performance for mass spectrometry imaging. The miniature laser was found capable of generating sufficient energy for complete ablation of animal tissue in the context of an IR-MALDESI experiment with exogenously added ice matrix, yielding several hundred confident metabolite identifications.
Speciation analysis of arsenic in seafood and seaweed: Part I—evaluation and optimization of methods Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-17 Mesay Mulugeta Wolle, Sean D. Conklin
Several extraction and chromatographic methods were evaluated to identify optimum conditions for arsenic speciation analysis in seafood and seaweed. The extraction systems, which include aqueous, aqueous-organic, acidic, basic, and enzymatic solutions, were examined for their efficiency in extracting arsenic from finfish, crustaceans, molluscs, and seaweed keeping the chemical forms of the native arsenicals intact. While dilute solutions of nitric acid, hydrochloric acid, and tetramethylammonium hydroxide (TMAH) extract high fractions of arsenic from most of the matrices, the extractants oxidized arsenite (As3+) to arsenate (As5+) and converted some arsenosugars and non-polar arsenicals to known and/or unknown forms. Hot water (90 °C) effectively maintained the integrity of the native arsenic species and enabled analysis of the extracts with no further manipulation than filtration and dilution. Stepwise extraction of water-soluble and non-polar arsenic with hot water and a mixture of dichloromethane and methanol, respectively, resulted in sufficiently quantitative (> 75%) arsenic extraction from seafood and seaweed. Anion and cation exchange chromatographic methods were optimized for separation and quantitation of the arsenicals extracted into hot water. The non-polar arsenicals were collectively determined after digesting the extract in acid. The application of the optimum extraction and chromatographic conditions was demonstrated by analyzing certified reference materials of tuna fish tissue (BCR 627), lobster hepatopancreas (TORT-2) and oyster tissue (SRM 1566b), and a sample of hijiki seaweed. For all the matrices, good agreement (80–92%) was found between the total water-soluble arsenic and the sum of the concentrations of the chromatographed species. Limits of quantification (LOQ) were in the range 4–11 ng g−1 for 16 arsenicals.
Molecularly imprinted vs. reversed-phase extraction for the determination of zearalenone: a method development and critical comparison of sample clean-up efficiency achieved in an on-line coupled SPE chromatography system Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-17 Ivona Lhotská, Barbora Gajdošová, Petr Solich, Dalibor Šatínský
Sample preparation prior to chromatographic separation plays an important role in the analytical process. To avoid time-consuming and manual handling sample-prep, automated on-line techniques such as on-line SPE-HPLC are therefore preferred. In this study, two different on-line extraction approaches for mycotoxin/endocrine disruptor zearalenone (ZEA) determination using either molecularly imprinted polymer (MIP) with selective cavities and binding sites for extraction or a reversed-phase sorbent C18 providing non-selective interactions have been developed, validated, and compared. The validation characteristics were compared and the two methods were evaluated as being almost equal in terms of linearity, repeatability, precision, and recovery. Recoveries were in the range of 99.0–100.1% and limits of detection were found the same for both methods (1.5 μg L−1). Method precision calculated for spiked beer samples was better for C18 sorbent (2.5 vs. 5.4% RSD). No significant differences in the selectivity of either extraction method were observed. The possible reasons and further details associated with this finding are discussed. Finally, both validated methods were applied for the determination of ZEA contamination in beer samples. Due to ZEA’s native fluorescence, chromatographic separation with fluorimetric detection (λex = 270 nm and λem, = 458 nm) was selected.
A novel integrated strategy for the detection and quantification of the neurotoxin β- N -methylamino- l -alanine in environmental samples Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-17 Joshua Beri, Kaylie I. Kirkwood, David C. Muddiman, Michael S. Bereman
We describe a set of new tools for the detection and quantification of β-N-methylamino-l-alanine (BMAA) which includes a novel stable isotope-labeled BMAA standard (13C3,15N2) and a chip-based capillary electrophoresis mass spectrometry platform for separation and detection. Baseline resolution of BMAA from its potentially confounding structural isomers N-2-aminoethylglycine (AEG) and 2,4-diaminobutyric acid (2,4-DAB) is achieved using the chip-based CE-MS system in less than 1 min. Detection and linearity of response are demonstrated across > 3.5 orders of dynamic range using parallel reaction monitoring (PRM). The lower limit of detection and quantification were calculated for BMAA detection at 40 nM (4.8 ng/mL) and 400 nM (48 ng/mL), respectively. Finally, the strategy was applied to detect BMAA in seafood samples purchased at a local market in Raleigh, NC where their harvest location was known. BMAA was detected in a sea scallop sample. Because the BMAA/stable isotope-labeled 13C3,15N2-BMAA (SIL-BMAA) ratio in the scallop sample was below the limit of quantification, a semiquantitative analysis of BMAA content was carried out, and BMAA content was estimated to be approximately 820 ng BMAA/1 g of wet scallop tissue. Identification was verified by high mass measurement accuracy of precursor (< 5 ppm) and product ions (< 10 ppm), comigration with SIL-BMAA spike-in standard, and conservation of ion abundance ratios for product ions between BMAA and SIL-BMAA. Interestingly, BMAA was not identified in the free protein fraction but only detected after protein hydrolysis which suggests that BMAA is tightly bound by and/or incorporated into proteins.
Prediction of biotransformation products of the fungicide fluopyram by electrochemistry coupled online to liquid chromatography-mass spectrometry and comparison with in vitro microsomal assays Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-17 Tessema F. Mekonnen, Ulrich Panne, Matthias Koch
Biotransformation processes of fluopyram (FLP), a new succinate dehydrogenase inhibitor (SDHI) fungicide, were investigated by electrochemistry (EC) coupled online to liquid chromatography (LC) and electrospray mass spectrometry (ESI-MS). Oxidative phase I metabolite production was achieved using an electrochemical flow-through cell equipped with a boron-doped diamond (BDD) electrode. Structural elucidation and prediction of oxidative metabolism pathways were assured by retention time, isotopic patterns, fragmentation, and accurate mass measurements using EC/LC/MS, LC-MS/MS, and/or high-resolution mass spectrometry (HRMS). The results obtained by EC were compared with conventional in vitro studies by incubating FLP with rat and human liver microsomes (RLM, HLM). Known phase I metabolites of FLP (benzamide, benzoic acid, 7-hydroxyl, 8-hydroxyl, 7,8-dihydroxyl FLP, lactam FLP, pyridyl acetic acid, and Z/E-olefin FLP) were successfully simulated by EC/LC/MS. New metabolites including an imide, hydroxyl lactam, and 7-hydroxyl pyridyl acetic acid oxidative metabolites were predicted for the first time in our study using EC/LC/MS and liver microsomes. We found oxidation by dechlorination to be one of the major metabolism mechanisms of FLP. Thus, our results revealed that EC/LC/MS-based metabolic elucidation was more advantageous on time and cost of analysis and enabled matrix-free detection with valuable information about the mechanisms and intermediates of metabolism processes.
Correction to: Volumetric absorptive microsampling as an alternative tool for therapeutic drug monitoring of first-generation anti-epileptic drugs Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-15 Sofie Velghe, Christophe P. Stove
Abstract We would like to call the reader’s attention to the fact that unfortunately in fig. 2 of the original article the figure headings of both graphs are the same.
Analytical challenges in sports drug testing Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-14 Mario Thevis, Oliver Krug, Hans Geyer, Katja Walpurgis, Norbert Baume, Andreas Thomas
Analytical chemistry represents a central aspect of doping controls. Routine sports drug testing approaches are primarily designed to address the question whether a prohibited substance is present in a doping control sample and whether prohibited methods (for example, blood transfusion or sample manipulation) have been conducted by an athlete. As some athletes have availed themselves of the substantial breadth of research and development in the pharmaceutical arena, proactive and preventive measures are required such as the early implementation of new drug candidates and corresponding metabolites into routine doping control assays, even though these drug candidates are to date not approved for human use. Beyond this, analytical data are also cornerstones of investigations into atypical or adverse analytical findings, where the overall picture provides ample reason for follow-up studies. Such studies have been of most diverse nature, and tailored approaches have been required to probe hypotheses and scenarios reported by the involved parties concerning the plausibility and consistency of statements and (analytical) facts. In order to outline the variety of challenges that doping control laboratories are facing besides providing optimal detection capabilities and analytical comprehensiveness, selected case vignettes involving the follow-up of unconventional adverse analytical findings, urine sample manipulation, drug/food contamination issues, and unexpected biotransformation reactions are thematized.
The combination of 2,5-dihydroxybenzoic acid and 2,5-dihydroxyacetophenone matrices for unequivocal assignment of phosphatidylethanolamine species in complex mixtures Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-14 Jenny Schröter, Annabelle Fülöp, Carsten Hopf, Jürgen Schiller
Unequivocal assignment of phospholipid peaks in complex mixtures is difficult if only the m/z values but no tandem mass spectrometry (MS/MS) data are available. This is usually the case for matrix-assisted laser/desorption ionization time-of-flight (MALDI-TOF) MS imaging experiments and the analysis has normally to be performed without prior separation. Another problem might be the often matrix-induced loss of one methyl group in phosphatidylcholine (PC) species, which makes them detectable as negative ions becoming isomers of some phosphatidylethanolamines (PEs). Selected lipid mixtures of known compositions were investigated by negative ion MALDI-TOF MS and various imaging experiments. In addition to common matrices such as 2,5-dihydroxybenzoic acid (DHB) and 9-aminoacridine (9-AA), different binary matrices, including 2,5-dihydroxyacetophenone (2,5-DHAP) as matrix additive to DHB, were tested to probe their performance in both ionization modes. Beside artificial PC and PE mixtures of known compositions, egg yolk and liver extracts as well as cryosections from liver and pancreas tissue were selected as biologically relevant systems. The majority of the binary MALDI matrices used here leads to the loss of a methyl group from PC in the negative ion mode, which makes the clear identification of PE species ambiguous. However, this problem does not apply if a mixture of DHB and 2,5-DHAP is used. Therefore, the application of DHB/2,5-DHAP as matrix is a simple method to unequivocally identify PEs even in complex mixtures and tissue sections as negative ions and without the necessity to separate the individual lipid classes prior to MS detection.
Functionalized Au@Ag-Au nanoparticles as an optical and SERS dual probe for lateral flow sensing Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-14 Tingting Bai, Meng Wang, Min Cao, Juan Zhang, Kangzhen Zhang, Ping Zhou, Zhengxia Liu, Ying Liu, Zhirui Guo, Xiang Lu
Lateral flow assay strips (LFASs) with Au nanoparticles (NPs) have been widely used as a probe for biomarkers in point-of-care testing; however, there still remain challenges in detection sensitivity and quantitative analysis. In this study, we developed a surface-enhanced Raman scattering (SERS)-based LFAS for quantitative analysis of a biomarker in the low concentration range. Moreover, apart from conventional Au NPs, three other types of citrate-capped Au-Ag bimetallic NPs: Au core with Ag shell NPs (Au@Ag NPs), rattle-like Au core in Ag-Au shell NPs (Au@Ag-Au NPs) and Ag-Au NPs were prepared and functionalized, and their solution-based SERS activities were comprehensively studied by experimental measurement and theoretical analysis. The results clearly indicated that the citrate-capped Au@Ag-Au NPs exhibited the highest SERS activity among the probes tested. Au@Ag-Au NPs were used as both optical and SERS probes in a SERS-based LFAS. In the presence of the analyte at high concentrations, a purple color appeared in the test zone. Highly sensitive and quantitative analysis was realized by measurement of SERS signals from the test lines. One of the most specific markers for cardiac injury, cardiac troponin I (cTnI), was chosen as the detection model. The detection limit of the SERS-based LFAS for cardiac troponin I was 0.09 ng/mL, lowered by nearly 50 times compared with visual results, and could be further lowered by optimization. These results demonstrated that the SERS-based LFAS using citrate-capped Au@Ag-Au NPs as probes can be a powerful tool for highly sensitive and quantitative detection of biomarkers.
Application and evaluation of a high-resolution mass spectrometry screening method for veterinary drug residues in incurred fish and imported aquaculture samples Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-14 Sherri B. Turnipseed, Joseph M. Storey, I-Lin Wu, Charles M. Gieseker, Nicholas R. Hasbrouck, Tina C. Crosby, Wendy C. Andersen, Shanae Lanier, Christine R. Casey, Robert Burger, Mark R. Madson
The ability to detect chemical contaminants, including veterinary drug residues in animal products such as fish, is an important example of food safety analysis. In this paper, a liquid chromatography high-resolution mass spectrometry (LC-HRMS) screening method using a quadrupole-Orbitrap instrument was applied to the analysis of veterinary drug residues in incurred tissues from aquacultured channel catfish, rainbow trout, and Atlantic salmon and imported aquacultured products including European eel, yellow croaker, and tilapia. Compared to traditional MS methods, the use of HRMS with nontargeted data acquisition and exact mass measurement capability greatly increased the scope of compounds that could be monitored simultaneously. The fish samples were prepared for analysis using a simple efficient procedure that consisted of an acidic acetonitrile extraction followed by solid phase extraction cleanup. Two different HRMS acquisition programs were used to analyze the fish extracts. This method detected and identified veterinary drugs including quinolones, fluoroquinolones, avermectins, dyes, and aminopenicillins at residue levels in fish that had been dosed with those compounds. A metabolite of amoxicillin, amoxicillin diketone, was also found at high levels in catfish, trout, and salmon. The method was also used to characterize drug residues in imported fish. In addition to confirming findings of fluoroquinolone and sulfonamide residues that were found by traditional targeted MS methods, several new compounds including 2-amino mebendazole in eel and ofloxacin in croaker were detected and identified.
Correction to: Analysis of bronopol (2-bromo-2-nitropropan-1,3-diol) residues in rice ( Oryza sativa L.) by SPE using Bond Elut Plexa and liquid chromatography-tandem mass spectrometry Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-13 Shuang-shuang Chai, Mei-ling Qin, You-ning Ma, Huan-huan Gao, Qiao He, Han-tong Zhang
Abstract The authors would like to call the reader’s attention to the fact that unfortunately during a recent cross-check of the experimental record, they found that the positions of intercept and slope were reversed in Table 1 in the original manuscript. The authors apologize for the mistake.
Quantitative structure –retention relationship modeling of selected antipsychotics and their impurities in green liquid chromatography using cyclodextrin mobile phases Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-13 Nevena Maljurić, Jelena Golubović, Biljana Otašević, Mira Zečević, Ana Protić
Applying green chromatography methods is currently one of the challenges in liquid chromatography. Among different strategies, using cyclodextrin (CD) mobile phase modifiers was applied in this paper. CDs can form inclusion complexes with a wide variety of hydrophobic organic compounds and, consequently, affect their retention behavior. CD-containing mobile phases possess complicated complexation and adsorption equilibria so retention is dependent not only on chromatographic parameters and properties of the compound but also on properties of compound–CD complex. Docking study was used to calculate association constants of the selected antipsychotics (risperidone, olanzapine, and their impurities) and β–CD complexes and predict which part of the molecule structure will most likely incorporate into the β–CD cavity. Quantitative structure-retention relationship model (QSRR) for selected model substances was built employing artificial neural network (ANN) technique. Reliable QSRR model was obtained using molecular descriptors, complex association constants, and chromatographic factors. The multilayer perceptron network with 11-8-1 topology, trained with back propagation algorithm, showed the best performance. Root mean square error for training, validation, and test was 0.2954, 0.3633, and 0.4864, respectively. The correlation coefficient (R2) between experimentally obtained retention factor values [k(exp)] and values computed or predicted by ANN [k(ANN)] was 0.9962 for training, 0.9927 for validation, and 0.9829 for test, indicating good predictive ability of the model. The optimized network was used for development of green chromatography method for separation of risperidone and its related impurities, as well as olanzapine and its related impurities in a relatively short run time and with low consumption of organic modifier. The developed methods were validated in accordance with ICH Q2 (R1) quideline and all parameters fulfilled the defined criteria. The greenness of the proposed methods has also been demonstrated.
In house validation of a high resolution mass spectrometry Orbitrap-based method for multiple allergen detection in a processed model food Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-13 Rosa Pilolli, Elisabetta De Angelis, Linda Monaci
In recent years, mass spectrometry (MS) has been establishing its role in the development of analytical methods for multiple allergen detection, but most analyses are being carried out on low-resolution mass spectrometers such as triple quadrupole or ion traps. In this investigation, performance provided by a high resolution (HR) hybrid quadrupole-Orbitrap™ MS platform for the multiple allergens detection in processed food matrix is presented. In particular, three different acquisition modes were compared: full-MS, targeted-selected ion monitoring with data-dependent fragmentation (t-SIM/dd2), and parallel reaction monitoring. In order to challenge the HR-MS platform, the sample preparation was kept as simple as possible, limited to a 30-min ultrasound-aided protein extraction followed by clean-up with disposable size exclusion cartridges. Selected peptide markers tracing for five allergenic ingredients namely skim milk, whole egg, soy flour, ground hazelnut, and ground peanut were monitored in home-made cookies chosen as model processed matrix. Timed t-SIM/dd2 was found the best choice as a good compromise between sensitivity and accuracy, accomplishing the detection of 17 peptides originating from the five allergens in the same run. The optimized method was validated in-house through the evaluation of matrix and processing effects, recoveries, and precision. The selected quantitative markers for each allergenic ingredient provided quantification of 60–100 μgingred/g allergenic ingredient/matrix in incurred cookies.
Standard Reference Material (SRM) 2378 fatty acids in frozen human serum. Certification of a clinical SRM based on endogenous supplementation of polyunsaturated fatty acids Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-13 Bruce A. Benner, Michele M. Schantz, Carissa D. Powers, Rosemary L. Schleicher, Johanna E. Camara, Katherine E. Sharpless, James H. Yen, Lorna T. Sniegoski
Dietary fatty acids can be both beneficial and detrimental to human health depending on the degree and type of saturation. Healthcare providers and research scientists monitor the fatty acid content of human plasma and serum as an indicator of health status and diet. In addition, both the Centers for Disease Control & Prevention (CDC) and the National Institutes of Health – Office of Dietary Supplements are interested in circulating fatty acids (FAs) because they may be predictive of coronary heart disease. The National Institute of Standards and Technology (NIST) provides a wide variety of reference materials (RMs) and Standard Reference Materials® (SRM®s) including blood, serum, plasma, and urine with values assigned for analytes of clinical interest. NIST SRM 2378 Fatty Acids in Frozen Human Serum was introduced in 2015 to help validate methods used for the analysis of FAs in serum, and consists of three different pools of serum acquired from (1) healthy donors who had taken fish oil dietary supplements (at least 1000 mg per day) for at least one month (level 1 material), (2) healthy donors who had taken flaxseed oil dietary supplements (at least 1000 mg per day) for at least one month (level 2 material), and (3) healthy donors eating “normal” diets who had not taken dietary supplements containing fish or plant oils (level 3 material). The use of dietary supplements by donors provided SRMs with natural endogenous ranges of FAs at concentrations observed in human populations. Results from analyses using two methods at NIST, including one involving a novel microwave-assisted acid hydrolysis procedure, and one at the CDC are presented here. These results and their respective uncertainties were combined to yield certified values with expanded uncertainties for 12 FAs and reference values with expanded uncertainties for an additional 18 FAs.
Ionic liquids as water-compatible GC stationary phases for the analysis of fragrances and essential oils Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-13 Cecilia Cagliero, Carlo Bicchi, Chiara Cordero, Erica Liberto, Patrizia Rubiolo, Barbara Sgorbini
Fragrances and products deriving from essential oils are often formulated or diluted in aqueous media, usually ethanol/water. Gas chromatography (GC) is the technique of choice to analyze volatiles. However, when using columns coated with conventional stationary phases, its application to aqueous samples often requires time-consuming and/or discriminative sample preparation techniques to extract the target analytes from the aqueous medium, so as to avoid its direct injection. In GC with conventional columns, water produces peak asymmetry, poor sensitivity and efficiency, strong adsorption, stationary phase degradation, and, last but not least, it is not easy to detect reliably when present in high amounts. In 2012, Armstrong’s group introduced new fully water-compatible ionic-liquid (IL)-based GC capillary columns based on phosphonium and imidazolium derivative cations combined with trifluoromethanesulphonate. These columns were recently made available commercially by Supelco, under the trade name Watercol™. These derivatives maintain IL’s unique selectivity and chromatographic properties, and enable water to be used as injection solvent, thus avoiding the sample preparation procedures required by conventional columns. This study reports and critically discusses the results of commercially available water-compatible IL columns for direct analysis of aqueous samples in the fragrance and essential oil fields by GC with thermal conductivity (TCD) and/or flame ionization detectors (FID). The results showed that water-compatible IL-based stationary phases can successfully be adopted for qualitative and quantitative analysis of fragrances and essential oils directly diluted in aqueous solvents. On the other hand, the study also shows that their inertness needs to be further increased and (possibly) the range of operative temperature extended when water is the main solvent of the sample.
A unique arsenic speciation profile in Elaphomyces spp. (“deer truffles”)—trimethylarsine oxide and methylarsonous acid as significant arsenic compounds Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-12 Simone Braeuer, Jan Borovička, Walter Goessler
Arsenic and its species were investigated for the first time in nine collections of Elaphomyces spp. (“deer truffles”) from the Czech Republic with inductively coupled plasma mass spectrometry (ICPMS) and high-performance liquid chromatography coupled to ICPMS. The total arsenic concentrations ranged from 12 to 42 mg kg−1 dry mass in samples of E. asperulus and from 120 to 660 mg kg−1 dry mass in E. granulatus and E. muricatus. These concentrations are remarkably high for terrestrial organisms and demonstrate the arsenic-accumulating ability of these fungi. The dominating arsenic species in all samples was methylarsonic acid which accounted for more than 30% of the extractable arsenic. Arsenobetaine, dimethylarsinic acid, and inorganic arsenic were present as well, but only at trace concentrations. Surprisingly, we found high amounts of trimethylarsine oxide in all samples (0.32–28% of the extractable arsenic). Even more remarkable was that all but two samples contained significant amounts of the highly toxic trivalent arsenic compound methylarsonous acid (0.08–0.73% of the extractable arsenic). This is the first report of the occurrence of trimethylarsine oxide and methylarsonous acid at significant concentrations in a terrestrial organism. Our findings point out that there is still a lot to be understood about the biotransformation pathways of arsenic in the terrestrial environment.
Detection of 1,3-dihydroxyacetone by tris(2,2′-bipyridine)ruthenium(II) electrochemiluminescence Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-12 Jianrui Sun, Wenyue Gao, Liming Qi, Yufeng Song, Pan Hui, Zhongyuan Liu, Guobao Xu
1,3-Dihydroxyacetone, a common cosmetic material and food additive, has been successfully explored as an efficient electrochemiluminescence coreactant of Ru(bpy)32+ for the first time. It is about 25 times more effective than the well-known coreactant sodium oxalate. The high electrochemiluminescence efficiency allows sensitive detection of 1,3-dihydroxyacetone without any derivatization. The electrochemiluminescence method shows two linear electrochemiluminescence responses over the range of 5.0–500 μM and 500 μM–6.0 mM with a detection limit of 1.79 μM. The proposed method is at least two orders of magnitude more sensitive than other reported methods.
Multi-layer solid-phase extraction and evaporation—enrichment methods for polar organic chemicals from aqueous matrices Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-12 Niklas Köke, Daniel Zahn, Thomas P. Knepper, Tobias Frömel
Analysis of polar organic chemicals in the aquatic environment is exacerbated by the lack of suitable and widely applicable enrichment methods. In this work, we assessed the suitability of a novel combination of well-known solid-phase extraction (SPE) materials in one cartridge as well as an evaporation method and for the enrichment of 26 polar model substances (predominantly log D < 0) covering a broad range of physico-chemical properties in three different aqueous matrices. The multi-layer solid-phase extraction (mlSPE) and evaporation method were investigated for the recovery and matrix effects of the model substances and analyzed with hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS). In total, 65% of the model substances were amenable (> 10% recovery) to the mlSPE method with a mean recovery of 76% while 73% of the model substances were enriched with the evaporation method achieving a mean recovery of 78%. Target and non-target screening comparison of both methods with a frequently used reversed-phase SPE method utilizing “hydrophilic and lipophilic balanced” (HLB) material was performed. Target analysis showed that the mlSPE and evaporation method have pronounced advantages over the HLB method since the HLB material retained only 30% of the model substances. Non-target screening of a ground water sample with the investigated enrichment methods showed that the median retention time of all detected features on a HILIC system decreased in the order mlSPE (3641 features, median tR 9.7 min), evaporation (1391, 9.3 min), HLB (4414, 7.2 min), indicating a higher potential of the described methods to enrich polar analytes from water compared with HLB-SPE.
Advances in the analysis of biological samples using ionic liquids Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-12 Kevin D. Clark, María J. Trujillo-Rodríguez, Jared L. Anderson
Ionic liquids are a class of solvents and materials that hold great promise in bioanalytical chemistry. Task-specific ionic liquids have recently been designed for the selective extraction, separation, and detection of proteins, peptides, nucleic acids, and other physiologically relevant analytes from complex biological samples. To facilitate rapid bioanalysis, ionic liquids have been integrated in miniaturized and automated procedures. Bioanalytical separations have also benefited from the modification of nonspecific magnetic materials with ionic liquids or the implementation of ionic liquids with inherent magnetic properties. Furthermore, the direct detection of the extracted molecules in the analytical instrument has been demonstrated with structurally tuned ionic liquids and magnetic ionic liquids, providing a significant advantage in the analysis of low-abundance analytes. This article gives an overview of these advances that involve the application of ionic liquids and derivatives in bioanalysis.
The NISTmAb Reference Material 8671 lifecycle management and quality plan Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-12 John E. Schiel, Abigail Turner
Comprehensive analysis of monoclonal antibody therapeutics involves an ever expanding cadre of technologies. Lifecycle-appropriate application of current and emerging techniques requires rigorous testing followed by discussion between industry and regulators in a pre-competitive space, an effort that may be facilitated by a widely available test metric. Biopharmaceutical quality materials, however, are often difficult to access and/or are protected by intellectual property rights. The NISTmAb, humanized IgG1κ Reference Material 8671 (RM 8671), has been established with the intent of filling that void. The NISTmAb embodies the quality and characteristics of a typical biopharmaceutical product, is widely available to the biopharmaceutical community, and is an open innovation tool for development and dissemination of results. The NISTmAb lifecyle management plan described herein provides a hierarchical strategy for maintenance of quality over time through rigorous method qualification detailed in additional submissions in the current publication series. The NISTmAb RM 8671 is a representative monoclonal antibody material and provides a means to continually evaluate current best practices, promote innovative approaches, and inform regulatory paradigms as technology advances.
Chemometrics-assisted microfluidic paper-based analytical device for the determination of uric acid by silver nanoparticle plasmon resonance Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-12 Vahid Hamedpour, Geert J. Postma, Edwin van den Heuvel, Jeroen J. Jansen, Koji Suzuki, Daniel Citterio
This manuscript reports on the application of chemometric methods for the development of an optimized microfluidic paper-based analytical device (μPAD). As an example, we applied chemometric methods for both device optimization and data processing of results of a colorimetric uric acid assay. Box–Behnken designs (BBD) were utilized for the optimization of the device geometry and the amount of thermal inkjet-deposited assay reagents, which affect the assay performance. Measurement outliers were detected in real time by partial least squares discriminant analysis (PLS-DA) of scanned images. The colorimetric assay mechanism is based on the on-device formation of silver nanoparticles (AgNPs) through the interaction of uric acid, ammonia, and poly(vinyl alcohol) with silver ions under mild basic conditions. The yellow color originating from visible light absorption by localized surface plasmon resonance of AgNPs can be detected by the naked eye or, more quantitatively, with a simple flat-bed scanner. Under optimized conditions, the linearity of the calibration curve ranges from 0.1–5 × 10−3 mol L−1 of uric acid with a limit of detection of 33.9 × 10−6 mol L−1 and a relative standard of deviation 4.5% (n = 3 for determination of 5.0 × 10−3 mol L−1 uric acid).
Inexpensive, effective novel activated carbon fibers for sample cleanup: application to multipesticide residue analysis in food commodities using a QuEChERS method Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-12 Shiv Singh, Anshuman Srivastava, Sheelendra Pratap Singh
Phenolic resin based activated carbon fibers (ACFs) were applied for the first time as a reversed-dispersive solid-phase extraction (r-DSPE) sorbent. A modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was applied to determine 26 pesticides (organophosphates, organochlorines, synthetic pyrethroids, and herbicides) in different complex matrices, including cauliflower, cucumber, banana, apple, wheat, and black gram. Different physicochemical characterization techniques were used to investigate the engineering and structural properties of the r-DSPE sorbent. All the chromatographic analyses were performed with a gas chromatograph equipped with an electron capture detector. The recoveries of all 26 pesticides were acceptable (70–120%), with relative standard deviations of less than 15%. The limit of detection and the limit of quantification were 1.13–5.48 ng/g and 3.42–16.60 ng/g, respectively. In the original QuEChERS method, primary secondary amine is extensively used as the r-DSPE sorbent in the cleanup process, but it is eightfold more expensive than the ACFs used in this study. Therefore, the modified QuEChERS method using ACFs during the cleanup process is more efficient, cheaper, and more robust to determine pesticides from different types of matrices, including vegetables, grains, and fruits, and ACFs could be used as a cost-effective alternative to primary secondary amine.
Fluorescent MUA-stabilized Au nanoclusters for sensitive and selective detection of penicillamine Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-10 Huan Yu, Xinfeng Chen, Long Yu, Mingtai Sun, Khalid A. Alamry, Abdullah M. Asiri, Kui Zhang, Juan Antonio Zapien, Suhua Wang
In this study, we have developed a facile method for preparation of highly fluorescent Au nanoclusters (AuNCs) using 11-mercaptoundecanoic acid (MUA) as both the reducing and stabilizing agent. The as-prepared MUA functionalized AuNCs (MUA-AuNCs) have good water solubility, excellent photostability, and strong fluorescence emission at 610 nm with a quantum yield of 7.28% in water. The fluorescence of MUA-AuNCs was first quenched by copper ions through electron transfer, subsequently caused obvious restoration by competitive effect after adding penicillamine, making it a potential fluorescent sensor for penicillamine with a detection limit of 0.08 μM. Furthermore, the newly designed fluorescence “on-off-on” assay was explored for the measurement of penicillamine in complex real water and urine samples with satisfactory results.
Determination of oligomers in virgin and recycled polyethylene terephthalate (PET) samples by UPLC-MS-QTOF Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-10 Sara Ubeda, Margarita Aznar, Cristina Nerín
An oligomer is a molecule that consists of a few monomer units. It can be formed during polymer manufacturing and also due to polymer degradation processes or even during use conditions. Since oligomers are not included in chemical databases, their identification is a complex process. In this work, the oligomers present in 20 different PET pellet samples have been determined. Two different sample treatment procedures, solvent extraction and total dissolution, were applied in order to select the most efficient one. The analyses were carried out by UPLC-MS-QTOF. The use of high resolution mass spectrometry allowed the structural elucidation of these compounds and their correct identification. The main oligomers identified were cyclic as well as lineal from the first, second, and third series. All of them were composed of terephthalic acid (TPA), diethylene glycol (DEG), and ethylene glycol (EG). Quantitative values were very different in both procedures. In total dissolution of PET samples, the concentration of oligomers was always, at least, 10 times higher than in solvent extraction; some of the compounds were only detected when total dissolution was used. Results showed that the oligomers with the highest concentration values were dimers and trimers, cyclic, as well as lineal, from the first and second series. The oligomer with the maximum concentration value was TPA2-EG-DEG that was found in all the samples in a concentration range from 2493 to 19,290 ng/g PET. No differences between virgin and recycled PET were found. Migration experiments were performed in two PET bottles, and results showed the transference of most of these oligomers to a fat food simulant (ethanol 95%).
High-performance liquid chromatography for the analytical characterization of anthocyanins in Vaccinium myrtillus L. (bilberry) fruit and food products Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-10 Stefania Benvenuti, Virginia Brighenti, Federica Pellati
Anthocyanins represent the most abundant class of bioactive compounds present in Vaccinium myrtillus L. (bilberry) fruit, conferring it several health-promoting properties. The content of anthocyanins in food products produced from bilberries can be affected by many parameters, making the study of their composition a critical issue. In this ambit, this work was aimed at a comprehensive profiling of anthocyanins in bilberry fruit and derivatives from the Italian Northern Apennines, including jam, juice, and liqueur (“Mirtillino”). Anthocyanins were extracted from the jams by means of a dynamic maceration with acidified methanol, while juice and liqueurs were directly analyzed. The analysis of anthocyanins in the extracts was carried out by means of HPLC-UV/DAD, HPLC-ESI-MS, and MS2, under gradient elution. As a comparison, authentic bilberry fruits were analyzed. The total anthocyanin content was in the range 582.4–795.2 mg/100 g (FW) for the fruit, 2.3–234.5 mg/100 g for the jams, 109.2–2252.2 mg/L for the juice, and 27.9–759.3 mg/L for the liqueurs. To deeper investigate the anthocyanin profile of the liqueurs that exhibited a remarkably different composition in comparison with the other products, an authentic bilberry liqueur was prepared in the lab, following a traditional recipe, and monitored weakly by HPLC. The percentage of degradation of 3-O-galactosides and 3-O-arabinosides of bilberry anthocyanidins was found to be higher than that of 3-O-glucosides. The results of this work demonstrated the importance of a suitable and reliable analysis of bilberry fruit and related food products to ensure their genuineness and quality.
Sensitive analysis of N-blocked amino acids using high-performance liquid chromatography with paired ion electrospray ionization mass spectrometry Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-10 Yadi Wang, Siqi Du, Daniel W. Armstrong
In this study, a paired ion electrospray ionization (PIESI) mass spectrometry method was developed for sensitive detection of 9-fluorenylmethyl chloroformate (Fmoc)-derivatized amino acids. The structure-optimized ion-pairing reagent was introduced post column to form positively charged complexes which can be detected in the positive ion mode. These complexes are more surface-active than the original analytes, and meanwhile, the intensity of sodium adducts was significantly reduced. The limit of detection of the amino acids obtained with the optimal ion-pairing reagent was 0.5 to 20 pg which was 5–100 times lower than the negative mode. In addition, two mass spectrometry platforms—linear ion trap and triple quadrupole—were used to compare the PIESI improvements. Eventually, the method was applied to successfully detect the level of amino acids in human urine samples with high accuracy and the added benefit of minimizing matrix effects.
Development of orthogonal NISTmAb size heterogeneity control methods Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-10 Abigail Turner, Katharina Yandrofski, Srivalli Telikepalli, Jason King, Alan Heckert, James Filliben, Dean Ripple, John E. Schiel
The NISTmAb is a monoclonal antibody Reference Material from the National Institute of Standards and Technology; it is a class-representative IgG1κ intended to serve as a pre-competitive platform for harmonization and technology development in the biopharmaceutical industry. The publication series of which this paper is a part describes NIST’s overall control strategy to ensure NISTmAb quality and availability over its lifecycle. In this paper, the development of a control strategy for monitoring NISTmAb size heterogeneity is described. Optimization and qualification of size heterogeneity measurement spanning a broad size range are described, including capillary electrophoresis-sodium dodecyl sulfate (CE-SDS), size exclusion chromatography (SEC), dynamic light scattering (DLS), and flow imaging analysis. This paper is intended to provide relevant details of NIST’s size heterogeneity control strategy to facilitate implementation of the NISTmAb as a test molecule in the end user’s laboratory.
The 2017 Nobel Prize in Chemistry: cryo-EM comes of age Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-09 Peter S. Shen
The 2017 Nobel Prize in Chemistry was awarded to Jacques Dubochet, Joachim Frank, and Richard Henderson for “developing cryo-electron microscopy (cryo-EM) for the high-resolution structure determination of biomolecules in solution.” This feature article summarizes some of the major achievements leading to the development of cryo-EM and recent technological breakthroughs that have transformed the method into a mainstream tool for structure determination.
Qualification of NISTmAb charge heterogeneity control assays Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-09 Abigail Turner, John E. Schiel
The NISTmAb is a monoclonal antibody Reference Material from the National Institute of Standards and Technology; it is a class-representative IgG1κ intended serve as a pre-competitive platform for harmonization and technology development in the biopharmaceutical industry. The publication series of which this paper is a part describes NIST’s overall control strategy to ensure NISTmAb quality and availability over its lifecycle. In this paper, the development and qualification of methods for monitoring NISTmAb charge heterogeneity are described. Capillary zone electrophoresis (CZE) and capillary isoelectric focusing (CIEF) assays were optimized and evaluated as candidate assays for NISTmAb quality control. CIEF was found to be suitable as a structural characterization assay yielding information on the apparent pI of the NISTmAb. CZE was found to be better suited for routine monitoring of NISTmAb charge heterogeneity and was qualified for this purpose. This paper is intended to provide relevant details of NIST’s charge heterogeneity control strategy to facilitate implementation of the NISTmAb as a test molecule in the end user’s laboratory.
Characterization of the NISTmAb Reference Material using small-angle scattering and molecular simulation Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-09 Maria Monica Castellanos, Steven C. Howell, D. Travis Gallagher, Joseph E. Curtis
Both conformational and colloidal stability of therapeutic proteins must be closely monitored and thoroughly characterized to assess the long-term viability of drug products. We characterized the IgG1 NISTmAb reference material in its histidine formulation buffer and report our findings on the higher order structure and interactions of NISTmAb under a range of conditions. In this paper we present the analysis of experimental small-angle scattering data with atomistic molecular simulations to characterize the monodisperse dilute solution of NISTmAb. In part II we describe the characterization of the NISTmAb at high protein concentration (Castellanos et al. 2018). The NISTmAb was found to be a flexible protein with a radius of gyration of 49.0 ± 1.2 Å in histidine formulation buffer using a variety of neutron and X-ray scattering measurements. Scattering data were then modeled using molecular simulation. After building and validating a starting NISTmAb structure from the Fc and Fab crystallographic coordinates, molecular dynamics and torsion-angle Monte Carlo simulations were performed to explore the configuration space sampled in the NISTmAb and obtain ensembles of structures with atomistic detail that are consistent with the experimental data. Our results indicate that the small-angle scattering profiles of the NISTmAb can be modeled using ensembles of flexible structures that explore a wide configuration space. The NISTmAb is flexible in solution with no single preferred orientation of Fc and Fab domains, but with some regions of configuration space that are more consistent with measured scattering profiles. Analysis of inter-domain atomistic contacts indicated that all ensembles contained configurations where residues between domains are ≤ 4 Å, although few contacts were observed for variable and C H 3 regions.
Establishment of pressurized-liquid extraction by response surface methodology approach coupled to HPLC-DAD-TOF-MS for the determination of phenolic compounds of myrtle leaves Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-09 Elixabet Díaz-de-Cerio, David Arráez-Román, Antonio Segura-Carretero, Pasquale Ferranti, Rosario Nicoletti, Giuseppe Mirko Perrotta, Ana María Gómez-Caravaca
Myrtus communis L. (myrtle) is native to the Mediterranean region and Western Asia. Its leaves have demonstrated its potential effect towards different bioactivities like anti-diabetic, anti-diarrheic, anti-ulcer, anti-cancer, among others. These activities have been associated with its phenolic content. In this sense, the aim of this work has been to develop a new pressurized-liquid extraction procedure (PLE), by using a response surface methodology (RSM), to evaluate the phenolic composition from myrtle leaves by HPLC-DAD-TOF-MS. Previously, different solvents such as methanol, ethanol, and acetone/water mixtures were tested by using ultrasound-assisted extraction (UAE) in order to select the most suitable one. Subsequently, a Box-Behnken design (BBD) was performed according to the effect of ethanol/water ratio (50, 75, and 100% (v/v)), temperature (50, 125, and 200 °C), and extraction time (5, 18, and 30 min). The optimal conditions achieved with the established method were 71% ethanol/water, 137 °C, and 19 min. The analysis of the obtained extracts by HPLC-DAD-TOF-MS allowed the characterization of 15 new compounds in myrtle leaves. Finally, high amounts of gallic and ellagic acid were found in the optimized PLE extracts (3.31 ± 0.03 and 3.88 ± 0.09 mg/g leaf dry weight (d.w.), respectively), and PLE reported greater recovery of total phenolic compounds than UAE (30 ± 1 and 22.4 ± 0.6 mg/g leaf d.w., respectively).
Characterization of the NISTmAb Reference Material using small-angle scattering and molecular simulation Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-08 Maria Monica Castellanos, Kevin Mattison, Susan Krueger, Joseph E. Curtis
Protein-protein interactions in monoclonal antibody solutions are important for the stability of a therapeutic drug and directly influence viscosity in concentrated protein solutions. This study describes the use of small-angle scattering to estimate protein-protein interactions at high concentrations of the IgG1 NISTmAb reference material and validate colloidal models for interacting molecules. In particular, we studied the colloidal stability of the NISTmAb at high protein concentrations and analyzed protein-protein interactions upon adding sodium chloride and its effect on viscosity. Isotropic colloidal models for interacting molecules were combined with an ensemble of atomistic structures from molecular simulation to account for the flexibility of the NISTmAb in solution. In histidine formulation buffer, net repulsive electrostatic interactions are important for the colloidal stability of the NISTmAb at high concentrations. Addition of sodium chloride increased the viscosity of the NISTmAb and decreased the colloidal stability due to charge screening of the repulsive interactions. The interactions at high concentrations (up to ~ 250 mg/mL) were consistent with those from light scattering at low concentrations (below ~ 20 mg/mL). However, in the presence of sodium chloride, the screening of charges was less pronounced with increasing protein concentration and the interactions approached those of the repulsive hard-sphere models. Additionally, we studied the NISTmAb under frozen conditions using in situ neutron scattering to analyze the crowded state as proteins are excluded from the water-rich phase. In the frozen samples, where protein concentration can reach hundreds of mg/mL in the protein-rich phase, sodium chloride did not affect the molecular spacing and crowding of the NISTmAb.
The NISTmAb Reference Material 8671 value assignment, homogeneity, and stability Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-07 John E. Schiel, Abby Turner, Trina Mouchahoir, Katharina Yandrofski, Srivalli Telikepalli, Jason King, Paul DeRose, Dean Ripple, Karen Phinney
The NISTmAb Reference Material (RM) 8671 is intended to be an industry standard monoclonal antibody for pre-competitive harmonization of best practices and designing next generation characterization technologies for identity, quality, and stability testing. It must therefore embody the quality and characteristics of a typical biopharmaceutical product and be available long-term in a stable format with consistent product quality attributes. A stratified sampling and analysis plan using a series of qualified analytical and biophysical methods is described that assures RM 8671 meets these criteria. Results for the first three lots of RM 8671 highlight the consistency of material attributes with respect to size, charge, and identity. RM 8671 was verified to be homogeneous both within and between vialing lots, demonstrating the robustness of the lifecycle management plan. It was analyzed in concert with the in-house primary sample 8670 (PS 8670) to provide a historical link to this seminal material. RM 8671 was verified to be fit for its intended purpose as a technology innovation tool, external system suitability control, and cross-industry harmonization platform.
Development of an LC-MS/MS peptide mapping protocol for the NISTmAb Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-07 Trina Mouchahoir, John E. Schiel
Peptide mapping is a component of the analytical toolbox used within the biopharmaceutical industry to aid in the identity confirmation of a protein therapeutic and to monitor degradative events such as oxidation or deamidation. These methods offer the advantage of providing site-specific information regarding post-translational and chemical modifications that may arise during production, processing or storage. A number of such variations may also be induced by the sample preparation methods themselves which may confound the ability to accurately evaluate the true modification levels. One important focus when developing a peptide mapping method should therefore be the use of sample preparation conditions that will minimize the degree of artificial modifications induced. Unfortunately, the conditions that are amenable to effective reduction, alkylation and digestion are often the same conditions that promote unwanted modifications. Here we describe the optimization of a tryptic digestion protocol used for peptide mapping of the NISTmAb IgG1κ which addresses the challenge of balancing maximum digestion efficiency with minimum artificial modifications. The parameters on which we focused include buffer concentration, digestion time and temperature, as well as the source and type of trypsin (recombinant vs. pancreatic; bovine vs porcine) used. Using the optimized protocol we generated a peptide map of the NISTmAb which allowed us to confirm its identity at the level of primary structure.
Combined analytical approaches to define biodistribution and biological activity of semi-synthetic berberrubine, the active metabolite of natural berberine Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-07 Emanuele Porru, Placido Franco, Donato Calabria, Silvia Spinozzi, Marinella Roberti, Cristiana Caliceti, Aldo Roda
Berberine (BBR) is a natural alkaloid obtained from Berberis species plants, known for its protective effects against several diseases. Among the primary BBR metabolites, berberrubine (M1) showed the highest plasma concentration but few and conflicting data are available regarding its concentration in biological fluids related to its new potential activity on vascular cells. A combined analytical approach was applied to study biodistribution of M1 in comparison with BBR. The optimization of sample clean-up combined with a fully validated HPLC-ESI-MS/MS tailored for M1 allows sufficient detectability and accuracy to be reached in the different studied organs even when administered at low dose, comparable to that assumed by human. A predictive human vascular endothelial cell-based assay to measure intracellular xanthine oxidase has been developed and applied to study unexplored activities of M1 alongside other common activities. Results showed that oral M1 treatment exhibits higher plasma levels than BBR, reaching maximum concentration 400-fold higher than BBR (204 vs 0.5 ng/mL); moreover, M1 exhibits higher concentrations than BBR also in all the biological compartments analyzed. Noteworthy, the two compounds follow two different excretion routes: M1 through urine, while BBR through feces. In vitro studies demonstrated that M1 inhibited intracellular xanthine oxidase activity, one of the major sources of reactive oxygen species in vasculature, with an IC50 = 9.90 ± 0.01 μg/mL and reduced the expression of the inflammatory marker ICAM-1. These peculiar characteristics allow new perspectives to be opened up for the direct use of M1 instead of BBR in endothelial dysfunction treatment.
Paper-based immune-affinity arrays for detection of multiple mycotoxins in cereals Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-06 Li Li, Hongpu Chen, Xiaolan Lv, Min Wang, Xizhi Jiang, Yifei Jiang, Heye Wang, Yongfu Zhao, Liru Xia
Mycotoxins produced by different species of fungi may coexist in cereals and feedstuffs, and could be highly toxic for humans and animals. For quantification of multiple mycotoxins in cereals, we developed a paper-based mycotoxin immune-affinity array. First, paper-based microzone arrays were fabricated by photolithography. Then, monoclonal mycotoxin antibodies were added in a copolymerization reaction with a cross-linker to form an immune-affinity monolith on the paper-based microzone array. With use of a competitive immune-response format, paper-based mycotoxin immune-affinity arrays were successfully applied to detect mycotoxins in samples. The detection limits for deoxynivalenol, zearalenone, T-2 toxin, and HT-2 toxin were 62.7, 10.8, 0.36, and 0.23 μg·kg-1, respectively, which meet relevant requirements for these compounds in food. The recovery rates were 81–86% for deoxynivalenol, 89–117% for zearalenone, 79–86% for T-2 toxin, and 78–83% for HT-2 toxin, and showed the paper-based immune-affinity arrays had good reproducibility. In summary, the paper-based mycotoxin immune-affinity array provides a sensitive, rapid, accurate, stable, and convenient platform for detection of multiple mycotoxins in agro-foods.
Detection of nanoplastics in food by asymmetric flow field-flow fractionation coupled to multi-angle light scattering: possibilities, challenges and analytical limitations Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-06 Manuel Correia, Katrin Loeschner
We tested the suitability of asymmetric flow field-flow fractionation (AF4) coupled to multi-angle light scattering (MALS) for detection of nanoplastics in fish. A homogenized fish sample was spiked with 100 nm polystyrene nanoparticles (PSNPs) (1.3 mg/g fish). Two sample preparation strategies were tested: acid digestion and enzymatic digestion with proteinase K. Both procedures were found suitable for degradation of the organic matrix. However, acid digestion resulted in large PSNPs aggregates/agglomerates (> 1 μm). The presence of large particulates was not observed after enzymatic digestion, and consequently it was chosen as a sample preparation method. The results demonstrated that it was possible to use AF4 for separating the PSNPs from the digested fish and to determine their size by MALS. The PSNPs could be easily detected by following their light scattering (LS) signal with a limit of detection of 52 μg/g fish. The AF4-MALS method could also be exploited for another type of nanoplastics in solution, namely polyethylene (PE). However, it was not possible to detect the PE particles in fish, due to the presence of an elevated LS background. Our results demonstrate that an analytical method developed for a certain type of nanoplastics may not be directly applicable to other types of nanoplastics and may require further adjustment. This work describes for the first time the detection of nanoplastics in a food matrix by AF4-MALS. Despite the current limitations, this is a promising methodology for detecting nanoplastics in food and in experimental studies (e.g., toxicity tests, uptake studies).
Comprehensive targeted and non-targeted lipidomics analyses in failing and non-failing heart Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-06 Ganesh V. Halade, Anela Dorbane, Kevin A. Ingle, Vasundhara Kain, Jean-Marie Schmitter, Boutayna Rhourri-Frih
Myocardial infarction (MI) and subsequent progressive heart failure pathology is the major cause of death worldwide; however, the mechanism of this pathology remains unclear. The present work aimed at testing the hypothesis whether the inflammatory response is superimposed with the formation of bioactive lipid resolving molecules at the site of the injured myocardium in acute heart failure pathology post-MI. In this view, we used a robust permanent coronary ligation model to induce MI, leading to decreased contractility index with marked wall thinning and necrosis of the infarcted left ventricle. Then, we applied mass spectrometry imaging (MSI) in positive and negative ionization modes to characterize the spatial distribution of left ventricle lipids in the infarcted myocardium post-MI. After micro-extraction, liquid chromatography coupled to tandem mass spectrometry was used to confirm the structures of the imaged lipids. Statistical tools such as principal component analysis were used to establish a comprehensive visualization of lipid profile changes in MI and no-MI hearts. Resolving bioactive molecules such as resolvin (Rv) D1, RvD5, RvE3, 17-HDHA, LXA4, and 18-HEPE were detected in negative ion mode MSI, whereas phosphatidyl cholines (PC) and oxidized derivatives thereof were detected in positive ion mode. MSI-based analysis demonstrated a significant increase in resolvin bioactive lipids with comprehensive lipid remodeling at the site of infarction. These results clearly indicate that infarcted myocardium is the primary location of inflammation-resolution pathomechanics which is critical for resolution of inflammation and heart failure pathophysiology.
Use of a quality control approach to assess measurement uncertainty in the comparison of sample processing techniques in the analysis of pesticide residues in fruits and vegetables Anal. Bioanal. Chem. (IF 3.431) Pub Date : 2018-02-06 Steven J. Lehotay, Lijun Han, Yelena Sapozhnikova
In routine monitoring of foods, reduction of analyzed test portion size generally leads to higher sample throughput, less labor, and lower costs of monitoring, but to meet analytical needs, the test portions still need to accurately represent the original bulk samples. With the intent to determine minimal fit-for-purpose sample size, analyses were conducted for up to 93 incurred and added pesticide residues in 10 common fruits and vegetables processed using different sample comminution equipment. The commodities studied consisted of apple, banana, broccoli, celery, grape, green bean, peach, potato, orange, and squash. A Blixer® was used to chop the bulk samples at room temperature, and test portions of 15, 10, 5, 2, and 1 g were taken for analysis (n = 4 each). Additionally, 40 g subsamples (after freezing) were further comminuted using a cryomill device with liquid nitrogen, and test portions of 5, 2, and 1 g were analyzed (n = 4 each). Both low-pressure gas chromatography-tandem mass spectrometry (LPGC-MS/MS) and ultrahigh-performance liquid chromatography (UHPLC)-MS/MS were used for analysis. An empirical approach was followed to isolate and estimate the measurement uncertainty contribution of each step in the overall method by adding quality control spikes prior to each step. Addition of an internal standard during extraction normalized the sample preparation step to 0% error contribution, and coefficients of variation (CVs) were 6–7% for the analytical steps (LC and GC) and 6–9% for the sample processing techniques. In practice, overall CVs averaged 9–11% among the different analytes, commodities, batches, test portion weights, and analytical and sample processing methods. On average, CVs increased up to 4% and bias 8–12% when using 1–2 g test portions vs. 10–15 g.
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