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The measurement of VOSCs in complex matrices is challenging due to their volatile and reactive nature. A straightforward method using headspace chromatography was developed for routine analyses of organosulfur compounds in a high saline liquid matrix with a pH of 8.4. Direct sample acidification with a 1M acetate buffer (pH 3.6) showed an increased response for methanethiol, ethanethiol, propanethiol, dimethyl sulfide, dimethyl disulfide and diethyl disulfide. A good quadratic fit (R2

A comprehensive Collision Cross Section (CCS) library was obtained via Travelling Wave Ion Guide mobility measurements through direct infusion (DI). The library consists of CCS and Mass Spectral (MS) data in negative and positive ElectroSpray Ionisation (ESI) mode for 463 and 479 endogenous metabolites, respectively. For both ionisation modes combined, TWCCSN2 data were obtained for 542 non-redundant metabolites. These data were acquired on two different ion mobility enabled orthogonal acceleration QToF MS systems in two different laboratories, with the majority of the resulting TWCCSN2 values (from detected compounds) found to be within 1% of one another. Validation of these results against two independent, external TWCCSN2 data sources and predicted TWCCSN2 values indicated to be within 1–2% of these other values. The same metabolites were then analysed using a rapid reversed-phase ultra (high) performance liquid chromatographic (U(H)PLC) separation combined with IM and MS (IM-MS) thus providing retention time (tr), m/z and TWCCSN2 values (with the latter compared with the DI-IM-MS data). Analytes for which TWCCSN2 values were obtained by U(H)PLC-IM-MS showed good agreement with the results obtained from DI-IM-MS. The repeatability of the TWCCSN2 values obtained for these metabolites on the different ion mobility QToF systems, using either DI or LC, encouraged the further evaluation of the U(H)PLC-IM-MS approach via the analysis of samples of rat urine, from control and methotrexate-treated animals, in order to assess the potential of the approach for metabolite identification and profiling in metabolic phenotyping studies. Based on the database derived from the standards 63 metabolites were identified in rat urine, using positive ESI, based on the combination of tr, TWCCSN2 and MS data.

[EN] The quantification of the enantiomeric fraction (EF) during the biodegradation process is essential for environmental risk assessment. In this paper the enantioselective biodegradation of ibuprofen, IBU, and ketoprofen, KET, two of the drugs most consumed, was evaluated. Biodegradation experiments were performed in batch mode using a minimal salts medium inoculated with an activated sludge (collected from a Valencian Waste Water Treatment Plant) and supplemented with the racemate of each compound. The inoculum activity was verified using fluoxetine as reference compound. The experimental conditions used (analyte concentration and volume of inoculum) were chosen according to OECD guidelines. In parallel, the optical density at 600 nm was measured to control the biomass growth and to connect it with enantioselectivity. Two RPLC methods for chiral separations of IBU and KET using polysaccharides-based stationary phases were developed. Novel calculations and adapted models, using directly the chromatographic peak areas as dependent variable, were proposed to estimate significant parameters related to the biodegradation process: biodegradation (BD) and EF values at given time, half-life times of (R)- and (S)-enantiomers, number of days to reach a complete BD and the minimum EF expected. The modelled BD and EF curves fitted adequately the data (R-2 > 0.94). The use of these new equations provided similar results to those obtained using concentration data. However, the use of chromatographic peak areas data, eliminates the uncertainty associated to the use of the calibration curves. The results obtained in this paper indicate that an enantiorecognition towards 1BU enantiomers by the microorganisms present in the activated sludge used in this study occurred, being the biodegradation of (R)-IBU higher than that of (S)-IBU. For KET, non-enantioselective biodegradation was observed., The authors acknowledge the Spanish Ministerio de Economia y Competitividad (MINECO) and the European Regional Development Fund (ERDF) for the financial support (Project CTQ2015-70904-R, MINECO/FEDER, UE).

Nitrobenzene, a potentially harmful compound found in tobacco smoke, has been largely excluded from prior analysis due to difficulties with quantification. Quantifying harmful compounds in cigarette smoke is useful to compare products, to examine the impact of design parameters on delivery, and to help estimate exposures. A sensitive high-throughput method has been developed for quantifying nitrobenzene in machine-generated mainstream cigarette smoke using isotope dilution gas chromatography-tandem mass spectrometry (ID-GC-MS/MS). This method has sufficient sensitivity to measure vapor phase nitrobenzene concentrations in the low nanogram range, with a 418 pg/cig method limit of detection. Precision estimates from two quality control cigarette products resulted in percent relative standard deviations of 11.5% and 14.9%; product variability estimates from 13 cigarette products resulted in percent relative standard deviations ranging from 2.8% to 16.9%. Nitrobenzene in the machine-generated, mainstream smoke from 15 cigarette products are reported and range from 18 to 38 ng/cig under the Health Canada Intense smoking regimen.

The size-exclusion separation of a water-soluble polyelectrolyte polymer, sodium polystyrene sulfonate (NaPSS), was demonstrated on common reversed-phase (C(18,) C(4), phenyl, and cyano) and hydrophilic interaction chromatography (HILIC) columns. The effect of common solvents – acetonitrile (ACN), tetrahydrofuran (THF), and methanol (MeOH), used as mobile phase modifiers – on the elution of NaPSS and the effect of column temperature (within a relatively narrow range corresponding to typical chromatographic conditions, i.e., 10 °C–60 °C) on the partition coefficient, K(SEC), were also investigated. Non-size-exclusion chromatography (non-SEC) effects can be minimized by the addition of an electrolyte and an organic modifier to the mobile phase, and by increasing the column temperature (e.g., to 50 °C or 60 °C). Strong solvents such as THF and ACN are more successful in the reduction of such effects than is the weaker solvent MeOH. The best performance is seen on medium polarity and polar stationary phases, such as cyanopropyl- and diol-modified silica (HILIC), where the elution of the NaPSS polyelectrolyte is by a near-ideal SEC mechanism. Hydrophobic stationary phases, such as C(18), C(4), and phenyl, require a higher concentration of a strong solvent modifier (THF) in the mobile phase to reduce non-SEC interactions of the solute with the stationary phase.

Few articles are reported for the simultaneous separation and sensitive detection of the kynurenine pathway (KP) metabolites. This work describes a capillary electrochromatography-mass spectrometry (CEC-MS) method using acrylamido-2-methyl-1-propanesulfonic acid (AMPS) functionalized stationary phase. The AMPS column was prepared by first performing silanization of bare silica with gamma-maps, followed by polymerization with AMPS. The CEC-MS/MS methods were established for six upstream and three downstream KP metabolites. The simultaneous separation of all nine KP metabolites is achieved without derivatization for the first time in the open literature. Numerous parameters such as pH and the concentration of background electrolyte, the concentration of the polymerizable AMPS monomer, column length, field strength, and internal pressure were all tested to optimize the separation of multiple KP metabolites. A baseline separation of six upstream metabolites, namely tryptophan (TRP), kynurenine (KYN), 3-hydroxykynurenine (HKYN), kynurenic acid (KA), anthranilic acid (AA), and xanthurenic acid (XA), was possible at pH 9.25 within 26 min. Separation of six downstream and related metabolites, namely: tryptamine (TRPM), hydroxy‑tryptophan (HTRP), hydroxyindole-3 acetic acid (HIAA), 3-hydroxyanthranilic acid (3-HAA), picolinic acid (PA), and quinolinic acid (QA), was achieved at pH 9.75 in 30 min. However, the challenging simultaneous separation of all nine KP metabolites was only accomplished by increasing the column length and simultaneous application of internal pressure and voltage in 114 min. Quantitation of KP metabolites in commercial human plasma was carried out, and endogenous concentration of five KP metabolites was validated. The experimental limit of quantitation ranges from 100 to 10,000 nM (S/N = 8–832, respectively), whereas the experimental limit of detection ranges from 31 to 1000 nM (S/N = 2–16, respectively). Levels of five major KP metabolites, namely TRP, KYN, KA, AA, and QA, and their ratios in patient plasma samples previously screened for inflammatory biomarkers [C-reactive protein (CRP) and tumor necrosis factor-alpha (TNF-α)] was measured. Pairs of the level of metabolites with significant positive correlation were statistically evaluated.

Traditionally, gas chromatography – mass spectrometry (GC/MS) analysis has used a targeted approach called selected ion monitoring (SIM) to quantify specific compounds that may have adverse health effects. Due to method limitations and the constraints of preparing duplicate samples, the information that could be obtained from separately collecting the full scan chromatogram of the sample has often been sacrificed. However, a hybrid technique called synchronous SIM/scan mode that switches back and forth between the two acquisition methods has become available from equipment manufacturers that maintains the accuracy and sensitivity of SIM for targeted analysis while also providing the full scan chromatogram for discovery of non-target compounds. We have explored the value and performance of this new technology using calibration data and real-world breath samples from a joint EPA/NIOSH collaboration that assessed the safety of firefighters’ protective gear during controlled structural burns. Collecting field samples is costly and must be performed strategically to ensure that time points and replicates are accurate and representative of the intended population. This is especially difficult, if not impossible, to accomplish with firefighters who are working under volatile conditions. The synchronous SIM/scan method decreases the number of field samples that need to be collected by half and reduces error in trying to recreate time points since a breath sample from a single sorbent tube can be used to collect both the SIM and scan data simultaneously. This work demonstrates the performance of the technology using calibration data. As a practical demonstration of the method, we investigate thirty-six firefighter breath samples, document organic compounds of interest, and identify additional non-target compounds.

Three quantification methodologies, namely calibration with internal standard (Cal-IS, non-weighted), weighted calibration with internal standard (wCal-IS) and isotope pattern deconvolution (IPD) have been used for the determination of testosterone in urine by LC-MS/MS. Uncertainty has been calculated and compared for the three methodologies through intra- and inter-laboratory reproducibility assays. IPD showed the best performance for the intra-laboratory reproducibility, with RSD and combined uncertainty values below 4% and 9% respectively. wCal-IS showed similar performance, while Cal-IS where not constant and clearly worse at the lowest concentration assayed (2 ng/mL) reaching RSD values up to 16%. The inter-laboratory assay indicated similar results although wCal-IS RSD (20%) was higher than IPD (10%) and Cal-IS get worse with RSD higher than 40% for the lowest concentration level. Uncertainty budgets calculated for the three procedures revealed that intercept and slope were the most important factors contributing to uncertainty for Cal-IS. The main factors for wCal-IS and IPD were the volumes of sample and/or standard measured. The authors acknowledge financial support from the Generalitat Valenciana (Research group of excellence Prometeo II 2014/023 and Collaborative Research on Environment and Food Safety ISIC/2012/016), as well as University Jaume I for project PB1-1B2013-55. Finally, the authors are grateful to the Serveis Centrals d'Instrumentació Científica (SCIC) of University Jaume I for using Acquity and TQD instruments.

In this work, we present a novel concept for a gas chromatography detector utilizing an atmospheric pressure chemical ionization which is initialized by a dielectric barrier discharge. In general, such a detector can be simple and low-cost, while achieving extremely good limits of detection. However, it is non-selective apart from the use of chemical dopants. Here, a demonstrator manufactured entirely from fused silica capillaries and printed circuit boards is shown. It has a size of 75 × 60 × 25 mm 3 and utilizes only 2W of power in total. Unlike other known discharge detectors, which require high-purity helium, this detector can theoretically be operated using any gas able to form stable ion species. Here, purified air is used. With this setup, limits of detection in the low parts-per-billion range have been obtained for acetone.

International audience; The effect of the polydispersity of polystyrenes on the dispersion through silicas having different morphologies (fully porous, core-shell particles and monoliths) was investigated. The heights equivalent to a theoretical plate (HETP) of those columns were measured for a small molecule (toluene) and a series of polystyrenes of different sizes in non-adsorbing conditions. The different contributions to the total HETP including polydispersity were determined experimentally. The longitudinal diffusion and the mass transfer resistance term were obtained from peak parking experiments. The eddy dispersion was obtained from models and experiments. The effect of polydispersity on the HETP values (Hpoly) can thus be calculated from the total HETP by substraction of the other contributions. The results were compared to the Knox model which surestimates the Hpoly values for porous and core-shell particles which is usually explained by an overestimation of the polydispersity index (PDI) given by the manufacturer. The PDI of two polymers (P02, Mw= 690 g.mol−1 and P03, Mw=1380 g.mol−1) was verified by liquid chromatography by separating each fraction of the polymer on the silica columns by using adsorbing conditions which are obtained with a mixture of heptane and THF. The PDI obtained are comparable to the PDI given by the manufacturer meaning that the assumptions made by Knox are not entirely valid. A direct method is proposed in this paper in order to determine Hpoly. In this method the excess of spreading as compared with a polymer with only one size corresponding to the average size is studied assuming the polymer size distribution is gaussian. The Hpoly values obtained by the direct method are comparable to the experimental values.

To evaluate the endocannabinoid system in an animal model of Parkinson's disease, in-tube solid-phase microextraction (in-tube SPME) was directly coupled to a tandem mass spectrometry (MS/MS) system for determination of the endocannabinoids anandamide (AEA) and 2-arachidonoylglycerol (2-AG) in rat brain samples. In-tube SPME-which consisted of a microtube of restricted access material (RAM) with a hydrophilic diol external surface and a hydrophobic octyl inner surface-efficiently excluded (up to 95%) macromolecules from the biological samples and selectively pre-concentrated the analytes. In-tube SPME parameters, such as sample volume, mobile phases, flow rate, and pre-concentration time, were evaluated to improve the extraction efficiency and throughput performance. The selectivity of the in-tube SPME and MS/MS (MRM mode) techniques allowed them to be directly coupled online, which dismissed the need for the chromatographic separation step. The in-tube SPME-MS/MS method was validated and shown to be linear from 6.0 to 30.0 ng mL-1 for AEA and from 10.0 to 100.0 ng mL-1 for 2-AG; the intra- and inter-assay accuracy and precision were lower than 15%. Parallelism between the calibration curves constructed in the matrix and aqueous solution confirmed that there was no matrix effect. The method allowed endogenous concentrations of AEA and 2-AG to be determined in rat brain striatum from unilaterally 6-hydroxydopamine-lesioned animals. The concentrations of these endocannabinoids in striatum ipsilateral and contralateral to the lesion differed significantly (p

Despite nearly 80 years of advancements in gas chromatography (GC), indirect chemical matrix effects (MEs), known as the matrix-induced response enhancement effect, still occur to cause a high bias in the GC analysis of susceptible analytes, unless precautions are taken. Matrix-matched calibration is one common option used in GC to compensate for the MEs, but this approach is usually inconvenient, imprecise, and inefficient. Other options, such as the method of standard additions, surface deactivation techniques, chemical derivatizations, priming the GC, and/or use of internal standards, also have flaws in practice. When methods are accommodating, the use of analyte protectants (APs) can provide the best practical solution to not only overcome MEs, but also to maximize analyte signal by increasing chromatographic and detection efficiencies for the analytes. APs address the source of MEs in every injection by filling active sites in the GC inlet, column, and detector, particularly in GC–MS, rather than the analytes that would otherwise undergo degradation, peak tailing, and/or diminished response due to interactions with the active sites. The addition of an adequate amount of APs (e.g. sugar derivatives) to all calibration standards and final extracts alike often leads to lower detection limits, better accuracy, narrower peaks, and greater robustness than the other options to compensate for MEs in GC. This article consists of a critical review of the scientific literature, proposal of mechanisms and theory, and re-evaluation studies involving APs for the first time in GC-orbitrap and GC–MS/MS with a high-efficiency ion source design. The findings showed that 1 µg each of co-injected shikimic acid and sorbitol in the former case, and 1 µg shikimic acid alone in the latter case, led to high quality results in multi-residue analysis of pesticides and environmental contaminants., R.R.R. would like to thank to the International Mentoring Foundation for the Advancement of Higher Education (IMFAHE) organization for the fellowship to spend 4 months as a visiting scientist with the USDA. USDA authors thank ThermoFisher Scientific for loan of the GC-orbitrap instrument.

Crotonaldehyde (Cro) is one of widespread and genotoxic α,β-unsaturated aldehydes and can react with the exocyclic amino group of 2'-deoxyguanosine (dG) in genomic DNA to form 1,N(2)-propano-2'-deoxyguanosine (ProdG) adducts. In this study, two diastereomers of high purity were prepared, including non-isotope and stable isotope labeled ProdG adducts, and exploited stable isotope dilution-based calibration method. By taking advantage of synthesized ProdG standards, we developed a sensitive ultrahigh performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UHPLC-ESI-MS/MS) method for accurate quantification of two diastereomers of ProdG adducts. In addition to optimization of the UHPLC separation, ammonium bicarbonate (NH4HCO3) was used as additive in the mobile phase for enhancing the ionization efficiency to ProdG adducts and facilitating MS detection. The limits of detection (LODs, S/N=3) and the limits of quantification (LOQs, S/N=10) are estimated about 50 amol and 150 amol, respectively. By the use of the developed method, both diastereomers of ProdG adducts can be detected in untreated human MRC5 cells with a frequency of 2.4-3.5 adducts per 10(8) nucleotides. Crotonaldehyde treatment dramatically increases the levels of ProdG adducts in human MRC5 in a concentration-dependent manner.

To-date, there has been no effective chiral capillary electrophoresis-mass spectrometry (CE-MS) method reported for the simultaneous enantioseparation of the antidepressant drug, venlafaxine (VX) and its structurally-similar major metabolite, O-desmethylvenlafaxine (O-DVX). This is mainly due to the difficulty of identifying MS compatible chiral selector, which could provide both high enantioselectivity and sensitive MS detection. In this work, poly-sodium N-undecenoyl-L,L-leucylalaninate (poly-L,L-SULA) was employed as a chiral selector after screening several dipeptide polymeric chiral surfactants. Baseline separation of both O-DVX and VX enantiomers was achieved in 15 min after optimizing the buffer pH, poly-L L-SULA concentration, nebulizer pressure and separation voltage. Calibration curves in spiked plasma (recoveries higher than 80%) were linear over the concentration range 150–5,000 ng/mL for both VX and O-DVX. The limit of detection (LOD) was found to be as low as 30 ng/mL and 21 ng/mL for O-DVX and VX, respectively. This method was successfully applied to measure the plasma concentrations of human volunteers receiving VX or O-DVX orally when co-administered without and with indinivar therapy. The results suggest that micellar electrokinetic chromatography electrospray ionization-tandem mass spectrometry (MEKC-ESI-MS/MS) is an effective low cost alternative technique for the pharmacokinetics and pharmacodynamics studies of both O-DVX and VX enantiomers. The technique has potential to identify drug-drug interaction involving VX and O-DVX enantiomers while administering indinivar therapy.

The adsorption behavior of the model proteins: alpha-Lactalbumin, Bovine Serum Albumin, Lysozyme, and a monoclonal antibody, in single component and in binary mixtures, was investigated on two different hydrophobic interaction chromatography resins using both static and dynamic methods. A kinetic model of the adsorption process was developed, which accounted for protein unfolding and intermolecular interactions in the adsorbed phase. The latter incorporated positive cooperative interactions, resulting from preferred and multilayer adsorption on the adsorbent surface, as well as negative cooperative interactions attributed to exclusion effects due to size exclusion and repulsion. Cooperative adsorption resulted in negative or positive deviations from the Langmuir model for both single and multicomponent isotherms. The model was used to assess possible contributions of different adsorption mechanisms of proteins and their structurally different forms to the overall adsorption pattern, as well as to simulate chromatographic band profiles under different loading conditions. For proteins with unstable structure, the overall adsorption isotherm was dominated by binding of unfolded species at low surface coverage and by positive cooperative adsorption at high surface coverage. Furthermore, regardless of structural stability, exclusion effects influenced strongly adsorption equilibrium, particularly at low surface coverages. In case of chromatographic elution, i.e. under dynamic conditions, unfolding, negative cooperative adsorption, and kinetic effects governed the retention behavior and determined peak shapes, whereas the effect of positive cooperative adsorption was negligible.

Several calibration approaches were evaluated for the quantitation of volatile organic compounds in air using miniaturized exhaustive and non-exhaustive sampling techniques, such as in-tube extraction (ITEX) and solid phase microextraction (SPME) Arrow. Eleven compounds, 2-ethyl-hexanol, hexanal, nonanal, toluene, ethyl-benzene, methyl isobutyl ketone, acetophenone, p-cymene, alpha-pinene, trimethylamine and triethylamine, all them found in the natural air samples, were selected as model analytes. Liquid injection, liquid standard addition to the sorbent bed and gas phase standards provided by an automatic permeation system, were evaluated in the case of ITEX packed with laboratory-made 10% polyacrylonitrile (PAN) material. Two different approaches, based on sampling of gas phase compounds from the permeation system and from sample vial containing gas phase standards, were evaluated for SPME Arrow with two different coatings, commercial divinylbenzene-poly(dimethylsiloxane) (DVB-PDMS) and laboratory-made mesoporous Mobil Composition of Matter No. 41 (MCM-41). In addition, interface model approach was used for the calculation of the real concentration of the target analytes in the sample from the total amount of analytes injected into the GC-MS in the case of SPME Arrow. Similar results were obtained with the different approaches used for the quantitation by ITEX and SPME Arrow. However, the use of gas phase standards with sample matrix similar to the natural samples, allowed the permeation system to provide the most reliable results for the quantitation of the target analytes. For this approach, linearity (expressed as r(2) values) ranged between 0.991 and 0.999. The limit of detection ranged from 0.5 mu g/m(3) (trimethylamine, MCM-41) to 2.2 x 10(-4) mu g/m(3) (methyl isobutyl ketone, MCM-41). In addition, the use of the fully automated permeation system provided good reproducibility values that were between 1.4% (acetophenone, MCM-41) and 7.8% (methyl isobutyl ketone, 10% PAN). The linear ranges were at least 3 order of magnitude for all the studied analytes with the exception of the calibration curve developed for trimethylamine with SPME Arrow (linear ranges between LOQ and 4.9 mu g/m(3) (DVB-PDMS) and LOQ and 9.8 mu g/m(3) (MCM-41)). (C) 2019 Elsevier B.V. All rights reserved.

In the nutrition field, there is a lack of understanding about the impact that dietary chiral composition may have on health, especially regarding cooked meals. Chiral amino acids (AAs) are naturally present in food and their proportion may vary quite a lot. Besides, the D-amino acids (D-AAs) are present in very low concentration compared to L-AAs, so very sensitive methods are required for their accurate quantitation. Moreover, some of them have been described as indicators of quality and different food processes. In this research, we propose a robust method for the absolute quantitation and enantiomeric ratio of 17 D-AAs in cooked meals. The AAs were extracted from 1 g of the homogenised meal with methanol, derivatised with (S)-N-(4-nitrophenoxycarbonyl) phenylalanine methoxyethyl ester ((S)-NIFE) and analysed by RP-LC-MS/MS. The separation was carried out with an Acquity BEH C18 (100 mm x 2.1 mm, 1.7 µm) column at 70 ºC, with 10 mmol/L ammonium bicarbonate in water as eluent A and acetonitrile as eluent B at a 0.3 mL/min flow rate in gradient elution. The MS operated in positive electrospray ionisation method in multiple reaction monitoring (MRM) mode. Isotopically labelled AAs were used as internal standards for the quantitation. The method was validated for 17 D-AAs in the cooked food samples in terms of specificity, linearity, precision, accuracy, matrix effect and stability. LLOQ are 2.0 ng/mL for most of them. Additionally, linearity was also studied for L-AAs. After optimization and validation, the method was applied to real breakfast, lunch and dinner samples of cooked meals (n = 18) that were part of a diet with a very high concordance with WHO dietary guidelines. Level of concentration of major and minor D-AAs have been described per total daily intake and within each of the three main meals. This method can be used for quality control purposes as well as to investigate the role of chiral composition in food and clinical outcomes.

We present here a new measurement method for the rapid extraction and accurate quantification of technical nonylphenol (NP) and 4-t-octylphenol (OP) in complex matrix water samples by UHPLC-ESI-MS/MS. The extraction of both compounds is achieved in 30 min by means of hollow fiber liquid phase microextraction (HF-LPME) using 1-octanol as acceptor phase, which provides an enrichment (preconcentration) factor of 800. On the other hand we have developed a quantification method based on isotope dilution mass spectrometry (IDMS) and singly 13 C 1 -labeled compounds. To this end the minimal labeled 13 C 1 -4-(3,6-dimethyl-3-heptyl)-phenol and 13 C 1 -t-octylphenol isomers were synthesized, which coelute with the natural compounds and allows the compensation of the matrix effect. The quantification was carried out by using isotope pattern deconvolution (IPD), which permits to obtain the concentration of both compounds without the need to build any calibration graph, reducing the total analysis time. The combination of both extraction and determination techniques have allowed to validate for the first time a HF-LPME methodology at the required levels by legislation achieving limits of quantification of 0.1 ng mL −1 and recoveries within 97–109%. Due to the low cost of HF-LPME and total time consumption, this methodology is ready for implementation in routine analytical laboratories.

The structural characteristics of the HyperCel family of cellulosic ion-exchange materials (Pall Corporation) were assessed using methods to gauge the pore dimensions and the effect of ionic strength on intraparticle architecture. Inverse size exclusion chromatography (ISEC) was applied to the S and STAR AX HyperCel derivatives. The theoretical analysis yielded an average pore radius for each material of about 5 nm, with a particularly narrow pore-size distribution. Electron microscopy techniques were used to visualize the particle structure and relate it to macroscopic experimental data. Microscopy of Q and STAR AX HyperCel anion exchangers presented some qualitative differences in pore structure that can be attributed to the derivatization using conventional quaternary ammonium and salt-tolerant ligands, respectively. Finally, the effect of ionic strength was studied through the use of salt breakthrough experiments to determine to what extent Donnan exclusion plays a role in restricting the accessible pore volume for small ions. It was determined that Donnan effects were prevalent at total ionic strengths (TIS) less than 150 mM, suggesting the presence of a ligand-containing partitioning volume within the pore space.

Analytical strategies for screening, quantitation and confirmation of a group of 100 pesticides in fruit and vegetable samples by LC-MS and LC-MS/MS were developed. The pesticides studied belong to different chemical families of herbicides, insecticides and fungicides. A selection of some degradation products was also included. Chromatographic separation was performed using a Zorbax Eclipse XDB-C8 column (150 mm × 4.6 mm and 5 µm particle size), and gradient elution with acetonitrile-water (both with 0.1% formic acid) as mobile phase. LC-MS/MS using highly-selective selected reaction monitoring (H-SRM) acquisition mode monitoring two transitions for each compound showed to be the most sensitive methodology. Quantitation was carried out using matrix-matched standard calibration and good linearity of response was demonstrated (r > 0.998). Limits of detection (by acquiring two transitions and with the ion-ratio requirements) ranged between 0.01 and 20 µg/kg were obtained. So, in general, the sensitivity achieved meets the maximum residue levels (MRLs) established by the European Union regulation for food monitoring programs. Pesticide confirmation was carried out following European Union guidelines. In order to prevent false-positives, further confirmatory strategies were proposed. LC-MS in highly-selective selected ion monitoring (H-SIM) mode with accurate mass measurement was used to obtain an orthogonal criterion (exact mass) for confirmation. Accurate mass measurements were always bellow 0.9 mDa for almost all pesticides studied (similar to those described with TOF instruments). A user reversed energy ramp (RER) product ion scan spectra library was generated by means of a data dependent analysis for routine library searching of pesticides. The combination of LC-MS/MS in H-SRM mode and the generation of the RER product ion scan spectra and library search were then used to achieve further confirmation on pesticide analysis. The LC-MS and LC-MS/MS strategies developed were successfully applied for the analysis and confirmation of pesticides in different types of fruit and vegetables samples, and examples of the screening, quantitation and confirmation of pesticides in these samples are shown in this work.

This study describes a method based on direct contact sorptive tape extraction followed by on-line thermal desorption gas chromatography-mass spectrometry (DC-STE-GC-MS) to detect and quantify a group of suspected volatile allergens on the European Union (E.U.) list and a related compound on the skin (the stratum corneum) of volunteers treated with a cream of known composition fortified with the reference allergens. The following compounds were tested: citronellol, Z-citral (neral), geraniol, cinnamaldehyde, anisyl alcohol, cinnamyl alcohol, eugenol, methyleugenol, coumarin, isoeugenol, alpha-isomethylionone, 2-(4-tert-butylbenzyl)propionaldehyde (lilial), alpha-amylcinnamaldehyde, alpha-hexylcinnamaldehyde. Sorptive tape extraction (STE) is a sorption-based sampling technique in which a flexible polydimethylsiloxane (PDMS) tape is used to recover analytes by direct contact with the surface of a solid matrix or from the headspace in equilibrium with it. The reliability of the method was confirmed by: (i) allergen recoveries varying from 52.3% for lilial to 95.7% for neral, (ii) linearity in the range 10-150ppm, with regression coefficient R(2) always above 0.97, (iii) repeatability of each analyte, RSD% never exceeding 10%, (iv) intermediate precision, always below 15%, and (v) LOD and LOQ in the ppb range, therefore fully compatible with E.U. prescriptions (ppm). Other parameters such as substantivity analyte, approximate permeation through skin and influence of different nature of stratum corneum on recovery were also investigated. The method was also successfully applied to five commercially available creams declared to contain some of the allergens in question spread on the skin of the same volunteers.

金沢大学医薬保健研究域薬学系, To measure the actual exposure of a person to 1-nitropyrene (1-NP) in airborne particulate matter, it is considered more accurate to collect air samples with a portable air sampler than to sample at a fixed location. However, because the portable samplers can sample only small volumes, a sensitive method is needed to analyze the compounds that are collected on a filter. Here we describe a high-performance liquid chromatographic (HPLC) method with fluorescence detection that is sensitive and precise enough for use with portable air samplers. The developed column-switching system successfully removed the interfering substances in the samples with only a simple pretreatment. To improve the precision of the measurement, deuterated 1-NP was used as an internal standard, and it eluted immediately prior to 1-NP with sufficient resolution (Rs, 1.50). The detection limit was 0.32 fmol/injection, and the calibration range was from 2 to 100 fmol. The proposed method was applied to determining 1-NP in fine airborne particulate matter (PM2.5) at two sites with low pollution levels. 1-NP was detected in all samples at concentrations in the low fmol/m3 range. The proposed method has enough sensitivity and precision to determine 1-NP in the limited air volume of the portable sampler. © 2009 Elsevier B.V. All rights reserved.

A sensitive and reliable method based on column switching liquid chromatography (LC) coupled to a triple quadrupole mass spectrometer (MS) has been developed for quantification of 19 perfluorinated compounds (PFCs) in serum. A volume of only 150microl serum is used and protein precipitation by methanol is the only sample preparation necessary prior to injection into the column switching system. Pseudo-MRM is used as a detection mode for determination of PFCs, resulting in reduced background noise and considerably increased sensitivity for the perfluorinated alkyl sulfonates and the perfluorinated alkyl sulfonamides. The estimated limits of detection for the method were as low as 0.0020-0.050ngPFCs/ml serum. The accuracy determined from spiking experiments, reported as recovery of added amount, was between 85 and 121% in the range 0.20-50ngPFC/ml serum, except for perfluorodecylsulfonate for which the accuracy was 146% at 0.20ngPFC/ml serum. The low sample volume needed, the limited manual handling and the broad range of analytes which are included, make this method advantageous for large-scale epidemiological studies. This column-switching technique can easily be set up on standard LC-MS/MS instruments and is thus available to a wide range of laboratories.

The 2nd international interlaboratory study (ILS) on perfluorinated compounds (PFCs) in environmental samples was organized to assess the performance of 21 North American and European laboratories on the analysis of PFCs in water and fish. A study protocol was provided to assess accuracy, precision, matrix effects and to study the use of in-house standards. The participants used shared native and mass-labelled standards that were provided for this study to quantify the PFC concentrations in the samples. Matrix effects in the determination of PFCs can be considerable and can decrease the sensitivity, the accuracy and internal standard recoveries. Therefore, two quantification methods were evaluated by all laboratories: standard addition quantification (SAQ) and solvent-based calibration curve quantification (SBCCQ; using mass-labelled internal standards (IS)). The between laboratory reproducibility (i.e. coefficient of variance) was smaller for the SBCCQ results (except for PFBS and PFHxS for which no mass-labelled analogues were available) compared to those obtained by the SAQ method. The within laboratory precision of individual laboratories is good (mean for all PFCs in water 12% and 6.8% in fish). The good performance is partially attributable to the use of well-defined native- and mass-labelled standards. Therefore, the SBCCQ method is recommended. The results show that analytical methods for PFCs in water and fish have improved considerably. Critical steps identified in this study are (i) the use of well-defined native standards for quantification, (ii) the use of mass-labelled internal standards (preferably one for each target compound) and (iii) minimization of matrix effects by a better clean up. © 2008 Elsevier B.V. All rights reserved.

The ability to quantify ultra-low concentrations of biologically active compounds in biological matrices is essential for the study of pharmacological/toxicological effects occurring at low doses. Selective solid-phase extraction (SPE) was combined with highly sensitive capillary LC (microLC)-MS/MS analysis to achieve ultra-sensitive quantification of the anti-cancer drug paclitaxel in cancer cells. The optimized SPE selectively extracted paclitaxel and eliminated undesirable matrix compounds, thus enabling a high sample loading volume on the microLC column without compromising chromatographic performance and operational robustness. The validated lower limit of quantification (LOQ) was 5pg/mL, approx. 20-fold more sensitive than published LC-MS/MS methods. The calibration curve was linear over the range of 5-6250pg/mL. Accuracy was 98-109% and the variation (CV%) was 2.3-7.4%. This method was applied successfully to quantify temporal drug accumulation by A121a ovarian cancer cells treated with sub-ng/mL concentrations of paclitaxel.

In the present work, an HPLC method is proposed to simultaneously detect and quantify water- and fat-soluble vitamins, phenolic compounds, carotenoids and chlorophylls in a single run, by using an ultradeactivated C18 column and gradient separation using trifluoroacetic acid, water and methanol. It is shown that the HPLC method provides baseline separation of all these compounds with good resolution values in 40 min. Moreover, other figures of merit of the method show a good linear response and low detection limits for all the compounds considered in the present study. Furthermore, the usefulness of this method is demonstrated via its successful application to the analysis of different beverages from different natural origin (orange, strawberry, apple, peach pineapple, plum and blackcurrant juices, soybean milk, beers) without the need of any previous sample preparation. A good correlation is also found by comparing the total phenol content (measured by Folin-Ciocalteu method) with the sum of total phenolic compounds obtained using the proposed HPLC method. By using statistical tools, the main compounds associated with antioxidant activity of the extracts (measured by 1,1-diphenyl-2-picrylhydrazyl radical scavenging) were assessed.

Extraction followed by reverse phase liquid chromatography (LC)/electrospray ionization-ion trap-mass spectrometry (ESI-IT-MS) analysis has been successfully developed for the determination of peptaibols, fungal toxic metabolites, in marine sediments. Spiking experiments showed that the mean recovery of target compounds exceeded 85% at a spiking level of 10 ng/g of sediment (wet weight). Detection and quantification limits were 250 and 830 pg/g of sediment, respectively. The method developed constituted the first sensitive assay for quantification of peptaibol trace amounts in a natural environment. A concentration of 5 ng/g in sediment samples collected from Fier d'Ars was found.

Studies of inorganic carbon cycle in natural waters provide important information on the biological productivity and buffer capacity. Determination of total inorganic carbon, alkalinity and dissolved carbon dioxide gives an indication of the balance between photosynthesis and respiration by biota, both within the water column and sediments, and carbon dioxide transfers from the water column to the atmosphere. There are few methods to measure and distinguish the different forms of inorganic carbon, but all require a measure or an indirect quantification of total inorganic carbon. A direct measurement of TIC in water is made possible by the introduction of electrolytic generated hydroxide eluent in ion chromatography which allows to detect a chromatographic peak for carbonate. The advantage of this method is that all the inorganic forms of carbon are converted in carbonate at eluent pH and can be detected as a single peak by conductivity detection. Repeatability of carbonate peak was evaluated at different levels from 0.02 to 6 mequiv. l−1 both in high purity water and in real samples and ranged from 1 to 9%. The calibration curve was not linear and has to be fitted by a quadratic curve. Limit of detection was estimated to be 0.02 mequiv. l−1. Accuracy has been estimated by comparing ion chromatography method with total inorganic carbon calculated from alkalinity and pH. The correlation between the two methods was good (R2 = 0.978, n = 141). The IC method has been applied to different typologies of surface waters (alpine and subalpine lakes and rivers) characterised by different chemical characteristics (alkalinity from 0.05 to 2 mequiv. l−1 and pH from 6.7 to 8.5) and low total organic carbon concentrations. This analytical method allowed to describe the distribution of TIC along the water column of two Italian deep lakes.

We developed capillary zone electrophoresis (CZE) with direct UV detection for determination of ammonium in environmental water samples. Ammonium in the samples was partly converted into ammonia in the alkaline background electrolyte (BGE) during migration and was detected by molecular absorption of ammonia at 190 nm in approximately 7 min. The limit of detection (LOD) for ammonium was 0.24 mg/l (as nitrogen) at a signal-to-noise ratio of three. The respective values of the relative standard deviation (RSD) of peak area, peak height, and migration time for ammonium were 2.1, 1.8, and 0.46%. Major alkali and alkaline earth metal ions coexisting in the samples did not interfere with ammonium determination by the proposed method. The proposed method determined ammonium in surface water and sewage samples. The results were compared to those obtained using ion chromatography (IC).

For practical chromatographers it is extremely difficult to judge the merits and limitations of new technological developments. On the other hand, it is nearly impossible for those at the forefront of technology to judge the implications of their efforts for all specific applications of chromatography. Both chromatographers and researchers can be aided by a classification of the numerous specific applications into a few well-defined categories. In this paper, we propose such a classification of all chemical analysis by chromatography into three generic types of applications, viz. target-compound analysis, group-type separation, and fingerprinting. The requirements for each type are discussed in general terms. The classification scheme is applied to assess the benefits and limitations of comprehensive two-dimensional gas chromatography (GCxGC) and the possible additional benefits of using multivariate-analysis (MVA) techniques for each type of application. The conclusions pertaining to the generic types of applications are indicative for the implications of new developments for specific chemical analysis by chromatography. © 2004 Elsevier B.V. All rights reserved.

The preparation and mesomorphic properties of a substituted bis(dithiolene)nickel complex derived from 4, 4′-dimethoxybenzil are reported. The phase transition temperatures were based on data obtained by polarized light microscopy and differential scanning calorimetry. The mesogenic phase existed over the temperature range from 77 to 175 °C. A novel micropacked column (1.5 or 3 m ×1 mm i.d.) prepared from the slurry of bis[1,2-bis(4-n-undecyloxyphenyl)ethane-1,2-dithiolene] nickel(II) (5%, w/w), coated on Chromosorb W was applied for the separation of dialkyl sulfides. The non-linearity (discontinuity) of Van’t Hoff plots suggests that the liquid crystal property existed even in the coated phase. Factors affecting the retention and the sample selectivity on the prepared column were examined by using a flame photometric detector (FPD). The separation might be based on the mechanism of ligand exchange, shape selectivity and polarity interaction besides the vapor pressure. LOD for the determination of dialkyl sulfides was below 1 ng for most of the analytes.

Univariate data accumulated for the purpose of calibration of chromatographic and spectroscopic methods often exhibit slight but definite curvature. In this paper the performance of a non-linear calibration equation with the capacity to account empirically for the curvature, y = a + bx m, (m ≠ 1) is compared with the commonly used linear equation, y = a + bx, as well as the quadratic equation, y = a + bx + cx2. All equations were applied to high quality HPLC calibration data using unweighted least squares. Parameter estimates and their standard errors were calculated for each equation. Standard errors and 95% prediction intervals in analyte concentrations were estimated with the aid of the fitted equations and their respective covariance matrices. Results indicate that the non-linear and quadratic equations each provide a better fit than the linear equation to the data considered here, as judged by the Akaikes information criterion (AIC), the adjusted coefficient of multiple determination, the magnitude and scatter of residuals, standard errors in estimated analyte concentrations and lack of fit analysis of variance (ANOVA). While the difference between the equations y = a + bx + cx2 and y = a + bxm as judged by the same criteria is more marginal, this work suggests that the non-linear calibration equation should be considered when a curve is required to be fitted to low noise calibration data which exhibit slight curvature. © 2004 Elsevier B.V. All rights reserved.

Both, experimental investigation of protein adsorption processes and mathematical models describing such processes indicate, that the pH in the absorbent particle might be the key factor for an improved understanding of these chromatographic processes. Thus, a technique aiming at the spatially resolved pH measurement in macroscopic large absorbent particles is presented. The first application of this method, being based on confocal laser scanning microscopy (CLSM), revealed an apparent dependence of the pH calibration curve on the scanning depth. By a model-based approach, factors distorting the measurement signal are identified: The wavelength-dependent light scattering and the re-absorption of emitted light. The resulting consequences for further development and application of CLSM based techniques to measure pH in macroscopic large absorbent particles are illustrated and discussed.

For the determination of components present in samples at very low concentrations, large injection volumes have to be applied in order to introduce a detectable amount of the analytes in capillary zone electrophoresis (CZE). To obtain a good resolution, the sample analytes have to be concentrated in narrow bands and therefore sample stacking is often applied. Sample stacking can lead to an increase in the electroosmotic flow and extra peak broadening during the analysis, through which the gain in resolution will be lost. Further, the presence of different electrolytes in the capillary can cause pH shifts. In this paper a model is given for the calculation of migration times of components applying sample stacking, and the effects of sample stacking in CZE on resolution, calibration graphs and pH are discussed

Twenty-six drugs in solutions for intravenous injection were determined by capillary isotachophoresis with only one calibration point for each component. The maximum deviation of the labelled concentration was 2%. A new calibration constant is introduced, viz., the response factor (RF, dimensionless), which is independent of the diameter of the capillary, the construction of the universal detector and the driving current used during detection. It is shown that the RF can be used on different equipment, using different currents during detection. It appears that the RF is usable for routine analysis when a deviation of 5% is acceptable. Daily one-point recalibration, however, improves this value to 1%.