Cryogenic oven-trapping gas chromatography for analysis of volatile organic compounds in body fluids

Cryogenic oven-trapping (COT) with capillary GC has been successfully applied to analysis of chloroform, dichloromethane, trichloroethylene, diethyl ether, the components of solvent thinner (ethyl acetate, benzene, n-butanol, toluene, and others), xylene isomers, cyanide, ethanol, hexanes, general anesthetics, and styrene in human body fluids. This COT-GC technique was compared with headspace solid-phase microextraction (SPME) coupled with GC for some volatile organic compounds (VOC); for all compounds compared the sensitivity achieved using COT-GC was more than ten times higher than for headspace SPME-GC. The COT-GC method is recommended for widespread use in forensic and environmental toxicology, because it is simple, requires no special GC operations, and yet enables high sensitivity and high resolution.     

Combined solid‐phase microextraction and high‐performance liquid chromatography with ultroviolet detection for simultaneous analysis of clenbuterol,salbutamol and ractopamine in pig samples

A simple and sensitive method based on the combination of solid‐phase microextraction (SPME) and high‐performance liquid chromatography with ultroviolet detection was developed for the simultaneous determination of clenbuterol, salbutamol and ractopamine in pig samples. Parameters of the SPME procedure affecting extraction efficiency, such as the type of fiber, extraction time, extraction temperature, ion strength, pH of sample and stirring rate, were optimized. The developed method was validated according to the International Conference on Harmonization guidelines. The calibration curves were linear over a range of 0.5–50 µg/L for clenbuterol and ractopamine, and 0.2–20 µg/L for salbutamol. The limits of detection were 0.1 µg/L for clenbuterol, 0.05 µg/L for salbutamol and 0.1μg/L for ractopamine, respectively. The averages of intra‐ and inter‐day accuracy ranged from 79.8 to 92.4%. The intra‐day and inter‐day precision were below 9.6% for the three analytes. This method exhibited the advantages of simplicity, rapidity and low solvent consumption, and was suitable for the monitoring of β₂‐agonists residue in pig samples. Copyright © 2013 John Wiley & Sons, Ltd.     

Rapid determination of volatile organic compounds in environmentally hazardous wastewaters using solid phase microextraction

Solid phase micro-extraction (SPME) was applied to the determination of volatile organic compounds (VOC) in wastewater discharges. Environmentally significant samples, typical of those subject to regulatory control, were examined and included discharges from pharmaceutical, petrochemical and municipal sewerage treatment plants. Analysis was performed using gas chromatography – mass spectrometry (GC-MS) following sampling using headspace or immersion SPME. Fused silica fibres, coated with either poly(dimethylsiloxane) or poly(acrylate), were examined to determine VOC which included chloroform, saturated carboxylic acids, alkylbenzenes, phenol, benzonitrile and benzofuran. Detection limits varied from 10 to 170 ng/ml and satisfactory relative standard deviations (%RSD < 10) were obtained. For most samples, headspace sampling was preferred to immersion. SPME was found to be a useful technique for the rapid screening of wastewaters for VOC.     

Gaseous and Particle‐bound VOC Products of Combustion Extracted by Needle Trap Samplers

Gaseous benzene, toluene, ethylbenzene and o‐xylene (BTEX) were extracted by using the divinylbenzene (DVB) particles (mesh sizes 60–80, 80–100 and 100–120) as sorbents packed in passive needle trap samplers (NTS). This study performed feasibility tests of these self‐designed DVB‐NTS as diffusive time‐weighted average (TWA) samplers and compared extraction efficiency with that of 100 mm polydimethylsiloxane‐solid phase microextration (PDMS‐SPME) fiber for sampling gaseous and particle‐bound volatile organic compounds (VOCs) from burning mosquito coils. Experimental results indicated that extraction rate of NTS is a reliable index in extracting VOCs. Additionally, comparisons of the NTS in extracting BTEX mass showed the NTS packed with the smallest diameters of adsorbent particles (100–120 mesh DVB) were the most effective. The mass of gaseous BTEX extracted by 100 μm PDMS‐SPME fiber were substantially lower than that extracted by DVB‐NTS of all meshes for the 30‐min TWA sampling of burning mosquito coils, and NTS packed with 100–120 mesh DVB adsorbed BTEX 50–120 ng BTEX. Particles clogging inside the packed phase of NTS inhibited VOC extraction performance after 3–5 samplings of burning particles, especially NTS packed with small‐diameter adsorbents.     

Qualitative and quantitative analysis of THC, 11‐hydroxy‐THC and 11‐nor‐9‐carboxy‐THC in whole blood by ultra‐performance liquid chromatography/tandem mass spectrometry

A qualitative and quantitative analytical method was developed for the simultaneous determination of Δ⁹‐tetrahydrocannabinol (THC), 11‐hydroxy‐Δ⁹‐tetrahydrocannabinol (11‐OH‐THC) and l1‐nor‐9‐carboxy‐Δ⁹‐tetrahydrocannabinol (THC‐COOH) in whole blood. The samples were prepared by solid‐phase extraction followed by ultra‐performance liquid chromatography/tandem mass spectrometry (UPLC/MS/MS) analysis using positive ion electrospray ionization and multiple reaction monitoring. The chromatographic separation was performed with an Acquity UPLC® HSS T3 (50 × 2.1 mm i.d., 1.8 µm) reversed‐phase column using a methanol/2 mM ammonium formate (formic acid 0.1%) gradient in a total run time of 9.5 min. MS/MS detection was achieved with two precursor‐product ion transitions per substance. The method was fully validated, including selectivity and capacity of identification, according to the identification criteria (two transitions per substance, signal‐to‐noise ratio, relative retention time and ion ratio) without the presence of interferences, limit of detection (0.2 µg/L for THC and 0.5 µg/L for 11‐OH‐THC and THC‐COOH), limit of quantitation (0.5 µg/L for all cannabinoids), recovery (53–115%), carryover, matrix effect (34‐43%), linearity (0.5‐100 µg/L), intra‐assay precision (CV < 10% for the relative peak area ratios and <0.1% for the relative retention time), inter‐assay accuracy (mean relative error <10%) and precision (CV <11%). The method has already been successfully used in proficiency tests and subsequently applied to authentic samples in routine forensic analysis. Copyright © 2011 John Wiley & Sons, Ltd.     

SPME sampling of BTEX before GC/MS analysis: examples of outdoor and indoor air quality measurements in public and private sites

This article presents the results of an exploratory application of the Solid Phase MicroExtraction (SPME) technique to the analysis of BTEX (benzene, toluene, ethylbenzene and xylenes) at the microg/m3 level in outdoor and indoor air. The salient features of the method validation are reported. As shown by the various examples of field sampling described, SPME technique appears as a method of choice for fast qualitative analysis and quantitative determination of Volatile Organic Compounds (VOC). The small dimensions of the SPME sampling system and the short sampling time let envisage its utilisation for the rapid diagnostic of outdoor and indoor air quality.     

Desorption electrospray ionisation mass spectrometric analysis of chemical warfare agents from solid‐phase microextraction fibers

Desorption electrospray ionisation mass spectrometry (DESI‐MS) was recently reported for the direct analysis of sample media without the need for additional sample handling. During the present study, direct analysis of solid‐phase microextraction (SPME) fibers by DESI‐MS/MS was evaluated with indoor office media that might be collected during a forensic investigation, including wall surfaces, office fabrics, paper products and Dacron swabs used for liquid sampling. Media spiked at the µg/g level with purified chemical warfare agents and a complex munitions grade sample of tabun, to simulate the quality of chemical warfare agent that might be used for terrorist purposes, were successfully analysed by DESI‐MS/MS. Sulfur mustard, a compound that has not been successfully analysed by electrospray mass spectrometry in the past, was also sampled using a SPME fiber and analysed for the first time by DESI‐MS/MS. Finally, the overall analytical approach involving SPME headspace sampling and DESI‐MS analysis was evaluated during a scenario‐based training live agent exercise. A sarin sample collected by the military was analysed and confirmed by DESI‐MS in a mobile laboratory under realistic field conditions. Copyright © 2007 Crown in the right of Canada. Published by John Wiley & Sons, Ltd.     

High‐quality poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylenevinylene] synthesized by a solid–liquid two‐phase reaction: Characterizations and electroluminescence properties

Poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylenevinylene] (MEH‐PPV) with a molar mass of 26–47 × 10⁴ g mol^?1 and a polydispersity of 2.5–3.2 was synthesized by a liquid–solid two‐phase reaction. The liquid phase was tetrahydrofuran (THF) containing 1,4‐bis(chloromethyl)‐2‐methoxy‐5‐(2′‐ethylhexyloxy)benzene as the monomer and a certain amount of tetrabutylammonium bromide as a phase‐transfer catalyst. The solid phase consisted of potassium hydroxide particles with diameters smaller than 0.5 mm. The reaction was carried out at a low temperature of 0 °C and under nitrogen protection. No gelation was observed during the polymerization process, and the polymer was soluble in the usual organic solvents, such as chloroform, toluene, THF, and xylene. A polymer light‐emitting diode was fabricated with MEH‐PPV as an active luminescent layer. The device had an indium tin oxide/poly(3,4‐ethylenedioxylthiophene) (PEDOT)/MEH‐PPV/Ba/Al configuration. It showed a turn‐on voltage of 3.3 V, a luminescence intensity at 6.1 V of 550 cd/m², a luminescence efficiency of 0.43 cd/A, and a quantum efficiency of 0.57%. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3049–3054, 2004     

Evaluation of needle trap micro‐extraction and solid‐phase micro‐extraction: Obtaining comprehensive information on volatile emissions from in vitro cultures

Volatile organic compounds (VOCs) emitted from in vitro cultures may reveal information on species and metabolism. Owing to low nmol L⁻¹ concentration ranges, pre‐concentration techniques are required for gas chromatography–mass spectrometry (GC–MS) based analyses. This study was intended to compare the efficiency of established micro‐extraction techniques – solid‐phase micro‐extraction (SPME) and needle‐trap micro‐extraction (NTME) – for the analysis of complex VOC patterns. For SPME, a 75 μm Carboxen®/polydimethylsiloxane fiber was used. The NTME needle was packed with divinylbenzene, Carbopack X and Carboxen 1000. The headspace was sampled bi‐directionally. Seventy‐two VOCs were calibrated by reference standard mixtures in the range of 0.041–62.24 nmol L⁻¹ by means of GC–MS. Both pre‐concentration methods were applied to profile VOCs from cultures of Mycobacterium avium ssp. paratuberculosis. Limits of detection ranged from 0.004 to 3.93 nmol L⁻¹ (median = 0.030 nmol L⁻¹) for NTME and from 0.001 to 5.684 nmol L⁻¹ (median = 0.043 nmol L⁻¹) for SPME. NTME showed advantages in assessing polar compounds such as alcohols. SPME showed advantages in reproducibility but disadvantages in sensitivity for N‐containing compounds. Micro‐extraction techniques such as SPME and NTME are well suited for trace VOC profiling over cultures if the limitations of each technique is taken into account.     

Charge‐Transfer Complex Formation in Gelation: The Role of Solvent Molecules with Different Electron‐Donating Capacities

A naphthalenediimide (NDI)‐based synthetic peptide molecule forms gels in a particular solvent mixture (chloroform/aromatic hydrocarbon, 4:1) through charge‐transfer (CT) complex formation; this is evident from the corresponding absorbance and fluorescence spectra at room temperature. Various aromatic hydrocarbon based solvents, including benzene, toluene, xylene (ortho, meta and para) and mesitylene, have been used for the formation of the CT complex. The role of different solvent molecules with varying electron‐donation capacities in the formation of CT complexes has been established through spectroscopic and computational studies.     

Toxicological determination and in vitro metabolism of the designer drug methylenedioxypyrovalerone (MPDV) by gas chromatography/mass spectrometry and liquid chromatography/quadrupole time‐of‐flight mass spectrometry

A method for the toxicological screening of the new designer drug methylenedioxypyrovalerone (MDPV) is described; with an emphasis on its application for anti‐doping analysis. The metabolism of MDPV was evaluated in vitro using human liver microsomes and S9 cellular fractions for CYP450 phase I and uridine 5′‐diphosphoglucuronosyltransferase (UGT) and sulfotransferase (SULT) phase II metabolism studies. The resulting metabolites were subsequently liquid/liquid extracted and analyzed using gas chromatography/mass spectrometry (GC/MS) as trimethylsilyl (TMS) derivatives. The structures of the metabolites were further confirmed by accurate mass measurement using a liquid chromatography/quadrupole time‐of‐flight (LC/QTOF) mass spectrometer. The studies demonstrated that the main metabolites of MDPV are catechol and methyl catechol pyrovalerone, which are in turn sulfated and glucuronated. The method for the determination of MDPV in urine has been fully validated by assessing the limits of detection and quantification, linearity, repeatability, and accuracy. This validation demonstrates the suitability for screening of this stimulant substance for anti‐doping and forensic toxicology purposes. Copyright © 2010 John Wiley & Sons, Ltd.     

碳纳米管顶空固相微萃取测定水中的多溴联苯醚

建立了顶空固相微萃取联结气相色谱-电子捕获检测器（HS-SPME-GC-ECD）测定水中多溴联苯醚的方法。制作了多壁碳纳米管涂层固相微萃取探头。优化了萃取时间,萃取温度,搅拌速度,顶空体积,溶液的pH,离子强度及有机溶剂等影响萃取效率的各种因素。比较了室温和100 ℃顶空萃取和直接萃取的效率。结果表明,室温下直接萃取比顶空萃取的效率高2-4倍,而在100 ℃时顶空萃取比直接萃取的效率高1-8倍。除BDE-154外,无论直接萃取还是顶空萃取,100 ℃时的萃取效率均高于室温。方法的线性范围50-1600 ng/L,相关系数为0.995-0.998,5种多溴联苯醚的最低检出限（S/N=3）为1.14-16.25 ng/L,相对标准偏差（RSD%,n=5）小于10%。本方法用于真实水样的测定,回收率为74.2%-98.7%。     

Guest‐Induced Arylamide Polymer Helicity: Twist‐Sense Bias and Solvent‐Dependent Helicity Inversion

A benzene/naphthalene alternately incorporated amide polymer was synthesized and characterized. ¹H NMR spectroscopy, fluorescence, and circular dichroism (CD) experiments indicated that, in chloroform, the polymer could be induced by the chiral l ‐aspartic acid dianion or one of its derivatives to form a helical tubular conformation with twist‐sense bias. CD titration studies showed that the l ‐aspartic acid dianion (8 equiv.) could lead to a maximum Cotton effect. It was also revealed that the twist‐sense bias obeyed the majority rule, and 70 % enantiomeric excess could realize the maximum helicity bias. Adding acetonitrile to the solution of chloroform caused inversion of the guest‐induced helicity bias of the polymer.     

A dispersive liquid–liquid micellar microextraction for the determination of pharmaceutical compounds in wastewaters using ultra‐high‐performace liquid chromatography with DAD detection

A dispersive liquid–liquid micellar microextraction (DLLMME) method coupled with ultra‐high‐performance liquid chromatography (UHPLC) using Diode Array Detector (DAD) detector was developed for the analysis of five pharmaceutical compounds of different nature in wastewaters. A micellar solution of a surfactant, polidocanol, as extraction solvent (100 μL) and chloroform as dispersive solvent (200 μL) were used to extract and preconcentrate the target analytes. Samples were heated above critical temperature and the cloudy solution was centrifuged. After removing the chloroform, the reduced volume of surfactant was then injected in the UHPLC system. In order to obtain high extraction efficiency, the parameters affecting the liquid‐phase microextraction, such as time and temperature extraction, ionic strength and surfactant and organic solvent volume, were optimized using an experimental design. Under the optimized conditions, this procedure allows enrichment factors of up to 47‐fold. The detection limit of the method ranged from 0.1 to 2.0 µg/L for the different pharmaceuticals. Relative standard deviations were <26% for all compounds. The procedure was applied to samples from final effluent collected from wastewater treatment plants in Las Palmas de Gran Canaria (Spain), and two compounds were measured at 67 and 113 µg/L in one of them. Copyright © 2014 John Wiley & Sons, Ltd.     

Experimental and theoretical investigation of a new rapid switching near‐infrared electrochromic conjugated polymer

A new rapid switching near‐IR electrochromic conjugated propeller‐shape polymer (PBTPAFL) with lower oxidation potential containing a di‐triarylamine group was synthesized via Suzuki coupling approach. The observed UV‐vis‐NIR absorption changes in the PBTPAFL film at various potentials are fully reversible and associated with strong color changes from the original light green to dark green and then to a Prussian blue. Excellent continuous cyclic stability of the electrochromic characteristics with a rapid color switching time 2.58 s and bleaching time 1.76 s was found as well. Compared with P1 and P2, the introduction of more electron‐donating propyl phenyl group in the para position of PBTPAFL lowered the oxidative potential and prevented coupling reaction during the electrochromic procedure. The high molecular weight conjugated polymer having high thermal stability with T_d10 more than 450 °C has excellent solubility in common organic solvents such as NMP, THF, chloroform, toluene, xylene, and benzene at room temperature (25 °C) due to the propeller‐shape structure and long alkyl chain on fluorene. Herein, from the combination of the experimental and computational study, we proposed a mechanism on the basis of the molecular orbital theory to explain the electrochromic oxidation behavior. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3913–3923, 2010.     

Fabrication of Bienzymatic Glucose Biosensor Based on Novel Gold Nanoparticles‐Bacteria Cellulose Nanofibers Nanocomposite

An exploration of gold nanoparticles–bacterial cellulose nanofibers (Au‐BC) nanocomposite as a platform for amperometric determination of glucose is presented. Two enzymes, glucose oxidase (GOx) and horseradish peroxidase (HRP) were immobilized in Au‐BC nanocomposite modified glassy carbon electrode at the same time. A sensitive and fast amperometric response to glucose was observed in the presence of electron mediator (HQ). Both of GOx and HRP kept their biocatalytic activities very well in Au‐BC nanocomposite. The detection limit for glucose in optimized conditions was as low as 2.3 µM with a linear range from 10 µM to 400 µM. The biosensor was successfully applied to the determination of glucose in human blood samples.     

Determination of trans,trans‐muconic acid in workers' urine through ultra‐performance liquid chromatography coupled to tandem mass spectrometry

A novel method for the biological monitoring of benzene‐exposed workers has been developed through ultra‐performance liquid chromatography coupled to tandem mass spectrometry. The method uses trans,trans‐muconic acid in urine as the benzene‐exposure biomarker. The method was developed using a triple quadrupole mass spectrometer with enough sensitivity to facilitate diluting and injecting the urine samples directly, rather than performing a solid‐phase extraction procedure as is common in the available protocols. Moreover, compared with a conventional high‐pressure liquid chromatography system, the separation power provided by the ultra‐performance liquid chromatography system allows a 10‐fold reduction in run time. The method was adjusted to a dynamic range of between 198.9 and 4916.7 µg/L to cover the biological exposure index of trans,trans‐muconic acid in urine. Also, the method demonstrated intra‐day and inter‐day precision at 98%, and accuracy within an acceptable range of 101 ± 8%. The method has been used to quantify various types of urine samples, such as workers' urine and inter‐laboratory proficiency tests. Depending on the sample, the quantified levels ranged from less than the limit of quantitation to 3836.7 µg/L. No levels exceeding the calibration range were detected in the urine of workers, and the reported concentrations in urine for the proficiency tests were, as expected, based on known values. Moreover, the new method using sample dilution and faster chromatographic run was more effective, facilitating fast communication of results, as needed, to decision‐makers. Copyright © 2012 John Wiley & Sons, Ltd.     

PDMS extraction bars for the determination of volatile aromatic hydrocarbons in water and wastewater

In this study, the preparation and application of extraction bars of PDMS were investigated to preconcentrate and determine benzene, toluene, ethylbenzene, and xylene in water and wastewater by means of HPLC with fluorescence detection. Aliquot samples from hospital wastewater were used as the model effluent. The independent variables for the sorptive extraction were as follows: ionic strength (added amounts of NaCl); pH; temperature and time of absorption; temperature and time of desorption. Under optimized conditions, by using a factorial design, the suspended extraction bars could allow the determination of benzene, toluene, ethylbenzene, and xylene (1.20 ± 0.05 μg/L; 10.40 ± 0.02 μg/L; 1.80 ± 0.04 μg/L; 15.9 ± 0.04 μg/L, respectively) in hospital effluent (fortified samples), by recoveries of 71.9 ± 4.9 to 74.8 ± 5.6%. This procedure represents an innovation that eliminates the time‐consuming stage of vacuum microfiltration, and allows the determination of volatile organic compounds by HPLC. As far as we know, this procedure is original and represents an important contribution to the field.     

Extractive Spectrophotometric Determination of Fluconazole by Ion-pair Complex Formation with Bromocresol Green

An extraction-spectrophotometric method for the determination of trace amounts of fluconazole was described. Fluconazole was effectively extracted as a 1 ： 1 ion-pair complex with bromocresole green （BCG） at pH 3.0 into chloroform, followed by spectrophotometric determination at 420 nm. Beer＇s law was obeyed over the range of 4-50 μg.mL^-1 of fluconazole with a detection limit of 3.7 μg.mL^-1 . The method is simple, rapid and sensitive. The procedure was applied to the determination of fluconazole in pharmaceutical preparations as well as its recovery from a blood serum sample.     

Infrared thermography analysis of the thermally latent polymerization of 3‐ethyl‐3‐phenoxymethyloxetane

Infrared thermography was employed to analyze multiple batches of the thermally latent polymerization of 3‐ethyl‐3‐phenoxymethyloxetane at once. The temperature changes in the polymerization depended on the polymerization rates. That is, a fast polymerization was exothermic, increasing the temporal temperature of the polymerization by approximately 130 °C within a few minutes. Infrared thermography, which can analyze multiple samples instantaneously, proved effective as a screening method for thermally latent curing systems. Exothermicity in the crosslinking polymerization of 1,4‐bis(3‐ethyloxetanylmethoxy)benzene was also analyzed by infrared thermography. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5519–5524, 2006