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New fully automated gas chromatographic analysis of urinary S-phenylmercapturic acid in isotopic dilution using negative chemical ionization with isobutane as reagent gas
Abstract
The determination of urinary S‐phenylmercapturic acid (S‐PMA) represents the most reliable biomarker to monitor the intake risk of airborne benzene. Recently, the European CHemical Agency (ECHA) deliberate new occupational exposure limits for benzene, recommended a S‐PMA Biological Limit Value of 2 μg/g creatinine. This limit is an order of magnitude lower than the previous one and its determination constitutes a challenge in the analytical field. We developed and validated a method, that allows the fully‐automated and sensitive determination of S‐PMA by the use of gas‐chromatography negative chemical ionization tandem mass spectrometry in isotopic dilution. For NCI we selected a mixture of 1% isobutane in argon as reactive gas, by studying its chemical ionization mechanism and optimal parameters compared to pure isobutane or pure methane. This gas mixture produces a more abundant signal of the target analyte than isobutane or methane and it extended the operative lifetime of the ion source, enabling us to start an high throughput approach of the S‐PMA anlysis. Moreover, energy resolved mass spectrometry experiments were carried out to refine the MS/MS analysis conditions, testing nitrogen and argon as collision gas. The method optimization was pursued by a chemometrich model by using the experimental design. The quantification limit for S‐PMA was 0.10 μg/L. Accuracy (between 98.3% to 99.6 %) and precision (ranging to 1.6% to 6.4%) were also evaluated. In conclusion, the newly developed assay represent a powerfull tool for the robust, reliable and sensitive quantification of urinary S‐PMA and, due to its automation, it is well suited for application in large environmental and biological monitoring.
... U-B was quantified by the m/z 78 ion. 10-50-250-2500 ng/mL SPMA analysis was performed by on-sample derivatization and direct immersion (DI) SPME with a Varian 3900/MS 320 triple quadrupole (TQ) GC-MS/MS, using 1% isobutane in an argon gas mixture for negative chemical impact; the GC-MS/MS system was equipped with a Flex x,y,z autosampler (EST Analytical, Fairfield, Ohio) equipped with a six-position MFX and devices as previously described [25,26]. The aliquot of 1 mL of sample was transferred into a 20-mL vial, added with 10-µL of internal standard solution ( 13 C 6 -SPMA, Giotto Biotech, Prato, Italy), and then placed into the autosampler. ...
... The routine procedure is acidifying the urine to pH < 1 to convert pre-SPMA to SPMA [27]. After agitation, 215 µL of 0.1 M KOH (Merck KGaA) solution was added to adjust the pH to 8. Ultrasound-assisted derivatization of the SPMA with 2,3,4,5,6-pentafluorobenzyl bromide solution (Merck KGaA) was carried out [25]. Finally, the 20-mL sample vial was filled with 18 mL of water, and the DI-SPME extraction was carried out using a 65-µm FFA-PDMS/DVB (Merck KGaA) temperature-controlled agitation at 60 • C for 20 min. ...
Airborne benzene in workplaces has progressively decreased due to preventive actions and the redesigning of facility processes. Professionals who assess occupational exposure should select techniques to detect benzene levels comparable to ambient air exposure. Thus, sensitive biomarkers are needed to discriminate the effects of confounding factors, such as smoking or sorbic acid (SA). In order to identify sensitive biomarkers and to study their correlation with confounding factors, 23 oil refinery workers were enrolled in the study; their airborne benzene exposures and biomarkers were monitored. Urinary benzene (U-B), t,t-muconic acid (t,t-MA), and S-phenylmercapturic acid (SPMA) were quantified. Urinary cotinine (U-C) and t,t-sorbic acid (t,t-SA) were evaluated to flag smoking and SA intake, respectively. The benzene measured in personal inhalation sampling ranged from 0.6 to 83.5 (median 1.7) µg/m3. The concentration range of the biomarkers, U-B, t,t-MA, and SPMA, were 18–4893 ng/m3, <10–79.4 µg/g creatinine, and <0.5–3.96 µg/g creatinine, respectively. Pearson tests were carried out; the best correlations were between airborne benzene and U-B (µg/L r = 0.820, p < 0.001) and between benzene and SPMA (g/L r = 0.812, p < 0.001), followed by benzene and t,t-MA (mg/L r = 0.465, p = 0.039). From our study, U-B and SPMA result to be the most reliable biomarkers to assess the internal number of low doses of benzene exposure, thanks to their specificity and sensitivity.
... . Solid-phase microextraction methods are developed to extract occupational indicators such as phenylmercapturic acid(Dugheri et al., 2020), cadmium, mercury and lead(Akkaya et al., 2017;Baile et al., 2018), 2,5-haxanedione, styrene and toluene.The most common fibers used were polydimethylsiloxane (PDMS), PDMS-divinylbenzene (DVB), Carboxen (CAR)/PDMS, polarpolyacrilate, and MIP. Other fibers such as CW/DVB, diethoxydiphenylsilane ...
The application of green microextraction techniques (METs) is constantly being developed in different areas including pharmaceutical, forensic, food and environmental analysis. However, they are less used in biological monitoring of workers in occupational settings. Developing valid extraction methods and analytical techniques for the determination of occupational indicators plays a critical role in the management of workers’ exposure to chemicals in workplaces. Microextraction techniques have become increasingly important because they are inexpensive, robust and environmentally friendly. This study aimed to provide a comprehensive review and interpret the applications of METs and novel sorbents and liquids in biological monitoring. Future perspectives and occupational indicators that METs have not yet been developed for are also discussed.
... What is more, GC is considered as a cheaper and green alternative to HPLC because of its relatively low operational costs and the use of inert gases such as He, Ar, and N 2 instead of toxic organic solvents in the mobile phase composition. [120,121] However, analytes must be volatile to carry out gas chromatographic analysis. Since b-blockers are not volatile, optimization of the time-and labor-consuming derivatization procedure is generally required before analysis. ...
β-blockers are among the most prescribed drugs and frequently recommended in patients with hypertension, angina, myocardial infarction, arrhythmias, and heart failure. Additionally, since β-blockers cause low anxiety, they are abused by athletes in branches where aiming is important. β-blocker residues may be present in environmental samples due to high consumption. At this point, the development of sensitive, rapid, and reliable analytical methods is very important for determination of β-blockers in different matrices. Among all the analytical methods, chromatographic methods are used in a wide range for the determination of β-blockers as they enable simultaneous determination of many analytes and removal of interfering components. Electrochemical methods, which usually do not require any pretreatment process, have become important due to their reliability, high specificity, and fast response. Simple and rapid optical methods can be used in laboratories where modern and expensive instruments such as high-performance liquid chromatography or gas chromatography are not available. The objective of this review is to provide an overview of the analytical methods for determination of β-blockers in pharmaceuticals, biological fluids, and environmental samples. Some selected studies for the determination of β-blockers published in the last decade are discussed. Furthermore, current trends and future perspectives on β-blocker analyses are also suggested.
In the last decade, the development and adoption of greener and sustainable microextraction techniques have been proved to be an effective alternative to classical sample preparation procedures. In this review, 10 commercially available solid-phase microextraction systems are presented, with special attention to the appraisal of their analytical, bioanalytical, and environmental engineering. This review provides an overview of the challenges and achievements in the application of fully automated miniaturized sample preparation methods in analytical laboratories. Both theoretical and practical aspects of these environment-friendly preparation approaches are discussed. The application of chemometrics in method development is also discussed. We are convinced that green analytical chemistry will be really useful in the years ahead. The application of cheap, fast, automated, “clever”, and environmentally safe procedures to environmental, clinical, and food analysis will improve significantly the quality of the analytical data.
High-throughput screening of samples is the strategy of choice to detect occupational exposure biomarkers, yet it requires a user-friendly apparatus that gives relatively prompt results while ensuring high degrees of selectivity, precision, accuracy and automation, particularly in the preparation process. Miniaturization has attracted much attention in analytical chemistry and has driven solvent and sample savings as easier automation, the latter thanks to the introduction on the market of the three axis autosampler. In light of the above, this contribution describes a novel user-friendly solid-phase microextraction (SPME) off- and on-line platform coupled with gas chromatography and triple quadrupole-mass spectrometry to determine urinary metabolites of polycyclic aromatic hydrocarbons 1- and 2-hydroxy-naphthalene, 9-hydroxy-phenanthrene, 1-hydroxy-pyrene, 3- and 9-hydroxy-benzoantracene, and 3-hydroxy-benzo[a]pyrene. In this new procedure, chromatography’s sensitivity is combined with the user-friendliness of N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide on-fiber SPME derivatization using direct immersion sampling; moreover, specific isotope-labelled internal standards provide quantitative accuracy. The detection limits for the seven OH-PAHs ranged from 0.25 to 4.52 ng/L. Intra-(from 2.5 to 3.0%) and inter-session (from 2.4 to 3.9%) repeatability was also evaluated. This method serves to identify suitable risk-control strategies for occupational hygiene conservation programs.
The intensive use of pesticides such as herbicides, insecticides, fungicides and acaricides has been lead to ubiquitous contamination, being present not only in soils, water bodies and/or crops, but also in the atmosphere. Considering the massive amount of pesticides employed globally, together to their persistence, this may be an important concern regarding air quality and human health worldwide. In the present study we developed a green sensitive sample preparation method for determination of nine organophosphates, two pyrethroids, one carbamate, and one strobirulin in PM2.5 collected in a tropical coastal area in the Southern Hemisphere for the first time. Extraction of PM2.5 sample masses, as low as 206 µg, were performed in a miniaturized device using 500 μL of a mixture containing 18% acetonitrile in dichloromethane followed by sonication for 23 minutes and injection into GC-MS. A total of 12 pesticides were identified and quantified successfully, among them, eight banned pesticides. A risk assessment exposure and cancer risk for possible carcinogenic pesticides (bifenthrin, malathion, parathion and permethrin) were performed for exposure of adults, children and infants. Hazard Quotient and cumulative exposure for organophosphate and pyrethroid pesticides were less than 1, showing that cumulative risk is within acceptable range.
Computational Fluid Dynamics (CFD) has consolidated as a tool to provide understanding and quantitative information regarding many complex environmental flows. The accuracy and reliability of CFD modelling results oftentimes come under scrutiny because of issues in the implementation of and input data for those simulations. Regarding the input data, if an approach based on the Reynolds-Averaged Navier-Stokes (RANS) equations is applied, the turbulent scalar fluxes are generally estimated by assuming the standard gradient diffusion hypothesis (SGDH), which requires the definition of the turbulent Schmidt number, Sct (the ratio of momentum diffusivity to mass diffusivity in the turbulent flow). However, no universally-accepted values of this parameter have been established or, more importantly, methodologies for its computation have been provided. This paper firstly presents a review of previous studies about Sct in environmental flows, involving both water and air systems. Secondly, three case studies are presented where the key role of a correct parameterization of the turbulent Schmidt number is pointed out. These include: (1) transverse mixing in a shallow water flow; (2) tracer transport in a contact tank; and (3) sediment transport in suspension. An overall picture on the use of the Schmidt number in CFD emerges from the paper.
This paper reports the first contribution to the determination of the hexahydrophthalic anhydride in unsaturated polyester resins by automated head space/solid-phase micro extraction and gas chromatography/mass spectrometry analysis. After a preliminary reaction of the acid anhydride with water to form carboxylic acids, a rapid on-sample derivatization using trimethyloxonium tetrafluoroborate was used. A new autosampler platform was proposed in this study by using the Multi Fiber Exchange device. The limits of detection for one mg of unsaturated polyester resin were 2.9 pg for the cis-1,2-cyclohexanedicarboxylic acid and 8.0 pg for trans-1,2-cyclohexanedicarboxylic acid, whereas the limits of quantification were 14.5 and 29.7 pg, respectively. The equilibrium and kinetics of this substance vs solid-phase microextraction are theoretically evaluated and discussed.
As a reagent gas for positive- and negative-mode chemical ionization mass spectrometry (CI-MS), isobutane (i-C4H10) produces superior analyte signal abundance to methane. Isobutane has never been widely adopted for CI-MS because it fouls the ion source more rapidly and produces positive CI spectra that are more strongly dependent on reagent gas pressure compared with methane. Isobutane was diluted to various concentrations in argon for use as a reagent gas with an unmodified commercial gas chromatograph-mass spectrometer. Analyte spectra were directly compared using methane, isobutane, and isobutane/argon mixtures. A mixture of 10% i-C4H10 in argon produced twice the positive-mode analyte signal of methane, equal to pure isobutane, and reduced spectral dependence on reagent gas pressure. Electron capture negative chemical ionization using 1% i-C4H10 in argon tripled analyte signal compared with methane and was reproducible, unlike pure isobutane. The operative lifetime of the ion source using isobutane/argon mixtures was extended exponentially compared with pure isobutane, producing stable and reproducible CI signal throughout. By diluting the reagent gas in an inert buffer gas, isobutane CI-MS experiments were made as practical to use as methane CI-MS experiments but with superior analytical performance. Graphical Abstractᅟ
The general problem of heat exchange, including heat exchanger design, heat conduction analysis, convective heat transfer, and thermal radiation are discussed. (N.G.G.)
Response sarfxe methodology (RSM) is a collection of tools developed in the 1950s for the purpose of determining optimum operating conditions in applications in the chemical industry. This article reviews the progrrss of RSM in the general areas of experimental design and analysis and indicates how its role has been affected by advanccs in other fields of applied statistics. Current areas of research in RSM are highlighted. and areas for future research are discussed.
Background:
Smoking tobacco preparations in a water pipe (hookah) is widespread in many places of the world and is perceived by many as relatively safe. We investigated biomarkers of toxicant exposure with water pipe compared with cigarette smoking.
Methods:
We conducted a crossover study to assess daily nicotine and carcinogen exposure with water pipe and cigarette smoking in 13 people who were experienced in using both products.
Results:
When smoking an average of 3 water pipe sessions compared with smoking 11 cigarettes per day (cpd), water pipe use was associated with a significantly lower intake of nicotine, greater exposure to carbon monoxide (CO), and a different pattern of carcinogen exposure compared with cigarette smoking, with greater exposure to benzene, and high molecular weight polycyclic aromatic hydrocarbon (PAH), but less exposure to tobacco-specific nitrosamines, 1,3-butadiene, acrolein, acrylonitrile, propylene oxide, ethylene oxide, and low molecular weight PAHs.
Conclusions:
A different pattern of carcinogen exposure might result in a different cancer risk profile between cigarette and water pipe smoking. Of particular concern is the risk of leukemia related to high levels of benzene exposure with water pipe use.
Impact:
Smoking tobacco in water pipes has gained popularity in the United States and around the world. Many believe that water pipe smoking is not addictive and less harmful than cigarette smoking. We provide data on toxicant exposure that will help guide regulation and public education regarding water pipe health risk.
As a result of the greater consciousness within the analytical community on the impact of chemicals on human health and environment, green issues are increasingly taken into account when choosing an established analytical method or developing a new one. Apart from typical analytical characteristics (e.g., sensitivity, limit of detection, repeatability, etc.), other features such as the amount of sample/ reagents, operation time, use of energy-effective apparatus, waste production, etc. should be highlighted in order to meet the principles of Green Chemistry. Although conventional approaches for trace element analysis by atomic spectrometry usually involve well-established sample pre-treatments based on 'wet chemistry', and high consumption of gases, reagents, etc. is inherent to many techniques in this group, there are still many avenues where green issues can be implemented. For greening atomic spectrometry, green chemistry principles should be applied to every step of the analytical process, i.e., from sampling and sample pre-treatment to data processing. In this review, main pathways for greening atomic spectrometry such as downsizing of instrumentation, use of portable instruments, solid sampling, application of clean energies (ultrasound, microwaves, etc.) for sample pre-treatment, development of on-site, on-line and at-line approaches vs. typical off-line methods, application of modern extraction techniques (e.g., solid-and liquid-phase microextraction), green solvents and derivatization agents and use of chemometric tools for method optimization, signal processing, etc. are discussed in a critical way.
The present research is focused on automation, miniaturization, and system interaction with high throughput for multiple and specific Direct Immersion-Solid Phase Microextraction/Fast Gas Chromatography analysis of the urinary ketones. The specific Mass Spectrometry instrumentation, capable of supporting such the automated changeover from Negative Chemical to Electron Ionization mode, as well as the automation of the preparation procedure by new device called MultiFiber Exchange, through change of the fibers, allowed a friendly use of mass spectrometry apparatus with a number of advantages including reduced analyst time and greater reproducibility (2.01-5.32%). The detection limits for the seven ketones were less than 0.004 mg/L. For an innovative powerful meaning in high-throughput routine, the generality of the structurally informative Mass Spectrometry fragmentation patterns together with the chromatographic separation and software automation are also investigated.
Analysis of plasma nonesterified fatty acids (NEFA) by gas-liquid chromatography requires procedures that are both lengthy and cumbersome. A 45-min direct methylation procedure was carried out at 24-29 degrees C on 150 microliter of plasma added with an internal standard in 5.0 ml of methanol-acetyl chloride 50:1 (v/v). To stop the reaction, 3 ml of 6.0% K2CO3 was added. After addition of 150 microliter of hexane, shaking and centrifugation, an aliquot of the upper phase was injected into the gas chromatograph. The specificity of the methylation reaction for NEFA without hydrolysis of other classes of plasma lipids was substantiated with appropriate standards. This one-step specific methylation procedure is superior to currently used methods.
Introduction
Mercapturic acids are urinary metabolites of occupational and environmental toxicants. The aim of this work was to develop and validate an analytical assay for the determination of several urinary mercapturic acids to be used as biomarkers of exposure.
Method
An isotope dilution tandem mass spectrometric method, coupled with reversed-phase liquid chromatography, was developed for the analysis of mercapturic acids derived from several compounds, including those of benzene, toluene, 1,3-butadiene, styrene, acrylonitrile, 4-chloronitrobenzene, acrylamide, acrolein, propylene oxide, N,N-dimethylformamide, crotonaldehyde, ethylene oxide, and methylating and ethylating agents. Samples were prepared by simple filtration after dilution. A validation was carried out, including the assessment of calibration curves, sensitivity, accuracy, precision, process efficiency, and stability, along with external verification. The assay was applied to the analysis of 14 end-of-shift urine samples from unexposed workers and gasoline station attendants.
Results
The chromatographic run lasted 18 min. Limits of quantitation ranged from 0.01 to 3.2 μg/L; precision, expressed as relative standard deviation, ranged from 0.6 to 20.9%; and accuracy ranged from 93.4 to 114.9% of theoretical values. The use of deuterated internal standards was suitable for control of the matrix effect. The assay allowed the simultaneous quantitation of urinary mercapturic acids at different concentration ranges. The external verification exercise produced good results. The application of the assay to urine samples from workers revealed differences in mercapturic acid profiles in agreement with the expected patterns of exposure.
Conclusion
This high-throughput method is valid and useful for the quantitation of urinary mercapturic acids, and is suitable for human biomonitoring of occupational and environmental exposure.
A new highly sensitive and environmentally friendly analytical method, using low-temperature partition extraction and ultra high performance liquid chromatography with tandem mass spectrometry, without the use of a labeled analyte, was developed and validated to determine and quantify urinary S-phenylmercapturic acid in urine samples. The World Health Organization, in its guidelines for air quality in Europe, recognizes that benzene is carcinogenic to humans and there is no safe level of exposure. Urinary S-phenylmercapturic acid is a sensitive and specific biological marker of exposure to benzene. The new analytical method, extraction and analysis, were linear in the working range between 0.1 and 200.0 μg L(-1) , precise (relative standard deviation lower than 6.0%), accurate (97.0-105.0%) and sensitive. The method limits of detection and quantification were 0.02 and 0.084 μg L(-1) , respectively. The recovery with the low temperature partition extraction was 96.1%, with relative standard deviation less than 3.8%. The method is simple, accurate and reproducible, and has been successfully applied in the evaluation of non occupational exposure to benzene, by urinary S-phenylmercapturic acid in urine samples. This article is protected by copyright. All rights reserved.
Pentafluorobenzyl bromide (PFB-Br) is a versatile derivatization agent. It is widely used in chromatography and mass spectrometry since several decades. The bromide atom is largely the single leaving group of PFB-Br. It is substituted by wide a spectrum of nucleophiles in aqueous and non-aqueous systems to form electrically neutral, in most organic solvents soluble, generally thermally stable, volatile, strongly electron-capturing and ultraviolet light-absorbing derivatives. Because of these greatly favoured physicochemical properties, PFB-Br emerged an ideal derivatization agent for highly sensitive analysis of endogenous and exogenous substances including various inorganic and organic anions by electron capture detection or after electron-capture negative-ion chemical ionization in GC-MS. The present article attempts an appraisal of the utility of PFB-Br in analytical chemistry. It reviews and discusses papers dealing with the use of PFB-Br as the derivatization reagent in the qualitative and quantitative analysis of endogenous and exogenous inorganic anions in various biological samples, notably plasma, urine and saliva. These analytes include nitrite, nitrate, cyanide and dialkyl organophosphates. Special emphasis is given to mass spectrometry-based approaches and stable-isotope dilution techniques.
The third generation of aminobiphenyl palladacycle pre-catalyst "G3-Xantphos" enables functionalization of peptides containing cysteine in high yields. The conjugation (bioconjugation) occurs chemoselectively at room temperature under biocompatible conditions. Extension of the method to protein functionalization allows selective bioconjugation of the trastuzumab antibody.
Roger Phan-Tan-Luu was Professor at the University Paul Cezanne of Marseille, France. In 1970, he founded the Laboratory of Methodology of Experimental Research in which he developed both the methodological approach and the algorithms that enable construction of efficient designs. He was at the start of the establishment of trainings about the Methodology of Experimental Research in several universities and industries in France and abroad. He is author and co-author of numerous scientific articles dealing with experimental designs. He belongs to the scientific committees of several international congresses. In 1992, Roger Phan-Tan-Luu was awarded Doctor Honoris Causa of the University of Umeå (Sweden).
A new approach is proposed for the selection of reagent ion species in a gas chromatography-chemical ionization mass spectrometry (GC-PICI-MS) method for GBL and 1,4-BD determination, the two "prodrugs" of gamma-hydroxybutyric acid (GHB), a drug associated with sexual assault. The GC-PICI-MS is often the best technique to avoid an extended fragmentation occurring in EI source and it preserves the information on molecular ions. Ion-trap mass spectrometry (IT-MS) is a valuable tool in chemical ionization experiments, commonly affording reaction times 104-105 higher than those in conventional CI sources. This feature allows the use of either vapors from liquid reagents, or many reactant species that are difficult to generate and employ in the conventional CI experiments. In this research acetone, acetonitrile, methanol and diethylamine were evaluated to generate vapors of the chemical ionization species. The use of liquid CI reagent offers a wide range of chemical-physical properties that can greatly affect the specificity, with the possibility to modulate the detection of the analyte in comparison with background or matrix interferences. The experimental data using different CI liquid reagents and reaction times were compared through calibration curves of GBL and 1,4-BD (ranging from 10 to 1000 ng/mL). The linear regression curves obtained were used to calculate the sensitivity (slope) and limit of detection (LOD) of the method. Methanol resulted in the most efficient reagent for the determination of studied analytes. However, its employment as ionization agent of the 1,4-BD favors the hydride abstraction mechanism or hydrogen loss from protonated-molecule ions. These phenomena can be considered as a possible sources of uncertainty or errors. Therefore, acetonitrile can be employed as a good compromise between sensitivity and reliability of signal for both analytes.
Dialkyl phosphates are organophosphate insecticide metabolites and their urinary analysis is useful for assessing human exposure to these compounds. This study presents a sample preparation method with microwave-assisted derivatization for two dialkyl phosphates to make the process faster before gas chromatographic analysis. The optimized conditions for derivatization procedure were: 250 μL of 2,3,4,5,6-pentafluorobenzyl bromide 3% in acetonitrile for derivative; microwave for 5 min with intensity of 160 W. The electron ionization mass spectrometric analysis was performed using a gas chromatography with mass spectrometry QP-2010 from the Shimadzu(®) equipped with RTx(®) -5MS capillary column. Ions were monitored at selected-ion monitoring mode at m/z 350 for diethyl thiophosphate and m/z 366 for diethyl dithiophosphate. The developed method was linear for both metabolites. The intra-assay precision was the values ranged between 1.1 to 9.1%, for diethyl thiophosphate, and between 4.06 to 6.9%, for diethyl dithiophosphate. The interassay precision showed relative standard deviation between 10.3 and 15.1%, for diethyl thiophosphate and between 4.9 to 11.9%, for diethyl dithiophosphate. The results obtained suggests that derivatization assisted by microwave, before gas chromatography with mass spectrometry analysis, can be applied to monitoring of exposure to organophosphates once is fast, sensible and precise method to determinate dialkyl phosphates. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Mercapturic acids (MAs) are metabolic end products formed from conjugates between glutathione and electrophilic compounds. MAs are, therefore, suitable biomarkers of exposure to toxicants, which are either electrophiles by themselves or metabolized to electrophilic intermediates. We developed and validated two LC-MS/MS methods which allow the complementary, rapid, and sensitive determination of MAs derived from acrolein, acrylamide, acrylonitrile, benzene, 1,3-butadiene, crotonaldehyde, N,N-dimethylformamide, ethylene, ethylene oxide, vinyl chloride, propylene oxide, styrene, toluene as well as methylating and ethylating agents. Since separate determinations of single or small groups of MAs are time-consuming and expensive, we multiplexed several individual methods into two LC-MS/MS methods covering 18 individual mercapturic acids. Method validation according to FDA guidelines showed excellent results in terms of robustness, accuracy, and sensitivity of the methods. Moreover, the use of a minimal, simple, and straightforward sample cleanup procedure further accelerated the analytical workflow, which allows a time- and cost-efficient analysis of up to 18 MAs derived from various toxicants in environmental levels. The methods were applied to urine samples derived from a strictly diet-controlled clinical study, including 25 smoking and 25 non-smoking subjects. Significant increase in the urine concentrations in smokers as compared to non-smokers (p < 0.01; Student t test) was observed for 13 individual MAs. Moreover, a dose dependence was obtained for the majority of the analytes. In conclusion, the newly developed assays represent a powerful tool for the fast and reliable quantification of 18 MAs in clinical studies. A first method application suggests several suitable biomarkers for nine relevant toxicants in tobacco smoke.
Various ionization methods including positive chemical ionization (PCI), negative chemical ionization (NCI) and electron impact (EI) were used to study the mass spectra of TNT. Methane, isobutane and ammonia were used as the CI reagent gases. The mass spectrometric quantitation in this study was performed by selected ion monitoring (SIM), with sample introduction via a short capillary column and a solids probe. The best TNT detection limit (ca. 0.020 ng) was obtained with the NCI-SIM technique with isobutane as a reagent gas.
Nitrogen- and sulfur-containing alkyl homologues of indole, carbazole, benzocarbazoles, benzothiophene, dibenzothiophene, and tribenzothiophenes are identified and quantified in fractionated catalytically cracked heavy gas oils. Four boiling fractions, 500 degree to 600 degree F, 600 degree to 700 degree F, 700 degree to 800 degree F, and 800 degree to 900 degree F, are analyzed by isobutane chemical ionization (CI) gas chromatography/mass spectrometry (GC/MS) and GC techniques in which nitrogen and sulfur selective detectors are employed. The total nitrogen and the total sulfur values obtained by organic elemental analysis are included for comparison. Comparison of quantitative results obtained by the three different techniques shows excellent agreement.
Acrylonitrile, acrolein, 1,3-butadiene, benzene, and crotonaldehyde are hazard volatile organic compounds in tobacco smoke, which can be metabolized to mercapturic acids (MAs) excreted in urine. MAs are can be regarded as important and specific biomarkers to evaluate exposure to those carcinogenic volatile organic compounds. A simultaneous determination of N-acetyl-S-2-cyanoethyl-cysteine (CEMA), 3-hydroxypropyl)-l-cysteine (3-HPMA), N-acetyl-S-(3,4-dihydroxybutyl)-l-cysteine (DHBMA), N-acetyl-S-(phenyl)-l-cysteine (SPMA) and 3-hydroxy-1-methylpropylmercapturic acid (HMPMA) derived from five volatile organic compounds by column-switching LC-MS/MS has been described. MAs were concentrated and cleaned up by an online reusable pre-column packed with restricted access material. The intra- and inter-day precisions of the method ranged from 0.7% to 15.2%. The LODs was 0.013-0.053ng/mL. The recovery of the whole analytical procedure ranged from 79.3% to 116%. After validation, this method was successfully applied to urine samples from smokers (n=246) and nonsmokers (n=58). The results showed MAs in urine from smokers were significantly higher than that in nonsmoker except for SPMA. Urinary CEMA significantly correlated with 3-HPMA (r=0.763, P<0.0001) and HMPMA (r=0.910, P<0.0001). CEMA, 3-HPMA and HMPMA are potential biomarkers to distinguish the differences between smokers and nonsmokers.
Wearable solid phase microextraction (SPME) devices consisting in necklaces and pins were developed for the environmental monitoring of ketamine in recreational places using ionic liquid as coating. SPME fibers obtained using both monocationic and dicationic polymeric ionic liquids were characterized in terms of morphology, film thickness, thermal stability and pH resistance. An average thickness of 30±5μm, an excellent thermal stability until 350°C and a very good fiber-to-fiber and batch-to-batch repeatability with RSD lower than 4% were some of the features of the developed coatings. A quantitation limit (LOQ) of 0.05mg/m(3) with a sampling time of 1min proved the feasibility of the developed method for the quantitation of ketamine in air at low concentration levels. Finally, the capabilities of the fibers for the rapid SPME sampling of ketamine in recreational places were proved obtaining extraction efficiencies at least two-fold higher than those obtained using commercial devices and extraction recoveries ranging from 84.2±3.3% to 93.6±2.6% (n=3).
The relative efficiencies of various monatomic and polyatomic gases when cast in the dual role of electron energy moderation and collisional stabilisation of excited ions have been assessed quantitatively by sensitivity measurements using so-called negative chemical ionisation conditions and controlled ionisation chamber gas densities and temperatures. With reference to the two chemical probes used in this study, viz. anthraquinone and bis(N,N-di-ethyldithiocarbamato)nickel(II), the nine gases examined can be ranked in order from the least to the most effective in maximising the degree of electron attachment as follows: He < Ne ∼ N2 < CH4 ∼ Ar ∼ Kr < Xe < i-C4H10 < CO2. Interpretation of these results has been achieved in terms of the respective abilities of the gases in the processes of elastic scattering of electrons, collisional stabilisation of negative ions and resonance scattering of electrons.
A new, rapid air sampling methodology using adsorptive solid phase microextraction (SPME) fiber coatings and non-equilibrium conditions was developed for volatile organic compounds (VOCs). This method is the fastest extraction-based technique for air sampling at typical airborne VOC concentrations. A theoretical model for the extraction was formulated based on the diffusion through the interface between the sampled (bulk) air and the SPME coating. Parameters that affect the extraction process through the interface including sampling time, air velocity, air temperature and relative humidity were investigated with the porous (solid) PDMS/DVB and Carboxen/PDMS coatings. Very short sampling times from 5 s to 1 min were used to minimize the effects of competitive adsorption and to calibrate the extraction process in the initial linear extraction region. The predicted amounts of extracted mass compared well with the measured amounts of target VOCs. Findings presented in this study extend the existing fundamental knowledge related to air sampling with porous SPME coatings, thereby enabling the development of new sampling devices for the rapid sampling of air, headspace, water and soil.
The chief chemical problems in the use of desorption or direct chemical ionization mass spectrometric techniques are that underivatized nonvolatile samples often undergo thermal adsorption/decomposition or give ions corresponding to dehydration products. Adsorption/decomposition effects can be abolished in many instances by appropriate techniques, but it is not possible to prevent dehydration for compounds containing easily eliminated hydroxyl groups when the usual protonating reagent gases are used. Parent MH+ ions are missing from mass spectra under these circumstances. The addition of a volatile amine to the gas phase will lead to molecular adduct ion formation in many instances of this kind. The mass spectra of ketones, acids, and esters show stable molecular adduct ions which are formed by covalent bonding of the amines. Some compounds containing hydroxyl groups alone will also form molecular adduct ions with a shared proton structure. When the twin-ion technique is used with pyridine-pyridine-d5, adduct ions containing a stable isotope label are easily recognized. The formation of covalently bonded stable isotope labeled molecular adduct ions may prove to be a useful way of determining molecular mass for many nonvolatile compounds other than macromolecules.
Mathematical descriptions of the absorption and desorption processes were developed and compared with experimental results for solid-phase microextraction (SPME) using poly(dimethylsiloxane)-coated fused silica optical fibers. Extraction times for benzene, toluene, and p-xylene using a coating thickness of 55 μm are under 10 min and can be shortened substantially using agitation. Detection limits and distribution coefficients for several organic compounds are presented. 20 refs., 13 figs., 1 tab.
Despite the presence of the ions at m/z 242 and m/z 243 in the electron ionization (EI) and chemical ionization (CI) mass spectra of tetryl, respectively, no such daughter ions were observed in the collision-induced dissociation spectra of the M+· ion in EI and of the [M+H]+ ion in CI. This supports the thesis that these ions are formed through hydrolysis of tetryl to N-methylpicramide in the ion source before ionization. It was found that the hydrolysis is considerably stronger under CI consitions, but can be minirnized in EI. The structure of the molecular ion at m/z 242 in the EI mass spectrum of N-methylpicramide was found to be similar to that of the [MH-NO2]+ ion in the CI mass spectrum of tetryl.
Nitroaromatic compounds (NACs) are important anthropogenic chemicals, which may enter all areas of the environment in significant amounts. Once there, they may be transformed, mainly via redox reactions. Most NACs and their transformation products are rather toxic, both in humans and ecosystems, and they are especially known for their carcinogenic potential. Thus, input and detrimental effects of NACs make environmental surveillance necessary, which in turn requires selective, sensitive, unbiased and robust methods suitable for the analysis of complex mixtures. These requirements are mainly fulfilled by the combination of an enrichment step with chromatographic separation and use of an appropriate detector. Official methods today use liquid–liquid extraction (LLE) or solid-phase extraction (SPE), followed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection, or gas chromatography (GC) with electron capture detection (ECD). These methods are widely established and have been thoroughly tested in interlaboratory comparisons. However, new methods for extraction, separation and detection are emerging, which are superior in terms of the required characteristics, and thus may replace the existing methods in the future. Both standard methods and new developments for the environmental analysis of NACs are discussed in this article. Regarding the references given, priority was given to the most recent developments, and thus about 70% of the cited literature is less than five years old.
The determination of acidic pharmaceutical and endocrine disrupting compounds at low ng/L levels in surface and wastewater requires highly selective and sensitive analytical procedures. Therefore, the water samples under study were prepared by means of solid phase extraction (SPE) for analyte enrichment and clean up. Prior to GC-NCI-MS, the polar analytes were derivatized using pentafluorobenzyl bromide. The performance of this analytical method has been revealed in fortification experiments by limits of detection ranging from 0.01 to 0.2 ng/L for, e. g., ibuprofen and 17α-ethinylestradiol, respectively. SPE may be the most rate determining step of the analytical procedure. Therefore, the performance of SPE disks and cartridges was additionally compared. Method evaluation demonstrated that even complex sample matrices, such as model wastewater or even synthetic humic acids, did not interfere with the quantification and identification of target analytes. The performance of the analytical method developed for water monitoring was further emphasized by the investigation of surface water of the River Saale and effluents of the wastewater treatment plant (WWTP) at Halle, Saxony-Anhalt, Germany. In those samples, acidic pharmaceuticals and corresponding metabolites occurred at 0.1 ng/L for clofibric acid up to 498 ng/L for bezafibrate. Technical nonylphenol and bisphenol A were found in every water sample. Meanwhile, 17α-ethinylestradiol was determined only in one WWTP effluent sample at 1 ng/L.
The aim of this study is to validate isotope-dilution electrospray ionization tandem mass spectrometry (ESI–MS–MS) method with a dual-loop cleanup device for simultaneous quantitation of two benzene metabolites, trans, trans-muconic acid (ttMA) and S-phenylmercapturic acid (SPMA), in human urine. In this study, a pooled blank urine matrix from rural residents was adopted for validation of the analytical method. The calibration curve, detection limit, recovery, precision, accuracy and the stability of sample storage for the system have been characterized. Calibration plots of ttMA and SPMA standards spiked into two kinds of urine matrixes over a wide concentration range, 1/32–8-fold biological exposure indices (BEIs) values, showed good linearity (R > 0.9992). The detection limits in pooled urine matrix for ttMA and SPMA were 1.27 and 0.042 μg g−1 creatinine, respectively. For both of ttMA and SPMA, the intra- and inter-day precision values were considered acceptable well below 25% at the various spiked concentrations. The intra- and inter-day apparent recovery values were also considered acceptable (apparent recovery >90%). The ttMA accuracy was estimated by urinary standard reference material (SRM). The accuracy reported in terms of relative error (RE) was 5.0 ± 2.0% (n = 3). The stability of sample storage at 4 or −20 °C were assessed. Urinary ttMA and SPMA were found to be stable for at least 8 weeks when stored at 4 or −20 °C. In addition, urine samples from different benzene exposure groups were collected and measured in this system. Without tedious manual sample preparation procedure, the analytical system was able to quantify simultaneously ttMA and SPMA in less than 20 min.
Phase-transfer catalysis (PTC) has been a well-established technique on the synthesis of organic chemicals for more than three decades. Its scope and underlying mechanistic features have been the subject of numerous studies and appear to be recognized and understood.This review is intended to approach the subject by focusing on the extraction–preconcentration–derivatization/reaction prior to analysis and to chronicle recent progress made. We present the salient aspects of PTC modes followed by a brief review of mechanistic considerations including reaction mechanisms, selectivity, rates and kinetics pointing out to the potency of PTC in analytical chemistry. Specific guidelines are given on how to optimize a PTC-based analysis with respect to catalyst, solvent, reaction conditions and more, based on reaction characteristics.Finally, using the PTC principles as a framework, selected real-life applications are provided, the capabilities and limitations of PTC are addressed for the purpose of direct analysis of organic analytes and certain advantages are highlighted.
Gas chromatography in combination with electron capture negative ion mass spectrometry (GC/ECNI-MS) is a sensitive method for the determination of polybrominated compounds in environmental and food samples via detection of the bromide ion isotopes m/z 79 and 81. The standard reagent gas for inducing chemical ionization in GC/ECNI-MS is methane. However, the use of methane has some drawbacks as it promotes carbonization of the filament and ion source. In this study, we explored the suitability of nitrogen as reagent gas for the determination of brominated flame retardants (polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), allyl-2,4,6-tribromophenyl ether (ATE) and 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE)) and halogenated natural products (for instance, methoxylated tetrabrominated diphenylethers and polybrominated hexahydroxanthene derivatives). An ion source temperature of 250 degrees C and a nitrogen pressure of 7 Torr in the ion source gave the highest response for m/z 79 and 81 of virtually all investigated polybrominated compounds. Using these conditions, nitrogen-mediated GC/ECNI-MS usually gave higher sensitivity than the method with methane previously used in our lab. In addition, the ion source was not contaminated to the same degree and the lifetime of the filament was significantly increased. Moreover, the response factors of the different polybrominated compounds with the exception of 2,4,6-tribromophenol were more uniform than with methane. Nitrogen is available at very high purity at relatively low price.
In benzene metabolism, pre-S-phenylmercapturic acid (pre-SPMA) is the precursor to S-phenylmercapturic acid (SPMA). Urinary pre-SPMA/SPMA ratios are variable. For the determination of urinary SPMA as a biomarker of exposure to benzene it is essential to completely convert pre-SPMA to SPMA. We developed a procedure for the enrichment and determination of urinary pre-SPMA by LC-MS/MS which allowed us to trace the conversion of pre-SPMA to SPMA. Complete conversion was found upon treatment of urine with HCl (37%) at pH 1.1. Previously reported treatment of urine with concentrated H(2)SO(4) was found to yield SPMA levels higher than after HCl treatment. The origin of that extra SPMA amount is unknown. In conclusion, our findings suggest that pre-treatment of urine with HCl to adjust the pH to 0.5-1 is essential for complete conversion of pre-SPMA to SPMA and should be applied prior to analysis of SPMA in urine.
Capillary column isobutane chemical ionization was found to be an excellent method for the mass spectral characterization of mustard, other sulfur vesicants and related compounds. Interpretation of [M + H]+ and fragmentation ion information afforded by this technique enabled the identification of many previously unreported mustard impurities. The developed methodology was applied to the analysis of an Iran/Iraq soil sample suspected to have been contaminated with mustard. Mustard and 17 other mustard related impurities were identified and characterized in this sample under electron impact and isobutane chemical ionization conditions.
The CI spectra obtained with i-C//5H//1//2 as the reagent gas are frequently very simple and provide abundant (M plus H)** plus ions for compounds more basic than i-C//5H//1//0. The i-C//5H//1//2 spectra are similar to i-C//4H//1//0 CI spectra but may contain somewhat fewer fragment ions and frequently more molecular ions, M** plus , from charge exchange by the relatively abundant i-C//5H//1//0** plus ion. In addition, i-C//5H//1//2 may be somewhat more selective than i-C//4H//1//0. One advantage of using i-C//5H//1//2 is the east by which the vapor may be introduced without a complex vacuum manifold.
Several reagent gases and mixed reagent gases for high pressure ion–molecule reaction ionization of samples have been investigated for use in gas chromatography-mass spectrometry analyses. The common g.c. carrier gases and their mixtures with other gases such as isobutane, ammonia, tetramethylsilane, hexafluoroacetone and nitric oxide, were studied. These reagents were used to enhance the molecular ion intensity and to simplify the spectra of steroidal alcohols and the trimethylsilyl ethers of biologically important compounds.
The isobutane chemical ionization (CI) mass spectra of forty-eight commonly used drugs have been measured. The majority of these give only an MH+ ion which can be used to identify the compound. In a few cases, the fragmentation of the MH+ ion is observed and can be rationalized in terms of simple acid-catalyzed reactions. Examples of the use of this technique in the identification of drugs taken in overdose quantities by patients admitted to a local hospital are provided.