Claude Schummer

Comparison of MTBSTFA and BSTFA in derivatization reactions of polar compounds prior to GC/MS analysis

In this study, MTBSTFA and BSTFA, which are among the preferred derivatization reagents for silylation were both tested on derivatization of six different groups of polar chemicals to get information about usefulness in terms of sensitivity and specificity of both reagents. Tested compound groups were nitrophenols and methoxyphenols, sterols and sugars, dicarboxylic acids and hydroxylated polycyclic aromatic hydrocarbons. It was found that MTBSTFA-derivates produce characteristic fragmentation patterns presenting mainly the fragments [M](+), [M-57](+) and [M-131](+), of which [M-57](+) is generally dominant on the mass spectrogram. BSTFA-derivates mainly show the fragments [M](+), [M-15](+) and [M-89](+) whereof the molecular ion [M](+) is generally dominant. It was also found that steric hindrance and molecular mass play a very important role in the choice of the best suited derivatization reagent: compounds with sterically hindered sites derivatized with MTBSTFA produce very small analytical responses or no signal at all, and compounds with high molecular mass produce no characteristic fragmentation pattern when derivatization is performed with BSTFA. It was also found that MTBSTFA-derivatization facilitates separation of isomer analytes, suggesting its choice in combination to semi-polar columns, whilst BSTFA seems better for sterically hindered compounds. Findings were confirmed with applications of both reagents to biological and environmental matrices (urine and atmospheric aerosols).

Temporal variations of concentrations of currently used pesticides in the atmosphere of Strasbourg, France

Atmospheric samples have been collected in Strasbourg between April 18 and May 29, 2007 and were analyzed for 71 current-use pesticides, of which 38 were detected. Average concentrations ranged from 0.09 ng m(-3) for Fenarimol to 110.42 ng m(-3) for Dimethachlor, which was slightly higher than the concentrations reported from other, comparable agricultural regions. Significant temporal variations were observed for 30 pesticides, and for most of them it could be shown that these were linked to time, temperature or atmospheric pressure. In several cases this helped to identify pesticide application just before or at the beginning of the sampling period, or ongoing treatment. Humidity, in contrast to previous reports, could not be linked to these variations. For the other 8 pesticides, only very little temporal variations were observed. Generally, these concentrations were low (less than 1 ng m(-3)), and it was assumed that they are not in use in Alsace at present.

Multi-class pesticide analysis in human hair by gas chromatography tandem (triple quadrupole) mass spectrometry with solid phase microextraction and liquid injection.

A method for the simultaneous detection and quantification of 22 pesticides from different chemical classes was developed using solid-phase microextraction (SPME) and gas chromatography tandem (triple quadrupole) mass spectrometry. Pesticides were extracted from 50mg of pulverized hair with acetonitrile. The extract was submitted to two successive steps of direct immersion-SPME at 30°C and 90°C or to a liquid injection without SPME in order to obtain optimized conditions for each of the 22 analytes investigated. Validation parameters were significantly influenced by both the injection mode (SPME vs liquid injection) and the temperature of SPME. Limits of quantification ranged from 0.05 pg mg(-1) for trifluralin to 10 pg mg(-1) for pentachlorophenol. The application of the validated method to the analysis of samples collected from non-occupationally exposed volunteers demonstrated the presence of pesticides in all the samples tested. Altogether, 13 different analytes were detected at concentration above the limit of quantification.

Analysis of phenols and nitrophenols in rainwater collected simultaneously on an urban and rural site in east of France.

The behaviour of phenols and nitrophenols in the atmosphere is of concern for environmental research as these are known to be toxic to humans and wildlife. To increase the knowledge about these compounds, the concentrations of 20 phenols and nitrophenols in rainwater were studied in an urban (Strasbourg) and a rural (Erstein) site in Eastern France. The wet rain samples were collected on a weekly basis between January 2002 and July 2003, and analyzed for phenols and nitrophenols using SPME and gas chromatography coupled to mass spectrometry. The compounds were derivatized with MDBSTFA directly in the injection port of the gas chromatograph. Total concentrations ranged from 0 to 1383 microg L(-1) in Strasbourg and from 0 to 1215 microg L(-1) in Erstein. These concentrations are in the same range than those measured in other studies, but considerably higher than the concentrations measured for pesticides (about 10 times) and polycyclic aromatic hydrocarbons (about 1000 times) on the same sites and at the same period. Phenols, except for o-cresol, were generally less concentrated than nitrophenols. o-Cresol was one of the major compounds, probably due to its role as raw material in pesticide production. The concentrations of phenols and nitrophenols were found to vary with time. No seasonal trend was observed, but significant correlations with rainfall amount were identified.

Quantitative determination of ethyl glucuronide in sweat.

In this study, ethyl glucuronide (EtG), a specific metabolite of ethanol, was for the first time detected in sweat after alcohol consumption by human volunteers. Sweat was collected using a sweat patch (PharmChek). After collection, chemicals accumulated on the patch were extracted with water and extracts were purified by solid phase extraction. EtG was determined by gas chromatography with mass spectrometric detection in negative chemical ionization mode. In parallel, the amount of sodium deposited on the patch was determined by capillary electrophoresis and used as a correction factor to calculate the volume of sweat accumulated on the patch and, hence, the concentration of EtG in sweat. The EtG sweat concentration observed ranged from 1.7 to 103.0 μg/L for alcohol consumption from 38.0 to 154.6 g equivalent pure ethanol. No EtG was detected in subjects who did not consume alcohol. Our results demonstrate that after ethanol consumption, EtG is detectable in sweat collected using a sweat patch. The simultaneous determination of sodium allows the estimation of the volume of sweat accumulated on the patch and to calculate the concentration of EtG in sweat. This represents the first quantitative determination of a xenobiotic in sweat collected using a sweat patch. This study suggests that EtG determination in sweat could represent an interesting alternative to urine or serum analysis for the control of abstinence of patients included in treatment programs.

Determination of hydroxylated metabolites of polycyclic aromatic hydrocarbons in human hair by gas chromatography–negative chemical ionization mass spectrometry

The study describes the determination of mono-hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs), metabolites of PAHs, in human hair. Twelve selected OH-PAHs from two to four rings, generally determined in urine analysis, were investigated as markers of human exposure to PAHs. Following hydrolysis of hair specimens of 50-300 mg with 1M NaOH, OH-PAHs were extracted using dichloromethane and submitted to an optimized derivatization with (2S,4R)-N-heptafluorobutyryl-4-heptafluorobutoyloxy-prolyl chloride. Compounds were then analyzed using gas chromatography-negative chemical ionization mass spectrometry (GC-NCIMS). The average inter-day and intra-day variability was 12% and 17%, respectively. The average recovery was 52% and the limits of detection and quantification ranged from 20 and 66 pmol/g for 1-OH-phenanthrene (i.e., 3.9 and 12.8 pg/mg) to 311 and 1030 pmol/g for 2-OH-benzo(c)phenanthrene (i.e., 75.9 and 251 pg/mg). The influence of hair washing with water as decontamination step, and enzymatic treatment (beta-glucuronidase) to hydrolyze conjugated derivatives were also tested. The application of the developed method to the analysis of 30 hair specimens (17 from non-smoker and 13 from smoker volunteers) demonstrated inter-individual qualitative and quantitative variations. According to the easiness of hair sampling and based on the extended detection windows provided by hair analysis, this method is proposed as a new promising tool for the assessment of human chronic exposure to PAHs.

Application of XAD-2 resin-based passive samplers and SPME–GC–MS/MS analysis for the monitoring of spatial and temporal variations of atmospheric pesticides in Luxembourg

Passive air sampling has been shown to be a very interesting alternative to high-volume sampling by overcoming its disadvantages (size, weight, expensiveness). However, to date, only limited data is available about passive air sampling of current-use pesticides. In order to test if passive samplers allow monitoring of spatial and temporal variations of atmospheric pesticide concentrations, five XAD-2-resin based passive air samplers were deployed at five locations in Luxembourg. Samplers were analyzed using accelerated solvent extraction coupled to solid-phase microextraction and gas chromatography with tandem mass spectrometry. Collected data was used to study the spatial and temporal variations of the concentrations of the compounds. Twenty two pesticides were detected between March and October, while no pesticides were detected from November to February. Highest concentrations were measured on the rural sites, suggesting that the used XAD-2 resin-based passive samplers allow the simultaneous monitoring of multiple current-use pesticides and identifying spatial and temporal variations.

Simultaneous determination of nicotine and PAH metabolites in human hair specimen: a potential methodology to assess tobacco smoke contribution in PAH exposure.

The present methodology was developed to simultaneously assess chronic exposure to PAHs and to tobacco from the analysis of one hair specimen per examined individual. The method is a two step extraction of twelve mono-hydroxy-PAHs and of nicotine, and their separate analysis by optimized methods using gas chromatography-negative chemical ionization-mass spectrometry. After method validation and assessment of the hair decontamination procedure, 105 hair specimens from smokers and non-smokers were analyzed. All the hair samples tested positive for nicotine. Median concentration was 10.7ng/mg for smokers and 0.5ng/mg for non-smokers. 70% of the samples tested positive for OH-PAHs. The most common one was 2-naphthol (61%) and its concentration was significantly higher in smokers than in non-smokers (median: 111 vs 70pmol/g, p=0.006). 2-OH-benzo(c)phenanthrene and 6-OH-chrysene were only detected once in a non-smokers hair. The concentration of the sum of all PAH-metabolites ranged from 24 to 67190pmol/g (median: 118pmol/g). Only six samples tested positive for more than two different metabolites. The simultaneous detection of nicotine and OH-PAHs in hair is possible and provides reliable results. This represents a useful tool for the accurate biomonitoring of chronic exposure to PAH and correct identification of the sources of exposure.

Utilization of long duration high-volume sampling coupled to SPME-GC-MS/MS for the assessment of airborne pesticides variability in an urban area (Strasbourg, France) during agricultural application.

ABSTRACT Atmospheric samples have been collected between 14 March and 12 September 2012 on a 2-week basis (15 days of sampling and exchange of traps each 7 days) in Strasbourg (east of France) for the analysis of 43 pesticides. Samples (particle and gas phases) were separately extracted using Accelerated Solvent Extraction (ASE) and pre-concentrated by Solid Phase Micro-Extraction (SPME) before analysis by gas chromatography coupled to tandem mass spectrometry (GC-MS/MS). Four SPME consecutive injections at distinct temperatures were made in order to increase the sensitivity of detection for the all monitored pesticides. Currently used detected pesticides can be grouped in four classes; those used in maize crops (acetochlor, benoxacor, dicamba, s-metolachlor, pendimethalin, and bromoxynil), in cereal crops (benoxacor, chlorothalonil, fenpropimorph, and propiconazole), in vineyards (tebuconazole), and as herbicides for orchards, meadows of green spaces (2,4-MCPA, trichlopyr). This is in accordance with the diversity of crops found in the Alsace region and trends observed are in accordance with the period of application of these pesticides. Variations observed permit also to demonstrate that the long time sampling duration used in this study is efficient to visualize temporal variations of airborne pesticides concentrations. Then, long time high-volume sampling could be a simple method permitting atmospheric survey of atmospheric contamination without any long analysis time and consequently low cost.