Negative Chemical Ionization Mode Research Articles

Gas chromatography/negative chemical ionization mass spectrometry of transfluthrin in rat plasma and brain.

Transfluthrin is a relatively non-toxic rapid-acting synthetic pyrethroid insecticide. It is widely used in household and hygiene products. A sensitive and accurate bioanalytical method is required for quantification of its concentration in plasma and its potential target organ, the brain for studies to assess its health effects and toxicokinetics in mammals. The samples were prepared by liquid-liquid extraction. Gas chromatography mass spectrometry (GC/MS) analysis was performed for the determination of transfluthrin in biological samples with an overall method run time of 15min. Transfluthrin was quantified using selected-ion monitoring (SIM) in the negative chemical ionization (NCI) mode. Chromatographic separation was achieved using a Zebron® ZB5-MS GC column operating with 1mL/min constant flow helium. Cis-Permethrin was used as the internal standard. The method was validated to be precise and accurate within the linear range of 1.0-400.0ng/mL in plasma and 4.0-400.0ng/mL in brain homogenate, based on a 100μL sample volume for both matrices. This method was applied to samples following administration of a 10mg/kg oral dose to male adult rats. The plasma concentrations were observed to be 11.70±5.69ng/mL and brain concentrations 12.09±3.15ng/g when measured 2h post-dose. A rapid GC/NCI-MS method was demonstrated to be sensitive, specific, precise and accurate for the quantification of transfluthrin in rat plasma and brain. The optimized method was successfully used to quantify the rat plasma and brain concentrations of transfluthrin 2h after the oral dosing of Sprague-Dawley rats.

Pyrethroids in chicken eggs from commercial farms and home production in Rio de Janeiro: Estimated daily intake and diastereomeric selectivity

In this study, pyrethroids were determined in chicken eggs from commercial farm (n = 60) and home egg production (n = 30). These pyrethroids were investigated: bifenthrin, phenothrin, permethrin, cyfluthrin, cypermethrin and fenvalerate, including most diastereomers. Quantification was done using GC-MS in a negative chemical ionization mode. Pyrethroids residues were found in 79% of the analyzed samples. Cypermethrin presented the highest occurrence, being quantified in 62 samples (69%) in concentrations (lipid weight – l w.) varying between 0.29 and 6408 ng g−1, followed by phenothrin (24%), 21–3910 ng g−1, permethrin (14%), 2.96–328 ng g−1, and bifenthrin (11%), 3.77–16.7 ng g−1. Cyfluthrin and fenvalerate were not detected. Home-produced eggs had a higher occurrence of pyrethroids (97%), with a greater predominance of phenothrin. In commercial production, 70% of the samples presented pyrethroid residues (predominantly cypermethrin). This is the first report about the presence of pyrethroids in home-produced eggs and the first description of a selectivity pattern with the predominance of cis diastereomers in chicken eggs. In general, estimated daily intake does not present a risk to human consumption, according to Brazilian and international standards (FAO/WHO). However, one third of the samples (30 eggs) had concentrations above the maximum residue limits (MRLs). The maximum cypermethrin concentration was 66 times the MRL, while the maximum phenothrin concentration was 11 times the limit. Further studies about transfer dynamics, bioaccumulation and metabolic degradation of stereoisomers are required, as well as determining if this selectivity pattern in food can increase consumer's health risk.

Medium-Chain Chlorinated Paraffins (CPs) Dominate in Australian Sewage Sludge.

To simultaneously quantify and profile the complex mixture of short-, median-, and long-chain CPs (SCCPs, MCCPs, and LCCPs) in Australian sewage sludge, we applied and further validated a recently developed novel instrumental technique, using quadrupole time-of-flight high resolution mass spectrometry running in the negative atmospheric pressure chemical ionization mode (APCI-qTOF-HRMS). Without using an analytical column the cleaned extracts were directly injected into the qTOF-HRMS followed by quantification of the CPs by a mathematical algorithm. The recoveries of the four SCCP, MCCP and LCCP-spiked sewage sludge samples ranged from 86 to 123%. This APCI-qTOF-HRMS method is a fast and promising technique for routinely measuring SCCPs, MCCPs, and LCCPs in sewage sludge. Australian sewage sludge was dominated by MCCPs with concentrations ranging from 542 to 3645 ng/g dry weight (dw). Lower SCCPs concentrations (<57–1421 ng/g dw) were detected in the Australian sewage sludge, which were comparable with the LCCPs concentrations (116–960 ng/g dw). This is the first time that CPs were reported in Australian sewage sludge. The results of this study gives a first impression on the distribution of the SCCPs, MCCPs, and LCCPs in Australia wastewater treatment plants (WWTPs).

Optimization of a microwave-assisted extraction procedure for the determination of selected alkyl, aryl, and halogenated phenols in sewage sludge and biosolids

A microwave-assisted extraction method for the determination of 15 alkyl, aryl, and halogenated phenols in sewage sludge and biosolids samples was developed and optimized. The effects of solvent, temperature, time, moisture content, acid, and number of extractions on the recovery of phenols were evaluated. Results indicated that extraction solvent had the greatest impact on the recovery of all phenols while pH had the largest effect on recovery of hexachlorophene and pentachlorophenol. Wet sludge samples were extracted with acetone-hexane mixture in the presence of glacial acetic acid. The extract was evaporated, acetylated by acetic anhydride and cleaned up by silica gel. For dry sludge samples, an optional procedure for the simultaneous extraction and acetylation of phenols was also proposed. Triclosan (TCS) and the alkyl and aryl phenols in sludge extracts were analyzed by gas chromatography-mass spectrometry (GC-MS) in electron-impact mode while polyhalogenated phenols were analyzed by GC-MS in negative ion chemical ionization mode. Method detection limits were ca. 200 ng/g for nonylphenol, &amp;lt;25 ng/g for TCS and other alkyl and aryl phenols, and &amp;lt;5 ng/g for other halogenated phenols. This method has been applied to the determination of phenolic compounds in over 150 sludge and biosolids samples since 2009.

Methodology for trace analysis of 17 pyrethroids and chlorpyrifos in foodstuff by gas chromatography-tandem mass spectrometry.

This study aimed to develop an efficient, sensitive, and reliable analytical method for trace analysis of 17 different pyrethroids and chlorpyrifos in the fatty content of animal products, including beef, chicken, eggs, fish, and milk. The method developed is based on an ultrasound extraction using lyophilized samples, a solid phase extraction cleanup with basic alumina and C18 cartridges in tandem, and analysis by gas chromatography coupled to tandem mass spectrometry in negative chemical ionization mode. Recovery values were in the range of 27-128% with relative standard deviation always below 25%, and chiral analysis of recovery data showed predominance of isomers of cis form over trans. Limits of detection (LODs) ranged from 0.002 to 6.43ngg-1 lipid weight (lw), and limits of quantification (LOQs) ranged between 0.006 and 21.4ng g-1lw. The developed methodology was used for the analysis of 25 samples of fatty foods. All samples were positive for at least one of the pesticides, chlorpyrifos, bifenthrin, cyhalothrin, permethrin, cypermethrin, or deltamethrin, with mass fraction levels ranging from 0.03 to 270ng g-1 lw. Graphical Abstract ᅟ.

Screening of nerve agent markers with hollow fiber-chemosorption of phosphonic acids.

This report describes a method developed for extracting nerve gas markers such as phosphonic acids from urine and other aqueous samples. It involves single-step microextraction with chemosorption to hollow fibers that have been pre-soaked in a solution containing a derivatization reagent (3,5 triflouro methyl benzene diazomethane). The derivatives it forms with phosphonic acids can be sensitively detected by mass spectrometric detectors operating in negative chemical ionization (NCI) mode. Limits of quantification obtained in analyses of water and urine extracts by GC/MS in negative chemical ionization and selected ion monitoring mode were 0.1-10 and 0.5-10ng/mL, respectively. Pentaflourophenyl diazomethane can also be used as a derivatization reagent, and the micro-extracts (which generate low background signals) can be sensitively analyzed by GC-MS/MS in NCI selected reaction monitoring (SRM) mode, using two specific transitions for both reagents. Thus, this sensitive approach can be flexibly modified to obtain confirmatory information, or address potential problems caused by interferences in some samples.

Analysis of tetrahydroxylated benzo[a]pyrene isomers in hair as biomarkers of exposure to benzo[a]pyrene.

A first gas chromatography-tandem mass spectrometry (GC-MS/MS) method was designed for analysis of four tetrahydroxylated benzo[a]pyrene metabolites (benzo[a]pyrene-r-7,t-8,t-9,c-10-tetrahydrotetrol, benzo[a]pyrene-r-7,t-8,t-9,t-10-tetrahydrotetrol, benzo[a]pyrene-r-7,t-8,c-9,c-10-tetrahydrotetrol, and benzo[a]pyrene-r-7,t-8,c-9,t-10-tetrahydrotetrol) in hair. Hair powder extract was submitted to liquid-solid extraction, followed by C18 solid-phase purification. The analytes were derivatized with use of N-methyl-N-(trimethylsilyl)trifluoroacetamide and then analyzed by GC-MS/MS in negative chemical ionization mode. The calibration curve was linear from the limit of quantification (LOQ) to 20 pg/mg in hair. The coefficient of determination of the calibration curve was more than 0.975 for all the analytes investigated. The LOQs ranged from 0.075 to 0.2 pg/mg in hair. The method was afterward applied to the analysis of hair of 16 rats randomly allocated to experimental groups receiving 16 polycyclic aromatic hydrocarbons solubilized in oil at 0 or 0.8 mg/kg body weight by oral administration three times per week for 90 days. The analysis of monohydroxylated and dihydroxylated benzo[a]pyrenes was conducted in parallel by GC-MS/MS on the same samples. All tetrahydroxylated benzo[a]pyrene isomers were detected in hair samples collected from rats exposed to polycyclic aromatic hydrocarbons. Benzo[a]pyrene-r-7,t-8,t-9,c-10-tetrahydrotetrol, the most abundant isomer in hair of treated rats, was also the principal isomer released in DNA adduct hydrolysis in humans. Moreover, the benzo[a]pyrene-r-7,t-8,t-9,c-10-tetrahydrotetrol concentrations in hair were significantly greater than those of 2-hydroxybenzo[a]pyrene, 1-hydroxybenzo[a]pyrene, 7-hydroxybenzo[a]pyrene, and 4-hydroxybenzo[a]pyrene and similar to those of 9-hydroxybenzo[a]pyrene and 3-hydroxybenzo[a]pyrene. The method was also sufficiently sensitive to monitor environmental levels of exposure because two hair specimens in the eight analyzed from smokers were above the LOQ for benzo[a]pyrene-r-7,t-8,t-9,c-10-tetrahydrotetrol and benzo[a]pyrene-r-7,t-8,c-9,t-10-tetrahydrotetrol. This study therefore demonstrated that tetrahydroxylated benzo[a]pyrenes in hair might be a useful biomarker for the assessment of both the general population and occupationally exposed workers.

A cadmium(II)-based metal-organic framework material for the dispersive solid-phase extraction of polybrominated diphenyl ethers in environmental water samples

In this study, a stable cadmium(II)-based metal-organic framework (MOF) material was designed and used as a sorbent for the dispersive solid-phase extraction (dSPE) of polybrominated diphenyl ethers (PBDEs) in environmental water samples. Gas chromatography coupled with triple quadrupole mass spectrometer (GC–MS/MS), working in the negative chemical ionization mode, was used to quantify the target analytes. Characterization of the material was performed by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), elementary analyses (EA) and thermogravimetric analyses (TGA). The synthesized rod shape MOF is on the micro level in size and has excellent chemical and solvent stability. The extraction conditions, including the extraction time, temperature and ionic strength, were examined systematically using response surface methodology (RSM). Under optimized conditions, the method that was developed showed an excellent extraction performance. Good linearity (R2>0.99) within the concentration range of 0.25–250ngL−1 was obtained. Low limits of detection (0.08–0.15ngL−1, signal-to-noise ratio=3:1) and good precision (relative standard deviation <12%, n=6) were achieved. The developed method was applied to analyze natural and spiked environmental water samples.

Gas phase ion chemistry of coumarins: ab initio calculations used to justify negative chemical ionization trends

The gas phase ion chemistry of coumarins using electron ionization (EI), positive chemical ionization (PCI) and negative chemical ionization (NCI) in a time of flight and quadrupole mass spectrometer (qMS) coupled to a gas chromatograph is outlined. The observations in NCI mode were complimented with Ab initio calculations. This was because NCI gave enhanced signals in contrast to EI and PCI and therefore could serve as a potential ionization method for quantitative analysis. For the two classes of analytes that were examined here, i.e. methyl and acetyl coumarin derivatives, experimental data showed that the methyl derivatives underwent dissociative electron capture to produce ions of the type [M–H]¯ while the acetyl derivatives underwent resonance electron capture to produce ions of the type M˙¯. The M˙¯ type of ions were more intense than the earlier. Ab initio calculations showed higher electron affinities in the acetyl than the methyl derivatives. KEY WORDS : Coumarins, Ab Initio calculations, Electron ionization, Positive chemical ionization, Negative chemical ionization Bull. Chem. Soc. Ethiop. 2015 , 29(3), 473-484. DOI: http://dx.doi.org/10.4314/bcse.v29i3.15

Oxidative stress: Determination of 4-hydroxy-2-nonenal by gas chromatography/mass spectrometry in human and rat plasma

The lipid peroxidation product 4-hydroxynonenal (HNE) is a biomarker of oxidative stress which is essentially involved in the pathophysiology of many diseases. The analysis of HNE is challenging because this aldehyde is extremely reactive and thus unstable. Hence, we adopted a gas chromatography–mass spectrometry (GC–MS) method based on derivatization of HNE with pentafluorobenzylhydroxylamine–HCl followed by trimethylsilylation to trimethylsilyl ethers. Ions representative for a negative ion chemical ionization mode were recorded at m/z = 152 for HNE and at m/z = 162 for the deuterated analogon (HNE-d11) as internal standard. This excellent stable and precise GC–MS method was carefully validated for HNE, and showed good linearity (r2 = 0.998), and high specificity and sensitivity. Within-day precisions were 4.4–6.1% and between-day precisions were 5.2–10.2%. Accuracies were between 99% and 104% for the whole calibration range (2.5–250 nmol/L) of HNE.To examine the versatility of this modified GC–MS method, we analyzed HNE in ethylenediaminetetraacetic acid (EDTA) plasma in a well-defined collective of migraine patients; recently published. The results underline our former observations that women with migraine are afflicted with increased levels of HNE. Patients with thyroidal dysfunction showed no significant HNE alterations. This was confirmed by normal HNE EDTA plasma levels in hyper- und hypothyroid Sprague-Dawley rats.Taken together, the GC–MS method presented herein is of excellent quality to record oxidative stress-related bioactive HNE levels. This is important for a reorientation of oxidative stress analytics in other human diseases first of atherosclerosis and cancer.

Multi-residue analysis of pesticides in traditional Chinese medicines using gas chromatography-negative chemical ionisation tandem mass spectrometry

In this study, a residue analysis method for the simultaneous determination of 107 pesticides in traditional Chinese medicines (TCMs), Angelica sinensis, A. dahurica, Leonurus heterophyllus Sweet, Pogostemon cablin and Lonicera japonica Thunb., was developed using gas chromatography coupled with tandem mass spectrometry in negative chemical ionisation mode (GC-NCI-MS/MS). NCI has advantages of high sensitivity and selectivity to chemicals with electron-withdrawing groups, and yields low background interference. For sample preparation, QuEChERS (quick, easy, cheap, effective, rugged and safe) was applied. Due to the unique characteristics of TCMs, the clean-up step was optimised by adjusting amounts of primary secondary amine, C18, graphitised carbon black and silica sorbents. Validation was mainly performed by determining analyte recoveries at four different spiking concentrations of 10, 50, 100 and 200 ng g−1, with seven replicates at each concentration. Method trueness, precision, linearity of calibration curves, lowest calibrated levels (LCLs) and matrix effects were determined to demonstrate method and instrument performance. Among the 107 pesticides tested, approximately 80% gave recoveries from 80% to 110% and < 10% relative standard deviation (RSD). The LCLs for nearly all pesticides were 5 ng g−1, and as low as 0.1 ng g−1 for dichlofenthion, endosulfan sulphate, flumetralin, isofenphos-methyl, methyl-pentachlorophenyl sulphide and trifluralin. The results indicate that GC-NCI-MS/MS is an excellent technique for quantitative and qualitative analysis of targeted GC-amenable pesticides at ultra-trace levels, especially in complex matrices such as TCMs.

Regulated bioanalysis of conformers - A case study with ASP2151 in dog plasma and urine.

We developed and validated bioanalytical methods for a potent helicase-primase inhibitor ASP2151 that has two conformers. These conformers elute as unseparated broad peaks under ordinary high-performance liquid chromatographic conditions, indicating discernable differences in hydrophobicity. We observed that column temperature and mobile phase pH have no effect on these peaks and that conformers form a single symmetrical peak when tetrahydrofuran is added to the mobile phase. In addition, we needed to develop semi-automated methods where inter-conversion of the conformers is unlikely to cause sample-to-sample extraction variability. Briefly, following the addition of deuterium-labeled ASP2151 as an internal standard (IS), dog plasma samples or acetonitrile-added urine samples were filtrated. The filtrates were then injected into a column-switching liquid chromatography-tandem mass spectrometry (LC-MS/MS) system and trapped onto an extraction column. Extracts were back-flushed onto an analytical C18 column (4.6×50mm, 3μm) with a mobile phase consisting of methanol, tetrahydrofuran, and 20mmol/L ammonium acetate (45:5:50, v/v/v). The eluent was monitored in the negative atmospheric pressure chemical ionization mode. The calibration curve was linear over a range of 5-1000ng/mL for plasma and 0.5-100μg/mL for urine. Validation data met the acceptance criteria in accordance with regulatory guidance and demonstrated that these methods were selective, accurate, and reproducible. In addition, the present methods were successfully applied to a pharmacokinetic study in dogs.

Tandem mass spectrometry and density functional theory of RDX fragmentation pathways: Role of ion-molecule complexes in loss of NO3 and lack of molecular ion peak.

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is an explosive compound that finds a wide range of military and civilian applications. RDX has been a target in environmental matrices by gas chromatography/tandem mass spectrometry (GC/MS/MS). MS/MS in negative chemical ionization (NCI) mode of RDX provides important fragmentation patterns that are useful for structural elucidation. The fragmentation patterns are needed for proper identification of precursor and product ions in analytical methods that depend on MS/MS approaches for a reliable identification of RDX. This study focuses on the MS fragmentation mechanisms of RDX in NCI mode using both MS/MS and density functional theory (DFT). The DFT studies were performed at the B3LYP/6-311G(d,p) level of theory. The DFT results showed that NCI of RDX leads to the formation of an anion-molecule complex that was energetically more stable than the RDX anion. The fragmentation proceeds through two pathways, leading to the loss of NO(2) and NO(3). The loss of NO(3) takes place in an anion-molecule complex leading to the formation of characteristic nitroso group fragment ions. Using the fragmentation schemes, important ion structures are proposed including structures for m/z 160, 129, 102, and 86. The results demonstrate the importance of both charge-induced and charge-remote dissociations in RDX pathways. The ion structures identified along the pathways could be used as targets in analytical methods for reliable identification purposes.

Negative chemical ionization gas chromatography coupled to hybrid quadrupole time-of-flight mass spectrometry and automated accurate mass data processing for determination of pesticides in fruit and vegetables.

Gas chromatography coupled to high resolution hybrid quadrupole time-of-flight mass spectrometry (GC-QTOF MS), operating in negative chemical ionization (NCI) mode and combining full scan with MSMS experiments using accurate mass analysis, has been explored for the automated determination of pesticide residues in fruit and vegetables. Seventy compounds were included in this approach where 50% of them are not approved by the EU legislation. A global 76% of the analytes could be identified at 1μgkg(-1). Recovery studies were developed at three concentration levels (1, 5, and 10μgkg(-1)). Seventy-seven percent of the detected pesticides at the lowest level yielded recoveries within the 70%-120% range, whereas 94% could be quantified at 5μgkg(-1), and the 100% were determined at 10μgkg(-1). Good repeatability, expressed as relative standard deviation (RSD <20%), was obtained for all compounds. The main drawback of the method was the limited dynamic range that was observed for some analytes that can be overcome either diluting the sample or lowering the injection volume. A home-made database was developed and applied to an automatic accurate mass data processing. Measured mass accuracies of the generated ions were mainly less than 5ppm for at least one diagnostic ion. When only one ion was obtained in the single-stage NCI-MS, a representative product ion from MSMS experiments was used as identification criterion. A total of 30 real samples were analyzed and 67% of the samples were positive for 12 different pesticides in the range 1.0-1321.3μgkg(-1).

Development of a Multiresidue Method for the Analysis of 33 Organochlorine Pesticide Residues in Fatty and High Water Content Foods

A new multiresidue method has been developed and validated for the determination of 33 organochlorine pesticides (OCPs) in various fatty and high water content food matrices. The OCP residues in foods were extracted with matrix solid-phase dispersion and cleaned up with gel permeation chromatography and Florisil solid-phase extraction. The instrumental determination was carried out by a gas chromatograph coupled to a single quadrupole mass spectrometer (MS) with runtime of 11 min. Besides, negative chemical ionization mode was also studied and evaluated for OCPs’ sensitivities. The optimized MS was operated in electron ionization mode and acquiring three selected ions per target compound. The method was validated with various food samples, including edible oil, meat, seafood, eggs, coffee, tree nuts, fruits, vegetables, etc. according to SANCO/12571/2013. An adequate linear relationship was obtained in the studied concentration range (0.5–10.0 μg kg−1) in sample; the average spiked recovery values were in the range 70–120 % for the two levels of concentration studied in samples: 0.5 and 2.0 μg kg−1. Precision values, expressed as relative standard deviation, were lower than 18 % at aforementioned spiking levels; detection limits and quantification limits were below or equal to 0.1 and 0.5 μg kg−1, respectively. Moreover, certified reference materials were used to assess the accuracy of the developed method. Finally, the developed method was successfully applied for the OCPs’ determination in real samples for the first Hong Kong Total Diet Study.

High-sensitivity elemental ionization for quantitative detection of halogenated compounds.

The rising importance of organohalogens in environmental, pharmaceutical, and biological applications has drawn attention to analysis of these compounds in recent years. Elemental mass spectrometry (MS) is particularly advantageous in this regard because of its ability to quantify without compound-specific standards. However, low sensitivity of conventional elemental MS for halogens has hampered applications of this powerful method in organohalogen analyses. To this end, we have developed a high-sensitivity elemental ion source compatible with widely available atmospheric-sampling mass spectrometers. We utilize a helium-oxygen plasma for atomization followed by negative ion formation in plasma afterglow, a configuration termed as plasma-assisted reaction chemical ionization (PARCI). The effect of oxygen on in-plasma and afterglow reactions is investigated, leading to fundamental understanding of ion generation processes as well as optimized operating conditions. Coupled to a gas chromatograph, PARCI shows constant ionization efficiency for F, Cl, and Br regardless of the chemical structure of the compounds. Negative ionization in the afterglow improves halide ion formation efficiency and eliminates isobaric interferences, offering sub-picogram elemental detection for F, Cl, and Br using low-resolution MS. Notably, the detection limit for F is about one order of magnitude better than other elemental MS techniques. The high sensitivity and facile adoptability of PARCI pave the way for combined elemental-molecular characterization, a comprehensive analytical scheme for rapid identification and quantification of organohalogens.

Determination of 2-, 3-, 4-methylpentanoic and cyclohexanecarboxylic acids in wine: Development of a selective method based on solid phase extraction and gas chromatography-negative chemical ionization mass spectrometry and its application to different wines and alcoholic beverages

A method to analyse 2-methylpentanoic, 3-methylpentanoic and 4-methylpentanoic acids as well as cyclohexanecarboxylic acid has been developed and applied to wine and other alcoholic beverages. Selective isolation with solid phase extraction, derivatization with 2,3,4,5,6-pentafluorobenzyl bromide at room temperature for 30minutes, and further analysis by gas chromatography-mass spectrometry in negative chemical ionization mode provides detection limits between 0.4 and 2.4ng/L. Good linearity up to 3.6μg/L, satisfactory reproducibility (RSD<10%) and signal recovery of around 100% represent a robust method of analysis. Concentration data of these analytes in wine and other alcoholic beverages are reported for the first time. The levels found ranged from the method detection limits to 2630ng/L, 2040ng/L and 3810ng/L for 2-, 3- and 4-methylpentanoic acids, respectively, and to 1780ng/L for cyclohexanecarboxylic acid. There are significant differences depending on the type of wine or beverage. Distilled beverages, beer and aged wines have higher contents in methylpentanoic and cyclohexanecarboxylic acids.

Gas chromatographic determination of ethyl glucuronide in hair: Comparison between tandem mass spectrometry and single quadrupole mass spectrometry

Ethyl glucuronide (EtG), a minor metabolite of ethanol, accumulates in hair and is currently used as a long-term marker for the detection of chronic and excessive alcohol consumption. Sensitive methods are required to differentiate teetotalers from moderate drinkers according to the established cut-off (i.e., 7pg/mg hair). The aim of this study was to develop a sensitive method using gas chromatography coupled to tandem mass spectrometry (GC–MS/MS) operated in the negative ion chemical ionization (NICI) mode. The validated method was applied to hair samples from teetotalers, moderate and excessive alcohol consumers, and results were compared to a previously validated GC–NICI–MS method. The developed GC–NICI–MS/MS method showed linearity over a range from 2 to 400pg/mg hair, with a limit of detection (LOD) of 0.05pg/mg hair and a lower limit of quantification (LLOQ) of 0.2pg/mg hair, compared to an LOD of 0.5pg/mg hair and LLOQ of 1.5pg/mg hair obtained with GC–NICI–MS. Furthermore, lower background noise was observed using GC–NICI–MS/MS. Comparison of results of hair samples (n=58) obtained by GC–NICI–MS and GC–NICI–MS/MS showed no significant difference between both methods (paired-sample t-test, p>0.05; mean CV=1.0%). The differences between both methods were larger for EtG concentrations<30mg/pg hair (mean CV=1.7%) than for EtG concentrations>30mg/pg hair (mean CV=0.7%). This suggests a higher selectivity of GC–NICI–MS/MS at lower concentrations. In conclusion, by using GC–NICI–MS/MS, a higher analytical selectivity and an improved signal to noise ratio, can be achieved. Although GC–NICI–MS would not change the interpretation of the EtG concentrations, the present GC–NICI–MS/MS method should preferentially be used for the determination of EtG in hair, especially when differentiating between teetotalers and moderate drinkers according to the current cut-off (i.e., 7pg/mg hair).

O14: Alcohol consumption vs. hair EtG concentration in alcohol dependent individuals: Role of gender differences

Introduction Ethyl glucuronide (EtG), a minor alcohol metabolite, accumulates in hair and is proposed as a stable marker for the detection of excessive alcohol consumption above a cut-off level of 30 pg/mg hair. A correlation between drinking behavior and EtG hair concentrations is observed, but variability exists, which could partially be explained by gender differences. Aims To investigate (1) the correlation between alcohol consumption and hair EtG in alcohol dependent patients, and (2) the effect of gender differences on this correlation. Methods The first 0–3 cm hair segments were analyzed using gas chromatography mass spectrometry (GC-MS) in negative ion chemical ionization (NICI) mode. Detailed retrospective alcohol consumption was obtained on a day per day basis over the last 3 months using the Timeline Follow Back Interview in alcohol dependent individuals starting an alcohol detoxification program. Results Thirty-six Caucasian alcohol dependent individuals (25 males/11 females; mean age 45 ± 8 years; mean BMI 25 ± 6) participated. Median alcohol consumption over the last three months (90 days) was 13050 g alcohol (range 65 – 650 g alcohol/ day). Hair EtG concentrations varied between 32 pg/mg hair and 662 pg/mg hair. There was a good linear and positive correlation between hair EtG and the amounts of alcohol consumed (Pearson r = 0.83; p r = 0.82; p r = 0.78; p = 0.005). Conclusions Our data confirm the good linear correlation between hair EtG and amounts of alcohol consumed, extending findings to alcohol dependent individuals. Additionally, we show that gender differences do not play a crucial role in the interpretation of hair EtG values for evaluating the amounts of alcohol consumed. As a result, no separate cut-off values are necessary for male and female alcohol abusers. These findings should be replicated in recreational alcohol consumers to assess possible gender differences in the interpretation of lower hair EtG values.

AN EVALUATION OF THE DETERMINABILITY OF LOW LEVEL DIOXIN CONCENTRATIONS BY HRGC/LRMS-NCI

High resolution gas chromatography coupled with high resolution mass spectrometry systems are often used for the analyses of dioxins at low concentrations in environmental sample matrices such as soil, vegetation, sediment, air and food. Since the construction and operation costs of these systems are so expensive, the most of the laboratories in the developing countries haven’t the systems with high resolution mass spectrometry. Thus, cheaper systems with similar sensitivity such as high resolution gas chromatography coupled with low resolution mass spectrometry systems in negative chemical ionization mode may be beneficial to assess the dioxin pollution levels in environmental samples before the elaborate studies on dioxin contamination and stochastic risk assessment. In this manuscript, 17 toxic congeners of dioxins were analyzed by a system with low resolution mass spectrometry. The sensitivity, stability and resolution power of the system for the analysis of dioxins were investigated. The calibration experiments in 3 different periods were studied and the minimum detection limits were determined by using the labeled and unlabeled standard solutions. The differences according to operation conditions of the ion source were examined and expounded by using relative response factor and relative standard deviation values obtained from sequential injections. Finally, it was performed a sample analysis program for some local food samples with the aim of observing the feasibility of the system on food samples that have very low level dioxin concentrations such as egg and cow's milk. It was found that the systems with low resolution mass spectrometry in negative chemical ionization mode are capable to fulfill the requirements for the environmental analyses of dioxins at ppt levels, with the exception of 2,3,7,8-TCDD showing lower sensitivity in negative chemical ionization. Thus, using the systems with low resolution mass spectrometry in negative chemical ionization mode may be recommended for the some environmental studies for dioxins in the absence of the systems with high resolution. On the other hand, the proposed methodology cannot be used for the direct analysis of dioxins without improvement of 2,3,7,8-TCDD detection and quantification.