Gas Chromatography-mass Spectrometric Determination Research Articles

Effect of ionizing radiation on the physico-chemical and performance properties of gasoline with the additive of benzene

The effect of irradiation was studied by adding benzene to AI-92 gasoline. Kinetics of processes were studied at temperature T = 20°С, dose rate P = 0.072 Gy/s, absorbed doses ( D ) in the range of 27-78 kGy. The results of gas chromatography-mass spectrometric (GC/MS) analysis, IR-spectroscopic studies, and determination of density and viscosity of samples before and after irradiation at di erent absorbed doses are presented. The evaluation of the physicochemical parameters of γ-irradiated gasoline with 1, 2, 4, and 6% benzene additives shows that γ-irradiation has a negative e ect on the performance characteristics (viscosity and density) of AI-92 gasoline. The optimal concentration of benzene is 6% when the viscosity and density decrease with the increase of the absorbed dose. The kinetics of post-polymerization processes for 8 months after the end of irradiation shows that the speed of the process and its share in the total polymerization depend on the irradiation time, the initial density of the mixture, and the dose.

Gas chromatography-mass spectrometric determination of bisphenol residues by dispersive solid phase extraction followed by activated carbon spheres cleanup from fish feed samples.

Bisphenols are known endocrine disruptors commonly utilized in food packaging and storage materials, which frequently come into touch with multiple food products packed in them. The bisphenols in fish feed and other feed materials for aquatic organisms are harmful. The consumption of such marine foods is hazardous. Hence, the feed of aquatic products needs to be verified for the presence of bisphenols. The present study was focused on developing and validating a rapid, selective, and sensitive method to quantify 11 bisphenols from the fish feed with dispersive solid-phase extraction, which was cleaned by an optimized amount of activated carbon spheres and silylated by N,O-bis(trimethylsilyl)trifluoro acetamide and analyzed by gas chromatography-mass spectrometry. The new method was rigorously tested and verified after carefully tuning various parameters affecting analyte recovery. Limit of detection (LOD) were set at 0.5-5 ng/g and limit of quantification (LOQ) at 1-10 ng/g, respectively, resulting in 95-114% recoveries. Interday and intraday precisions in terms of relative standard deviation were found to be less than 11%. The proposed approach was effectively applied in floating and sinking fish feeds. The obtained results showed that higher concentration of bisphenol A, followed by bisphenol TMC, and bisphenol M at a concentration of 256.10, 159.01, and 168.82 ng/g in floating feed and 88.04, 200.79, and 98.03 ng/g in sinking feed samples, respectively.

Gas chromatography-mass spectrometric determination of organic acids by ion pair liquid extraction followed by in-situ butylation from aqua feed samples.

A rapid and sensitive analytical method was developed to quantitatively determine organic acids (OAs) from fish feed samples extracted by ion-pair (IP) solvent extraction, followed by in-situ butylation and gas chromatography-mass spectrometric (GC-MS) analysis. The extraction of OAs was carried out with acetonitrile containing 10 mM tetrabutylammonium hydroxide (TBAH), and the analytes were derivatized to their butyl esters in the injection port of the GC-MS system. The developed method was validated in the range of 1-5000 ng/g, with recoveries ranging from 93-117%. The limit of detection (LOD) and limit of quantification (LOQ) of the method was 1-5 ng/g and 2-10 ng/g, respectively, yielding good linearity (R2 > 0.9990) and precision with a relative standard deviation less than 10%. The proposed method was successfully applied to analyze OAs in sinking and floating fish feed samples. The analyzed samples showed the presence of benzoic, succinic, fumaric, glutaric, adipic, and phthalic acids in sinking feed samples; and benzoic, succinic, adipic, phthalic acids in floating feed samples, respectively.

Influence of the composition of atmospheric air pollution on genotoxic effects in the buccal epithelial cells in children

Introduction. This publication presents the third fragment of a comprehensive multi-parameter pilot study to create a methodology for assessing the open-air odor’ impact on human’s adaptive potential. The pilot study was carried out in the little town (50 thousands of inhabitants), mainly the food industry and agro-industrial complex work, but enterprises of 1-2 classes of danger are absent. Air emissions from operating enterprises have a specific odor that causes complaints of inhabitants. Materials and methods. The effects of genome instability (EGI) in children attending kindergartens located at a distance of 1.7-5.9 km from enterprises - the primary sources of odor - were assessed. EGI was determined non-invasively using a micronucleus test on exfoliating cheek epithelial cells. The epitheliocytes from 112 children of 5 -7 years old were examined simultaneously with a collection of atmospheric air samples from the walking areas of the kindergartens which the examined children attended. These atmospheric air samples were taken for gas chromatography-mass spectrometric determination of their chemical composition. Results. Seventy-eight chemical compounds belonging to different classes of chemicals were identified in the air samples. The groups of children from different kindergartens did not differ statistically in any of the 13 assessed indicators of the cytome analysis of the buccal mucosa epithelium cells, and the levels of genotoxic and toxic effects did not go beyond the average expected values presented in literature and our studies for differents groups of comparison. High-level and statistically significant direct correlations between the total content of air pollutants with proven genotoxic activity and the two main indicators of the micronucleus test on cheek epithelial cells: the frequencies of cells with micronuclei and cells with accepted apoptotic bodies were revealed. No correlation was found between summarized levels of the detected chemicals limited concentrations and the results of cytome analysis of children’s buccal epithelial cells. Limitations. correct formation of groups for examination, the severity of the criteria for cytotome analysis and identity of cytogenetic effects identification in the course of cytotome analysis by different researchers. Conclusion. The effects of genome instability in the buccal epithelial cells in children were shown to be mainly associated with the presence of substances with proven mutagenic, carcinogenic and neogenic activities, but not with the total excess of hygienic standards for the content of chemical compounds in the air.

Method development, validation, monitoring, seasonal effect and risk assessment of multiclass multi pesticide residues in surface and ground water of new alluvial zone in eastern India.

A liquid-liquid extraction (LLE) method was validated as per SANTE/12682/2019 guidelines for gas chromatography-mass spectrometric (GC-MS) determination of thirty-six multiclass pesticides in environmental waters. Seasonal (summer, monsoon, and winter) effects on the magnitude of pesticide residues in environmental water (river, pond, and tube well) of six different urban areas of Nadia and North 24 Parganas districts (New alluvial zone, Eastern India) was monitored for subsequent risk assessment. Total 288 water samples (96 each of river, pond, and tube-well) irrespective of locations and seasons were monitored for multiclass multi pesticide residues during the experiment. Each sample (750mL) was extracted with ethyl acetate/dichloromethane (8:2) liquid-liquid partitioning and filtration (0.22μm nylon filter paper) and total residue was reconstituted in acetone (1mL) for GC-MS analysis with developed and validated method resulting satisfactory recovery percentages (77.84-118.15%). The maximum no. of organochlorine (OC) and organophosphorus (OP) pesticide residues were dominated in river and pond water irrespective of seasons and monitoring sites. About 74% of river water samples were found to be contaminated with concerned pesticides in variable magnitudes. Monsoon (July to October) season was highly alarming with the highest presence of total pesticide residues in different types of environmental waters. Risk quotient (RQ) [acute and chronic] was also evaluated in pond and river water as sometimes used for drinking purposes. RQ value (5900) of total endosulfan indicates the highest risk of chronic toxicity to river fishes. Seven water samples from tube-wells were also monitored and found to be contaminated with butachlor and chlorpyriphos in non-significant amounts (< 0.1ngmL-1), irrespective of seasons and sites, thus safe for consumption.

Gas chromatography-mass spectrometric determination of organic acids in fruit juices by multiwalled carbon nanotube-based ion-pair dispersive solid-phase extraction and in situ butylation.

Fruit juices are naturally acidic, and the acidity is due to the formation of various organic acids formed in several metabolic processes. The content of acids varies due to various processing parameters during the preparation of fruit juices and their packaging for commercialization. Quantitative determination of organic acids provides the necessary information leading to changes occurred during processing. The organic acids were extracted by ion-pair dispersive solid-phase extraction by multiwalled carbon nanotubes and analyzed using gas chromatography-mass spectrometry (GC-MS) and in situ butylation. The developed analytical method was validated, and the obtained results showed a linearity in the range of 0.5-5000 μg/L levels of the analytes with limit of detection and quantification values of 2-10 and 5-20 μg/L, respectively. The inter- and intra-day reproducibilities are less than 15% with 80%-98% recoveries and less than 20% matrix effect. The developed method was used for the quantitative determination of organic acids present in fresh and packaged apple, grape, orange, and pomegranate juice samples. The content of organic acids was observed in the range of 0.26-3793 μg/L. Pimelic acid was not detected in any of the analyzed fruit juices. Fumaric acid (FA) was observed to be a major organic diacid present in the natural fruit juices. The results indicated that the processing of fruit juices for packaging decreases the content of organic acids in fruits. The developed GC-MS-based analytical method for the analysis of organic acids has good sensitivity and reproducibility for the quantitative determination of various organic acids in fruit juices. FA was observed to be the major carboxylic acid present in fruits. The processed juice samples possess the lowest concentration of organic acids, suggesting that processing has a significant effect on the concentration of organic acids in fruits.

Hollow-fibre liquid-phase microextraction and gas chromatography-mass spectrometric determination of amphetamines in whole blood

Here, we present a fully validated method using a hollow-fibre liquid-phase microextraction technique for the determination by gas chromatography-mass spectrometry (GC–MS) of amphetamine (AMP), methamphetamine (MET), fenproporex (FEN), 3,4-methylenedioxymethamphetamine (MDMA), 3,4-methylenedioxyamphetamine (MDA) and 3,4-methylenedioxyethylamphetamine (MDEA) in whole blood. The validation parameters presented successful values within those recommended by the Scientific Working Group for Forensic Toxicology (SWGTox) in the Standard Practices for Method Validation in Forensic Toxicology. The limits of detection ranged from 1 to 3 ng/mL, and the limits of quantification ranged from 2 to 5 ng/mL. The determination coefficients (r2) ranged from 0.990 to 0.997, and the method presented good intraday and interday accuracy (from 90.4% to 97.2%) and satisfactory recovery (from 68% to 110%). No carryover was observed. The heteroscedasticity was tested, and only AMP presented homoscedasticity. Weighting factors were applied to correct the linearity of MET (1/x2), MDA (1/x), FEN (1/x1/2), MDMA (1/x2) and MDEA (1/y). Dilution integrity was tested at ratios of 1:2, 1:5 and 1:10, and all maintained intraday precision (from 94.9% to 99.3%) and interday precision (from 89.4% to 94.9%). The validated method was applied to six real whole blood samples from individuals suspected of consuming ecstasy, and MDMA, MDA and amphetamine were successfully identified and quantified.

Development of Ultra-sensitive Method for Determination of Trace Atrazine Herbicide in Environmental Water Using Magnetic Graphene Oxide-Based Solid-Phase Extraction Coupled with Dispersive Liquid-Liquid Microextraction Prior to Gas Chromatography-Mass Spectrometry

Atrazine is one of the most widely used herbicides and has caused much concern about its toxic effects on human and ecosystem. In the present work, a new and efficient method for ultra-trace determination of atrazine in water was developed, using magnetic graphene oxide-based solid-phase extraction combined with dispersive liquid-liquid microextraction, followed by gas chromatography-mass spectrometric determination. The effects of sample pH, contact time, type and volume of elution solvent and extraction solvent, desorption time, and salt addition on the extraction efficiency of atrazine were examined and optimized. Under the optimum conditions, an enrichment factor of 1033 and a detection limit of 0.6 ng L−1 for atrazine were achieved. The developed method was applied to the detection of atrazine in river water, lake water, pond water, and groundwater samples, with spiked recovery of 96–102% and RSD of 2.9–10.5%. Therefore, the proposed method allows proper monitoring of trace atrazine in various environmental waters.

Gas chromatography-mass spectrometric determination of components of leaves of Aegle marmelos and Psidium guajava and seeds of Nigella sativa and correlation with In vitro antioxidant activity

Objective: The aim of this study is to analyze the volatile components of the leaves of Aegle marmelos, Psidium guajava, and seeds of Nigella sativa, using gas chromatography-mass spectrometric (GC-MS) and correlate with their in vitro antioxidant activity. Materials and Methods: Plant material was analyzed for heavy metal content (HMC), pesticide residue (PR), and the presence of microbes/fungi. Following hydrodistillation, the volatile components (AM, PG, and NS) were subjected to GC-MS analysis and in vitro antioxidant assay (2,2-diphenyl-1-picrylhydrazyl). Results: The plant material passed the test for HMC, PR, microbial, and fungal contamination. Using GC-MS, the number of compounds identified in AM, PG, and NS were 62, 46, and 58, respectively. The antioxidant activity of AM, PG, and NS was 98.538%, 98.955%, and 97.755%, respectively. Conclusion: GC-MS-based methods can be successfully utilized for phytochemical profiling and standardization of plant material. Abbreviations Used: AM: Volatile oil of Aegle marmelos Correa.; GC-MS: Gas chromatography-mass spectrometry; HMC: Heavy metal content; NS: Volatile oil of Nigella sativa Linn.; PG: Volatile oil of Psidium guajava Linn.; PR: Pesticide residue.

Combined dispersive solid-phase extraction-dispersive liquid–liquid microextraction-derivatization for gas chromatography–mass spectrometric determination of aliphatic amines on atmospheric fine particles

Short-chain aliphatic amines are ubiquitous in the atmospheric environment. They play an important role in the formation and growth of atmospheric particles. As such, there is a pressing need to monitor these particle-bound compounds present at trace quantities. The present work describes an efficient, one-step microextraction technique for the preconcentration and detection of trace levels of 10 aliphatic amines on fine particles (particulate matter of 2.5μm or less (PM2.5)) in the atmosphere. After extraction of amines from particles in acidified water samples, carbon-based sorbents (in dispersive solid-phase extraction mode), and vortex agitation were utilized for simultaneous derivatization-extraction and dispersive liquid–liquid microextraction. The approach significantly increased the recoveries and enrichment of the amine derivatives. This one-step, combined technique is proposed for the first time. Several influential factors including type and concentration of derivatization reagent (for gas chromatographic separation), type of buffer, sample pH, types and volumes of extraction and disperser solvents, type and amount of sorbent, vortex time and temperature, desorption solvent type and volume, and salt content were investigated and optimized. Under the optimum conditions, high enrichment factors (in the range of between 307 and 382) and good reproducibility (relative standard deviations, below 7.0%, n=5) were achieved. The linearity ranged from 0.1μg/L–100μg/L, and from 0.5μg/L–100μg/L, depending on the analytes. The limits of detection were between 0.02μg/L (corresponding to ∼0.01ng/m3 in air) and 0.09μg/L (corresponding to ∼0.04ng/m3 in air). The developed method was successfully applied to the analysis of PM2.5 samples collected by air sampling through polytetrafluoroethylene filters. The concentration levels of amines ranged from 1.04 to 4.16ng/m3 in the air sampled.

A comparative study of two ionization techniques in gas chromatography-mass spectrometric determination of sterenes in olive oil

The gas chromatography⁃mass spectrometric (GC⁃MS) method with two different ionization techniques, electron impact (EI) and positive chemical ionization (PCI), have been developed for the simultaneous determination of three sterenes in olive oil. The olive oil sample was dissolved in petroleum ether, followed by cleanup on a silica gel column and finally ana⁃ lyzed by GC⁃EI / MS and GC⁃PCI / MS in selected ion monitoring mode. The quantitation was per⁃ formed by internal standard calibration with cholesta⁃3,5⁃diene as internal standard. These two methods were compared in terms of linearity, accuracy, precision and sensitivity. Good lineari⁃ ties were obtained with correlation coefficients (r) higher than 0􀆰 999 for campesta⁃3,5⁃diene in the range of 0􀆰 024 to 0􀆰 48 mg / L, stigmasta⁃3,5,22⁃triene in the range of 0􀆰 02 to 0􀆰 50 mg / L and

A simple and sensitive single-step method for gas chromatography–mass spectrometric determination of fipronil and its metabolites in sugarcane juice, jaggery and sugar

A simple and sensitive single-step method for gas chromatography–mass spectrometric determination of fipronil and its metabolites viz., fipronil desulfinyl, fipronil sulphide and fipronil sulphone in sugarcane juice, jaggery and sugar has been developed. Acetonitrile was superior to ethyl acetate in terms of selectivity, though they were on par with each other in terms of recoveries. This method does not require any cleanup as the PSA-based cleanup was on par with no-cleanup treatment. Interestingly, the recoveries of fipronil and its metabolites decreased with increased amounts of C18 from 10 to 50mg/g of matrix. Matrix effects were insignificant and the limit of quantification was 0.005μg/g. The recoveries of fipronil and its metabolites varied between 87.5% and 108.5% with the RSD of 0.2–5.3% for all the three matrices studied. This method has also been validated by monitoring fipronil and its metabolites in the retail outlet samples of sugarcane juice, jaggery and sugar.

Ultra sound assisted one step rapid derivatization and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometric determination of amino acids in complex matrices

A rapid and economical method for the simultaneous determination of 20 amino acids in complex biological and food matrices (hair, urine and soybean seed samples) has been developed using ultrasound assisted dispersive liquid–liquid micro extraction (UA-DLLME). The method involves simultaneous derivatization and extraction followed by gas chromatography–mass spectrometric (GC–MS) analysis of amino acids. The parameters of UA-DLLME were optimized with the aid of design of experiments approach. The procedure involves the rapid injection of mixture of acetonitrile (disperser solvent), trichloroethylene (TCE) (extraction solvent) and ethylchloroformate (derivatization reagent) into the aqueous phase of sample extract containing pyridine. The Plackett–Burman design has indicated that, the factors such as volume of disperser and extraction solvents and pH were found to be significantly affects the extraction efficiency of the method. The optimum conditions of these factors based on central composite design were found to be 250μL of acetonitrile, 80μL of TCE and pH of 10. The limit of detection and limit of quantification were found to be in the range of 0.36–3.68μgL−1 and 1.26–12.01μgL−1 respectively. This is the first application of DLLME for the analysis of amino acids in any matrices. The advantages like (i) in situ derivatization and extraction of amino acids without any prior lyophilization and cleanup of sample, (ii) low consumption of extraction solvent, (iii) fast and simple, (iv) cost-effective and (iv) good repeatability make the method amenable for the routine analysis of amino acids in clinical, toxicological, nutritional and quality control laboratories.

Zeolite imidazolate frameworks 8 as sorbent and its application to sonication-assisted emulsification microextraction combined with vortex-assisted porous membrane-protected micro-solid-phase extraction for fast analysis of acidic drugs in environmental water samples

A novel and fast procedure, sonication-assisted emulsification microextraction combined with vortex-assisted porous membrane protected micro-solid-phase extraction (SAEME-VA-μ-SPE), was developed for the gas chromatography–mass spectrometric determination of acidic drugs from environmental water samples. One advantage of the new procedure is that any solvent immiscible with water can be used as extractant solvent of SAEME and any solid sorbent can be used for μ-SPE in the SAEME-VA-μ-SPE process. In the present work, zeolite imidazolate framework 8 (ZIF-8) was employed as extraction sorbent for μ-SPE and 1-octanol as extractant solvent for SAEME. ZIF-8 has very good thermal, chemical and water stability, which make it a suitable material for the extraction of trace analytes from aqueous samples. Under the optimized extraction conditions, the developed method exhibited low limits of detection (0.01–0.04ng/ml), good linearity (with r2 between 0.9965 and 0.9993) from 0.5 to 50ng/ml and satisfactory repeatability (between 4.1% and 7.6%). In essence SAEME-VA-μ-SPE is a combination of two different and efficient miniaturized techniques. It was demonstrated to be a fast, accurate, and convenient pretreatment procedure for trace analysis of environmental water samples.

Application of ethyl chloroformate derivatization for solid-phase microextraction–gas chromatography–mass spectrometric determination of bisphenol-A in water and milk samples

A simple and rapid analytical method based on in-matrix ethyl chloroformate (ECF) derivatization has been developed for the quantitative determination of bisphenol-A (BPA) in milk and water samples. The samples containing BPA were derivatised with ECF in the presence of pyridine for 20 s at room temperature, and the non-polar derivative thus formed was extracted using polydimethylsiloxane solid-phase microextraction (SPME) fibres with thicknesses of 100 μm followed by analysis using gas chromatography-mass spectrometry. Three alkyl chloroformates (methyl, ethyl and isobutyl chloroformate) were tested for optimum derivatisation yields, and ECF has been found to be optimum for the derivatisation of BPA. Several parameters such as amount of ECF, pyridine and reaction time as well as SPME parameters were studied and optimised in the present work. The limit of detection for BPA in milk and water samples was found to be 0.1 and 0.01 μg L(-1), respectively, with a signal-to-noise ratio of 3:1. The limit of quantitation for BPA in milk and water was found to be 0.38 and 0.052 μg L(-1), respectively, with a signal-to-noise ratio of 10:1. In conclusion, the method developed was found to be rapid, reliable and cost-effective in comparison to silylation and highly suitable for the routine analysis of BPA by various food and environmental laboratories.

Abstract 5554: Margin of exposure of genotoxic and carcinogenic furan

Abstract An in-house validated solid-phase microextraction followed by gas chromatography-mass spectrometric determination was used to study furan concentrations in baby-food samples purchased from the Finnish markets (LOD 1.9 ng g−1, LOQ 4.0 ng g−1 and RSTD &amp;lt;20%). The mean levels of furan varied between 4.7 ng g−1 and 90.3 ng g−1 (n=21). The mean concentrations of similar product formulas based on their ingredients were 9.2 ng g−1, 37.0 ng g−1 and 49.6 ng g−1 for fruit-, vegetables- and meat-containing baby-foods, respectively. The consumption of industrial baby-foods in Finland is 172 g/day which results to the furan intake ranging from 0.8 to 15.5 µg/day and exposure of 0.1 to 2.1 µg kg−1 bw/day, respectively. Two extreme worst case scenarios can be deduced from our data: i) the maximum value in consumption of canned baby-foods (883 g/day) and the maximum concentration of furan detected (90.3 µg kg−1) and ii) 95 percentile consumption of canned baby-foods (384 g/day) and the maximum concentration of furan detected (90.3 µg kg−1). These two extreme worst case scenarios gave intakes of 79.7 µg and 34.7 µg, respectively. Applying the benchmark dose rate as well as safety-factor approaches a NOAEL of 0.08 mg kg−1 bw/day for furan can be deduced. If MOE is calculated by using the deduced NOAEL (600 µg/day for 7.5 kg baby) or BMDL10 (1.28 mg kg−1 bw/day) and the worst case exposure scenarios the MOE values of 7.5NOAEL/120BMDL10 and 17.3NOAEL/276BMDL10 can be derived. In the case of low exposure scenario (consumption 172 g/day; furan level 4.7 µg kg−1) the MOE values are 750NOAEL/2030BMDL10. A very low MOE exists in the extreme worst case infant exposures and particularly for such a clear rodent carcinogen (cholangiocarcinoma, hepatocellular adenoma and carcinoma). The MOEs derived clearly indicate that it is now a priority to understand the mode of action for the development of the liver tumours in the rat after exposure to furan and whether this is relevant to man. A significant reduction, however, to the exposure scenarios is provided by the fact that the use of fruit-based baby-foods with low furan content comprises a substantial proportion (mean consumption 78 g/day, maximum consumption 488 g/day and 95 percentile consumption 197 g/day) of the consumption of total industrial baby-foods. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5554. doi:10.1158/1538-7445.AM2011-5554

Ultrasound-assisted hydrolysis and gas chromatography–mass spectrometric determination of phenolic compounds in cranberry products

An ultrasound-assisted hydrolysis and gas chromatography–mass spectrometric (GC–MS) method has been developed for determination of phenolics in cranberry products. Prior to GC–MS separation and characterisation, the phenolics in samples were hydrolysed by hydrochloric acid with ultrasound-assistance, extracted with ethyl acetate, and derivatised with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA)+1% trimethylchlorosilane (TMCS) reagents. The application of ultrasonication significantly accelerated the acidic hydrolysation of the conjugated phenolics. A baseline separation of the 20 phenolics and internal standard was achieved in 25min. Standard calibration curves were linear over the concentration range of 0.0–50μg/mL and detection limits were 0.06–0.70μg/mL. Twenty phenolics were identified in cranberry samples and all of them occurred mainly in conjugated forms. Of those, the benzoic acid, quercetin, and myricetin were most abundant phenolics. The total phenolics were 12.4mg/g in cranberry fruits, 9.1mg/mL in 100% cranberry juice, and 11.1mg/g in cranberry sauces, respectively.

Gas chromatography-mass spectrometric determination of ivermectin following trimethylsilylation with application to residue analysis in biological meat tissue samples

A gas chromatography-mass spectrometric (GC-MS) method utilizing electron impact ionization has been developed for the quantitation of the antiparasitic agent, ivermectin (IVM). The approach is based upon the pre-column derivatization of IVM by reaction with N,O-bis(trimethylsilyl)tri-fluoroacetamide (BSTFA) in the presence of 1-methylimidazole as catalyst and carbon tetrachloride as solvent to form the trimethylsilyl (TMS) derivative of IVM (IVM-TMS) prior to injection into the GC-MS system. The derivatization reaction is complete within 5.0 min at room temperature and allows the GC-MS determination of IVM. A limit of detection for IVM of 0.67 ng g−1 was achieved (via monitoring the peak with m/z = 185 in the selective ion mode and benzophenone-d10 as the internal standard). The method was utilized with success for the determination of IVM in spiked horse meat samples yielding recoveries very similar to that obtained using a reference liquid chromatography-mass spectrometric method (LC-MS). In addition, this GC-MS method can be employed to determine not only IVM but also other related macrolide veterinary drugs such as eprinomectin and moxidectin which are often administered along with IVM. Detection limits of 3.72 and 5.44 ng g−1 were obtained for eprinomectin and moxidectin, respectively.

Single-walled carbon nanotubes coated fibers for solid-phase microextraction and gas chromatography–mass spectrometric determination of pesticides in Tea samples

Using a single-walled carbon nanotubes (SWCNTs) as stationary phase of solid-phase microextraction (SPME) fibers, a simple, low cost and environmentally friendly method for extraction of 13 pesticides in Tea samples has been developed following gas chromatography–mass spectrometric determination. Potential factors affecting the extraction efficiency were investigated and optimized, including extraction and desorption time, extraction temperature, stirring rate, solution pH and ionic strength. Under optimized conditions, the linearity of the developed method was in the range of 0.125–25 ng/mL with correlation coefficients greater than 0.9928 and the limits of detections (LODs) were 0.027–0.23 ng/mL ( S/ N = 3). Meanwhile, the relative standard deviations (RSDs) for five successive measurements with single fiber, fiber-to-fiber, day-to-day were 2.3–13.0, 8.2–14.6 and 4.1–12.5%, respectively, indicating good reproducibility of the proposed method. The fiber had high extraction efficiency for studied pesticides in comparison with commercial poly(dimethylsiloxane) (PDMS) and polyacrylate (PA) fibers and could be used for more than 70 times without decrease of efficiency. The developed method was successfully applied for the analysis of real samples including green Tea, oolong Tea, white Tea, and flower Tea, and the recoveries of the pesticides spiked in these samples ranged from 75.1 to 118.4%. Chlorfenapyr and λ-cyhalothrin were found in the Tea samples bought randomly from local market. The results demonstrated that the developed SWCNTs-SPME method was a simple, efficient pretreatment and enrichment procedure for pesticides in complex matrices.

Tandem capillary column gas chromatography–mass spectrometric determination of the organophosphonate nerve agent surrogate dimethyl methylphosphonate in gaseous phase

A procedure based on capillary column gas chromatographic-mass spectrometric (GC-MS) confirmation was developed for the verification of the ubiquitous and versatile chemical and nerve agent simulant, dimethyl methyl phosphonate (DMMP; CAS# 756-79-6), from gaseous samples. This method was developed to verify low nanogram DMMP concentrations during testing of a nerve agent detection system. Standard solutions of 1, 5, 10, 50, 100, 500, and 1000ng/ml DMMP in acetonitrile were employed. Through 15 calibration curves using the 5 lowest concentrations, coefficient of determination (r(2)) values showed a mean of 0.998 (0.992-1.000). An additional 15 calibration curves likewise containing 5 concentrations of DMMP spanning 3 orders of magnitude (1, 50, 100, 500, and 1000ng/ml) yielded a mean r(2) of 0.997 (0.991-1.000). Sixty-five nitrogen diluted gaseous samples varying from 1.0 to 10.0microl in volume were analyzed and concentrations of DMMP ranging from 1 to 1000ng/ml were confirmed. An additional 35 vapor samples in UHP N(2) ranging in DMMP concentration from 5.8microg/m(3) to 1.0mg/m(3) were analyzed by increasing sample volume range to between 10.0 and 100microl. For gaseous samples with volumes>1.0microl, the lowest concentration observed was 5.8microg/m(3). The method detection limit (Appendix B of Title 40 CFR, United States) for 1.0microl autoinjected standards in acetonitrile was determined to be 0.331ng/ml. Method precision for 15 independently analyzed standards of 25ng/ml had a relative standard deviation of 1.168. This method demonstrated high linearity across a wide range of concentrations, as well as excellent sensitivity and repeatability, and proved applicable to other lower alkyl-phosphonates.