Gas Chromatography-electron Impact Ionization Research Articles

Soil concentrations of polybrominated diphenyl ethers and trace metals from an electronic waste dump site in the Greater Accra Region, Ghana: Implications for human exposure

Unregulated electronic waste (e-waste) recycling operations have become a significant environmental issue as well as human health risk in developing countries across the world. The present study evaluated the extent of pollution in Agbogbloshie e-waste recycling site in Accra, Ghana. The concentrations of polybrominated diphenyl ethers (PBDEs) and some selected trace metals were determined using gas chromatography electron impact ionization mass spectrometry and flame atomic absorption spectrophotometry, respectively. The concentrations of ∑ PBDEs ranged from 15.6 to 96.8ngg−1 dry weight, with an overall mean of 54.8ngg−1dw. BDE-28 was the dominant congener followed by BDE-209 and BDE-47. The order of mean concentrations of the abundant trace metals was Fe>Cu>Pb≫Mn, with a mean range of .531–289mgkg−1. Geoaccumulation index suggested that the surface soils deteriorated from moderate to high metal pollution, particularly for Cu, Pb and Fe. Of the trace metals analysed, Fe exhibited the highest concentration ranging from 3.97 to 918mgkg−1. Correlation and principal component analyses suggested possible interactions between PBDEs and the trace metals analysed, while source assessment suggested that PBDEs and trace metals were mostly derived from inputs from the e-waste recycling activities. Average daily dose (ADD) was estimated using concentrations corresponding to 5th percentile, median and 95th percentile. Hazard quotients of 380 and 862 were obtained for adults and children respectively, for Cu and Pb which is a cause for concern especially for local children.

Polybrominated diphenyl ethers in car dust in Nigeria: Concentrations and implications for non-dietary human exposure

In the present study, the levels of polybrominated diphenyl ethers in car dust samples collected from 12 randomly selected cars in Nigeria were measured, and the daily intake via dust ingestion were estimated for four categories of individuals. PBDEs were extracted and analyzed using ultra-sonication extraction and gas chromatography electron impact ionization mass spectrometry (GC-EIMS), respectively. The concentrations of ∑7PBDEs ranged from 159 to 736ngg−1 dry weight. BDE-209 was found to be the most prevalent congener with a total of 2130ngg−1, contributing up to 47% of the total congener values (4554ngg−1) and the other congeners contributed 53%. The mean and median concentrations of detected congeners ranged from 65 to 137 and 14 to 127ngg−1 dry weight, respectively. BDE-47 was detected in all the dust samples at a detection frequency of 100%, and this was followed by BDE-209 with 92%. The daily intake (DI) was estimated using concentrations corresponding to 5th percentile, median, and 95th percentile. The estimated DI was highest for professional drivers at 0.12ngkg−1 bw day−1 and this was followed by toddlers (0–3years) at 0.09ngkg−1 bw day−1 while DI estimate of 0.01ngkg−1 bw day−1 was determined for children (4–18years) and adults (>19years). PBDEs daily intake rates from car dust estimated in the present study are way below the USEPA reference dose (RfD) for oral exposure to PBDEs 47, 99, 153, and 209 of 100, 100, 200, and 7000ngkg bw day−1

Identification of N-ethyl-α-ethylphenethylamine in crystalline powder seized for suspected drug trafficking: a research chemical or a new designer drug?

A crystalline powder was found in an unclaimed lost article shipped from Vietnam to South Korea, and it was seized by narcotics agents as an item of suspicious trade. The chemical was suspected to be methamphetamine crystals, and was sent to the National Forensic Service for forensic identification. Elucidation of the chemical structure was carried out using gas chromatography–electron impact ionization–mass spectrometry, liquid chromatography–time-of-flight–mass spectrometry, and 1D and 2D nuclear magnetic resonance spectroscopy. The compound was identified as N-ethyl-α-ethylphenethylamine. Although the narcotic effect of this compound remains unverified, it may be classified as a phenethylamine-based designer drug on the basis of its structure. It appeared that the recipient of this article sought to abuse this chemical in the same way as amphetamines. There is a possibility that this chemical will be widely abused for recreational use in the near future.

Multi-residue method for the determination of brominated and organophosphate flame retardants in indoor dust

A new method was optimized for the simultaneous determination of several flame retardants (FRs) in indoor dust, namely polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDs), novel brominated flame retardants (NBFRs) and organophosphate ester flame retardants (OPFRs). The method was based on two previously validated analytical methods for NBFRs and OPFRs, which were combined in order to include even a large number of FRs. An ultrasonic extraction method and two-stage clean-up by adsorption chromatography was optimized using an indoor dust standard reference material (SRM 2584). The 1st cleanup step was essential for fractionation of analytes in the dust extracts, while the 2nd step was important for the further removal of interferences. Analysis of cleaned dust extracts was performed with gas chromatography electron impact ionization mass spectrometry for OPFRs, gas chromatography electron capture negative ionization mass spectrometry for PBDEs and NBFRs and liquid chromatography electrospray ionization tandem mass spectrometry for HBCDs. Method validation by matrix spiking demonstrated good accuracy ranging from 81 to 130%. Matrix effects were investigated by spiking sodium sulfate and dust with analyte standards. Typical recoveries ranged between 80 and 110% at both spiking levels, though occasional deviations were observed at low spiking concentrations. Precision between different days was generally below 24% relative standard deviation (RSD) at low concentrations and below 11% RSD at high concentrations. Method limits of quantification for BFRs ranged between 0.04 (BDE 28) and 17ng/g (BDE 209), 6ng/g for sum HBCDs, and for OPFRs between 10 (triphenyl phosphate) and 370ng/g (tri-isobutyl phosphate). The method was applied to SRM 2585 and to a set of indoor dust samples from various countries. The newly developed method will be employed for the monitoring of human exposure via dust ingestion to phased-out and alternate FRs.

ANALYSIS AND IDENTIFICATION SPIKING CHEMICAL COMPOUNDS RELATED TO CHEMICAL WEAPON CONVENTION IN UNKNOWN WATER SAMPLES USING GAS CHROMATOGRAPHY AND GAS CHROMATOGRAPHY ELECTRON IONIZATION MASS SPECTROMETRY

The identification and analysis of chemical warfare agents and their degradation products is one of important component for the implementation of the convention. Nowadays, the analytical method for determination chemical warfare agent and their degradation products has been developing and improving. In order to get the sufficient analytical data as recommended by OPCW especially in Proficiency Testing, the spiking chemical compounds related to Chemical Weapon Convention in unknown water sample were determined using two different techniques such as gas chromatography and gas chromatography electron-impact ionization mass spectrometry. Neutral organic extraction, pH 11 organic extraction, cation exchanged-methylation, triethylamine/methanol-silylation were performed to extract the chemical warfare agents from the sample, before analyzing with gas chromatography. The identification of chemical warfare agents was carried out by comparing the mass spectrum of chemicals with mass spectrum reference from the OPCW Central Analytical Database (OCAD) library while the retention indices calculation obtained from gas chromatography analysis was used to get the confirmation and supported data of the chemical warfare agents. Diisopropyl methylphosphonate, 2,2-diphenyl-2-hydroacetic acid and 3-quinuclidinol were found in unknown water sample. Those chemicals were classified in schedule 2 as precursor or reactant of chemical weapons compound in schedule list of Chemical Weapon Convention. Keywords: gas chromatography, mass spectrometry, retention indices, OCAD library, chemical warfare agents

A validated gas chromatographic–electron impact ionization mass spectrometric method for methamphetamine, methylenedioxymethamphetamine (MDMA), and metabolites in mouse plasma and brain

A method was developed and fully validated for simultaneous quantification of methamphetamine (MAMP), amphetamine, hydroxy-methamphetamine, methylenedioxymethamphetamine (MDMA, ecstasy), methylenedioxyamphetamine, 3-hydroxy-4-methoxy-methamphetamine, and 3-hydroxy-4-methoxy-amphetamine in 100 μL mouse plasma and 7.5 mg brain. Solid phase extraction and gas chromatography–electron impact ionization mass spectrometry in selected-ion monitoring mode achieved plasma linear ranges of 10–20 to 20,000 ng/mL and 0.1–0.2 to 200 ng/mg in brain. Recoveries were greater than 91%, bias 92.3–110.4%, and imprecision less than 5.3% coefficient of variation. This method was used for measuring MAMP and MDMA and metabolites in plasma and brain during mouse neurotoxicity studies.

Biodegradation and Product Identification of [14C]Hexabromocyclododecane in Wastewater Sludge and Freshwater Aquatic Sediment

In a previous study the biodegradation of hexabromocyclododecane (HBCD) was reported to occur under realistic environmental concentrations in soils and freshwater aquatic sediments with biotransformation half-lives ranging from approximately 2 days to 2 months. In this study we extend our knowledge as to the environmental behavior of HBCD with respect to the fate of the three major diastereomers of HBCD (alpha, beta, and gamma) as well as to the identification of major intermediate metabolites formed during degradation. Substantial biological transformation of the alpha-, beta-, and gamma-[14C]HBCD diastereomers was observed in wastewater (i.e., digester) sludge and in freshwater aquatic sediment microcosms prepared under aerobic and anaerobic conditions. Concomitant with the loss of [14C]HBCD in these matrixes there was a concurrent production of three [14C]products. Using a combination of high performance liquid chromatography atmospheric pressure photoionization mass spectrometry and gas chromatography electron impact ionization mass spectrometry these metabolites were identified as tetrabromocyclododecene, dibromocyclododecadiene, and cyclododecatriene. We propose that HBCD is sequentially debrominated via dihaloelimination where at each step there is the loss of two bromines from vicinal carbons with the subsequent formation of a double bond between the adjacent carbon atoms. These results demonstrate that microorganisms naturally occurring in aquatic sediments and anaerobic digester sludge mediate complete debromination of HBCD.

Determination of 14 benzodiazepines and hydroxy metabolites, zaleplon and zolpidem as tert-butyldimethylsilyl derivatives compared with other common silylating reagents in whole blood by gas chromatography–mass spectrometry

The most common commercially available silylating reagents, N-methyl- N-(trimethylsilyl)trifluoroacetamide (MSTFA), N, O-bis-(trimethylsilyl)trifluoroacetamide + 1% trimethylchlorosilane (BSTFA + 1% TMCS) and N-methyl- N-( tert-butyldimethylsilyl)trifluoroacetamide (MTBSTFA) were evaluated to achieve optimal derivatization conditions for analyzing various benzodiazepines based on gas chromatography–electron impact ionization–mass spectrometry (GC–EI–MS). Sensitivity, repeatability, retention times and stability of the derivatives, as well as specificity of mass fragmentation, were studied in detail. Also other parameters affecting the derivatization chemistry of benzodiazepines are discussed. tert-Butyldimethylsilyl (TBDMS) derivatives proved to be more stable, reproducible and sensitive than corresponding trimethylsilyl (TMS) derivatives for the GC–EI–MS analysis of benzodiazepines. Based on the TBDMS derivatives, a rapid, reliable, sensitive and quantitative GC–MS method was developed for the determination of 14 benzodiazepines and two hydroxy metabolites, as well as two non-benzodiazepine hypnotic agents, zolpidem and zaleplon, using 500 μl of whole blood. The method was completely validated in terms of accuracy, intra- and interday precision, limit of detection (LOD), limit of quantitation (LOQ), linearity, selectivity and extraction efficiency; these were all within the required limits, except for the accuracy of nitrazepam at a medium concentration level.

Quality assurance of commercial beeswax: II. Gas chromatography–electron impact ionization mass spectrometry of alcohols and acids

Gas chromatography with mass spectrometric detection was used to find the fraction of alcohols and acids present in pure beeswax from Apis mellifera. Some new compounds not described till now were found, such as a family of unsaturated linear fatty acids, several hydroxyacids and 1,2,3-propanetriol monoesters. The chromatographic profiles obtained from pure beeswax and bee-rejected foundation beeswax can be used to discriminate them; they mainly differ in the amount of some acids and alcohols.

Quantitation of formate by solid-phase microextraction and gas chromatography–mass spectrometry utilizing a [ 13C]formate internal standard

A new method for the analysis of formic acid was developed using gas chromatography–electron impact ionization mass spectrometry in the selected ion monitoring mode and solid-phase microextraction. Using this method with [ 13C]formic acid as an internal standard, the peak area ratio of [ 12C]formic acid/[ 13C]formic acid was not affected by differing methanol or sulfuric acid concentrations during the esterification and fiber adsorbing step. In comparison, the peak area ratio of formic acid/acetonitrile as detected by conventional GC with flame ionization detection was greatly affected by methanol or sulfuric acid concentrations. The formic acid calibration curve of our method showed excellent linearity over the range 5 to 200 μ M. The within- and between-run assay relative standard deviations for the formic acid concentration were all less than 1.70%.

Assay of the deuterium enrichment of water via acetylene.

A technique is presented for measuring the 2H enrichment of water in biological samples when this enrichment is greater than 0.2%. The sample is reacted with calcium carbide to form acetylene gas, which is determined by gas chromatography electron impact ionization mass spectrometry. Ion-molecule reactions, resulting in proton abstraction, are minimized by lowering the electron ionization energy from the usual 70 eV to 45 eV. This technique is much more rapid and economical than the classical isotope ratio mass spectrometric assay of the enrichment of hydrogen gas derived from reduction of water.

Negative-ion counting techniques for gas chromatography—mass spectrometry

Negative-ion counting techniques for gas chromatography—electron-impact ionization quadrupole mass spectrometry (g.c.—m.s.) are described. Signal-to-noise performance is good and data acquisition is fast. Digital processing of the negative ion signals is done with an ion-counting device and data acquisition with a multi-channel analyzer. The negative-ion mass spectra from g.c.—m.s. measurements are shown for a mixture of tetrachloro-methane, 1,2,2-trichloroethane and 1,1,2,2-tetrachloroethane.