Gas Chromatography And Electron Capture Detection Research Articles

Exploring the use of cork pellets in bar adsorptive microextraction for the determination of organochloride pesticides in water samples with gas chromatography/electron capture detection quantification

In this study, a biosorbent material with characteristics for the adsorption of organic compounds was used for a cork pellet-based bar adsorptive microextraction technique, as a new greener alternative for the determination of organochlorine compounds. Aldrin, chlordane, dieldrin, endrin, lindane, 4,4-DDD, 4,4-DDE, 4,4-DDT, α-endosulfan and β-endosulfan were analyzed in water samples (drinking water, stream water and river water) with separation/detection by gas chromatography and electron capture detection (GC/ECD). The parameters that can affect the sample preparation efficiency such as desorption solvent and time as well as extraction time and ionic strength were evaluated by multivariate and univariate designs. Cork pellets (10 × Ø 3 mm) were used for the extraction of 15 mL of sample in the optimal conditions: 60 min of agitation with no salt added to the sample, followed by desorption of the cork pellet with 120 µL of ethyl acetate for 30 min. The bar-to-bar RSD out with five different bars showed good results with RSD ≤ 15.6%, allowing the use of simultaneous extractions. LOD and LOQ values ranged from 3 to 15 ng L−1 and 10 to 50 ng L−1 respectively, and the determination coefficients were greater than 0.9869. The target analytes were not detected in the three analyzed samples. Therefore, the recovery study was performed fortifying the water samples. Analyte recovery ranged from 48.7 – 138.2% for drinking water, 40.2 – 128.2% for stream water and 67.5 – 128.7% for river water.

Competitive immunoassay for monitoring polybrominated diphenyl ethers in PM2.5 in Shanghai

ABSTRACTIn this paper, a sensitive biotin–streptavidin (BS)-ELISA was developed for determining the polybrominated diphenyl ethers in PM2.5. For establishing this proposed BS-ELISA, we prepared the biotinylated antibody primarily. And for reducing the background interference, some influencing factors and procedures for this immunoassay were also discussed and optimised. Under the optimal conditions, the IC50 = 0.53 ng/mL; IC10 was 0.002 ng/mL; and the results were almost consistent with those using the gas chromatography and electron capture detection (GC-ECD). Less procedures and simpler sample preparation were required for this method compared with the GC-ECD. The results showed that the highest value of BDE-47 concentration occurred in December, which might reflect the combination of heating and industrial pollution. In our analysis, we studied the Pearson correlations between BDE-47/PM2.5 and gaseous pollutants (such as NO2, SO2, CO, O3, PM10 and PM2.5). BDE-47 showed a higher correlation with NO2 than that with PM10, PM2.5 and SO2, which implied that the BDE-47 emission process might be accompanied by the emission of NO2. Moreover, during the Spring Festival, the concentration of BDE-47 in PM2.5 decreased significantly, whereas the PM2.5 changed little. This suggested factories and vehicles might be the major contributors to BDE-47 emissions (but not to PM2.5).

Troubleshooting in the Analysis of Hexachlorocyclohexane Isomers in Agar-Agar Culture Media

A method to determine hexachlorocyclohexane isomers (HCHs) in agar-agar culture media was developed in order to study the bioremediation potential of these compounds. Spiked culture medium samples (0.5 g) were finely chopped and then extracted with 20 ml of hexane:ethyl acetate (80:20) in an ultrasonic bath during 30 min and analyzed by gas chromatography and electron capture detection (GC-ECD). Analytical recoveries were highly satisfactory, ranging between 84 and 101%, and relative standard deviations were lower than 5%. The method was applied to evaluate the stability of lindane (γ -hexachlorocyclohexane, γ-HCH) and isomers (α-, β- and δ -HCH) in agar-agar culture media at different temperatures. Our results showed a decrease on the recoveries of γ- and α-HCH, very important in the case of α-HCH, during the incubation period at room temperature and at 30°C, while the losses of β -HCH and δ-HCH were negligible.

Application of fractional factorial experimental and Box-Behnken designs for optimization of single-drop microextraction of 2,4,6-trichloroanisole and 2,4,6-tribromoanisole from wine samples

In this paper a new method for the determination of 2,4,6-trichloroanisole (TCA) and 2,4,6-tribromoanisole (TBA) in wine samples is presented. Headspace single-drop microextraction (HS-SDME) was used for the extraction and preconcentration of the analytes, followed by analysis by gas chromatography and electron-capture detection (GC-ECD). The variables affecting extraction efficiency were optimized using fractional factorial experimental and Box-Behnken designs. The external calibration procedure was successfully carried out using a synthetic wine solution and diluted red wine samples. The method was also applied to white wine samples. Excellent detection limits of 8.1 and 6.1 ng L −1 were achieved for TCA and TBA, respectively. Good precision and accuracy were obtained.

Urinary Pentachlorophenol in Painters and Bricklayers in a Four-Years Time Interval after the PCP Prohibition Ordinance in Germany

Pentachlorophenol (PCP) was widely used as a wood preservative in Germany until 1989, when it was prohibited by law. Within a cross-sectional study we investigated the internal PCP exposure of painters and bricklayers between one year and four years after the ban. PCP was analysed in post-shift urine samples of 189 painters and 148 bricklayers by gas chromatography and electron capture detection (GC-ECD). The median PCP concentration in the urine of painters was 2.4 microg/g creatinine (range: 0.2-52 microg/g creatinine). For the bricklayers a range of 0.1-25 microg/g creatinine (median: 1.8 microg/g creatinine) was determined. The difference between both groups was statistically significant, pointing to a small additional uptake of PCP by the painters probably from an exposure to contaminated wood surfaces or residual PCP containing preservatives. The biomonitoring results for both groups coincided with background values of the general population at that time.

Determination of organochlorine pesticides in horticultural samples by microwave assisted extraction followed by GC-ECD

A method to determine 21 organochlorine pesticides in horticultural samples (lettuce, pepper, tomato, spinach and potato) based on microwave assisted extraction (MAE) followed by solid-phase extraction (SPE) clean-up is described. After extraction with hexane : acetone (50 : 50), a carbon cartridge was employed for the clean-up step. Pesticides were eluted with 5 mL of hexane : ethyl acetate (80 : 20) and determined by gas chromatography and electron capture detection (GC-ECD). Results were confirmed by GC-MS analysis. Analytical recoveries obtained were ca. 100% for most of the studied pesticides with the proposed method in each analysed matrix. The method was applied to analyse 35 commercial samples from A Coruña (NW Spain); only two samples contained pesticide residues, but none of them exceeded the MRLs established by EU legislation.

Solid-phase microextraction of the herbicide metolachlor in runoff and tile-drainage water samples

The new rapid solid-phase microextraction (SPME) technique developed in Canada by Pawliszyn and co-workers has been used in the analysis of water for pesticide residues in laboratory studies. SPME used with gas chromatography and electron-capture detection (GC-ECD) of metolachlor in runoff water showed linear response over a wide range. The lowest concentration analyzed was 0.002 μg/1 (2 ppt), and the highest was 20 000 μg/1 (20 ppm). Over this span of seven orders of magnitude, the standard curve had an R 2 of 0.9954 for ten data points, each of which was averaged over three or more trials. The curve below 200 μg/1, or 0.20 ppm had a slightly different slope ( R 2 0.9996). Earlier analyses by automated SPME-GC and flame ionization detection (FID) in distilled water showed linear response over the range 180 to 180 000 μg/1. A 100-μm polydimethylsiloxane-coated fibre was used; metolachlor residues in the runoff water were 0.17 to 50.7 μg/1. This is the first time, to our knowledge, that SPME has been used in the analysis of herbicide residues in runoff water.

Extra-hepatic metabolism of midazolam.

Six patients received 10 mg of midazolam intravenously during the anhepatic period of liver transplantation. Arterial blood was sampled during this time and for a similar period following revascularisation. The plasma was analysed using gas chromatography and electron capture detection (GC-ECD) for midazolam alpha-hydroxymidazolam and alpha-hydroxymidazolam glucuronide. Five of the six patients had small but significant concentrations of metabolites detected during the anhepatic period, demonstrating the presence of extra-hepatic sites of metabolism for this drug. The remaining patient had plasma concentrations of metabolites below the lower limit of detection (2 micrograms l-1). This may represent a pharmacogenetic abnormality or a temporary failure of midazolam metabolism secondary to the patients illness affecting the extra-hepatic sites of metabolism.