Gas Chromatography-electron Capture Detection Research Articles

Sulfonic acid-based metal organic framework functionalized magnetic nanocomposite combined with gas chromatography-electron capture detector for extraction and determination of organochlorine

The metal organic framework functionalized with sulfonic acid was combined with magnetic nanoparticles to fabricate a new nanocomposite (denoted as Fe3O4@PDA@Zr-SO3H). By combining with gas chromatography-electron capture detector, the resulting Fe3O4@PDA@Zr-SO3H nanocomposite was successfully used as a high-efficiency adsorbent for pre-concentrating eight organochlorine pesticides from water sample in environment. Apart from the ability of fast separation, the as-prepared Fe3O4@PDA@Zr-SO3H nanocomposite also exhibited high adsorption capacity for organochlorine pesticides. With the use of optimal experimental conditions, the linear relationship can be obtained in the range of 0.05∼300 μg/L, the correlation coefficient was over 0.9978, and the relative standard deviation was located in 2.5%–7.7%. Moreover, the limit of detection and quantification was between 0.005–0.016 μg/L and 0.017∼0.050 μg/L. Finally, the nanocomposite was used for the determination of organochlorine pesticides from environmental water samples, and displayed the recovery of 82%–118%.

Transfer of Organochlorine Pesticide Residues during Household and Industrial Processing of Ginseng

Ginseng is an important traditional herbal medicine; however, ginseng root may contain pesticide residues that may cause adverse health effects to consumers. Generally, people are more inclined to take the household- or industrial-processed ginseng products, instead of eating them directly. To investigate the intake of pesticides along with ginseng more specifically, we simulated two household processing methods (boiling and brewing) and two industrial processing methods (ethanol refluxing and boiling combined with resin purification) and then calculated the transfer rates of five organochlorine pesticide (OCP) residues in ginseng. The determination of targeted pesticide residues in ginseng was done by gas chromatography-electron capture detector (GC-ECD), and the confirmation was done by gas chromatography-tandem mass spectrometer (GC-MS/MS). The transfer rates of five OCPs during boiling, brewing, ethanol refluxing, and boiling combined with resin purification were 3.44%–34.43%, 1.47%–38.12%, 34.81%–57.0%, and 0–2.91%, respectively. The transfer rates of the OCPs in water extraction (boiling and brewing) were relatively low and would not increase significantly along with two hours of boiling. The OCPs were concentrated during the ethanol refluxing procedure because of the high transfer rates of the OCPs and the reduction of the weight of products. The boiling combined with resin purification method removed the OCPs most effectively. Different ginseng processing methods resulted in variable transfer rates of pesticides, as well as a diverse exposure risk of pesticides to humans. Consequently, it is necessary to concern about the transfer rates of pesticide residues during ginseng processing.

Occurrence of a Polychlorinated Biphenyl (PCB) Congener in Surface Water, Sediments and Blackchin Tilapia (<i>Sarotherodon melanotheron</i>) from Ologe Lagoon, Nigeria

Polychlorinated biphenyls (PCBs) are persistent organochlorine chemicals that are toxic to aquatic organisms and humans. PCBs levels were assessed in surface water, sediments and fish from Ologe Lagoon, a major water body receiving treated effluents from Agbara Industrial Estate, using Gas Chromatograph-Electron Capture Detector (GCECD). 2,4,4’-Trichlorobiphenyl (2,4,4’-TCB) was the only PCB congener detected in the assessed matrices. Sediment 2,4,4’-TCB levels ranged from 0.0033±0.00333 to 0.0430 ± 0.00351ng/g. There was a significant (p < 0.05) seasonal variation in the levels in sediments and surface water. The level in surface water from Zone 3 was above USEPA’s safe limit (0.0005 mg/L) in the rainy season. There was no significant (p > 0.05) seasonal difference in the mean concentrations of 2,4,4’-TCB in fish, and the levels were lower than WHO’s safe limit (0.2 mg/kg). Based on the negligible to low levels of 2,4,4’-TCB in S. melanotheron inhabiting the lagoon, the fish was considered safe for consumption. Levels of 2,4,4’- TCB found in the sediments and surface water in this study indicate that levels may change with season, therefore, we recommend that the concentrations of the compound are regularly monitored in order to timely avert toxic levels of bioavailable 2,4,4’-TCB in the water body.Keywords: Polychlorinated biphenyls, Sarotherodon melanotheron, Sediments, Surface water.

A silica-based three-dimensional molecularly imprinted coating for the selective solid-phase microextraction of difenoconazole from wheat and fruits samples

In this work, a selective silica-based molecular imprinted solid-phase microextraction (SPME) sorbent was prepared through the sol-gel process. Difenoconazole was used as a template to prepare imprinted materials on the surface of mesoporous silica. The SPME fiber followed by gas chromatography-electron capture detection was applied for the extraction and determination of difenoconazole. Fourier transform infrared spectrometry, field emission scanning electron microscopy, X-ray diffraction, and thermal gravimetry were used to characterize the imprinted SPME fiber.Two different procedures were presented to prepare MCM-41@SiO2-difenoconazole. Also, a non-MCM molecularly imprinted polymer was synthesized to investigate the effect of MCM-41 on the selectivity and extraction efficiency of the sorbent. The important parameters (i.e., desorption time and temperature, ionic strength, stirring rate, pH, extraction temperature and time) affecting the extraction performance of the method were optimized. Under optimum conditions, the limits of detection and quantification were found to be 0.002 and 0.005 ng mL−1, respectively. Linear dynamic range was in the range of 0.01–1 ng mL−1. The intra- and inter-day relative standard deviations and fiber-to-fiber reproducibility were in the range of 4.3–7.5, 3.3–8.2 and 7.4–9.7%, respectively. The fiber was successfully applied for the selective extraction of difenoconazole from wheat and fruit samples and satisfactory results with extraction recoveries >73% were obtained.

Dispersive Liquid-Liquid Microextraction Method for the Simultaneous Determination of Four Isomers of Hexachlorocyclohexane and Six Pyrethroid Pesticides in Milk by Gas Chromatography Electron Capture Detector

In this study, a simple and rapid dispersive liquid-liquid microextraction method was established, and the residuals of four isomers of hexachlorocyclohexane and six kinds of pyrethroid pesticides in milk were simultaneously determined by gas chromatography electron capture detector (GC-ECD). The milk sample was first extracted with acetonitrile and cleaned with primary secondary amine (PSA). Then 0.5 mL of acetonitrile was mixed with 140 μL of cyclohexane and rapidly injected into 3 mL of pure water. After vortexing and centrifugation, the floating phase was removed with a 0.1-mL pipette into the GC-ECD. The type and volume of extraction solvent, volume of disperser solvent, volume of water, vortex time, and amount of salt were optimized. Under optimal extraction conditions, the ten pesticides showed a good linear relationship in a certain concentration range in milk matrix, and the correlation coefficients were greater than 0.99. The limits of detection ranged from 0.07 to 2 μg/kg, and the limits of quantitation ranged from 0.2 to 5 μg/kg. The average recovery rates were between 70.1% and 106.3%, and the relative standard deviations were less than 15.2%. This method can be used for the determination of hexachlorocyclohexane and pyrethroid pesticides in milk and for subsequent research.

New magnetic oil palm fiber activated carbon-reinforced polypyrrole solid phase extraction combined with gas chromatography-electron capture detection for determination of organochlorine pesticides in water samples

Magnetic solid phase extraction (MSPE) employing oil-palm fiber activated carbon (OPAC) modified with magnetite (Fe3O4) and polypyrrole (OPAC-Fe3O4-PPy) was successfully used for the determination of two organochlorine pesticides (OCPs), namely endosulfan and dieldrin in environmental water samples. Analysis was performed using gas chromatography with micro-electron capture detection (GC-μECD). The effects of three preparation variables, namely Fe3O4:OPAC ratio, amount of pyrrole monomer, and amount of FeCl3 oxidant were optimized using Box-Behnken design (BBD) (R2 < 0.99, p-value < 0.001%). The optimum conditions were as follows: Fe3O4:OPAC ratio of 2:1 w/w, 1 g of FeCl3 and 100 μL of pyrrole monomer. The experimental results obtained agreed satisfactorily with the model prediction (> 90% agreement). Optimized OPAC-Fe3O4-PPy composite was characterized using field emission scanning electron microscope, vibrating sample magnetometer and Fourier transform infrared spectroscopy. Four numerical parameters of MSPE procedure was optimized using BBD. The significance of the MSPE parameters were salt addition > sample solution pH > extraction time and desorption time. Under the optimized conditions (extraction time: 90 s, desorption time: 10 min, salt: 0%, and pH: 5.8), the method demonstrated good linearity (25–1000 ng L−1) with coefficients of determination, R2 > 0.991, and low detection limits for both endosulfan (7.3 ng L−1) and dieldrin (8.6 ng L−1). The method showed high analyte recoveries in the range of 98.6–103.5% for environmental water samples. The proposed OPAC-Fe3O4-PPy MSPE method offered good features such as sustainability, simplicity, and rapid extraction.

Spent Mushroom Compost of Pleurotus ostreatus: A Tool to Treat Soil Contaminated with Endosulfan

Composts especially spent mushroom composts (SMC) have been used for their ability to degrade toxic organic pollutants. Due to extreme toxicity, endosulfan (C9H6Cl6O3S) is categorized as a Category 1 pollutant by the U.S. EPA because of its well-reported carcinogenicity. This study was done to monitor the biodegradation potential of SMC against this pesticide. For this purpose, bioreactors (BRs) system was designed to mimic the field conditions. Soil within all four BRs contaminated with endosulfan was amended with four different treatments of SMC. Quantitative reduction in amount of endosulfan isomers was calculated using Gas Chromatography–Electron Capture Detector. For the monitoring of metabolites formed as a result of biodegradation, Gas Chromatography–Mass Spectrometry was used. Maximum attenuation was observed in BR1 (fresh SMC and soil). In BR2 when fresh SMC was added in sterilized soil, rate of removal was declined as compared to BR1. In another bioreactor BR3, where unsterilized soil was used with sterilized SMC, total reduction in quantity of endosulfan was less than BR1 and BR2. BR4 (abiotic control) showed the least reduction suggesting the role of SMC and soil microbes. Degradation was well described using simple first-order kinetics which revealed that the active microcosm of BR1 manifested least DT50. Denaturation of either SMC(BR3) or soil(BR2) or both (BR4) resulted in less biodegradation than BR1.

Combined Approach for Determining Diuron in Sugarcane and Soil: Ultrasound‐Assisted Extraction, Carbon Nanotube‐Mediated Purification, and Gas Chromatography–Electron Capture Detection

Diuron is a urea herbicide that is frequently detected in surface water, groundwater, and marine waters. However, there are few methods or guidelines reported on ensuring the quality of sugarcane and soil. In this study, a method was developed for detecting diuron to ensure the quality and safety of food and sugar. Mass spectrometry was used to identify 3,4-dichloroaniline as a marker for the thermal decomposition of diuron, and thus, as a representative component for quantitative diuron analysis. This approach can be used to rapidly detect trace amounts of diuron. In addition, ultrasound-assisted extraction (UAE) and carbon nanotube column purification were used in conjunction with gas chromatography-electron capture detection to detect diuron. The method was then evaluated for its accuracy, detection limit, and viability. The effects of extraction solvent, ultrasound time, and ultrasound power on the extraction efficiency of the analyte from sugarcane and soil were also investigated. The efficiency and optimum conditions of UAE were examined through single-factor experiments and Box-Behnken design (BBD). The optimal extraction conditions were identified as follows: acetonitrile as the extraction solvent, extraction temperature of 27°C, extraction time of 3.4min, and ultrasound power of 70 W. Under these conditions, high linearity was achieved for diuron concentrations of 0.01 to 5.0 mg/L, and the purification correlation coefficient was consistently greater than 0.998. Hence, gas chromatography, combined with UAE and BBD, offers superior efficiency extraction, which is sufficiently accurate and precise for pesticide residue analysis. PRACTICAL APPLICATION: We developed an accurate and cost-effective method for detecting diuron (a commonly used herbicide) in soil and sugar samples. We performed experiments to determine the optimum detection conditions for our method. This method can be used for online monitoring of sugar manufacturing processes to ensure food safety and quality.

Occurrence and Toxicological Risk Evaluation of Organochlorine Pesticides from Suburban Soils of Kenya.

The use of organic chemicals in agriculture and manufacturing has raised concerns about the dangers of organochlorine pesticides (OCPs) in the environment. By examining OCPs occurrence in the suburban soils from Kenya, this study revealed the distribution, concentrations, and the threat posed to the environment and human health. A gas chromatography electron capture detector was used to test the pesticides. The hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT) studied in soils of Kapsabet, Voi, and Nyeri towns showed concentrations ranging from 0.03–52.7, 0.06–22.3, and 0.24–24.3 ng/g respectively. The highest concentration of HCHs was in Kapsabet (0.03–48.1 ng/g), whereas the highest DDTs concentration was in Voi (n.d.–15.5 ng/g). Source identification revealed OCPs pollution originated from recent usage of DDT pesticides to control insect-borne diseases and from the use of lindane in agriculture. Correlation test revealed that total organic carbon influenced the presence of pesticides in the soils. The enantiomeric ratios of α-HCH/γ-HCH were <3 indicating the use of lindane while the ratios of DDE/DDT were <1 suggesting recent input of DDT. The cancer risk assessment showed values close to the set risk level of 10−6, suggesting the likelihood of exposure to cancer was not low enough, and control measures need to be established.

Linear toxicokinetic of chlordecone in ewe's serum.

Chlordecone (CLD) is an organochlorine pesticide used in banana fields of the French West Indies between 1972 and 1993. This use resulted in a long-term pollution of soils and the possible contamination of farm animals. Indeed, after involuntary ingestion of soil, CLD is absorbed and consequently leads to contaminated animals. The aim of this study was the determination of CLD half-life and the establishment of the linearity of CLD disappearance kinetics in non-lactating adult's ewes. Chlordecone diluted in cremophor was intravenously administrated to ewes at different doses: 0.04, 0.2, or 1 mg kg-1 body weight (n = 5 for each dose). Blood samples were collected from time t = 0 to time t = 84 days. Serum samples were extracted with a solid-phase extraction and analyzed by electron capture detection gas chromatography. A two-compartmental model was applied to the serum CLD kinetics. An additional statistical analysis was applied to the observed elimination parameters in serum according to the administrated dose, and no significant differences were detected. The linear elimination of CLD between 0.04 and 1 mg kg-1 body weight allowed the possibility of ewe's extrapolation half-life in this dose range. The estimated mean CLD half-life in ewes was 24 days. Overall, the results of this study will be useful to establish decontamination strategies in small ruminants reared in contaminated CLD areas. Graphical abstract Experimental design of the CLD toxicokinetic study in ewes.

Purification of 2,4,6-trinitrotoluene by digestion with sodium sulfite and determination of its impurities by gas chromatography–electron capture detector (GC-ECD)

Unwanted compounds in 2,4,6-trinitrotoluene (TNT) explosive, such as dinitrotoluene (DNT) and TNT isomers, can lead to exudation defects in the ammunition. For this reason, separation and analysis of impurities are valuable. Chemical treatment with sulfite solution is an important method for the purification of TNT. In this paper, TNT was purified by sodium sulfite solution with putting flaked TNT in digestion condition to remove existing impurities, and the effect of four main factors, digestion temperature, digestion time, concentration of sulfite solution and reaction time of sulfite with impurities on this purification process, was statistically investigated and optimized using central composite design of experiment (CCD) by Minitab software. Also, the qualification of final product was characterized by gas chromatography–electron capture detector method. Here, some conventional compounds such as 2,6-DNT, 2,4-DNT, 3,4-DNT, 2,4,5-TNT (γ-TNT), 2,3,4-TNT (β-TNT) and aniline derivatives were identified by standard solutions; then their concentrations were quantitatively determined by internal standard calibration method.

Development of a screening analytical method for the determination of non-dioxin-like polychlorinated biphenyls in chicken eggs by gaschromatography and electron capture detection

ABSTRACTA sensitive and reproducible screening analytical method is here proposed for the determination of six non dioxin-like polychlorinated biphenyls (NDL-PCBs, congener 28, 52, 101, 138, 153, 180) in chicken eggs based on accelerated solvent extraction (ASE) procedure for the fat extraction and determination, a solid phase extraction (SPE) sample clean-up process, and a gas chromatography – electron capture detection (GC-ECD) analysis. The optimized chromatographic separation, in less than 25 min, returned good responses for the six NDL-PCBs in the range of 2.5–60.0 µg L−1, with correlation coefficients always higher than 0.9995. Instrumental limits of detection were between 0.08–0.35 µg L−1, corresponding to 0.05 and 0.23 ng g−1 fat in the matrix, while method detection limits, calculated on spiked egg samples, ranged from 1.6 to 3.5 ng g−1 fat. The method has been extensively validated in terms of selectivity, sensitivity, recovery, precision, ruggedness and measurement uncertainty, following the European Directives.

Exposure profile of mercury, lead, cadmium, arsenic, antimony, copper, selenium and zinc in maternal blood, cord blood and placenta: the Tohoku Study of Child Development in Japan

BackgroundThe effects of prenatal exposure to toxic elements on birth outcomes and child development have been an area of concern. This study aimed to assess the profile of prenatal exposure to toxic elements, arsenic (As), bismuth (Bi), cadmium (Cd), mercury (total mercury (THg), methylmercury (MHg), inorganic mercury (IHg)), lead (Pb), antimony (Sb) and tin (Sn), and essential trace elements, copper (Cu), selenium (Se) and zinc (Zn), using the maternal blood, cord blood and placenta in the Tohoku Study of Child Development of Japan (N = 594–650).MethodsInductively coupled plasma mass spectrometry was used to determine the concentrations of these elements (except mercury). Levels of THg and MeHg were measured using cold vapour atomic absorption spectrophotometry and a gas chromatograph-electron capture detector, respectively.ResultsMedian concentrations (25th–75th) of As, Cd, Pb, Sb, Sn and THg in the maternal blood were 4.06 (2.68–6.81), 1.18 (0.74–1.79), 10.8 (8.65–13.5), 0.2 (0.06–0.40) and 0.2 (0.1–0.38) ng mL−1 and 5.42 (3.89–7.59) ng g−1, respectively. Median concentrations (25th–75th) of As, Cd, Pb, Sb, Sn and THg in the cord blood were 3.68 (2.58–5.25), 0.53 (0.10–1.25), 9.89 (8.02–12.5), 0.39 (0.06–0.92) and 0.2 (0.2–0.38) ng mL−1 and 9.96 (7.05–13.8) ng g−1, respectively.ConclusionsTHg and Sb levels in the cord blood were twofold higher than those in the maternal blood. Cord blood to maternal blood ratios for As, Cd and Sb widely varied between individuals. To understand the effects of prenatal exposure, further research regarding the variations of placental transfer of elements is necessary.

Extraction of carbonyl derivatives from ozonated wastewater samples using hollow fiber liquid phase microextraction followed by gas chromatography-electron capture detection

Herein, a simple and sensitive method was successfully developed for the extraction and quantification of seven carbonyl compounds (acetaldehyde, propanal, butanal, pentanal, hexanal, glyoxal, methylglyoxal) in a number of wastewater samples previously treated by ozonation process. The compounds were initially derivatized (derivatizing reagent (PFBHA)) and then extracted by a hollow-fiber liquid-phase microextraction method (HF-LPME) in the aqueous sample solution. Afterwards, the extraction solvent was withdrawn from the fiber and injected to a gas chromatograph equipped with electron capture detection (GC–ECD). Factors affecting the extraction efficiency of the whole procedure were optimized using a univariate approach. Under the optimal conditions obtained (sample solution pH, 4; organic extraction solvent, dihexylether; stirring rate, 1000 rpm; no salt addition; and extraction time of 40 min), limits of quantification were 0.5–0.8 μg/l for the studied carbonyl compounds. Dynamic linear ranges were 0.5–100 μg/l for five targets (acetaldehyde, propanal, butanal, pentanal and hexanal) and 0.8–80 μg/l for two targets (glyoxal and methylglyoxal). The relative standard deviations (RSDs %) representing the precision of the method were in the range of 6.4–11.9 based on the average of three measurements. Accuracy of the method was also tested by the relative recovery experiments on spiked samples, with results ranging from 85 to 113%. Finally, the method could be used for routine screening of carbonyl compounds in complex matrices.

Statistical optimization for determination of trace amounts of RDX in matrix of HMX using GC-ECD

1,3,5,7-Tetranitro-1,3,5,7-tetrazocane (HMX) is one of the most powerful military explosives that is produced by means of Bechmann method. Simultaneous, 1,3,5-rinitroperhydro-1,3,5-triazine (RDX) as a by-product is produced in this method that affect on the purity and sensitivity of HMX. Using a simple and fast technique is important for determination of trace amounts of RDX in the HMX matrix. The technique of gas chromatography-electron capture detector (GC-ECD) was proposed for these reasons. Because the presence of several parameters in the proposed technique, the experimental design methods of factorial and central composite were used for the experiments of screening and optimization, respectively. The parameters of oven programming, injection volume, injection temperature, carrier gas flow rate, and detector temperature were used in experiments of screening. The analysis of variance and Pareto plots showed that the injection temperature and carrier gas flow rate must be optimized among the parameters. After the screening and optimization of the studied parameters, the selected conditions were oven programming 10 °C min−1, injection volume 1 μL, injection temperature 250 °C, carrier gas (N2) flow rate 3 mL min−1, and detector temperature 300 °C. The calibration curve and detection limit of the optimized method were 10–90 and 1.8 mg L−1, respectively, of RDX in matrix of HMX. The relative standard deviation of the measurement was 1.89%. Finally, the RDX recovery percentages in HMX matrix in the three spiked samples were also calculated.

Representative commodity for six leafy vegetables based on the determination of six pesticide residues by gas chromatography

A residue analytical method was developed for the determination of trichlorfon, chlorpyrifos, dimethoate, β cypermethrin, deltamethrin, and chlorothalonilin in six leafy vegetables by gas chromatography–electron capture detector (GC–ECD) and gas chromatography–flame photometric detector (GC–FPD). The method had a good linearity (R2 ≥ 0.9924) and precision (RSD ≤ 14.0%). The limits of quantification (LOQ) of six pesticides were all 0.01 mg/kg. Average recoveries of six pesticides ranged from 81% to 119%. The developed method was successfully applied to study the initial deposits, degrade characteristics, and terminal residues for six pesticides applied to six leafy vegetables under the same dose of formulation. The half-life of six pesticides was in the range of 0.8–8.8 days. The highest initial deposits, maximal residues, and terminal residues were found on leaf mustard and sweet potato leaves as the same pesticides were applied in different crops. Therefore, leaf mustard can be selected as representative commodity in the same subgroup to realize the residual extrapolation. This conclusion should be considered as a complement on crop classification of China.

Development and application of a dispersive solid-phase extraction method for the simultaneous determination of chloroacetamide herbicide residues in soil by gas chromatography-tandem mass spectrometry (GC-MS/MS)

ABSTRACTIn this study, a convenient and sensitive analytical method based on dispersive solid-phase extraction (dSPE) and gas chromatography-tandem mass spectrometry in tandem was developed for the simultaneous determination of six chloroacetamide herbicides (acetochlor, alachlor, metolachlor, metazachlor, butachlor and pretilachlor) in soil. Parameters that could influence the extraction efficiency such as the varieties of solvents, the amount of solvents and sorbents were investigated. The optimized extractions were performed by mixing 5.0 g of dried soil with 10.0 mL acetonitrile, 10.0 mL deionized water and 4.0 g sodium chloride, and then the extract was purified with 50.0 mg N-propyl ethylenediamine (PSA), 50.0 mg C18, 10.0 mg graphitized carbon black (GCB) and 100.0 mg MgSO4 (5:5:1:10). At 5.0, 25.0 and 100.0 ng g−1 fortification levels for each analyte, the average obtained recoveries ranged from 87.7% to 108.0% with relative standard deviation (RSD) between 3.8% and 10.9%. The soil matrix effect of the six compounds were lower than 11.0%. The linear relation was observed in the range of 5.0–500.0 ng g−1 and the correlation coefficient (R2) of these compounds were higher than 0.998. The detection limits (LODs) were in the range of 0.2–1.0 ng g−1, and the limits of quantification (LOQs) were between 0.8 and 2.2 ng g−1. Comparing with the gas chromatography-electron capture detector (GC-ECD), the GC-tandem mass spectrometry (MS/MS) method can improve the anti-interference ability and thus get better separation of the chloroacetamide herbicides. Additionally, this method was verified to fit for soil samples with broad organic matter range (16.2 to 83.0 g kg−1). The developed method was successfully applied for analysing 26 field soil samples collected from Dianchi lake basin in the southeast of China. About 42.0% soil samples were detected with these herbicides, of which butachlor was the most frequently detected and the highest concentration was up to 137.0 ng g−1 in rape soil.

Dispersive liquid-liquid microextraction of chloroacetic acids from water samples using a syringe-like glass extraction vessel

A syringe-like glass extraction vessel was used for dispersive liquid-liquid microextraction using low-density solvents for the extraction of chloroacetic acids (CAAs, monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid) from water samples. The CAAs were derivatized using n-octanol (extraction solvent) in the presence of sulfuric acid during and after extraction. Gas chromatography–electron capture detection was applied for the detection of n-octyl derivatize of CAAs. The effective parameters on the extraction efficiency, including the volume of extraction solvent, type, and volume of dispersive solvent, sample acidity, salt addition and extraction time were investigated. Also, the time and temperature of the derivatization reaction were optimized. The limits of detection and quantification were in the range of 0.02–6 and 0.05–10 μg L−1, respectively. Tap, river and swimming pool water samples were analyzed by the method. The relative recoveries were from 90 to 119%, with the RSDs being in the range of 2.1–4.7% (n = 3). The satisfactory results revealed the suitability and reliability of the method in determining the CAAs in environmental water samples.

Importance of biogenic volatile organic compounds to acyl peroxy nitrates (APN) production in the southeastern US during SOAS 2013

Abstract. Gas-phase atmospheric concentrations of peroxyacetyl nitrate (PAN), peroxypropionyl nitrate (PPN), and peroxymethacryloyl nitrate (MPAN) were measured on the ground using a gas chromatograph electron capture detector (GC-ECD) during the Southern Oxidants and Aerosols Study (SOAS) 2013 campaign (1 June to 15 July 2013) in Centreville, Alabama, in order to study biosphere–atmosphere interactions. Average levels of PAN, PPN, and MPAN were 169, 5, and 9 pptv, respectively, and the sum accounts for an average of 16 % of NOy during the daytime (10:00 to 16:00 local time). Higher concentrations were seen on average in air that came to the site from the urban NOx sources to the north. PAN levels were the lowest observed in ground measurements over the past two decades in the southeastern US. A multiple regression analysis indicates that biogenic volatile organic compounds (VOCs) account for 66 % of PAN formation during this study. Comparison of this value with a 0-D model simulation of peroxyacetyl radical production indicates that at least 50 % of PAN formation is due to isoprene oxidation. MPAN has a statistical correlation with isoprene hydroxynitrates (IN). Organic aerosol mass increases with gas-phase MPAN and IN concentrations, but the mass of organic nitrates in particles is largely unrelated to MPAN.

Development, validation of QuEChERS-based method for simultaneous determination of multiclass pesticide residue in milk, and evaluation of the matrix effect

Extraction and quantification of pesticide residue from the milk matrix at or below the established maximum residue limit (MRL) is a challenging task for both analytical chemists and the regulatory institutions to take corrective actions for the human health and safety. The main aim of the study is to develop a simple rapid and less expensive QuEChERS extraction and cleanup method for simultaneous analysis of 41 multiclass pesticide residue in milk by gas chromatography-electron capture detector (GC-ECD), followed by confirmation of the residues with gas chromatography-mass spectrometer (GC-MS). Effect of sorbent type, temperature, spiking concentration, matrix effect (ME), measurement uncertainty (MU), inter- and intra-assay repeatability, reproducibility of recovery, and trueness of the results were investigated to validate the effectiveness of the method. Limit of determination (LOD) and limit of quantitation (LOQ) for all the analytes ranged within 0.001–0.02 and 0.002–0.05 µg mL−1, respectively. The % recovery of all the pesticides ranged between 91.38 and 117.56% with relative standard deviation (RSD) below 2.79%. The MU for all the analytes was ≤29% of respective LOQs, and except for few pesticides, the ME was largely negative. The method fulfilled all the SANTE guidelines and thus can be extended for routine analysis of multiclass pesticide residue in milk.