Gas Chromatography-electron Capture Detection Research Articles

A novel dispersive micro solid phase extraction using zein nanoparticles as the sorbent combined with headspace solid phase micro-extraction to determine chlorophenols in water and honey samples by GC–ECD

This study presents a new technique, dispersive micro solid phase extraction (DMSPE) combined with headspace solid phase micro-extraction (HS-SPME) for extraction and determination of chlorophenols (CPs) in water and honey samples using a Gas Chromatography–Electron Capture Detector (GC–ECD). Zein nanoparticles were made by liquid–liquid dispersion and applied for the first time as the sorbent phase in DMSPE. In the proposed DMSPE–HS-SPME method, 1% w/v of ethanolic zein solution was added to an aqueous sample and then a dose of the in-situ generated zein nanoparticles was applied to a pre-concentration of target analytes. Thermal desorption of analytes was performed after the isolating sorbent phase, and then HS-SPME was applied for enrichment prior to introducing to gas chromatography. All the important parameters influencing efficiency of the extraction process such effects of salt, pH, sorbent concentration, temperature, sorbent solution volume in DMSPE procedure, extraction temperature, extraction time, desorption temperature and time in the HS-SPME procedure were investigated and optimized. Results showed that under optimum extraction conditions, detection limits (signal to noise ratio=3) were in the range of 0.08–0.6ngmL−1 and evaluations for relative standard deviations (RSDs %) were between 6.62% and 8.36%.

Comparison and analysis of organochlorine pesticides and hexabromobiphenyls in environmental samples by gas chromatography-electron capture detector and gas chromatography-mass spectrometry.

Two analytical methods, gas chromatography-electron capture detector (GC-ECD) and gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS), were evaluated and compared for the measurement of persistent organic pollutants, specifically for 26 organochlorine pesticides and two hexabromobiphenyls, in atmospheric particulate matter and soil samples. The hypothesis tested was that the coelution of non-target compounds may lead to false positives when analyzed by GC-ECD, and that the overestimation associated with these false positives can be eliminated using GC-NCI-MS. The study showed that both methods had satisfactory linearity and reproducibility for the target compounds. Although the sensitivities of GC-ECD for most of the compounds investigated were higher than those observed with the GC-NCI-MS method, the matrices interference was obvious with GC-ECD. There was indeed an apparently high false-positive rate or overestimate when GC-ECD was used for environmental samples, implying that the GC-ECD method has been used with care and that GC-NCI-MS is generally superior for the analysis of trace amounts of these compounds in environmental samples. Based on these results, the sample extraction and cleanup procedures of the GC-NCI-MS method were optimized for achieving acceptable recoveries and less matrices interference.

Occurrence and distribution of polycyclic aromatic hydrocarbons in surface microlayer and subsurface seawater of Lagos Lagoon, Nigeria.

Polycyclic aromatic hydrocarbons (PAHs) in surface microlayer (SML) and subsurface water (SSW) of Lagos Lagoon were investigated using gas chromatography-electron capture detector (GC-ECD) technique to ascertain their occurrence and spatial distribution, origin, enrichment, and carcinogenicity. Total PAH (ΣPAH) concentrations ranged from 9.10 to 16.20 μg L(-1) in the SML and 8.90 to 13.30 μg L(-1) in the SSW. ΣPAH concentrations were relatively higher in the SML than the underlying SSW samples. The enrichment factors (EFs) of ΣPAHs ranged from 0.76 to 1.74 while the EFs of the individual PAHs varied from 0.50 to 2.09. In general, the EFs values calculated in this study were consistent or slightly less than the EFs reported for similar coastal seawater ecosystems. A correlation between the EFs of fluoranthene and pyrene indicated a positive significant value (R = 0.9828, p < 0.0001, n = 6). Source analyses using the phenanthrene/anthracene and fluoranthene/pyrene ratios indicated the dominance of petrogenic-derived PAHs. Furthermore, enhanced concentrations of BaP (strong carcinogenicity) in SML and SSW samples, which resulted in higher EFs, could pose serious ecological and human health risks.

Persistence behaviour of deltamethrin on tea and its transfer from processed tea to infusion

The dynamics and residues of deltamethrin in a tea grown in an open field ecosystem were investigated. The quantification was performed using gas chromatography–electron capture detection (GC–ECD) and confirmed by gas chromatograph–mass spectrometry (GC–MS) in selective ion monitoring (SIM) mode. The method was validated using blank samples spiked at three levels and the results showed that recoveries ranged from 87% to 101% with relative standard deviations (RSD) ranging of 0.7–7.1%. The residues of deltamethrin were found to dissipate following first order kinetics with half-life ranging between 3.04 and 3.54d for two different rates of foliar application. The deltamethrin residues are present in the processed tea are not transferred into the tea infusion during the infusion process, since their water solubility is extremely low. These results can be utilized in formulating the spray schedule and safety evaluation on deltamethrin tea crop.

Determination of Organochlorine Pesticides in Tea Beverage by Directly Suspended Droplet Microextraction Combined with GC-ECD

In this paper, a simple and efficient directly suspended droplet microextraction (DSDME) method has been developed and optimized, which can be applied on extracting organochlorine pesticides (OCPs) in beverage for gas chromatography–electron capture detector (GC-ECD) analysis. The optimal DSDME was adding 100 μL of isooctane into 5 mL of the beverage sample and stirred for 10 min at 1,000 rpm. The relative recoveries of the DSDME method were ranged from 81 to 117 % (relative standard deviations were 2–20 %, n = 5). The limits of detections were 0.8–5.0 ng/L. Furthermore, DSDME was applied to rapidly determine the OCPs in tea beverage and the results suggested that the method can be used as rapid determination of OCPs in the tea beverage.

Preparation of poly(butyl methacrylate-co-ethyleneglyceldimethacrylate) monolithic column modified with β-cyclodextrin and nano-cuprous oxide and its application in polymer monolithic microextraction of polychlorinated biphenyls

A poly(butyl methacrylate-co-ethyleneglyceldimethacrylate) (poly(BMA-EDMA)) monolithic column was prepared with in situ polymerization method and modified with allylamine-β-cyclodextrin (ALA-β-CD) and nano-cuprous oxide (Cu2O). A polymer monolith microextraction method was developed with the modified monolithic column for the preconcentration of polychlorinated biphenyls combined with gas chromatography–electron capture detector. Various parameters affecting the extraction efficiency were investigated and optimized. Under the optimum experimental conditions, we obtained acceptable linearities, low limits of detection, and good intra-day/inter-day relative standard deviations. Because of the hydrophobic properties of β-CD and the porous nano structure of Cu2O, the enrichment capacity of the poly(BMA-EDMA) monolithic column was significantly improved. The extraction efficiency followed the order: poly(BMA-EDMA-ALA-β-CD-Cu2O)>poly(BMA-EDMA-ALA-β-CD)>poly(BMA-EDMA)>direct GC analysis. When applied to the determination of polychlorinated biphenyls in wine samples, low limits of detection (0.09ngmL−1) were obtained under the preoptimized conditions (sample volume 1.0mL, sample flow rate 0.1mLmin−1, eluent volume 0.1mL, and eluent flow rate 0.05mLmin−1). In addition, the present method was employed to determine polychlorinated biphenyls in red wine samples and the accuracy was assessed through recovery experiments. The obtained recovery values were in the range of 78.8–104.1% with relative standard deviations less than 9.0%.

Determination of ten pyrethroids in various fruit juices: Comparison of dispersive liquid–liquid microextraction sample preparation and QuEChERS method combined with dispersive liquid–liquid microextraction

Dispersive liquid–liquid microextraction (DLLME) sample preparation and the quick, easy, cheap, effective, rugged and safe (QuEChERS) method combined with DLLME were developed and compared for the analysis of ten pyrethroids in various fruit juices using gas chromatography-electron capture detection (GC–ECD). QuEChERS–DLLME method has found its widespread applications to all the fruit juices including those samples with more complex matrices (orange, lemon, kiwi and mango) while DLLME was confined to the fruit juices with simpler matrices (apple, pear, grape and peach). The two methods provided acceptable recoveries and repeatability. In addition, the applicabilities of two methods were demonstrated with the real samples and further confirmed by gas chromatography–mass spectrometry (GC–MS).

GC-ECD를 이용한 flutianil 잔류량 분석법 개발 및 확인

Ji-Eun Kwon, Jung-Ah Do, Hyejin Park, Ji-Young Lee, Yoon-Jae Cho,Jae-Ho Oh, Gyu-Seek Rhee, Sang-Jae Lee, and Moon-Ik Chang*Food Safety Evaluation Department, National Institute of Food and Drug Safety Evaluation, MFDSAbstract A sensitive and simple analytical method to identify flutianil residues in agricultural commodities wasdeveloped and validated using gas chromatography-electron capture detection (GC-ECD) and mass spectrometry (GC-MS).The flutianil residues were extracted with acetonitrile, partitioned with dichloromethane, and then purified using a silicasolid-phase extraction (SPE) cartridge. The method was validated using pepper, sweet pepper, mandarin, hulled rice,soybean, and potato spiked with 0.02 or 0.2 mg/kg flutianil. The average recovery of flutianil was 76.5-108.0% with arelative standard deviation of less than 10%. The limit of detection and limit of quantification were 0.004 and 0.02 mg/kg, respectively. The result of recoveries and relative standard deviation were in line with Codex Alimentarius CommissionGuidelines (CAC/GL 40). These results show that the method developed in this study is appropriate for flutianilidentification and can be used to maintain the safety of agricultural products containing flutianil residues.Keywords: flutianil, fungicide, GC-ECD, GC-MS, agricultural commodities

Analysis of iodine content in seaweed by GC-ECD and estimation of iodine intake

Edible seaweed products have been consumed in many Asian countries. Edible seaweeds accumulate iodine from seawater, and are therefore a good dietary source of iodine. An adequate consumption of seaweed can eliminate iodine deficiency disorders, but excessive iodine intake is not good for health. The recommended dietary reference intake of 0.15 mg/d and 0.14 mg/d for iodine has been established in the United States and Taiwan, respectively. In this study, 30 samples of seaweed were surveyed for iodine content. The samples included 10 nori (Porphyra), 10 wakame (Undaria), and 10 kombu (Laminaria) products. The iodine in seaweed was derivatized with 3-pentanone and detected by gas chromatography-electron capture detector (GC-ECD). The method detection limit was 0.5 mg/kg. The iodine content surveyed for nori was 29.3–45.8 mg/kg, for wakame 93.9–185.1 mg/kg, and for kombu 241–4921 mg/kg. Kombu has the highest average iodine content 2523.5 mg/kg, followed by wakame (139.7 mg/kg) and nori (36.9 mg/kg). The GC-ECD method developed in this study is a low-cost alternative to inductively coupled plasma-optical emission spectroscopy for iodine detection in seaweeds. The iodine intake from seaweed in the current survey was calculated and compared with the iodine dietary reference intake of Taiwan. The risk and benefit of seaweed consumption is also discussed.

Evaluation of dewatered sludge properties from a selected municipal sewage treatment plant

An incorrectly maintained sludge management in wastewater treatment plants, may cause a major threat to the natural environment. Sewage sludge and supernatant, as by-products of the sewage treatment process, generate various chemical substances, including toxins. The aim of the study was to determine the physicochemical characteristics of sludge, sampled from a selected municipal wastewater treatment plant of a throughput of 9000 m3/d. The supernatant and water extract of tested sludge were also determined. The tests were carried out in compliance with the accredited methods for municipal sewage sludge. The heavy metal content of tested sludge does not exceed the amounts specified for their use in agriculture and for land reclamation. Taking into consideration the use of polyelectrolytes in the sludge conditioning process, some examinations were performed using a gas chromatography electron-capture detector to determine the polyacryloamide content. Thus the concentration of this compound in the water extract from the sludge after the press was 1.62 μg/L, while in the supernatant from the pressed sludge it was at a level of 0.98 μg/L. In the examined water extract from the pressed sludge, a very high level of dissolved organic carbon was found (TOC = 128.5 mg C/L) as against the permissible value (TOC = 30 mg C/L). For this reason, the waste (pressed sludge) should not be disposed on a landfill site other than the one designed specifically for non-hazardous and neutral wastes.

Cotton-supported graphene functionalized with aminosilica nanoparticles as a versatile high-performance extraction sorbent for trace organic analysis

Cotton fibers were functionalized, following the coating of fibers with graphene oxide (GO), the covalent attachment of aminosilica nanoparticles and the reduction to the cotton-GR-aminosilica material. Employing the cotton-supported graphene (GR)-aminosilica material, a novel and easily applicable extraction mode was put forward. Several groups of analytes were employed such as PAHs, phthalates, musks, phenolic endocrine disrupters and haloacetic acids to test the applicability of the functionalized cotton for extraction purposes. The extraction yields ranged from 76% to 96% corroborating the high degree of affinity of the material for the above groups of compounds while the limits of detection were between 0.06 and 1.10μg/L using gas chromatography-electron capture detection for haloacetic acids and gas chromatography–mass spectrometry for the rest of the analytes. The accuracy of the method was evaluated in fortified lake water at a spiking level of three to ten times the lowest quantifiable concentration and the recoveries varied from 86% to 104% for all the studied analytes. The π–π and hydrophobic interactions, the hydrogen bonding between the functionalized cotton and analytes and the electron polarizability and ionizability of the chemical structures justify the extraction behavior.

Rapid and sensitive determination of the prochloraz residues in the cultivated mushroom, Agaricus bisporus (Lange) Imbach

The QuEChERS (quick, easy, cheap, efficient, rugged, and safe) sample preparation method and gas chromatography-electron capture detector (GC-ECD) were adopted for rapid extraction and determination of prochloraz residues in cultivated mushrooms. The results were further confirmed by using a gas chromatography-mass spectrometry (GC-MS) system. The method showed that there was a good linear relationship with a correlation coefficient of r2 = 0.999 in the concentration ranges from 52.9 to 1000 μg L−1. The limit of detection (LOD) of the GC-ECD method was 15.9 μg kg−1 and the limit of quantification (LOQ) was 52.9 μg kg−1. The data satisfactorily demonstrated the good repeatability of the method with relative standard deviations (RSDs) lower than 20%. The recovery values for spiked mushroom samples were 100.6 ± 1.6% and 105.6 ± 3.9% for 250 and 1000 μg kg−1, respectively. The samples from seven different mushroom growing facilities were analyzed. The residue levels of prochloraz ranged from <LOQ to 105.4 ± 16.9 μg kg−1. Although, this was the first study on determination of prochloraz residues in mushroom samples by GC-ECD after QuEChERS extraction, the adopted method adequately met the validation criteria and was successfully applied to analyze prochloraz residues in the mushroom samples. Therefore, this method could be regarded as a new alternative for routine analysis of trace levels of this most commonly used pesticide in mushroom production.

Solid phase microextraction using a graphene composite-coated fiber coupled with gas chromatography for the determination of acetanilide herbicides in water samples

A graphene composite-coated stainless steel solid-phase microextraction fiber was prepared. The applicability of the fiber was evaluated through the solid-phase microextraction of five acetanilide herbicides (alachlor, acetochlor, pretilachlor, butachlor and metolachlor) in water samples followed by gas chromatography-electron capture detection. Parameters that affect the extraction efficiency, including the extraction time, extraction temperature, pH of the sample solution, stirring rate and desorption conditions were investigated and optimized. The linear response for the analytes was observed in the range from 0.8 to 150.0 μg L−1 with the correlation coefficients (r) ranging from 0.9933 to 0.9970 and the limits of detection (LODs) between 0.06 and 0.10 μg L−1. The single fiber repeatability and fiber-to-fiber reproducibility were less than 6.2% and 11.2%, respectively. The recoveries of acetanilides from water samples by the current method at spiking levels of 10.0 and 100.0 μg L−1 fell in the range from 81.8% to 112.0%.

Simultaneous determination of insecticide fipronil and its metabolites in maize and soil by gas chromatography with electron capture detection

An integrated method for the simultaneous determination of insecticide fipronil and its three metabolites, desulfinyl, sulfide, and sulfone, in maize grain, maize stem, and soil was developed. This three-step method uses liquid-solid extraction with ultrasound or mechanical grinding, followed by liquid-liquid partitioning and florisil solid-phase extraction (SPE) for cleanup. The quantification was conducted by gas chromatography-electron capture detection in triplicate for each sample. The method was validated with five replicates at three fortification concentrations, 0.002, 0.01, and 0.1 mg kg(-1), in each matrix and gave mean recoveries from 83 to 106 % with relative standard deviation ≤ 8.9 %. The limits of quantification (LOQ) were 0.002 mg kg(-1) for the compounds in all matrixes. In the field study in Beijing and Shandong 2012, fipronil-coated maize seeds were planted and the proposed method was applied for checking the possible existence of four compounds in maize and soil samples, but none of them contained residues higher than the LOQs in both application rates. Moreover, the dissipation of fipronil in soil fits first-order kinetics with half-lives 9.90 and 10.34 days in Beijing and Shandong, respectively. Combined with an adequate sample treatment, this technique offers good sensitivity and selectivity in the three complex matrixes. The results could provide guidance for the further research on pesticide distribution and safe use of fipronil as seed coat in cereals.

Estimation of measurement uncertainty of polychlorinated biphenyls, polycyclic aromatic hydrocarbons and organochlorine pesticides in the atmosphere using gas chromatography–mass spectrometry and gas chromatography–electron capture detector

Estimation of uncertainty of measurement is a crucial issue to achieve accurate measurement results. When the target has adverse environmental and health effects, accuracy of the results become more important. POPs are the pollutants that have toxic effects and unfortunately, there is a lack of information about uncertainty of the method for determining POPs in air samples. In this work, uncertainty calculations were carried out for PCBs, OCPs, and PAHs in air samples analyzed by using GC–MS and GC–ECD. The main dominant sources for combined uncertainty were calibration curve, recovery and repeatability. The relative uncertainties were found to be in the range of 23–52% for PCBs, 24–59% for OCPs and 23–90% for PAHs.

A contribution to reduce sampling variability in the evaluation of deoxynivalenol contamination of organic wheat grain

Fusarium head blight caused by different varieties of Fusarium species is one of the major serious worldwide diseases found in wheat production. It is therefore important to be able to quantify the deoxynivalenol concentration in wheat. Unfortunately, in mycotoxin quantification, due to the uneven distribution of mycotoxins within the initial lot, it is difficult, or even impossible, to obtain a truly representative analytical sample. In previous work we showed that the sampling step most responsible for variability was grain sampling. In this paper, it is more particularly the step scaling down from a laboratory sample of some kilograms to an analytical sample of a few grams that is investigated. The naturally contaminated wheat lot was obtained from an organic field located in the southeast of France (Rhône-Alpes) from the year 2008–2009 cropping season. The deoxynivalenol level was found to be 50.6 ± 2.3 ng g–1. Deoxynivalenol was extracted with a acetonitrile–water mix and quantified by gas chromatography-electron capture detection (GC-ECD). Three different grain sampling techniques were tested to obtain analytical samples: a technique based on manually homogenisation and division, a second technique based on the use of a rotating shaker and a third on the use of compressed air. Both the rotating shaker and the compressed air techniques enabled a homogeneous laboratory sample to be obtained, from which representative analytical samples could be taken. Moreover, the techniques did away with many repetitions and grinding. This study, therefore, contributes to sampling variability reduction in the evaluation of deoxynivalenol contamination of organic wheat grain, and then, at a reasonable cost.

Homogeneous Liquid–Liquid Microextraction for Determination of Organochlorine Pesticides in Water and Fruit Samples

A fast and effective preconcentration method for extraction of organochlorine pesticides (OCPs) was developed using a homogeneous liquid–liquid extraction based on phase separation phenomenon in a ternary solvent (water/methanol/chloroform) system. The phase separation phenomenon occurred by salt addition. After centrifugation, the extraction solvent was sedimented in the bottom of the conical test tube. The OCPs were transferred into the sedimented phase during the phase separation step. The extracted OCPs were determined using gas chromatography–electron capture detector. Several factors influencing the extraction efficiency were investigated and optimized. Optimal results were obtained at the following conditions: volume of the consolute solvent (methanol), 1.0 mL; volume of the extraction solvent (chloroform), 55 μL; volume of the sample, 5 mL; and concentration of NaCl, 5 % (w/v). Under optimal conditions, the preconcentration factors in the range of 486–1,090, the dynamic linear range of 0.01–100 μg L−1, and the limits of detection of 0.001–0.03 μg L−1 were obtained for the OCPs. Using internal standard, the relative standard deviations for 1 μg L−1 of the OCPs in the water samples were obtained in the range of 4.9–8.6 % (n = 5). Finally, the proposed method was successfully applied for extraction and determination of the OCPs in water and fruit samples.

Anopheles arabiensis egg treatment with dieldrin for sex separation leaves residues in male adult mosquitoes that can bioaccumulate in goldfish (Carassius auratus auratus).

The sterile insect technique (SIT) is a biological control tactic that is used as a component of area-wide integrated pest management (AW-IPM) programs. The SIT can only be applied against disease-transmitting mosquitoes when only sterile male mosquitoes are released, and the blood-sucking and potentially disease-transmitting females are eliminated from the production line. For Anopheles arabiensis, a potent vector of malaria, a genetic sexing strain was developed whereby females can be eliminated by treating the eggs or larvae with the insecticide dieldrin. To evaluate the presence of dieldrin residues in male mosquitoes designated for SIT releases, a simple, sensitive, and accurate gas chromatography–electron capture detector (GC–ECD) method was developed. In addition, bioaccumulation and food chain transfer of these residues to fish after feeding with treated mosquitoes was demonstrated. The overall recovery from method validation studies was 77.3 ± 2.2% (mean ± relative standard deviation [RSD]) for the mosquitoes, and 99.1 ± 4.4% (mean ± RSD) for the fish. The average dieldrin concentration found in adult male An. arabiensis was 28.1 ± 2.9 µg/kg (mean ± standard deviation [SD]). A range of 23.9 ± 1.1 µg/kg to 73.9 ± 5.2 µg/kg (mean ± SD) of dieldrin was found in the fish samples. These findings indicate the need to reassess the environmental and health implications of control operations with a SIT component against An. arabiensis that involves using persistent organochlorines in the sexing process.

Isolation and characterization of a Bacillus subtilis strain that degrades endosulfan and endosulfan sulfate.

Endosulfan has emerged as a major environmental menace worldwide due to extensive usage and environmental persistence, seeking its remedial by a cheaper and efficient means. Therefore, natural resource (soil) was explored to search a potential candidate for biodegradation of endosulfan. A soil bacterium was enriched and isolated by applying a strong nutritional selection pressure, using a non-sulfur medium supplemented with endosulfan as sole source sulfur. The microbial strain was found to degrade endosulfan as well as its equally toxic metabolite endosulfan sulfate to non-toxic metabolites (endodiol and endosulfan lactone) very efficiently (up to 94.2 %) within 7 days, estimated qualitatively by thin layer chromatography and quantitatively by gas chromatography-electron capture detection methods. The isolate was characterized for its morphological, physiological, biochemical and 16S rRNA sequencing and identified as a new strain of Bacillus subtilis with strain designation AKPJ04, which was deposited with accession number Microbial Type Culture Collection and Gene Bank (MTCC) 8561, at MTCC, Institute of Microbial Technology, Chandigarh, India. The partial 16S rRNA sequence was submitted to Genbank, Maryland, USA, with the accession number EU 258611. The primary investigation for endosulfan degrading gene(s) localization suggested its location on chromosomal DNA.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-013-0176-7) contains supplementary material, which is available to authorized users.

Gas Chromatography-electron Capture Detection Method for Determination of Polyols in the Urine

Polyols or sugar alcohols are sugar-derived metabolites. The origin, metabolic fate and functions of most of them are not clear. The monitoring of polyols can be helpful in the diagnosis and treatment of diseases, especially those of unknown etiology. The main aim of the study was to develop and demonstrate the efficiency, reliability, sensitivity of the gas chromatography - electron capture detection method for the quantification of polyols: D-arabitol, ribitol and erythritol in urine. In the case of polyols there is a problem with the preparation of samples for analysis. Enrichment and separation of analytes and extract purification are difficult because of their relatively high polarity. That is why we have developed the method of sample preparation based on solid phase extraction with using non-porous graphitized carbon. The elaborated method was applied in autistic children in relation to the pentose phosphate pathway metabolism. Keywords: Electron capture detection, Gas chromatography, Graphitized carbon black, Polyols, Solid phase extraction, Urine.