Gas Chromatography-micro Electron Capture Detector Research Articles

Monitoring of Polychlorinated biphenyls in Surface Water Using QuEChERS Extraction Method with Gas Chromatography-micro Electron Capture Detector

Monitoring of Polychlorinated biphenyls in Surface Water Using QuEChERS Extraction Method with Gas Chromatography-micro Electron Capture Detector

Simultaneous Determination of Polychlorinated Biphenyl 101 (PCB101) and Its Hydroxylated, Methoxylated and Methyl Sulfonated Metabolites in Aquatic Organisms by Solid-Phase Extraction (SPE) and Gas Chromatography–Microelectron Capture Detection (GC-μECD)

Polychlorinated biphenyls (PCBs), a group of persistent organic pollutants, are ubiquitous in the environment. The concentrations of PCBs and their metabolites are crucial to understand their impact on the environment. Here, a simultaneous method is reported to determine PCB101 and its hydroxylated, methoxylated and methyl sulfonated metabolites in aquatic organisms by gas chromatography–microelectron capture detection (GC-μECD). Several operational parameters, including the extraction solvent, volume of concentrated sulfuric acid for lipid removal, elution procedure, and solid-phase extraction (SPE) eluent volume, were optimized for the analytes in the muscle tissue of carp (Carassius auratus). Under the optimum conditions, the linearity of the method was from 2.5 to 100 ng/mL with correlation coefficients (R 2) > 0.9961. The limit of detection was 2.00 μg/kg, and the limit of quantitation was equal to 5.00 μg/kg. The spiked recoveries of the targets in carp muscles were from 84.4% to 104%, and the relative standard deviation (RSD) was from 4.02% to 8.75%. The developed method was successfully applied to different aquatic samples. The precursor and metabolites were simultaneously detected in aquatic products. The metabolites of PCBs were present in marine samples collected from the East China Sea. For the first time, the methoxylated metabolite of PCB101 was identified in aquatic organisms. The results provide support for further study on the environmental properties and biological transmission of PCBs.

Research progress in the application of magnetic solid phase extraction based on carbon based magnetic materials in food analysis

食品中残留的痕量有毒物质严重威胁人体健康,对其进行分析十分必要。然而,食品中有毒物质种类多、量少、基质复杂,需选择适当的样品预处理技术进行提取和净化。磁固相萃取(MSPE)因具有操作简单、省时快速、无需离心过滤、环境友好等优点,被认为是一种高效的样品预处理技术并应用于食品分析中。MSPE中使用的磁性吸附剂的吸附容量和选择性是影响MSPE萃取效率和选择性高低的关键,对所建立分析方法的准确度起着关键作用。碳基磁性材料是具有价格低廉、来源丰富、比表面积大、化学稳定性好、吸附容量高、绿色环保等优点的一类新型功能性磁性材料,可以富集不同性质的有机、无机分析物,在环境分析、生物检测、污染治理等多个领域取得了较大进展。近年来,基于碳基磁性材料的MSPE技术在食品分析预处理领域逐渐得到应用,但尚处于起步阶段,存在巨大的应用潜力。该文以碳基类别(碳纳米管、石墨烯、金属有机骨架衍生碳、活性炭等)为主线,综述了采用MSPE技术,以碳基磁性材料为吸附剂,对食品样品中酯类、真菌毒素、多环芳烃、抗生素、生物碱、酚类、维生素、抗菌药等物质进行萃取,进而采用液相色谱法等进行分析的应用实例,同时阐述了该技术存在的问题,并对其发展方向做出了展望。该综述将为基于碳基磁性材料的MSPE技术在食品分析中的广泛应用提供理论依据和技术支撑。

Evolution of cross-linked polyethyleneimine/SABO®STAB as an efficient sorbent for extraction of pesticides in fruit and vegetable juices

The novel cross-linked polyethyleneimine/SABO®STAB was synthesized and used as an efficient sorbent for dispersive micro-solid phase extraction of pesticides before gas chromatography–micro-electron capture detection. The sorbent was fully characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, Brunauer–Emmett–Teller, and Barrett–Joyner–Halenda techniques which confirmed thermally stable cross-linked polymer composite with large surface area and mesoporous morphology. The significant parameters, including type and volume of desorption solvent, extraction time, sorbent dosage, and pH of the sample solution, were optimized. The analytical characteristics of the method were validated using a matrix-matched calibration method. The linear dynamic range was 0.85–250 µg L−1 with good determination coefficients (R2 > 0.996). The limits of detection were 0.25–0.44 µg L−1. Finally, the method was applied for the determination of chlorpyrifos and hexaconazole in celery and apple juices, and the relative recoveries were in the range of 75–116% with the RSDs of 2.7–3.6%.

Levels of polybrominated diphenyl ethers (PBDEs) in indoor dusts in Lagos and Ibadan, Nigeria

Polybrominated diphenyl ethers (PBDEs) were analysed in dust samples collected from 10 homes, 10 cars, 10 offices and 10 schools in 2 different cities, Lagos and Ibadan, Nigeria. The daily dust ingestion was calculated for all the indoor microenvironment studied. Extraction of PBDEs was by ultrasonication and was analysed on a gas chromatography microelectron capture detector. This represents the first PBDE study in school dust on the African continent and also first PBDE study in Ibadan. Lagos is Africa’s most populated city and Ibadan is the third largest city in West Africa and of historical significance. The concentrations of ΣPBDEs (BDE 28, 47, 99,100,153,154,183 and 209) in homes, cars, offices and schools was 2.24–11500 ng/g; 1.20–258 ng/g; 3.76–687 ng/g and 0–471 ng/g, respectively. Generally, dust samples from Lagos had higher median concentration as compared to Ibadan. BDE-47, BDE-99 and BDE-183 were the most prominent congeners recorded. Interestingly, BDE-209 which is prevalent in dust samples in temperate region had a low concentration in this study (especially in car dust). This may be attributed to the photodegradation of BDE-209 due to Nigeria being a tropical country. samples in Lagos, very high median concentration levels of PBDE was present in-house dusts, with slightly lower PBDE levels recorded in office dust. BDE-100 and BDE-183 were the most prevalent congeners in school dust samples. The median concentration obtained was lower when compared to Australian schools. The concentrations of PBDE in house and office dusts in Nigeria was less than studies in the UK and US but similar to values from South Africa and Egypt. The daily intake of PBDEs from all indoor dust samples were below USEPA reference dose (RfD) for oral exposure for all BDE congeners. For all indoor dust categories, toddlers had the possibility for the highest ingestion rate, and this is of serious concern. Lastly, the method scaled analytical Eco-Scale evaluation and Green Analytical Chemical Procedure Index as “an acceptable green analysis method”.

Determination of polychlorinated biphenyls in honeybee, pollen, and honey samples from urban and semi-urban areas in Turkey.

In recent years, honeybees and bee products such as pollen and honey have been used as bioindicators for monitoring environmental pollution. Unfortunately, there are few studies about polychlorinated biphenyl (PCB) concentrations in honeybees and bee products from Turkey. Honeybee and pollen samples were taken between May and September 2017, and honey samples were taken between July and September 2017 at urban and semi-urban areas in Bursa (Turkey). PCB concentrations measured by gas chromatography-microelectron capture detector (GC-μECD) were found to be 135.46 ± 6.53, 81.47 ± 23.52, and 106.35 ± 21.60ngg-1 dry weight (dw) for honeybee, pollen, and honey samples in the urban area, respectively; and 126.35 ± 26.54, 67.57 ± 27.34, and 118.88 ± 55.28ngg-1 dw for honeybee, pollen, and honey samples in the semi-urban area, respectively. Pearson correlation was made between meteorological parameters and pollutant concentrations. According to the correlation results, a significant relationship was found between the pollen and honey results and the total cloudiness and temperature in the semi-urban area. The coefficient of divergence (COD) and Pearson correlation coefficient (PCC) methods were applied to determine the similarities and differences between the pollutant concentrations and sources of the two areas and the temporal variation. According to these two methods, PCB concentrations and emission sources in honeybee and pollen samples in urban and semi-urban areas were generally different in May and June, and similar in August and September.

Environmental view for chlorothalonil on tomato and pepper fruits and soil field in Egypt: Risk assessment and pre-harvest gap

ABSTRACT The objectives of this study were to determine the residues of chlorothalonil which was sprayed with a recommended dose on tomato, pepper, soil under and the nearest water source and to examine the decline and safety. Recovery for tomato and pepper fruits ranged from 88.27% to 108.01%, 79.81% and 102.57% for soil and nearest water source, respectively. Limit of detection and quantification were 0.01 and 0.05 mg kg−1 respectively.The field trial was carried out in El-Sharkia Governorate, Egypt. Samples were randomly collected at pre-harvest intervals (PHI) of 0 day (1 h), 1, 3, 7, 10, and 15 days, respectively. A gas chromatography micro-electron capture detector method was used to detect residue levels. The data showed that the initial deposits were 2.86, 4.01 mg/kg in tomato and pepper, 0.89, 1.43 mg/kg in soil under tomato and pepper, respectively. The half-lives were found to be 1.79 and 1.83 days for tomato and pepper, respectively, while they were 1.63 days and 2.28 days in soil under tomato and pepper, respectively. No chlorothalonil residues were detected in water samples. Apparently, there is no chlorothalonil risk to consumers.

Extraction and Trace Analysis of Trihalomethanes in Water Samples Using Zein@Fe3O4 Nanocomposite.

This study presents a simple dispersive solid phase extraction (DSPE) technique combined with headspace thermal desorption (HSTD) for extraction and determination of the most significant trihalomethanes (THMs), bromodichloromethane, bromoform, chloroform and dibromochloromethane, in water samples by using Zein@Fe3O4 nanocomposite coupled with gas chromatography/micro electron capture detection (GC-MECD). Various parameters affecting the DSPE-HSTD performance were investigated and optimized. The obtained results revealed that under optimum conditions, LOD and LOQ values were in the range of 0.1-0.36, 0.3-1.08µgL-1, respectively. The intra-day and inter-day precisions of the method at a concentration of 10µgL-1 for each analyte (n = 5) were obtained in the range of 5.69-6.70% and 6.12-7.34%, respectively. Finally, the proposed method was successfully applied for extraction and determination of four THMs in drinking water samples.

Health risk assessment of residential exposure to cypermethrin among young children in agricultural communities in northeastern Thailand

This study aimed to identify factors associated with dermal exposure to cypermethrin and assess the health risks among young children in an agricultural community in Thailand. Face-to-face interviews were conducted with the parents/caregivers of 58 children (aged 1–3 years). Wipe samples were analyzed for cypermethrin by gas chromatography-microelectron capture detection (GC-µECD). Health risk assessments were based on the cypermethrin concentration on the children’s hands and feet. Spearman’s correlation indicated significant associations among cypermethrin concentrations on the hands, feet, floors/wooden beds, and toys (rho = 0.438–0.613, p-value <0.001). Cypermethrin concentrations on the hands were significantly and inversely correlated with the child’s caregiver being the child’s mother and insecticide use (p < 0.01). Concentrations on the feet were significantly correlated with insecticide use (p < 0.05) and showering (p < 0.01). The hazard quotient calculated from dermal exposure via the hands and feet showed no risk for potential noncarcinogenic effects (5.586 × 10−5 in the dry season and 4.301 × 10−4 in the wet season). These findings suggest that young children might not be at risk for cypermethrin exposure through the dermal route. Residential exposure among young children may be reduced by improved hygiene. Health risk assessments of environmental insecticide exposure via the oral and inhalation routes require further investigation.

Hyper-crosslinked polymer nanoparticles as the solid-phase microextraction fiber coating for the extraction of organochlorines

A hyper-crosslinked polymer benzenedimethanol (HCP-BDM) was synthesized and explored as a solid-phase microextraction (SPME) fiber coating material. To prepare the HCP-BDM, 1,4-benzenedimethanol monomer was self-condensed via a simple Friedel-Crafts alkylation reaction. The physical-chemical properties of the HCP-BDM material were characterized by infrared spectroscopy, scanning electron microscopy, thermogravimetric and analysis nitrogen adsorption-desorption isotherms. The HCP-BDM coated fiber demonstrated excellent adsorption performance for some organochlorine pesticides (OCPs). An effective HCP-BDM fiber-based SPME method combined with gas chromatography-micro electron capture detector was established for the analysis of the OCPs from various vegetable samples. The linear ranges were observed from their corresponding limits of quantification (LOQs) to 50 ng g−1 for the OCPs, with correlation coefficients varied from 0.9952 to 0.9992. Their limits of detection at S/N = 3 ranged from 0.058 to 0.14 ng g−1. The single fiber repeatability and fiber-to-fiber reproducibility, expressed as the relative standard deviations (RSDs), were from 3.4% to 8.8% and from 6.7% to 9.6%, respectively. The established method was finally applied to the analysis of the OCPs from cucumber, Chinese cabbage and tomato samples with satisfactory recoveries and repeatability.

Determination of endrin and δ-keto endrin in five food products of animal origin using GC-μECD: A modified QuEChERS approach to traditional detection

A simple quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based method was developed for the analysis of endrin and its metabolite, δ-keto endrin, in five animal-derived food products (chicken, pork, beef, egg, and milk) using a gas chromatography-micro electron capture detector (GC-μECD). Samples were extracted with acidified acetonitrile, salted out with magnesium sulfate and sodium acetate, and finally purified with a dual layer solid-phase extraction cartridge (SPE) that contains both Supelclean ENVI-Carb (upper layer) and primary secondary amine (lower layer) SPE sorbents. A seven-point external calibration curve was constructed both for the solvent and matrix for both compounds. Good linearity was achieved for both analytes, with coefficients of determination (R2) ≥ 0.9960. The limits of detection (LODs) were 0.003 mg/kg, whereas the limits of quantification (LOQ) were 0.01 mg/kg, which were 10 times lower than the extraneous maximum residue limit (EMRL) designated by CODEX Alimentarius for the specified matrices. The method was validated via recovery performances in triplicates, with three fortification levels equivalent to LOQ, 2 × LOQ, and 10 × LOQ. The method provided excellent recoveries, ranging between 75.63 and 117.92%, with relative standard deviations (RSD) ≤ 8.52% for both analytes in various matrices. The developed method was successfully applied to monitor market samples collected from 20 different places throughout the Republic of Korea, and none of the tested analytes were found in the analyzed samples. Conclusively, we could propose that the current method can be used for routine analysis of endrin and δ-keto endrin in any type of fatty food matrix.

Pesticides and hypothyroidism in farmers of plantain and coffee growing areas in Quindio, Colombia

To establish the correlation between hypothyroidism and blood pesticide levels. Cross-sectional study in agricultural workers and their permanent partners in plantain and coffee producing municipalities as reference population. A representative sample was estimated and thyroid function tests were performed using ELISA Stat Fax 303/Plus reader, at a wavelength of 450 nm. Organochlorine pesticide residuality was determined, a dispersive liquid-liquid microextraction (DLLME) assisted by sonication was implemented, and a gas chromatography-micro-electron capture detector (GC-pECD) was used for the analysis. 819 participants, 58.7% men and 41.3% women were included; their average age was 48.1 years. Prevalence of symptomatic hypothyroidism (1.2%) and subclinical hypothyroidism (6.7%) was observed, with a higher prevalence in people older than 60 years (2.6% and 8.9%, respectively). Non-causal association was found between subclinical hypothyroidism and the organochlorine pesticides 4,4'-DDE (sig.0,006), Heptachlor (sig.0,04), and Endosulfan I (sig.0,02). Antiperoxidase (Anti TPO) antibodies ≥60 lU/ml were associated with subclinical hypothyroidism (OR 2.6). The prevalence of hypothyroidism in the studied population is similar to that reported in the literature, and lower than in urban areas. In turn, the prevalence of subclinical hypothyroidism is higher and positive anti-TPO values are related to risk of progression to frank hypothyroidism, which is why follow-up is required in these patients. Three organochlorine pesticides were associated with subclinical hypothyroidism. TSH screening is recommended in people aged 40 and over, especially if they are exposed to the aforementioned agrochemicals.

Magnetic graphene coated inorganic-organic hybrid nanocomposite for enhanced preconcentration of selected pesticides in tomato and grape

The new magnetic graphene based hybrid silica-N-[3-(trimethoxysilyl)propyl]ethylenediamine (MG@SiO2-TMSPED) nanocomposite was synthesized via sol-gel process, and used as an effective adsorbent in magnetic solid phase extraction (MSPE) of three selected pesticides followed by gas chromatography micro-electron capture detection (GC-μECD). The adsorbent was characterized using Fourier transform-infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDXS) techniques. The analytical validity of the developed method was evaluated under optimized conditions and the following figures of merit were obtained: linearity, 1–20μgkg−1 with good determination coefficients (R2=0.995–0.999); limits of detection (LODs), 0.23–0.30μgkg−1 (3×SD/m, n=3); and limits of quantitation (LOQ), 0.76–1.0μgkg−1 (10×SD/m, n=3). The precision (RSD%) of the proposed MSPE method was studied based on intra-day (3.43–8.83%, n=3) and inter-day (6.68–8.37%, n=12) precisions. Finally, the adsorbent was applied to determination of pesticides in tomato and grape samples and good recoveries were obtained in the range from 82 to 113% (RSDs 5.1–8.1%, n=3).

A zeolitic imidazolate framework based nanoporous carbon as a novel fiber coating for solid-phase microextraction of pyrethroid pesticides

A high-surface-area nanoporous carbon (NPC) has been successfully synthesized by using the metal-organic framework ZIF-90 as both the template and precursor together with furfuryl alcohol as a secondary carbon source. The prepared ZIF-90 templated NPC (ZIF-90-NPC) was then coated onto a stainless steel wire by a simple physical adhesion approach to prepare solid-phase microextraction (SPME) fiber. By coupling the ZIF-90-NPC coated fiber-based SPME with gas chromatography-microelectron capture detection (GC-μECD), the developed method gave a large enhancement factor (984-2869), low limit of detection (0.1–0.5ngg−1) and good linearity (0.3–50ngg−1) for the determination of some pyrethroid pesticides (bifenthrin, fenpropathrin, cyhalothrin, permethrin, cyfluthrin, flucythrinate, fenvalerate and deltamethrin) from different fruits and vegetables. The relative standard deviations (RSDs) for six replicate extractions of the pyrethroids by the ZIF-90-NPC coated fiber ranged from 4.3% to 8.0%. The recoveries of the spiked pyrethroids (5ngg−1 and 20ngg−1) from fruit and vegetable samples were in the range of 88.0–104.0% and 86.0–103.5% with the RSDs ranging from 4.8% to 12.9% and 5.0–10.8%, respectively. Besides, the ZIF-90-NPC coated fiber was stable enough for 100 extraction cycles without a significant loss of extraction efficiency. The method was successfully applied to the determination of the pyrethroids in fruit and vegetable samples.

Multipesticide residue levels in UHT and raw milk samples by GC-μECD after QuEChER extraction method.

In the present study, milk samples including raw and ultra-high temperature (UHT) processed milk were analyzed for pesticide residue levels, including five pesticides, viz chloripyrifos, endosulfan (α and β), profenofos and bifenthrin by gas chromatography microelectron capture detector (GC-μECD) after extraction by QuEChERS method. Further confirmation of the pesticide residue was done by GC-MS. The pesticide residual level in raw and UHT milk samples (n = 70) was determined in the range of 0.1-30μgL(-1). All UHT processed milk samples contain pesticide residues within permissible limit set by the World Health Organization (WHO); however, among raw milk samples, chloripyrifos (12%), α (24%), and β (14%) endosulfan were found above the maximum residue limit (MRL). The estimated daily intake (EDI) of these four pesticide residues were also calculated as 1.32, 16.16, 5.30, 10.20, and 9.93μgkg(-1) body weight for chloripyrifos, endosulfan α, profenofos, endosulfan β, and bifenthrin, respectively. It is concluded that the raw milk samples showed higher prevalence of pesticide residues as compared to UHT processed milk. Graphical abstract Determination of pesticide residues in dairy milk by GC-μECD after QuEChERS extraction method.

Accumulation of polychlorinated biphenyls in fish and assessment of dietary exposure: a study in Hyderabad City, India

The objective of this study is to determine the concentrations of polychlorinated biphenyls (PCBs) in different fish species collected from fish outlets in the south Indian city of Hyderabad. The samples of fish extracted by using Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) and concentrations of polychlorinated biphenyls (PCBs, 45 congeners) were determined by gas chromatography-microelectron capture detection (GC-μECD) method. The intake of individual PCB congeners through fish, toxicity equivalence factors (TEFs), hazardous quotient, quantitative assessment, and risk evaluations was estimated in the Indian population. Daily dietary intakes of PCBs at the 95th-percentile-measured concentrations were twice the values of the 50th-percentile-measured concentrations in all socio-economic groups. The dietary intakes of PCBs through fish consumption in middle-income group, low-income group, and industrial laborers (0.023 μg kg(-1) day(-1)), the high-income group (0.031 μg kg(-1) day(-1)), and slum dwellers (0.039 μg kg(-1) day(-1)) exceeded the reference dose. The observed estimated daily intakes (EDIs) of our study for all socio-economic sections (0.0087 μg/kg/day) crossed the cancer benchmark concentration of 0.0003 μg/kg/day. In slum dwellers, the ingestion of fish from freshwater and marine water results in the highest lifetime cancer risks of 4.7 in 100,000 and 7.8 in 100,000, respectively. Ultimately, the concentrations of PCBs were determined high in all of the fish species collected. Risk assessment showed that the fish were highly contaminated with PCBs and may pose health threats to consumers in the city of Hyderabad as well as a lifetime cancer risk.

Development of a simple extraction and oxidation procedure for the residue analysis of imidacloprid and its metabolites in lettuce using gas chromatography

Simple extraction and optimised oxidation procedures were developed for the determination of the total residues of imidacloprid and its metabolites (containing the 6-chloropicolyl moiety) in lettuce using a gas chromatography-micro electron capture detector (GC-μECD). Samples were extracted with acetonitrile, and the extract was then evaporated. The remaining residues were dissolved in water and oxidised with potassium permanganate to yield 6-chloronicotinic acid (6-CAN). The acid residues were further dissolved in n-hexane:acetone (8:2, v/v) and then silylated with MSTFA (N-methyl-N-(trimethylsilyl)trifluoroacetamide) to 6-chloronicotinic acid trimethylsilyl ester. Calibration curves were linear over the concentration ranges (0.025–5μgmL−1) with a determination coefficient (r2) of 0.991. The limits of detection and quantification were 0.015 and 0.05mgkg−1, respectively. Recoveries at two fortification levels ranged between 72.8% and 108.3% with relative standard deviation (RSD) lower than 8%. The method was effective, and sensitive enough to determine the total residues of imidacloprid and its metabolites in field-incurred lettuce samples. The identity of the analyte was confirmed using gas chromatography–tandem mass spectrometry (GC–MS/MS).

Determination of alachlor residues in pepper and pepper leaf using gas chromatography and confirmed via mass spectrometry with matrix protection

Alachlor residues were determined in pepper and pepper leaf, after 49 days of manufacturer-recommended single- and double-dose application to the soil and plant. The samples were extracted with acetonitrile, partitioned with n-hexane, and purified through solid-phase extraction, and finally detected with a gas chromatography-microelectron capture detector. The linearity of the analytical response across the studied range of concentrations (0.05-4.0 µg/mL) was excellent, obtaining coefficients of determination (r(2) ) of 0.999. Recovery studies were carried out on spiked pepper and pepper leaf samples, at two concentrations levels (0.2 and 1.0 mg/kg), with three replicates performed at each level. Mean recoveries of 73.1-109.0% with relative standard deviations of 1.3-2.3% were obtained. The method was successfully applied to field samples, and alachlor residue was found in pepper (0.02 mg/kg) and pepper leaf (0.03 mg/kg), at levels lower than the maximum residue limits (0.2 mg/kg) set by the Korea Food and Drug Administration. The field-detected residues were further confirmed with gas chromatography-mass spectrometry with the help of pepper leaf matrix protection.

Evaluation of Dispersive Liquid-Liquid Microextraction Coupled with Gas Chromatography-Microelectron Capture Detection (GC-µECD) for the Determination of Organochlorine Pesticides in Water Samples

The extraction efficiency of a dispersive liquid-liquid microextraction (DLLME) method coupled with gas chromatography-microelectron capture detection (GC-µECD) for the simultaneous determination of 20 organochlorine pesticides (OCPs) in water samples was evaluated. The optimum conditions of DLLME for OCP measurement in water sample were determined with 10 µL of carbon tetrachloride (CCl(4)) and 1.5 mL of acetone as the extraction and dispersive solvents, respectively, all measurements were conducted under room temperature without the addition of salt. OCPs were extracted with good recoveries (60.35 - 107.89%) by the proposed method, except for heptachlor and aldrin due to the specific physico-chemical properties of these chemicals. Quantitative analysis showed that the relative standard deviations (RSDs) were below 9% and rather wider linear ranges (LRs) of 0.1 - 50 µg/L were obtained. The limits of detection (LODs) were in the range of 0.21 - 11.65 ng/L and no significant matrix effects were observed. Obtained results demonstrated that DLLME coupled with GC-µECD was rapid, convenient and efficient for OCP analysis in water samples.

Development of an Analytical Scheme for the Determination of Pyrethroid Pesticides in Composite Diet Samples

Analysis of an individual's total daily food intake may be used to determine aggregate dietary ingestion of given compounds. However, the resulting composite sample represents a complex mixture, and measurement of such can often prove to be difficult. In this work, an analytical scheme was developed for the determination of 12 select pyrethroid pesticides in dietary samples. In the first phase of the study, several cleanup steps were investigated for their effectiveness in removing interferences in samples with a range of fat content (1-10%). Food samples were homogenized in the laboratory, and preparatory techniques were evaluated through recoveries from fortified samples. The selected final procedure consisted of a lyophilization step prior to sample extraction. A sequential 2-fold cleanup procedure of the extract included diatomaceous earth for removal of lipid components followed with a combination of deactivated alumina and C(18) for the simultaneous removal of polar and nonpolar interferences. Recoveries from fortified composite diet samples (10 microg kg(-1)) ranged from 50.2 to 147%. In the second phase of this work, three instrumental techniques [gas chromatography-microelectron capture detection (GC-microECD), GC-quadrupole mass spectrometry (GC-quadrupole-MS), and GC-ion trap-MS/MS] were compared for greatest sensitivity. GC-quadrupole-MS operated in selective ion monitoring (SIM) mode proved to be most sensitive, yielding method detection limits of approximately 1 microg kg(-1). The developed extraction/instrumental scheme was applied to samples collected in an exposure measurement field study. The samples were fortified and analyte recoveries were acceptable (75.9-125%); however, compounds coextracted from the food matrix prevented quantitation of four of the pyrethroid analytes in two of the samples considered.