GC-electron Capture Detection Research Articles

Dissipation kinetics, risk assessment, and waiting period of spiromesifen on chili fruits using gas chromatography-electron capture detector.

A supervised field trial was designed in Rajasthan Agricultural Research Institute, Durgapura, Jaipur, Rajasthan, to assess the dissipation and persistence of spiromesifen in chili fruits. Spiromesifen (22.9% suspension concentrate) was sprayed two times at an interval of 10 days at the recommended dose (96 g. a.i. ha-1 ) and double the recommended dose (192 g. a.i. ha-1 ) with four replications. Sampling was done according to the planned interval of days after the second spray. Extraction and cleanup were performed using the modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method and the spiromesifen residue was analyzed by GC-electron capture detector and confirmation performed using GC-MS. The average initial deposit of spiromesifen was 1.207 mg kg-1 and 1.948 mg kg-1 at the recommended and double the recommended dose, respectively. The half-life values of spiromesifen ranged between 2.7 and 3.2 days at the recommended and double the recommended dose. The safe waiting period was calculated for the respective doses and it was concluded that an average of 7 days is safe for picking. The FSSAI (Food Safety and Standards Authority of India) have set the maximum residue limit of 0.1 mg kg-1 for spiromesifen in green chili. The theoretical maximum residue contribution value of spiromesifen was lower than the maximum permissible intake at both the applications on the 0th day. Hence, there will be no adverse effects on human health after consumption of green chilies.

Persistence and dissipation kinetics of novaluron 9.45% + lambda-cyhalothrin 1.9% ZC insecticides in tomato crop under semi-arid region.

In recent decades, fate studies of pesticides have been a topic of interest worldwide due to human health concerns tomato, contain abundant nutritional phytochemicals and lycopene which is known for antioxidant. Tomato is susceptible to many pest, so to overcome from these pests many insecticides are used, leaving residual effects on the crop. So to find out the persistence, the present study was carried out to investigate the residual levels and dissipation behaviour of novaluron 9.45% + lambda-cyhalothrin 1.9% ZC in tomato crop during Rabi session of 2017-18 in randomized block design. The first spray of insecticide was done at fruit formation stage and second spray at 10-day interval at recommended dose @43.31ga.i.ha-1 and double of recommended dose @86.62ga.i.ha-1. The residue of novaluron determined by HPLC (high-performance liquid chromatography) on 0day (two hours after spraying) was 0.154ppm at lower dose and 0.234ppm at higher dose. The residue of lambda-cyhalothrin determined by GC ECD (gas chromatography electron capture detector) at 0day (two hours after spraying) was 0.451ppm at lower dose and 0.849ppm at higher dose. The deposition of novaluron 9.45% +  lambda-cyhalothrin 1.9% ZC was gradually decreased with increasing days after spraying (DAS). The mean initial deposition of the pesticide novaluron and lambda-cyhalothrin was recorded as 0.154mg/kg, 0.451mg/kg, respectively, at the recommended dose @43.31ga.i.ha-1 while at double of recommended dose @86.62ga.i.ha-1 novaluron and lambda-cyhalothrin, the mean initial deposition of 0.234mg/kg and 0.849mg/kg was recorded, respectively. The residue of the novaluron and lambda-cyhalothrin was at BDL (below determination level) (0.01 and 0.05ppm) on 5th and 7th day, respectively, at lower dose (x), whereas at higher dose (2x) it was below determination level on 7th and 10th day, respectively. In soil samples, the residue levels were at below the determination level (0.01mg/kg) for novaluron and (0.05mg/kg) for lambda-cyhalothrin at both doses. The half-life DT50 of novaluron and lambda-cyhalothrin in the tomato fruit was found to be 2days at recommended dose (X) @43.31ga.i.ha-1 for both the pesticide and at double of the recommended dose @86.62g a.i. ha-1 it was 3 and 2days, respectively.

A review of the application of comprehensive two-dimensional gas chromatography MS-based techniques for the analysis of persistent organic pollutants and ultra-trace level of organic pollutants in environmental samples

Abstract Analysis of complex samples in environmental matrices poses extreme challenge for analytical chemists as the number of known and unknown compounds are numerous and have varying physical and chemical properties. The introduction, over the past decade, of comprehensive two-dimensional (2D) gas chromatography (GC × GC) paired with mass spectrometry (MS) has tremendously changed the analytical profiles of ultra-trace levels of organic pollutants from different environmental media. This review article provides a summary of selected articles using comprehensive 2D GC/MS-based methodologies from January 2014 to August 2019. The applications of various MS detectors, such as single (Q) and triple (QqQ) quadrupole, low resolution and high resolution time-of-flight (TOF), and the hybrid (quadrupole TOF-MS), coupled to GC × GC, and their benefits for analyzing persistent and emerging organic pollutants when applied to different environmental matrices were discussed. Emphasis was given to reviewing some applications of GC × GC-electron capture detector (ECD) and GC × GC-μECD within the specified period as these detectors have improved selectivity and sensitivity toward halogenated (bromine and chloride) compounds found in ultra-trace levels of environmental media.

Determination of residues of pesticides, anabolic steroids, antibiotics, and antibacterial compounds in meat products in Oman by liquid chromatography/mass spectrometry and enzyme-linked immunosorbent assay.

Background and Aim:Meat is a rich source of many nutrients and plays a vital role in human life however, meat safety is one of the top priorities of great concern for consumers today. More than 90% of human exposure to harmful materials is due to consumption of contaminated meat products. This study was designed to compare four valid analytical methods for the determination of organochlorine pesticides 2,4 D (2,4-dichlorophenoxyacetic acid), dichlorodiphenyldichloroethylene/dichlorodiphenyltrichloroethane, alachlor, organophosphate, anabolic steroids (progesterone, testosterone, and estrogen), antibiotics (tetracycline, sulfonamides, gentamycin, and cephalexin), antibacterial compounds (Macrolide, ß-Lactam, Chloramphenicol, Sulphur drugs, and Gentamicin) residues in 135 beef, buffalo, and sheep meat samples (fresh, frozen meats, minced, and sausage samples) of local, regional, and international brands available in Omani markets.Materials and Methods:Triplicate meat samples from each brand within each species were extracted with acetonitrile and purified with acetonitrile-saturated n-hexane to remove all impurities. To dry the sample after heating, the residue was passed across a Sep-Pak C18 cartridge for sample cleaning before gas chromatography (GC) (Brand GCMS-QP2010 Plus) coupled with different detectors, including a mass spectrometer or GC-electron capture detector (GC-ECD). Liquid chromatography/mass spectrometry (LC-MS) was also employed for the quantification of the residues in meat products. Enzyme-linked immunosorbent assay (ELISA) kits were employed to assess veterinary drug residues, anabolic steroids, and pesticides. The CHARM II instrument was employed to detect chloramphenicol, gentamicin, sulfa-drug, ß-lactam, and macrolide residues in meat and meat product samples.Results:A thin-layer chromatographic (TLC) method should be considered as another method of choice to determine concentrations of veterinary drugs and anabolic steroids. The TLC results were validated by LC-MS. The three described methods permit the multi-residue analysis of anabolic steroid residue levels of 0.06-1.89 ppb in meat product samples. There were three violative residues of anabolic steroids in red meat products that were above the maximum residue limits (MRLs). Although, the levels of organochlorine pesticides and antibiotic concentrations in meat products were below the MRLs, the long-term consumption is considered a health hazard and will affect the wellbeing of consumers.Conclusion:The four techniques (GC, high-performance liquid chromatography, ELISA and CHARM II) provided results that were reliable and precise for the detection of chessssmical residues in meat and meat products.

A mixed-methods study of pesticide exposures in Breastmilk and Community & Lactating Women\u2019s perspectives from Haryana, India

BackgroundPopulation growth which has resulted in a need for increased crop yields to sustain food security, in addition to the effects of climate change, have led to the widespread use of chemical pesticides. The indiscriminate use of pesticides has in turn led to contamination of the environment, food commodities and bioaccumulation in human tissues, particularly in agrarian regions of India including the northern state of Haryana.MethodsWe conducted a pilot screening study to investigate the presence of organochlorine, organophosphate, and pyrethroid pesticides in breastmilk samples (n = 75) from Haryana, India. Pesticide analyses were conducted using gas chromatography mass spectrometry (GC-MS) for OC and OP pesticides and GC-electron capture detector for pyrethroids. The study was complemented by a qualitative evaluation of maternal and community perceptions, knowledge, attitudes and practices associated with pesticide use and risk of exposure (n = 30 in-depth interviews; n = 9 focus group discussions).ResultsAnalysis of breastmilk showed the presence of p,p’-dichlorodiphenyltrichloroethane (DDT) and p,p’-dichlorodiphenyldichloroethylene (DDE) in 4% (range: <LOQ - 28 μg/L) and 5% (range: < LOQ – 107 μg/L) of samples, respectively. No other pesticides were detected.Our qualitative findings showed that community members commonly held perceptions of pesticides as medicines and poison but acknowledged their widespread use to ensure crop yields. Given the gendered engagement in farming in this setting, lactating women in study communities do not directly handle chemical pesticides, thus lowering risk of inhalation and dermal exposure.ConclusionsIn our small sample, breastmilk pesticide concentrations were low and did not pose a risk to infants. Based on the persistent nature of many organic pollutants and reported widespread use, we recommend more comprehensive and longitudinal investigation of upstream pesticide contamination in the food supply and exposures among mothers and children.Trial registrationCTRI/2017/01/007636, Date Registered: 06/01/2017.CTRI website: http://ctri.nic.in/Clinicaltrials/pdf_generate.php?trialid=17249&EncHid=&modid=&compid=%27,%2717249det%27

Methylmercury Determination in Fish by Direct Mercury Analyzer

There are two methods for quantifying methylmercury (MeHg) in fish using GC-electron capture detection (ECD): AOAC INTERNATIONAL Official Method 988.11 and the Korean Food Code (KFC) method. Both of these methods consume a large amount of chemicals and require long pretreatment times because of several complicated MeHg extraction steps. In this study, a new method for the simple and rapid determination of MeHg in fish has been developed. The method is based on the investigation of oxygen combustion-gold amalgamation using a direct mercury analyzer (DMA) after the complete removal of MeHg by organic extraction and back-extraction to an aqueous medium. The DMA is suitable for the analysis of both solid and liquid materials and has a good detection limit. The developed method was validated by comparing the MeHg recoveries (%) of both certified reference materials and the market-purchased fish samples with the MeHg concentration obtained using the KFC method. The following parameters pertaining to the developed method were established: detection limit, 1.02 μg/kg; LOQ, 3.09 μg/kg; linearity (r), 0.9998; range, 0.1-300 μg/kg; and recovery, 95-97%. Our method is a promising alternative by virtue of its much simpler and faster sample pretreatment procedure, with a MeHg recovery as high as that of the KFC method. The developed method enables the simultaneous analysis of total Hg and MeHg with only DMA equipment.

Chemical compositions, contaminants, and residues of organic and conventional goat milk in Bogor District, Indonesia.

Aim:This study aimed to compare chemical composition and contaminants (pesticide residues, antibiotic residues, and heavy metal residues) between organic and conventional goat milk in Bogor District, West Java Province, Indonesia.Materials and Methods:Milk sampling was carried out from March to August 2018 at six goat farms. The chemical quality of milk was checked using the Lactoscan Ultrasonic Milk Analyzer device. Fatty acids were analyzed using gas chromatography (GC). Pesticide residues in goat’s milk were analyzed using a GC-electron capture detector (GC-ECD). Antibiotic residues were analyzed using bioassay screening test method. The lead (Pb) and arsenic (As) residues were analyzed using the Atomic Absorption Spectrophotometer (AAS).Results:The content of fat, protein, and lactose showed that there was no difference in the composition of goat’s milk between organic and conventional farms. Caprylic acid (C8:0) and capric acid (C10:0) of organic goat milk are higher than conventional goat milk. Stearic acid (C18:0) and linoleic acid (C18:2) of conventional goat milk are higher than organic goat milk. The total fatty acid of organic goat milk is higher than conventional goat milk. Organochlorine pesticide residues were not detected in organic goat milk and conventional goat milk. Tetracycline antibiotic residues were found in one sample (5.56%) of organic goat milk, and macrolides residues were found in two samples (11.11%) of conventional goat milk. Pb residue in organic goat milk is 50 ppb while conventional goat milk is 80 ppb. Residue As in organic goat milk is 70 ppb while conventional goat milk is 110 ppb.Conclusion:There was no chemical composition (fat, protein, and lactose) difference between organic and conventional goat milk. Saturated fatty acid (SFA) in organic goat milk is higher than conventional goat milk. Pesticide residues are not found in both organic and conventional goat milk. Tetracycline antibiotics were found in organic goat milk and macrolide antibiotic groups found in conventional goat milk. Pb and As residues were found in both organic goat milk and conventional goat milk.

Matrix solid-phase dispersion associated to gas chromatography for the assessment in honey bee of a group of pesticides of concern in the apicultural field

A method based on matrix solid-phase dispersion (MSPD) associated to gas chromatography-flame photometric detection (GC-FPD), GC-electron capture detection (GC-ECD) and GC-mass spectrometry (GC–MS) for confirmation purposes, was developed for the determination of a representative group of twelve pesticides in honeybee with particular concern in the apicultural field (fipronil, thiamethoxam, acetamiprid, acrinathrin, metamidophos, dimetoathe, diazinon, chlorpyrifos, methidathion, profenophos, azinphos methyl and coumaphos). Factors influencing the extraction efficiency of MSPD were investigated and optimized through response surface method. The use of octadecylsilyl (C18) sorbent combined with a florisil clean-up and acetonitrile-methanol (99:1) elution was the optimal condition for the extraction of the selected pesticides. Under this condition the recovery of pesticides at the limit of quantification of the method (0.007 to 0.050 μg g−1) ranged from 68 to 102% with RSDs for within-laboratory reproducibility ≤20%. The proposed method was applied to the analysis of honeybees collected in 68 field hives from areas of great apicultural and agricultural development in central Chile. In 65% of these samples eight different pesticides were detected. Pesticides most frequently found were chlorpyrifos (34% of the samples, <0.017–0.067 μg g−1), acrinathrin (32% of the samples, <0.020–0.026 μg g−1) and diazinon (10% of the samples at values <0.015 μg g−1). The incidence of these pesticides in bees can be related to their high employ in central Chile, use to combat the varroosis in hives and hydrophobicity.

Progressive Increase in Disinfection Byproducts and Mutagenicity from Source to Tap to Swimming Pool and Spa Water: Impact of Human Inputs.

Pools and spas are enjoyed throughout the world for exercise and relaxation. However, there are no previous studies on mutagenicity of disinfected spa (hot tub) waters or comprehensive identification of disinfection byproducts (DBPs) formed in spas. Using 28 water samples from seven sites, we report the first integrated mutagenicity and comprehensive analytical chemistry of spas treated with chlorine, bromine, or ozone, along with pools treated with these same disinfectants. Gas chromatography (GC) with high-resolution mass spectrometry, membrane-introduction mass spectrometry, and GC-electron capture detection were used to comprehensively identify and quantify DBPs and other contaminants. Mutagenicity was assessed by the Salmonella mutagenicity assay. More than 100 DBPs were identified, including a new class of DBPs, bromoimidazoles. Organic extracts of brominated pool/spa waters were 1.8× more mutagenic than chlorinated ones; spa waters were 1.7× more mutagenic than pools. Pool and spa samples were 2.4 and 4.1× more mutagenic, respectively, than corresponding tap waters. The concentration of the sum of 21 DBPs measured quantitatively increased from finished to tap to pool to spa; and mutagenic potency increased from finished/tap to pools to spas. Mutagenic potencies of samples from a chlorinated site correlated best with brominated haloacetic acid concentrations (Br-HAAs) (r = 0.98) and nitrogen-containing DBPs (N-DBPs) (r = 0.97) and the least with Br-trihalomethanes (r = 0.29) and Br-N-DBPs (r = 0.04). The mutagenic potencies of samples from a brominated site correlated best (r = 0.82) with the concentrations of the nine HAAs, Br-HAAs, and Br-DBPs. Human use increased significantly the DBP concentrations and mutagenic potencies for most pools and spas. These data provide evidence that human precursors can increase mutagenic potencies of pools and spas and that this increase is associated with increased DBP concentrations.

Pesticide residues analysis in honey using ethyl acetate extraction method: validation and pilot survey in real samples

This paper presents a cost-effective and validated multi residue confirmatory method for the determination of 167 chemically different pesticides and a survey study on Cyprus honey samples. This method uses ethyl acetate for the extraction of pesticides from honey and the determination is performed with liquid chromatography (LC) coupled to mass spectrometry (MS) operating in tandem mode (MS/MS) and with GC–ECD (gas chromatography with electron capture detector) analysis. The LC-MS/MS analytical system is especially important in the analysis of polar and non-volatile pesticides. For the validation of the method, blank honey samples were spiked with 146 pesticides (organophosphorous, carbamates, triazoles, amides, neonicodinoids, strobilurines, phenylureas, bendimidazoles and others) for the LC-MS/MS analysis at three levels: 0.01, 0.05 and 0.1 mg kg−1 and with 21 pesticides for the GC-ECD analysis at two levels: 0.01 and 0.05 mg kg−1for organochlorines and 0.05 and 0.2 mg kg−1for the pyrethroids. As blank sample, a sample of honey which did not contain detectable levels of the analytes sought was used. The validation study was in accordance to the DG SANCO guidelines. The scope of validation included recovery, linearity, limits of quantification and precision. Linearity is demonstrated all along the range of concentration that was investigated with correlation coefficients ≥0.98. Recoveries of the majority of compounds were in the 70%–120% range and were characterised by precision lower or equal to 20%. The validated method was used for a survey of 36 samples of honey produced in different areas of Cyprus and this is the first work on Cypriot honey samples investigating a broad range of pesticides. Only coumaphos was detected at concentrations higher than 0.01 mg kg−1 in the 58.6% of the honey samples analysed for Coumaphos. The results were evaluated in accordance to the provisions of the Commission Regulation (EU) No 37/2010 on pharmacologically active substances and their classification regarding maximum residue limits (MRLs) in foodstuffs of animal origin. The concentrations of coumaphos in all positive samples were at levels much lower than the MRL.

Analysis of Polychlorinated Biphenyls in Biological Samples by Headspace Solid Phase Microextraction Coupled with Gas Chromatography

Based on headspace solid phase microextraction (HS-SPME) procedure coupled with gas chromatography, a method for determination of polychlorinated biphenyls (PCBs) in biological samples was developed. The optimization of factors influencing the performances of SPME was studied in detail. To perform the HS-SPME polydimethylsiloxane (PDMS), polydimethylsiloxane-divinyl benzene (PDMS-DVB) and polyacrylate (PA) fibers were compared on the basis of their absorption capacities for the selected compounds, and PDMS-DVB fiber was selected. The influence of various parameters on PCBs extraction efficiency by HS-SPME was studied using GC-electron capture detector (ECD). The linear range of most compounds was found to be between 1 and 100 μgL−1 and the limits of detection were between 20.1 and 42.3 ngL−1. The reproducibility of the method (n = 6), expressed as relative standard deviation (RSD), was between 4.63 and 9.71%. Finally, the optimization of method was applied to determine selected PCBs in biological samples.

An improved extraction method of rapeseed oil sample preparation for the subsequent determination in it of azole class fungicides by gas chromatography

The distribution of 19 azole class pesticides in hexane/aqueous–organic mixtures systems and rapeseed oil (or oil solution in hexane)/organic solvents has been studied at 20±1°C. The distribution constants (P) and coefficients (D) between hydrocarbon and polar phase are calculated. It is found that all the studied pesticides are hydrophobic, i.e., in hexane–water system logP≫0. Replacement of water by organic solvents results in sharp logP falling, and their values become negative. It is revealed that solutions of strong inorganic acids in anhydrous acetonitrile extract azole class pesticides from hexane and vegetable oils most fully and selectively. In particular, the acidification of acetonitrile causes a drop of D values in 50–2000 times for the majority of the studied pesticides. This phenomenon was used for the development of the improved technique for the quantitative analysis of a widely used azole class pesticides, which can be presented at trace levels in rapeseed oil. The proposed methodology is based on dissociation extraction (DE) of azoles using perchloric acid in anhydrous acetonitrile, with following clean-up of acetonitrile extract from organic impurities by hexane and aqueous solution of dipotassium hydrogen orthophosphate, and final GC–ECD (gas chromatography with electron capture detection) determination of azole fungicides. The values of obtained recoveries were between 85% and 115% with RSD values below 10%. The obtained limits of quantitation, ranged from 3.0 to 300μgkg−1, are below the maximum residue levels (MRLs) set by the European Union for the majority of pesticides. The developed method was successfully applied to different rapeseed oil samples.

Development of an Analytical Procedure for the Determination of Trihalomethanes in Leafy Vegetable by Headspace-SPME Followed by GC-ECD Determination

An analytical procedure for the determination of trihalomethanes (i.e., CHCl3, CHBrCl2, CHBr2Cl, and CHBr3) in leafy vegetable matrices was developed consisting of headspace solid-phase microextraction (HS-SPME) followed by GC-electron capture detector (ECD) determination. Factors affecting the extraction yield were optimized by multivariate methods in two steps. First, a 25-1 fractional factorial design was applied to screen for and assess the effects and interactions of sample mass (g), extraction temperature (°C), extraction time (min), the salting-out effect, and total volume (mL). Second, a response surface methodology design, i.e., central composite design, was applied to optimize the variables found to have a significant impact on the extraction process (extraction time, extraction temperature, and total sample volume), thereby making it possible to simulate the behavior of all the analytes except CHBr3. Finally, the multiple responses were simultaneously optimized using the desirability function. The optimum overall extraction conditions were achieved with an extraction time of 30 min, a temperature of 40 °C, and a total volume of 5 mL. These analytical conditions were validated by spiking plant samples at two concentration levels (2 and 5 mg kg−1), which yielded accurate and precise results for the target analytes. Detection and quantitation limits ranged from 0.09 to 0.64 μg kg−1 and 0.14 to 0.97 μg kg−1, respectively. Finally, chloroform and bromoform were detected in lettuce irrigated with a chlorinated secondary effluent at concentrations of 1.01 and 0.33 μg kg−1, respectively.

Agricultural Practice and Pesticide Residues in Soils and Pool Sediments from the Pendjari Biosphere Reserve Area in Benin, West Africa

One consequence of the shift in land use from traditional food production to cotton production in West Africa is the application of different pesticides. The influence of this practice on the formation of pesticide residues in soils and sediments of seasonal dry pools was investigated in 2008 and 2009 in the region of the Pendjari biosphere reserve in Benin. The protected park area, the buffer zone with some sporadic agricultural practice and the agricultural zone of the Pendjari region were compared. GC–electron capture detector method was used to analyze selected pesticides covering the officially supplied pesticides and some organochlorine compounds. Residues of α‐ and β‐endosulfan, endosulfan sulfate, chlorpyrifos, p,p′‐dichlorodiphenyldichloroethane, p,p′‐dichlorodiphenyldichloroethylene (DDE) were detected in soils of cotton fields and in sediments from adjacent pools within the agricultural and buffer zone. Concentrations were in the range of below detection limit (DL) to 150 µg/kg dry mass (dm) for endosulfan and endosulfan sulfate together and of below DL to 12 µg/kg dm for chlorpyrifos. In pool sediments, concentrations of total endosulfan were in a range of below DL to 47 µg/kg dm. The occurrence of the pesticides was directly linked to the cotton growing season. No residues were detected at the beginning of cotton growing season. Concentration levels of p,p′‐DDE were in the range of below DL to 12 µg/kg dm. No pesticide residues were found in the protected park zone.

Anatomical mercury speciation in bay scallops by thio-bearing chelating resin concentration and GC-electron capture detector determination

The highly toxic methyl-, ethyl- and phenylmercury species that may exist in the three main anatomical parts – the adductor muscle, the mantle and the visceral mass – of bay scallops (Argopecten irradias) were quantitatively released by cupric chloride, zinc acetate, sodium chloride and hydrochloric acid (HCl) under ultrasonic extraction. After centrifugation, the mercury species in the supernatant were concentrated by thio (SH)-bearing chelating resins, eluted with HClO4 and HCl and extracted with toluene. Separation was achieved by capillary GC equipped with programmed temperatures, a constant nitrogen flow and detected by a micro-electron capture detector (μECD). Under optimised conditions, the LODs for methyl-, ethyl- and phenylmercury in bay scallop samples were 1.1, 0.65 and 0.80 ng g−1, respectively. The maximum RSD for three replicate determinations of methyl-, ethyl- and phenylmercury in bay scallop samples were 13.7%, 14.0% and 11.2%, respectively. In the concentration range of 4–200 ng g−1 in bay scallop samples, the calibration graphs were linear with correlation coefficients not less than 0.997. Recoveries for spiked samples were in the range of 92.7–103.5% (methylmercury), 87.5–108.3% (ethylmercury) and 91.6–106.0% (phenylmercury), respectively. The method was verified by the determination of methylmercury in a CRM GBW10029 (Total Mercury and Methyl Mercury in Fish Tissue), with results in good agreement with the certified values. Methylmercury – the only existing species in bay scallops – was successfully determined by the method.

Headspace Solid Phase Microextraction Procedure for the Detection of Polychlorinated Biphenyls in Seawater Sample

Headspace solid phase microextraction combined with gas chromatography (HS-SPME–GC) method has been studied for determination of 7 polychlorinated biphenyls (PCBs) in seawater samples. To perform the HS-SPME polydimethylsiloxane (PDMS) (7, 30 and 100 µm film thickness) fibers were compared on the basis of their absorption capacities for the selected compounds, and PDMS 100 µm film thickness was selected. The influence of various parameters on PCBs extraction efficiency by HS-SPME was studied using GC-electron capture detector (ECD) compared with solid phase. The performance of proposed HS-SPME–GC methodology with respect to linearity, reproducibility and limit of detection (LOD) was evaluated by water spiked with target compounds. The linear range of most compounds was found to be between 0.1 and 100 µgL−1 and the limits of detection were between 15.2 and 63.8 ngL−1. The reproducibility of the method (n = 6), expressed as relative standard deviation (RSD), was between 4 and 10%. Finally, developed procedure was applied to determine selected PCBs in seawater samples.

Phenyl‐functionalized silica‐coated magnetic nanoparticles for the extraction of chlorobenzenes, and their determination by GC‐electron capture detection

We have prepared a solid phase for the extraction of chlorobenzenes (CBs) by coating magnetic (Fe3 O4 ) nanoparticles with silica via a sol-gel process using a mixture of tetraethoxysilane and triethoxyphenylsilane. The nanoparticles were characterized by SEM, energy-dispersive spectroscopy, and X-ray diffractometry. The nanoparticles were used for the extraction of 1,4-dichlorobenzene (1,4-DCB), 1,2,3-trichlorobenzene (1,2,3-TCB), 1,2,4-trichlorobenzene (1,2,4-TCB), and 1,2,3,4-tetrachlorobenzene (1,2,3,4-TeCB) from water, followed by their determination by GC-electron capture detection. Under optimal conditions, enrichment factors ranging from 220 to 360 were obtained. All determination coefficients (r(2)) are >0.99, and linear response is found in range 0.025-1.5 μg/L (at the lower end), and 6-120 μg/L (at the higher end). Detection limits are 6, 10, 11, and 500 ng/L for 1,2,3,4-TeCB, 1,2,4-TCB, 1,2,3-TCB, and 1,4-DCB, respectively. All RSDs are <6% (for n = 5). The method was successfully applied to the determination of CBs in environmental water samples.

Analysis of kresoxim‐methyl and its thermolabile metabolites in Korean plum: An application of pepper leaf matrix as a protectant for GC amenable metabolites

A new method was developed for kresoxim-methyl (parent compound) and its two thermolabile metabolites, BF 490-2 and BF 490-9, in Korean plum, introducing pepper leaf matrix as a natural analyte protectant for GC-amenable metabolites using a GC-electron capture detector. Samples were extracted with a simple and rapid method using a mixture of ethyl acetate-n-hexane (1:1) and salts, and purified via SPE. Due to the elution gap between parent compound and metabolites in the SPE cartridge and matrix interference, kresoxim-methyl was isolated separately from its metabolites. An optimized amount of pepper leaf matrix (0.25 g/mL) was added to the metabolites prior to each injection. Calibration curves were linear over the concentration ranges with coefficient of determination (r(2)) ≥ 0.999. The method was validated in triplicate at two fortification levels, giving recoveries ranging between 74.3 and 101.4%, and RSDs less than 5%. The LOD and LOQ were 0.015 and 0.05 mg/kg, respectively. The method was successfully applied to real samples where kresoxim-methyl residues were detected in field-incurred plum samples. Residues were confirmed using GC-MS.

Application of Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Droplet Multi-residue Method for the Simultaneous Determination of Polychlorinated Biphenyls, Organochlorine, and Pyrethroid Pesticides in Aqueous Sample

Dispersive liquid–liquid microextraction based on solidification of floating organic droplet (DLLME-SFO) technique was successfully applied for simultaneous assay of eight polychlorinated biphenyls, two organochlorine, and four pyrethroid pesticides multi-residue in aqueous samples by using GC-electron capture detection. The effects of various parameters such as kind of extractant and dispersant and volume of them, extraction time, effect of salt addition, and pH were optimized. As a result, 5.0 µL 1-dodecanol was chosen as extraction solvent, 600 µL methanol were used as dispersive solvent without salt addition, pH was adjusted to 7. Under the optimized conditions, the limits of detection (LOD) were ranged from 1.4 to 8.3 ng L−1. Satisfactory linear range was observed from 5.0 to 2000 ng L−1 with correlation coefficient better than 0.9909. Good precisions were also acquired with RSD better than 13.6% for all target analytes. The enrichment factors of the method were ranged from 786 to 1427. The method can be successfully applied to simultaneous separation and determination of three class residues in real water samples and good recoveries were obtained ranging from 76 to 130, 73 to 129, and 78 to 130% for tap water, lake water, and industrial waste water, respectively.

Degradation kinetics and N-Nitrosodimethylamine formation during monochloramination of chlortoluron

The degradation of chlortoluron by monochloramination was investigated in the pH range of 4–9. The degradation kinetics can be well described by a second-order kinetic model, first-order in monochloramine (NH2Cl) and first-order in chlortoluron. NH2Cl was found not to be very reactive with chlortoluron, and the apparent rate constants in the studied conditions were 2.5–66.3M−1h−1. The apparent rate constants were determined to be maximum at pH 6, minimum at pH 4 and medium at alkaline conditions. The main disinfection by-products (DBPs) formed after chlortoluron monochloramination were identified by ultra performance liquid chromatography-ESI-MS and GC-electron capture detector. N-Nitrosodimethylamine (NDMA) and 5 volatile chlorination DBPs including chloroform (CF), dichloroacetonitrile, 1,1-dichloropropanone, 1,1,1-trichloropropanone and trichloronitromethane were identified. The distributions of DBPs formed at different solution pH were quite distinct. Concentrations of NDMA and CF were high at pH 7–9, where NH2Cl was the main disinfectant in the solution. NDMA formation during chlortoluron monochloramination with the presence of nitrogenous salts increased in the order of nitrite<nitrate<ammonium for a given monochloramination and chlortoluron concentration.