Gas Chromatography-electron Capture Detection Research Articles

Organochlorine pesticides in two fish species from the southern Caspian Sea

In the present research, we aimed to investigate organochlorine toxins accumulated in both Rutilus frisii kutum and Liza aurata captured at the southern Caspian Sea. At six sampling stations, organochlorine toxins were measured in fish tissues by the gas chromatography–electron capture detector (GC-ECD) method. Total organochlorine toxins ranged from 2.102 ppb to 9.033 ppb in L. aurata at the study area. The highest content of total organochlorine toxins was obtained at station 5, whereas the lowest content was achieved at station 4.In L. aurata, lindane showed the highest level among the measured components (1.642 ppb), whereas α-lindane showed the highest mean level of the measured components (0.57 ppb). In this investigation, the total amount of organochlorine compounds in R. frisii kutum was more than that in L. aurata, but these compounds indicated no significant difference between the two types of fishes (p > 0.05). Moreover, the measured components in both types of fishes were lesser than the allowable limit.

Fate, distribution, and bioconcentration of pesticides impact on the organic farms of Cameron Highlands, Malaysia.

Occurrence and distribution of organochlorine pesticides (OCPs), organophosphate pesticides (OPPs), and pyrethroid pesticides (PYRs) residues in the leafy vegetables were analyzed together with the soil samples using gas chromatography-electron capture detector. Edible tissues of vegetables showed detectable residues of these compounds indicating the influence of the conventional farms and nearby organic farms. In the vegetables, the OCPs concentrations were recorded as nd-133.3ng/g, OPPs as nd-200ng/g, and PYRs as nd-33.3ng/g. In the soil, the OCPs concentrations were recorded as nd-30.6ng/g, OPPs as nd-26.6ng/g, and for PYRs as nd-6.7ng/g. Bioconcentration factor (BCF) was higher for the OPPs (0.3) than the OCPs and PYRs (1.1). The OCPs concentration in the vegetables decreased in the following order: spinach > celery > broccoli > cauliflower > cabbage > lettuce > mustard. For OPPs, the concentration decreased in the following order: cauliflower > spinach > celery > cabbage > broccoli > lettuce > mustard and for PYRs as spinach > celery > lettuce > cabbage > broccoli. Principal component analysis indicates that the sources of these pesticides are not the same, and the pesticide application on the vegetables depends on the type of crop. There is a significant positive correlation between OPPs and the soil (r = 0.65) as compared to OCPs and PYRs (r = 0.1) as the vegetables accumulated OPPs more efficiently than OCPs and PYRs.

A sublimate sorbent for stir-bar sorptive extraction of aqueous endocrine disruptor pesticides for gas chromatography-electron capture detection

A dumbbell-shaped magnetic stir-bar with sublimate sorbent was prepared for the stir bar sorptive extraction (SBSE) of pesticides in an aqueous sample prior to gas chromatography-micro-electron capture detection (GC-μECD). Cyclododecane (CDD) was coated onto a magnetic stir-bar surface as a sublimate sorbent, and steel balls were placed on both ends to form a dumbbell-shaped magnetic stir-bar for SBSE. Four EDC pesticides including chlorpyrifos, ethion, bromopropylate, and λ-cyhalothrin in aqueous samples were selected as model species to examine the proposed SBSE and the following desorption.The parameters studied were those affecting the extraction efficiencies including the coating (solvent for CDD and thickness), extraction (sample pH, stirring rate, time, and salting out effect), dissolution solvent volume, and the loss of CDD sublimated in air. The maximum extraction efficiency was obtained under the following conditions. The stir bar (with CDD thickness of 5.2 μm) was added into a 10 mL sample solution (at pH 7) for a 20-min extraction at 600 rpm. Then, the stir bar was gently removed from the sample solution, disassembled, and immersed into a 0.2 mL insert tube consisting of 3 μL hexane to dissolve; 1 μL was used for GC-ECD analysis. The linear ranges were 0.005–5 μg L−1 with coefficients of determination ranging from 0.9950 - 0.9994. Detection limits (based on S/N = 3) of the four EDCs were 0.4–4.5 ngL-1 with a relative standard deviation (RSD) of 2.4–6.3%, and quantitation limits (based on S/N = 5) were 1–15 ngL−1. The relative recoveries of the spiked samples were in the range of 83.2–98.7% with RSDs of 2.1–8.4% in farm field waters. The proposed sublimation sorbent obtained excellent enrichment factors (101–834) and provided a simple, rapid, sensitive, and eco-friendly sample preparation method.

Covalent attachment of phenyl and carboxyphenyl layers derived from diazonium salts onto activated charcoal for the adsorption of pesticides

The past and recent uncontrolled use of organochlorine pesticides imposes serious problems due to their adverse undesired effects in ecosystems. Finding new ways to dispose of these molecules is therefore mandatory. The covalent modification of activated charcoal powder (ACP) by substituted aryl groups can be achieved by reaction with aryl radicals obtained through the sonically induced dediazonation of diazonium salts. Seventeen organochlorine pesticides were adsorbed on ACP covalently grafted with phenyl and carboxyphenyl layers. The sorption percentages of the pesticides onto the carboxyphenyl modified ACPs [measured by GC-ECD (Gas Chromatography – Electron Capture Detector)] were in the range of 90–100% (DDT, δ-HCH, γ-HCH and endrin aldehyde), 80–90% (methoxychlor, endosulfan II, p,p-DDD and β-HCH) and 60–80% (α-HCH, DDE, endosulfansulfate, endrin, endosulfan I, aldrin, heptachlorepoxid, dieldrin and heptachlor). A tentative explanation is given for these differences based on steric effects.

Organochlorine Pesticides and Polychlorinated Biphenyls in Blue Crabs Callinectes sapidus (Rathbun, 1896) from Akyatan Lagoon in the Eastern Mediterranean Region of Turkey.

The aim of this study is to determine the levels of organochlorine-based pesticides and polychlorinated biphenyls in the edible muscle tissue of blue crabs Callinectes sapidus (Rathbun, 1896) that are harvested from Akyatan Lagoon in the Eastern Mediterranean Region of Turkey. The crabs were harvested in October 2010, January 2011 and March 2011. A total of fifty crabs were studied. A quantitative determination of residue levels was carried out through a Gas Chromatography-Electron Capture Detector (GC-ECD), and compared with acceptable contaminant levels. PCBs were the greatest source of contamination.. The predominant compounds were α-HCH, o,p’-DDE, PCB 28 (2,2',4,4'-PCB) and PCB 52 (2,2’,5,5’-PCB), with mean concentrations of 22.39, 59.45, 347.31 and 362.86 ng/gwet weights, respectively. The present work is highly significant and points out a chronic exposure to pollutants in Akyatan Lagoon. This ecosystem is protected under the Ramsar Convention (Convention on Wetlands of International Importance, especially as Waterfowl Habitat).

Evaluating organochlorine pesticide residues in the aquatic environment of the Lake Naivasha River basin using passive sampling techniques

Passive sampling techniques can improve the discovery of low concentrations by continuous collecting the contaminants, which usually go undetected with classic and once-off time-point grab sampling. The aim of this study was to evaluate organochlorine pesticide (OCP) residues in the aquatic environment of the Lake Naivasha river basin (Kenya) using passive sampling techniques. Silicone rubber sheet and Speedisk samplers were used to detect residues of α-HCH, β-HCH, γ-HCH, δ-HCH, heptachlor, aldrin, heptachlor epoxide, pp-DDE, endrin, dieldrin, α-endosulfan, β-endosulfan, pp-DDD, endrin aldehyde, pp-DDT, endosulfan sulfate, and methoxychlor in the Malewa River and Lake Naivasha. After solvent extraction from the sampling media, the residues were analyzed using gas chromatography electron capture detection (GC-ECD) for the OCPs and gas chromatography-mass spectrometry (GC-MS) for the PCB reference compounds. Measuring the OCP residues using the silicone rubber samplers revealed the highest concentration of residues (∑OCPs of 81 (± 18.9 SD) μg/L) to be at the Lake site, being the ultimate accumulation environment for surficial hydrological, chemical, and sediment transport through the river basin. The total OCP residue sums changed to 71.5 (± 11.3 SD) μg/L for the Middle Malewa and 59 (± 12.5 SD) μg/L for the Upper Malewa River sampling sites. The concentration sums of OCPs detected using the Speedisk samplers at the Upper Malewa, Middle Malewa, and the Lake Naivasha sites were 28.2 (± 4.2 SD), 31.3 (± 1.8 SD), and 34.2 (± 6.4 SD) μg/L, respectively. An evaluation of the different pesticide compound variations identified at the three sites revealed that endosulfan sulfate, α-HCH, methoxychlor, and endrin aldehyde residues were still found at all sampling sites. However, the statistical analysis of one-way ANOVA for testing the differences of ∑OCPs between the sampling sites for both the silicone rubber sheet and Speedisk samplers showed that there was no significant difference from the Upper Malewa to the Lake site (P < 0.05). Finally, the finding of this study indicated that continued monitoring of pesticides residues in the catchment remains highly recommended.

Determination of organochlorine compounds in fish liver by ultrasound-assisted dispersive liquid–liquid microextraction based on solidification of organic droplet coupled with gas chromatography-electron capture detection

A simple and rapid method for the extraction of organochlorine compounds (OCs) including poly-chlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in fish liver using ultrasound assisted dispersive liquid–liquid microextraction based on the solidification of floating organic droplet (US-DLLME-SFO) was developed. For reducing the complexity of the matrix, the sample was pre-treated prior to microextraction. Factors affecting US-DLLME-SFO were optimized by using statistical design of experiment (DoE). The analysis was carried out by Gas Chromatography (GC) equipped with micro electron capture detector (μ-ECD). The optimized parameters were 4.8 min of ultrasound, 3.0 mL of Milli-Q and 24 μL of 1-undecanol as an extraction solvent as determined by DoE. US-DLLME-SFO was validated in terms of limit of detection, limit of quantification, dynamic linearity range, coefficient of determination (linearity) and extraction recovery in fish liver for OCs, and the respective values were (1.06-3.84 ng g−1), (3.50-12.67 ng g−1), (1.0–500 ng g−1), (R2 = 0.994-0.999), (88.5-108.4%). Interday and intraday precisions were evaluated as relative standard deviation (% RSD) and the values were ≤10%.

Assessment of Polychlorinated Biphenyls (PCBs) in water, sediments and biota from e-waste dumpsites in Lagos and Osun States, South-West, Nigeria

The levels of PCBs in sediments, water, leachate and aquatic fauna ( Tilapia guineensis , Callinectes amnicola and Cardiosoma armatum ) found in and around e-waste dumpsites in Lagos and Osun States, South-West, Nigeria were analyzed using Gas Chromatography Electron Capture Detector (GC ECD) Agilent 7820A. All the 28 PCBs congeners studied were detected with the Σhexa-PCBs dominating in Lagos (21%) while the Σtetra-PCBs (24%) enriched the samples from Osun State. The concentrations of Σ- PCBs in decreasing order were Lagos: sediment ˃ fish gill ˃ fish muscles ˃ water ˃ crab ˃ leachate and Osun: fish gill ˃ fish muscle ˃ sediment ˃ crab ˃ water ˃ leachate. The concentrations of total indicator PCBs ( Σ7PCBs) in the sediment from Lagos (4.19 μg/kg) and Osun (8.58 μg/kg) exceeded the Canadian Sediment Quality standard threshold effect level (CSQ TEL) (0.03 μg/kg) and the National Oceanic Atmospheric Administration threshold effect level (NOAA TEL) for fresh and marine sediments.. The calculated toxic equivalent quotient (TEQ) for fish from Lagos and Osun (3.7 and 4.4) respectively further suggests a likely occurrence of adverse effects to humans who consume the fish. This study reveals the high health and ecological risks associated with e waste pollution in the aquatic environment. Keywords: e-waste, polychlorinated Biphenyls, aquatic environment, leachate

Organochlorine Compounds with a Low Boiling Point in Desalted Crude Oil: Identification and Conversion

Organochlorine compounds (OOCs) with a low boiling point in desalted crude oil were identified via gas chromatography (GC) with electron capture detection (ECD), and the possibility of their hydrolysis was evaluated thermodynamically under the conditions of industrial distillation of desalted crude oil. Six fractions, namely, gasoline, aviation kerosene, light diesel, heavy diesel, lubricating oil, and residual oil, were obtained via true boiling point distillation. Chlorine concentration results indicated that OOCs with low and high boiling points were concentrated in the gasoline fraction and residual oil, respectively. Qualitative and quantitative analyses of low-boiling-point OOCs, such as carbon tetrachloride, tetrachloroethylene, 1,1,1,3-tetrachloropropane, and 1,2,4-trichlorobenzenem were performed via GC–ECD. The four types of OOCs coexisted in the gasoline, aviation kerosene, and light diesel fractions. Thermodynamic analysis results indicated that the four types of OOCs could hydrolyze to form c...

Atmospheric bromoform at Cape Point, South Africa: an initial fixed-point data set on the African continent

Abstract. Bromoform mixing ratios in marine air were measured at Cape Point Global Atmospheric Watch Station, South Africa. This represents the first such bromoform data set recorded at this location. Manual daily measurements were made during a month-long field campaign (austral spring 2011) using a gas chromatograph-electron capture detector (GC-ECD) with a custom-built front end thermal desorption trap. The measured concentrations ranged between 4.4 and 64.6 (± 22.2 %) ppt with a mean of 24.8 ± 14.8 ppt. The highest mixing ratios recorded here occurred at, or shortly after, low tide. The diurnal cycle exhibited a morning and evening maximum with lower concentrations throughout the rest of the day. Initial analysis of the data presented indicates that the local kelp beds were the dominant source of the bromoform reported. A concentration-weighted trajectory analysis of the bromoform measurements suggests that two offshore source areas may exist. These source areas appear to be centred on the Agulhas retroflection and extend from St Helena Bay to the southwest.

Residue determination of triclopyr and aminopyralid in pastures and soil by gas chromatography-electron capture detector: Dissipation pattern under open field conditions

In this study, a new method for the simultaneous quantitative determination of triclopyr and aminopyralid in forage grass, hay, and soil was developed and validated using gas chromatography coupled with electron capture detector (GC-ECD). In this method, a simple and maneuverable esterification reaction was applied to convert the two acidic herbicides into their ester form with methanol. The target compounds were extracted with 1% hydrochloric acid-acetonitrile, esterified, purified by florisil solid-phase extraction cartridge, and detected in a single run by the GC-ECD. The average recoveries using this method, at different fortified levels, ranged from 80% to 104% with intra-day and inter-day RSDs in the range of 1.2–10.8% and 3.3–10.3% for both the herbicides, respectively. The LODs were below 0.02 mg/kg while the LOQs were below 0.05 mg/kg, both of which were much lower than the maximum residue limits (MRLs) of 25–700 mg/kg in pastures, as established by the USA (the code of federal regulations). The open field dissipation and residual analysis in pastures and soil were conducted with the commercial formulation at two locations. With time, both triclopyr and aminopyralid dissipated via first-order kinetics. In forage grass, both compounds degraded rapidly over the first 14- or 21-d period and at a slow rate over the remainder of experimental days. In soil, they degraded at a relatively slow rate, and dissipated steadily to below or close to the LOQ by 60-d post application. The half-lives of triclopyr were 1.4–1.8 d and 6.2–9.0 d and aminopyralid were 1.7–2.1 d and 8.2–10.6 d in terms of forage grass and soil, respectively. The terminal residue results indicated that on 7 d after the treatment, the residues of aminopyralid and triclopyr in forage grass and hay were lower than the MRLs set by the USA. This work can provide guidance on the reasonable use of these herbicides and also provide an analytical method for the determination of triclopyr and aminopyralid in pasture and soil.

Levels and distribution of pesticide residues in soil and sediments in Eastern Lake Tanganyika environs

The aim of this study was to investigate the types, levels and distribution of pesticide residues in Eastern Lake Tanganyika basin in Tanzania. Water, soil and sediments samples were collected from various sites in Kigoma region. Analyses of cleaned sample extracts were performed using gas chromatographyelectron capture detection (GC-ECD) and gas chromatography-mass spectrometry (GC-MS). Six pesticide residues and metabolites were detected, namely, p,p' -DDT, o,p' -DDT, p,p' -DDE, p,p' -DDD, diazinon and chlorpyrifos. DDT, DDD and DDE were the predominantly detected compounds in all of the samples. Diazinon and chlorpyrifos were detected in soil samples only. The highest concentrations of total DDT in sediments and soil ranged from 10.02 to 116 μg/kg dry weight (dw) and 7.5 to 564.2 μg/kg dw, respectively. Chlorpyrifos and diazinon had concentrations up to 36 and 184 μg/kg dw, respectively. The concentrations of DDT residues were greater in soil samples than in sediments. The highest concentrations of DDT residues were detected in soil samples. The ratios of ( p,p' -DDE + p,p' -DDD)/ p,p' -DDT indicated recent inputs in most samples. The study reveals that there were recent uses of DDT, diazinon and chlorpyrifos in the region. Continued use of DDT indicates risks and may result into serious environmental problems. The area therefore needs serious environmental monitoring. © 2017 International Formulae Group. All rights reserved. Keywords: Pesticide, Lake, soil, sediments, Tanzania

Dissipation kinetics and risk assessment of chlorfenapyr on tomato and cabbage.

A field experiment was conducted over two seasons to evaluate the dissipation kinetics and assess the risks of chlorfenapyr in tomato and cabbage following foliar application of chlorfenapyr 10% SC at 100 and 200ga.i.ha-1. Samples of tomato, cabbage, and soil were analyzed and quantified by gas chromatography-electron capture detector (GC-ECD). The limit of detection (LOD) and limit of quantification (LOQ) of chlorfenapyr were found to be 0.01 and 0.03mgkg-1, respectively, in tomato, cabbage, and soil. The dissipation of chlorfenapyr followed first-order kinetics. The compound showed less persistence in both the vegetables and soil as the calculated half-life values of chlorfenapyr ranged between 4.54 and 7.74days considering two different doses and seasons. The residue was below detection limit in all the untreated plant and soil samples. The pre-harvest interval (PHI) of chlorfenapyr in both the vegetables was determined to be 9-14days regardless of dose or season. The theoretical maximum residue contribution (TMRC) of chlorfenapyr was calculated for tomato and cabbage and was found to be lower than the maximum permissible intake (MPI) of the compound. Therefore, the application of chlorfenapyr at the recommended dose in tomato and cabbage for crop protection seems to be safe from both environmental contamination and consumer safety standpoints.

High-Precision Measurement of N2O Concentration in Ice Cores.

Atmospheric nitrous oxide (N2O) is a greenhouse gas and ozone-depleting substance whose emissions are substantially perturbed by current human activities. Although air trapped in polar ice cores can provide direct information about N2O evolution, analytical precision was not previously sufficient for high temporal resolution studies. In this work, we present a highly improved analytical technique with which to study N2O concentrations in ancient-air-trapped ice cores. We adopt a melt-refreezing method to extract air and use a gas chromatography-electron capture detector (GC-ECD) to determine N2O concentrations. The GC conditions are optimized to improve the sensitivity for detecting N2O. Retrapped N2O in ice during the extraction procedure is precisely analyzed and corrected. We confirmed our results using data from the Styx Glacier ice core in Antarctica by comparing them with the results of a dry-extraction method. The precision estimated from the pooled standard deviation of replicated measurements of the Styx ice core was 1.5 ppb for ∼20 g of ice, a smaller sample of ice than was used in previous studies, showing a significant improvement in precision. Our preliminary results from the Styx Glacier ice core samples have the potential to define small N2O variations (a few parts per billion) at centennial time scales.

A novel liquid chromatography detector based on a dielectric barrier discharge molecular emission spectrometer with online microwave-assisted hydrolysis for determination of dithiocarbamates.

A novel detector for liquid chromatography (LC) for the determination of dithiocarbamate (DTC) fungicides is presented with a miniaturized dielectric barrier discharge-microplasma molecular emission spectrometer and an online microwave-assisted hydrolysis reactor. DTCs in the sample/standard solutions together with SnCl2 were pumped to the reactor to be converted to CS2 with high efficiency, which was then separated from the liquid phase and transformed for the detection of the specific molecular emission at 257.49 nm by the spectrometer. Under optimized conditions, the performance of this new detector was evaluated by its determination of different types of DTC including mancozeb, thiram, zineb, propineb, and metiram, and the limit of detection (LOD) values were found to be in the range 0.1-1.0 μg mL-1. The results from 20 test vegetable and fruit samples determined with the proposed method agreed well with those obtained using the standard headspace gas chromatography-electron capture detector (GC-ECD) method. Preliminary experimental results showed that the proposed method provided slightly higher LOD values than those obtained using GC-ECD. Most importantly, the new LC detector could detect each DTC chemical, whereas the traditional method could not distinguish between analytes of different subclasses of DTC.

Magnetic solid-phase extraction using MIL-101(Cr)-based composite combined with dispersive liquid-liquid microextraction based on solidification of a floating organic droplet for the determination of pyrethroids in environmental water and tea samples

An efficient magnetic metal-organic framework (MOF) material MIL-101(Cr)-based composite (MIL, Matérial Institute Lavoisier) was applied as a sorbent for magnetic solid phase extraction (MSPE) coupled with dispersive liquid-liquid microextraction based on the solidification of floating organic drop (DLLME-SFO) method of trace pyrethroids in environmental water and tea samples. Target analytes were quantified by gas chromatography-electron capture detection (GC-ECD). The variables influencing the performance of both steps, including amount of MIL-101(Cr)-based composite, pH value, ultrasound extraction time, elution solvent, elution/disperser solvent volume, elution time and extraction solvent volume, were systematically investigated. The characteristics of the analytical method were evaluated. A linearity range (r=0.9989–0.9997) was obtained in the range of 0.05–10.0ng/mL. Excellent sensitivity levels were achieved with the detection limits of 0.008–0.015ng/mL and the quantitation limits of 0.028–0.050ng/mL. Under optimal conditions, the method was successfully established for the determination of pyrethroids in real samples with satisfactory recoveries ranging from 78.3–103.6%. Overall, the encouraging method exhibited the advantages of remarkable sensitivity, ease of operation, rapidity, low cost and environmental friendliness.

Dissipation pattern of quinalphos in cauliflower, tomato and bean samples

Quinalphos, an organothiophosphate chemical, is chiefly used as an insecticide. A field experiment was conducted at Bangladesh Agricultural Research Institute (BARI), to study the dissipation of quinalphos in tomato, cauliflower and bean samples when sprayed at its recommended dose and were collected from 0 (2 h after application) to 15 successive days. To determine the residual value of quinalphos, the samples were extracted in quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and run through a gas chromatography-electron capture detector (GC-ECD). Higher, middle and lower concentration calibration curves were obtained with linear correlation coefficient (r2) of 0.998, 0.995 and 0.993, respectively. Limit of detection (LOD) and limit of quantification (LOQ) were found to be 0.009 and 0.027 μg mL−1, respectively. The percentages of the recovery of quinalphos residues in spiked vegetable samples at three different levels (0.625, 2.5 and 5.0 μg mL−1) were in the range of 74–86%. The amount of quinalphos residue in tomato, bean and cauliflower were in the range of 0.05–6.3, 0.05–3.1 and 0.06–6.5 μg g−1 and dissipated below maximum residue limit (MRL; 0.20, 0.20 and 0.50 μg g−1 in cauliflower, tomato and bean) value within 6, 4 and 7 days after application, respectively.

The interaction between atrazine and the mineral horizon of soil: a spectroscopic study

PurposeIn this paper, an attempt was made to explain the long-lasting occurrence of atrazine in soil. Despite the fact that this herbicide has been banned in European Union 10 years ago, it is still detected in the environment.Materials and methodsSoil samples (organic and mineral horizon), SiO2 and Al2O3 sorbents were spiked with atrazine. The ultrasound-assisted extraction coupled with gas chromatography-electron capture detector was performed to establish the atrazine recovery depending on the type of soil horizon and sorbent. Fourier transform infrared spectroscopy (FTIR) analysis was conducted to determine the type of interactions between atrazine and sorbents.Results and discussionThe atrazine recovery was lower for the mineral horizon (15%) compared to the organic horizon (63%). This finding suggests an interaction between atrazine and the mineral components of soil. Therefore, attempts have been made to explain atrazine’s interaction with the main mineral components of soil, SiO2 and Al2O3, and to investigate the influence of pH on atrazine’s behaviour in soil. The atrazine recoveries were 86.5 and 10.7% for Al2O3 and SiO2, respectively. The obtained results demonstrated that the protonated atrazine exhibits stronger interactions with the soil mineral layer (recovery below 0.1%) in comparison to molecular form of atrazine (recovery 86%). FTIR results suggested interactions between atrazine and SiO2. FTIR analysis revealed that 1,3,5-azidine ring interacts with SiO2 molecule.ConclusionsIn acidic soil, atrazine remediation is limited, especially if the soil contains minerals with high SiO2 contents. This situation may cause the long-lasting persistence of atrazine in soil.

Bioconcentration and half-life of quinalphos pesticide in rice-fish integration system in the Mekong Delta, Vietnam

ABSTRACTIn order to determine the distribution and enable the elimination of quinalphos, a popular active pesticide compound used in the Mekong Delta, an experiment was set up in a rice-fish integration system in Can Tho City, Vietnam. Fish was stocked into the field when the rice was two-months old. Quinalphos was applied twice in doses of 42.5 g per 1000 m2. Water, fish and sediment samples were collected at time intervals and analyzed by a Gas Chromatography Electron Capture Detector system. The results show that quinalphos residues in fish muscles were much higher than those of the water and the bioconcentration factor (logBCF) was above 2 for the fish. The half-life of first and second quinalphos applications were 12.2 and 11.1 days for sediment, 2.5 and 1.1 days for silver barb, 1.9 and 1.3 days for common carp, and 1.1 and 1.0 days for water, respectively.

A low-cost biosorbent-based coating for the highly sensitive determination of organochlorine pesticides by solid-phase microextraction and gas chromatography-electron capture detection

In this study, an environmentally friendly and low-cost biosorbent coating was evaluated, for the first time, as the extraction phase for solid-phase microextraction (SPME) supported on a nitinol alloy. The characterization of the new fiber was performed by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The applicability of the biosorbent-based fiber in the determination of δ-hexachlorocyclohexane, aldrin, heptachlor epoxide, α-endosulfan, endrin and 4,4′-DDD in water samples was verified, with separation/detection by gas chromatography coupled to electron capture detection (GC-ECD). The influencing parameters (temperature, extraction time and ionic strength) were optimized simultaneously using a central composite design. The optimum conditions were: extraction time of 80min at 80°C and sodium chloride concentration of 15% (w/v). Satisfactory analytical performance was achieved with limits of detection (LOD) between 0.19 and 0.71ngL−1 and limits of quantification (LOQ) between 0.65 and 2.38ngL−1. The relative recoveries for the analytes were determined using river and lake water samples spiked at different concentrations and ranged from 60% for α-endosulfan to 113% for δ-hexachlorocyclohexane, with relative standard deviations (RSD) lower than 21%. The fiber-to-fiber reproducibility (n=3) was also evaluated and the RSD was lower than 14%. The extraction efficiency obtained for the proposed biosorbent coating was compared to a commercially available DVB/Car/PDMS coating. The proposed fiber provided very promising results, including LODs at the level of parts per trillion and highly satisfactory thermal and mechanical stability.