Micro-electron Capture Detector Research Articles

Part per quadrillion quantitation of pentaerythritol tetranitrate vapor using online sampling gas chromatography–mass spectrometry

The development of an online sampling method using programmable temperature vaporization gas chromatography with a mass spectrometer detector (PTV-GC/MS) for the analysis of trace pentaerythritol tetranitrate (PETN) vapor is presented. PETN degradation was minimized by optimizing the temperature and flow rates of the vapor sampling infrastructure. Validation of the online method was done using a previously published technique, vapor sampling with Tenax-TA thermal desorption tubes followed by analysis with a thermal desorption system coupled to a programmable temperature vaporization gas chromatograph with a micro-electron capture detector (TDS-PTV-GC/μECD). Trace PETN vapor was generated using state-of-the-art instrumentation known as the TESTbed, located at the US Naval Research Laboratory. For PETN vapor concentrations in the parts per trillionvolume (pptv) range, quantitative results from the TDS-PTV-GC/μECD consistently showed concentrations approximately double that measured by the online PTV-GC/MS method, indicating that sample loss due to additional exposure to the vapor sampling infrastructure occurs when using online sampling. Further utilization of the online PTV-GC/MS system allowed for the quantitation/semi-quantitation of PETN vapor concentrations as low as 260 parts per quadrillionvolume (ppqv) with only 10 min of sampling time.

Verification of nitrous oxide primary standard gas mixtures by gas chromatography and cavity ring-down spectroscopy for ambient measurements in South Africa

Nitrous oxide (N2O) is an important greenhouse gas and is the third-largest contributor to global warming with a global warming potential (GWP) higher than that of carbon dioxide. Ambient N2O is monitored globally and described at nanomole per mole (nmol mol−1) levels. Metrologically traceable and highly accurate N2O gas standards are required to understand the behaviour of the greenhouse gases in the atmosphere and GWP. A group of primary standard gas mixtures (PSGMs) in aluminium cylinder material has been prepared in synthetic air for the calibration of analytical instruments for measurement of N2O at an ambient level. An automatic weighing system with a mass comparator and a fully automated circular rotary plate, as well as a gas filling station, was used in the preparation of the gas mixtures. Analytical methods such as gas chromatography coupled with micro-electron capture detector and cavity ring-down spectroscopy were adopted in the verification process. Four PSGMs in the final preparation step were used to analyse unknown background and filtered air samples at the ambient level. An expanded uncertainty relative to the gravimetric amount fraction was found to be 0.02 %. Results show that the background air samples lie within the calibration range with 329 to 330 nmol mol−1 obtained and 135 nmol mol−1 obtained for filtered air sample.

Хлорорганические соединения в ерше Scorpaena porcus Linnaeus, 1758 в акватории Севастополя (Чёрное море): пространственное распределение и биологический отклик на уровень накопления загрязнителей

Несмотря на запрет применения хлорорганических соединений (ХОС), они до настоящего времени аккумулируются в различных абиотических и биотических компонентах экосистемы Чёрного моря, в том числе в рыбах, вызывая негативные изменения в их метаболизме. Как район активного хозяйственного использования, севастопольская морская акватория подвергается значительному антропогенному воздействию. Уровень содержания ХОС в тканях морского ерша (скорпены) Scorpaena porcus Linnaeus, 1758, ведущего оседлый образ жизни и массово распространённого в прибрежных сообществах, может служить показателем степени загрязнения акватории данным поллютантом, а вид ― удобным индикатором. Газохроматографическим методом с использованием микродетектора электронного захвата определены качественный состав и концентрация хлорорганических пестицидов (п,п’-ДДТ и его метаболитов) и шести индикаторных конгенеров полихлорированных бифенилов в 58 пробах белых мышц, гонад и печени морского ерша, отловленного в 2016–2017 гг. в различных по степени загрязнённости бухтах региона Севастополя (Александровская, Казачья, Стрелецкая, Балаклавская, Ласпи), а также в открытой прибрежной акватории. Для определения отклика организма на уровень загрязнения в печени ерша исследовали комплекс биохимических маркеров: активность аланинаминотрансферазы, аспартатаминотрансферазы и каталазы, содержание альбумина, уровень окислительной модификации белков и концентрацию малонового диальдегида. Содержание ХОС в рыбах зависело от загрязнённости места их обитания. Наибольший уровень ХОС зафиксирован в органах ершей из бухт закрытого типа с затруднённым водообменом (Александровская, Стрелецкая и Балаклавская), наименьший ― в открытой бухте Ласпи. Накопление ХОС в органах ершей зависело от содержания липидов в исследованных тканях. Максимальные концентрации ХОС обнаружены в печени скорпен из всех изученных акваторий, минимальные ― в гонадах рыб из бухт и в белых мышцах особей из открытых районов. Полученные соотношения между содержанием ХОС в печени ерша и показателями комплекса биохимических маркеров свидетельствуют об ослаблении антиоксидантной защиты и о развитии окислительного стресса у рыб в результате накопления ксенобиотиков.

Silica-based magnetic hybrid nanocomposite for the extraction and preconcentration of some organophosphorus pesticides before gas chromatography.

The precise control of pesticide residues in foodstuffs depends significantly on the clean extraction of analytes using specifically designed separation methods. In this study, a one-pot sol-gel process was used for the preparation of a magnetic hybrid silica gel tetraethylortho silicate-cyanopropyltriethoxy silane nanocomposite. The prepared material was characterized using energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, single-point specific surface area, and scanning electron microcopy. The synthesized magnetic hybrid material was used as a solid phase extraction sorbent for the extraction and preconcentration of some organophosphorus pesticides before gas chromatography with a microelectron capture detector. The performance of the proposed magnetic solid-phase extraction technique was validated by linearity (0.05-2ng/mL), correlation coefficients (r2 =0.9993-0.9997), limit of detection (0.02-0.06ng/mL, S/N=3, n=3), and intraday (RSD=1.5-8.7%, n=3) and interday precision (RSD=5.5-9.3%, n=12), while the recovery in real samples and equilibrium adsorption capacity was 72.02-103.84% and 8-20mg/g, respectively. The magnetic solid-phase extraction based on the hybrid nanocomposite revealed a high enrichment factor, an appropriate dynamic range, and great absorptive ability toward the selected organophosphorus pesticides spiked in real water samples.

Electroless-coated magnetic three-dimensional graphene with silver nanoparticles used for the determination of pesticides in fruit samples.

A new type of adsorbent composed of magnetic three-dimensional graphene coated with silver nanoparticles was synthesized by an electroless technique and used in the magnetic solid-phase extraction of selected pesticides (fenitrothion, chlorpyrifos, and hexaconazole) before gas chromatography with a micro-electron capture detector. The adsorbent was characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, vibrating sample magnetometry, and field-emission scanning electron microscopy. The important extraction parameters such as pH, adsorbent dose, extraction time, and desorption conditions were investigated. Under the optimal conditions, the analytical figures of merit were obtained as: linear dynamic range of 0.1-5ng/g with determination coefficients of 0.991-0.996; limit of detection of 0.07-0.13ng/g; limit of quantification of 0.242-0.448ng/g; and the intraday and interday relative standard deviations (C=5ng/g, n=3) were 3.8-8.7 and 6.6-8.9%, respectively. The developed method was successfully applied for analysis of the selected pesticides in tomato and grape with extraction recoveries in the range of 72.8-109.6%.

Deep eutectic solvent based magnetic nanofluid in the development of stir bar sorptive dispersive microextraction: An efficient hyphenated sample preparation for ultra‐trace nitroaromatic explosives extraction in wastewater

A deep eutectic solvent based magnetic nanofluid was coupled with stir bar sorptive dispersive microextraction as a hyphenated sample preparation technique. The neodymium core magnetic stir bar was coated physically with nanofluid of magnetic carbon nanotube nanocomposites and deep eutectic solvents. The prepared nanofluid has magnetic and strong sorbing properties and is compatible with gas chromatography. In this nanofluid, the deep eutectic solvent acts simultaneously as both carrier and stabilizer for magnetic nanotubes. The predominant experimental variables affecting the extraction efficiency of nitroaromatic compounds were evaluated. Under the optimized conditions, the limit of detection and enrichment factor were in the range of 0.2-4.9ng/L and 852-1480, respectively. The relative standard deviations were between 5.6 and 10.2% (n=6). Method validation was performed by both spiking-recovery method and comparison of results with other methods. Finally, the proposed method was successfully applied for the extraction and pre-concentration of nitroaromatic explosives in water samples, followed by determination by gas chromatography with micro-electron capture detection.

Application of deep eutectic solvent based magnetic colloidal gel for dispersive solid phase extraction of ultra-trace amounts of some nitroaromatic compounds in water samples

In this work, colloidal gel of magnetic carbon nanotube and deep eutectic solvent was prepared and used in developing a fast and efficient dispersive solid phase extraction method for enrichment of ultra-trace amounts of nitroaromatic explosives in water samples. In this colloidal gel, deep eutectic solvent is compatible with gas chromatography and acts simultaneously as both carrier and stabilizer for magnetic nanotubes. In this method, nanofluid was dispersed in solution and a dark cloudy suspension was formed which was stable against sedimentation. The extraction efficiency was improved and the extraction time was shortened with no need to shake the sample solution manually or use the external means. A face centered, central composite design was used for efficient optimization of main variables in the extraction procedure. Under the optimized conditions, the limit of detection and enrichment factor were in the range of 0.8–12.4ngL−1 and 267–415, respectively. The relative standard deviations were between 4.6% and 8.5% (n=6). Method validation was performed by both spiking–recovery method and comparison of results with other methods. The method followed by gas chromatography with micro-electron capture detector (GC-μECD), was successfully applied for determination of nitroaromatic explosives in water samples.

Occurrence and Health Risk of Patulin and Pyrethroids in Fruit Juices Consumed in Bangkok, Thailand

The mycotoxin patulin (PAT) is well known as a natural contaminant of apple- and other fruit-based products. Pesticides are a group of chemicals abundantly used in agriculture to maximize productivity by protecting crops from pests and weeds. Because of their harmful health effects, PAT and pesticides are strictly monitored. The current study was undertaken to investigate the significance of PAT and pyrethroid insecticide contamination in a variety of fruit juices in Bangkok. To do this, a total of 200 fruit juice samples, consisting of 40 samples each of apple, apricot, peach, pineapple, and grape juice, were collected from supermarkets in Bangkok, Thailand. PAT contamination in a variety of fruit juices was detected using validated liquid chromatography-tandem mass spectrometry, and pyrethroid insecticides (cypermethrin, cyfluthrin, and flumethrin) were analyzed using a gas chromatography equipped with micro-electron capture detector. The survey found that PAT concentrations were lower than the maximum residue limit established by European Union. The results of the present study suggest that the risk of exposure to harmful levels of PAT, cypermethrin, cyfluthrin, and flumethrin in fruit juices is very low in urban areas of Thailand.

Residualidad de fitosanitarios en tomate y uchuva cultivados en Quindío (Colombia)

En este trabajo se determinó la residualidad de plaguicidas organofosforados (OF) y organoclorados (OC) en los frutos de dos solanáceas comúnmente consumidas en la dieta diaria de la población del departamento del Quindío (Colombia): tomates (Lycopersicon esculentum Mill) cosechados en cultivos regionales y uchuvas (Physalis peruviana, L.) obtenidos en mercados de cadena. Con el fin de evaluar la calidad con la que se comercializan estos frutos, se midieron parámetros fisicoquímicos tales como el pH y la concentración de sólidos solubles (°Bx). El análisis de los plaguicidas en piel y pulpa de ambos frutos se realizó mediante cromatografía de gases con detección por microcaptura de electrones (GC-μ-ECD), empleando técnicas de extracción en fase sólida como pretratamiento de muestra. Como resultado del análisis cromatográfico se encontró la presencia de un total de 10 plaguicidas OF y OC tanto en la piel como en la pulpa de ambos frutos, algunos de ellos en concentraciones mayores a 0,13 ppm en tomate y 0,39 ppm en uchuva. Los resultados obtenidos en este estudio sugieren una alta residualidad de este tipo de fitosanitarios y ponen de manifiesto el uso desmesurado de estas sustancias en el cultivo de frutos de consumo masivo como el tomate y la uchuva. Esto revela el uso de malas prácticas agrícolas y la falta de un control más riguroso sobre el empleo de estos agroquímicos.

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 New Method for the Fast Analysis of Trihalomethanes in Tap and Recycled Waters Using Headspace Gas Chromatography with Micro-Electron Capture Detection.

Chemical disinfection of water supplies brings significant public health benefits by reducing microbial contamination. The process can however, result in the formation of toxic compounds through interactions between disinfectants and organic material in the source water. These new compounds are termed disinfection by-products (DBPs). The most common are the trihalomethanes (THMs) such as trichloromethane (chloroform), dichlorobromomethane, chlorodibromomethane and tribromomethane (bromoform); these are commonly reported as a single value for total trihalomethanes (TTHMs). Analysis of DBPs is commonly performed via time- and solvent-intensive sample preparation techniques such as liquid–liquid and solid phase extraction. In this study, a method using headspace gas chromatography with micro-electron capture detection was developed and applied for the analysis of THMs in drinking and recycled waters from across Melbourne (Victoria, Australia). The method allowed almost complete removal of the sample preparation step whilst maintaining trace level detection limits (>1 ppb). All drinking water samples had TTHM concentrations below the Australian regulatory limit of 250 µg/L but some were above the U.S. EPA limit of 60 µg/L. The highest TTHM concentration was 67.2 µg/L and lowest 22.9 µg/L. For recycled water, samples taken directly from treatment plants held significantly higher concentrations (153.2 µg/L TTHM) compared to samples from final use locations (4.9–9.3 µg/L).

MEASUREMENT OF NITROUS OXIDE IN A NITROGEN MATRIX USING GAS CHROMATOGRAPHY WITH MICROELECTRON CAPTURE DETECTION: VALIDATION OF ANALYTICAL METHOD

Atmospheric nitrous oxide (N2O) as one of the most potent greenhouse gases significantly contributes to the global warming effect. Therefore, an accurate and valid measurement method for monitoring its environmental release is of great importance. In this study, an analytical method for the measurement of N2O in a nitrogen (N2) matrix using gas chromatography and microelectron capture detection (GC‐μECD) has been validated. The analytical method was validated in terms of some performance parameters such as system suitability, precision (repeatability and reproducibility), linearity, limit of detection (LoD) and limit of quantitation (LoQ), accuracy and method robustness. The results show that the GC system was found to be suitable for the measurement of N2O in the N2 matrix. The repeatability and reproducibility of the method were found to have %RSD of 1.42 and 0.71, respectively, indicating that the method is repeatable and reproducible for N2O measurement. The linearity of the method was excellent, having the R2 value of 0.9998. The LoD and LoQ of the method were found to be 0.10 and 0.34 µmol mol-1, respectively. Evaluation of method accuracy showed that the method is also accurate for the measurement of N2O in the N2 matrix. The method’s roughness indicated that the method was quite stable and unaffected by slight changes in the experimental conditions. From this study, it can be concluded that the validated method can be used in testing laboratory for internal quality assurance programs purposes related to the measurement of N2O in N2 matrix.

Elevated Concentrations of 4-Bromobiphenyl and 1,3,5-Tribromobenzene Found in Deep Water of Lake Geneva Based on GC×GC-ENCI-TOFMS and GC×GC-μECD.

We quantified the concentrations of two little-studied brominated pollutants, 1,3,5-tribromobenzene (TBB) and 4-bromobiphenyl (4BBP), in the deep water column and sediments of Lake Geneva. We found aqueous concentrations of 625 ± 68 pg L–1 for TBB and 668 ± 86 pg L–1 for 4BBP over a depth range of 70–191.5 m (near-bottom depth), based on duplicate measurements taken at five depths during three separate 1 month sampling periods at our sampling site near Vidy Bay. These levels of TBB and 4BBP were 1 or 2 orders of magnitude higher than the quantified aqueous concentrations of the components of the pentabrominated biphenyl ether technical mixture, which is a flame retardant product that had a high production volume in Europe before 2001. We observed statistically significant vertical concentration trends for both TBB and 2,2′,4,4′,6-pentabromobiphenyl ether in the deep water column, which indicates that transport and/or degradation processes affect these compounds. These measurements were enabled by application of a comprehensive two-dimensional gas chromatograph coupled to an electron capture negative chemical ionization time-of-flight mass spectrometer (GC×GC-ENCI-TOFMS) and to a micro-electron capture detector (GC×GC-μECD). GC×GC-ENCI-TOFMS and GC×GC-μECD were found to be >10× more sensitive toward brominated pollutants than conventional GC×GC-EI-TOFMS (with an electron impact (EI) ionization source), the latter of which had insufficient sensitivity to detect these emerging brominated pollutants in the analyzed samples. GC×GC also enabled the estimation of several environmentally relevant partitioning properties of TBB and 4BBP, further confirming previous evidence that these pollutants are bioaccumulative and have long-range transport potential.

Toxicokinetics of the broad-spectrum pyrethroid insecticide deltamethrin in broiler chickens

ABSTRACT1. The aim of this study was to examine single-dose toxicokinetics of deltamethrin, a broad-spectrum pyrethroid insecticide, for treatment of broiler chickens.2. Twenty male broiler chickens were used. Animals were divided into two groups, each comprising 10 animals. An intravenous dose of 0.75 mg of deltamethrin/kg body weight was given intravenously to the first group and the same dose (0.75 mg/kg body weight) was administered by intracrop by gavage to the second group. Blood samples were also collected at specified intervals.3. Serum deltamethrin levels were measured via micro-electron capture detection with gas chromatography equipment. According to the serum deltamethrin level-time curve, deltamethrin tended to distribute according to a two-compartment open model.4. The half-life at β phase (t1/2β), mean residence time (MRT) and area under the concentration time curve in 0-∞ (AUC0→∞) values after intravenous application of deltamethrin were 4.00 ± 0.76 h, 4.65 ± 0.75 h and 702.27 ± 236.07 ng h/ml, respectively. Furthermore, the absorption half-life (t1/2a), maximal concentration in serum after intracrop administration (Cmax), time needed to reach Cmax (tmax), t1/2β, MRT and AUC0→∞ values after intracrop application of deltamethrin were determined to be 0.18 ± 0.06 h, 19.65 ± 4.58 ng/ml, 0.70 ± 0.10 h, 7.27 ± 1.36 h, 10.46 ± 1.84 h and 153.33 ± 30.83 ng h/ml, respectively. The bioavailability of deltamethrin was 21.83%.5. It was concluded that deltamethrin was rapidly but incompletely absorbed after intracrop administration and bioavailability was at a low level. The t1/2β and MRT of the deltamethrin were short for both intracrop and intravenous applications, and the risk of toxic and residual effects of deltamethrin is therefore limited.

Occurrence of fungicide residues on Argentinean blueberry fruit and juice samples.

Azoxystrobin, boscalid, cyprodinil, fludioxonil and pyraclostrobin are fungicides commonly used in Argentina against different fungus contaminations in the blueberry field. The presence of these fungicides was investigated in 50 samples of blueberry fruit and 15 samples of blueberry juice purchased in Argentina. Fungicide residues were determined by solid-phase microextraction (SPME) coupled to gas chromatography with micro-electron capture and nitrogen phosphorous detector. The average concentrations of azoxystrobin were 48 g/kg in blueberry fruit. Average of boscalid were 43 and 239 g/kg, of cyprodinil 1581 and 852 g/kg, of fludioxonil 1077 and 2842 g/kg, and of pyraclostrobin 578 and 3414 g/kg, in fruits and juice respectively. The higher concentrations of fungicides were found in those cases where the time between the application of the compound and the fruit’s commercialization was shorter than the fungicide’s half-life.

The quantification of short-chain chlorinated paraffins in sediment samples using comprehensive two-dimensional gas chromatography with μECD detection.

The analysis of persistent organic pollutants in environmental samples is a challenge due to the very large number of compounds with varying chemical and physical properties. Chlorinated paraffins (CPs) are complex mixtures of chlorinated n-alkanes with varying chain lengths (C10 to C30) and degree of chlorination (30 to 70% by weight). Their physical-chemical properties make these compounds persistent in the environment and able to bioaccumulate in living organisms. Comprehensive two-dimensional gas chromatography (GC × GC) coupled with micro-electron capture detection (μECD) was used to separate and quantify short-chain chlorinated paraffins (SCCP) in sediment samples. Distinct ordered bands were observed in the GC × GC chromatograms pointing to group separation. Using the Classification function of the ChromaTOF software, summary tables were generated to determine total area counts to set up multilevel-calibration curves for different technical mixes. Fortified sediment samples were analyzed by GC × GC-μECD with minimal extraction and cleanup. Recoveries ranged from 120 to 130%. To further validate the proposed method for the analysis of SCCPs, the laboratory participated in interlaboratory studies for the analysis of standards and sediment samples. The results showed recoveries between 75 and 95% and z-score values <2, demonstrating that the method is suitable for the analysis of SCCPs in soil/sediment samples. Graphical abstract Quantification of SCCPs by 2D-GC-μECD.

Magnetite nanoparticles surface-modified with a zinc(II)-carboxylate Schiff base ligand as a sorbent for solid-phase extraction of organochlorine pesticides from seawater

Magnetite nanoparticles were surface-modified with mercaptoacetic acid (MAA), complexed with Zn(II), and then treated with the dual Schiff base (referred to as imine-based ligand; IBL; obtained by reaction of p-aminobenzoic acid and 2,3-butanedione) to give particles with an architecture of type Fe3O4@MAA@IBL. These are shown to be viable sorbents for magnetic solid phase extraction of organochlorine pesticides (OCPs) from seawater samples. Efficient extraction of the OCPs probably is due to lone pair-π, π-complexation and π-interactions. The sorbent was characterized by transmission electron microscopy, scanning electron microscopy, FT-IR and energy-dispersive X-ray spectroscopy. The effects of the volumes of sample, sorbent dosage and eluent, adsorption and desorption times, and the salinity of the sample on the extraction efficiencies were optimized. The OCPs (heptachlor, aldrin, dieldrin, p,p’-DDE and p,p’-DDT) were quantified by gas chromatography with microelectron capture detection. Under optimal conditions, the limit of detections range was between 1.0 and 1.9 ng L−1. The enrichment factors are between 84.1 and 99.9 %. The sorbent was applied to the rapid extraction of trace quantities of OCPs from seawater samples and gave good relative recoveries (78 to 108 %) and relative standard deviations (<8.3 %).

Covalent Bonding of Metal-Organic Framework-5/Graphene Oxide Hybrid Composite to Stainless Steel Fiber for Solid-Phase Microextraction of Triazole Fungicides from Fruit and Vegetable Samples.

A hybrid material of the zinc-based metal-organic framework-5 and graphene oxide (metal-organic framework-5/graphene oxide) was prepared as a novel fiber coating material for solid-phase microextraction (SPME). The SPME fibers were fabricated by covalent bonding via chemical cross-linking between the coating material metal-organic framework-5/graphene oxide and stainless steel wire. The prepared fiber was used for the extraction of five triazole fungicides from fruit and vegetable samples. Gas chromatography coupled with microelectron capture detector (GC-μECD) was used for quantification. The developed method gave a low limit of detection (0.05-1.58 ng g(-1)) and good linearity (0.17-100 ng g(-1)) for the determination of the triazole fungicides in fruit and vegetable samples. The relative standard deviations (RSDs) for five replicate extractions of the triazole fungicides ranged from 3.7 to 8.9%. The method recoveries for spiked fungicides (5, 20, and 50 ng g(-1)) in grape, apple, cucumber, celery cabbage, pear, cabbage, and tomato samples were in the range of 85.6-105.8% with the RSDs ranging from 3.6 to 11.4%, respectively, depending on both the analytes and samples. The metal-organic framework-5/graphene oxide coated fiber was stable enough for 120 extraction cycles without a significant loss of extraction efficiency. The method was suitable for the determination of triazole fungicides 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.

Organochlorine pesticides in green sea turtles (Chelonia mydas) with and without fibropapillomatosis caught at three feeding areas off Brazil

Many factors threaten the survival of marine turtles, such as incidental capture by fisheries, habitat degradation, pollution and diseases. One of the most important diseases is fibropapillomatosis (FP), characterized by the development of benign skin tumours. FP predominantly affects juvenile green sea turtles (Chelonia mydas) and involves a complex multifactorial aetiology. For several years, it has been noted that the prevalence of FP tends to be higher in marine environments under the influence of human activities, leading to the hypothesis that environmental pollutants play a role in the epidemiology of this disease. Organochlorine compounds (OCs) are persistent organic pollutants with immunosuppressive and carcinogenic effects in humans and wildlife. OC levels (α-BHC, β-BHC, α-endosulphan, β-endosulphan, endosulphan sulphate, pp′-DDD, op′-DDD, pp′-DDE, op′-DDE, heptachlor, dicofol and mirex) were quantified through gas chromatography with a micro-electron capture detector (GC-μECD) in liver and fat samples from 64 juvenile green sea turtles. Specimens with and without FP were analysed, after being caught at three feeding areas off the Brazilian coast: Ubatuba, Praia Grande and Vitória. OC levels were comparable to those observed in similar studies, and no consistent difference was observed between sea turtles with and without FP. This study helps to elucidate the contamination profile in sea turtles caught at feeding areas off Brazil and confirms that green sea turtles are exposed to OCs, which may play a negative role in the health of this species.