Xueke Liu

Effervescence assisted on-site liquid phase microextraction for the determination of five triazine herbicides in water.

A novel effervescence assisted on-site liquid phase microextraction has been developed for the determination of five triazine herbicides in water. The use of an effervescent tablet composed of citric acid, sodium bicarbonate and 1-undecanol (extraction solvent) was the core of the method. The triazine herbicides in water were extracted by 1-undecanol released from tablet under effervescence and determined by ultra-high pressure liquid chromatography tandem mass spectrometer. The experimental variables, including NaCl concentration, temperature, weight of effervescent tablet, volume of extraction solvent and pH value, were screened by a Plackett-Burman design and optimized by a Box-Behnken design. Under the optimized conditions, good linearity was obtained in the range of 0.05-10 μg L(-1) with correlation coefficients ranging from 0.9936 to 0.9988. The limits of quantification were between 7.6 and 26.4 ng L(-1), and the recoveries were in 71.4-93.2% with relative standard deviations of 2.5-10.9%. This method, which does not require centrifugation and any special apparatus, was successfully applied to determine triazine herbicides in real waters, promising to be a way to speed field sampling procedures for the organic pollutants monitoring in water.

Effervescence assisted dispersive liquid-liquid microextraction based on cohesive floating organic drop for the determination of herbicides and fungicides in water and grape juice

A novel effervescence assisted dispersive liquid-liquid microextraction method based on cohesive floating organic drop has been developed for simultaneous determination of triazine herbicides and triazole fungicides in aqueous samples followed by ultra-high pressure liquid chromatography tandem a triple quadrupole mass spectrometer. In this method, 1-undecanol as extractant was well dispersed by effervescence. In order to obtain relatively high extraction efficiency, the effects of salt, volume of effervescence mixture, volume of extraction solvent and temperature were investigated. Under the optimum conditions, the proposed method showed good linearity within the range of 0.05-10μgL-1 with correlation coefficients of 0.9987-0.9999. The recoveries of analytes were in the range of 72.4-101.5% with relative standard deviations ranging from 2.6% to 11.7%. The limits of detection were varied from 2.7 to 9.7ngL-1. This method has been successfully used to simultaneously analyze triazine herbicides and triazole fungicides in surface waters and grape juice.

Approach for Pesticide Residue Analysis for Metabolite Prothioconazole-desthio in Animal Origin Food

Food safety problems such as damage to immune, nervous, and endocrine systems leading to cancer and malformations have received increasing attention. To achieve the maximum residue limits, the most discussed method of high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) is widely used with a advantage of high precision and resolution. Prothioconazole is a broad-spectrum thiocarbamate fungicide. It can rapidly metabolize to prothioconazole-desthio in different matrixes. Rapid and effective methods for the determination of prothioconazole-desthio in five kinds of different animal food were developed. Samples were extracted with acetonitrile or acetonitrile/water and determined by HPLC-MS/MS. The limit of detection and limit of quantification values of prothioconazole-desthio were 0.015 and 0.05 mg/kg for porcine liver and kidney, 0.0015 and 0.005 mg/kg for pork, and 0.003 and 0.01 mg/kg for eggs, together with 0.0012 and 0.004 mg/kg for milk of the detected method, respectively. A good linear regression trend can be observed in a certain concentration range for all of the animal food. At fortified levels, recoveries were between 83.6 and 105%, with relative standard deviations of 1.5-10.3%. A sample survey of 150 samples with 30 samples for each kind of animal food across the country was conducted and found that there was no prothioconazole-desthio detected in all samples.

Stereoselective metabolism of the UV-filter 2-ethylhexyl 4-dimethylaminobenzoate and its metabolites in rabbits in vivo and vitro

The stereoselective metabolism of the enantiomers of the UV-filter 2-ethylhexyl 4-dimethylaminobenzoate (EDP) in rabbits was studied. The two major metabolites 4-(N,N-dimethylamino) benzoic acid (DMP) and 4-methylaminobenzoic acid (MMP) were also investigated in vivo and in vitro. Cytotoxicity of EDP and its two metabolites was also investigated in hepatocytes. The results showed that EDP degraded rapidly to its metabolites (DMP and MMP) and could not be detected in blood at 5 min after intravenous administration to rabbit in vivo. In almost all the tissue samples, EDP, DMP and MMP could not be detected at 3 h expect DMP was found in the liver and kidney at about 1 mg kg−1 level. EDP was found to be degraded to DMP rapidly in plasma and liver microsome in vitro with t1/2 less than 20 and 5 min and the whole process was enantioselective with preference of (+)-form. DMP was observed to be further degraded to MMP in liver microsome in the presence of NADPH. The cytotoxic effects of EDP, DMP and MMP were carried out using buffalo rat liver cell line. The results from cell viability assays indicated that the degradation of EDP was a detoxification process.

Minimizing geometric isomerization of α-cypermethrin in the residue analysis.

Isomerization of chiral pesticides in residue analysis has not drawn much attention which can cause wrong decisions on the enantioselective environmental behavior. A residue analysis method for α-cypermethrin and its three acid metabolites, cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethyl cyclopropanecarboxylic acid (cis/trans-DCVA) and 3-phenoxybenzoic acid (3-PBA), in foods such as chicken, honey, milk and pork has been established, in which the isomerization of α-cypermethrin was minimized. The target compounds were determined by GC-ECD after a derivatization reaction with 1,1,1,3,3,3-hexafluoroisopropanol. The conditions of the method were optimized by Taguchi orthogonal experiment. Under the optimized conditions, good linearity was obtained with correlation coefficients ranging from 0.9964 to 0.9998. The limits of detection were 0.001-0.005 mg kg(-1). The recoveries were 70.9-114.9% with relative standard deviations of 0.6-15%. In addition, ratios of isomerization ranged only from 2.3% to 7.0%. This method was applied in commercial animal food products.

Enantioselective Characteristics and Montmorillonite-Mediated Removal Effects of α-Hexachlorocyclohexane in Laying Hens

α-Hexachlorocyclohexane (α-HCH) is a chiral organochlorine pesticide that is often ubiquitously detected in various environmental matrices and may be absorbed by the human body via food consumption, with serious detriments to human health. In this study, enantioselective degradation kinetics and residues of α-HCH in laying hens were investigated after a single dose of exposure to the pesticide, whereas enantioselectivity and residues of α-HCH in eggs, droppings, and various tissues were investigated after long-term exposure. Meanwhile, montmorillonite (MMT), a feed additive with high capacity of adsorption, was investigated for its ability to remove α-HCH from laying hens. Most non-brain tissues enantioselectively accumulated (-)-α-HCH, while (+)-α-HCH was preferentially accumulated in the brain. The enantiomer fractions (EFs) in most tissues gradually decreased, implying continuous depletion of (+)-α-HCH in laying hens. After 30 days of exposure and 31 days of elimination, the concentration of α-HCH in eggs and tissues of laying hens with MMT-containing feed was lower than that with MMT-free feed, indicating the removal effects of MMT for α-HCH in laying hens. The findings presented herein suggest that modified MMT may potentially be useful in reducing the enrichment of α-HCH in laying hens and eggs, thus lowering the risk of human intake of α-HCH.

Supramolecular fluorescent sensor array for simultaneous qualitative and quantitative analysis of quaternary ammonium herbicides

The quaternary ammonium herbicides mainly include paraquat and diquat, whose fast and simultaneous detection is important for environmental and public safety. Herein, we simultaneously analyzed paraquat and diquat by a simple three-component supramolecular sensor array, which was simply prepared from carboxymethyl-β-cyclodextrin (CM-β-CD) and fluorophores. Under the optimal pH, the two herbicides were excellently distinguished in the principal component analysis (PCA) score plot in the presence of various interferences. Then, the results of semi-quantitative analysis through linear discrimination analysis (LDA) also showed good cluster separation for both paraquat and diquat in the concentration range of 10–250 μM. Moreover, in order to test the unknown samples, the support vector machine (SVM) regression model was applied for simultaneous quantitative analysis of paraquat and diquat, which was successful in the prediction of the amount of the two analytes. Accordingly, this simple supramolecular sensor array is expected to be applied in the rapid and accurate analysis of quaternary ammonium herbicides.

Application of a magnetic graphene nanocomposite for organophosphorus pesticide extraction in environmental water samples

A novel magnetic nanocomposite was prepared and applied for the extraction of organophosphorus pesticide residue (malathion, chlorpyrifos, isocarbophos, fenamiphos, profenofos) in environmental water by magnetic solid phase extraction. The magnetic nanocomposite was synthesized by coating Fe3O4 with silicon dioxide and then bonding with graphene oxide under the catalytic action of hydrazine hydrate. A residue analysis method for the determination of organophosphorus pesticides in environmental water was established via magnetic solid phase extraction with the nanocomposite as the sorbent, followed by gas chromatography with flame photometric detection (GC-FPD). Various experimental parameters affect extraction efficiency and must be optimized, such as the sorbent amount, the type and volume of desorption solvent, desorption time, desorption step, salt concentration and pH. Under the optimum conditions, a linear response was achieved for malathion and chlorpyrifos in the concentration range of 0.05 mg L-1-5 mg L-1. Other organophosphorus pesticides were quantified in a concentration range of 0.1 mg L-1-5 mg L-1, and the coefficient of correlations were between 0.996 and 1 for this method. The method was used to determine organophosphorus pesticides in river water and groundwater. The average recoveries ranged from 90.2% to 102.9%, with low relative standard deviations (RSD), and the limits of detection (LOD) were between 0.016 mg L-1 to 0.033 mg L-1 at a signal to noise ratio of 3. The method was efficient for the residue analysis of organophosphorus pesticides in water with easy operation, high sensitivity, and good precision.

Ultrafast removal of Cd(II) by green cyclodextrin metal-organic framework based nanoporous carbon: adsorption mechanism and application

Water contaminated with heavy metals has been identified as a significant threat to human health. Therefore, the development of safe and rapid water-treatment techniques is necessary. We have synthesized an eco-friendly γ-cyclodextrin metal-organic framework (MOF)-based nanoporous carbon (γ-CD MOF-NPC) material, conducted a comprehensive characterization of it, and found its rapid and effective CdII -removal capacity. The γ-CD MOF-NPC could effectively sequester a majority of cadmium ions within one minute, and it still demonstrated excellent adsorption ability under various conditions, including different pH, adsorbent dosage, and coexistent ions. The maximum adsorption capacity was calculated to be 140.85 mg g-1 by means of the Langmuir model. The adsorption was primarily due to the effect of ion exchange of oxygen-containing functional groups, as determined by studying the ζ potential and Fourier transform infrared spectroscopy. Flow-through experiments further proved the rapid CdII -removal capacity and potential of the practical application of γ-CD MOF-NPC in water treatment according to the cytotoxic data.

Absorption, Distribution, Metabolism, and in Vitro Digestion of Beta-Cypermethrin in Laying Hens

Beta-cypermethrin (beta-CP), an important pyrethroid insecticide, and its main acid metabolites are frequently detected in human samples. Because beta-CP may pose some risk to human health, we studied dynamics and residues of beta-CP and its metabolites in hen egg, droppings, blood, and 15 other tissues after continuous exposure. A digestive model was then used to study beta-CPs digestive fate. Beta-CP and its metabolites significantly accumulated in tissues with high lipid contents and were readily transferred to eggs. Beta-CP was mainly metabolized into acid metabolites that accumulated in egg and edible tissues of laying hens, suggesting that humans may be exposed to beta-CP acid metabolites through food.