Application and enantioselective residue determination of chiral pesticide penconazole in grape, tea, aquatic vegetables and soil by ultra performance liquid chromatography-tandem mass spectrometry

Stereoselective study on chiral fungicide metconazole in four kinds of fruits: Absolute configuration, SFC-MS/MS enantioseparation, degradation and risk assessment

Metconazole is a novel chiral fungicide with two chiral carbon atoms, but the research on its stereoselective behavior is limited. Therefore, the stereoselective behaviors of metconazole in four fruits, including grape, peach, pear and jujube, were summarized in this study. After determining the absolute configuration of metconazole stereoisomers, a chiral separation method through supercritical fluid chromatography/tandem triple quadrupole mass spectrometry was first developed, which combined an improved QuEChERS method obtained the recoveries of 71.6-113 % with RSD ≤ 19.8 %. The LOD and LOQ were 4.30-95.9 and 10.5-143.2 ng/kg, respectively. Different stereoselective and diastereoselective behaviors were observed in four fruits. Dietary risk assessments of rac-metconazole were performed in populations with different ages and genders. Both acute (RQa, 0.0124-0.140 %) and chronic (HQ, 0.0234-0.0794 %) intake risks were acceptable. The results of this study would contribute to more complete risk assessments of metconazole and provide data for chiral studies.

Antifungal triazoles affect key non-target metabolic pathways in Solanum lycopersicum L. plants

Several 1,2,4-triazoles are widely used as systemic fungicides in agriculture because they inhibit fungal 14ɑ-demethylase. However, they can also act on many non-target plant enzymes, thereby affecting phytohormonal balance, free amino acid content, and adaptation to stress. In this study, tomato plants (Solanum lycopersicum L. var. 'Cherrola') were exposed to penconazole, tebuconazole, or their combination, either by foliar spraying or soil drenching, every week, as an ecotoxicological model. All triazole-exposed plants showed a higher content (1.7-8.8 ×) of total free amino acids than the control, especially free glutamine and asparagine were increased most likely in relation to the increase in active cytokinin metabolites 15 days after the first application. Conversely, the Trp content decreased in comparison with control (0.2-0.7 ×), suggesting depletion by auxin biosynthesis. Both triazole application methods slightly affected the antioxidant system (antioxidant enzyme activity, antioxidant capacity, and phenolic content) in tomato leaves. These results indicated that the tomato plants adapted to triazoles over time. Therefore, increasing the abscisic and chlorogenic acid content in triazole-exposed plants may promote resistance to abiotic stress.

Simultaneous determination of spiropidion and its five major metabolites in sweet orange fruit and various processing by-products using ultra-high performance liquid chromatography-tandem mass spectrometry

The present work reported the application of an ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for simultaneous analysis of spiropidion and its five major metabolites in sweet orange fruit and by-products throughout the whole industrial juicing process of the orange fruit. The reversed-dispersive solid phase extraction (r-DSPE) with multi-walled carbon nanotubes (MWCNTs) was employed for the extraction and purification. The established method was validated and satisfactory parameters (linearity, trueness, precision, sensitivity, matrix effect and stability) were obtained. And then, the field trial of spiropidion on sweet oranges has been conducted and the effect of commercial juicing processing on the residue of spiropidion and its metabolites was further investigated. The various processing factors (PFs) for washing, juicing, sterilization, concentrating and essential oil collecting were also determined. The final results indicated that washing processing reduced residues by 18.4%; the juicing step allowed a significant decrease of the spiropidion residue by 34.2-70.8%, with PFs value in the range of 0.290-0.658. However, high level of residual spiropidion (ranging from 4.016 to 4.205 mg/kg) was detected in orange essential oil, with PFs value of 17.157. All the above results demonstrated the efficiency of the established method in the routine control analysis of spiropidion residues in sweet orange fruits and their by-products, and will facilitate the further intensive research on its spatial distribution, transfer and degradation during the different processing procedures of the sweet orange fruits.

Protective effects of N-acetyl-l-cysteine against penconazole-triggered hepatorenal toxicity in adult rats

Introduction

Penconazole (PEN) is a widely applied triazole fungicide. This study sought to define the efficacy of N-acetyl-l-cysteine (NAC) in mitigating PEN-triggered hepatorenal toxicity in rats.

Material and Methods

Twenty-eight adult male albino Wistar rats were assigned to four groups: a normal control (NC), a PEN group, a NAC group and a PEN+NAC group. Administration of PEN (50 mg/kg body weight (b.w.) every 2 days) and NAC (150 mg/kg b.w., daily) took place via oral gavage for 10 days.

Results

Effective amelioration by NAC of PEN-induced liver and kidney dysfunction was indicated by a significant reduction in the circulating liver and kidney markers (aspartate aminotransferase, alanine aminotransferase, urea and creatinine). Attenuation of PEN-induced oxidative stress and lipid peroxidation in liver and kidney tissues was evident in a significant reduction in malondialdehyde and enhanced total antioxidant capacity. Moreover, NAC significantly reduced the histopathological alterations and the expression of tumour necrosis factor α in liver and kidney tissue. Furthermore, NAC maintained the messenger RNA levels of nuclear factor erythroid 2-related factor 2 (Nrf2), haem oxygenase 1, and Kelch-like erythroid cell-derived protein 1 and prevented nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) protein upregulation caused by PEN.

Conclusion

N-acetyl-1-cysteine protected against PEN-induced hepatorenal oxidative damage and inflammatory response via activation of Nrf2 and inhibition of NF-κB pathways.

Triazoles as a Potential Threat to the Nutritional Quality of Tomato Fruits

Triazole fungicides can threaten plants as abiotic stressors but can also positively affect plant defense by inducing priming. Thus, plant yield is also both protected and endangered by triazoles that may influence several metabolic pathways during maturation processes, such as the biosynthesis of saccharides or secondary metabolites. Here, Solanum lycopersicum L. plants were exposed to foliar and soil applications of penconazole, tebuconazole, or their combination, and their resulting effect on tomato fruits was followed. The exposure to the equimolar mixture of both triazoles influenced the representation of free proteinogenic amino acids, especially Gln, Glu, Gly, Ile, Lys, Ser and Pro, saccharide content, and led to a significant increase in the contents of total phenolics and flavonoids as well as positive stimulation of the non-enzymatic antioxidant system. Among the identified secondary metabolites, the most abundant was naringenin, followed by chlorogenic acid in tomato peel. In turn, all triazole-treated groups showed a significantly lower content of rosmarinic acid in comparison with the control. Foliar application of penconazole affected the fruit more than other single triazole applications, showing a significant decrease in antioxidant capacity, the total content of secondary metabolites, and the activities of total membrane-bound peroxidases and ascorbate peroxidase.

Resveratrol ameliorates penconazole-induced cardiotoxicity by inhibition of oxidative stress and apoptosis in zebrafish larvae

Penconazole (PEN) is a typical systemic triazole fungicide with cardiac toxic effects. Resveratrol (RES) is a natural polyphenolic phytochemical with antioxidation properties. This study aimed to investigate if RES could protect against PEN-induced cardiotoxicity and to determine the underlying mechanisms. Zebrafish embryos were exposed to 0, 0.5, 1 and 2 mg/L of PEN from 4 to 96 h post fertilization (hpf) and cardiac developmental toxicity was assessed. Our results showed that PEN decreased hatching rate, survival rate, heart rate and body length, with increased malformation rate and spontaneous movement. PEN induced pericardial edema and abnormal cardiac structure in myl7:egfp transgenic zebrafish, as well as downregulation of cardiac development related genes (nkx2.5, tbx2.5, gata4, noto, and vmhc). In addition, PEN elevated oxidative stress via reactive oxygen species (ROS) accumulation and triggered cardiomyocytic apoptosis by upregulation of p53, bcl-2, bax and caspase 3. These adverse outcomes were counteracted by RES, indicating that RES ameliorated PEN-induced cardiotoxicity by inhibiting oxidative stress and apoptosis in zebrafish. Taken together, this study revealed the important role of oxidative stress in PEN-induced cardiotoxicity and identified dietary RES supplementation as a novel strategy to mitigate its toxicity.

Dissipation of penconazole formulation in horticultural crops by ultrahigh performance liquid chromatography-high resolution mass spectrometry: From the active substance to metabolites

The present study describes the dissipation and metabolism of penconazole in horticultural products by a method based on ultra-high performance liquid chromatography-quadrupole-orbitrap (UHPLC-Q-Orbitrap). Targeted and suspected analysis were carried out. Two independent trials were performed under laboratory conditions (on courgette samples), and under greenhouse conditions (on tomatoes) during 43 and 55 days, respectively. In both studies, a pesticide formulation (TOPAS® EW) containing penconazole was used. The results showed that penconazole was relatively short-lived (<30 days) in horticultural products. The proposed method allowed for the tentative identification and semi-quantification of nine metabolites. In addition, the potential toxicity of these metabolites was evaluated, observing that some of them are even more toxic than penconazole, as triazole lactic acid. This research may provide a starting point for understanding the dissipation process of penconazole, the formation pathways of its main metabolites, their concentrations and toxicity to ensure food safety and the environmental protection.

Highly sensitive colorimetric assay for penconazole using gold nanostar-graphene quantum dot composite

In this study, a simple and sensitive colorimetric method for penconazole sensing is reported. It is based on the etching/anti-etching strategy in which gold nanostar@graphene quantum dot (AuNS@GQD) nanocomposite acts as a sensing nanoprobe and IO₄^- as an etching agent. With adding IO₄^- to the solution of AuNSs@GQDs, the sharp tips of NSs are etched and they are transformed into nearly spherical nanostructures, and the color of the solution changes from green to violet. These changes can be attributed to the oxidation of gold atoms at the sharp corners and tips of NSs with I₂, produced by the reaction of IO₄^- with AuNS@GQD solution. When penconazole is added into the system, the color and shape variations of AuNSs caused by periodate are impressively prevented. It can be assigned to the strong binding affinity between nitrogen atoms of penconazole and gold atoms, which protects them from etching by I₂. This mechanism has been affirmed via transmission electron microscopy (TEM) and UV-Vis spectra. This approach exhibited a good linear relationship (R² = 0.999) between the wavelength shift and penconazole concentration in the range of 5.0-1000.0 nM with a limit of detection (LOD) of 1.5 nM. The sensor is stable and reproducible and was used to measure penconazole in spiked water samples with recoveries over 97%.

Enantioselective toxic effects of the novel chiral antifungal agrochemical penthiopyrad in the early life stage of zebrafish (Danio rerio)

Penthiopyrad was extensively applied in agricultural production, however, the toxicities information of the penthiopyrad enantiomers on early life stages of aquatic organism were limited. This study investigated the enantioselective toxicity of penthiopyrad on the early life stage of zebrafish by acute toxicity, sublethal toxic effects and the mRNA relative expression levels of genes related to succinate dehydrogenase, cardiac development, and lipid metabolism. The results showed that the 96-h-LC₅₀ of penthiopyrad racemate and enantiomers to zebrafish embryos were Rac-: 2.784 mg/L; R-(-)-: 3.528 mg/L; S-(+)-: 1.882 mg/L. Penthiopyrad exposure induced autonomous movement abnormalities, slowed heart rate and delayed hatching in zebrafish embryos, and caused developmental toxic effects such as pericardial edema and yolk sac edema. The mRNA relative expression levels results showed that penthiopyrad exposure induced significant enantioselectivity effect for the expression of the Sdha, Pr1 and Nkx2.5 with a 1.94-4.98-fold difference between different enantiomers, and significantly affected succinate dehydrogenase (energy metabolism), lipid metabolism and cardiac development-related genes expression. In general, S-(+)-penthiopyrad induced higher toxic effects in zebrafish embryos, and mitochondrial dysfunction may be an important cause of abnormal development. This study contributed to improve the comprehensive risk assessment and enantiomeric research system of penthiopyrad to early life stage of zebrafish.

Syntheses of APTMS-Coated ZnO: An Investigation towards Penconazole Detection

Extrinsic chemiluminescence can be an efficient tool for determining pesticides and fungicides, which do not possess any intrinsic fluorescent signal. On this basis, (3-aminopropyl) trimethoxysilane (APTMS)-coated ZnO (APTMS@ZnO) was synthesized and tested as an extrinsic probe for the fungicide penconazole. Several synthetic routes were probed using either a one-pot or two-steps method, in order to ensure both a green synthetic pathway and a good signal variation for the penconazole concentration. The synthesized samples were characterized using X-ray diffraction (XRD), infrared (IR), Raman and ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM) imaging and associated energy-dispersive X-ray (EDX) analysis. The average size of the synthesized ZnO nanoparticles (NPs) is 54 ± 10 nm, in line with previous preparations. Of all the samples, those synthesized in two steps, at temperatures ranging from room temperature (RT) to a maximum of 40 °C, using water solvent (G-APTMG@ZnO), appeared to be composed of nanoparticles, homogeneously coated with APTMS. Chemiluminescence tests of G-APTMG@ZnO, in the penconazole concentration range 0.7-1.7 ppm resulted in a quenching of the native signal between 6% and 19% with a good linear response, thus indicating a green pathway for detecting the contaminant. The estimated detection limit (LOD) is 0.1 ± 0.01 ppm.

Systematic evaluation of chiral pesticides at the enantiomeric level: A new strategy for the development of highly effective and less harmful pesticides

Over the past few decades, pesticides have been used in large quantities, and they pose potential risks to organisms across various environments. Reducing the use of pesticides and their environmental risks has been an active research focus and difficult issue worldwide. As a class of pesticides with special structures, chiral pesticides generally exhibit enantioselectivity differences in biological activity, ecotoxicity, and environmental behavior. At present, replacing the racemates of chiral pesticides by identifying and developing their individual enantiomers with high efficiency and environmentally friendly characteristics is an effective strategy to reduce the use of pesticides and their environmental risks. In this study, we review the stereoselective behaviors of chiral pesticide, including their environmental behavior, stereoselective biological activity, and ecotoxicity. In addition, we emphasize that the systematic evaluation of chiral pesticides at the enantiomeric level is a promising novel strategy for developing highly effective and less harmful pesticides, which will provide important data support and an empirical basis for reducing pesticide application.

Residue degradation, transfer and risk assessment of pyriproxyfen and its metabolites from tea garden to cup by ultra performance liquid chromatography tandem mass spectrometry

BACKGROUND

Tea is one of the most popular drinks in the world. The growth of tea plant is inseparable from the control of pesticides on diseases and pests. Pyriproxyfen is used as a pesticide substitute to control insect pests in tea gardens, but little is known about its residue degradation. Here, we performed an integrative study of the degradation and metabolism of pyriproxyfen from the tea garden to the cup.

RESULTS

The dissipation half-life of pyriproxyfen during tea growth was 2.74 days, and five metabolites PYPAC, PYPA, DPH-Pyr, 5''-OH-Pyr, and 4'-OH-Pyr were generated. The total processing factors for pyriproxyfen in green tea and black tea were 2.41-2.83 and 2.77-3.70, respectively. The residues of pyriproxyfen and its metabolites were affected by different processing steps. The total leaching rates of pyriproxyfen from green tea and black tea into their infusions were 9.8-12.3% and 5.3-13.8%, respectively. The leaching rates of the five metabolites were higher than that of pyriproxyfen and increased the intake risk.

CONCLUSION

To ensure safe consumption, the recommended maximum residue limit value of pyriproxyfen in tea can be set to 5 mg kg^-1 and the pre-harvest interval can be set to 5 days. © 2022 Society of Chemical Industry.

Assessment of the eco-toxicological effects in zoxamide polluted soil amended with fertilizers-An indoor evaluation

Zoxamide is a benzamide fungicide applied to control diseases caused by oomycete fungi. Fertilizers are important agricultural supplies to adjust soil properties and increase nutrition. To investigate the impact of zoxamide and seven fertilizers urea, phosphate fertilizer, potash fertilizer, compound fertilizer, organic fertilizer, vermicompost and soya bean cakes on the soil environment, the enantioselective dissipation characteristics of zoxamide, soil enzyme activities, pH and N, P nutrition changes were comprehensively analyzed in our present study. The enantioseparation method was successfully validated to quantify the zoxamide enantiomers in soil by HPLC using Chiral NQ (2)-RH column. Our results demonstrated that the R-(-)- and S-(+)-zoxamide half dissipated in the range of 10.88-17.81 and 8.05-14.41 days, respectively. S-(+)-zoxamide disappeared faster in soil. The vermicompost accelerated the dissipation rate of S-(+)-zoxamide, while urea, phosphate, organic and vermicompost fertilizer increased the dissipation selectivity. Zoxamide and fertilizers other than urea caused soil acidification during 80 days. Zoxamide was beneficial to soil catalase, instead inhibited soil urease, dehydrogenase activities and available phosphorus content. No significant effects on sucrase activity and available nitrogen content were found by zoxamide. Vermicompost and soya bean cakes had lasting and outstanding performance in efficiently improving soil enzyme activity and N, P nutrition. The comprehensive understanding of the ecological impact induced by chiral pesticide enantiomers and fertilizers on soil is vital to ensure the sustainable development and safety of agricultural production.

Particularities of Fungicides and Factors Affecting Their Fate and Removal Efficacy: A Review

Systemic fungicide use has increased over the last decades, despite the susceptibility of resistance development and the side effects to human health and the environment. Although herbicides and insecticides are detected more frequently in environmental samples, there are many fungicides that have the ability to enter water bodies due to their physicochemical properties and their increasing use. Key factors affecting fungicide fate in the environment have been discussed, including the non-target effects of fungicides. For instance, fungicides are associated with the steep decline in bumblebee populations. Secondary actions of certain fungicides on plants have also been reported recently. In addition, the use of alternative eco-friendly disease management approaches has been described. Constructed Wetlands (CWs) comprise an environmentally friendly, low cost, and efficient fungicide remediation technique. Fungicide removal within CWs is dependent on plant uptake and metabolism, absorption in porous media and soil, hydrolysis, photodegradation, and biodegradation. Factors related to the efficacy of CWs on the removal of fungicides, such as the type of CW, plant species, and the physicochemical parameters of fungicides, are also discussed in this paper. There are low-environmental-risk fungicides, phytohormones and other compounds, which could improve the removal performance of CW vegetation. In addition, specific parameters such as the multiple modes of action of fungicides, side effects on substrate microbial communities and endophytes, and plant physiological response were also studied. Prospects and challenges for future research are suggested under the prism of reducing the risk related to fungicides and enhancing CW performance.

Enantioselective separation, analysis and stereoselective dissipation of the chiral pesticide cloquintocet-mexyl using a modified QuEChERS method by high-performance liquid chromatography tandem mass spectrometry

An efficient and novel enantioseparation method was successfully developed and validated to quantify the enantiomers of cloquintocet-mexyl in soil, millet, enoki mushroom, oilseed rape, and watermelon using a modified QuEChERS technique combined with HPLC-MS/MS. This method showed reliable performances for determining both enantiomers of cloquintocet-mexyl in all five matrices. The limits of detection and limits of quantification were in the range of 0.06-0.15 μg kg^-1 and 0.2-0.5 μg kg^-1, respectively. Good linearities were obtained with correlation coefficients ≥0.9954. The mean recoveries were between 84.1% and 111.5%, with relative standard deviations ranging from 1.2% to 9.8% at three spiked levels. Additionally, the study of stereoselective dissipation of cloquintocet-mexyl in soil indicated that (R)-cloquintocet-mexyl was preferentially degraded. This work is the first to describe a chiral analytical method and enantioselective behavior of cloquintocet-mexyl and provide basic data for the risk evaluation of cloquintocet-mexyl in food and environmental safety.

Chiral fungicide penconazole: Absolute configuration, bioactivity, toxicity, and stereoselective degradation in apples

Traditional evaluation of chiral pesticides can lead to inaccurate results, as their enantiomers may show different properties. Penconazole, a chiral triazole fungicide with two enantiomers, is widely applied to protect against phytopathogens. In this study, its absolute configuration, bioactivity, ecotoxicity, and stereoselective degradation were investigated at the enantiomeric level in detail. The absolute configuration of the two enantiomers (R-(+)-penconazole and S-(-)-penconazole) was first confirmed by electronic circular dichroism (ECD), and their enantioseparation method was developed and optimized using UPLC-MS/MS. S-(-)-penconazole showed high bioactivity, as its fungicidal activity against four target phytopathogens (Alternaria alternate f. sp. mali, Botryosphaeria berengeriana f. sp. piricola, Colletotrichum gloeosporioides, and Fusarium oxysporum) was 1.8-4.4 times higher than that of R-(+)-penconazole. The results of an acute toxicity test showed that the LC₅₀ values of S-(-)-penconazole against Daphnia magna were 32.5 times higher than those of R-(+)-penconazole at 24 h during the test period. Stereoselective degradation behaviors were found in nonbagging and bagging Fuji apples collected from three major apple-producing regions in China, with half-lives of 23.5-51.6 d (nonbagging treatment) and 23.0-57.5 d (bagging treatment) for R-(+)-penconazole and 41.1-60.9 d (nonbagging treatment) and 52.5-91.2 d (bagging treatment) for S-(+)-penconazole, respectively. This study provided new insights into the bioactivity, ecotoxicity, and stereoselective degradation of penconazole enantiomers. The above results also emphasized the importance of risk assessments of chiral pesticides at the enantiomeric level.

Stereoselective effects of fungicide difenoconazole and its four stereoisomers on gut barrier, microbiota, and glucolipid metabolism in male mice

Difenoconazole is a commonly used triazole fungicide that consists of four stereoisomers [(2S,4S)-, (2S,4R)-, (2R,4R)-, and (2R,4S)-isomers] with different bioactivity. For example, the toxicity of the (2R,4S)-isomer to fish is approximately seven times higher than that of the (2S,4S)-isomer. However, the stereoselective toxic effects of difenoconazole stereoisomers on mammals have received little attention. In the present study, adult male mice were orally treated with a mixture of the four stereoisomers or each stereoisomer individually (0, 30, or 100 mg/kg/d) by gavage for 28 days. Pathological staining of the liver sections showed that the (2R,4R)-isomer caused lipid droplet accumulation. The mixture or each individual stereoisomers decreased the levels of amino acids and acyl-carnitine in serum. Moreover, the (2S,4R)-, (2R,4R)-, and (2R,4S)-isomers affected intestinal permeability, causing decreases in mucus secretion and tight junction protein expression in colon. Analysis of the gut microbiota composition showed that the stereoisomers caused decreases of OTU numbers and observed species at different levels. Interestingly, difenoconazole and its four stereoisomers reduced the relative abundance of Bacteroidetes at the phylum level and some short-chain fatty acid (SCFA)-producing bacteria. Taking the findings together, 2R-difenoconazole with strong bioactivity against pathogenic fungi also had significant effects in mammals, disrupting hepatic lipid metabolism, intestinal permeability, and gut microbiota. It is concluded that the health risks of the four difenoconazole stereoisomers to mammals should not be overlooked.

Enantioselective monitoring chiral fungicide mefentrifluconazole in tomato, cucumber, pepper and its pickled products by supercritical fluid chromatography tandem mass spectrometry

A fast, effective, and environmental-friendly method was developed for enantioseparation and analysis of mefentrifluconazole in vegetables based on supercritical fluid chromatography tandem mass spectrometry. The enantioselective behaviors of mefentrifluconazole enantiomers in tomato, cucumber, and pepper in the greenhouse, and pickled cucumber and pepper during processing were investigated. Mefentrifluconazole enantiomers could obtain baseline separation within 2 min. The average recoveries of all matrices ranged from 78.4% to 119.0%, with relative standard deviations less than 16.8% for two enantiomers. S-(+)-mefentrifluconazole was preferentially degraded in pepper, while there was no enantioselectivity in tomato and cucumber under field conditions. During processing, S-(+)-mefentrifluconazole was reduced preferentially than R-(-)-mefentrifluconazole in pickled cucumber and cucumber brine. Inversely, R-(-)-mefentrifluconazole degraded faster than S-(+)-mefentrifluconazole in pepper brine. But, no obvious enantioselectivity was observed in pickled pepper. The result of this study could contribute to a more accurate dietary risk assessment of mefentrifluconazole in vegetables and processed products.

Ultrasound-assisted dispersive liquid-phase microextraction by solidifying L-menthol-decanoic acid hydrophobic deep eutectic solvents for detection of five fungicides in fruit juices and tea drinks

An ecofriendly and efficient ultrasound-assisted deep eutectic solvents dispersive liquid-phase microextraction by solidifying the deep eutectic solvents-rich phase was developed to determine azoxystrobin, fludioxonil, epoxiconazole, cyprodinil, and prochloraz in fruit juices and tea drinks by high-performance liquid chromatography. A varieties of environmental hydrophobic deep eutectic solvents serving as extraction agents were prepared using L-menthol and decanoic acid as hydrogen-bond acceptor and hydrogen-bond donor, respectively. The deep eutectic solvents were ultrasonically dispersed in sample solutions, solidified in a freezer and easily harvested. The main variables were optimized by one-factor-at-a-time and response surface test. The new method performs well with relative recovery of 71.75-109.40%, linear range of 2.5-5000 μg/L (r ≥ 0.9968), detection limit of 0.75-8.45 μg/L, quantification limit of 2.5-25 μg/L,_, and inter- and intraday relative standard deviations below 13.53 and 14.84%, respectively. As for the extraction mechanism, deep eutectic solvents were disposed into many fine particles in the solution and captured the analytes based on the changes of particle size and quantity in deep eutectic solvents droplets after extraction. The environmental method can successfully detect fungicide residues in real fruit juices and tea drinks.

Enantioselective determination of phenthoate enantiomers in plant-origin matrices using reversed-phase high-performance liquid chromatography-tandem mass spectrometry

Phenthoate is a chiral organophosphate pesticide with a pair of enantiomers which differ in toxicity, behavior and insecticidal activity, and its acute toxicity on human health owing to the inhibition of acetylcholinesterase highlights the need for enantioselective detection of enantiomers. Therefore, this study aimed to establish a simple rapid method for separation and detection of phenthoate enantiomers in fruits, vegetables and grains. The enantiomers were separated using reversed-phase high-performance liquid chromatography-tandem mass spectrometry for the first time. Rapid chiral separation (within 9 min) of the target compound was achieved on a chiral OJ-RH column with the mobile phase of methanol-water = 85:15(v/v), at a flow rate of 1 ml/min and a column temperature of 30°C. Acetonitrile and graphitized carbon black were used as the extractant and sorbent for pretreatment, respectively. This method provides excellent linearity (correlation coefficient ≥0.9986), high sensitivity (limit of quantification 5 μg/kg and limit of detection <0.25 μg/kg), satisfactory mean recoveries (76.2-91.0%) and relative standard deviation (intra-day RSDs ranged from 2.0 to 7.9% and inter-day RSDs ranged from 2.4 to 8.4%). In addition, a field trial to explore the stereoselective degradation of phenthoate enantiomers in citrus showed that (-)-phenthoate degraded faster than its antipode, resulting in the relative accumulation of (+)-phenthoate.

Bagging and non-bagging treatment on the dissipation and residue of four mixed application pesticides on banana fruit

BACKGROUND

Bananas are vulnerable to disease and insect pests after producing fruit. In order to increase the yield and produce high-quality fruit, the insecticides and fungicides are mixed and applied 2-3 times on banana, then the fruit is bagged. Buprofezin, imidacloprid, difenoconazole, and pyraclostrobin are widely used on banana. However, there is a lack of research on the effect of fruit bagging on pesticide dissipation and residues on bananas.

RESULTS

A versatile liquid chromatography-tandem mass spectrometry method with modified QuEChERS sample preparation has been developed for the determination of buprofezin, imidacloprid, difenoconazole, and pyraclostrobin in bananas. The recovery of four pesticides was satisfactory (74.96-98.63%) with reasonable relative standard deviation (≤ 8.78%). In Hainan and Guangzhou, the half-lives of the four pesticides were 4.68-13.9 and 5.63-20.4 days in non-bagged and bagged bananas, respectively. The significance analysis of the half-lives in the two sites showed that the dissipation rates of the three pesticides (imidacloprid, difenoconazole, pyraclostrobin) on whole bananas were significantly decreased by the effect of bagging (P < 0.05). However, there was no significant difference in the degradation of half-life of buprofezin under bagging and without bagging (P > 0.05).

CONCLUSION

The high vapor pressure and the non-systemic property cause buprofezin to evaporate and dissipate the fastest among the four studied pesticides. The ultimate residues of four pesticides in bananas are lower than the maximum residue limits in China after three times of mixed applications under bagging or non-bagging. The results provide scientific data for evaluating the safety of four pesticides in banana bagging. © 2020 Society of Chemical Industry.

A rapid method for the simultaneous stereoselective determination of the triazole fungicides in tobacco by supercritical fluid chromatography-tandem mass spectrometry combined with pass-through cleanup

This work presents a simple, rapid and green chiral analysis method for five triazole fungicides (penconazole, tebuconazole, triadimefon, myclobutanil, and triadimenol) in tobacco, by which the samples were cleaned up by the novel pass-through solid phase extraction and subsequently the stereoisomers were separated and determined by the supercritical fluid chromatography-tandem mass spectrometry (SFC-MS/MS). Optimized separation of the stereoisomers was achieved on an ACQUITY UPC2 Trefoil AMY 1 column within 6 min. Under fortified concentration levels of 0.1, 0.5 and 2.0 mg/kg, the mean recoveries were 82.8-106.6%, the intra-day relative standard deviations (RSDs) were 1.1-6.6%, and the inter-day RSDs were 2.5-5.6%. The correlation coefficient was greater than 0.9926 for all studied analytes within the range of 10-500 ng/mL. The limits of detection (LODs) for all stereoisomers ranged from 0.26 μg/kg to 3.24 μg/kg. The established method was subsequently successfully applied to analyze authentic samples, confirming that this method is a novel, rapid and environmentally friendly method for the stereoselective separation of triazole fungicides in tobacco.

Stereoselective degradation behavior of the novel chiral antifungal agrochemical penthiopyrad in soil

Penthiopyrad is a chiral carboxamide fungicide with a broad spectrum of fungicidal activity. However, there is no report on the analysis of the enantiomers of penthiopyrad and their environmental behavior. Soil is an important carrier for pesticides to affect the environment. Therefore, this study aimed to investigate the absolute configuration, stereoselective degradation, configuration stability and potential metabolites of this agrochemical in soil under different laboratory conditions. R-(-)-penthiopyrad and S-(+)-penthiopyrad were identified by the electronic circular dichroism method. Regarding the racemic analyte, the degradation half-lives of the stereoisomers ranged from 38.9 to 97.6 days, the S-(+)-stereoisomer degraded preferentially in four types of Chinese soil. However, enantiopure R-(-)-penthiopyrad degraded faster than its antipode, a finding that might be related to the microbial activity in soil. The organic matter (OM) content influenced the stereoselective degradation of rac-penthiopyrad. No configuration conversion was observed in both enantiopure analyte degradation processes. One possible metabolite, 753-A-OH, was detected in the treated soil samples, and the degradation pathway might be a hydroxylation reaction. This is the first report of the absolute configuration of penthiopyrad stereoisomers and the first comprehensive evaluation of the stereoselective degradation of penthiopyrad in Chinese soil. Stereoselective degradation of rac-penthiopyrad was observed in the four types of soil. And the stereoselectivity might be inhibited by OM. This study provides more accurate data to investigate the environmental behavior of penthiopyrad at the stereoisomer level.

New Trend in the Extraction of Pesticides from the Environmental and Food Samples Applying Microextraction Based Green Chemistry Scenario: A Review

This review focused on the green microextraction methods used for the extraction of pesticides from the environmental and food samples. Microextraction techniques have been explored and applied in various fields of analytical chemistry since its beginning, as evinced by the numerous reviews published. The success of any technique in science and technology is measured by the simplicity, environmentally friendly, and its applications; and the microextraction technique is highly successive. Deliberations were attentive to studies where efforts have been made to validate the methods through the inter-laboratory comparison study to assess the analytical performance of microextraction techniques against conventional methods. Succinctly, developed microextraction methods are shown to impart significant benefits over conventional techniques. Provided that the analytical community continues to put forward attention and resources into the growth and validation of the microextraction technique, a promising future for microextraction is forecasted.

A review on the stereospecific fate and effects of chiral conazole fungicides

The production and use of chiral pesticides are triggered by the need for more complex molecules capable of effectively combating a greater spectrum of pests and crop diseases, while sustaining high production yields. Currently, chiral pesticides comprise about 30% of all pesticides in use; however, some pesticide groups such as conazole fungicides (CFs) consist almost exclusively of chiral compounds. CFs are produced and field-applied as racemic (1:1) mixtures of two enantiomers (one chiral center in the molecule) or four diastereoisomers, i.e., two pairs of enantiomers (two chiral centers in the molecule). Research on the stereoselective environmental behavior and effects of chiral pesticides such as CFs has become increasingly important within the fields of environmental chemistry and ecotoxicology. This is motivated by the fact that currently, the fate and effects of chiral pesticides such as CFs that arise due to their stereoselectivity are not fully understood and integrated into risk assessment and regulatory decisions. In order to fill this gap, a summary of the state-of-the-art literature related to the stereospecific fate and effects of CFs is needed. This will also benefit the agrochemistry industry as they enhance their understanding of the environmental implications of CFs which will aid future research and development of chiral products. This review provides a collection of >80 stereoselective studies for CFs related to chiral analytical methods, fungicidal activity, non-target toxicity, and behavior of this broadly used pesticide class in the soil environment. In addition, the review sheds more light on mechanisms behind stereoselectivity, considers possible agricultural and environmental implications, and suggests future directions for the safe use of chiral CFs and the reduction of their environmental footprint.

Residue analysis and dietary exposure risk assessment of acibenzolar-S-methyl and its metabolite acibenzolar acid in potato, garlic, cabbage, grape and tomato

Acibenzolar-S-methyl (ASM) is one of the most effective plant resistance activators and protects against a broad spectrum of fungal, bacterial and viral pathogens. A rapid, efficient and high-throughput analysis method for ASM and its metabolite acibenzolar acid in fruits and vegetables was developed using potato, garlic, cabbage, grape and tomato as representative commodities by modified QuEChERS and UPLC-MS/MS. The modified procedure showed satisfying recoveries (70-108%) fortified in the range of 0.01-1 mg/kg with relative standard deviations (RSDs) lower than 17.7%. With the established analytical method, the dietary risk of ASM in fruits and vegetables from Chinese markets were further monitored using risk quotient (RQ) method. The RQ value based on ASM residue in China are far less than 1, elucidating that the potential health risk induced by ASM ingestion for Chinese population is not significant. Comparing the residue and risk assessment results of ASM in agricultural products in China to those in Codex, the maximum residue limits (MRLs) for ASM on garlic, cabbage and tomato established by CAC (Codex Alimentarius Commission) can be safely adopted in China, whereas the MRLs on potato and grape in China should be proposed as 0.01 mg/kg.

Enantioseparation and stereoselective dissipation of the novel chiral fungicide pydiflumetofen by ultra-high-performance liquid chromatography tandem mass spectrometry

Pydiflumetofen is a novel and efficient broad-spectrum chiral fungicide consisting of a pair of enantiomers. A simple and sensitive chiral analytical method was established to determine the enantiomers of this chiral fungicide in food and environmental samples by ultra-high-performance liquid chromatography tandem triple quadrupole mass spectrometry (UHPLC-MS/MS) using QuEChERS method coupled with octadecylsilane-dispersive solid-phase extraction (C₁₈-dSPE) as extraction procedure. The specific optical rotation and the absolute configuration of the enantiomers were identified by polarimetry and electronic circular dichroism (ECD). The elution order of the pydiflumetofen enantiomers on Lux Cellulose-2 was S-(-)-pydiflumetofen and R-(+)-pydiflumetofen. The average recoveries of eleven matrices ranged from 71.3% to 107.4%. The intraday relative standard deviations (RSDs) were less than 11.8%, and the interday RSDs were less than 12.6% for the two enantiomers. Stereoselective dissipation in pakchoi and soil were observed: S-(-)-pydiflumetofen was degraded faster than R-(+)-pydiflumetofen in pakchoi, causing the enantiomer fraction (EF) of the enantiomers to change from 0.50 to 0.42 in 7 days. However, R-(+)-pydiflumetofen was degraded faster than S-(-)-pydiflumetofen in soil, causing the EF of the enantiomers to change from 0.49 to 0.52 in 21 days. This study provides a method for monitoring pydiflumetofen enantiomer residues, which is crucial for improving risk assessments and the development of chiral pesticides.

Dissipation, Processing, Leaching, and Safety Evaluation of Flonicamid and Its Metabolites in Tea

BACKGROUND

Tea is a popular traditional non-alcoholic beverage worldwide. Flonicamid is a selective systemic pyridine carboxamide insecticide that is widely used for controlling tea leafhopper in tea.

OBJECTIVE

The leaching rates, dissipation dynamics, and residue levels of flonicamid and its metabolites in tea leaves during processing and transferring were investigated to validate the safe risk in tea and transfer behavior using high performance liquid chromatography-tandem mass spectrometry with a convenient pretreatment method.

METHOD

The extracting method and immersion rate experiments were optimized by single factor analysis and orthogonal tests. The acetonitrile extracting solvent with 0.5% formic acid was used and optimal leaching conditions were obtained with a regime of 15 min immersion time, 100°C temperature, three immersions and a tea-to-water ratio of 1:50.

RESULTS

Average recoveries in processed green tea and infusions were 80.85-98.75% with relative standard deviations <5.87%. LODs and LOQs of flonicamid, 4-trifluoromethylnicotinic acid (TFNA), N-(4-trifluoromethylnicotinoyl) glycine (TFNG), and 4-trifluoromethylnicotinamide (TFNA-AM) were 0.0013-0.350 and 0.004-1 μg/g, respectively. The processing factor of flonicamid was 0.36-5.52 during green tea manufacture. The leaching rates were 22.9-97.4% from processed tea to infusion.

CONCLUSIONS

The risk of long-term and short-term dietary intake of flonicamid was safe in tea infusions with the risk quotient (RQ) values <1 for the Chinese consumer. This work may provide guidance for safe and reasonable consumption of flonicamid in tea in China.

HIGHLIGHTS

The suitable leaching factors of flonicamid and its metabolites in tea infusions were optimized by orthogonal experimentation for the first time.

Enantioselective residue analysis of oxathiapiprolin and its metabolite in tea and other crops by ultra-high performance liquid chromatography-tandem mass spectrometry

Oxathiapiprolin is the first chiral piperidinyl thiazole isoxazoline fungicide developed to control downy mildew and other diseases, and there were no prior reports on its enantiomeric residue. In this study, a modified quick, easy, cheap, effective, rugged, and safe extraction and purification method followed by ultra-high performance liquid chromatography-tandem mass spectrometry determination was first developed and validated for the residue analysis of oxathiapiprolin enantiomers and its metabolite IN-E8S72 in green tea and other crops. Oxathiapiprolin enantiomers and IN-E8S72 were separated on a chiral Lux Cellulose-3 column with the use of 0.1% formic acid in acetonitrile and 5 mmol/L ammonium acetate in water as mobile phases. IN-E8S72 was eluted first, followed by (-)-oxathiapiprolin, and then (+)-oxathiapiprolin. The recoveries ranged from 53.3 to 125.3% with relative standard deviations ranging from 1.4 to 16.0%. The limits of quantification for (-)-oxathiapiprolin and (+)-oxathiapiprolin were 0.005 mg/kg in romaine lettuce, head cabbage, potato, grape, and garlic, 0.01 mg/kg in soybean and pea, and 0.025 mg/kg in green tea and dry pepper. The limits of quantification of IN-E8S72 were twice those of (-)-oxathiapiprolin. Screening results with real market samples indicated that there was no enantiomeric excess in the oxathiapiprolin residue in romaine lettuce.

Acute exposure to the fungicide penconazole affects some biochemical parameters in the crayfish (Astacus leptodactylus Eschscholtz, 1823)

Penconazole is one of the most widely used fungicides all over the world, and since it spreads to large environments, its toxic effects on non-target organisms are of great concern. The toxic effects of penconazole on crayfish (Astacus leptodactylus), which is a bioindicator in freshwater ecosystems and consumed economically, are not known. Therefore, in this study, the purpose was to contribute to the literature on the potential harmful effects of penconazole on a non-target species, Astacus leptodactylus. For this aim, the acute toxicity (96 h) of penconazole was examined. The 96-h LC₅₀ value of penconazole was detected as 18.7 mg L^-1. Four concentrations of penconazole (18.7 mg L^-1, 9.35 mg L^-1, 4.68 mg L^-1, 2.34 mg L^-1) were applied to crayfish for 96 h. The results showed that penconazole had destructive effects on esterase mechanisms by inhibiting acetylcholinesterase (AChE) and carboxylesterase (CaE) activities. Significant increases were observed in all antioxidant parameters (superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), reduced glutathione (GSH), malondialdehyde (MDA)) in all doses except the lowest concentration (2.34 mg L^-1). All adenosine triphosphatase (ATPase) activities (Na⁺/K⁺-ATPase, Mg²⁺-ATPase, Ca²⁺-ATPase, total ATPase) had significant dose-related inhibition in both gill and muscle tissues. In summary, our findings show that acute penconazole administration to crayfish causes significant toxic effects on esterase, antioxidative parameters, and metabolic enzymes.

Deep eutectic solvent-based dispersive liquid-liquid micro-extraction of pesticides in food samples

Deep eutectic solvents are versatile, green and new generation solvents that can be used during dispersive liquid-liquid micro-extraction techniques for pesticides. They have tunable physico-chemical properties that can be easily changed by varying the ratios of hydrogen bond donors and hydrogen bond acceptors in their structures. Deep eutectic solvents are non-flammable, chemically and thermally stable solvents with low vapour pressure. Thus, they have characteristics that are similar to those of ionic liquids. However, they have simpler synthetic procedures, less expensive and are more biodegradable than ionic liquids. One of the limitations of deep eutectic solvents is their toxicity to the environment but they are less toxic than ionic liquids. This paper gives a focused and comprehensive recent review on the applications of deep eutectic solvents during dispersive liquid-liquid micro-extraction of pesticides in food samples for the period starting from 2016 to 2020. Emphasis was placed on the modifications done to the deep eutectic solvent-based dispersive liquid-liquid micro-extraction techniques in order to enhance their greenness during pesticide pre-concentration in food samples. In addition, hyphenated dispersive liquid-liquid micro-extraction techniques were also reviewed and lastly, the paper outlined the challenges associated with the use of DESs during the DLLME techniques.

Metabolism of esfenvalerate in tomato plants (Solanum lycopersicum)

The metabolic fate of esfenvalerate (1), ¹⁴C-labeled at the chlorophenyl or phenoxyphenyl ring, in tomato plants was investigated by spraying it three times at 15 g/ha. The overall metabolic trend of 1 was similar in foliage and fruit. The applied 1 gradually penetrated into the foliage/fruit, and approximately 30% of the total radioactive residue (TRR) distributed within the plant. The applied radioactivity remained mostly intact on the plant surface, while its degradation proceeded via ester cleavage to produce two corresponding acids derived from the chlorophenyl and phenoxyphenyl moieties, followed by saccharide conjugation at the inner tissues (each <5%TRR). While 1 retained its optical configuration (2S,αS) on the plant surface and in the fruit, a very slight isomerization at the α-cyanobenzyl carbon occurred to form a (2S,αR) isomer in the foliage (≤1%TRR). The isomerization at another asymmetric carbon C2 in the isovaleric acid moiety did not proceed on/in the plant for 1 or its metabolite.

Enantioseparation and Determination of Penconazole in Rat Plasma by Chiral LC-MS/MS: Application to a Stereoselective Toxicokinetic Study

In this study, a specific and sensitive method of liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) was developed for the determination of penconazole enantiomers in rat plasma. The enantioseparation was achieved on a Chiralpak IC column by using acetonitrile/water (80:20, v/v) as the mobile phase. Penconazole enantiomers and internal standard l-lansoprazole (IS) were detected in multiple reaction monitoring (MRM) mode with positive electrospray ionization source. The method was validated over the concentration range of 2.5–250.0 ng mL⁻¹ for penconazole enantiomers. Good linearity was obtained for both enantiomers with correlation coefficients (R) greater than 0.995. The relative error was well within the admissible range of −1.1–3.2%, and relative standard deviation was less than 6.0%. After validation, the established method was successfully applied to a stereoselective toxicokinetic study in female and male rats after oral administration of 50 mg kg⁻¹ racemic penconazole. This is the first experiment regarding the stereospecific toxicokinetic study of penconazole and the bioanalytical approach for its quantitation in vivo.

A magnetic multi-walled carbon nanotube preparative method for analyzing asymmetric carbon, phosphorus and sulfur atoms of chiral pesticide residues in Chinese herbals by chiral liquid chromatography-quadrupole/linear ion trap mass spectrometry determination

An analytical method for the determination of asymmetric carbon, phosphorus and sulfur atoms in chiral pesticide residues by magnetic multi-walled carbon nanotube sample pretreatment combined with chiral ultra-performance liquid chromatography/quadrupole/linear ion trap mass spectrometry (UPLC-MS/Qtrap) was developed and applied to chiral pesticide residues analysis in Chinese herbals. Eleven different chiral pesticides were found, and 36.4% were positive in Chinese herbals. Three plants containing detectable pesticide residues were observed in Dendrobium nobile, Panax notoginseng flowers and honeysuckle, in the order of decreasing detected concentration. High detection frequencies of 26.1% for (R/S)-(±)-difenoconazole and 14.5% for (R/S)-(±)-metalaxyl and (R/S)-(±)-propiconazole were observed, the residual amount for (R/S)-(±)-difenoconazole, (R/S)-(±)-metalaxyl and (R/S)-(±)-propiconazole were 0.32 ~ 2.5 mg/kg, 0.022 ~ 0.23 mg/kg, 0.62 ~ 3.21 mg/kg respectively. The EF value of (R/S)-(±)-difenoconazole was 0.506 ± 0.046. The EF value of (R/S)-(±)-metalaxyl was lower than 0.5 in Dendrobium nobile, Panax notoginseng flowers, Panax notoginseng roots and hawthorn. The EF of (R/S)-(±)-propiconazole was not significantly enantioselective in honeysuckle and Panax notoginseng flowers. The enantioselectivity of various pesticide residues in different plants cannot be predicted from our existing knowledge and may closely depend on plant growth, environmental conditions or molecular structure.

Simultaneous determination of eight neonicotinoid insecticides, fipronil and its three transformation products in sediments by continuous solvent extraction coupled with liquid chromatography-tandem mass spectrometry

Neonicotinoids (NEOs) and fipronil (FIP) are insecticides that are widely used in modern agriculture and have received considerable attention in recent years due to their adverse effects on non-target organisms in the environment. In the present study, a new method to simultaneously detect eight common NEO insecticides and FIP and its three transformation products (FIPs) in sediments was developed using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) based on a combined pretreatment of continuous solvent extraction (CSE) and solid phase extraction (SPE). Under optimized conditions, 5.0 g of freeze-dried sediment samples were initially extracted with methanol (20 mL)-methanol (15 mL)-water (20 mL) in sequence, and then the extract was cleaned with hydrophilic-lypophilic balance SPE cartridges, and HPLC-MS/MS analysis was conducted. The established method was validated to be sensitive, linear, accurate, and precise. The limits of detection (LOD) and limits of quantification (LOQ) of target compounds were 0.012-0.055 μg/kg d.w and 0.031-0.091 μg/kg d.w, respectively. Good linearity (R² > 0.990) was observed between 4.0 × 10^-2 and 20.0 μg/kg d.w. The recovery rates of all target insecticides were between 75.5% and 98.5%, and the relative standard deviations (RSD) were all less than 15.0% at the low, medium, and high spiked levels. Finally, the optimized method was applied to analyze 12 target insecticides in the sediments obtained from Jiaozhou Bay of China and its main inflow rivers. Acetamiprid, thiamethoxam, fipronil sulfide, and fipronil sulfone were detected in the river sediment samples at the concentration from <LOQ to 0.197 μg/kg d.w. Thus, the two types of studied insecticides can enter the sedimentary environment. Overall, the proposed method can be used to investigate the contamination status of typical NEOs and FIP insecticides in sediments and provide base data to comprehensively understand their environmental behavior, safety, and fate.

Effect of Biochar on the Enantioselective Soil Dissipation and Lettuce Uptake and Translocation of the Chiral Pesticide Metalaxyl in Contaminated Soil

Enantioselectivity is usually ignored when assessing potential biochar-based methods of redressing pesticide contamination of soils. In this study, the effect of woodchip biochar (WBC) on the enantioselective dissipation of metalaxyl in soil and its uptake and translocation by lettuce were investigated. S-metalaxyl (T1/2 = 29.8 days) dissipated more quickly than R-metalaxyl (T1/2 = 36.4 days) in unamended soil. The addition of WBC to the soil decreased the dissipation rate and the enantioselectivity of metalaxyl. Metalaxyl distribution showed opposing enantioselectivity in lettuce, with roots and shoots showing preferences for R-metalaxyl and S-metalaxyl, respectively. Enrichment with WBC decreased the concentrations of metalaxyl and metalaxyl acid enantiomers in lettuce and reduced the ability of the shoots to transport the highly toxic R-metalaxyl from roots. This is the first study to provide evidence that amending soil with biochar affects the enantioselective uptake and translocation of a chiral pesticide.

Novel Liquid Chromatography-Tandem Mass Spectrometry Method for Enantioseparation of Tefluthrin via a Box-Behnken Design and Its Stereoselective Degradation in Soil

A simple and eco-friendly dispersive solid-phase extraction method coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the determination of the chiral pesticide tefluthrin in food and environmental samples. The response surface methodology was applied to optimize separation conditions. The elution order of tefluthrin enantiomers was Z-cis-(1S,3S)-(-)-tefluthrin and Z-cis-(1R,3R)-(+)-tefluthrin on a Lux Cellulose-1 chiral column was identified via a polarimeter and vibrating circular dichroism. The average recoveries in five matrices ranged from 76.9 to 107.6%, with intraday relative standard deviations (RSDs) less than 15.6% and interday RSDs less than 12.5% for two enantiomers. The enantioselective degradation was investigated via laboratory incubation experiments. Slightly enantioselective degradation was observed under aerobic conditions; (1S,3S)-tefluthrin degraded preferentially with the enantiomer fraction value of 0.57 at 120 days of incubation. No remarkable enantioselective degradation was observed under anaerobic and sterile conditions. It was the first time that pyrethroid pesticides were determined at the enantiomer levels via UPLC-MS/MS. This novel method was successfully applied for the enantioselective analysis of tefluthrin enantiomers in authentic samples, indicating its efficacy in investigating the environmental stereochemistry of tefluthrin in the food web and environment. It is of crucial importance to improve risk assessment and regulation of chiral pesticides in an agricultural system.