Chiral Pesticides Research Articles

Low-dose cadmium affects the enantioselective bioaccumulation and dissipation of chiral penflufen in zebrafish (Danio rerio)

Pesticides are currently extensively used in agriculture, forestry, animal husbandry, and environmental hygiene, and their residues have become a global environmental problem, which can easily form combined pollution with heavy metals. The present study examined the effects of chronic (28 days) aqueous exposure of chiral penflufen (rac-penflufen, R-(-)-penflufen and S-(+)-penflufen), a widely used fungicide, with/without cadmium (Cd), a highly toxic heavy metal in zebrafish (Danio rerio). After rac-penflufen individual or combined exposure with Cd, the bioaccumulation and residual levels of S-(+)-penflufen were significantly higher than R-(-)-penflufen, and the effects of Cd were insignificantly. But for penflufen enantiomer, the effects of Cd were more serious for R-(-)-penflufen, which could increase the bioaccumulation (up to1.73 times), inhibit the dissipation (up to 32.3%) and enhance the residue (up to 5.35 times) of R-(-)-penflufen in zebrafish, decreasing the enantioselectivity. However, significant increase of S-(+)-penflufen concentrations was only found in viscera under co-exposure of Cd. The tissue distribution of penflufen enantiomers were not affected by the presence of Cd, and no interconversion of the two enantiomers occurred regardless of the presence of Cd. These findings indicated that co-contamination with Cd could increase the persistence of R-(-)-penflufen in zebrafish, thus increasing the environmental risks. The significant differences of Cd effects on chiral pesticide enantiomer and racemate indicated that the combined pollution of heavy metal and chiral pesticide might have enantiomer-specific, which should raise concern, and the enantioselective mechanism deserve further study.

Fate of the neonicotinoid insecticide cycloxaprid in different soils under oxic conditions

Neonicotinoids are the most widely used pesticides worldwide due to their high toxicity to invertebrates. However, these compounds also increase the probability of environmental contamination. Cycloxaprid (CYC) is a promising neonicotinoid due to its insecticidal effectiveness and low cross resistance, but little is known about its fate in soils. Using radioisotope tracing techniques, the fate of 14C-labeled CYC enantiomers and racemic mixtures in aerobic soil was investigated in this research. After 100 d of incubation, the extractable residue (ER) of CYC decreased from 89.6% to 36.4% in red clay soil, from 46.1% to 10.1% in yellow loam soil, and from 93.2% to 12.2% in coastal saline soil. The radioactivity was substantially lower in methanol than in the other two solvents, but the distribution of CYC ER in various solvents across the three soils dramatically differed. The fraction of radioactive CYC that diffused into bound residue (BR) in the three soils increased over time to 56.8–83.0%. The variability in BR was influenced by soil properties such as organic matter concentration, pH, and residual microbial activity. Among the soils, yellow loam soil had the greatest tendency (53.0–83.0%) to form BR, while red clay soil showed the lowest capacity (7.5–61.2%). Cumulative mineralization (MI) to 14CO2 accounted for 0.12–0.23%, 6.69–7.31% and 14.82–20.06% in acidic soil, neutral soil and alkaline soil, respectively, which suggests that the environmental fate of chiral pesticides may be influenced by soil pH. No stereoselective behavior was detected in this study. These findings provide a framework to assess the environmental impact and ecological safety of CYC application.

Chiral Pesticides with Asymmetric Sulfur: Extraction, Separation, and Determination in Different Environmental Matrices

Chiral pesticides with S atoms as asymmetric centers are gaining great importance in the search for new pesticides with new modes of action. As for the rest of the chiral pesticides, the determination of the stereoisomers separately has become crucial in the environmental risks assessment of these pesticides. Therefore, the development of suitable extraction and clean-up methods as well as efficient stereoselective analytical techniques for stereoisomers determination in environmental samples is essential. Currently, liquid/solid phase extraction, microextraction, and QuEChERS-based methods are most commonly used to obtain chiral pesticides from environmental samples. Gas, liquid, and supercritical fluid chromatography together with capillary electrophoresis techniques are the most important for the determination of the stereoisomers of chiral pesticides containing S atoms in its structure. In this study, all these techniques are briefly reviewed, and the advantages and disadvantages of each are discussed.

Multi-walled carbon nanotubes impact on the enantioselective bioaccumulation and toxicity of the chiral insecticide bifenthrin to zebrafish (Danio rerio)

The effects of different multi-walled carbon nanotubes on the enantioselective bioaccumulation and toxicity of the chiral pesticide bifenthrin to zebrafish were investigated in this work. The results showed that MWCNTs and MWCNTs-COOH did not affect the preferential bioaccumulation of 1R-cis-BF in zebrafish following exposure to cis-BF enantiomers for 28 days, but which increased cis-BF accumulation amount by 1.03–1.48 times. Further research demonstrated that the genes related to immunity, endocrine activity and neurotoxicity showed enantioselective expression in different zebrafish tissues, and sex-specific differences were observed. The levels of c-fos, th, syn2a, 17β-hsd and cc-chem were expressed as 1.09–2.84 times higher in females and males treated with 1R-cis-BF than in the 1S-cis-BF-treated groups. However, in the presence of MWCNTs or MWCNTs-COOH, c-fos, th, syn2a, 17β-hsd and cc-chem levels were expressed as 1.53–14.92 times higher in females and males treated with 1S-cis-BF than in 1R-cis-BF-treated groups, which indicated that enantioselective expression was altered. The effects of different types of MWCNTs on the enantioselective bioaccumulation and toxicity of BF in zebrafish have little difference. In summary, the presence of MWCNTs or MWCNTs-COOH increased the impact of BF on zebrafish. Therefore, the risks posed by coexisting nanomaterials and chiral pesticides in aquatic environments should be considered.

Evaluation of chiral triticonazole in three kinds of fruits: enantioseparation, degradation, and dietary risk assessment.

The enantioselective behaviors of chiral pesticides would affect the accuracy of risk assessment. This study evaluated the enantioselectivity of chiral triticonazole (a widely used fungicide) in three kinds of fruits. Firstly, the enantioseparation of triticonazole enantiomers was carried out within 1.2min utilizing CHIRALPAK OJ-3 column with a mixture of CO2 and methanol (93:7, v/v) using SFC-MS/MS. Secondly, field trials were conducted to clarify the enantioselective degradation and residue of S-( +)-triticonazole and R-(-)-triticonazole in fruits. The initial concentrations of rac-triticonazole were 25.1-93.1ng/g, and enantioselective degradation was observed in pear, peach, and jujube after 2h, 10days, and 3days, respectively. The degradation of S-( +)-triticonazole was fastest in pear (T1/2, 2.01days), while the T1/2 of R-(-)-triticonazole was 5.02days. The residue concentrations of rac-triticonazole were less than the MRL set by EU (10ng/g) on the 3rd and 21st day in pear and peach, respectively, which were lower than 10ng/g in jujube on the 30th day (no MRL). Finally, we found that the dietary intake risks of rac-triticonazole in fruits were low for 2-7 age, 20-50 age/female, and 20-50 age/male. The current study could provide complimentary references for the rational usage, MRL formulation, and risk assessment of chiral triticonazole.

Enantioselective bioaccumulation and toxicity of rac-sulfoxaflor in zebrafish (Danio rerio)

Sulfoxaflor is a fourth-generation neonicotinoid insecticide mainly used to control sap-feeding pests. In this study, four stereoisomers of sulfoxaflor were separated using HPLC, and the absolute configurations of three stereoisomers were identified via single-crystal X-ray diffraction. First, the stability and isomerization of the four enantiomers and rac-sulfoxaflor in water and seven organic solvents were investigated. All enantiomers were extremely unstable in water with isomerization rates above 20%. The racemate did not isomerize in any of the solutions and was stable in water (degradation rate less than 7%). Therefore, we studied the acute toxicity, enantioselective behavior, and enzymatic activities of rac-sulfoxaflor in zebrafish. The bioaccumulation experiment demonstrated that the bioconcentration of sulfoxaflor in zebrafish was enantioselective, and the four enantiomers accumulated in zebrafish in the order (+)-2S,3S-sulfoxaflor > (−)-2R,3R-sulfoxaflor > (+)-2R,3S-sulfoxaflor > (−)-2S,3R-sulfoxaflor. The effect of rac-sulfoxaflor on the enzymatic activities of zebrafish showed that superoxide dismutase and glutathione-S-transferase activities and malondialdehyde content were significantly enhanced as compared to those in control, whereas acetylcholinesterase was significantly reduced in the sulfoxaflor exposure treatment (p < 0.05), indicating that sulfoxaflor caused oxidative lesions and induced enzymatic activity in zebrafish. This study provides important information on the enantioselective behavior and toxic effects of sulfoxaflor, which can help assess the potential ecological risk of chiral pesticides to aquatic organisms.

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.

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.

Metabolomic and transcriptomic investigation of the mechanism involved in enantioselective toxicity of imazamox in Lemna minor

Imazamox (IM) is a chiral pesticide that has been widely used in agriculture. Currently, few studies have investigated the toxicity mechanisms of imazamox to aquatic macrophyte from the enantiomer level. In this study, the enantioselective effects of IM on the toxicity and physiological and biochemical system of aquatic macrophyte Lemna minor were systematically investigated. Metabolomic and transcriptomic for Lemna minor were used to identify potential mechanisms of toxicity. 7 d EC50s for racemic-, R-, and S-IM were 0.036, 0.035, and 0.203 mg/L, respectively, showing enantioselective toxicity. In addition, IM caused Lemna minor lipid peroxidation and antioxidant damage, and inhibited the activities of the target enzymes. Metabolomic and transcriptomic data indicated that R-IM interferenced differentially expressed genes and metabolites of Lemna minor which were enriched in carbon fixation during photosynthesis, glutathione metabolic pathway, pentose phosphate pathway, zeatin biosynthesis, and porphyrin and chlorophyll metabolism. S-IM affected phenylalanine metabolism, phenylpropanoid biosynthesis, zeatin biosynthesis and secondary metabolite biosynthesis. Racemic-IM influenced carbon fixation during operation, glutathione metabolic pathway, zeatin biosynthesis and pentose phosphate pathway. The results provide new insights into the enantioselective toxicity mechanisms of IM to Lemna minor, and lay the foundation for conducting environmental risk assessments.

Impact of chiral tebuconazole on the flavor components and color attributes of Merlot and Cabernet Sauvignon wines at the enantiomeric level

The impact of chiral tebuconazole on the flavor and appearance of Merlot and Cabernet Sauvignon wines were systematically studied. Gas chromatography-ion mobility spectrometry and headspace-solid phase microextraction coupled with gas chromatography mass spectrometry qualitatively and quantitatively identified the flavor components, and a photographic colorimeter was used for color attribute analysis. Tebuconazole enantiomers had different effects on the flavor and appearance of young wines, especially R-tebuconazole. The flavor differences were mainly manifested in fruity and floral characteristics of the wine due to changes in the concentrations of acids, alcohols, and esters; R-tebuconazole alters the concentrations of key flavor compounds to the greatest extent. Tebuconazole treatment changes the color of young wines, with the final red shade of wine being control group > rac-tebuconazole ≥ S-tebuconazole > R-tebuconazole. Since chiral tebuconazole negatively alters wine, grapes treated with chiral pesticides should be subject to stricter quality control during processing.

Enantiomer/stereoisomer-specific residues of metalaxyl, napropamide, triticonazole, and metconazole in agricultural soils across China.

In this study, the residual status of four chiral pesticides including metalaxyl, napropamide, triticonazole, metconazole, and their enantiomers/stereoisomers were investigated in agricultural soils across China. The levels in the soils were detected as non-detected (n.d.)-16.67 ng/g for metalaxyl with a median of 0.14 ng/g; 0.004-32.99 ng/g for napropamide with a median of 0.29 ng/g; n.d.-207.39 ng/g for triticonazole with a median of 1.29 ng/g; and n.d.-71.83 ng/g for metconazole with a median of 1.03 ng/g, respectively. Enantiomer/stereoisomer-specific residues were observed for metalaxyl and triticonazole. R-Metalaxyl and R-triticonazole were identified as the major enantiomers in the soils for the two pesticides. There was no obvious enantioselective residue for napropamide in most of the soils. As for metconazole, metconazole-1 and metconazole-4 were identified as the major stereoisomers in the soils. These results suggest that enantiomer/stereoisomer-specific risk should be considered when assessing the ecological safety of these pesticides in soils.

On-line coupling of supercritical fluid extraction with enantioselective supercritical fluid chromatography-triple quadrupole mass spectrometry for the determination of chiral pesticides in hemp seeds: A proof-of-principle study

The present research can be considered as a proof-of-principle study focused on the determination of chiral pesticides using a supercritical fluid extraction instrument coupled on-line with an enantioselective supercritical fluid chromatography-triple quadrupole mass spectrometry. To the best of Authors’ knowledge, this is the first description of an on-line approach for the extraction and determination of chiral pesticides. Metalaxyl, benalaxyl and dimethenamid were investigated in nine hemp seed samples belonging to four varieties of Cannabis sativa; only in one case a pesticide was found at levels above the method limit of quantification (LoQ), though within the EU maximum residue level value. The figures-of-merit determined were linearity, precision, limit of detection (LoD), and LoQ. Regression coefficients were between 0.9856 and 0.9973, the LoDs were in the 0.04–0.41 μg kg−1 range, the LoQs were in the 0.12–1.38 μg kg−1 range, while coefficients of variation were between 1 and 3% (10 μg kg−1 level).

Enantiomer metabolism of acephate and its metabolite methamidophos in in vitro tea (Camellia sinensis L.) systems: Comparison between cell suspensions and excised tissues

Enantioselective metabolism of chiral pesticide in plants is very important. In vitro system has become an effective means to study the metabolism of pesticides in plants, but the study on the metabolism of chiral pesticides has not been reported. This work compared the enantiomer metabolic behavior of acephate and its metabolite methamidophos between tea cell suspensions and excised tea stem with leaves. (±)-Acephate could be absorbed and transferred well to top leaves by the cut end of excised stem after 24 h. (±)-Methamidophos was derived from the metabolism of (±)-acephate in tea plants at 3–5% in leaves and 2–3% in stems at 216 h. The content of (+)-methamidophos was 1.5 times higher than that of (−)-methamidophos in excised leaves. Though both (±)-acephate and (±)-methamidophos could be metabolized well by cell suspension, (±)-acephate and (±)-methamidophos was non-enantioselectively metabolized in cell suspension. It was shown that using the excised tea stem with leaves for chiral pesticide metabolism studies was much closer to intact plant than cell suspensions. This result also established an effective and easily available in vitro metabolic model for the study of enantioselective metabolism of chiral contaminants from environment.

Stereochemistry of chiral pesticide uniconazole and enantioselective metabolism in rat liver microsomes

In this work, stereochemistry of uniconazole enantiomers and their metabolism behaviors in rat liver microsomes have been researched. Significance analysis has been applied in data processing. Absolute configurations of uniconazole enantiomers were identified through vibrational circular dichroism spectroscopy. According to their elution order from the chiral column using the CO2-methanol (80:20, v/v) mixture, two eluted fractions were determined to be (R)-uniconazole and (S)-uniconazole, respectively. A high-efficient and sensitive LC-MS/MS chiral analysis method was established for investigating the metabolism of uniconazole enantiomers in rat liver microsomes. The metabolic half-life of (R)-uniconazole (38.7 min) in rat liver microsomes was half that of (S)-enantiomer (74.5 min), and maximum velocity of metabolism, Michaelis constant of metabolism as well as the intrinsic metabolic clearance of (R)-uniconazole were significantly higher than (S)-enantiomer (p < 0.05), which indicated that (R)-uniconazole was preferentially metabolized in rat liver microsomes. By the virtue of molecular docking, (R)-uniconazole exhibited a higher binding affinity to cytochrome CYP2D2 than (S)-enantiomer, which corroborated well with the metabolism results. This work will shed light on the risk assessment of uniconazole toward human health and the ecological environment.

Enantioselective Fungicidal Activity and Toxicity to Early Wheat Growth of the Chiral Pesticide Triticonazole.

In this study, the enantioselective activity of the chiral fungicide triticonazole (TRZ) against target pathogens of seed-borne diseases and the effect on the early phenotypic indexes and physiological and biochemical indexes of wheat following the soaking of seeds were studied. S-TRZ had low fungicidal activity and significantly inhibited the germination of wheat seeds. Seedlings in the S-TRZ treatment group suffered severe oxidative damage; the contents of glutathione (GSH) and malondialdehyde (MDA) were significantly increased. S-TRZ significantly inhibited the synthesis of gibberellin (GA) and ethylene (ETH), while it significantly increased that of jasmonic acid (JA). R-TRZ showed the highest activity against two smut fungi; the treatment of seeds with 5 g (ai)/100 kg R-TRZ had little influence on early wheat growth. The plant hormones were synthesized normally; seedlings grew well, and the fresh weight increased significantly following this treatment. Based on these data, we propose to develop and apply R-TRZ using the national recommended doses to control seed-borne diseases of wheat.

Magnetic solid-phase extraction based on zirconium-based metal–organic frameworks for simultaneous enantiomeric determination of eight chiral pesticides in water and fruit juices

A novel multi-residue method, magnetic solid-phase extraction combined with LC–MS/MS, was proposed for simultaneous enantiomeric determination of eight chiral pesticides in water and fruit juices. Fe3O4@C@UiO-66 was firstly used to extract and enrich pesticides, showing excellent adsorption capacity, which was proved by adsorption kinetic and thermodynamic experiments. Multiple extraction parameters were optimized by Plackett-Burman and Box-Behnken design. Under optimized conditions, good linearity (1.0–200 ng L−1, R2 ≥ 0.9953) for all analytes, detection limits (0.10 to 0.35 ng L−1), quantitation limits (0.35 to 1.00 ng L−1), recoveries (83.68–95.99%), and precision (intra-day RSD ≤ 7.06%, inter-day RSD ≤ 9.40%) were obtained, meeting the requirements of pesticides residues analysis. It is worth mentioning that eight chiral pesticides can be separated quickly within 19 min. The above results indicate that the proposed method with satisfactory sensitivity and accuracy has the potential for routine analysis of chiral pesticide residues in aqueous samples.

In vitro enantioselective inhibition of the main human CYP450 enzymes involved in drug metabolism by the chiral pesticide tebuconazole

Tebuconazole (TEB) is a chiral triazole fungicide worldwide employed to control plant pathogens and preserve wood. People can be exposed to TEB either through diet and occupational contamination. This work investigates the in vitro inhibitory potential of rac-TEB, S-(+)-TEB, and R-(−)-TEB over the main cytochrome P450 enzymes (CYP450) using human liver microsomes to predict TEB in vivo inhibition potential. The IC50 values showed that in vitro inhibition was enantioselective for CYP2C9, CYP2C19, and CYP2D6, but not for CYP3A4/5. Despite enantioselectivity, rac-TEB and its single enantiomers were always classified in the same category. The inhibition mechanisms and constants were determined for rac-TEB and it has shown to be a mixed inhibitor of CYP3A4/5 (Ki = 1.3 ± 0.3 μM, αKi = 3.2 ± 0.5 μM; Ki = 0.6 ± 0.3 μM, αKi = 1.3 ± 0.3 μM) and CYP2C9 (Ki = 0.7 ± 0.1 μM, αKi = 2.7 ± 0.5 μM), and a competitive inhibitor of CYP2D6 (Ki = 11.9 ± 0.7 μM) and CYP2C19 (Ki = 0.23 ± 0.02 μM), respectively, suggesting that in some cases, rac-TEB has a higher or comparable inhibitory potential than well-known strong inhibitors of CYP450 enzymes, especially for CYP2C9 and CYP2C19. In vitro-in vivo extrapolations (IVIVE) were conducted based on the results and data available in the literature about TEB absorption and metabolism. R1 values were estimated based on the Food and Drug Administration guideline and suggested that in a chronic oral exposure scenario considering the acceptable daily intake dose proposed by the European Food and Safety Authority, the hypothesis of rac-TEB to inhibit the activities of CYP3A4/5, CYP2C9, and CYP2C19 in vivo and cause pesticide-drug interactions cannot be disregarded.

Enantioselective toxicity and mechanism of chiral fungicide penflufen based on experiments and computational chemistry

Penflufen fungicide is widely used as a racemate, which has potential ecological risks to aquatic organisms, while its enantioselective toxicity data is limited. This study aimed to differentiate the enantioselective toxicity difference of penflufen enantiomers, and illuminate the enantioselective mechanism from the insight of enantiomer-protein specific binding. The semipreparative separation and absolute configuration of penflufen enantiomers were conducted. The acute toxicity of S-(+)-penflufen was 54 times higher than R-(-)-penflufen to Danio rerio, and the coexistence of R-(-)-penflufen could increase the exposure risk of S-(+)-penflufen. For chronic toxicity, after low-dose long-term exposure, rac-penflufen and S-(+)-penflufen inducted more serious oxidative stress than R-(-)-penflufen in D. rerio, and inhibited the succinate dehydrogenase (SDH) activity significantly. For target phytopathogen, the toxicity difference of S-(+)-penflufen and R-(-)-penflufen was up to 148 times for Rhizoctonia solani. Based on the toxic unit analysis, the toxic interactions of antagonistic effect and concentration addition were found between penflufen enantiomers, indicating the coexistence of R-(-)-penflufen could increase overuse and environmental risks. Computational chemistry was used to illuminate the enantioselectivity mechanism, and the lower binding energy between the active site of SDH and S-(+)-penflufen contributed to the higher toxicity. The higher target toxicity might be due to the hydrophobic pocket of CybL in R. solani was more benefited to S-(+)-penflufen binding SDH than Botrytis cinerea. These results could be helpful for further understanding the potential risk of chiral penflufen in the environment, demonstrating the importance of understanding the enantioselective difference of chiral pesticides, and providing a new insight for analyzing the enantioselective mechanism.

Analytical research on the separation and residue of chiral pesticide triadimenol in fruit and vegetable puree.

In this paper, a method for the separation of triadimenol stereoisomers using ultra-performance convergence chromatography and an analytical method for the determination of triadimenol stereoisomer residues in pumpkin puree, apple puree, and tomato puree as a supplement for infants are established. Test samples were extracted with acetonitrile and successively purified with graphitized carbon black and Florisil column. Afterward, Acquity Trefoil AMY1 column was adopted for chiral separation of chromatographic column, and gradientelute was carried out with supercritical carbon dioxide-methanol as the mobile phase and with external standard method for quantitation. Results showed that the linearly dependent coefficient of the four kinds of triadimenol stereoisomers within 1.0 and 50mg/L was greater than 0.9997, and the limit of quantitation of the four kinds of triadimenol stereoisomers was 0.05mg/kg. Recovery experiment was carried out within 0.05 and 1.0mg/kg scope, the recoveries were 81.0-107％, and the relative standard deviation was 2.3-7.6%. This method implemented the separation of triadimenol stereoisomers and its residue test in pumpkin puree, apple puree, and tomato puree as a supplement for infants, and it can provide reliable technical support for the analysis of pesticide residue and assessment of product quality.

Determination of myclobutanil enantiomers in wheat and its processed products by ultraperformance liquid chromatography-tandem mass spectrometry based on a chiral stationary phase

建立了手性超高效液相色谱-串联质谱检测小麦及其加工制品中腈菌唑对映体残留的分析方法。样品经乙腈提取,N-丙基乙二胺(PSA)和C18净化,手性色谱柱Lux Cellulose-1(150 mm×2.0 mm, 3 μm)分离,质谱电喷雾正离子扫描(ESI+),多反应监测(MRM)模式进行检测。为准确定量,考察了小麦籽粒及其加工制品的基质效应,最终采用基质匹配校准法来补偿基质效应,并进行样品中腈菌唑对映体残留的校准定量。结果表明,腈菌唑的两个对映体得到良好的拆分。S-(+)-腈菌唑先出峰,R-(-)-腈菌唑后出峰,保留时间分别为4.34 min和5.13 min。S-(+)-腈菌唑和R-(-)-腈菌唑在小麦及其加工制品中的检出限均为0.2 μg/kg,定量限均为0.5 μg/kg。在0.5~25 μg/L范围内,腈菌唑对映体的峰面积与其质量浓度呈现良好的线性关系,相关系数(R2)均大于0.99。在对映体添加水平为5、50、100 μg/kg时,在小麦籽粒、麸皮、面粉、面团、馒头、面条、煮面水中,S-(+)-腈菌唑的平均回收率在82%~110%之间,RSD在0.9%~6.8%之间;R-(-)-腈菌唑的平均回收率在80%~109%之间,RSD在0.9%~6.8%之间。将该方法应用于实际样品的检测,在5份面粉、2份面条及2份馒头样品中均未检出腈菌唑对映体。该方法为手性农药腈菌唑对映体在初级农产品及其加工制品中的残留分析提供了有效的方法。