Oxidative stress, DNA damage, and gene expression in earthworms (Eisenia fetida) exposure to ethiprole.

To evaluate the potential ecotoxicity of ethiprole and early warning to earthworms (Eisenia fetida), different concentrations (0 mg·kg-1, 416 mg·kg-1, 625 mg·kg-1, and 1000 mg·kg-1) of ethiprole were added to artificial soil. The key bioindicators were measured and screened at 3 days, 7 days, 14 days, 21 days, and 28 days. The results show that the activity of catalase (CAT) was inhibited for all treatments during the whole exposure period. Besides, the olive tail moment (OTM) value increased gradually as the concentration got higher, which exhibited a dose-time-dependent relationship. Superoxide dismutase (SOD) gene reached the maximum on the 7th day. Mitochondrial large ribosomal RNA (l-rRNA) subunit gene was always in a downregulated state as the concentration increased. Our results show that different concentrations of ethiprole induced certain oxidative stress, DNA damage, and genotoxicity in earthworms. The CAT activity, OTM, and SOD gene could be the most sensitive biomarkers to monitor the toxicity of ethiprole in the soil.

Residue analysis and dietary risk assessment of picoxystrobin in potato (Solanum tuberosum), citrus fruit (Citrus reticulata Blanco), and Dendrobium officinale Kimura et Migo.

Picoxystrobin is a systemic fungicide widely used on potato, citrus fruit, and Dendrobium officinale. To provide information for the risk assessment of potato, citrus, and Dendrobium officinale, field experiments combined with QuEChERS and HPLC-MS/MS were performed to detect picoxystrobin. Picoxystrobin had good linearity (R2 > 0.99), the average recovery rate was 75 - 102%, and the relative standard deviation was 1 - 11%. Picoxystrobin was utilized as the test agent in field experiments, and samples were evaluated and analyzed at various times after the final application utilizing random sampling. The results showed that picoxystrobin residuals in potato and citrus (orange meat) were ˂ 0.01 mg kg-1, whereas those in citrus whole fruit, D. officinale (fresh), and D. officinale (dried) were < 0.05 - 0.084, 0.16 - 3.82, and 0.34 - 9.05 mg kg-1, respectively. Based on these results, both the acute risk quotient (2.77%) and chronic risk quotient (8.7%) were ˂100%, and the dietary risk assessment indicated that the intake of picoxystrobin residues in potato, citrus fruit, and D. officinale did not pose a health risk. This study can guide the reasonable use of picoxystrobin in potato, citrus fruit, and D. officinale.

A systemic study of cyenopyrafen in strawberry cultivation system: Efficacy, residue behavior, and impact on honeybees (Apis mellifera L.).

The pesticide application method is one of the important factors affecting its effectiveness and residues, and the risk of pesticides to non-target organisms. To elucidate the effect of application methods on the efficacy and residue of cyenopyrafen, and the toxic effects on pollinators honeybees in strawberry cultivation, the efficacy and residual behavior of cyenopyrafen were investigated using foliar spray and backward leaf spray in field trials. The results showed that the initial deposition of cyenopyrafen using backward leaf spray on target leaves reached 5.06-9.81 mg/kg at the dose of 67.5-101.25 g a.i./ha, which was higher than that using foliar spray (2.62-3.71 mg/kg). The half-lives of cyenopyrafen in leaves for foliar and backward leaf spray was 2.3-3.3 and 5.3-5.9 d, respectively. The residues (10 d) of cyenopyrafen in leaves after backward leaf spray was 1.41-3.02 mg/kg, which was higher than that after foliar spraying (0.25-0.37 mg/kg). It is the main reason for the better efficacy after backward leaf spray. However, the residues (10 d) in strawberry after backward leaf spray and foliar spray was 0.04-0.10 and < 0.01 mg/kg, which were well below the established maximum residue levels of cyenopyrafen in Japan and South Korea for food safety. To further investigate the effects of cyenopyrafen residues after backward leaf spray application on pollinator honeybees, sublethal effects of cyenopyrafen on honeybees were studied. The results indicated a significant inhibition in the detoxification metabolic enzymes of honeybees under continuous exposure of cyenopyrafen (0.54 and 5.4 mg/L) over 8 d. The cyenopyrafen exposure also alters the composition of honeybee gut microbiota, such as increasing the relative abundance of Rhizobiales and decreasing the relative abundance of Acetobacterales. The comprehensive data on cyenopyrafen provide basic theoretical for environmental and ecological risk assessment, while backward leaf spray proved to be effective and safe for strawberry cultivation.

Residue Analysis and Dietary Risk Assessment of Pymetrozine in Potato (Solanum tuberosum L.) and Chrysanthemum morifolium (Ramat).

Pymetrozine is used on potato (S. tuberosum) and Chrysanthemum morifolium (C. morifolium) to obtain greater yield and quality. However, pesticide use carries the potential for residues to remain and be detected on harvested crops. Therefore, the aim of this study was to estimate pesticide residues in S. tuberosum and C. morifolium products that are commercially available for human consumption and to assess the associated dietary risks. For this study, a total of 340 samples (200 S. tuberosum samples and 140 C. morifolium samples) were collected randomly from supermarkets and farmer's markets. Residues of pymetrozine in S. tuberosum and C. morifolium were detected by using an established and validated QuECHERS-HPLC-MS / MS method, while a dietary risk assessment of pymetrozine in S. tuberosum and C. morifolium was performed using these data. The detection rates of pymetrozine in S. tuberosum and C. morifolium samples were 92.31% and 98.17%, respectively, with residues not more than 0.036 and 0.024 mg/kg, respectively. Based on these results, the dietary risk assessment indicated that the intake of pymetrozine residues in S. tuberosum and C. morifolium does not pose a health risk. This work improved our understanding of the potential exposure risk of pymetrozine in S. tuberosum and C. morifolium.

Large-scale fate profiling of butralin between cultivated and processed garlics for multi-risk estimations.

Elaborating on the fate profiling and risk magnitude of butralin during large-scale applications was conducive to agroecosystems sustainability and dietary rationality. Occurrence, dissipation and concentration variation of butralin were elucidated from garlic cultivation to household processing by tracing UHPLC-MS/MS within 2 min, with regard to original depositions, half-lives, and terminal magnitude in typical origins of garlic. The processing factors (Pfs) of butralin were further clarified among washing, stir-frying and pickling of garlic crops, and pickling was the most effective way for butralin removal with a Pf of 0.092. A probabilistic model with Pfs was further introduced for the comprehensive risk estimations, by reduction factors of 3.1-10.9 from raw garlic crops to processed products. The short-term risks of butralin from green garlic were greater than those between garlic shoot and garlic, with the %ARfDs of 0.030 %-6.323 % from 50th to 99.9th percentiles. The long-term risks were inversely correlated to the age of the population, whose location in rural (%ADIs, 0.256 %-0.768 %) suffered more serious exposures than in urban (%ADIs, 0.231 %-0.699 %). High potential risk amplification should be continuously emphasized given the increasing applications and persistent fate of butralin, especially for vulnerable rural children.

First report of Fusarium solani causing wilt disease on Gleditsia sinensis in Tianjin, China.

The Gleditsia sinensis Lam. widely grown in China is a perennial plant with medicinal properties (Zhang et al. 2016). Since 2019, the leaves of G. sinensis have exhibited yellowing and wilting, and the plants have gradually become stunted and dead in Taifeng park of Binhai New Area in Tianjin (39.02° N; 117.65° E). In this park, there are two types of G. sinensis, one is with round branch thorns, the other is with flat branch thorns. The G. sinensis with round branch thorns did not grow well and almost all plants had disease symptoms. The samples were collected on October, 2021 and deposited in Plant Disease Laboratory of Tianjin Agricultural University under accession no. PATAU211018. The disease symptoms consisted of foliage wilt (Figure 1A), plant drying and vascular tissue discoloration (Figure 1B). The stem sections from different plants were surface-disinfested in 0.6% NaClO, wiped with 75% ethanol and rinsed with sterile water. Thirty tissue samples were placed on Potato Dextrose Agar (PDA) medium and cultured at 28℃ for 7 days (Uppala et al. 2013). Thirty fungal isolates with the same morphological characteristics were obtained from the samples. Five representative isolates (PATAU211018-05, PATAU211018-07, PATAU211018-10, PATAU211018-12 and PATAU211018-21) were collected and purified using the single-spore method (Li et al. 2022). Colonies of the five isolates on PDA grew in a circular shape and showed abundant white densely fluffy aerial mycelium (Figure 1C). Morphological characteristics included septate and hyaline hyphae, long cylindrical monophialides (Figure 1D), macroconidia (Figure 1E) and microconidia (Figure 1F). Macroconidia were falcate, 2-5-septate, hyaline, 18-40 × 4-6 µm (n = 50). Microconidia were hyaline, oblong, 0-1-septate, 5-14 × 2-6 µm (n = 50). These morphological characteristics were consistent with the description of Fusarium solani. (Chitrampalam et al. 2018). PATAU211018-12 was randomly chosen for molecular analysis as the representative isolate given the similarity of these isolates. For further identification, the genomic DNA of isolate PATAU211018-12 was extracted. The fragments of internal transcribed spacer (ITS), translation elongation factor 1α (EF1α) gene and RNA polymerase II subunit (RPB2) were amplified and sequenced (O'Donnell et al. 2008; Carbone et al. 1999). The sequences of ITS, EF1α, and RPB2 of PATAU211018-12 were deposited in GenBank under the accession no. of OP735578, ON630412 and OP746032, respectively. Phylogenetic trees were constructed in MAGA X (Kumar et al. 2018) using the neighbor-joining (NJ) method based on the concatenated sequences of ITS, EF1α, and RPB2 (Figure 2). The isolate (PATAU211018-12) grouped with F. solani (JS-169) with a bootstrap value of 100 in the phylogenetic tree. The morphology and multi-gene phylogenetic analysis indicated that the new isolate is F. solani. Pathogenicity tests were carried out on one-year-old G. sinensis seedlings with round branch thorns (n=6). The F. solani isolate PATAU211018-12 was cultured in Potato Dextrose Broth (PDB) at 28°C on a shaker at 150 rpm for 5 days. Mycelia were filtered through four layers of sterilized lens paper and the conidia were obtained for pathogenicity tests. G. sinensis was infected by F. solani through root soaking method. The roots were inoculated by dipping in conidial suspension with the concentration of 107 conidia/mL for 30 minutes. Control plants (n=6) were treated with distilled water. Plants were in pots indoors at 25℃. At 20 days after inoculation, the leaves of inoculated plants were chlorotic and wilted (Figure 1G), symptoms similar to those observed in the park. In contrast, the leaves of control plants were symptomless (Figure 1H). The pathogenicity assay was repeated three times. The fungal isolate was re-isolated from the disease tissues and verified as F. solani based on morphology and molecular character (ITS, EF1α and RPB2). F. solani has been reported as pathogens on many plants, such as Eriobotrya japonica (Wu et al. 2021), Fragaria × ananassa (Pastrana et al. 2014), Gastrodia elata (Li et al. 2022) and Hedysarum boreale (Uppala et al. 2013). To our knowledge, this is the first report of F. solani causing disease on G. sinensis in China. Identification of F. solani as a disease agent in G. sinensis will assist in disease management for this important tree crop.

Oxidative stress, DNA damage, and gene expression induced by flufiprole enantiomers in the earthworms (Eisenia fetida).

To evaluate flufiprole enantiomers ecotoxicology and early warning to earthworms in the soil, the effect of flufiprole enantiomers on the activity of antioxidative enzymes (superoxide dismutase, SOD; catalase, CAT; peroxidase, POD), malondialdehyde (MDA) content, DNA damage and expression level of target genes (SOD, TCTP, l-rRNA, and HSP90) have been investigated. Compared to the controls, the activities of SOD, CAT, POD, and MDA content were first inhibited and then stimulated by all concentrations of flufiprole enantiomers in 28 days. The olive tail moment (OTM) value was maximum on the 14th day, then decreased gradually, and the higher the concentration, the slower the decrease. The expression level of the SOD and TCTP genes increased first and then decreased. In conclusion, the toxicity of flufiprole enantiomers to earthworms is: R-(+)- flufiprole >Rac-(±)- flufiprole >S-(-)- flufiprole. The SOD could be the key biomarker for monitoring the risk of flufiprole enantiomers.

Enantiomeric profiling of mefentrifluconazole in watermelon across China: Enantiochemistry, environmental fate, storage stability, and comparative dietary risk assessment.

Elucidating the enantiomeric chemistry and enantioselective fate of the novel chiral triazole fungicide mefentrifluconazole is of vital importance for agroecosystem safety and human health. The absolute configuration of mefentrifluconazole was identified firstly as S-(+)-mefentrifluconazole and R-(-)-mefentrifluconazole on a cellulose tris(3-chloro-4-methylphenylcarbamate) chiral phase. A baseline resolution (Rs, 2.51), favorable retention (RT ≤ 2.24 min), and high sensitivity (LOQ, 0.5 µg/kg) of enantiomer pair were achieved by reversed-phase liquid chromatography tandem mass spectrometry combined with a 3D response surface strategy. Nationwide field trials were undertaken to clarify the enantiomer occurrence, enantioselective dissipation, terminal concentrations, and storage stability of S-mefentrifluconazole and R-mefentrifluconazole in watermelon across China. The original deposition of the sum of enantiomer pair was estimated to be 14.4-163.7 µg/kg, and terminally decreased to < LOQ-59.3 µg/kg 10 days after foliage application. S-mefentrifluconazole preferentially degraded (T1/2, 3.3-6.0 days), resulting in the relative enrichment of R-mefentrifluconazole (T1/2, 3.9-6.6 days) in watermelon. A probabilistic model is recommended for the dietary risk assessment, although both acute (%ARfD, 0.435-22.188%) and chronic (%ADI, 1.697-9.658%) risks are acceptable for associated population. The long-term exposures should be continuously emphasized given the increasing applications and persistent fate of mefentrifluconazole, especially for urban children.

Stereoselective bioactivity, acute toxicity and dissipation in typical paddy soils of the chiral fungicide propiconazole.

Propiconazole is a widely used systemic agricultural triazole fungicide with two chiral centers. In the present study, systemic assessments of propiconazole stereoisomers are reported for the first time, including absolute configuration, stereoselective bioactivity toward pathogens (Ustilaginoidea virens, Magnaporthe oryzae, Fusarium moniliforme, Thanatephorus cucumeris, and Rhizoctonia solani), and stereoselective acute toxicity toward aquatic organisms (Scenedesmus obliquus, and Daphnia magna). Moreover, the stereoselective dissipation of propiconazole in three types of paddy soil under laboratory-controlled conditions (aerobic, anaerobic and sterile) was investigated. The degree of bioactivity and acute toxicity of the propiconazole stereoisomers differed depending on the type of target pathogens and non-target organisms. There were 2.43-23.47 and 1.48-2.13 fold differences between the best and worst stereoisomer in bioactivity and toxicity, respectively. Under aerobic conditions, (2S,4S)-propiconazole and (2S,4R)-propiconazole were preferentially degraded in the three types of soils. However, no significant stereoselectivity was observed under anaerobic and sterile conditions. Propiconazole was configurationally stable throughout the study. In comprehensive consideration of bioactivity, toxicity and environmental behavior, using stereoisomer mixture rather than pure stereoisomer may help to control more species of disease in practical application, and the stereoselectivity should be taken into consideration in risk assessment.

The fate and enantioselective behavior of zoxamide during wine-making process.

The fate of zoxamide and its enantiomers were evaluated in detail during wine-making process. The enantiomers of zoxamide were separated and determined by ultra-high-performance liquid chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) after each processing procedure including washing, peeling, fermentation and clarification. Significant enantioselectivity was observed in all three treatments with the half-lives of R-zoxamide and S-zoxamide estimated to be 45.6 and 52.9 h in Group A, 45.0 and 52.1 h in Group B, 56.8 and 70.7 h in Group C, respectively. The results indicated that R-zoxamide degraded faster than S-zoxamide during the fermentation process. The processing factors (PFs) of each procedure were generally less than 1, and the PF of the overall process ranged from 0.019 to 0.051, which indicated that the whole process can reduce the zoxamide residue in red and white wine obviously. The results could help facilitate more accurate risk assessments of zoxamide during wine-making process.

Stereoselective Analysis and Dissipation of Propiconazole in Wheat, Grapes, and Soil by Supercritical Fluid Chromatography-Tandem Mass Spectrometry.

An efficient and sensitive chiral analytical method was established for the determination of propiconazole stereoisomers by supercritical fluid chromatography-tandem mass spectrometry (SFC-MS/MS). Stereoisomeric separation was performed on a Chiralpak AD-3 column with CO2/ethanol (93:7) as the mobile phase. The four propiconazole stereoisomers were well separated in 4.7 min with resolutions above 2.0. The specificity, linearity, matrix effects, accuracy, precision, and stability of the developed method were evaluated. The stereoselective dissipation of propiconazole in wheat straw, grape, and soil samples was investigated according to the proposed method. The results indicated that significant stereoselective degradation occurred in wheat straw and grapes, with preferential degradation of (-)-propiconazole A and (+)-propiconazole B in wheat straw and the opposite case in grapes. No enantioselectivity was observed in soil, although diastereoisomer A degraded more rapidly than diastereoisomer B. These results could contribute to a more accurate assessment of the environmental risk and food safety of propiconazole.

Simultaneous enantioselective determination of phenylpyrazole insecticide flufiprole and its chiral metabolite in paddy field ecosystem by ultra-high performance liquid chromatography/tandem mass spectrometry.

A novel and sensitive ultra-high performance liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) method was developed and validated for simultaneous enantioselective determination of flufiprole and its hydrolysis metabolite in paddy field ecosystem. The separation and determination were performed using reversed-phase chromatography on a novel cellulose chiral stationary phase, a Lux Cellulose-4 (150 mm × 2.0 mm) column, under isocratic conditions at 0.25 mL/min flow rate. The effects of other four different polysaccharide-based chiral stationary phases (CSPs) on the separation and simultaneous enantioseparation of the two target compounds were also evaluated. The elution orders of the eluting enantiomers were identified by an optical rotation detector. Modified QuEChERS (acronym for Quick, Easy, Cheap, Effective, Rugged and Safe) method and solid-phase extraction (SPE) were used for the enrichment and cleanup of paddy water, rice straw, brown rice and paddy soil samples, respectively. Parameters including the matrix effect, linearity, precision, accuracy and stability were evaluated. Under the optimal conditions, the mean recoveries for all enantiomers from the above four sample matrix were ranged from 83.6% to 107%, with relative standard deviations (RSD) in the range of 1.0-5.8%. Coefficients of determination R(2)≥0.998 were achieved for each enantiomer in paddy water, rice straw, brown rice and paddy soil matrix calibration curves within the range of 5-500 µg/kg. The limits of quantification (LOQ) for all stereoisomers in the above four matrices were all below 2.0 µg/kg. The methodology was successfully applied for simultaneously enantioselective analysis of flufiprole enantiomers and their chiral metabolite in the real samples, indicating its efficacy in investigating the environmental stereochemistry of flufiprole in paddy field ecosystem.

Green and sensitive supercritical fluid chromatographic-tandem mass spectrometric method for the separation and determination of flutriafol enantiomers in vegetables, fruits, and soil.

A green and sensitive chiral analytical method was developed to determine flutriafol enantiomers in vegetables (tomato, cucumber), fruits (apple, grape), and soil by supercritical fluid chromatography-tandem mass spectrometry. The enantioseparation was performed within 3.50 min using Chiralpak IA-3 column with CO2/methanol (88:12, v/v) as the mobile phase at a 2.2 mL/min flow rate. The postcolumn compensation technology provided with 1% formic acid/methanol greatly improved the ionization efficiency of mass spectrometry. Column temperature, auto back pressure regulator pressure, and flow rate of compensation solvent were optimized to 30 °C, 2200 psi, and 0.1 mL/min, respectively. The simple and fast QuEChERS pretreatment method was adopted. Mean recoveries for flutriafol enantiomers were 77.2-98.9% with RSDs ≤ 9.6% in all matrices. The limits of quantification ranged from 0.41 to 1.18 µg/kg. Well-applied to analyze authentic samples, the developed method could act as a versatile strategy for the analysis of flutriafol enantiomers in food and environmental matrices.

Comparison of different cleanup procedures for oil crops based on the development of a trace analytical method for the determination of pyraclostrobin and epoxiconazole.

The effects of different cleanup procedures in removing high-molecular-mass lipids and natural colorants from oil-crop extracts, including dispersive solid-phase extraction, low-temperature precipitation and gel permeation chromatography, were studied. The pigment removal, lipid quantity, and matrix effects of the three cleanup methods were evaluated. Results indicated that the gel permeation chromatography method is the most effective way to compare the dispersive solid-phase extraction and low-temperature precipitation. Pyraclostrobin and epoxiconazole applied extensively in oil-crop production were selected as typical pesticides to study and a trace analytical method was developed by gel permeation chromatography and ultra high performance liquid chromatography with tandem mass spectrometry. Average recoveries of the target pesticides at three levels (10, 50, and 100 µg/kg) were in the range of 74.7-96.8% with relative standard deviation values below 9.2%. The limits of detection did not exceed 0.46 µg/kg, whereas the limits of quantification were below 1.54 µg/kg and much lower than maximum residue limit in all matrices. This study may provide the essential data for optimizing the analytical method of pesticides in oil-crop samples.

Stereoselective separation and pharmacokinetic dissipation of the chiral neonicotinoid sulfoxaflor in soil by ultraperformance convergence chromatography/tandem mass spectrometry.

Ultraperformance convergence chromatography/tandem triple quadrupole mass spectrometry (UPC(2)-MS/MS) is a novel tool in separation science that combines the advantages of supercritical fluid chromatography with ultraperformance liquid chromatography/MS/MS technology. The use of nontoxic CO2 fluid and a postcolumn additive to complement MS/MS allows better control of analyte retention for chiral separation and high-sensitivity determination with different chiral stationary phases. This paper reports the stereoselective separation and determination of the chiral neonicotinoid sulfoxaflor in vegetables and soil by UPC(2)-MS/MS. Baseline resolution (Rs ≥ 1.56) of and high selectivity (LOQ ≤ 1.83 µg/kg) for the four stereoisomers were achieved by postcolumn addition of 1 % formic acid-methanol to a Chiralpak IA-3 using CO2/isopropanol/acetonitrile as the mobile phase at 40 °C, 2,500 psi, and for 6.5 min in electrospray ionization positive mode. Rearranged Van't Hoff equations afforded the thermodynamic parameters ΔH (ο) and ΔS (ο), which were analyzed to promote understanding of the enthalpy-driven separation of sulfoxaflor stereoisomers. The interday mean recovery, intraday repeatability, and interday reproducibility varied from 72.9 to 103.7%, from 1.8 to 9.2%, and from 3.1 to 9.4%, respectively. The proposed method was used to study the pharmacokinetic dissipation of sulfoxaflor stereoisomers in soil under greenhouse conditions. The estimated half-life ranged from 5.59 to 6.03 d, and statistically nonsignificant enantioselective degradation was observed. This study not only demonstrates that the UPC(2)-MS/MS system is an efficient and sensitive method for sulfoxaflor stereoseparation, but also provides the first experimental evidence of the pharmacokinetic dissipation of sulfoxaflor stereoisomers in the environment.

A quick, easy, cheap, effective, rugged, and safe method for the simultaneous detection of four triazolone herbicides in cereals combined with ultrahigh performance liquid chromatography with tandem mass spectrometry.

This paper describes a novel, rapid, and sensitive analytical method for monitoring four triazolone herbicides in cereals (wheat, rice, corn, and soybean), using a quick, easy, cheap, effective, rugged, and safe sample extraction procedure followed by ultrahigh performance liquid chromatography coupled with tandem mass spectrometry. The four triazolone herbicides (amicarbazone, carfentrazone-ethyl, sulfentrazone, and thiencarbazone-methyl) were extracted using acidified acetonitrile (containing 1% v/v formic acid) and subsequently purified with octadecylsilane (C18 ) prior to sample analysis. Ultrahigh performance liquid chromatography coupled with tandem mass spectrometry was operated in positive and negative ionization switching mode. Amicarbazone and carfentrazone-ethyl were detected in the positive mode (ESI+), while sulfentrazone and thiencarbazone-methyl were detected in the negative mode (ESI-). All compounds were successfully separated in less than 3.0 min. Further optimization achieved desired recoveries ranging from 74.5 to 102.1% for all analytes with relative standard deviation values ≤17.2% in all tested matrices at three levels (10, 100, and 500 µg/kg). The limits of detection for all compounds were ≤2.3 µg/kg, and the limits of quantitation did not exceed 7.1 µg/kg. The developed method showed excellent linearity (R(2) ≥ 0.994) and was proven to be highly efficient and reliable for the routine monitoring of triazolone herbicides in cereals.

Stereoselective determination of a novel chiral insecticide, sulfoxaflor, in brown rice, cucumber and apple by normal-phase high-performance liquid chromatography.

An effective high-performance liquid chromatography method was developed for the stereoselective determination of a new sulfoximines insecticide, sulfoxaflor, in brown rice, cucumber and apple. Target compounds were extracted with acetonitrile and an aliquot cleaned with Cleanert PestiCarb/PSA (primary and secondary amine) cartridge. Five polysaccharide-based columns were investigated on the separation of sulfoxaflor stereoisomers and the best was achieved on a ChromegaChiral CCA column with n-hexane/ethanol/methanol (90:2:8, v/v/v) as mobile phase by UV detection at 220 nm at 20ºC. The resolutions of the four stereoisomers were 1.85, 1.54 and 3.08, and the elution order was identified by optical rotation and stereoisomers ratio. The mean recoveries of sulfoxaflor stereoisomers ranged from 77.1% to 99.3%, with relative standard deviations less than 8.9% at three concentration levels in all matrices. The limits of detection for all stereoisomers varied from 0.05 mg/kg to 0.07 mg/kg, while the limit of quantification did not exceed 0.22 mg/kg. The method was then successfully applied to determine the sulfoxaflor stereoisomers in authentic samples, confirming that it is convenient and reliable for stereoselective determination of sulfoxaflor stereoisomers in food.

Enantioselective separation and transformation of metalaxyl and its major metabolite metalaxyl acid in tomato and cucumber.

Many studies have shown the enantioselective transformation of metalaxyl in soil and animals, but little is known about the enantioselective biotransformation of metalaxyl in plants. In this study, a sensitive and convenient chiral liquid chromatography-tandem mass spectrometry method was developed for simultaneous measurement of the enantiomers of metalaxyl and its major metabolite, metalaxyl acid, in tomato and cucumber. Separation was by reversed-phase chromatography on a Chiralcel OD-RH column under isocratic conditions using acetonitrile-water (60/40, v/v) as mobile phase. The proposed method was successfully applied to investigate the possible enantioselective transformation of metalaxyl as well as the formation of metalaxyl acid in tomato and cucumber. In both vegetables, the (-)-R-enantiomer was preferentially degraded, resulting in relative enrichment of the (+)-S-enantiomer. Furthermore, formation of the metalaxyl acid enantiomers was also shown to be enantioselective, with the R-metalaxyl acid formed at a faster rate. This is the first evidence of enantioselective transformation of metalaxyl in vegetables, and the results should be considered in future environmental risk and food safety evaluations.

Enantioselective determination of the insecticide indoxacarb in cucumber and tomato by chiral liquid chromatography-tandem mass spectrometry.

A convenient and precise chiral method was developed and validated for measuring indoxacarb enantiomers in cucumber and tomato using liquid chromatography-tandem mass spectrometry (LC-MS/MS) with a reversed-phase Chiralpak AD-RH column. The target analytes were extracted by acetonitrile and then purified by solid phase extraction (SPE) using NH2 /Carb combined-cartridge. Parameters including the matrix effect, linearity, precision, accuracy, and stability were used. Then the proposed method was successfully applied to investigate the possible enantioselective degradation of rac-indoxacarb in cucumber and tomato under open conditions. The results indicated that the degradation of indoxacarb enantiomers followed first-order kinetics in cucumber and tomato. The half-lives of (+)-S-indoxacarb in cucumber and tomato were 3.0 and 5.9 days, respectively; while the (-)-R-indoxacarb were 7.3 and 12.2 days, respectively. The data of the half-lives showed that (+)-S-indoxacarb was preferentially degraded in cucumber and tomato. Moreover, indoxacarb degraded faster in cucumber than in tomato.

Simultaneous enantioselective determination of triazole fungicide difenoconazole and its main chiral metabolite in vegetables and soil by normal-phase high-performance liquid chromatography.

Herein is reported, for the first time, a simple and highly sensitive chiral high-performance liquid chromatography (HPLC) method for the simultaneous quantitative determination of difenoconazole stereoisomers and their hydroxylated metabolite difenoconazole alcohol (CGA-205375) enantiomers in vegetables and soil matrix. The separation of difenoconazole and CGA-205375 including their simultaneous enantioseparation was studied using four different polysaccharide-type chiral stationary phases (CSPs) in combination with n-hexane-polar organic alcohols mobile phase. Chiralcel OJ consisting of 25 % of cellulose tris(4-methylbenzoate) coated on wide-pore polysaccharide silica gel exhibited higher resolving ability compared to cellulose tris(3,5-dimethylphenylcarbamate) (Chiralcel OD) as well as to its similar amylose derivative (Chiralpak AD) CSPs for this particular set of chiral analytes. Baseline separation and simultaneous enantioseparation of difenoconazole and its metabolite CGA-205375 could be achieved under optimized separation conditions. Based on the established HPLC method, enantioselective analysis method for this fungicide and its main chiral metabolite in vegetables and soil matrix were developed and validated. Parameters including the matrix effect, linearity, precision, accuracy, and stability were evaluated. Under the optimal conditions, the mean recoveries from cucumber, tomato, and soil matrix ranged from 81.65 to 94.52 %, with relative standard deviations in the range of 1.05-8.32 % for all stereoisomers. Coefficients of determination R(2) ≥ 0.998 were achieved for each enantiomer in the cucumber, tomato and soil matrix calibration curves within the range of 0.5-50 µg mL(-1). The limits of quantification for all enantiomers in three matrices were all below 0.1 µg mL(-1). The methodology was successfully applied for simultaneous enantioselective analysis of difenoconazole stereoisomers and their metabolite in the real samples, indicating its efficacy in investigating the environmental stereochemistry of difenoconazole in food and environmental matrix.