Dissipation and safety evaluation of novaluron, pyriproxyfen, thiacloprid and tolfenpyrad residues in the citrus-field ecosystem

Integrating processing factors and large-scale cabbage cultivation to understand the fate tendency and health risks of tolfenpyrad using deterministic and probabilistic models

Understanding the negative effects of agrochemicals on the environment and human health is indispensable for achieving green agriculture. In this study, the optimized UHPLC-MS/MS method achieved a highly sensitive quantification of tolfenpyrad in cabbage within 4.04 min. The occurrence, dissipation, and concentration variation of tolfenpyrad were reflected by the initial deposition of 0.250-2.045 mg/kg, half-lives (T1/2) of 2.4-10.2 d, and terminal magnitudes within 1.134 mg/kg. Furthermore, the fates of tolfenpyrad during processing were elucidated, with processing factors (Pfs) of 0.561-1.282. Among the different processing procedures, soaking in tap water (25 °C) for 5 min removed 43.9 % of tolfenpyrad and was recommended for initial processing. The multidimensional dietary assessment revealed unacceptable levels of short-term risks from tolfenpyrad in children (%ARfD, 160.519-688.725 %) using deterministic and probabilistic models. Fortunately, the risks were minimized to negligible levels (%ARfD, 69.665-98.719 %) through washing and heat processing. Despite the long-term risks (%ADI, 3.310-9.371 %) being within the safety threshold, the cumulative effect of tolfenpyrad in multiple crops (%ADIt, 46.407-121.472 %) and regional differences (p < 0.05) should be emphasized. Our investigation shed light on the fates of tolfenpyrad in raw to processed cabbage with the aim of achieving sustainable agriculture and alerting to the agricultural pollutant's danger to children.

Study of dissipation dynamics and persistent toxicity of selected insecticides in chilli using LCMSMS

Chilli, a globally cultivated and consumed crop is significantly impacted by Thrips parvispinus. The reliance on pesticides could result in residue contamination, adversely affecting quality, leading to export rejections and health risks to consumers. This study evaluated the bioefficacy and persistent toxicity of fipronil and tolfenpyrad against thrips in chilli, and persistence of their residues. Tolfenpyrad demonstrated higher field efficacy (60.94 to 78.53%) against thrips compared to fipronil (37.61 to 58.07%). Residue analysis was performed in leaves and green chilli fruits using LC-MS/MS. Fipronil's efficacy decreased after 5 to 7 days of application, but both fipronil and tolfenpyrad residues remained for 20 and 30 days, respectively. In contrast, the residues in leaves caused persistent toxicity to thrips, causing about 50% mortality until 10 to 15 days in tolfenpyrad treatment. In green chilli, residues of tolfenpyrad and fipronil persisted for up to 40 and 25 days, necessitating pre-harvest intervals of 3.17 and 19.39 to 30.65 days, respectively, but with no dietary risk to consumers. Tolfenpyrad exhibited superior efficacy against T. parvispinus compared to fipronil, with a longer duration of effectiveness in leaves and quicker residue dissipation in chilli fruits and a short pre-harvest interval, supporting its use in Integrated Pest Management.

Standardization of an analytical technique for determination of pesticide residues in fresh and processed button mushroom Agaricus bisporus (Lange) Imbach

An efficient modified QuEChERS procedure was established for the simultaneous determination of 37 pesticide residues in fresh and processed edible button mushroom by employing GC/ GC-MS and LC-MS/MS. The effectiveness, reliability and accuracy of the method were assessed through validation parameters such as linearity, LOD, LOQ, precision, accuracy, uncertainty, and matrix effect. The linearity calibration for all the selected pesticides at standard concentrations (0.003, 0.01, 0.025, 0.05, 0.075, and 0.1 µg mL- 1) obtained were ≥ 0.970 in both GC and LC-MS/MS. The LOD and LOQ values were 0.003 and 0.01 µg g- 1, respectively. The recoveries obtained in the spiking level of 0.01-0.1 µg g- 1 were in the acceptable range (71.69 to 117.90%) with RSD less than 20%. Matrix effect and uncertainty for all target compounds were in the acceptable range. Monitoring of edible button mushroom samples collected from market revealed the presence of cypermethrin residues in four out of 25 fresh button mushroom samples and no detectable residues were found in processed mushroom products tested. Dietary risk assessement was calculated to the detected cypermethrin in the fresh button mushroom samples and RQ value obtained was <1, where risk is acceptable.

Quality and Safety in Asparagus Cultivation: A Three-Year Case Study Comparing Standardized Agricultural Bases and Small-Scale Farmers

To investigate the quality and safety difference between agricultural standardization bases and small-scale farmers, we carried out a three-year investigation of asparagus from seven production sites of different sizes in Pinghu city, Zhejiang Province, China, from 2021 to 2023. We documented trace elements (Fe, Zn, Mn, and Cu), quality indicators (vitamin B1, vitamin B2, vitamin C, total sugar, and proteins), and pesticide residues. The evaluation indicated that the quality of asparagus in standardization bases 1-4 was higher than that in small farmer sites 5-7. The detection rate of pesticides in asparagus was 23.81% (15/63), with a low concentration range of 0.001-0.130 mg mL-1. Low pesticide levels reflect Pinghu's effective green pest control measures. Results showed that the quality and safety of asparagus at the standardization bases are superior to those at small-scale farmer sites, and our findings may inform better management practices for both large-scale and small-scale asparagus farmers.

Combination of biotransformation and metabolomics reveals tolfenpyrad-induced hepatocytotoxicity

Tolfenpyrad (TFP) is an extensively used pesticide that inevitably leads to human exposure to both TFP and its transformation product residues. However, the biotransformation of TFP in humans has not been elucidated, and the toxicity of TFP along with its biotransformation products remains largely unknown. In this study, the biotransformation process of TFP was investigated using human liver microsomes and human hepatic cells. Endogenous metabolic changes in the cells were studied to investigate the hepatocytotoxicity of TFP at environmentally relevant concentrations. Fourteen phase I biotransformation products and four phase II TFP products were characterized, among which twelve products were identified for the first time. The oxidative product tolfenpyrad-benzoic acid (PT-CA) was particularly abundant and stable. Further hepatotoxicity assessments and metabolic studies demonstrated comparable metabolic profiles for TFP and PT-CA in HepG2 cells, with both significantly disrupting purine and glutathione metabolism. These processes are closely associated with oxidative stress, mitochondrial damage, and cell death. Our results provide novel perspectives on the biotransformation, metabolism, and hepatotoxicity of TFP, thereby highlighting the non-negligible toxicity of its crucial biotransformation product PT-CA in environmental risk assessments.

Exploring the dynamic behaviors of five pesticides in lettuce: Implications for consumer health through field and modeling experiments

Lettuce, a globally consumed nutritious vegetable, is often linked to concerns regarding pesticide residues. To address this issue, we conducted field trials and utilized dynamiCROP modeling to examine the uptake, distribution, translocation, and dissipation of five pesticides (λ-cyhalothrin, difenoconazole, acetamiprid, dimethomorph, and β-cypermethrin) commonly detected in lettuce. At harvest, pesticides residues were below the maximum residue limits (MRLs) at 0.05, 0.39, 0.047, 0.72, and 0.072 mg kg-1, respectively. Simulation results elucidated distinct behaviors of the pesticides following application to lettuce foliage across various compartments. However, all pesticides exhibited a common dissipation trend, initially stabilizing or increasing before gradually declining. For all five pesticides, the largest contribution of residues on lettuce leaves came from the leaf surface during the early period after application, and from the soil in the long term. Health risk assessments indicated negligible risks associated with consuming lettuce containing these pesticides, both in the short and long term.

Rational design of a dual-mode fluorescent probe for portable detection of pyriproxyfen in the environment and food

The development of a fluorescent probe for pyriproxyfen (PPF) is crucial due to its potential threat to human health. However, the chemical inertness and low solubility of PPF present significant challenges for the detection of PPF in aqueous solutions using fluorescent probes. Herein, we have originally proposed a complex based on 2-(4-(dimethylamino)phenyl)-3-hydroxy-6,7-dimethoxy-4 H-chromen-4-one (HOF) and serum albumin (SA) as a dual-mode fluorescent probe, HOF@SA. This probe utilizes an indicator displacement assay (IDA) to release the dye HOF from the probe at low PPF concentrations (< 10 µM) and embeds the free dye HOF into the micelle of PPF at high concentrations (> 10 µM). This results in dual-mode fluorescent response characteristics for PPF: a turn-off response at low concentrations and a ratiometric response at high concentrations. An investigation of sensing behavior of HOF@SA for PPF detection exhibits rapid response (< 60 s), high sensitivity (LOD ∼4.7 ppb), high selectivity, and excellent visual detection capability (from cyan to yellow). Moreover, with the aid of a portable device, this method enables to analyze PPF in environmental and food samples. These results promote the advancement of a fluorescent probe approach for PPF analysis in environment and food.

Advances on multiclass pesticide residue determination in citrus fruits and citrus-derived products - A critical review

The application of agrochemicals in citrus fruits is widely used to improve the quality of crops, increase production yields, and prolong post-harvest life. However, these substances are potentially toxic for humans and the ecosystem due to their widespread use, high stability, and bioaccumulation. Conventional techniques for determining pesticide residues in citrus fruits are chromatographic methods coupled with different detectors. However, in recent years, the need for analytical strategies that are less polluting for the environment has encouraged the appearance of new alternatives, such as sensors and biosensors, which allow selective and sensitive detection of pesticide residues in real time. A comprehensive overview of the analytical platforms used to determine pesticide residues in citrus fruits and citrus-derived products is presented herein. The review focuses on the evolution of these methods since 2015, their limitations, and possible future perspectives for improving pesticide residue determination and reducing environmental contamination.

Occurrence, dissipation and processing factors of multi-pesticides in goji berry

As medicine and food homology substance, goji berry is consumed worldwide in the form of fresh, dried and juice; however, pesticide residues have become one of the problems that essentially threaten its quality during cultivation and processing. In this study, a total of 75 dried goji berries were sampled from markets across China, and for the determination of 62 analytes, 28 pesticides were identified. Nine pesticides with high detectable rates and residual levels were selected for folia spraying, and their half-lives were found to range from 1.04 to 2.21 d. The processing factors (PFs) of juice were between 0.25 and 1.02, and this was mainly related with their octanol-water partition coefficient (logKow values). Washing could reduce pesticides residues to varying degrees with the removal rates between 17.00% and 74.05%. Sun drying with higher PF values in the range of 0.61-5.91 exhibited more obvious enrichment effect compared to oven drying. Commercial goji berry had cumulative chronic dietary risks with the hazard index (HI) values of 1.61%-4.97%. Its acute risk quotients (HQas) for consumers were 543.32%-585.92% and were mainly due to insecticides. These results provide important references for rationalizing pesticide application during goji berry cultivation and for the improvement of process to ensure food safety.

The fate and potential hazards of chlorfenapyr and one metabolite tralopyril in cabbages: A comprehensive investigation

The potential hazards of chlorfenapyr warrant attention owing to its widespread application on vegetables. A comprehensive investigation of the fate of chlorfenapyr in the ecosystem is imperative. This paper presents a method for detecting chlorfenapyr and tralopyril in cabbages, which exhibits good linearity (determination coefficients > 0.99) and satisfactory recoveries (82.50 %-108.03 %). Chlorfenapyr residues in cabbages demonstrate a positive correlation with its application dose and time. Tralopyril can inhibit the dissipation of chlorfenapyr, as evidenced by the half-lives of 5.67-11.14 d (chlorfenapyr) and 6.91-14.77 d (total chlorfenapyr). The results of terminal residues (<2.0 mg/kg) and dietary risk assessment (<100 %) suggest preharvest intervals of 14 d (greenhouse) and 10 d (open-field). Additionally, the uptake of chlorfenapyr in cabbages is limited (translocation factor < 1), while the downward translocation predominantly occurs through phloem transport. The findings provide valuable insights for understanding the fate and potential risks of chlorfenapyr in cabbages.

Insight into the uptake, translocation, metabolism, dissipation and risk assessment of tolfenpyrad in romaine and edible amaranth grown in hydroponic conditions

Tolfenpyrad is an alternative to highly water-soluble and ecotoxic insecticides that is widely used in China. It is absorbed and accumulates in vegetables, leading to potential public-health hazards. A systematic study of the fate of tolfenpyrad is necessary for proper application and food safety. Herein, we report on the uptake, translocation, metabolism, dissipation, and dietary risks of tolfenpyrad in hydroponic romaine and amaranth plants. Roots easily absorbed and accumulated tolfenpyrad, although transport was moderate in both vegetables. Basipetal translocation of tolfenpyrad occurred in romaine but not in edible amaranth, owing to differences in specific transport behaviour in each case. Six metabolites and three pathways were proposed. Tolfenpyrad affected antioxidant enzyme activities in different parts of the two vegetables. Tolfenpyrad dissipation proceeded swiftly, entailing an acceptable risk to humans. Our results provide information on the distribution and transport of tolfenpyrad, as well as on the safety in using it on vegetables.

Dissipation behaviours, residues, and health risk of six herbicides in sugar beets under field conditions

This study established a residue detection method based on the QuEChERS pre-treatment method and combined it with high-performance liquid chromatography-tandem mass spectrometry to test six herbicides (metamitron, clopyralid, desmedipham, phenmedipham, ethofumesate, and haloxyfop-p-methyl) in sugar beet plants, soil, and roots. The degradation dynamics and terminal residues of each herbicide in sugar beets were analysed. Finally, the dietary risks of various herbicides in sugar beets were evaluated based on the dietary structure of Chinese people, and the risk quotient values were below 100%. Using this detection method, all reagents exhibited good linearity (0.9724 ≤ R2 ≤ 0.9998), The limit of quantification (LOQ) ranged from 0.01 to 0.05 mg/L, the matrix effect ranged from -1.2% to -50%, the addition recovery rate ranged from 77.00% to 103.48%, and the relative standard deviation ranged from 1.61% to 16.17%; therefore, all indicators of this method met the residue detection standards. Under field conditions, the half-lives (t1/2) ranged about 0.65 ∼ 2.96 d and 0.38 ∼ 27.59 d in sugar beet plants and soil, respectively. All herbicides were easily degraded in sugar beet plants and soil (t1/2 < 30 d). The terminal residue amounts in the beet plants, soil, and roots ranged from < LOQ to 0.243 mg/kg. The dietary risk assessment of each pesticide was conducted based on the residual median of the terminal residues and the highest residual values on the edible part of the beetroot. The chronic exposure risk quotient (RQc) and acute exposure risk quotient (RQa) values were < 100%, indicating that the residue of each pesticide in beetroot posed low risks to consumers in China at the recommended dosage.

Thiamethoxam dynamics in pepper plants: Deciphering deposition and dissipation pattern across diverse planting modes and regions

To reduce the application dosage of thiamethoxam (TMX), we investigated the deposition and dissipation patterns in a pepper-planted ecosystem under different planting modes across four regions in China, namely Hainan (HN), Zhejiang (ZJ), Anhui (AH) and Hebei (HB). This study focused on the deposition and dissipation of TMX at concentrations of 63.00, 47.25, 31.50, 23.63 and 15.75 g a.i.hm-2. As the application dose increased, the deposition amount of TMX initially increased in the plants and cultivated soil, showing obvious geographic differences in four cultivation areas. Surprisingly, the initial amount of TMX deposited the pepper-cultivated greenhouse of ZJ and AH was 1.1-2.1-fold and 1.0-3.6-fold higher than that in the open field system at the same application dose, respectively. In pepper leaves, stems, fruits and soil, the dissipation exhibited rapid growth and then slowed. However, the residual concentration showed an increasing trend, followed by a subsequent decrease in the pepper roots. In different planting regions, the dissipation rate of TMX followed the order HN > ZJ > AH > HB in pepper plants and cultivated soil. In comparison to the open field, the total TMX retention rate in greenhouse was higher, indicating overall greater persistence in the greenhouse conditions. These findings reveal the deposition and dissipation characteristics of TMX within the pepper-field ecosystem, offering a significant contribution to the risk assessment of pesticides.

Dissipation behavior and dietary risk assessment of cyclaniliprole and its metabolite in cabbage under field conditions

Cyclaniliprole, a novel diamide insecticide, can successfully control Spodoptera litura (Fabricius, 1775) in cabbage. Understanding the residual level of cyclaniliprole in crops and the risk related to its dietary intake is imperative for safe application. Here, we established a simplified, sensitive method for simultaneous analysis of cyclaniliprole and its metabolite NK-1375 (3-bromo-2-((2-bromo-4H-pyrazolo[1,5-d]pyrido[3,2-b]-[1,4]oxazin-4-ylidene)amino)-5-chloro-N-(1-cyclopropylethyl)benzamide) in cabbage by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to investigate their dissipation behavior and residual characteristics. Cyclaniliprole showed rapid dissipation in cabbage and had a half-life of 1.8-2.7 days. The highest residue of total cyclaniliprole (sum of cyclaniliprole and NK-1375) in cabbage from different pre-harvest intervals (3 and 5 days) was 0.25 mg/kg. Our results confirmed the generally low dietary risk quotient of cyclaniliprole (0.243-1.036%) among different age and gender groups in China. Therefore, cyclaniliprole did not pose an unacceptable risk to consumers. This study contributes to setting cyclaniliprole maximum residue limit in cabbage by assessing its dissipation fate and food safety risks.

Dissipation kinetics, decontamination, consumer risk assessment and monitoring of flonicamid and imidacloprid residues in capsicum under open field and polyhouse condition

Liquid chromatography mass spectrometry (LC-MS)-based detection of flonicamid, imidacloprid and 6-chloronicotinic acid residues was validated and analysed in capsicum fruit, processed products and soil. The standard concentrations (0.0025 to 0.25 μg mL-1) of insecticides had a good linear curve (r2>0.99). Limit of detection and limit of quantification values were 0.0025 and 0.01 mg kg-1, respectively. The accuracy (80.53 to 100.33 %) of capsicum matrices and soil (89.41 to 100.52 %) and precision (RSD <10%) were established. Dissipation of imidacloprid (20 and 40 g a.i. ha-1) and flonicamid (75 and 150 g a.i. ha-1) at single (X) and double dose (2X) was studied under open field and polyhouse conditions. Under open field conditions, the flonicamid and imidacloprid residues persisted with half-life of 1.98, 2.90 days (X) and 2.80, 3.14 (2X) days, respectively. While under polyhouse conditions, the flonicamid and imidacloprid residues persisted with a half-life of 2.84, 3.66 (X) and 3.24, 3.97 (2X) days, respectively. The metabolite, 6-CNA, was not detected in any samples under open field and polyhouse condition. Among decontamination treatments, cooking in boiling water for 10 minutes reduced 78 to 81.60 percent of imidacloprid and flonicamid residues in both doses. The estimated dietary risk assessment of imidacloprid and flonicamid residues (RQ <1) indicated that the risk is within the acceptable limit. In farmgate capsicum samples, residues of flonicamid (7 samples) and imidacloprid (11 samples) were detected. Market samples of capsicum products (powder, flakes and sauce) were not detected with residues of selected insecticides.

Residue behaviors, degradation, processing factors, and risk assessment of pesticides in citrus from field to product processing

Pesticide residues in citrus may cause health risks in related juice products, and bring much uncertainty during the processing procedures. In this study, based on the dispersive solid-phase extraction (d-SPE) and UPLC-MS/MS, the residual levels of ten analytes in citrus and its processed products were monitored. The results showed that dissipation of the pesticides followed the first-order kinetics and the half-lives in citrus varied greatly, ranging from 6.36 to 63.0 days. The terminal residues of the five pesticides at harvest time were <0.01-0.302 and <0.01-0.124 mg/kg in raw citrus and citrus flesh, respectively, all of which were lower than the corresponding maximum residue limits (MRLs) of 0.5-1 mg/kg. In the processing experiments, the residues of ten analytes in sterilized juice, concentrated juice, and citrus essential oil were in the range of <0.01 to 0.442 mg/kg, <0.01 to 1.16 mg/kg, and <0.01 to 44.0 mg/kg, respectively, and the corresponding processing factors (PFs) were 0.127-1.00, 0.023-3.06, and 0.006-39.2. Particularly, in citrus essential oil, the PFs of etoxazole, fluazinam, lufenuron and spirotetramat-keto-hydroxy were 1.68-39.2, exhibiting obvious enrichment effects. By integrating the residue data of the field trials and the PFs, the acute and chronic dietary risks of the target pesticides in citrus juice were 0.031-1.83 % and 0.002-2.51 %, respectively, which were far lower than 100 %, demonstrating no unacceptable risk to human health. This work provides basic data for the establishment of the MRLs and dietary exposure risk assessment for processed citrus products.

Immunochromatographic test strip for quantitative and rapid detection of tolfenpyrad in food samples

In the study, a hapten was designed to preserve the molecular structure of tolfenpyrad while introducing a carboxyl group and was coupled with a carrier protein to synthesize an immunogen and coating antigen. A monoclonal antibody was fabricated against tolfenpyrad and its performance was assessed by indirect competitive enzyme-linked immunosorbent assay. Finally, we developed a colloidal gold nanoparticle immunochromatographic test strip (CGN-ICTS) for the detection of tolfenpyrad in kale, Chinese cabbage, and eggplant samples. The results shows that CGN-ICTS was sensitive, with calculated detection limits of 0.49 ng/g for kale and Chinese cabbage and 0.99 ng/g for eggplant. Subsequently, CGN-ICTS and LC-MS were used to analyze the tolfenpyrad-spiked samples. The recovery rate of the CGN-ICTS for kale samples was 97.1-103.0%, for Chinese cabbage samples was 93.7-103.4%, and for eggplant samples was 92.7-105.7%. Recovery rates were similar between CGN-ICTS and LC-MS. Therefore, CGN-ICTS can be used to quickly screen tolfenpyrad residues in foods.

The metabolism and dissipation behavior of tolfenpyrad in tea: A comprehensive risk assessment from field to cup

The metabolites of pesticides usually require rational risk assessment. In the present study, the metabolites of tolfenpyrad (TFP) in tea plants were identified using UPLC-QToF/MS analysis, and the transfer of TFP and its metabolites from tea bushes to consumption was studied for a comprehensive risk assessment. Four metabolites, PT-CA, PT-OH, OH-T-CA, and CA-T-CA, were identified, and PT-CA and PT-OH were detected along with dissipation of the parent TFP under field conditions. During processing, 3.11-50.00 % of TFP was further eliminated. Both PT-CA and PT-OH presented a downward trend (7.97-57.89 %) during green tea processing but an upward trend (34.48-124.17 %) during black tea manufacturing. The leaching rate (LR) of PT-CA (63.04-101.03 %) from dry tea to infusion was much higher than that of TFP (3.06-6.14 %). As PT-OH was no longer detected in tea infusions after 1 d of TFP application, TFP and PT-CA were taken into account in the comprehensive risk assessment. The risk quotient (RQ) assessment indicated a negligible health risk, but PT-CA posed a greater potential risk than TFP to tea consumers. Therefore, this study provides guidance for rational TFP application and suggests the sum of TFP and PT-CA residues as the maximum residual limit (MRL) in tea.

Residue behavior of cyantraniliprole and its ecological effects on Procambarus clarkii associated with the rice-crayfish integrated system

BACKGROUND

Cyantraniliprole, a second-generation diamide insecticide, was recently introduced in China, where the rice-crayfish integrated system (RCIS) is practiced to control rice pest infestations. The aim of this study was to investigate the residue behavior of cyantraniliprole in RCIS and its potential ecological effects on nontarget Procambarus clarkii in order to recommend safe pesticide application strategies.

RESULTS

Cyantraniliprole dissipated in rice plants according to first-order kinetics, with an average half-life of 5.25 days and a dissipation rate of >95% over 28 days. The terminal cyantraniliprole residue levels in rice straw, paddy hull and brown rice were all within 0.2 mg kg^-1 , which is the China-recommended maximum residue limit. The tissues of P. clarkii accumulated and distributed cyantraniliprole in the descending order gill > hepatopancreas > intestine > muscles. Procambarus clarkii exposed to cyantraniliprole exhibited a moderate decrease in weight gain, specific growth rate and condition factor compared to the control group. Exposure of P. clarkii to cyantraniliprole caused histopathological alterations to the hepatopancreas, but the alterations were not statistically significant in the 60 g ai ha^-1 cyantraniliprole group when compared with the control group.

CONCLUSION

We suggest that 10% cyantraniliprole oil dispersion be sprayed twice at an interval of 14 days and dosage of 60 g ai ha^-1 during the growth stage of rice in RCIS. © 2023 Society of Chemical Industry.

Computer-Aided Prediction, Synthesis, and Characterization of Magnetic Molecularly Imprinted Polymers for the Extraction and Determination of Tolfenpyrad in Lettuce

Tolfenpyrad, a pyrazolamide insecticide, can be effectively used against pests resistant to carbamate and organophosphate insecticides. In this study, a molecular imprinted polymer using tolfenpyrad as a template molecule was synthesized. The type of functional monomer and the ratio of functional monomer to template were predicted by density function theory. Magnetic molecularly imprinted polymers (MMIPs) were synthesized using 2-vinylpyridine as a functional monomer in the presence of ethylene magnetite nanoparticles at a monomer/tolfenpyrad ratio of 7:1. The successful synthesis of MMIPs is confirmed by the results of the characterization analysis by scanning electron microscopy, nitrogen adsorption-desorption isotherms, Fourier transform infrared spectroscopy, X-ray diffractometer, thermogravimetric analyzer, and vibrational sample magnetometers. A pseudo-second-order kinetic model fit the adsorption of tolfenpyrad, and the kinetic data are in good agreement with the Freundlich isothermal model. The adsorption capacity of the polymer to the target analyte was 7.20 mg/g, indicating an excellent selective extraction capability. In addition, the adsorption capacity of the MMIPs is not significantly lost after several reuses. The MMIPs showed great analytical performance in tolfenpyrad-spiked lettuce samples, with acceptable accuracy (intra- and inter-day recoveries of 90.5-98.8%) and precision (intra- and inter-day relative standard deviations of 1.4-5.2%).

Effect of decontamination and processing on insecticide residues in grape (Muscat Hamburg)

Field and laboratory experiments were conducted to study the effect of simple decontamination methods and processing on imidacloprid, dimethoate, and emamectin benzoate residues in grapes and their processed products by liquid chromatography-mass spectrometry. Among the decontamination methods evaluated, washing with NaCl (2%) solution was effective for reducing imidacloprid (77.55%), dimethoate (83.27%), and emamectin benzoate (77.28%) residues in mature grapes. No metabolites (omethoate and 6-chloronicotinic acid) were detected in both decontamination and processing studies. The grapes were processed into various products, including fresh juice, squash, and raisin, following the standard effective steps for each product. Washing with NaCl (2%) solution for decontamination was included as an additional step in the standard protocol and resulted in substantial removal of surface residues of the selected insecticides. The processing factor calculated was less than one for all the products.

Characterization of Chitin Synthase A cDNA from Diaphorina citri (Hemiptera: Liviidae) and Its Response to Diflubenzuron

Diaphorina citri Kuwayama is the vector of HLB and one of the most common pests in citrus orchards in southern China. One of the most significant genes in D. citri's growth and development is the chitin synthase gene. In this study, the CHS gene (DcCHSA) of D. citri was cloned and analyzed by bioinformatics. According to RT-qPCR findings, DcCHSA was expressed at many growth processes of D. citri, with the greatest influence in the fifth-instar nymph. The molting failure rate and mortality of D. citri rose as DFB concentration increased in this research, as did the expression level of DcCHSA. Feeding on DcCHSA caused a large drop in target gene expression, affected nymph molting, caused failure or even death in freshly eclosion adults, increased mortality, and reduced the molting success rate over time. These findings showed that DcCHSA was involved in nymph to adult development and may aid in the identification of molecular targets for D. citri regulation. It provided new ideas for further control of D. citri.

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.

Systemic assessment of the chiral insecticide pyriproxyfen in a citrus nectar source system: Stereoselective degradation, biological effect and exposure risk

BACKGROUND

Balancing the safety and efficiency of chiral pesticides can help protect pollinators. We evaluated the stereoselective behavior, bioactivity, toxicity and exposure risk of the chiral insecticide pyriproxyfen in a citrus nectar system.

RESULTS

Density functional theory (DFT) and ultra-performance liquid chromatography tandem mass spectroscopy (UPLC-MS/MS) were applied for absolute configuration appraisal and chiral analysis validation, respectively. The recoveries ranged from 72.3% to 100.5% with an relative standard deviation (RSD) ranging from 1.2% to 9.7%. In a field trial, we determined insecticide half-lives in citrus leaves and flowers, which were 7.0 and 8.6 days for R-(+)-pyriproxyfen, and 11.7 and 14.7 days for S-(-)-pyriproxyfen, respectively. We found that the bioactivity of R-(+)-pyriproxyfen was 3.39 and 2.37 times higher than S-(-)-pyriproxyfen against Unaspis yanonensis and Diaphorina citri nymphs, respectively. S-(-)-pyriproxyfen had 3.8 times higher acute toxicity than R-(+)-pyriproxyfen on Apis mellifera L., and its exposure risk was moderate based on the hazard quotient.

CONCLUSION

The phenomenon of stereoselective degradation and biological effect demonstrated that the high-risk stereoisomer of S-(-)-pyriproxyfen degraded more slowly than R-(+)-pyriproxyfen, but R-(+)-pyriproxyfen with better efficiency for target. Therefore, an increased duration of R-(+)-pyriproxyfen activity on citrus was beneficial for efficacy. Our results could guide the scientific application and evaluation of chiral pesticides on nectar plants. © 2022 Society of Chemical Industry.

Method Validation, Residues and Dietary Risk Assessment for Procymidone in Green Onion and Garlic Plant

Procymidone is used as a preventive and curative fungicide to control fungal growth on edible crops and ornamental plants. It is one of the most frequently used pesticides and has a high detection rate, but its residue behaviors remain unclear in green onion and garlic plants (including garlic, garlic chive, and serpent garlic). In this study, the dissipation and terminal residues of procymidone in four matrices were investigated, along with the validation of the method and risk assessment. The analytical method for the target compound was developed using gas chromatography-tandem mass spectrometry (GC-MS/MS), which was preceded by a Florisil cleanup. The linearities of this proposed method for investigating procymidone in green onion, garlic, garlic chive, and serpent garlic were satisfied in the range from 0.010 to 2.5 mg/L with R2 > 0.9985. At the same time, the limits of quantification in the four matrices were 0.020 mg/kg, and the fortified recoveries of procymidone ranged from 86% to 104%, with relative standard deviations of 0.92% to 13%. The dissipation of procymidone in green onion and garlic chive followed first-order kinetics, while the half-lives were less than 8.35 days and 5.73 days, respectively. The terminal residue levels in garlic chive were much higher than those in green onion and serpent garlic because of morphological characteristics. The risk quotients of different Chinese consumer groups to procymidone in green onion, garlic chive, and serpent garlic were in the range from 5.79% to 25.07%, which is comparably acceptable. These data could provide valuable information on safe and reasonable use of procymidone in its increasing applications.

Multi-residue analysis, dissipation behavior, and final residues of four insecticides in supervised eggplant field

In this study, the residues of four insecticides, spirotetramat, flonicamid, thiamethoxam, and tolfenpyrad, and their metabolites, including spirotetramat-enol, spirotetramat-mono-hydroxy, spirotetramat-keto-hydroxy, spirotetramat-enol-glucoside, 4-trifluoromethylnicotinamide, 4-trifluoromethylnicotinic acid, N-(4-trifluoromethylnicotinoyl) glycine, and clothianidin, were assessed using a single analysis method. The samples were extracted by acetonitrile, then purified by dispersive solid phase extraction and quantified using high performance liquid chromatography tandem mass spectrometry. The average recovery rate of 12 target compounds was 73.5-103.7%, the relative standard deviation was 1.1-18.3%, and the limit of quantification was 0.01-0.05 mg/kg. The results showed good linearity (R² >0.99), meeting the requirements of the pesticide residue analysis. The dissipation half-lives of the four insecticides in eggplant were 3.4-14.5 days. After the last applications at 7 and 10 days, the final residues of the four insecticides in eggplant were <0.01-0.21, 0.085-0.26, <0.05-0.078, and <0.01-0.21 mg/kg, respectively. The dissipation and final residue results could provide a theoretical basis for the rational application of four insecticides in eggplant fields.HighlightsHPLC-MS/MS for simultaneous determination of four insecticides and their metabolites in eggplant fields.The dissipation dynamics and final residue of the target compounds in field eggplant were studied.Guidance for the safe use of four insecticides on eggplant.

Skeletal Ni electrode-catalyzed C-O cleavage of diaryl ethers entails direct elimination via benzyne intermediates

Diaryl ethers undergo electrocatalytic hydrogenolysis (ECH) over skeletal Ni cathodes in a mild, aqueous process that achieves direct C-O cleavage without initial benzene ring saturation. Mechanistic studies find that aryl phenyl ethers with a single para or meta functional group (methyl, methoxy, or hydroxy) are selectively cleaved to the substituted benzene and phenol, in contrast to recently reported homogeneous catalytic cleavage processes. Ortho positioning of substituents reverses this C-O bond selectivity, except for the 2-phenoxyphenol case. Together with isotope labeling and co-solvent studies, these results point to two distinct cleavage mechanisms: (a) dual-ring coordination and C-H activation, leading to vicinal elimination to form phenol and a surface-bound aryne intermediate which is then hydrogenated and released as the arene; and (b) surface binding in keto form by the phenolic ring of the hydroxy-substituted substrates, followed by direct displacement of the departing phenol. Notably, acetone inhibits the well-known reduction of phenol to cyclohexanol, affording control of product ring saturation. A byproduct of this work is the discovery that the ECH treatment completely defluorinates substrates bearing aromatic C-F and C-CF₃ groupings.

Biomass conversion holds promise as a more sustainable source of platform chemicals, but limitations in the ways in which lignin can be broken down is a current bottleneck. Here the authors report an electrocatalytic hydrogenolysis over skeletal Ni that cleaves diaryl ethers, chemically resistant moieties in both renewable carbon sources and persistent organic pollutants.

Dissipation and dietary risk assessment of carbendazim and epoxiconazole in citrus fruits in China

BACKGROUND

Carbendazim and epoxiconazole are widely applied to control anthracnose and sand bark fungal diseases in citrus. The residues of these two fungicides in citrus and their potential risk to consumers have generated much public concern. We therefore sought to investigate the dissipation, residue, and dietary risk assessment of carbendazim and epoxiconazole in citrus.

RESULTS

The dissipation kinetics and residue levels of carbendazim and epoxiconazole in citrus under field conditions were measured using dispersive solid-phase extraction and ultra-high-performance liquid chromatography-tandem mass spectrometry. The citrus samples were extracted with acetonitrile and purified by primary secondary amine sorbent. The mean recoveries of carbendazim and epoxiconazole ranged from 86.2 to 105.6% and relative standard deviations were ≤9.8%. The half-lives of carbendazim and epoxiconazole in whole citrus ranged from 2.0 to 18.0 days. Hazard quotient (HQ) and risk quotient (RQ) models were applied to whole citrus for dietary exposure risk assessment based on the terminal residue test. Hazard quotients ranged from 0.066 to 0.134% and RQs from 18.48 to 82.12%.

CONCLUSION

Carbendazim and epoxiconazole in citrus degraded rapidly following first-order kinetics models. The dietary risk of exposure to both carbendazim and epoxiconazole through citrus, based on HQ and RQ, was acceptable for human consumption. This study indicates scientifically validated maximum residue limits in citrus, which are currently lacking for epoxiconazole in China. © 2021 Society of Chemical Industry.

A simple, environmental-friendly and reliable d-SPE method using amino-containing metal-organic framework MIL-125-NH2 to determine pesticide residues in pomelo samples from different localities

A simple, environmentally-friendly and reliable method was developed to simultaneously monitor the residue of methyl 1-naphthalene acetate, parathion-methyl, fenitrothion, bromophos and phenthoate in pomelo by using dispersive solid-phase extraction technique (d-SPE). In this method, these target analytes were captured by MIL-125-NH₂ and detected by GC-MS/MS. The key parameters of d-SPE were optimized by the single factor experiment. Under the optimized conditions, a good determination coefficient (R² > 0.9922) and extraction recoveries (64.7-116.8%) are obtained. The limit of detections (0.03-1.07 ng/g) is lower than the MRLs in citrus fruits established by EU (10-15000 ng/g) and China (10-10000 ng/g). The precisions of intra-day and inter-day are 1.3-8.9% and 3.8-14.9%, respectively. In addition, the sorbent MIL-125-NH₂ is stable and can be reused at least eight times. These results prove the established method is efficient and reliable to detect the pesticide residues in pomelo.

Determination, residue analysis and risk assessment of thiacloprid and spirotetramat in cowpeas under field conditions

The dissipation and residue levels of thiacloprid, spirotetramat and its four metabolites residues in cowpeas were investigated under field conditions. The QuEChERS technique with high-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) was used to detect thiacloprid, spirotetramat and its four metabolites residues content in cowpeas. The recoveries were 81.3–95.1% at a spike level of 0.005–0.5 mg/kg, the relative standard deviations (RSDs) were 2.1–9.5%. The dissipation kinetics data showed that thiacloprid and spirotetramat in cowpeas were degraded with the half-lives of 1.14–1.54 days and 1.25–2.79 days. The terminal residues of thiacloprid and spirotetramat were 0.0255–0.4570 mg kg⁻¹ and 0.0314–0.3070 mg kg⁻¹ after application 2 times with a pre-harvest interval (PHI) of 3 days under the designed dosages. The chronic and acute dietary exposure assessment risk quotient (RQ) values of thiacloprid in cowpeas for different consumers were 2.44–4.41% and 8.72–15.78%, respectively, and those of spirotetramat were 1.03–1.87% and 0.18–0.32%, respectively, all of the RQ values were lower than 100%. The dietary risk of thiacloprid through cowpeas to consumers was higher than spirotetramat. The results from this study are important reference for Chinese governments to develop criteria for the safe and rational use of thiacloprid and spirotetramat, setting maximum residue levels (MRLs), monitoring the quality safety of agricultural products and protecting consumer health.

Residue, dissipation and dietary intake risk assessment of tolfenpyrad in four leafy green vegetables under greenhouse conditions

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A QuEChERS-GC–MS/MS method was used to detect tolfenpyrad in leafy green vegetables.

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Half-lives of tolfenpyrad were 2.0–6.8 d in greenhouse-grown leafy green vegetables.

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PHI of tolfenpyrad was suggested as 21 d in BCL and 28 d in BBL, SOL and LSL.

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The potential health risk of tolfenpyrad was acceptable in leafy green vegetables.

A novel and accurate analytical method for the determination of tolfenpyrad in four leafy green vegetables, Brassica bara L., Spinacia oleracea L., Lactuca sativa L. and Brassica chinensis L., was developed and applied to investigate the residue distribution and dietary risk under greenhouse conditions. The established approach was determined to be adequate, with recoveries of 79.2%–92.9% and relative standard deviations < 8%. Tolfenpyrad dissipated relatively rapidly in four leafy green vegetables. Terminal residues of tolfenpyrad were below 0.5 mg/kg (maximum residue limit for Brassica bara L. set by China) in leafy green vegetables collected 28 d after the last application. Due to risk quotient values < 100%, the residue levels of tolfenpyrad in leafy green vegetables collected 21 days after the last application were deemed safe for consumers. The results provide field data for the reasonable use and dietary risk assessment of tolfenpyrad in leafy green vegetables.

LC-MS/MS method for the simultaneous quantification of pyriproxyfen and bifenthrin and their dissipation kinetics under field conditions in chili and brinjal

Bifenthrin, a synthetic pyrethroid, and pyriproxyfen, a plant growth regulator, are used extensively in agriculture for controlling the different insect pests. The present study was undertaken to examine the dissipation behavior of a formulation with a combination of pyriproxyfen and bifenthrin on chili and brinjal under field conditions at four different locations. Dissipation study of combination of pyriproxyfen and bifenthrin revealed swift degradation in both crops with a half-life of 2.5-2.6 and 2.0-2.1 days in brinjal and chili, respectively. Also, a simple method for simultaneous quantification of pyriproxyfen and bifenthrin was developed and validated using modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) technique on liquid chromatography with tandem mass spectrometry (LC-MS/MS). Recovery of the method was found to be under an acceptable range of 90.0%-93.5% and 88.7%-94.3% in chili and 92.4%-96.6% and 97.4%-100.9% in brinjal for pyriproxyfen and bifenthrin, respectively. At harvest time, the terminal residues of bifenthrin and pyriproxyfen were below the maximum residue limits set by European Union in chili and brinjal, respectively, suggesting that the use of this pesticide formulation is safe and does not impose harmful effects on human health. PRACTICAL APPLICATION: In this paper, dissipation behavior of a pesticide formulation with a combination of pyriproxyfen and bifenthrin was undertaken under field conditions at four different locations on chili and brinjal in India. The simultaneous quantification of pyriproxyfen and bifenthrin using LC-MS/MS technique has been validated incorporating modified QuEChERS extraction method with limit of detection at 0.005 µg/g and limit of quantification at 0.01 µg/g, which is well below the EU-MRLs (European Union legislation Maximum Residue Level) of pyriproxyfen and bifenthrin in both chili and brinjal. Furthermore, dissipation kinetics of a formulation undertaken under field conditions at four different locations on chili and brinjal suggested that the terminal residues of both bifenthrin and pyriproxyfen were below the maximum residue limits set by European Union in chili and brinjal, respectively, at the time of harvest and that the use of this pesticide formulation is safe.

Dissipation behavior and risk assessment of tolfenpyrad from tea bushes to consuming

The dissipation behavior of tolfenpyrad, a widely used pyrazole insecticide in tea plantations, was investigated during tea bushes growing, manufacturing and brewing. Tolfenpyrad dissipated fast on the tea bushes with the half-lives of 1.8-2.3 days. Manufacturing processes of green tea and black tea further reduced the tolfenpyrad residue by 3.5%-36.4%. The average processing factors (PFs) of tolfenpyrad ranged from 0.68 to 1.40 and 0.84 to 1.30 during the processing of green tea and black tea, respectively. Then a low infusion factor of 9.8%-19.9% was observed during the brewing of made tea, as the water solubility of tolfenpyrad was only 0.087 mg/L. Therefore, more than 96% of the initial deposition of tolfenpyrad was dissipated and not accessible for consuming. Results of the risk quotient (RQ) assessment also indicated a negligible health risk by tea consumption. Results from this study indicated that the residue of tolfenpyrad can be reduced by proper field management, manufacturing and brewing processes, where field dissipation and brewing were key steps to minimize its risks. Data of this study could also provide guidance for rational application of tolfenpyrad in tea plantations.

Residue kinetics of neonicotinoids and abamectin in pistachio nuts under field conditions: model selection, effects of multiple sprayings, and risk assessment

Pistachio is an economically valuable crop, and Iran is among the biggest producers, exporters, and consumers of this product in the world. During the growing season, pistachios are subjected to multiple sprayings with various pesticides, which result in the accumulation of their residues in nuts. These residues have raised concerns regarding consumers' health. In this research, uptake and dissipation kinetics of insecticides imidacloprid (IMI), thiacloprid (THI), thiamethoxam (THX), and abamectin (ABA) were investigated in pistachio nuts. Field experiments were conducted in a pistachio orchard. Pistachio trees were sprayed with the recommended dose of each insecticide formulation and water as the control. Samplings were performed for up to 49 days. Based on the results, pesticides uptake and dissipation kinetics were best fitted to first-order exponential growth (FOEG) and single first-order kinetic (SFOK) models, respectively. Variations in pesticides uptake/dissipation rates were mostly related to their water solubility, pK_a, and log K_ow. THX showed a higher uptake rate (0.16 ± 0.04) compared to IMI (0.10 ± 0.01) and THI (0.06 ± 0.01). The fastest dissipation rates were observed for IMI (0.04 ± 0.002 day^-1) and THX (0.03 ± 0.001 day^-1), while the slowest belonged to THI (0.02 ± 0.003 day^-1). ABA residues were below the quantification limit (LOQ) throughout the experiment. Based on FOEG and SFOK model predictions, multiple sprayings with THI and THX resulted in final concentrations exceeding the maximum residue limit (MRL). Hazard quotients for all pesticides were <1, indicating no risk to humans via consumption of the pistachio nut.

Determination of five pesticides in kumquat: Dissipation behaviors, residues and their health risk assessment under field conditions

The present study was carried out to profile the dissipation patterns and residues of five pesticides (triazophos, profenofos, chlorpyrifos, etoxazole and bifenthrin) on kumquat using QuEChERS method coupled with HPLC-MS/MS. The corresponding dietary health risks were also estimated. In the method validation, satisfactory results of good linearity (r2 ≥ 0.9956), sensitivity (limits of quantification ≤0.01 mg/kg), recoveries (71.0-95.7%) with relative standard deviations (0.70-9.4%) were obtained. The half-lives of the five pesticides in kumquat were 13.6-38.5 d under field conditions according to first-order kinetics. Based on the final residue experiment, dietary exposure risks of profenofos, chlorpyrifos, etoxazole and bifenthrin were all acceptably low, with RQc and RQa values of 0.00199-0.122 and 0.00145-0.200, respectively. However, exposure intake of triazophos posed unacceptable acute and chronic health risks for Chinese residents, especially for children with RQa and RQc up to 4.25 and 2.19. Forbidden use suggestion of triazophos and recommended MRLs of profenofos and bifenthrin were put forward in kumquat for safe production and consumption. This work was significant in providing guidance on appropriate application and MRL establishment of pesticides in kumquat.

Residue behavior, transfer and risk assessment of tolfenpyrad, dinotefuran and its metabolites during tea growing and tea brewing

BACKGROUND

Tolfenpyrad and dinotefuran are two representative pesticides used for pest control in tea gardens. Their application may bring about a potential risk to the health of consumers. Therefore, it is essential to investigate the residue behavior, transfer and risk assessment of tolfenpyrad, dinotefuran and metabolites from tea garden to teacup.

RESULTS

An effective analytical method was established and validated to simultaneously determine tolfenpyrad, dinotefuran and its metabolites (DN and UF) in tea. The average recoveries of tolfenpyrad, dinotefuran, DN and UF were in the range 72.1-106.3%, with relative standard deviations lower than 11.8%. On the basis of the proposed method, the dissipation of tolfenpyrad and dinotefuran in fresh tea leaves followed first-order kinetics models with half-lives of 4.30-7.33 days and 4.65-5.50 days, respectively. With application amounts of 112.5-168.75 g a.i. ha^-1 once or twice, the terminal residues of tolfenpyrad and total dinotefuran in green tea were lower than 19.6 and 7.13 mg kg^-1 , respectively, and below their corresponding maximum residue limits . The leaching rates of tolfenpyrad and total dinotefuran during the tea brewing were in the ranges 1.4-2.3% and 93.7-98.1%, respectively.

CONCLUSION

Tolfenpyrad and dinotefuran in tea were easily degraded. The RQ_c and RQ_a values for tolfenpyrad were 37.6% and 5.4%, which were much higher than for dinotefuran at 24.7% and 0.84%, respectively. The data indicated that there was no significant health risk in tea for consumers at the recommended dosages. The results provide scientific data regarding the reasonable use of tolfenpyrad and dinotefuran aiming to ensure safe tea consuption. © 2021 Society of Chemical Industry.

Dynamics and risk assessment of pesticides in cucumber through field experiments and model simulation

Pesticides are often applied multiple times during cucumber cultivation in China. In order to obtain the residue concentrations and subsequently human health risk assessment after pesticide multiple applications, plenty of field trials have been conducted, consuming a lot of labor force and funds. The application of kinetic models can address this problem to some extent by predicting the residue values of pesticides in cucumber. In this study, a dynamic model (dynamiCROP) was applied in combination with field experiments to investigate the distribution, translocation, and dissipation after the one-time application of seven pesticides in a cucumber-soil environment. Moreover, the residue concentrations after the second and third applications of the seven pesticides were estimated through a "simple superposition method", i.e., superimposing the output results of dynamiCROP after each single pesticide application. The estimated residue concentrations show good agreement with that measured through field experiments with R² = 0.865 and relative root mean squared error (RRMSE) = 13.2%. Meanwhile, the short- and long-term risks of each pesticide were assessed according to the concentrations estimated by the "simple superposition method" with the dynamiCROP model. It shows that the seven pesticides, applied multiple times during cucumber cultivation, pose a very low dietary risk to human health through cucumber intake. Our study presents a cost- and time-efficient way to investigate the dissipation of pesticides in the cucumber-soil environment, predicate the residue concentrations of pesticides after multiple applications and assess the dietary risk of pesticides to human health through cucumber intake.

Residue behavior and risk assessment of validamycin a in grape under field conditions

The dissipation and residue of validamycin A in grapes were investigated under field conditions. An ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method for the determination of validamycin A in grapes was established and validated. Methanol and water (90/10, v/v) were used for validamycin A extraction and purification used MCX solid-phase extraction cartridges. The average recoveries of validamycin A in grapes at 0.01, 0.50, and 5.0 mg/kg levels were between 83.8 and 91.4%, with relative standard deviations of 2.3-3.0%. The half-lives of validamycin A in grape were 4.4-6.1 days. The terminal residues in grapes over a range of harvest times (7, 14, and 21 days) were no more than 0.73 mg/kg. According to Chinese consumption data, the risk quotient (RQ) of validamycin A was 3.22%, demonstrating a low risk to consumers. The current study may offer guidance for validamycin A use and could aid the government in determining the maximum residue level (MRL) values for validamycin A in grapes.

Determination of 12 insect growth regulator residues in foods of different matrixes by modified QuEChERS and UPLC-MS/MS

An analytical method was developed and validated for the simultaneous determination of 12 insect growth regulators (IGRs) (buprofezin, cyantraniliprole, flubendiamide, flonicamid, tolfenpyrad, chlorantraniliprole, RH-5849, methoxyfenozide, chromafenozide, tebufenozide, pyriproxyfen and fenoxycarb) in foods collected from different matrixes by modified QuEChERS and ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples were ultrasonically extracted with acetonitrile containing 0.5% formic acid, and different QuEChERS purification conditions were optimized for different matrixes (vegetable oil, fruit and tea). 12 IGRs were separated on a Plus C18 column, and detected by MS/MS under multiple reaction monitoring (MRM) mode. The developed method was validated in terms of linearity, matrix effect, accuracy and precision. Acceptable recoveries of IGRs in three different substrates (vegetable oil, tea and fruit) at three spiked levels were in the range of 65.47-95.17%, 80.55-110.15%, and 62.02-96.50%, respectively, with RSDs less than 11.58%. The method showed a good linearity (R 2 ≥ 0.9994) for all analytes in the range of 0.2-200 μg L-1. The LODs (S/N = 3) and LOQs (S/N = 10) of the method were 0.04-0.40 μg kg-1, and 0.13-1.24 μg kg-1, respectively. Owing to the advantages of simple operation, high accuracy and sensitivity, this method is suitable for the rapid and simultaneous detection of 12 IGRs in vegetable oil, tea and fruit.

Determination of pesticide residues in edible snails with QuEChERS coupled to GC-MS/MS

A QuEChERS multi-residue GC-MS/MS method was developed for determining 160 pesticides in fresh edible snails. The method was validated according to the EU guidance SANTE/12682/2019. Twenty-seven different pesticides were quantified in the 824 samples analysed. Of these, 22.09% contained pesticide residues; in one case six different pesticides. The most frequently quantified pesticides were chlorpyrifos (108 samples), cypermethrin (50), difenoconazole (24), oxyfluorfen (13), lambda-cyhalothrin (12), tetraconazole and azoxystrobin (7). Other pesticides were found in <5 samples. Of the samples containing residues, 154 exceeded the EU legal limit. However, the estimated daily intake of pesticide residues showed that snail consumption does not represent appreciable risks to consumer health.

Removal residues of pesticides in apricot, peach and orange processed and dietary exposure assessment

The effects of the industrial processing are evaluated of the removal of 16 pesticide residues in canned apricots and peaches and in orange juice. A method of multi-residual extraction that uses QuEChERS and liquid chromatography in tandem with triple quadrupole mass spectrometry was used. The method shows good linearity for the 16 pesticides studied (R2 > 0.999); it is accurate and precise (recoveries of 87-115%, relative standard deviation <8.0%). The processing factors are <0.6, indicating that all the processes significantly reduce the residue levels (spinosad, thiacloprid, pyridaben, bupirimate, flusilazole, triflumizole, flonicamid, imidacloprid, lambda-cyhalothrin, cyproconazole, fludioxinil and cyprodinil, abamectin, chlorpyrifos-methyl, hexythiazox and metalaxyl) initially present in the raw fruits and very significantly during washing/cutting, squeezing and hot pack canning (>55% loss). The risk quotient (EDI/ADI ratio) for canned foods is below 100, indicating that the potential consumer risk for the pesticides studied is practically negligent for human health.

Fate of Pyriproxyfen in Soils and Plants

Since the 1990s, the insect growth regulator pyriproxyfen has been widely used worldwide as a larvicide in vector control and in agriculture to fight a very large number of pests. Due to its widespread use it is of first importance to know how pyriproxyfen behaves in the terrestrial ecosystems. This was the goal of this work to establish the fate profile of pyriproxyfen in soils and plants. Thus, in soil, pyriproxyfen photodegrades slowly but its aerobic degradation is fast. The insecticide presents a high tendency to adsorb onto soils and it is not subject to leaching into groundwater. On the contrary its two main metabolites (4'-OH-Pyr and PYPAC) show a different fate in soil. When sprayed to plants, pyriproxyfen behaves as a translaminar insecticide. Its half-life in plants ranges from less than one week to about three weeks. The review ends by showing how the fate profile of pyriproxyfen in soils and plants influences the adverse effects of the molecule on non-target organisms.

Dissipation and Risk Assessment of Multiresidual Fungicides in Grapes under Field Conditions

Grapes are among the most popular fruits globally, and various fungicides are widely applied to grape crops. As such, the presence of multiple fungicide residues and dietary risks in grapes has become the focus of significant attention. In this study, an easy-to-implement and sensitive UPLC-MS/MS approach was developed to simultaneously determine pyraclostrobin, dimethomorph, cymoxanil, cyazofamid and its metabolite CCIM in grapes via QuEChERS. This approach achieved 78.1-106.0% recovery and a 0.01 mg kg^-1 limit of quantitation (LOQ). Field trials revealed that these compounds had degradation half-lives ranging from 0.9 to 13.3 days. And their terminal residues ranging from < LOQ to 1.36 mg kg^-1 were below the official maximum residue limit (MRL) in China. The short-term risk for each tested fungicide was below 54%. The long-term risk of individual chemicals ranged from 0.0086% to 3.1%, and their cumulative risk was 4.4%. Results indicated that the dietary risk of these fungicides in grapes was minor.

Formation of Carbon Dioxide Attached Fragment Ions in the Fragmentation of Deprotonated Tolfenpyrad and Tebufenpyrad

The in-source collision-induced dissociation (CID) and MS/MS mass spectra of deprotonated tolfenpyrad and tebufenpyrad both showed an unusual fragment ion at m/z 187, but its fragmentation pattern and structure could not be explained by logical neutral losses. Accurate mass measurement indicated that the mass difference between this fragment ion and the dominant fragment ion at m/z 143 equaled to a carbon dioxide (CO₂) molecule. The isolation of the fragment ion m/z 143 in the mass analyzer could spontaneously give rise to the ion m/z 187. The Gibbs free energy of carbon dioxide addition to deprotonated pyrazole ion was significantly negative from the computational results. According to these results, we derived a proposal for the formation and structure of the ion m/z 187, which was an attachment of molecular carbon dioxide to the fragment ion m/z 143 to produce a carboxylate anion. The trace carbon dioxide was speculated to be derived from the residual atmosphere or collision gas in the instrument. This study is valuable for the qualitative and quantitative mass spectrometry analysis of pesticides containing the pyrazole functional group.