Dissipation Behavior and Acute Dietary Risk Assessment of Thiamethoxam and Its Metabolite Clothianidin on Spinach.

Thiamethoxam and its metabolite clothianidin residues pose a potential threat to human health. This study aims to investigate the residue behavior and acute dietary risk assessment of thiamethoxam and clothianidin on spinach. Thiamethoxam and clothianidin were extracted using a quick, easy, cheap, effective, rugged, safe (QuEChERS) method and analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). At spike levels from 0.01 to 5 mg kg−1, the average recoveries of both analytes were in the range of 94.5−105.5%, with relative standard deviations (RSDs) of 3.8−10.9%. The dissipation behavior of thiamethoxam followed first-order kinetics, with half-lives of ≤1.6 days. Clothianidin appeared readily as a plant metabolite with highest level exhibited during 3 to 5 days after application. Temperature and light may be two main factors for degradation of thiamethoxam. Besides, acute risk assessment of thiamethoxam and clothianidin was evaluated with risk quotients (RQs) <100%, which suggested a low health risk for all consumer groups of Chinese residents.

Residue analysis, dissipation patterns of chlorfenapyr, diafenthiuron and their corresponding metabolites in tea trees, and dietary intake risk assessment.

BACKGROUND: Recently, chlorfenapyr and diafenthiuron have been widely used to prevent and control diseases and pests in tea production. However, rare studies have investigated the dissipation patterns of chlorfenapyr, diafenthiuron and their metabolites simultaneously in tea matrices. Here, we established an analytical method to investigate the degradation patterns of five target compounds in tea shoots and made tea samples. Moreover, the dietary intake risk assessment of chlorfenapyr-diafenthiuron mixture among Chinese populations was evaluated based on the supervised field experiment. RESULTS: The mean recoveries of the primary analytes at five spiking levels were between 95.6% and 112.6% in tea shoots and made tea, respectively, and the values of RSD (relative standard deviation) were lower than 9.7% for all the target analytes. The field trial results showed that the half-lives of chlorfenapyr and diafenthiuron based on the residue definition were 10.0-12.4 days and 4.3-5.9 days, respectively, in tea shoots. For the dietary intake risk assessment, the risk quotient (RQ) values in made tea ranged from 30.4% to 73.9% at the pre-harvest interval of 14 days, which were significantly less than 100%. CONCLUSION: The accuracy and precision of the developed method were satisfied by the measurement requirements according to the validation results. The dynamic dissipation experiments suggested that diafenthiuron was much easier to dissipate than chlorfenapyr. Moreover, the existence of tralopyril made the half-life of chlorfenapyr significantly increase, indicating that practical application of chlorfenapyr should take careful consideration of its metabolite. Finally, the potential chronic dietary risks of the chlorfenapyr-diafenthiuron mixture to human communities were within the acceptable range. © 2022 Society of Chemical Industry.

Fate, residues and dietary risk assessment of the fungicides epoxiconazole and pyraclostrobin in wheat in twelve different regions, China.

The fungicides epoxiconazole and pyraclostrobin have been widely used to control wheat fusarium head blight. This study was designed to investigate the dissipation behaviors in different climate regions and provide data for the modification of maximum residue limits of the two fungicides. Wheat samples were collected from field sites in twelve different regions, China and analyzed with an HPLC-MS/MS method for simultaneous detection of epoxiconazole and pyraclostrobin in wheat. The average recoveries of epoxiconazole and pyraclostrobin in wheat matrix were 87-112% and 85-102%, respectively, with the relative standard deviations ≤8.1%. The limits of quantification of epoxiconazole and pyraclostrobin in grain and straw were both 0.01 mg/kg. The dissipations of epoxiconazole and pyraclostrobin followed first-order kinetics, with the half-lives of 10.3 days and 7.6 days, respectively. The terminal residues of epoxiconazole and pyraclostrobin in grain were below 0.034 and 0.028 mg/kg, separately, both lower than the maximum residue limits recommended by China. Based on Chinese dietary pattern and terminal residue distributions, the risk quotients of epoxiconazole and pyraclostrobin were 13.9% and 65.9%, respectively, revealing the evaluated wheat exhibited an acceptably low dietary risk to consumers.

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.

Determination, dissipation dynamics, terminal residues and dietary risk assessment of thiophanate-methyl and its metabolite carbendazim in cowpeas collected from different locations in China under field conditions.

BACKGROUND: Thiophanate-methyl and its metabolite carbendazim are broad-spectrum fungicides used on many crops. The residues of these chemicals could result in potential environmental and human health problems. Therefore, investigations of the dissipation and residue behaviors of thiophanate-methyl and its metabolite carbendazim on cowpeas and associated dietary risk assessments are essential for the safety of agricultural products. RESULTS: A simple analytical approach using liquid chromatography with tandem mass spectrometry was developed and validated for the determination of thiophanate-methyl and carbendazim concentrations in cowpeas. Good linearity (R2 > 0.998) was obtained, and the recoveries and relative standard deviations were 80.0-104.7% and 1.4-5.2%, respectively. The dissipation rates of thiophanate-methyl, carbendazim and total carbendazim were high (half-lives of 1.61-2.46 days) and varied in the field cowpea samples because of the different weather conditions and planting patterns. Based on the definition of thiophanate-methyl, the terminal residues of total carbendazim in cowpea samples were below the maximum residue limits set by Japan for other legumes. The acute and chronic risk quotients of three analytes were 0.0-27.6% in cowpea samples gathered from all terminal residue treatments, which were below 100%. CONCLUSION: An optimized approach for detecting thiophanate-methyl and carbendazim in cowpeas was applied for the investigation of field-trial samples. The potential acute and chronic dietary risks of thiophanate-methyl, carbendazim and total carbendazim to the health of Chinese consumers were low. These results could guide the safe and proper use of thiophanate-methyl in cowpeas and offer data for the dietary risk assessment of thiophanate-methyl in cowpeas. © 2021 Society of Chemical Industry.

Dissipation behavior, residues distribution and dietary risk assessment of tembotrione and its metabolite in maize via QuEChERS using HPLC-MS/MS technique.

The dissipation and residues of tembotrione in corn field application were investigated using liquid chromatography tandem mass spectrometry (LC-MS/MS) method. The average recoveries of tembotrione in maize, corncob, and straw were in the ranges of 98-107% with relative standard deviations (RSDs ≤9.3%), respectively. The recoveries of M5 was in the ranges of 90-108% in all three matrices of maize, with RSDs were 3.3-12.8%. The LODs for tembotrione and M5 in maize were 0.85 µg/L and 1.0 µg/L, 0.84 µg/L and 0.43 µg/L in corncob, 0.94 µg/L and 1.5 µg/L in straw, respectively. The LOQs of the method in maize grain, corncob and straw were 0.01, 0.01 and 0.05 mg/kg for both analytes, respectively. The dissipation of tembotrione in straw was in compliance with the first-order dynamic equation, with half-lives of 1.18-1.23 days at Beijing and Heilongjiang. Total residue of tembotrione in maize grain and corncob matrix were both below 0.02 mg/kg, lower than the max residue limit (MRL) recommended by european food safety authority (EFSA). Risk quotients (RQs) of this pesticide was assessed via comparing national estimated daily intake with acceptable daily intake. The dietary intake risk of tembotrione residue in maize was very low for all groups of Chinese residents. These data could provide scientific data and strategies and facilitate Chinese government to establish the MRLs of tembotrione.

Dissipation of fluazinam in citrus groves and a risk assessment for its dietary intake.

BACKGROUND: Citrus is one of the most important fruit crops worldwide. Fluazinam is a fungicide that is used to control fungal diseases, and its dissipation and residue in citrus fruits should be studied. RESULTS: A Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) procedure combined with gas chromatography with an electron capture detector (GC-ECD) has been developed. The fortified recoveries ranged from 82.1% to 105.9%, with relative standard deviations (RSDs) of less than 5.7%. Fluazinam dissipated relatively quickly following first-order kinetics, with a half-life of 8.5-9.5 days. The experiments on the terminal residue of fluazinam in citrus were conducted at six locations in China, and the risk quotient (RQ) method was applied to citrus fruits for dietary exposure risk assessment based on the terminal residue test. The RQs of fluazinam at three preharvest intervals (PHIs) (21, 28, and 35 days) were all less than 100%, which is an acceptable level for human consumption. The present study provides a reference for the establishment of maximum residue limit (MRL) for fluazinam in citrus. CONCLUSIONS: The dissipation and residues of fluazinam in citrus were monitored. The half-life of less than 10 days showed that fluazinam could degrade relatively easily in citrus. The risk assessment also indicated the intake safety of fluazinam in citrus. © 2019 Society of Chemical Industry.

Residue distribution and risk assessment of two macrocyclic lactone insecticides in green onion using micro-liquid-liquid extraction (MLLE) technique coupled with liquid chromatography tandem mass spectrometry.

A micro-liquid-liquid extraction (MLLE) technique coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis was established and validated to determine the residues of two macrocyclic lactone insecticides (spinetoram and spinosad) in green onion. The limit of quantification (LOQ) of the method, as demonstrated by the lowest acceptable recovery level, was 0.01 mg kg-1, and the obtained recoveries were 78.3-93.4% with relative standard deviations (RSDs) < 12.5%. The method was then applied for analyzing field samples collected after treatment with the tested insecticides under Egyptian open-field condition. The decline pattern, terminal residues, and dietary risk assessment of spinetoram and spinosad residues in green onion were evaluated for food safety. Spinetoram and spinosad residues' decline in green onion followed first-order kinetics with the half-lives of 1.2 and 1.42 days, respectively. Based on the results, the required period to reach their respective maximum residue limits (MRLs) was 1 and 0 days for spinetoram and spinosad residues in green onion, respectively, which indicates a short persistence level and high degradation rate. The results suggest that there is no unacceptable chronic or acute risk to human health from the consumption of green onion treated with spinetoram and spinosad according to the uses considered.

Residue behaviors and risk assessment of flonicamid and its metabolites in the cabbage field ecosystem.

Flonicamid, a novel selective systemic pesticide, can effectively control a broad range of insect pests. However, the dissipation behaviors and the terminal residues of flonicamid and its metabolites in some crops and soils remain unclear. Herein, an easy, sensitive and reliable method using a modified QuEChERS extraction coupled with LC-MS/MS for the simultaneous analysis of flonicamid and its metabolites in cabbage and soil was developed. Based on this method, the dissipation behaviors of flonicamid and its metabolites as well as their persistence in cabbage and soil during harvest were investigated. Flonicamid degraded rapidly, and the half-lives of flonicamid only and total residues (the sum of flonicamid and its metabolites) were 1.49-4.59 and 1.97-4.99 days in cabbage, and 2.12-7.97 and 2.04-7.62 days in soil, respectively. When 50% flonicamid WG was sprayed once or twice at the recommended dose and 1.5-fold the recommended dose, the highest residues of total flonicamid in cabbage and soil from different pre-harvest intervals (3, 7 and 14 days) were 0.070 and 0.054 mg kg-1, respectively. The risk quotient (RQ) of flonicamid based on the consumption data from China was below 16.84%, indicating that the use of flonicamid is non-hazardous to humans. These results could not only guide the safe and responsible use of flonicamid in agriculture but also help the Chinese government establish the maximum residue level (MRL) for flonicamid in cabbage.

Dissipation behavior and risk assessment of imidacloprid and its metabolites in apple from field to products.

Pesticides play vital roles in controlling pests and boosting crop yields. Imidacloprid is widely used all over the world and may form in agricultural products. The presence of pesticide residues in apples raises serious health concerns. Understanding the residual fate of imidacloprid is critical for food safety and human health. In this study, the dissipation behavior, metabolism, household processing and risk assessment of imidacloprid and its metabolites in apple were investigated from filed to products. Field experiment results suggested that the half-lives of imidacloprid at 5 times the recommended dosage was 1.5 times that of the standard dosage. And the final residues of imidacloprid were less than the established maximum residue limits (MRLs). Clarification and simmering had little effect on the reduction the residues of imidacloprid and its metabolites. The calculated processing factors were lower than 1 for imidacloprid and its metabolites, implying that the residual ratios of imidacloprid and its metabolites in each steps of the food processing were reduced. The risk quotients were <1 for all Chinese people, indicating that acceptable risks associated with dietary exposure to imidacloprid in apple. However, the higher risks were observed in young people than adults, and females faced higher risks than males. Given high residue levels in pomace, imidacloprid and its metabolites should be further studied in commercial byproducts.

Dissipation, Residue and Human Dietary Risk Assessment of Pyraclostrobin and Cyazofamid in Grapes Using an HPLC-UV Detector.

Pyraclostrobin is a new broad-spectrum methoxyacrylic acid fungicide. Cyazofamid is a new selective foliar spray acaricide. Here, we studied the degradation rate and final residues of pyraclostrobin and cyazofamid in grape and evaluated their dietary risk to consumers. The average recoveries of pyraclostrobin ether ester, cyazofamid and cyazofamid metabolite (CCIM) in grapes were 84-94%, 92-98% and 99-104%, respectively. The relative standard deviations (RSDs) were 6.0-20.3%, 2.4-10.5% and 1.3-4.0%, respectively, and the LOQs were all 0.05 mg/kg. The digestion dynamics of the experimental sites were in accordance with the first-order kinetic equation. The degradation half-lives of pyraclostrobin ether ester and cyazofamid were 17.8 d-28.9 d and 4.3 d-7.8 d, respectively. The final residues of pyraclostrobin ether ester, cyazofamid and CCIM in grapes were <0.05-1.88 mg/kg, <0.05-0.31 mg/kg and <0.05-0.47 mg/kg, respectively. Using probability models, the total chronic risk values for pyraclostrobin and cyazofamid were calculated to be 0.112-189.617% and 0.021-1.714%, respectively. The results of the contribution analysis indicate that pyraclostrobin poses a much greater risk to Chinese consumers than cyazofamid, especially to children and adolescents, who have a significantly greater risk than adults. This suggests that more consideration should be given to the cumulative risk of compounds for vulnerable groups in the future.

Residual behavior and risk assessment of fluopyram, acetamiprid and chlorantraniliprole used individually or in combination on strawberry.

In this study, fluopyram (FOR), acetamiprid (ATP), and chlorantraniliprole (CAP) were used individually or in combination at the maximum recommended dose in greenhouse strawberries to research the dissipation dynamics and dietary risks. A multi-residue analytical method for FOR, ATP, and CAP in strawberries using UPLC-MS/MS integrated with the QuEChERS approach was developed with strong linearity (R2 ≧ 0.9990), accuracy (recoveries of 82.62 to 107.79%), and precision (relative standard deviations of 0.58% to 12.73%). The limits of quantification were 0.01 mg kg-1. Field results showed that the half-lives of FOR, ATP and CAP in strawberry fruits were 11.6-12.4 days, 6.1-6.7 days, and 10.9-11.7 days, respectively. The half-lives of the three investigated pesticides showed no significant difference when used individually or in combination. A risk assessment indicated that the dietary intake risks of the three pesticides in grown strawberries were 0.0041 to 7.63% whether applied alone or in combination, which demonstrated that the dietary intake risks of the three pesticides in grown strawberries could be negligible for Chinese male and female consumers, and that even though pesticides were used in combination, there was less cause for concern about the safety. This paper serves as a guide for the safe use of FOR, ATP, and CAP on greenhouse strawberries.

Residual behavior and dietary risk assessment of albendazole as fungicide in citrus orchards.

Albendazole is a broad-spectrum fungicide that shows great potential in controlling fungal diseases in citrus. To quantify the dissipation behavior, residue distribution, and dietary risk of albendazole in citrus, we developed an UPLC-MS/MS analysis protocol. The average recovery rate of albendazole in whole citrus and citrus pulp ranged from 74 to 105% with an RSD of 3 to 8%, and a limit of quantification of 0.01 mg kg-1. The degradation half-lives were 2.8-3.0 and 5.7-17.0 days in whole citrus and citrus pulp, respectively, and the final residues of albendazole were <0.059 mg kg-1 with a risk quotient of <1. This study not only demonstrates that the dietary risk of albendazole in citrus is negligible, but also provides empirical data to establish the maximum residual limit (MRL) for the safe application of albendazole in citrus orchards to meet the requirements for food safety as well as international trade.

Dissipation, residue, and dietary risk assessment of dimethachlon in grapes.

Dimethachlon, a dicarboximide fungicide, has gained widespread usage in Asian countries. While considered a low-toxicity fungicide, concerns regarding potential health effects, such as nephrotoxicity, have emerged. To date, neither China nor other countries have established maximum residue limit (MRL) for dimethachlon on grapes, and exposure risk assessment of dimethachlon is lacking. Here, we developed a QuEChERS method coupled with gas chromatography-mass spectrometry (GC-MS) to investigate the dissipation rates and terminal residues of dimethachlon in grapes, along with an assessment of dietary risk to consumers. Our results indicated that the average recoveries of dimethachlon in grapes ranged from 74 to 76%. The limit of quantification (LOQ) was 0.050 mg/kg. After undergoing 112 days of storage at -18 °C, the dissipation rate of dimethachlon in grapes was found to be less than 30%, suggesting a state of stable storage. In the context of good agricultural practice (GAP) guidelines, the half-lives of dimethachlon in grapes were 14.3-18.1 days, which is notably longer compared to the reported values for other crops. The terminal residues of dimethachlon in grapes at 14 and 21 days were found to be < 0.05-0.53 mg/kg and < 0.05-0.29 mg/kg, respectively. Regarding the dietary risk assessment, the calculated risk quotient (RQ) value was significantly below 100%, indicating a negligible chronic risk of dimethachlon in grapes at the recommended dosage. This study provides an important reference for the analysis of dimethachlon and offers valuable empirical data to support the establishment of MRL.

Dissipation behavior, residue transfer, and safety evaluation of chlorantraniliprole and indoxacarb during tea growing and brewing by ultrahigh-performance liquid chromatography-tandem mass spectrometry.

A reliable and simple analytical method was developed and validated to simultaneously determine chlorantraniliprole and indoxacarb in tea using ultrahigh-performance liquid chromatography-tandem mass spectrometry. The average recoveries of chlorantraniliprole were in the range of 86-110%, with the precision of intraday (n = 5) and interday (n = 15) ranging from 1.9 to 8.4% and from 2.4 to 8.8%, respectively. The average recoveries of indoxacarb were in the range 81-105%, with the precision of intraday (n = 5) and interday (n = 15) ranging from 2.0 to 9.8% and from 2.7 to 9.1%, respectively. The limits of quantification (LOQs) were all 0.01 mg/kg. The results based on the supervised field trials showed that chlorantraniliprole and indoxacarb in two tea samples followed first-order kinetics models with half-lives of 2.2-4.7 days and 2.5-3.5 days, which could be regarded as a moderately degrading pesticide. The terminal residues of chlorantraniliprole and indoxacarb in made tea were below 6.7 and 4.5 mg/kg, respectively, lower than their corresponding maximum residue limits (MRLs) established by several major countries and organizations (50 and 5 mg/kg). The leaching rates of chlorantraniliprole and indoxacarb during the tea brewing ranged from 4.78 to 12.62% and 4.13 to 10.67%, respectively. The chronic intake risk quotient (RQc) values for chlorantraniliprole and indoxacarb were 0.24% and 35.10%, while the acute dietary risk assessment (RQa) value of indoxacarb was 5.8%, which were all much lower than 100%. The results in the present study indicated that the health risk posed by the chlorantraniliprole and indoxacarb mixture pesticides was negligible in tea for consumers at the recommended dosages.

Dissipation Behavior, Residue, and Risk Assessment of Benziothiazolinone in Apples.

Benziothiazolinone is the first independently developed fungicide in China. It has been used to effectively control fungal diseases in a variety of fruits, vegetables, and crops. In this study, the degradation behavior and final residue of benziothiazolinone in apples is discussed, and the dietary risk to consumers was evaluated. High-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine benziothiazolinone residues in apple samples from eight different regions of China. The average recovery of benziothiazolinone in apples was 85.5-100.2%, and the relative standard deviation (RSD) was 0.8-14.9%. The limits of the method of quantification of benziothiazolinone in apples was 0.01 mg/kg. Under good agricultural practices (GAP) conditions, the final residues of benziothiazolinone in apples were below 0.01 mg/kg, lower than the maximum residual limit (MRL) of China. Although the degradation half-lives of benziothiazolinone were 23.9 d-33.0 d, the risk quotient (RQ) of benziothiazolinone was 15.5% by calculating the national estimated daily intake and comparing it with the acceptable daily intake. These results suggested that under GAP conditions, the intake of benziothiazolinone from apples exhibits an acceptably low health risk on consumers.

The dissipation behavior, household processing factor and risk assessment for cyenopyrafen residues in strawberry and mandarin fruits.

A modified QuEChERS method for determining cyenopyrafen in strawberries, mandarins and their processed products was established with a good linearity (R2 > 0.9981), accuracy (recoveries of 83% to 111%) and precision (relative standard deviations of 0.9% to 14%). The limit of quantification (LOQ) was 0.01 mg/kg. Field results showed that the half-lives of cyenopyrafen were 6.8 and 11.8 d in strawberry and mandarin respectively, and that the final residues were within established maximum residue limits (MRLs). The household processing factors (PFs) for cyenopyrafen residues in strawberry and mandarin fruits were also studied: residues increased in strawberry jam (PF 1.51) and mandarin juice (1.31) but decreased in strawberries (0.58) and mandarin pulp (<0.17) after washing and peeling, respectively. A risk assessment showed that the risk from long-term dietary exposures to cyenopyrafen was 73.73%, indicating that consuming these products was unlikely to present a public health concern.

Dissipation behavior, residue distribution and dietary risk assessment of field-incurred boscalid and pyraclostrobin in grape and grape field soil via MWCNTs-based QuEChERS using an RRLC-QqQ-MS/MS technique.

A QuEChERS technique employing multi-walled carbon nanotubes was developed and validated for the simultaneous quantitation of boscalid and pyraclostrobin in grape field samples using rapid resolution liquid chromatography triple- quadrupole tandem mass spectrometry. The validated method was successfully applied to determine the levels of residual boscalid and pyraclostrobin in soil and grapes. The dissipation behavior of each fungicide followed first-order kinetics, with a linear correlation coefficient of 0.995-0.998 at 95% confidence. The highest levels of boscalid and pyraclostrobin in grape, with a pre-harvest interval of 14 days and doses of 380-570 mg a.i. kg-1 in three or four applications, were 3.99 mg kg-1 and 0.792 mg kg-1, respectively. These are below the maximum residue limits for boscalid and pyraclostrobin in grape, as recommended by the Chinese Ministry of Agriculture. Risk quotients (RQs) of these pesticides were evaluated by comparing national estimated daily intake with acceptable daily intake. The results yielded RQs for boscalid and pyraclostrobin in grape of 54% and 31.7%, respectively, which suggest a low health risk to consumers.

Residue behavior and risk assessment of thifluzamide in the maize field ecosystem.

In the present work, the dissipation kinetics and final residue levels of thifluzamide in the maize field ecosystem were investigated. Using a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction combined with liquid chromatography-tandem mass spectrometric detection (LC-MS/MS), a rapid, sensitive, efficient, and reliable method for extraction and quantitative analysis of thifluzamide residues in maize grain, maize plant, and soil was developed. Satisfactory recoveries of 78.7-97.0% were achieved with relative standard deviations (RSDs) in the range of 1.6 to 8.2%. The limits of detection (LODs) and the limit of quantification (LOQ) were 0.002-0.005 and 0.010 mg kg-1, respectively. The dissipation kinetics of thifluzamide in maize plant was well fitted by the first-order kinetic model with short half-lives of 0.19-0.22 days, while thifluzamide degraded slowly in soil with half-lives of 4.56-15.85 days. The final residues in maize grain, maize plant, and soil samples collected at the milk stage and the physiological maturity stage were no more than 0.010, 0.807, and 0.278 mg kg-1, respectively. Given that no maximum residue limit (MRL) for thifluzamide in maize has been established, the safety of this fungicide application was estimated by a dietary risk assessment. The hazard quotient was 0.03%, which was substantially less than 1, indicating that the long-term risk induced by the thifluzamide application on maize at the recommended dose is negligible. These results help governments to develop regulations for the safe use of thifluzamide.

Investigation of degradation and penetration behaviors of dimethoate on and in spinach leaves using in situ SERS and LC-MS.

To investigate the degradation and penetration behaviors of the organophosphate insecticide dimethoate applied on spinach leaves, in situ SERS and LC-MS methods were used to detect dimethoate residue on&in spinach leaves picked on different days after treatment (DAT). The SERS and LC-MS methods determined that the dimethoate degradation rate followed first-order kinetics, with a half-life of 3.56 or 4.13days, depending on the respective method. The correlation coefficient of quantification value of these two methods was 0.9562. With the SERS method, we detected most of the penetrated dimethoate in the depth of 60-110µm. With the LC-MS method, we detected dimethoate up to 0.17ng in leaves and that the dimethoate on:in ratio of spinach leaves ranged from 562.25 on 0 DAT to 5.23 on 14 DAT. The combination of these two methods facilitated a better understanding of the behavior and biological fate of pesticides in a complex biological system.