Established Maximum Residue Limits Research Articles

Simultaneous Analysis of 504 Pesticide Multiresidues in Crops Using UHPLC-QTOF at MS1 and MS2 Levels.

A robust analytical method was developed for the simultaneous detection of 504 pesticide multiresidues in various crops using ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF). The method integrates both MS1 and MS2 levels through sequential window acquisition of all theoretical mass spectra (SWATH) analysis, allowing for accurate mass measurements and the construction of a spectral library to enhance pesticide residue identification. An evaluation of the method was carried out according to international standards, including the FAO guidelines and SANTE/11312/2021. Validation across five representative crops-potato, cabbage, mandarin, brown rice, and soybean-demonstrated exceptional sensitivity, with over 80% of the analytes detected at trace levels (≤2.5 μg/kg). Moreover, an impressive 96.8% to 98.8% of the compounds demonstrated LOQs of ≤10 μg/kg. Most compounds exhibited excellent linearity (r2 ≥ 0.980) and satisfactory recovery rates at spiking levels of 0.01 and 0.1 mg/kg. Among 42 crop samples analyzed, pesticides were detected in 1 cabbage, 3 mandarin, and 6 rice samples, with a mass accuracy within ±5 ppm and a Fit score ≥ 70.8, confirming the method's practical applicability and reliability. The detected residues ranged from 12.3 to 339.3 μg/kg, all below the established maximum residue limits (MRLs). This comprehensive approach offers an efficient, reliable, and scalable solution for pesticide multiresidue monitoring, supporting food safety programs and regulatory compliance.

Multi-class, multi-residue analysis of pesticide residues in fishery products using LC and GC-MS/MS

Pesticide residues in agricultural products and the environment have been studied extensively over the years. Through the excessive or illegal use of pesticides, residues enter the surrounding environment and are absorbed by animals. Livestock and fishery products are subject to pesticide residue regulation, which includes the establishment of maximum residue limits. However, currently, fishery products are regulated only for ethoxyquin, neglecting the potential for bioaccumulation. This study aims to develop a method for the multi-class, multi-residue analysis of pesticide residues in fishery products—flatfish, eel, shrimp, and Manila clam—based on the QuEChERS method. A total of 327 compounds, including 263 pesticides and their metabolites, were identified using liquid chromatography and gas chromatography–tandem mass spectrometry. The method can quantify 263 pesticide residues in flatfish, 265 in eel, 264 in shrimp, and 263 in Manila clam, respectively. Additionally, the method can be applied to quantify 244 pesticide residues in seaweed. The method proves effective and useful for monitoring both food safety and environmental contamination.

Monitoring pesticide residues in pepper (Capsicum annuum L.) from Al-Qassim region, Saudi Arabia: Occurrence, quality, and risk evaluations

The Al-Qassim region, a prominent agricultural hub in Saudi Arabia, significantly contributes to the national production of vegetables and fruits. This study validated the standard EN-QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method in conjunction with liquid chromatography–tandem mass spectrometry (LC–MS/MS) to determine 90 multiple pesticide residues in three categories of peppers: green bell, green hot and red chilli peppers. Validation criteria, including linearity range, accuracy, precision, limit of detection (LOD), and limit of quantification (LOQ), were within the acceptance range of the SANTE/11312/2021 guideline. The validated method was then used to analyse 536 pepper samples collected in 2023 from the Al-Qassim region of Saudi Arabia. The analysis of 536 pepper samples revealed that 394 samples (73.51 %) contained pesticide residues, with 126 (23.51 %) exceeding the established maximum residue limits (MRLs). The most frequently identified pesticide was imidacloprid (171 samples, 31.9 %) and acetamiprid (94 samples, 17.54 %), followed by bifenazate and difenoconazole, which were each detected in 66 samples (12.31 %). Among the remaining 32 pesticides, 24 were detected in 1%–10 % of the samples, whereas 8 were detected in <1 %. The 36 pesticides detected were classified into 14 insecticides (38.9 %), 14 fungicides (38.9 %) and 8 acaricides (22.2 %). Notably, the overall detection rate of the pesticides was relatively higher in red chilli peppers (232 %) compared with bell peppers (165 %), followed by green hot peppers (132 %). Red chilli peppers also showed the highest residue concentrations of various pesticides. Neonicotinoids and triazoles exhibited the highest detection rates in this study. The residue quality index (IqR) of the samples analysed fell into the categories excellent (26.49 %), good (31.72 %), and adequate (14.06 %), with 28.73 % of the samples deemed inadequate. Long-term dietary exposure was examined for adults and children. This study highlights the crucial role of continual observation in defending public health and securing the trade standardisation and safety.

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.

Changes of 22 pesticide residues and 3 metabolites during the common processing of Auricularia auricula-judae

It is of great significance to investigate the changes of pesticide residues during processing procedures to ensure the accuracy of dietary risk assessment of pesticide residues. At present, there are few reports about the influence of household processing on pesticide residues in Auricularia auricula-judae. In this study, the changes of 22 pesticides and 3 metabolites during drying and rehydrating process in Auricularia auricula-judae were analyzed, and changes of dietary risk of the residues were assessed. The pesticide residue concentrations increased by 2.8–15.4 times after drying, indicating drying could increase the dietary risk of Auricularia auricula-judae. Different rehydrating conditions, including temperature, duration, and solutions were investigated and compared. The removal rates were the highest (67%–96%) when the Auricularia auricula-judae was rehydrated in clear water at 20 °C for 2h, and the dietary risk could be further reduced for some pesticides using 1.0% NaHCO3 solution for the rehydration. This study provided data for the dietary risk assessment and establishment of maximum residue limits (MRLs) for pesticides in the processed products of Auricularia auricula-judae.

Risk assessment of residues of coccidiostats in food 14 years after the introduction of maximum levels

To ensure food safety, coccidiostats’ residue levels in food of animal origin are monitored to see if they comply with the established Maximum Residue Limits (MRL) and Maximum Levels (ML). The incidence of non-compliant (exceeding permitted limits) results in Europe dropped from 1.01% in 2009 to 0.13% in 2021. Nicarbazin, narasin, lasalocid, and salinomycin were the most frequently reported analytes. During monitoring in Poland in 2016–2022, 14.3% positive samples (above LOQ), and 0.85% non-compliant samples were reported, mostly in eggs and poultry. Based on data collected in Polish monitoring, a risk assessment was performed. In the worst-case, estimated daily intake (EDI) exceeded the acceptable daily intake (ADI) only for toltrazuril, up to three times in every assessed age group. In the average scenario, EDIs of all assessed coccidiostats (decoquinate, diclazuril, lasalocid, nicarbazin, robenidine, salinomycin, and toltrazuril) were well below their corresponding ADIs. The results indicate no direct health risk resulting from the consumption of food of animal origin.

Environmental fate and safety analysis of methoxyfenozide application to control litchi and longan pests

Litchi and longan pests significantly affect crop yield and quality. Chemical prevention and control are very effective for production; therefore, it is crucial to study fate assessment and appropriate field efficacy before pesticide application on crops to appropriately assess the health and ecological risks linked with these agents. This study conducted Good Agricultural Practice (GAP) field trials and laboratory experiments to elucidate the dissipation, terminal residues, and efficacy of methoxyfenozide on litchi and longan in six locations throughout China. To detect methoxyfenozide residues on litchi and longan, a QuEChERS/UPLC-MS/MS-based method was designed. The initial methoxyfenozide levels in litchi and longan ranged from 2.21–2.86 to 0.83–0.95 mg kg−1 and indicated half-lives of 5.1–5.3 and 5.3–5.7 days, respectively. After 7 days of foliage treatment, the concentrations of terminal methoxyfenozide residue were 0.78–2.61 and 0.02–1.01 mg kg−1, which were less than the established maximum residue limit for methoxyfenozide in litchi and longan. The chronic (acceptable daily intake = 0.0055–0.0331%) dietary intake risk analysis for methoxyfenozide in longan and litchi indicated acceptable concentrations of terminal residue for the general population. Methoxyfenozide in litchi and longan was readily degraded in first-order kinetics models, the degradation rate on longan was higher than that on litchi, and their dietary risks were negligible to consumers. Two hundred forty grams per liter of methoxyfenozide suspension concentrate (SC) represents a highly efficacious insecticidal dose to control litchi and longan pests and indicates a significant application potential as it is rapidly degraded and linked with reduced post-treatment residue levels.

Dissipation and Safety Analysis of Dimethomorph Application in Lychee by High-Performance Liquid Chromatography-Tandem Mass Spectrometry with QuEChERS.

This study presents a method for analyzing dimethomorph residues in lychee using QuEChERS extraction and HPLC-MS/MS. The validation parameters for this method, which include accuracy, precision, linearity, and recovery, indicate that it meets standard validation requirements. Following first-order kinetics, the dissipation dynamic of dimethomorph in lychee was determined to range from 6.4 to 9.2 days. Analysis of terminal residues revealed that residues in whole lychee were substantially greater than those in the pulp, indicating that dimethomorph residues are predominantly concentrated in the peel. When applied twice and thrice at two dosage levels with pre-harvest intervals (PHIs) of 5, 7, and 10 days, the terminal residues in whole lychee ranged from 0.092 to 1.99 mg/kg. The terminal residues of the pulp ranged from 0.01 to 0.18 mg/kg, with the residue ratio of whole lychee to pulp consistently exceeding one. The risk quotient (RQ) for dimethomorph, even at the recommended dosage, was less than one, indicating that the potential for damage was negligible. This study contributes to the establishment of maximum residue limits (MRLs) in China by providing essential information on the safe application of dimethomorph in lychee orchards.

MXene/Gold nanoparticles heterostructure as catalase mimic for colorimetric detection of penicillin G

Penicillin G (PenG) is a common antibiotic used to fight bacterial infections in livestock. Its excessive use leads to animal products tainted with antibiotic residues. Consumption of foods contaminated with antibiotics can cause their accumulation in our bodies and pose threats to our health. We developed a colorimetric assay to detect the presence of PenG in real matrices using a hierarchical nanostructure material composed of layered titanium carbide MXene nanosheets (Ti3C2Tx) decorated with gold nanoparticles (AuNPs). The AuNPs were directly grown on the MXene nanosheets via a facile method, which significantly enhanced the catalase-like enzyme activity of MXene. The Ti3C2Tx/AuNPs nanocomposite catalyzed the enzymatic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) to its oxidized form in the presence of hydrogen peroxide, and the reaction products turned the sample solution greenish blue. However, this color-change reaction does not occur when PenG is present in the solution. Our assay performed well with a limit of detection (LOD) of 7.51 nM, which is below the established maximum residue limits for raw milk. We hypothesized and experimentally verified that superoxide anions (O2•-) generated play a critical role in the catalysis of PenG. Our results may help develop a simple and inexpensive colorimetric sensor for the routine detection of PenG in food samples.

Analysis of Food Safety Import Notifications and Relevant Standards and Regulations for Aquaculture Products With a Focus on Antimicrobial Residues and Use

The use of antimicrobials is essential for the aquaculture sector; however, their misuse is cause for concern because it could adversely affect the environment and human health. Irresponsible use of antimicrobials can lead to antimicrobial resistance and result in the presence of unwanted residues in aquaculture products. The establishment of maximum residue limits (MRLs) for antimicrobials is of great importance for monitoring their correct use, but the lack of harmonized standards as well as the regulatory gaps for the aquatic products create a challenging situation, as it is reflected in import notifications related to food safety. This paper collects information about current MRLs for antimicrobials in aquatic commodities in the main importing and exporting countries of aquatic products and compares them with each other and with MRLs set by Codex Alimentarius. This analysis highlighted the need for Codex Alimentarius guidance regarding MRLs for nine antimicrobials in aquaculture products (chlortetracycline, doxycycline, enrofloxacin, erythromycin, florfenicol, sulfadimethoxine + ormetoprim, sulfamerazine, tetracycline, and trimethoprim). This paper shows that there is still work to do to implement exhaustive science‐based international standards for residues permitted in aquatic commodities and promote harmonization.

Method Validation for Simultaneous Determination of Pyriproxyfen and Fenpropathrin in Okra Matrices

Extraction and quantification of pesticide residue from the okra matrix at or below the established maximum residue limit (MRL) is a challenging task for both analytical chemists and regulatory institutions to take corrective actions for human health and safety. to develop a simple rapid and less expensive extraction and cleanup method for simultaneous analysis of pyriproxyfen and fenpropathrin residue in okra two methods: QuEChERS and Liquid-Liquid Extraction (LLE) were tested. Both methods produce reliable results, QuEChERS method was chosen for the present research due to its superior efficiency, low cost as well as reduced risk of exposure to solvents in comparison to Liquid-Liquid Partitioning. The residues of both pesticides were confirmed and quantified by hyphenated gas chromatography-tandem mass spectrometer (GC-MS/MS). The effect of spiking concentration, matrix effect (ME), measurement of inter- and intra-assay repeatability, reproducibility of recovery, and trueness of the results were investigated to validate the effectiveness of the method. Limit of determination (LOD) and limit of quantitation (LOQ) for both the analytes were 0.005 and 0.01 mg/kg. The % recovery of both pesticides ranged between 85.9 to 97.9 % with RSD ≤ 7.19 %. The method fulfilled all the SANTE guidelines (SANTE, 2021) and thus can be extended for routine analysis of multiclass pesticide residue in the okra matrix.

Dissipation Dynamic, Residue Distribution and Risk Assessment of Emamectin Benzoate in Longan by High-Performance Liquid Chromatography with Fluorescence Detection.

A derivatization method combined with high-performance liquid chromatography-fluorescence detection (HPLC-FLD) was used to evaluate the dissipation, residue distribution and risk assessment of emamectin benzoate in whole longan and pulp. The average recoveries were 82-111% with relative standard deviation (RSD) less than 11%. The limit of quantification (LOQ) was 0.001 mg/kg in longan and pulp. The half-lives were 3.3-4.2 days. The terminal residues in whole longan were <0.001-0.025 mg/kg applied two and three times at two levels of dosage with PHIs of 10, 14, and 21 days. The residues in whole longan had a higher quantity than those in the pulp, and the terminal residues of pulp were all lower than LOQ (0.001 mg/kg). The chronic risk of emamectin benzoate was not negligible to humans depending on ADI% value, which was higher than 1; and the acute risk was acceptable to the consumer. This study could provide guidance for the safe use of emamectin benzoate in longan and serve as a reference for the establishment of maximum residue limits (MRLs) in China.

Accurate determination of four tetracycline residues in chicken meat by isotope dilution-liquid chromatography/tandem mass spectrometry

An analytical method based on isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC‒MS/MS) was developed to accurately determine four representative tetracyclines (tetracycline, chlortetracycline, doxycycline, and oxytetracycline) in chicken meat. Tetracyclines are known to have a great tendency for epimerization and keto-enol tautomerism, which often provoke major challenges in their determination. Since this isomerization was found to be unavoidable during the whole chain of the current analysis, the total content (µg kg‒1) of individual tetracycline was quantified as a sum of each parent compound and its respective isomeric forms. Using this approach in combination with IDMS analysis, more consistent, accurate, and reproducible measurement results for the four tetracyclines in chicken meat were acquired. LC-MS/MS conditions and sample preparation processes were comprehensively optimized to minimize the chelating effect of tetracyclines and possible co-extracted interferences. Details of the sample preparation scheme, LC‒MS/MS detection, calculation equation, and method validation are described in this article. The method provided very good accuracy (97.7–102.6%) for all analytes across the concentration range of 10–200 µg kg‒1, with relative standard deviations for intra-day and inter-day precision of less than 4%. The limits of quantification were below 0.2 µg kg‒1, demonstrating the high sensitivity of the method. Furthermore, the measurement uncertainty was generally below 5.5%. Hence, the established method exhibits high-order metrological quality with superior performance over various existing methodologies. Moreover, this method can provide references for general food testing laboratories close to and far below the established maximum residue limits (100 µg kg‒1) for animal muscle tissues.

Analysis of Residues of Pesticides in Tomato Processed Foods

The tomato (Solanum lycopersicon L.) crop has great economic relevance, being one of the most processed agricultural products worldwide. Some pesticides are chemically stable and can remain in food even after processing. In this context, the objective of this work was to analyze food products derived from tomatoes (extract, sauce and ketchup), regarding the levels of pesticide residues. Fifteen samples were acquired from Vale do Jaguaribe, Ceará, Brazil. Six pesticides (bifenthrin, chlorothalonil, chlorpyrifos, cyfluthrin, pyriproxyfen, trifluralin) authorized by Agência Nacional de Vigilância Sanitária (Anvisa) for tomato cultivation were selected for the study. QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction and gas chromatography coupled to mass spectrometry (GC-MS) were used in method validation, according to the recommendations of SANTE 11312/2021 guidelines. Statistical analyzes of linearity show that the six pesticides studied were classified as heterocesdastic. Limits of detection (LOD) and quantification (LOQ) values (0.01-0.03 and 0.03-0.10 mg kg-1, respectively) were below the established maximum residue limits (MRLs) for tomatoes. Accuracy and precision (78-121 and 2.3-16.7%, respectively) were satisfactory. The results indicated that among the 15 analyzed samples, one active ingredient was detected (0.05 mg kg-1) in a tomato sauce sample, lower than MRLs (Anvisa 0.15 mg kg-1 and FAO 0.3 mg kg-1). The results show the relevance of monitoring pesticide residues in tomato-derived products and the validation of new methodologies for food control.

Residual levels and dietary intake risk assessment of 11 pesticides in apricots from different ecological planting regions in China

The frequent and massive use of pesticides has led to pesticide residues in apricot, threatening food safety and human health. A reliable and simple modified QuEChERS method with ultra-performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of 11 pesticides in apricot. Method validation indicated that satisfied linearity (R2 ≥ 0.9959), accuracy (recoveries of 72–119%), sensitivity (limits of detection, 0.03–0.30 μg/kg; limits of quantification, 0.13–1.00 μg/kg), and precision (relative standard deviations ≤ 11.9%), and matrix effects were 0.89–1.13. Apricot samples from different ecological regions in China were collected and tested using the proposed methods. Monitoring results were used to assess the dietary intake risk of Chinese populations of different ages and genders. Dietary risk assessment revealed that the risk quotients were 0.003–1.184% for different gender and age groups in China, indicating none unacceptable public health risk for general population. This work was thus significant in developing a simpler, more efficient and economical analysis method and food safety risks of the 11 pesticides on apricot and facilitated the establishment of maximum residue limits.

Dissipation behavior and dietary exposure risk of pesticides in Brussels sprout evaluated using LC–MS/MS

In this study, the dissipation behavior and dietary exposure risk of eight pesticides in Brussels sprout were evaluated under greenhouse conditions. Brussels sprout samples were collected 0, 7, 14, and 21 days after the last pesticide treatment. Ultra-high performance liquid chromatography with tandem mass spectrometry was used for sample analysis. Recovery rates at different concentrations of pesticides (0.01 and 0.1 mg/kg) were in the range of 70.2–104.5%, and the relative standard deviations were ≤ 10.6%. The pesticide residues in Brussels sprouts were determined for each treatment. For acephate, etofenprox, imidacloprid, indoxacarb, alpha-cypermethrin, zeta-cypermethrin, fludioxonil, and oxytetracycline, the half-lives were, respectively, 11.3, 9.8, 11.3, 15.8, 10.6, 13, 9.1, and 8.2 d and the dietary intake rates were, respectively, 2.90%, 0.81%, 0.7%, 1.19%, 0.06%, 0.24%, 0.05%, and 0.36% of the acceptable daily intake. The findings of this study provide important insights into the establishment of maximum residue limits in the Republic of Korea and pesticide control measures for Brussels sprout.

Selection of the Most Reliable Method for the Analysis of Inhibitory Substances in Raw and Skimmed Milk

Abstract Milk used for human consumption must comply with the European Union legislative requirements for residues of inhibitory substances in milk, the values of which must not exceed the established maximum residue limit. In order to ensure the quality and safety of milk and milk products placed on the market, the presence of residues of inhibitory substances should be monitored and verified. The aim of our study was to select the most reliable method for the analysis of residues of inhibitory substances in milk. In the search for the most reliable method, a total of 49 milk samples were tested in the form of raw milk, skimmed milk and skimmed-milk powder throughout the agri-food chain. For comparison, the microbial inhibition tests Eclipse 50, Eclipse Farm, Explorer 2.0, Delvotest®, Premi®Test and the fast receptor screening test TwinSensor were used. The most relevant results were obtained by the Eclipse 50 and Eclipse Farm tests, the reliability of which were also confirmed by the Explorer 2.0 and Premi®Test tests. Moreover, according to the State Veterinary and Food Administration of the Slovak Republic, Eclipse 50 is an official reference method for the determination of residues of inhibitory substances in milk. Therefore, we can only state that of all the methods used, the Eclipse 50 seems to be the most reliable for routine control analysis of residues of inhibitory substances in all types of milk.

Determination of Residual Triflumezopyrim Insecticide in Agricultural Products through a Modified QuEChERS Method.

A rapid and simple analytical method for triflumezopyrim, a new class of mesoionic insecticides and commercialized molecules from DuPont, was developed with a modified QuEChERS method. The pH adjustment was used to improve the extraction efficiency of acetonitrile solvent, and dispersive solid-phase extraction was employed for the clean-up process. The five selected food commodities were used to verify the present optimized method, which displayed good linearity with an excellent correlation coefficient (R2 = 0.9992–0.9998) in the 0.003–0.30 mg/kg calibration range. The method limits of detection (LOD) and quantification (LOQ) were determined to be a value of 0.003 and 0.01 mg/kg, respectively. The mean recovery for the triflumezopyrim was in the 89.7–104.3% range. The relative standard deviations were ≤9.8% for intra- (n = 5) and inter-day (n = 15) precisions at concentrations of 0.01, 0.1, and 0.5 mg/kg in the five representative samples. The matrix effect has been calculated to confirm the effect during ionization of the analyte in the UPLC-MS/MS. The matrix effects of the instrumental analysis showed that triflumezopyrim was less susceptible to matrices. The proposed analytical method in this study has effectively improved the accuracy, selectivity, and sensitivity for the determination of triflumezopyrim in agricultural commodities; therefore, it can serve as a reference method for the establishment of maximum residue limits (MRLs).

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.

Residue behavior and dietary risk assessment of six pesticides in pak choi using QuEChERS method coupled with UPLC-MS/MS

A reliable and simple modified QuEChERS method with UPLC-MS/MS was developed for the simultaneous determination of six pesticides (dimethomorph, imidaclothiz, lufenuron, methoxyfenozide, pyridaben, spinetoram) and their metabolites in pak choi. Method validation indicated good linearity (R2 ≥ 0.99), accuracy (recoveries of 75%−112%), sensitivity (limits of quantification, 0.002–0.01 mg kg−1), and precision (relative standard deviations ≤ 21%), and matrix effects were −36–28%. The half-lives of the six pesticides in pak choi were 2.2–12 d under open field and greenhouse conditions. Considering the short growth cycle of pak choi, the terminal residue levels (0.046–7.8 mg kg−1) and the relevant maximum residue limits (MRLs) of some countries, 5 d was recommended as the pre-harvest interval for the six pesticides on pak choi. Dietary risk assessment revealed that the risk quotients were 3.1%−58% for different gender and age groups in China, indicating none unacceptable public health risk for general population. The results showed that all the six pesticides degraded faster and the terminal residues were much lower under open field conditions than those under greenhouse conditions, which was mainly due to the influence of rainfall, sunlight and other environmental factors. This work was thus significant in assessing the dissipation fate and food safety risks of the six pesticides on pak choi and facilitated the establishment of maximum residue limits.