A computational and experimental study of cis-trans isomeric pesticides based on collision-induced dissociation of high-resolution mass spectrometry.

RATIONALE: Pesticide isomers are widely available in agricultural production and may vary widely in biological activity, potency, and toxicity. Chromatographic and mass spectrometric analysis of pesticide isomers is challenging due to structural similarities. METHODS: Based on liquid chromatography time-of-flight mass spectrometry, identification of cis-trans isomeric pesticides was achieved through retention time, characteristic fragment ions, and relative abundance ratio. Furthermore, theoretical and basic research has been conducted on the differences in characteristic fragment ions and their relative abundance ratios of cis-trans isomers. On the one hand, the cleavage pathways of six cis-trans isomers were elucidated through collision-induced dissociation to explain different fragment ions of the isomers. On the other hand, for those with the same fragment ions but different abundance ratios, energy-resolved mass spectrometry combined with computational chemical density functional theory in terms of kinetics, thermodynamics, and bond lengths was employed to explain the reasons for the differences in characteristic fragment ions and their abundance ratios. RESULTS: A high-resolution mass spectrometry method was developed for the separation and analysis of cis-trans isomers of pesticides in traditional Chinese medicine Radix Codonopsis, and six pesticide isomers were distinguished by retention time, product ions, and relative abundance ratios. The limits of quantification of the six pesticides were up to 10 µg/kg, and the linear ranges of them were 10-200 µg/kg, with coefficients of determination (R2) > 0.99, which demonstrated the good linearity of the six pesticides. The recoveries of the pesticides at spiked concentrations of 10, 20, and 100 µg/kg reached 70-120% with relative standard deviations ≤20%. CONCLUSIONS: It was demonstrated that the application of the method was well suited for accurate qualitative and quantitative analysis for isomers with different structures, which could avoid false-negative results caused by ignoring other isomers effectively.

Residual levels and dietary exposure risk assessment of banned pesticides in fruits and vegetables from Chinese market based on long-term nontargeted screening by HPLC-Q-TOF/MS.

The negative impact of banned pesticides is of special importance for their high toxicity. In this study, nationwide screening of banned pesticides in 37462 fruit and vegetable samples was carried out from 2012 to 2018 using a self-developed HPLC-Q-TOF/MS technique. The dietary exposure risks associated with the banned pesticides were assessed. The results showed that 66.62 % of the samples were detected at least one pesticide. Among the pesticide-positive samples, a total of 18 banned pesticides were detected in 1798 samples for 1896 times. The risk assessment revealed that 11.71 % of the positive detections exceeded the safety limits and posed an unacceptable risk, while 37.29 % of the positive detections posed acceptable risks. According to the screening and assessment results, two national maps were presented to show the total detection ratios of the banned pesticides and the unacceptable risks of dietary exposure. It should be noted that omethoate had higher residual concentration, unacceptable risk frequency and unacceptable risk proportion. This is the first nationwide comprehensive report on screening and risk assessment banned pesticides.

Efficiency and mechanism of C18-functionalized magnetic nanoparticles for extracting weakly polar pesticides from human serum determined by UHPLC-QTOF-MS and molecular dynamics simulations.

Detecting pesticide residues in human serum is a challenging process due to trace-level chronic exposure. Several methods using magnetic adsorbents have been developed for analyzing pesticide residue levels in human serum, but it is still difficult to achieve lower quantitative levels, and the adsorption mechanism for extracting pesticides is unclear. Herein, we propose a feasibility concept of using C18-functionalized magnetic nanoparticles for the adsorption of target pesticides, focusing on the extensively used weakly polar pesticides based on molecular dynamics (MD) simulations. To support this, the facilitated target nanoparticles of Fe3O4@SiO2-C18 were synthesized at a size of 12-13 nm with a magnetic saturation of 40 emu/g. After optimizing and establishing the extraction conditions (1.8 mL C18 modifier, 10 mg sorbents, 3 min adsorption time, 1000 µL ACN for desorption eluent at pH 3.8 and 5 min desorption time), which exhibited recovery = 72.3%-118.3% with RSDs = 0.03-6.57, linearity at 0.01-10 ng/mL with R2 = 0.9561-0.9993, and LODs = 0.01-0.30 ng/mL for the 11 weakly polar pesticides in human serum. Furthermore, the mechanism by which the C18 group selectively extracts weakly polar pesticides was confirmed by binding van der Waals and electrostatic interactions under stable and strong binding energy. The extraction process of efficient adsorption and desorption with C18 functional magnetite nanoparticles suggests a simple method for detecting weakly polar pesticides. The concept may lead to a general approach to analyzing multiple pesticide residues in human serum at trace levels.

Imidacloprid increases intestinal permeability by disrupting tight junctions.

The neonicotinoid pesticide, imidacloprid (IMI), is frequently detected in the environment and in foods. It is absorbed and metabolized by the intestine; however, its effects on intestinal barrier integrity are not well studied. We investigated whether IMI disrupts the permeability of the intestinal epithelial barrier via in vivo tests on male Wistar rats, in vitro assays using the human intestinal epithelial cell line, Caco-2, and in silico analyses. A repeated oral dose 90-day toxicity study was performed (0.06 mg/kg body weight/day). IMI exposure significantly increased intestinal permeability, which led to significantly elevated serum levels of endotoxin and inflammatory biomarkers (tumor necrosis factor-alpha and interleukin-1 beta) without any variation in body weight. Decreased transepithelial electrical resistance with increased permeability was also observed in 100 nM and 100 µM IMI-treated Caco-2 cell monolayers. Amounts of tight junction proteins in IMI-treated colon tissues and between IMI-treated Caco-2 cells were significantly lower than those of controls. Increased levels of myosin light chain phosphorylation, myosin light chain kinase (MLCK), and p65 subunit of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB p65) phosphorylation were found in IMI-exposed cells compared with control cells. Furthermore, the barrier loss caused by IMI was rescued by the MLCK inhibitor, ML-7, and cycloheximide. Pregnane X receptor (PXR, NR1I2) was inhibited by low-dose IMI treatment. In silico analysis indicated potent binding sites between PXR and IMI. Together, these data illustrate that IMI induces intestinal epithelial barrier disruption and produces an inflammatory response, involving the down-regulation of tight junctions and disturbance of the PXR-NF-κB p65-MLCK signaling pathway. The intestinal barrier disruption caused by IMI deserves attention in assessing the safety of this neonicotinoid pesticide.

Simultaneous determination and risk assessment of highly toxic pesticides in the market-sold vegetables and fruits in China: A 4-year investigational study.

This study investigated the levels of highly toxic pesticides (HTPs) in 6554 vegetable and fruit samples from 31 regions of China, along with the associated risk of dietary exposure for the population between 2014 and 2017. 18 HTPs were detected in 325 (4.96%) samples, and the levels of HTPs in 103 (1.57%) samples were found to be higher than the maximum residue limits (MRLs) of China. The rate of detection of HTPs in six types of vegetables and fruits, in a decreasing order, was found to be as follows: eggplant (8.84%) >grape (5.58%) >tomato (5.43%) >cucumber (5.43%) >pear (3.12%) >apple (2.30%). The level of contamination of HTPs was found to be higher in vegetables compared with fruits. The vegetable and fruit samples with the highest percentages of HTPs exceeding MRLs were found in eggplants from Guangxi (20%) and grapes from Inner Mongolia (12.5%), respectively. Both, the average target hazard quotient (THQ) of a single highly toxic pesticide (HTP) and the average hazard index (HI) of the mixture of HTPs for adults and children from vegetables and fruits from the 31 regions were found to be less than one. Omethoate, carbofuran, ethoprophos, triazophos, and phorate were identified as the major contributors to the average HI for vegetables, and carbofuran, ethoprophos, omethoate, phorate, and phosphamidon were identified as the primary contributors to the average HI for fruits. The results of this study revealed that HTPs in vegetables and fruits did not cause any significant chronic risk of dietary exposure. The detection of HTPs exceeding MRLs in some of the samples implied that appropriate management guidelines for HTPs should be implemented to protect the health of the consumers.

Triazophos and its metabolite diethyl phosphate have different effects on endocrine hormones and gut health in rats.

Organophosphorus pesticide (OP) residues present in food can be metabolized into diethylphosphate (DEP) in vivo. Epidemiological studies of OPs have usually focused on these metabolites, while animal studies mainly assessed the OPs. Here, we compared the health risks of a frequently detected OP, triazophos (TAP), and its major metabolite, DEP, in rats. Levels of serum lipids and, sex hormones were measured using immunoassay kits. Gut hormones and inflammatory cytokines were assessed using a multiplexing kit, and the gut microbiota was evaluated by 16S rRNA gene sequencing. After a 24-week exposure period, both TAP and DEP significantly decreased serum levels of triglycerides, cholesterol, low-density lipoprotein cholesterol, and IL-6 (p < 0.05). However, DEP exposure had a stronger effect on serum estradiol (p < 0.05) than TAP, whereas only TAP inhibited the secretion of gut hormones. Both TAP and DEP enriched the pathogenic genera Oscillibacter, Peptococcus and Paraprevotella in the gut, and TAP also enriched enteritis-related genera Roseburia and Oscillibacter, which may affect the secretion of gut hormones. These findings indicate that the use of dialkyl phosphates as markers of OPs to examine the correlations of OP exposure with diseases may only provide partial information, especially for diseases related to gut health and the endocrine system.

Assessment of the endocrine-disrupting effects of diethyl phosphate, a nonspecific metabolite of organophosphorus pesticides, by in vivo and in silico approaches.

Organophosphorus pesticides (OPs) remain one of the most commonly used pesticides, and their detection rates and residues in agricultural products, foods and environmental samples have been underestimated. Humans and environmental organisms are at high risk of exposure to OPs. Most OPs can be degraded and metabolized into dialkyl phosphates (DAPs) in organisms and the environment, and can be present in urine as biomarkers for exposure to OPs, of which diethyl phosphate (DEP) is a high-exposure metabolite. Epidemiological and cohort studies have found that DAPs are associated with endocrine hormone disorders, especially sex hormone disorders and thyroid hormone disorders, but there has been no direct causal evidence to support these findings. Our study explored the effects of chronic exposure to DEP on endocrine hormones and related metabolic indicators in adult male rats at actual doses that can be reached in the human body. The results showed that chronic exposure to DEP could cause thyroid-related hormone disorders in the serum of rats, causing symptoms of hyperthyroidism in rats, and could also lead to abnormal expression of thyroid hormone-related genes in the rat liver. However, DEP exposure did not seem to affect serum sex hormone levels, spermatogenesis or sperm quality in rats. The molecular interactions between DEP and thyroid hormone-related enzymes/proteins were investigated by molecular docking and molecular dynamics methods in silico. It was found that DEP could strongly interact with thyroid hormone biosynthesis, blood transport, receptor binding and metabolism-related enzymes/proteins, interfering with the production and signal regulation of thyroid hormones. In vivo and in silico experiments showed that DEP might be a potential thyroid hormone-disrupting chemical, and therefore, we need to be more cautious and rigorous regarding organophosphorus chemical exposure.

Assessment of the endocrine-disrupting effects of organophosphorus pesticide triazophos and its metabolites on endocrine hormones biosynthesis, transport and receptor binding in silico.

Triazophos (TAP) was a widely used organophosphorus insecticide in developing countries. TAP could produce specific metabolites triazophos-oxon (TAPO) and 1-phenyl-3-hydroxy-1,2,4-triazole (PHT) and non-specific metabolites diethylthiophosphate (DETP) and diethylphosphate (DEP). The objective of this study involved computational approaches to discover potential mechanisms of molecular interaction of TAP and its major metabolites with endocrine hormone-related proteins using molecular docking in silico. We found that TAP, TAPO and DEP showed high binding affinity with more proteins and enzymes than PHT and DETP. TAP might interfere with the endocrine function of the adrenal gland, and TAP might also bind strongly with glucocorticoid receptors and thyroid hormone receptors. TAPO might disrupt the normal binding of androgen receptor, estrogen receptor, progesterone receptor and adrenergic receptor to their natural hormone ligands. DEP might affect biosynthesis of steroid hormones and thyroid hormones. Meanwhile, DEP might disrupt the binding and transport of thyroid hormones in the blood and the normal binding of thyroid hormones to their receptors. These results suggested that TAP and DEP might have endocrine disrupting activities and were potential endocrine disrupting chemicals. Our results provided further reference for the comprehensive evaluation of toxicity of organophosphorus chemicals and their metabolites.

Age- and diet-specific effects of chronic exposure to chlorpyrifos on hormones, inflammation and gut microbiota in rats.

Chlorpyrifos is a pesticide frequently detected in food and has been reported to disturb endocrine and gut health, which was regulated by gut microbiota and enteroendocrine cells. In this study, newly weaned (3 week) and adult (8 week) male rats fed a normal- or high- fat diet were chronically exposed to 0.3 mg chlorpyrifos/kg bodyweight/day. The effects of chlorpyrifos exposure on serum hormone levels, proinflammatory cytokines and gut microbiota were evaluated. Chronic exposure to chlorpyrifos significantly decreased the concentrations of luteinizing hormone, follicule stimulating hormone and testosterone, which was found only in the normal-fat diet. The counteracted effect of high-fat diet was also found in gut hormones and proinflammatory cytokines. Significantly higher concentrations of glucagon-like peptide-1, pancreatic polypeptide, peptide tyrosine tyrosine (PYY), ghrelin, gastric inhibitory poly-peptide, IL-6, monocyte chemoattractant protein-1, and TNF-α were found in rats exposed to chlorpyrifos beginning at newly weaned, whereas only the PYY, ghrelin and IL-6 concentrations increased significantly in rats exposed in adulthood. Furthermore, a decrease in epinephrine induced by chlorpyrifos exposure was found in rats exposed to chlorpyrifos beginning at newly weaned, regardless of their diet. Chlorpyrifos-induced disturbances in the microbiome community structure were more apparent in rats fed a high-fat diet and exposed beginning at newly weaned. The affected bacteria included short-chain fatty acid-producing bacteria (Romboutsia, Turicibacter, Clostridium sensu stricto 1, norank_f_Coriobacteriaceae, Faecalibaculum, Parasutterella and norank_f__Erysipelotrichaceae), testosterone-related genus (Turicibacter, Brevibacterium), pathogenic bacteria (Streptococcus), and inflammation-related bacteria (unclassified_f__Ruminococcaceae, Ruminococcaceae_UCG-009, Parasutterella, Oscillibacter), which regulated the endocrine system via the hypothalamic-pituitary-adrenal axis, as well as the immune response and gut barrier. Early exposure accelerated the endocrine-disturbing effect and immune responses of chlorpyrifos, although these effects can be eased or recovered by a high-fat diet. This study helped clarify the relationship between disrupted endocrine function and gut microbiota dysbiosis induced by food contaminants such as pesticides.

Effects of Diethyl Phosphate, a Non-Specific Metabolite of Organophosphorus Pesticides, on Serum Lipid, Hormones, Inflammation, and Gut Microbiota.

Organophosphorus pesticides (OPs) can be metabolized to diethyl phosphate (DEP) in the gut environment, which may affect the immune and endocrine systems and the microbiota. Correlations between OPs and diseases have been established by epidemiological studies, mainly based on the contents of their metabolites, including DEP, in the serum or urine. However, the effects of DEP require further study. Therefore, in this study, adult male rats were exposed to 0.08 or 0.13 mg/kg DEP for 20 weeks. Serum levels of hormones, lipids, and inflammatory cytokines as well as gut microbiota were measured. DEP significantly enriched opportunistic pathogens, including Paraprevotella, Parabacteroides, Alloprevotella, and Helicobacter, leading to a decrease in interleukin-6 (IL-6). Exposure to the high dose of DEP enriched the butyrate-producing genera, Alloprevotella and Intestinimonas, leading to an increase in estradiol and a resulting decrease in total triglycerides (TGs) and low-density lipoprotein cholesterol (LDL-C); meanwhile, DEP-induced increases in peptide tyrosine‒tyrosine (PYY) and ghrelin were attributed to the enrichment of short-chain fatty acid-producing Clostridium sensu stricto 1 and Lactobacillus. These findings indicate that measuring the effects of DEP is not a proxy for measuring the effects of its parent compounds.

3-Monochloropropane-1, 2-diol causes irreversible damage to reproductive ability independent of hormone changes in adult male rats.

3-MCPD, a contaminant frequently detected in foodstuffs, has been reported to damage human kidneys and testes. Previous studies can be used to evaluate the risk to humans of exposure to excessive 3-MCPD for a short period. However, the effects of withdrawal after 3-MCPD exposure have rarely been studied. Adult male SD rats were orally administered 0, 36 and 72 mg 3-MCPD/kg b.w./day for 4 weeks, followed by a 7-week recovery period. 3-MCPD significantly reduced RBC, HGB and HCT levels, indicating a phenotype of anemia, which returned to normal after the recovery period. 3-MCPD induced dysfunction in the liver and kidneys, which were characterized by hepatomegaly and elevated serum ALT, TBIL levels, and nephromegaly and elevated serum urea, UA contents. These effects were also restored to normal after the recovery period. Although the abnormal levels of testosterone and progesterone returned to normal, 3-MCPD-induced atrophy in testes, decreased sperm concentration and motility, and an increased rate of teratosperm still existed after the recovery period. 3-MCPD can induce restorable anemia and dysfunction in liver and kidney but irreversibly damage the reproductive system with normal sex hormone levels. This study may provide a novel perspective for characterizing the ongoing risk of exposure to 3-MCPD.

Screening of 439 Pesticide Residues in Fruits and Vegetables by Gas Chromatography-Quadrupole-Time-of-Flight Mass Spectrometry Based on TOF Accurate Mass Database and Q-TOF Spectrum Library.

Because of its unique characteristics of accurate mass full-spectrum acquisition, high resolution, and fast acquisition rates, GC-quadrupole-time-of-flight MS (GC-Q-TOF/MS) has become a powerful tool for pesticide residue analysis. In this study, a TOF accurate mass database and Q-TOF spectrum library of 439 pesticides were established, and the parameters of the TOF database were optimized. Through solid-phase extraction (SPE), whereby pesticides are extracted from fruit and vegetable substrates by using 40 mL 1% acetic acid in acetonitrile (v/v), purified by the Carbon/NH2 SPE cartridge, and finally detected by GC-Q-TOF/MS, the rapid analysis of 439 pesticides in fruits and vegetables can be achieved. The methodology verification results show that more than 70 and 91% of pesticides, spiked in fruits and vegetables with concentrations of 10 and 100 µg/kg, respectively, saw recoveries that conform to the European Commission's criterion of between 70 and 120% with RSD ≤20%. Eighty-one percent of pesticides have screening detection limits lower than 10 µg/kg, which makes this a reliable analysis technology for the monitoring of pesticide residues in fruits and vegetables. This technology was further validated for its characteristics of high precision, high speed, and high throughput through successful detection of 9817 samples during 2013-2015.

High-Throughput Analytical Techniques for the Determination of the Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea, Part VII: A GC-MS, GC-MS/MS, and LC-MS/MS Study of the Degradation Profiles of Pesticide Residues in Green Tea.

GC-MS, GC-tandem MS (MS/MS), and LC-MS/MS were used to mathematically define the degradation profiles of pesticide residues in two field trials. Nineteen pesticides were studied in the first field trial and 11 in the second. The results of the field trials demonstrated that the degradation profiles of pesticide residues in green tea can be described with power functions to successfully estimate the amount of time, following pesticide application, pesticide residues appearing in tea in concentrations at and/or above the maximum residue limit (MRL) decrease to concentrations below the MRL. Stability tests on green tea samples stored at room temperature were conducted to determine whether pesticide-incurred green tea samples prepared according to the method used in the field trials would be suitable for the preparation of reference standards for laboratory-proficiency testing trials. This paper reports the results of a GC-MS, GC-MS/MS, and LC-MS/MS study, as well as the suitability of the samples prepared under these conditions for use as pesticide reference standards in tea analysis.

Wide-scope screening of pesticides in fruits and vegetables using information-dependent acquisition employing UHPLC-QTOF-MS and automated MS/MS library searching.

This paper presents an application of ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) for simultaneous screening and identification of 427 pesticides in fresh fruit and vegetable samples. Both full MS scan mode for quantification, and an artificial-intelligence-based product ion scan mode information-dependent acquisition (IDA) providing automatic MS to MS/MS switching of product ion spectra for identification, were conducted by one injection. A home-in collision-induced-dissociation all product ions accurate mass spectra library containing more than 1700 spectra was developed prior to actual application. Both qualitative and quantitative validations of the method were carried out. The result showed that 97.4 % of the pesticides had the screening detection limit (SDL) less than 50 µg kg-1 and more than 86.7 % could be confirmed by accurate MS/MS spectra embodied in the home-made library. Meanwhile, calibration curves covering two orders of magnitude were performed, and they were linear over the concentration range studied for the selected matrices (from 5 to 500 µg kg-1 for most of the pesticides). Recoveries between 80 and 110 % in four matrices (apple, orange, tomato, and spinach) at two spiked levels, 10 and 100 µg kg-1, was 88.7 or 86.8 %. Furthermore, the overall relative standard deviation (RSD, n = 12) for 94.3 % of the pesticides in 10 µg kg-1 and 98.1 % of the pesticides in 100 µg kg-1 spiked levels was less than 20 %. In order to validate the suitability for routine analysis, the method was applied to 448 fruit and vegetable samples purchased in different local markets. The results show 83.3 % of the analyzed samples have positive findings (higher than the limits of identification and quantification), and 412 commodity-pesticide combinations are identified in our scope. The approach proved to be a cost-effective, time-saving and powerful strategy for routine large-scope screening of pesticides.

High-Throughput Analytical Techniques for Determination of Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea, Part VI: Study of the Degradation of 271 Pesticide Residues in Aged Oolong Tea by Gas Chromatography-Tandem Mass Spectrometry and Its Application in Predicting the Residue Concentrations of Target Pesticides.

The degradation rate of 271 pesticide residues in aged Oolong tea at two spray concentrations, named a and b (a < b), were monitored for 120 days using GC-tandem MS (GC-MS/MS). To research the degradation trends and establish regression equations, determination days were plotted as horizontal ordinates and the residue concentrations of pesticide were plotted as vertical ordinates. Here, we consider the degradation equations of 271 pesticides over 40 and 120 days, summarize the degradation rates in six aspects (A-F), and discuss the degradation trends of the 271 pesticides in aged Oolong tea in detail. The results indicate that >70% of the determined pesticides coincide with the degradation regularity of trends A, B, and E, i.e., the concentration of pesticide will decrease within 4 months. Next, 20 representative pesticides were selected for further study at higher spray concentrations, named c and d (d > c > b > a), in aged Oolong tea over another 90 days. The determination days were plotted on the x-axis, and the differences between each determined result and first-time-determined value of target pesticides were plotted on the y-axis. The logarithmic function was obtained by fitting the 90-day determination results, allowing the degradation value of a target pesticide on a specific day to be calculated. These logarithmic functions at d concentration were applied to predict the residue concentrations of pesticides at c concentration. Results revealed that 70% of the 20 pesticides had the lower deviation ratios of predicted and measured results.

High Throughput Analytical Techniques for the Determination and Confirmation of Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea by GC/MS, GC/MS/MS, and LC/MS/MS: Collaborative Study, First Action 2014.09.

Thirty laboratories from fom North and South America, Europe, and Asia participated in this AOAC collaborative study (15 from China; five from Germany; two each from Italy and the United States; and one each from the Republic of Korea, Canada, Spain, Japan, Belgium, and India). Participants represented government regulatory, commercial testing, university, research institute, and private laboratories. The single-laboratory validated (SLV) tea method was evaluated in the collaborative study to determine the recovery and reproducibility of the method under multilaboratory conditions. Since there were no restrictions regarding the type of analytical instrumentation to use for the analyses, laboratories used a combination of equipment that included GC/MS, GC/MS/MS, and LC/MS/MS instruments from 22 different manufacturers, 21 brands of GC and LC columns, 13 different GC temperature programming profiles, 11 LC gradient elution programs, and six different vendor manufactured SPE cartridges. Even though all the analytical performance parameters for all the 653 compounds had been determined in the SLV study, guidance was obtained from an expert review panel of the AOAC Method-Centric Committee on Pesticide Residues to conduct the multilaboratory collaborative study based on 20 selected compounds that can be analyzed by GC/MS and 20 compounds that can be analyzed by LC/MS/MS. Altogether, 560 samples covering the 40 selected pesticides were analyzed in the study. These samples included green tea and oolong tea samples fortified typically at the European Union maximum residue limit for regulatory guidance and compliance, aged tea samples incurred with 20 pesticides, and green tea and oolong tea samples incurred with five pesticides. The analysis of the 560 samples generated a total of 82 459 test results by the 30 participating laboratories. One laboratory failed to meet the proficiency requirements in the precollaborative study. Therefore, its data submitted for the collaborative study were excluded from further analysis and interpretation. The results presented are therefore the 6638 analytical results obtained from the 29 remaining laboratories, which included 1977 results generated by GC/MS, 1704 results by GC/MS/MS, and 2957 results by LC/MS/MS. It was determined after application of the Grubbs and Dixon tests for outliers to the data sets that there were 65 outlier results from the 1977 GC/MS results (3.3%), 65 outlier results from the 1704 GC/MS/MS results (3.8%), and 57 outlier results out of 2957 LC/MS/MS results (1.9%), representing 0.98, 0.98, and 0.86%, respectively, of the 6638 results generated in the study. Analysis with the AOAC statistical software package also confirmed that the method is rugged, and average recovery, average concentration, RSDr, RSDR, and HorRat values all meet recovery and reproducibility criteria for use in multiple laboratories. The Study Director is recommending this method for adoption as an AOAC First Action Official MethodSM.

[Comparison of the performances of gas chromatography-quadrupole time of flight mass spectrometry and gas chromatography-tandem mass spectrometry in rapid screening and confirmation of 208 pesticide residues in fruits and vegetables].

The performances of gas chromatography-tandem mass spectrometry (GC-MS/MS) and gas chromatography quadrupole time of flight mass spectrometry (GC-QTOF/MS) for the determination of 208 pesticide residues in fruit and vegetable samples, including apple, orange, tomato and cucumber, were compared comprehensively. Based on the differences of the two instruments, their respective characteristics and scopes of application in the detection of the pesticide residues were presented, which provided the reference for the analysis of pesticide residues. The performance parameters of the two instruments, such as overall recoveries, precisions, limits of detection, linear ranges, identification points and matrix effects, were evaluated according to a designed experiment. At three spiked levels (5.0, 10.0 and 20.0 µg/kg), the average recoveries for the majority of pesticides (93.0%) ranged from 70% to 120% in the four matrices with relative standard deviations below 20%. The limits of detection for most of the pesticides by GC-MS/MS and GC-Q-TOF/MS were less than 5.0 µg/kg. Compared with GC-QTOF/MS, GC-MS/MS showed relatively lower limits of detection and wider linear ranges, and its performance was more satisfactory in accurate quantitative analysis due to its superior sensitivity. On the other hand, GC-QTOF/MS provided accurate mass measurement, which was proved to be an efficient analytical tool on the rapid screening and confirmation of a large number of pesticides and non-target compounds.

High-Throughput Analytical Techniques for Multiresidue, Multiclass Determination of 653 Pesticides and Chemical Pollutants in Tea-Part IV: Evaluation of the Ruggedness of the Method, Error Analysis, and Key Control Points of the Method.

A 3 month study was conducted on the ruggedness of a multiresidue method for accuracy and stability. The results indicate that in terms of Youden pair ratios of 201 pesticide aged tea samples falling approximately within 1.00-1.20 of the ratio of theoretical spraying concentrations, the differences do not exceed 5% for percentages made up by ratios of the fixed values obtained by two kinds of instruments for two teas and those made up by 18 circular determinations. However, regarding two kinds of SPE cartridges, the Cleanert TPT cartridge is higher than the ENVI-CARB+primary secondary amine (PSA) cartridge by 10%. Pertaining to RSD values of "parallel samples" and whether it is green tea or Woolong tea, the percentages of RSD≤15% values of the parallel samples all exceed 88%. Whether it is the first or circular determination for two teas and analytical results from two kinds of instruments, the percentages of RSD≤15% values have a difference of less than 6%, while the TPT cartridge is better than ENVI-CARB+PSA by above 6% for the two cartridges. Concerning RSDs of Youden pair ratios, RSD≤15% values have a proportion exceeding 85% for both green tea and Woolong tea, and the percentage is greater than 87% whether it is for two kinds of SPE cartridges or two kinds of instruments. In terms of Youden pair ratios and the classified statistical analysis of the ruggedness data of parallel samples, the proportion of RSD≤15% values of Youden pair ratios is 8% higher for the TPT cartridge than the ENVI-CARB+PSA cartridge; the proportion of RSD≤15% values of parallel samples is 6.2% higher for the TPT cartridge than the ENVI-CARB+PSA cartridge. Data show no marked differences for two teas and two kinds of instruments. A comparison of the aforementioned aspects finds that good ruggedness was obtained with both SPE cleanup methods, and the results from the TPT cartridge are better than those from the ENVI-CARB+PSA cartridge.

High-Throughput Analytical Techniques for Determination of Residues of 653 Multiclass Pesticides and Chemical Pollutants in Tea--Part V: A Comparative Study of the Influence of Tea Hydration on the Efficiency of Pesticide Multiresidue Determination Using Three Sample Preparation Methods and GC/MS/MS.

This paper describes a comparative study of the influence of three sample preparation techniques (M1: hydration+oscillating extraction+partial extraction solution hexane partitioning cleanup; M2: hydration+oscillating extraction+overall extraction solution SPE cleanup; and M3: pure acetonitrile homogeneous extraction+overall extraction SPE cleanup) on the determination efficiency of 456 pesticide multiresidues in tea. First, it was discovered from the mathematical correlation equation of 329 pesticide recoveries established and log Kow values that the extraction efficiency of hydration method M1 has obvious correlation with pesticide log Kow, making the extraction efficiency of M1 take the shape of an arc trend line with a certain arc hanging down from both ends of polar pesticides and nonpolar pesticides. Second, regarding the M1 method, the interfering matter after co-extraction increased in large quantities, which markedly lowered the S/N of the target pesticides and method sensitivity, leading to an obvious decrease of the method efficiency. The fortification experiment of the uniform limit 0.010 mg/kg proved that with the M1 hydration method there are 23 pesticides with recoveries between 70 and 120% and RSD<20%, accounting for only 5.0%, while with nonhydration method M3 there are 229 pesticides, making up 50%.

High-throughput analytical techniques for multiresidue, multiclass determination of 653 pesticides and chemical pollutants in tea--Part III: Evaluation of the cleanup efficiency of an SPE cartridge newly developed for multiresidues in tea.

A comparative study was conducted over three stages on the cleanup efficiency of SPE cartridge Cleanert TPT, newly developed for multigroups of pesticide residues in tea. In Stage I, different SPE cartridges C18, graphite carbon black (GCB), primary secondary amine (PSA), and amino (NH2) were purchased and combined into 12 different sequences. Through the comparative test on cleanup efficiency of 84 representative pesticides in tea, Envi-Carb GCB + PSA with a good cleanup effect was selected. In Stage II, GC/MS test results from the comparative study of the extraction efficiency of 201 pesticides spiked into green tea and Woolong tea with Cleanert TPT and Envi-Carb + PSA SPE showed that average recoveries fell within 70-110% and RSD <20% for 193 and 184 pesticides, respectively, for green tea, accounting for 96.0 and 91.0% of the total number, respectively. GC/MS/MS test results also found 193 and 184 pesticides, respectively, meeting the recovery and RSD conditions, accounting for 96.0 and 91.5%, respectively, of the total number. For Woolong tea samples, GC/MS results showed that with Cleanert TPT and Envi-Carb + PSA SPE for cleanup, there were 192 and 177 pesticides, respectively, meeting the conditions, accounting for 95.5 and 88.1% of the total number, respectively. GC/MS/MS results demonstrated that there were 195 and 184 pesticides, respectively, meeting the conditions, accounting for 97.0 and 91.5% of the total number, respectively. It was seen that Cleanert TPT was superior to Envi-Carb + PSA in cleanup efficiency, whether for green or Woolong tea samples, or GC/MS or GC/MS/MS determination. In Stage III, 61104 results of the average content value of pesticides and RSD (two teas xtwo Youden pair concentrations x two kinds of SPE cartridges x two instruments x 19 tests x 201 pesticides) were derived from the 19 times stability tests over 3 months by paralleling three samples every 5 days via two instruments with two kinds of SPE cartridges for cleanup, respectively, against Youden Pair samples of the 201 incurred pesticides from green and Woolong teas. The statistical analysis found that detected values from the target pesticides of the incurred Youden pair samples showed no marked differences with cleanup by either Cleanert TPT or Envi-Carb + PSA, whether for green or Woolong tea, or G/IMS or G/IM/IMS. The test results using the two aforementioned kinds of SPE cleanup for above 93% pesticides had a tolerance less than 15%, which testifies that both cartridge cleanups met the requirement for pesticide residue analysis.