Residue dissipation and risk assessment of tebuconazole, thiophanate-methyl and its metabolite in table grape by liquid chromatography-tandem mass spectrometry

Sensitive colorimetric and fluorescence dual-mode detection of thiophanate-methyl based on spherical Fe3O4/GONRs composite nanozyme

Pesticide detection based on nanozyme is largely limited in terms of the variety of pesticides. Herein, a spherical and well-dispersed Fe3O4/graphene oxide nanoribbons (Fe3O4/GONRs) composite nanozyme was applied to firstly develop an enzyme-free and sensitive colorimetric and fluorescence dual-mode detection of thiophanate-methyl (TM). The synthesized Fe3O4/GONRs possess excellent dual enzyme-like activities (peroxidase and catalase) and can catalyze H2O2 to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) into oxidized TMB (oxTMB). We found that Fe3O4/GONRs can adsorb TM through the synergistic effect of multiple forces, thereby inhibiting the catalytic activities of nanozyme. This inhibition can modulate the transformation of TMB to oxTMB, producing dual responses of absorbance decrease (oxTMB) and fluorescence enhancement (TMB). The limits of detection (LODs) of TM were 28.1 ng/mL (colorimetric) and 8.81 ng/mL (fluorescence), respectively. Moreover, the developed method with the recoveries of 94.8-100.8% also exhibited a good potential application in the detection of pesticides residues in water and food samples.

Simultaneous determination of four fungicide residues in figs using liquid chromatography tandem mass spectrometry

Dissipative behavior and final residue levels of difenoconazole, prochloraz, propiconazole, and pyraclostrobin in figs were investigated using field trials and laboratory assays. A three-factor, three-level orthogonal test was designed to optimize the pretreatment conditions of the method. A method was established using high-performance liquid chromatography tandem mass spectrometry for the determination of difenoconazole, prochloraz, propiconazole, and pyraclostrobin residues in figs. The limit of quantification for all four targets in figs was 0.002 mg/kg. Difenoconazole, prochloraz, propiconazole, and pyraclostrobin are readily digestible pesticides in figs with half-lives of 6.4, 6.2, 4.8, and 7.9 days, respectively. Residues of difenoconazole, prochloraz, propiconazole, and pyraclostrobin in figs were below the European Union established residue levels of 0.1, 0.03, 0.01, and 0.02 mg/kg, respectively, at day 7 after application. Pyraclostrobin, propiconazole, difenoconazole, and prochloraz were applied twice at doses of 75, 125, 150, and 200 mg a.i./kg at 7-day intervals, and the residues of the four fungicides in figs were acceptable 7 days after the last application. Therefore, the safety interval can be set at 7 days for 70% difenoconazole-prochloraz wettable powder and 40% pyraclostrobin-propiconazole aqueous emulsion according to the protocol.

A highly effective peroxidase-mimic nanozyme of S, N-carbon dot-decorated cerium organic framework-based colorimetric detection of Hg2+ ion and thiophanate methyl

In this study, we proposed a colorimetric probe as S, N-carbon dot-decorated Ce-MOF (S, N-CD@Ce-MOF) for the dual detection of mercury and thiophanate methyl (TM), which are simultaneously present pollutants in the environment and foodstuffs. These pollutants cause serious threats to human health, such as carcinogenicity and neurovirulence. Herein, we synthesized S, N-CD@Ce-MOF using the hydrothermal method and applied it to a "turn-off-on" probe to detect mercury and TM using the colorimetric method in water and food samples. S, N-CD@Ce-MOF shows excellent peroxidase activity by catalyzing the chromogenic substrate of 3,3',5,5'-tetramethylbenzidine (TMB), resulting in deep blue-colored oxidized TMB product (ox TMB) in the presence of H2O2 with a UV absorption wavelength at 654 nm. However, the addition of Hg(II) ions prohibits the oxidation of TMB by an electron transfer effect and easily binds with -S, -N-containing sites on the surface of carbon dots, obstructing the catalytic active sites and decreasing catalytic efficiency with weak UV absorption at 654 nm as a "turn-off". Subsequently, the addition of TM to the above sensing solution as a "turn-on" was triggered by the TM-Hg complex formation and permitted TMB oxidation with a strong absorption peak at 654 nm. Furthermore, this proposed sensor demonstrates a superior linear response to mercury ions and TM in the ranges from 0 to 15 μM and 0 to 14 μM, respectively. The developed colorimetric assay exhibits good sensitivity and selectivity against various possible interferences. Furthermore, we found that the limits of detection for Hg2+ and TM were as low as 0.01 μM and 0.03 μM, respectively. The developed sensor provides various benefits, such as cost-effectiveness, simplicity without a complex detection process, and naked-eye detection. Consequently, our proposed colorimetric technique worked well for the detection of Hg2+ in real water samples and TM in real apple and tomato juice.

Study of pesticide transformation processes in different wheat varieties and their effects on plant metabolism

BACKGROUND

This study aims to obtain systematic understanding of the way by which pesticides are metabolized in plants and the influence of this process on plants' metabolism as this process has a key impact on plant-based food safety and quality. The research was conducted under field conditions, which enabled to capture metabolic processes taking place in plants grown under multihectare cultivation conditions.

RESULTS

Research was conducted on three wheat varieties cultivated under field conditions and treated by commercially available preparations (fungicides, herbicides, insecticides, and growth regulator). Plant tissues with distinctions in roots, green parts, and ears were collected periodically during spring-summer vegetation period, harvested grains were also investigated. Sample extracts were examined by chromatographic techniques coupled with tandem mass spectrometry for: dissipation kinetics study, identification of pesticide metabolites, and fingerprint-based assessment of metabolic changes.

CONCLUSION

Tissue type and wheat varieties influenced pesticide dissipation kinetics and resulting metabolites. Metabolic changes of plants were influenced by type of applied pesticide and its concentration in plants tissues. Despite differences in plant metabolic response to pesticide stress during cultivation, grain metabolomes of all investigated wheat varieties were statistically similar. 4-[cyclopropyl(hydroxy)methylidene]-3,5-dioxocyclo-hexanecarboxylic acid and trans-chrysantemic acid - metabolites of crop-applied trinexapac-ethyl and lambda-cyhalothrin, respectively, were identified in cereal grains. These compounds were not considered to be present in cereal grains up to now. The research was conducted under field conditions, enabling the measurement of metabolic processes taking place in plants grown under large-scale management conditions. © 2024 Society of Chemical Industry.

Metabolic pathway of tebuconazole by soil fungus Cunninghamella elegans ATCC36112

Tebuconazole is the most widely used fungicide in agriculture. Due to its long half-life, tebuconazole residues can be found in the environment media such as in soil and water bodies. Here, the metabolic pathway of tebuconazole was studied in Cunninghamella elegans (C. elegans). Approximately 98% of tebuconazole was degraded within 7 days, accompanied by the accumulation of five metabolites. The structures of the metabolites were completely or tentatively identified by gas chromatography-mass spectrometry (GC-MS) and ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). To identify representative oxidative enzymes that may be involved in the metabolic process, treatment with piperonyl butoxide (PB) and methimazole (MZ) was performed. PB had a strong inhibitory effect on the metabolic reactions, while MZ had a weak inhibitory effect. The results suggest that cytochrome P450 (CYP) and flavin-dependent monooxygenase are involved in the metabolism of tebuconazole. Based on the results, we propose a metabolic pathway for the fungal metabolism of tebuconazole. Data are of interest to gain insight into the toxicological effects of tebuconazole and for tebuconazole bioremediation.

Residue levels and risk assessment of acetamiprid-pyridaben mixtures in cabbage under various open field conditions

Acetamiprid and pyridaben are highly efficient insecticides widely used to protect leafy vegetables against various pests, such as Phyllotreta striolata, but analyses of their residual behaviors applied in mixtures in cabbage fields are primarily lacking. Herein, field trials were performed by spraying 50% acetamiprid-pyridaben wettable powder (50% WP) once at a dose of 150 g of active ingredient per hectare in 12 representative provinces of China under Good Agricultural Practices. The residues of acetamiprid and pyridaben were detected using modified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) and liquid chromatography-tandem mass spectrometry, together with an assessment of their dietary risks. The average recoveries of the two insecticides were 84.6-104%, and the relative standard deviations were 0.898-10.1%. The residual concentrations of acetamiprid and pyridaben at the preharvest interval of 7 days were <0.364 and 0.972 mg/kg, respectively, and less than their maximum residue limits in cabbage (0.5 mg/kg for acetamiprid and 2 mg/kg for pyridaben) in China. The chronic and acute risk values of acetamiprid and pyridaben were 0.0787-33.3%, implying acceptable health hazards to Chinese consumers. In conclusion, applying 50% WP in cabbage fields under Good Agricultural Practices is acceptable. These results provide essential data for using mixtures of acetamiprid and pyridaben in cabbage fields.

Dissipation, residue distribution, and risk assessment of ethiprole and its metabolites in rice under various open field conditions

BACKGROUND

Ethiprole has been registered to control planthoppers in rice fields for many years in Asia. However, its dissipation and residues in rice under natural field conditions and health hazards are largely unclear. In the present study, a modified QuEChERS (i.e. Quick Easy Cheap Effective Rugged Safe) and high-performance liquid chromatography-tandem mass spectrometry method was established to detect ethiprole and its metabolites, ethiprole amide and ethiprole sulfone, in brown rice, rice husks, and rice straw. The field experiments were implemented in 12 representative provinces of China under Good Agricultural Practices aiming to investigate the fate and terminal residues of ethiprole and its metabolites in rice. Finally, the dietary risk of ethiprole was evaluated.

RESULTS

The average recoveries of these analytes in all matrices were 86.4-99.0% with a repeatability of 0.575-9.38%. The limits of quantification for each compound were 0.01 mg kg-1 . Dissipation of ethiprole followed the single first-order, first + first-order, and first-order multi-compartment kinetic models with a half-life of 2.68-8.99 days in rice husks. The dissipation half-life of ethiprole combining all metabolites was 5.20-16.2 days in rice husks. The terminal residues of ethiprole and its metabolites at preharvest intervals of 21 days were < 0.011, 0.25, and 0.20 mg kg-1 in brown rice, rice husks, and rice straw, respectively. Ethiprole amide was undetectable in all matrices, and the risk quotient of ethiprole was far less than 100%.

CONCLUSION

Ethiprole rapidly converted to ethiprole sulfone in rice, and ethiprole and ethiprole sulfone mainly remained in rice husks and straws. The dietary risk of ethiprole was acceptable for Chinese consumers. © 2023 Society of Chemical Industry.

Dissipation Behavior and Dietary Risk Assessment of Thiamethoxam, Pyraclostrobin, and Their Metabolites in Home-Style Pickled Cowpea

In this study, the fate of two pesticides commonly used on cowpeas, thiamethoxam and pyraclostrobin, during the preparation of home-made pickled cowpeas was investigated using an improved QuEChERS method combined with UHPLC-MS/MS. Although pesticide residues were primarily distributed on cowpea samples, some were transferred to brine. The dissipation half-life of thiamethoxam on cowpea samples was significantly shorter than that of pyraclostrobin due to thiamethoxam's higher water solubility. Thiamethoxam demonstrated a half-life of 5.12 ± 0.66 days, whereas pyraclostrobin exhibited a longer half-life of 71.46 ± 7.87 days. In addition, the degradation half-lives of these two pesticides in the whole system (cowpea and brine) were 45.01 ± 4.99 and 70.51 ± 5.91 days, respectively. This result indicates that the pickling did not effectively promote the degradation of thiamethoxam and pyraclostrobin. The metabolite clothianidin of thiamethoxam was not produced throughout the pickling process, but the metabolite BF 500-3 of pyraclostrobin was detected in cowpea samples. The detection rates for thiamethoxam, pyraclostrobin, and BF 500-3 in the 20 market samples were 10%, 70%, and 45%, respectively. However, the risk quotient analysis indicated that the risk of dietary intake of thiamethoxam and pyraclostrobin in pickled cowpeas by Chinese consumers was negligible.

Biotransformation of carbendazim in cowpea pickling process

Carbendazim, a systemic fungicide, is one of the most commonly detected pesticides in cowpeas. Pickled cowpea is a fermented vegetable product with unique flavor favored in China. The dissipation and degradation of carbendazim were investigated in the pickled process. The degradation rate constant of carbendazim in pickled cowpeas was 0.9945 and the half-life of the carbendazim was 14.06 ± 0.82 d. Seven transformation products (TPs) were identified in the pickled process. Furthermore, the toxicity of some TPs show more harmful to three aquatic organisms (TP134) and rats (all the identified TPs) than carbendazim. And most of the TPs posed more development toxicity and mutagenicity than carbendazim. 4 out of 7 TPs were discovered in the real pickled cowpea samples. These results shed light on the degradation and biotransformation of the carbendazim in the pickled process, to better understand the potential health risk of pickled food and evaluate the environmental pollution.

Dissipation, metabolism, accumulation, processing and risk assessment of fluxapyroxad in cucumber and cowpea vegetables from field to table

Understanding the residue fate of fluxapyroxad is critical for food safety and human health. The present study profiled the dissipation, metabolism, accumulation, removal and risk assessment of fluxapyroxad in cucumbers and cowpeas from field to table. Greenhouse-field trials suggested that fluxapyroxad dissipated faster in cucumbers than in cowpeas, and M700F008 was the only detected metabolite at <LOQ-37.92 μg/kg. Fluxapyroxad accumulated in cucumbers (average residue accumulation value, 1: 2.21: 1.16) and cowpeas (1: 1.33: 1.05) after repeated spraying. Peeling, washing and parboiling could remove fluxapyroxad from cucumbers and cowpeas (PF range, 0.16-0.85); however, fluxapyroxad was partly concentrated by stir-frying (PF range, 0.36-1.41). Moreover, fluxapyroxad residues increased with increasing pickling time. Chronic and acute risk assessments revealed that dietary exposure to fluxapyroxad was within the acceptable levels from cucumber and cowpea consumption. Given high residue levels and their potential accumulation, fluxapyroxad should be continuously monitored and assessed in the future.

Impact of technological processes on tebuconazole reduction in selected cereal species and the primary cereal product, and dietary exposure assessment

Contamination of cereals with tebuconazole (TEB) can affect the dietary risk assessment. This study investigates, for the first time, how mechanical, thermal, physical-chemical, and biochemical processes affect the TEB level in wheat, rye, and barley. The biochemical process of malting was the most effective for tebuconazole reduction (by 86%) in cereals. Thermal processes were also effective, i.e., boiling (70%) and baking (55%). These processes considerably decreased the concentration of tebuconazole, and Procesing Factors (PFs) were from 0.10 to 0.18 (malting), 0.56 to 0.89 (boiling), and 0.44 to 0.45 (baking), respectively. The concentration of TEB was not reduced after the application of mechanical processing. The risk was estimated in dietary exposure assessment on the basis of the highest reported levels of tebuconazole residues bread. At a high level of rye bread consumption, the potential exposure to tebuconazole reached only 3.5% and 2.7% in children and adults, respectively.

Dissipation and dietary exposure risk assessment of pyraclostrobin, fluxapyroxad, difenoconazole, and azoxystrobin in the Fritillaria field ecosystem

Fritillaria (Beimu in Chinese) is a well-known traditional Chinese medicinal herbal and valuable health food, which has attracted more and more attention. In this study, an efficient method was developed to determine pyraclostrobin, fluxapyroxad, difenoconazole, and azoxystrobin in plants, fresh Fritillaria, dry Fritillaria, and soil via liquid chromatography-tandem mass spectrometry. The average recoveries of the method were 78.9-109.7% with relative standard deviations of 0.94-11.1%. The dissipation half-lives of the four fungicides were 4.4-7.7 days in the Fritillaria plant and 11.6-18.2 days in the soil. The terminal residues of four fungicides were 0.033-0.13 mg/kg in fresh Fritillaria, 0.096-0.42 mg/kg in dry Fritillaria, and 0.12-0.74 mg/kg in soil. In the risk assessment of dietary exposure, all the chronic hazard quotient and acute hazard quotient index values were far below 100%, which were both acceptable to consumers. Accordingly, 7 days was recommended as the pre-harvest interval for the four fungicides in Fritillaria. This work could guide the safe use of these fungicides in Fritillaria and also give a reference for the Chinese government to establish the maximum residue limits (MRLs).

Modern Analytical Methods for the Analysis of Pesticides in Grapes: A Review

Currently, research on the determination of pesticides in food products is very popular. Information obtained from research conducted so far mainly concerns the development of a methodology to determine the content of pesticides in food products. However, they do not describe the content of the pesticide used in viticulture in the resulting product. Over the past decade, this study has examined analytical methodologies for assessing pesticide residues in grapes. Scopus, Web of Science, Science Direct, PubMed, and Springer databases were searched for relevant publications. The phrases “pesticides” and “grapes” and their combinations were used to search for articles. The titles and annotations of the extracted articles have been read and studied to ensure that they meet the review criteria. The selected articles were used to compile a systematic review based on scientific research and reliable sources. The need to study the detection of pesticide residues in grapes using advanced analytical methods is confirmed by our systematic review. This review also highlights modern methods of sample preparation, such as QuEChERS, SPME, PLE, dLLME, and ADLL-ME, as well as the most used methods of separation and identification of pesticides in grapes. An overview of the countries where residual grape pesticide amounts are most studied is presented, along with the data on commonly used pesticides to control pests and diseases in grape cultivation. Finally, future possibilities and trends in the analysis of pesticide residues in grapes are discussed by various analytical methods.

Residue analysis and dietary risk assessment of tebuconazole in loquat and sugarcane after open-field application in China

Tebuconazole is an effective but potentially carcinogenic fungicide. Tebuconazole residues in loquat and sugarcane were investigated, together with an analysis of their dietary risk. Solid-phase extraction and high-performance liquid chromatography-tandem mass spectrometry showed fortified recoveries of 87% to 98%, with standard deviations ≤ 6.4%. The tebuconazole residues were below 6.34 mg kg^-1 for whole loquat and 0.80 mg kg^-1 for sugarcane. Based on the final residue test, the chronic hazard index was 90.74% in whole loquat and sugarcane, while the acute hazard index ranged from 66.32% to 109.49% for loquat and 33.37% to 76.93% for sugarcane. The assessment of potential dietary risk showed that while loquats may represent an acute risk to human health, whereas sugarcane consumption was safe. A 21-day pre-harvest interval is proposed to comply with maximum residue limit regulations and the observed risks when using 430 g/L tebuconazole for treating sugarcane. These findings offer guidance for tebuconazole formulation and use.

Smart MOF-on-MOF Hydrogel as a Simple Rod-shaped Core for Visual Detection and Effective Removal of Pesticides

The immoderate use of pesticides in the modern agricultural industry has led to the pollution of water resources and ultimately threatens the human body. Herein, two metal-organic frameworks (MOFs), namely {[Zn(tpt)₂ ·2H₂ O]}_n (Zn1) and {[Zn₂ (tpt)₂ (bdc)]}_n (Zn2), (Htpt = 5-[4(1H-1,2,4-triazol-1-yl)]phenyl-2H-tetrazole), respectively, are constructed as smart materials for visual and on-site detection of pesticides and their removal from water. The exposed nitrogen-rich sites and high chemical stability make Zn2 a self-assembly core to further fabricate MOF-on-MOF-sodium alginate (ZIF-8-on-Zn2@SA) composite by wrapping ZIF-8 on the outside surface. Inheriting the excellent fluorescent emission of Zn2, the rod-like ZIF-8-on-Zn2@SA module exhibits naked-eye detection of thiophanate-methyl (TM) in real fruits and vegetables with a broad linear range (10-100 × 10^-6  m), a low limit of detection (LOD = 0.14 × 10^-6  m), and satisfactory recoveries (98.30-102.70%). In addition, carbendazim (CBZ), the metabolite of TM after usage in crops, can be efficiently removed from water by the ZIF-8-on-Zn2@SA (q_max  = 161.8 mg g^-1 ) with a high correlation coefficient (R²  > 0.99). Therefore, the portable ZIF-8-on-Zn2@SA sensing platform presents a promising candidate for monitoring and removal of pesticides, especially suitable for regions with serious pesticide environmental pollution.

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.

Evaluation of the cytotoxic and genotoxic potential of the captan-based fungicides, chlorothalonil-based fungicides and methyl thiophanate-based fungicides in human fibroblasts BJ

The objectives of this study were to examine cytotoxic and genotoxic damage in human BJ fibroblasts caused by three pesticides used worldwide by trypan blue dye exclusion assays and to measure the relative level of phosphorylated histone H2A.X by flow cytometry at different concentrations. Captan-based fungicide and methyl thiophanate-based fungicide (100 and 1000 µΜ) showed immediate cytotoxic effects; furthermore, after 24 h, captan-based fungicide, chlorothalonil-based fungicide and methyl thiophanate-based fungicide caused cytotoxic effects in the concentration ranges of 40-100 µM, 30-100 µM and 150-1000 µM, respectively. All fungicides generated DNA damage in the treated cells by activating ATM and H2A.X sensor proteins. The three fungicides tested generated DNA double-stranded breaks and showed cytotoxicity at concentrations 33, 34, and 5 times lower (captan, chlorothalonil and thiophanate-methyl respectively) than those used in the field, as recommended by the manufacturers.

Tebuconazole induces liver injury coupled with ROS-mediated hepatic metabolism disorder

Tebuconazole, the most widely used fungicide, is reported to cause various environmental problems and have serious health risks in humans. Despite numerous advances in toxicity studies, its internal metabolic process and the underlying mechanisms have not been systemically studied. The present study administered low doses (0.02 g/kg bw and 0.06 g/kg bw) of tebuconazole to C57BL/6 mice in vivo. The high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed and validated to analyze the tebuconazole in different organs, and our data revealed that tebuconazole mainly accumulated in the liver and that histopathological damage were exhibited in this organ. Tebuconazole significantly dysregulated phase Ⅰ- and phase II-metabolizing enzymes, ATP-binding cassette (ABC) efflux transporters (Abcc2 and Abcc3) and fatty acid metabolism-related genes (Cdkn1a and Fasn), thereby directly causing liver hypertrophy and steatosis. Importantly, the excessive induction of reactive oxygen species (ROS) and oxidative stress partially accounted for the metabolic abnormalities mediated by tebuconazole. Moreover, these alterations were related to the abnormal transcriptional levels of peroxisome proliferator-activated receptor α (PPAR-α) and liver x receptor α (LXR-α), which were predicted to bind to tebuconazole via hydrogen bonding interactions. The current findings provide new insight into the molecular mechanisms of metabolic abnormalities induced by tebuconazole at low concentration, and are conducive to a better understanding of the environmental risk posed by this fungicide.

Personal exposure assessment of pesticides in residents: The association between hand wipes and urinary biomarkers

BACKGROUND

Residential exposure to pesticides may occur via inhalation of airborne pesticides, direct skin contacts with pesticide-contaminated surfaces, and consumption of food containing pesticide residues. The aim was to study the association of dermal exposure to pesticides between the use and non-use periods, between farmer and non-farmer families and between dermal exposure and the excretion of metabolites from urine in residents living close to treated agricultural fields.

METHODS

In total, 112 hand wipes and 206 spot urine samples were collected from 16 farmer and 38 non-farmer participants living within 50 m from an agricultural field in the Netherlands. The study took place from May 2016 to December 2017 during the use as well as the non-use periods of pesticides. Hand wipes were analysed for the parent compound and urines samples for the corresponding urinary metabolite of five applied pesticides: asulam, carbendazim (applied as thiophanate-methyl), chlorpropham, prochloraz and tebuconazole. Questionnaire data was used to study potential determinants of occurrence and levels of pesticides in hand wipes according to univariate and multivariate analysis.

RESULTS

Carbendazim and tebuconazole concentrations in hand wipes were statistically significantly higher in the pesticide-use period compared to the non-use period. In addition, especially during the use periods, concentrations were statistically significantly higher in farmer families compared to non-farmer families. For asulam, chlorpropham and prochloraz, the frequency of non-detects was too high (57-85%) to be included in this analysis. The carbendazim contents in urine samples and hand wipes were correlated on the first and second day after taking the hand wipe, whereas chlorpropham was only observed to be related on the second day following the spray event.

CONCLUSIONS

Concentrations in hand wipes were overall higher in pesticide use periods compared to non-use periods and higher in farmer families compared to non-farmer families. Only for carbendazim a strong correlation between concentrations in hand wipes and its main metabolite in urine was observed, indicating dermal exposure via contaminated indoor surfaces. We expect this to be related to the lower vapour pressure and longer environmental lifetime of carbendazim compared to the other pesticides studies.

Potential effects of Rhodococcus qingshengii strain djl-6 on the bioremediation of carbendazim-contaminated soil and the assembly of its microbiome

As a widely used fungicide, the environmental fate of carbendazim and its residues in agricultural products have caused great concern. However, its effects on soil microbial communities are largely unknown. Herein, we used high-throughput sequencing to reveal the effects of high and low dose of carbendazim and its degrading strain, Rhodococcus qingshengii strain djl-6, on the composition, diversity, and interrelationship of soil bacterial and fungal communities in short- and medium-term under laboratory conditions. The results showed that carbendazim exhibited an increased negative impact on bacterial communities and reduced the proportion of dominant fungal phylum Ascomycota during a 14-day incubation period. Only the impacts of low-dose carbendazim (2 mg·kg^-1 dry soil) on fungal community were weakened. Network analysis showed that carbendazim increased the connectivity and modularity of microbial co-occurrence networks. Strain djl-6 exhibited good potential for bioremediation of carbendazim-contaminated soils. Moreover, it driven the assembly of potential carbendazim-degrading consortia from indigenous microbial communities; and members of the genera Arthrobacter, Bacillus, Brevundimonas, Lysinibacillus, Massilia, Mycobacterium, Paenibacillus, and Pseudarthrobacter might be participated in the degradation of carbendazim. Taken together, our study provides a relatively comprehensive understanding of the effects of carbendazim and its degrading strain djl-6 on soil microbial communities.

Tebuconazole induced cytotoxic and genotoxic effects in HCT116 cells through ROS generation

Tebuconazole (TEB) is a common triazole fungicide that has been widely used for the control of plant pathogenic fungi, suggesting that mammal exposure occurs regularly. Several studies demonstrated that TEB exposure has been linked to a variety of toxic effects, including neurotoxicity, immunotoxicity, reprotoxicity and carcinogenicity. However, there is a few available data regarding the molecular mechanism involved in TEB-induced toxicity. The current study was undertaken to investigate the toxic effects of TEB in HCT116 cells. Our results showed that TEB caused cytotoxicity by inhibiting cell viability as assessed by the MTT assay. Furthermore, we have demonstrated that TEB induced a significant increase in the reactive oxygen species (ROS) production leading to the induction of lipid peroxidation and DNA fragmentation and increased superoxide dismutase (SOD) and catalase (CAT) activities. Moreover, TEB exposure induced mitochondrial membrane potential loss and caspase-9/-3 activation. Treatment with general caspases inhibitor (Z-VAD-fmk) significantly prevented the TEB-induced cell death, indicating that TEB induced caspases-dependent cell death. These findings suggest the involvement of oxidative stress and apoptosis in TEB-induced toxicity in HCT116.

Study on degradation behaviour, residue distribution, and dietary risk assessment of propiconazole in celery and onion under field application

BACKGROUND

Propiconazole is widely used to control fungal diseases in field crops, including celery and onion. The potential risk to the environment and human health has aroused much public concern. Therefore, it is significant to investigate the degradation behaviour, residue distribution, and dietary risk assessment of propiconazole in celery and onion.

RESULTS

A sensitive analytical method for determination of propiconazole residue in celery and onion was established and validated through high-performance liquid chromatography tandem mass spectrometry. The average recovery rate of propiconazole ranged from 85.7% to 101.8%, with a relative standard deviation of 2.1-6.3%. For the dissipation kinetics, the data showed that propiconazole in celery and onion was degraded, with half-lives of 6.1-6.2 days and 8.7-8.8 days respectively. In the terminal residue experiments, the residues of propiconazole were below 4.66 mg kg^-1 in celery after application two or three times and were below 0.029 mg kg^-1 in onion after application of three or four times with an interval of 14 days under the designed dosages. The chronic and acute dietary exposure assessments for propiconazole were valued by risk quotient, with all values being lower than 100%.

CONCLUSION

Propiconazole in celery and onion was rapidly degraded following first-order kinetics models. The dietary risk of propiconazole through celery or onion was negligible to consumers. The study not only offers a valuable reference for reasonable usage of propiconazole on celery and onion, but also facilitates the establishment of maximum residue limits in China. © 2020 Society of Chemical Industry.

Simultaneous determination, dissipation and decontamination of fungicides applied on cabbage using LC-MS/MS

A method for simultaneous determination of carbendazim and tebuconazole residues in cabbage was developed and validated in LC-MS/MS. Samples were extracted and purified following the modified QuEChERS procedure, which enabled the elution of carbendazim and tebuconazole at 0.96 and 5.31 min, respectively. LOD and LOQ were 0.0005 and 0.0015 mg kg^-1, respectively. Mean recovery was in the range of 78.94 to 104.89% for carbendazim and 76.07 to 98.62% for tebuconazole. The field samples recorded residues of 0.274 and 0.481 mg kg^-1; and 0.194 and 0.392 mg kg^-1 at single and double dose for carbendazim and tebuconazole, respectively. Half-life values were 2.17 and 2.99 for carbendazim and 2.74 and 2.81 for tebuconazole at single and double dose, respectively. Decontamination with saltwater wash followed by cooking and lemon water wash found superior in the removal of residues more than 90%.

Portable and quantitative detection of carbendazim based on the readout of a thermometer

The detection of carbendazim (CBZ) is important for food safety and human health. However, most current analytical methods require large instruments and highly trained operators. In order to solve this problem, herein, an innovative portable and quantitative photothermal assay platform relying on a thermometer readout for the detection of CBZ has been developed. Gold nanoparticles (AuNPs), which exhibit a strong distance-dependent photothermal effect under specific laser irradiation, were utilized as indicators. The CBZ aptamer was introduced to protect AuNPs from salt-mediated aggregation. When CBZ is present, the binding event between CBZ and aptamer leads to the loss of the aptamer protective effect on AuNPs, and AuNP aggregation occurs. Under 650-nm laser irradiation, the increase in temperature associated with an AuNP-dependent photothermal effect is highly related to the CBZ concentration. Having the advantages of user-friendliness, low cost, quick response, and portability, this method has great potential for on-site applications.

Colourimetric Detection of Tebuconazole in Aqueous Solution Based on an Unmodified Aptamer and the Aggregation of Gold Nanoparticles

This paper illustrates the establishment of a colourimetric method for detection of the fungicide tebuconazole (TEB) in aqueous samples based on an unmodified TEB-specific aptamer and gold nanoparticles (AuNPs). In the absence of TEB, the AuNPs are coated with a TEB-specific aptamer and then stably dispersed a NaCl solution of high concentration, leading to a red solution and producing a maximum UV absorption peak at 520 nm. In the presence of TEB, due to the specific high affinity between TEB and the TEB-specific aptamer, the aptamer combines with TEB to form stable compounds, causing the AuNPs to be exposed in the solution and aggregate. The aggregated AuNPs turn the solution from red to blue, presenting a maximum UV absorption peak at 650 nm. Therefore, the concentration of TEB in the system can be quantitatively detected through the changes in absorbance. This TEB selective colourimetric biosensor detects TEB over a linear concentration range of 20 to 400 nM (R = 0.99385) and has a limit of detection (LOD) of 4.13 nM. The average recovery of TEB is 94.9–104.8 % in the application of actual water samples with the relative standard deviations (RSD) ranging from 1.01 to 5.34 %. With considerable sensitivity and selectivity, this aptasensor indicates great potential for TEB detection in aqueous samples.

Dissipation behavior of thiophanate-methyl in strawberry under open field condition in Egypt and consumer risk assessment

Thiophanate methyl is a broad-spectrum benzimidazole fungicide extensively applied in pre- and post-harvest, for the control of a wide range of fruit and vegetable pathogens. In the current work, the residue behavior of thiophanate methyl after application on strawberries and an estimation of the consumer dietary exposure was performed. Supervised field trials were conducted in Egypt (Qaluobiya Governorate) as to investigate the residue dynamics and terminal residues at different PHIs of thiophanate methyl and its metabolite carbendazim in strawberries under Egyptian conditions. For the measurement of residues in fruits, a QuEChERS-based protocol coupled with LC-MS/MS was optimized and successfully validated at 0.01 mg kg^-1. The half-life (t_1/2) of thiophanate methyl in strawberries was estimated, and a dietary risk assessment was performed employing both FAO/WHO and EFSA approaches.

A novel thioctic acid-carbon dots fluorescence sensor for the detection of Hg2+ and thiophanate methyl via S-Hg affinity

Mercury ions and thiophanate methyl (TM), are common contaminants present in the environment and food products. These contaminants cause neurovirulence and carcinogenicity effect on the human body. Herein, thioctic acid-carbon dots (SCDs) was synthesized and applied in a fluorescent "turn-off-on" probe to detect Hg²⁺ and TM. The presence of other common metal ions and pesticides did not affect the response of the developed sensor. Further investigation revealed that the fluorescent "turn-off-on" model were static, wherein the "turn-off" was induced by an electron transfer effect, while the "turn-on" was caused by the formation of TM-Hg complexes. Under optimal conditions, the fluorescence sensor method exhibited limits of detection as low as 33.3 nmol/L and 7.6 nmol/L for Hg²⁺ and TM, respectively. The developed sensor was designed to detect Hg²⁺ and TM in real tap water, grape juice and Citri Reticulatae Pericarpium (CRP) water samples.

Dissipation, Processing, Leaching, and Safety Evaluation of Flonicamid and Its Metabolites in Tea

BACKGROUND

Tea is a popular traditional non-alcoholic beverage worldwide. Flonicamid is a selective systemic pyridine carboxamide insecticide that is widely used for controlling tea leafhopper in tea.

OBJECTIVE

The leaching rates, dissipation dynamics, and residue levels of flonicamid and its metabolites in tea leaves during processing and transferring were investigated to validate the safe risk in tea and transfer behavior using high performance liquid chromatography-tandem mass spectrometry with a convenient pretreatment method.

METHOD

The extracting method and immersion rate experiments were optimized by single factor analysis and orthogonal tests. The acetonitrile extracting solvent with 0.5% formic acid was used and optimal leaching conditions were obtained with a regime of 15 min immersion time, 100°C temperature, three immersions and a tea-to-water ratio of 1:50.

RESULTS

Average recoveries in processed green tea and infusions were 80.85-98.75% with relative standard deviations <5.87%. LODs and LOQs of flonicamid, 4-trifluoromethylnicotinic acid (TFNA), N-(4-trifluoromethylnicotinoyl) glycine (TFNG), and 4-trifluoromethylnicotinamide (TFNA-AM) were 0.0013-0.350 and 0.004-1 μg/g, respectively. The processing factor of flonicamid was 0.36-5.52 during green tea manufacture. The leaching rates were 22.9-97.4% from processed tea to infusion.

CONCLUSIONS

The risk of long-term and short-term dietary intake of flonicamid was safe in tea infusions with the risk quotient (RQ) values <1 for the Chinese consumer. This work may provide guidance for safe and reasonable consumption of flonicamid in tea in China.

HIGHLIGHTS

The suitable leaching factors of flonicamid and its metabolites in tea infusions were optimized by orthogonal experimentation for the first time.

Chromatographic Methods for Detection and Quantification of Carbendazim in Food

Carbendazim (CBZ), which is a fungicide widely used for the management of plant diseases, has been detected in a number of food products. The negative effects of CBZ to human health have stimulated the reduction of the maximum residue limits (MRLs), and subsequently the development of reliable and sensitive detection methods. Here, we are reviewing for the first time all reported chromatographic methods for the detection and quantification of CBZ in food. Several techniques, including liquid chromatography (LC), thin layer chromatography (TLC), micellar electrokinetic chromatography (MEKC), and supercritical fluid chromatography (SFC), were used for the separation and detection of CBZ, showing diverse characteristics and sensitivity. Some methods allowed the specific determination of CBZ, whereas other methods were successfully applied for the simultaneous quantification of a huge number of pesticides. Most reported methods showed limits of detection (LOD) and quantification (LOQ) lower than the MRLs. Relevant efforts in the field have been directed toward the simplification and optimization of the extraction steps prior to the chromatographic separation to increase the recovery and reduce the matrix effects. In this Review, the matrices, extraction procedures, and separation and detection parameters are detailed and compared in order to provide new insights on the development of new reliable methods for the detection of CBZ in food.

In vitro assessment of pesticide residues bioaccessibility in conventionally grown blueberries as affected by complex food matrix

The aim of this study was to investigate the bioaccessibility of pesticide residues in blueberries (commercial and sample from controlled field trial) from Serbia, involving the presence of a complex food matrix and to assess the potential risk to human health. The presence of nine active substances (azoxystrobin, boscalid, fludioxonil, cyprodinil, pyrimethanil, pyridaben, pyriproxyfen, acetamiprid and thiametoxam) in initial blueberry samples was determined in concentration range from 5.15 μg/kg for thiametoxam to 187 μg/kg for azoxystrobin. Clothianidin, metabolite of thiametoxam, was not detected in any blueberry sample. However, after in vitro digestion, the content of initially detected pesticides residues was significantly decreased or it was below limit of quantification resulting in the total bioaccessibility of about 15%. Azoxystrobin, pyrimethanil and fludioxonil was quantified in digestive juice at concentrations which were about 81%, 37% and 10% less than the inital concentration, respectively. The presence of food matrix during digestion of blueberries even more severely reduced concentration of pesticide residues (total bioaccessibility was about 7%) compared to digestion without the food matrix. Only azoxystrobin was quantified after digestion with food matrix in concentration of 27 μg/kg in sample from controlled field trial and detected in two commercial samples but below the limit of quantification. Furthermore, chronic risk assessment indicated that risk is acceptable for the health of different human subpopulation groups. The current study on pesticides residues, most commonly applied on blueberries, provides for the first time an insight into their bioaccessibility under conditions that mimic physiological environment of human digestive tract.

Thiophanate-methyl induces severe hepatotoxicity in zebrafish

Thiophanate-methyl (TM) is widely used all over the world and is a typical example of pesticide residues, which can be detected in the soil, and even in vegetables and fruits. However, the molecular mechanisms underlying the hepatotoxicity of TM are not well understood. In this study, we utilized zebrafish to comprehensively evaluate the hepatotoxicity of TM and explore how the molecular mechanisms of hepatotoxicity are induced. The zebrafish larvae were exposed in 6.25, 12.5 and 25 mg/L TM from 72 to 144 hpf, while the adults were exposed in 2, 4 and 6 mg/L TM for 28 days. Here, we found that 12.5 and 25 mg/L TM induces specifically serious hepatotoxicity but not the toxicity of other organs in zebrafish larvae and adults. Moreover, it might triggered hepatotoxicity by activating the caspase-3 through apoptotic pathways and oxidative stress in zebrafish. Subsequently, this resulted in a metabolic imbalance in the zebrafish's liver. In conclusion, our results disclosed the fact that TM may induce severe hepatotoxicity by mediating activation of caspase-3 and oxidative stress in zebrafish.

Residues and Dietary Risk Assessments of 2,4-D Isooctyl Ester, Metribuzin, Acetochlor, and 2-Ethyl-6-methylaniline in Corn or Soybean Fields

Since 2,4-dichlorophenoxy acetic acid (2,4-D) was discovered in the 1940s, 2,4-D and its derivatives remain among most commonly used herbicides in the world. There have been recent increases in using 2,4-D products in a combination with other herbicides such as metribuzin and acetochlor to control noxious weeds. However, accurate analysis of 2,4-D isooctyl ester remains to be improved due to long analysis time and rapid conversion of the ester to acid (i.e., under-reporting residues). In this work, a simple hydrolysis procedure was introduced to provide a quantitative hydrolytic rate of the ester (>95%) and did not affect the other pH-sensitive compounds. Analysis parameters and sample pretreatments were optimized for improved selectivity and accuracy. The hydrolysis-QuEChERS (quick, easy, cheap, effective, rugged, and safe) technique for multidetermination of 2,4-D isooctyl ester, metribuzin, acetochlor, and 2-ethyl-6-methylaniline in corn and soybeans via high performance liquid chromatography-tandem mass spectrometry was established. The method had average recoveries of 74-109% with relative standard deviations ≤13.5% and limits of quantifications (LOQs) of 0.05 mg/kg. The terminal residues of these compounds found in real edible matrixes were less than the corresponding LOQs at harvest time. The risk quotients were far below 100%, indicating a low health risk to consumers.

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 and Risk Assessment of Multiresidual Fungicides in Grapes under Field Conditions

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

QuEChERS - Fundamentals, relevant improvements, applications and future trends

The Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method is a simple and straightforward extraction technique involving an initial partitioning followed by an extract clean-up using dispersive solid-phase extraction (d-SPE). Originally, the QuEChERS approach was developed for recovering pesticide residues from fruits and vegetables, but rapidly gained popularity in the comprehensive isolation of analytes from different matrices. According to PubMed, since its development in 2003 up to November 2018, about 1360 papers have been published reporting QuEChERS as extraction method. Several papers have reported different improvements and modifications to the original QuEChERS protocol to ensure more efficient extractions of pH-dependent analytes and to minimize the degradation of labile analytes. This analytical approach shows several advantages over traditional extraction techniques, requiring low sample and solvent volumes, as well as less time for sample preparation. Furthermore, most of the published studies show that the QuEChERS protocol provides higher recovery rate and a better analytical performance than conventional extraction procedures. This review proposes an updated overview of the most recent developments and applications of QuEChERS beyond its original application to pesticides, mycotoxins, veterinary drugs and pharmaceuticals, forensic analysis, drugs of abuse and environmental contaminants. Their pros and cons will be discussed, considering the factors influencing the extraction efficiency. Whenever possible, the performance of the QuEChERS is compared to other extraction approaches. In addition to the evolution of this technique, changes and improvements to the original method are discussed.

Dissipation behavior and dietary risk assessment of lambda-cyhalothrin, thiamethoxam and its metabolite clothianidin in apple after open field application

The dissipation dynamics and residue amounts of lambda-cyhalothrin, thiamethoxam and clothianidin in apple were investigated by using rapid resolution liquid chromatography triple quadrupole mass spectrometer (RRLC-MS/MS) and gas chromatography mass spectrometry (GC-MS). The developed method performed satisfactory recoveries of 88%-105% and the limit of quantitation (LOQ) was 0.01 mg kg^-1. The suspension concentrate (SC) formulation of lambda-cyhalothrin and thiamethoxam was applied on apple field in accordance with good agricultural practice (GAP). The half-lives of two pesticides ranged from 7.01 d to 17.3 d and the terminal residues were <0.01-0.21 mg kg^-1. Based on the Chinese dietary pattern, the dietary risk of lambda-cyhalothrin and total thiamethoxam were predicted by comparing intake amounts with the toxicological data, namely acceptable daily intake (ADI) and acute reference dose (ARfD). The chronic and acute risk quotients were 0.1080-0.4463 and 0.0008-0.2005, respectively, which showed negligible risk for general consumers. The pre-harvest interval (PHI) of 21 d was suggested for the formulation in compliance with maximum residue limit (MRL) and dietary risk assessment, meanwhile, the MRL of 0.1 mg kg^-1 was recommended for thiamethoxam in apple. These results were vital for guiding reasonable usage of two insecticides and for approval of formulation use.

Analysis of the dissipation kinetics of thiophanate-methyl and its metabolite carbendazim in apple leaves using a modified QuEChERS-UPLC-MS/MS method

As one of the main fungicides for the apple leaf disease control, thiophanate-methyl (TM) mainly exerts its fungicidal activity in the form of its metabolite carbendazim (MBC), whose dissipation kinetics is very distinct from that of its parent but has been paid little attention. The aim of this work was to investigate the dissipation kinetics of TM and its active metabolite MBC in apple leaves using a modified QuEChERS-UPLC-MS/MS method. The results showed that TM and MBC could be quickly extracted by this modified QuEChERS procedure with recoveries of 81.7-96.5%. The method linearity was in the range of 0.01-50.0 mg kg^-1 with the quantification limit of 0.01 mg kg^-1 . Then this method was applied to the analysis of fungicide dissipation kinetics in apple leaves. The results showed that the dissipation kinetics of TM for the test in 3 months can be described by a first-order kinetics model with a DT₅₀ (dissipation half-life) range of 5.23-6.03 days and the kinetics for MBC can be described by a first-order absorption-dissipation model with the T_max (time needed to reach peak concentration) range of 4.78-7.09 days. These models can scientifically describe the behavior of TM and MBC in apple leaves, which provides necessary data for scientific application.