Dissipation, Processing Factors and Dietary Risk Assessment for Flupyradifurone Residues in Ginseng

Residue Patterns and Dietary Risk Assessment of Picarbutrazox and Its Metabolite TZ-1E in a Ginseng Planting System

This study established a simple, sensitive, and rapid method for the residual analytical method of picarbutrazox and its metabolites (E)-picarbutrazox (TZ-1E) in ginseng plants, fresh ginseng, and dried ginseng. The samples were extracted and purified using an improved QuEChERS method and determined by HPLC-MS/MS. The linear relationship of the method was good (R2 ranging from 0.9935 to 0.9999), the limit of detection was 7.19 × 10-5 to 1.65 × 10-3 ng, the limit of quantitation was 0.01 mg/kg, the intra- and interday addition recovery rates ranged from 87.33 to 107.2%, and the relative standard deviation range was 0.58-8.21%. This method was applied to detect residual samples in the field. The results showed that the degradation of picarbutrazox in ginseng plants followed first-order kinetic equations; the R2 values were 0.9293 and 0.9430, and the half-lives (t1/2) were 8.24 and 11.5 d, respectively. It was an easily degradable pesticide (t1/2 < 30 d). The final residual levels of picarbutrazox in ginseng plants, fresh ginseng, and dried ginseng ranged from 0.0184 to 19.223 mg/kg. A dietary risk assessment was conducted based on the final residual levels of picarbutrazox in fresh and dried ginseng, and the results showed that the chronic exposure risk quotient values of both fresh and dried ginseng were less than 100% (0.1303% for both fresh and dried ginseng). This indicated that the dietary risk of using 10% picarbutrazox suspension concentrate in ginseng was very low and did not pose an unacceptable risk to public health. The results of this study can provide a basis for the development of maximum residue limit for picarbutrazox in ginseng.

Dissipation and Risk Assessment of Propaquizafop in Ginseng under Field Conditions

Propaquizafop is a highly efficient aryloxy phenoxy propionate chiral herbicide. However, the use of propaquizafop, including its safe use methods, residue patterns, dietary risk assessment, and maximum residue limits, for ginseng, a traditional Chinese medicinal plant, has not been studied. An analytical method was established for the simultaneous determination of propaquizafop and its four metabolites in ginseng soil, fresh ginseng, ginseng plant, and dried ginseng using HPLC-MS/MS. This approach showed good linearity (R2 ranging from 0.9827 to 0.9999) and limit of quantification ranging from 0.01 to 0.05 mg/kg. The intra- and interday recovery rates of this method ranged from 71.6 to 107.1% with relative standard deviation ranging from 1.3 to 23.2%. The method was applied to detect residual samples in the field, and it was found that the degradation of propaquizafop in ginseng plants and soil followed a first-order kinetic equation. R2 was between 0.8913 and 0.9666, and the half-life (t1/2) ranged from 5.04 to 8.05 days, indicating that it was an easily degradable pesticide (T1/2 < 30 days). The final propaquizafop residues in ginseng soil, plants, fresh ginseng, and dried ginseng ranged from 0.017 to 0.691 mg/kg. A dietary risk assessment was conducted on the final propaquizafop residue in fresh and dried ginseng. The results showed that the chronic exposure risk quotient values were less than 100% for fresh and dried ginseng (1.15% for fresh ginseng and 1.13% for dried ginseng). This illustrates that the dietary risk associated with the use of 10% propaquizafop emulsifiable concentrate in ginseng is very low. Thus, applying 750 mL/ha of propaquizafop on ginseng could not pose an unacceptable risk to public health. The results of the present study support the registration of propaquizafop in ginseng.

Residue analysis and dietary risk assessment of abamectin in fresh corn, bitter melon, and Fritillaria

To clarify the residue behavior and possible dietary risk of abamectin in fresh corn, bitter melon, and Fritillaria, a method was developed for the simultaneous determination of abamectin residues in fresh corn, bitter melon, and Fritillaria by QuEChERS (quick, easy, cheap, effective, rugged, safe) ultra-performance liquid chromatography-tandem mass spectrometry. The mean recovery of abamectin in fresh corn, bitter melon, and Fritillaria was 86.48%-107.80%, and the relative standard deviation was 2.07%-10.12%. The detection rates of abamectin residues in fresh corn, bitter melon, and Fritillaria were 62.50%, 87.50%, and 80.00%, respectively. The residues of abamectin in fresh corn, bitter melon, and Fritillaria were not more than 0.020, 0.019, and 0.087 mg/kg, respectively. Based on these results, dietary risk assessment showed that the risk content of abamectin residues in long- and short-term dietary exposure for Chinese consumers was 61.57% and 0.41%-1.11%, respectively, indicating that abamectin in fresh corn, bitter melon, and Fritillaria in the market would not pose a significant risk to consumers.

Toxicity risk assessment of flupyradifurone for the predatory pirate bug, Orius strigicollis (Poppius) (Heteroptera: Anthocoridae), a biological control agent of Diaphorina citri Kuwayama (Hemiptera: Liviidae)

Diaphorina citri Kuwayama (Hemiptera: Liviidae), commonly known as the Asian citrus psyllid, is a prominent citrus tree pest that serves as a vector for Asian huanglongbing (HLB). The substantial costs incurred by the citrus industry as a consequence of this disease have spurred considerable interest in the combined control of D. citri using insecticides and natural enemies. However, the successful implementation of such integrated pest management strategies is dependent on ensuring the compatibility of using natural enemies in the presence of insecticides. In this regard, we evaluated the lethal and sublethal effects of flupyradifurone on Orius strigicollis (Poppius) (Heteroptera: Anthocoridae), an important predatory biological control agent, in which we assessed the risk of exposure to flupyradifurone under both in- and off-field scenario. The median lethal rate (LR50) value of flupyradifurone against O. strigicollis (9.089 g a.i. ha-1), was found to be significantly lower than the maximum field recommended rate (MFRR, 170 g a.i. ha-1). Additionally, at 0.254 g a.i. ha-1, flupyradifurone was established to significantly prolong the developmental duration of O. strigicollis from the first to third instar nymphs. Although we detected no significant difference in the survival of immature O. strigicollis subjected to 0.064 g a.i. ha-1 and control treatments, survival was significantly lower in 0.127 and 0.254 g a.i. ha-1 treatments. Moreover, whereas there were no significant differences in adult longevity between the 0.127 g a.i. ha-1 and control treatments, we recorded a significant reduction in fecundity. Furthermore, there were reductions in peak life expectancy, reproductive value, finite rate of increase, intrinsic rate of increase, and net reproduction rate in response to exposure to increasing flupyradifurone rate. Additionally, at 0.127 g a.i. ha-1, the mean generation time was significantly longer than that under control conditions. Following simulated exposure to flupyradifurone for 100 days, population of O. strigicollis in the 0.064 g a.i. ha-1 and control treatments were found to be significantly larger than those exposed to 0.127 g a.i. ha-1. On the basis on LR50 evaluations, whereas the risk of exposure risk was unacceptable for O. strigicollis under in-field scenario, it remained acceptable off-field. Nonetheless, the sublethal effect of prolonged exposure to residual flupyradifurone could pose an unacceptable off-field risk to O. strigicollis (e.g., in adjacent habitats). Consequently, the effects of different flupyradifurone exposure scenarios on O. strigicollis should be thoroughly assessed, and reducing the dosage of flupyradifurone could be advantageous for the control of D. citri when combine with augmentative release of O. strigicollis.

Adsorption of flupyradifurone onto soils: kinetics, isotherms, and influencing factors

The study of the adsorption properties of pesticides in soil is essential to assessing the risk of their pollution of nearby aquatic environments. To reveal the adsorption mechanisms of flupyradifurone (FPO) on soil, batch experiments in five different soils were carried out in this study. The adsorption kinetics and isotherms of FPO in five soils were well fitted by using several models (R² = 0.922-0.998). It was found that both physical and chemical adsorption were included in the adsorption process of FPO in soils; the monolayer adsorption of FPO occurred with a non-uniform energy distribution on the soil surface, and the internal particle diffusion was not the only rate-controlling step. The adsorption coefficients calculated by using the Langmuir (K_L) and Freundlich (K_F) models were 0.0158-0.0982 and 1.053-9.798, respectively. In addition, the main factors affecting the adsorption of FPO in soil were investigated by stepwise regression fitted with the adsorption coefficient (K_d) and the soil properties. It was found that the organic carbon content was the main factor (R² = 0.857, p < 0.05). Therefore, the organic carbon adsorption coefficients (K_oc) were calculated. The results (1.0532-5.6529) indicated that FPO has a low affinity and high mobility in the soils, and may cause water environment pollution around the soil. Therefore, FPO should be used cautiously in paddy fields. These research findings were important for elucidating the sorption behaviour and transport of FPO in soil.

Simultaneous Determination of 108 Pesticide Residues in Three Traditional Chinese Medicines Using a Modified QuEChERS Mixed Sample Preparation Method and HPLC-MS/MS

A rapid, efficient, simple, and high-throughput method for the simultaneous determination of 108 pesticide residues in three traditional Chinese medicines (TCMs) was established, comprising an improved QuEChERS method in combination with HPLC-MS/MS based on mixed samples. A quantity of 10 mL of acetonitrile was used as extraction solvent, and 10 mg of amino-modified multi-walled carbon nanotubes (MWCNTs-NH2) and 150 mg of anhydrous magnesium sulfate (MgSO4) were selected as sorbents for dispersive solid phase extraction. The performance of the method was verified according to the analytical quality control standards of SANTE/11813/2017 guidelines. With good linearity (R2 > 0.9984) in the range of 2−200 μg/L for all pesticides in the selected matrices, and good accuracy, precision, and high sensitivity, the recoveries were in the range of 70−120% for more than 95% of the pesticides, with a relative standard deviation (RSD) of less than 16.82% for all. The limit of detection (LOD) and limit of quantification (LOQ) of the method were 0.01−3.87 μg/kg and 0.07−12.90 μg/kg, respectively, for Fritillaria thunbergii Miq (F. thunbergii), Chrysanthemum Morifolium Ramat (C. morifolium), and Dendrobium officinale Kimura et Migo (D. officinale). The method was successfully applied to 60 batches of actual samples from different regions.