In this study, a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method was established for the extraction and cleanup of fipronil and its three metabolites (fipronil solfone, sulfide, and desulfinyl) in peanut kernel, shell, straw, seedling, and soil samples, and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used for analysis. The average recoveries were 66-116% at the level of 0.001-0.1 mg/kg with the RSD <19%, and the limit of detection was 0.3 ng/g for all matrices. The dissipation experiment results demonstrated that fipronil dissipated more rapidly in peanut seedling than in soil, with half-lives of <1 day in peanut seedling and 32-57 days in soil depending on the soil pH. The final residues at harvest of peanut kernels were all below 0.02 mg/kg, whereas in peanut shell and straw, the total highest residues were 0.99 and 0.30 mg/kg, respectively. Fipronil-desulfinyl and fipronil-sulfone were the highest residue metabolites in peanut plant (seedling and straw) and soil samples, respectively.

The dissipation and final residues of picoxystrobin in peanut and soil were determined by a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The dissipation and final residue of picoxystrobin at three different provinces (Hebei, Hubei, and Shandong) in China were studied. The fortification experiments at three different spiking levels of 0.01, 0.05, and 0.5 mg kg(-1) in all matrices (soil, peanut seedling, shell, stalk, and kernels) were conducted, and the recoveries were 79-114% with relative standard deviations of 3-12 (n = 5). The dissipation half-lives of picoxystrobin were 1.5-8.6 days in soil, and 2.1-2.8 days in seedlings. The final residues of picoxystrobin in supervised field trials were 0.05-6.82 mg kg(-1) in stalk, ≤0.381 mg kg(-1) in soil, ≤0.069 mg kg(-1) in shells, and ≤0.005 mg kg(-1) in peanut kernels. Considering the final residue levels and the maximum residue limits (MRLs), the pre-harvest interval of 14 days was recommended for the safe use of picoxystrobin in peanut crop.

A simple residue analytical method using the quick, easy, cheap, effective, rugged, and safe (QuEChERS) procedure for the determination of trifloxystrobin and its metabolite trifloxystrobin acid (CGA321113) in tomato and soil was developed using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The limits of detection were 0.0005 mg/kg for trifloxystrobin and 0.001 mg/kg for trifloxystrobin acid, respectively. The average recoveries in tomato and soil ranged from 73-99 % for trifloxystrobin and 75-109 % for trifloxystrobin acid, with relative standard deviations below 15 %. The method was then used to study the dissipation and residues in tomato and soil. The dissipation half-lives of trifloxystrobin in tomato were 2.9 days (Beijing) and 5.4 days (Shandong), while in soil were 1.9 days (Beijing) and 3.0 days (Shandong), respectively. The final results showed that the major residue compound was trifloxystrobin in tomato whereas it was its metabolite, trifloxystrobin acid, in soil. The final residues of total trifloxystrobin (including trifloxystrobin acid) were below the EU maximum residue limit of 0.5 mg kg(-1) in tomato 3 days after the treatment.

Residue analysis of trifloxystrobin and its metabolite (CGA 321113) in rice matrices, paddy water, and soil was developed using the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and high-performance liquid chromatography-tandem mass spectrometry. The method was used to evaluate the dissipation rate of trifloxystrobin and CGA 321113 in rice seedling, soil, and paddy water as well as the residual level in harvest rice (grain, hull, straw) and soil. The results demonstrated that the dissipation half-lives of trifloxystrobin in rice seedling, soil, and water were 1.9 d to 4.7 d, 0.35 d to 0.54 d, and 0.28 d to 0.51 d, respectively. The final total residue of trifloxystrobin and CGA 321113 was highest in rice hull and lowest in paddy soil. The highest total residues in husked rice, rice hull, straw, and paddy soil at 28 d after spraying were 0.39 mg kg(-1), 3.82 mg kg(-1), 0.29 mg kg(-1), and 0.15 mg kg(-1), respectively. According to the final residue data and the maximum residue limits of trifloxystrobin in rice grain and straw (Codex Alimentarius) and in rice hull (US Environmental Protection Agency), 28 d could be recommended as the preharvest interval for trifloxystrobin application in the rice field. The data show that CGA 321113 constitutes a small amount of the final total residues in rice matrices, whereas it is much higher than its parent compound in soil samples.