Terminal residue and dietary intake risk assessment of prothioconazole‐desthio and fluoxastrobin in wheat field ecosystem

Abstract

Background Wheat is one of the most important cereal crops worldwide, and fungicide is an essential part of wheat production. Both prothioconazole and fluoxastrobin have excellent control of important seed and soilborne pathogens. The combination of these two fungicides shows the complementary mode of action and has a wide usage around the world. But the residue levels of these fungicides in the wheat matrix are still unknown. Results In the current study, a simple, low‐cost, and highly sensitive method using modified QuECHERS procedure combining with high‐performance liquid chromatography‐tandem mass spectrometry was developed to simultaneously quantify E‐ and Z‐fluoxastrobin, and the main metabolite prothioconazole‐desthio of prothioconazole in the wheat matrix. The recoveries of prothioconazole‐desthio, E‐fluoxastrobin, and its Z‐isomer ranged from 84% to 101%, with the relative standard deviations less than 13.2%. The terminal residues of prothioconazole‐desthio, E‐fluoxastrobin, and its Z‐isomer were studied in wheat grain and straw under field conditions. The results showed that the terminal residue of the target compounds ranged from <0.01 mg/kg to 0.029 mg/kg and <0.05 mg/kg to 7.6 mg/kg in wheat grain and straw (expressed as dry weight), respectively. The risk quotients of prothioconazole‐desthio and fluoxastrobin were 0.2% and 3.2%. Conclusion The residue levels of the target analytes in wheat grain were lower than the maximum residue limits recommended by the Chinese Ministry of Agriculture. And the calculated risk quotient values were far below 100%, indicating a low dietary intake health risk to the consumers.