Enantioselective residue analysis of oxathiapiprolin and its metabolite in tea and other crops by ultra‐high performance liquid chromatography–tandem mass spectrometry

Abstract

Oxathiapiprolin is the first chiral piperidinyl thiazole isoxazoline fungicide developed to control downy mildew and other diseases, and there were no prior reports on its enantiomeric residue. In this study, a modified quick, easy, cheap, effective, rugged, and safe extraction and purification method followed by ultrahigh performance liquid chromatography-tandem mass spectrometry determination was first developed and validated for the residue analysis of oxathiapiprolin enantiomers and its metabolite IN-E8S72 in green tea and other crops. Oxathiapiprolin enantiomers and IN-E8S72 were separated on a chiral Lux Cellulose-3 column with the use of 0.1% formic acid in acetonitrile and 5 mmol/L ammonium acetate in water as mobile phases. IN-E8S72 was eluted first, followed by (−)oxathiapiprolin, and then (+)-oxathiapiprolin. The recoveries ranged from 53.3 to 125.3% with relative standard deviations ranging from 1.4 to 16.0%. The limits of quantification for (−)-oxathiapiprolin and (+)-oxathiapiprolin were 0.005 mg/kg in romaine lettuce, head cabbage, potato, grape, and garlic, 0.01 mg/kg in soybean and pea, and 0.025 mg/kg in green tea and dry pepper. The limits of quantification of IN-E8S72 were twice those of (−)-oxathiapiprolin. Screening results with real market samples indicated that there was no enantiomeric excess in the oxathiapiprolin residue in romaine lettuce.

Enantioselective Detection, Bioactivity, and Degradation of the Novel Chiral Fungicide Oxathiapiprolin

“…The ME is ubiquitous in mass spectrometry, including the matrix enhancement effect and matrix suppression effect, which affects the quantitative analysis of compounds. 6,15 External matrix-matched standards were used for both enantiomers to eliminate the ME that was based on guidelines published by the European Food Safety Authority (EFSA). 25 The ME was calculated according to eq 6:…”

“…The solvent standard curve and matrix-matched calibration curves were fitted at 10–1000 μg/L according to both the peak areas and the concentrations of each enantiomer in triplicate. The ME is ubiquitous in mass spectrometry, including the matrix enhancement effect and matrix suppression effect, which affects the quantitative analysis of compounds. , External matrix-matched standards were used for both enantiomers to eliminate the ME that was based on guidelines published by the European Food Safety Authority (EFSA) . The ME was calculated according to eq : where s matrix is the slope of the calibration curve in the matrix and s solvent is the slope of the calibration curve in the solvent.…”

“…So far, the MRLs of oxathiapiprolin have not been proposed for agricultural products in China. 15 Oxathiapiprolin has a chiral carbon atom with two enantiomers (Figure 1). Currently, the studies of oxathiapiprolin mainly focused on the racemate.…”

“…Moreover, the MRLs were recommended from 0.01 to 0.7 mg/kg in various matrixes from the European Union (EU), with representative MRLs of 0.01 mg/kg for pepper, 0.1 mg/kg for cucumbers, 0.2 mg/kg for tomato, and 0.7 mg/kg for grapes. So far, the MRLs of oxathiapiprolin have not been proposed for agricultural products in China . Oxathiapiprolin has a chiral carbon atom with two enantiomers (Figure ).…”

Enantioselective determination of phenthoate enantiomers in plant‐origin matrices using reversed‐phase high‐performance liquid chromatography–tandem mass spectrometry

“…The stability of each phenthoate enantiomer in the solvent or the matrices was tested for 3 months. The matrix‐dependent LOD for both enantiomers was defined as the concentration that produced a signal‐to‐noise ratio of 3 when analyzing samples spiked with phenthoate enantiomers (Xia et al, 2019; Zhang et al, 2020a). The LOQ is considered as the lowest fortified concentration verified by recovery experiments, which were conducted to evaluate the accuracy and precision of the new method (Zhang et al, 2018; Zhang et al, 2019).…”