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

Phenthoate is a chiral organophosphate pesticide with a pair of enantiomers which differ in toxicity, behavior and insecticidal activity, and its acute toxicity on human health owing to the inhibition of acetylcholinesterase highlights the need for enantioselective detection of enantiomers. Therefore, this study aimed to establish a simple rapid method for separation and detection of phenthoate enantiomers in fruits, vegetables and grains. The enantiomers were separated using reversed-phase high-performance liquid chromatography–tandem mass spectrometry for the first time. Rapid chiral separation (within 9 min) of the target compound was achieved on a chiral OJ-RH column with the mobile phase of methanol–water = 85:15(v/v), at a flow rate of 1 ml/min and a column temperature of 30°C. Acetonitrile and graphitized carbon black were used as the extractant and sorbent for pretreatment, respectively. This method provides excellent linearity (correlation coefficient ≥0.9986), high sensitivity (limit of quantification 5 μg/kg and limit of detection <0.25 μg/kg), satisfactory mean recoveries (76.2–91.0%) and relative standard deviation (intra-day RSDs ranged from 2.0 to 7.9% and inter-day RSDs ranged from 2.4 to 8.4%). In addition, a field trial to explore the stereoselective degradation of phenthoate enantiomers in citrus showed that (−)-phenthoate degraded faster than its antipode, resulting in the relative accumulation of (+)-phenthoate.