Dissipation and residue determination of penicillin G and its two metabolites in citrus under field conditions by DSPE/UPLC‐MS/MS

A rapid determination method of residual penicillin G and its two metabolites in citrus was developed and validated by dispersive solid-phase extraction and ultra-high performance liquid chromatography-tandem mass spectrometry (DSPE/UPLC-MS/MS). The samples were extracted with 80% acetonitrile and purified with octadecylsilane. High linearity was obtained with correlation coefficients (r2 ) > 0.9981. The limit of quantification were 0.005-0.01 mg/kg. The recoveries of penicillin G and its metabolites spiked in blank citrus were within 76.7%-107%, with relative standard deviations of 1.3%-9.6%. The dissipation dynamics and distribution of penicillin G in citrus followed first-order kinetics, with half-life of 1.7-2.7 days. Penicillin G degraded easily in citrus and the metabolite was mainly penilloic acid, which can stably exist for long time. The terminal residues of penicillin G in pulp, whole citrus and peels were 0.015-0.701, 0.047-7.653, and 0.162-13.376 mg/kg respectively. The hazard indexes for risk assessment of citrus were significantly < 1, suggesting the health risks to humans after consumption of citrus were insignificant and negligible. These results could provide necessary data for evaluating the safe and proper use of penicillin G in citrus.