Determination of higenamine and tretoquinol in spices by solid phase extraction-isotope internal standard-high performance liquid chromatography-tandem mass spectrometry

Abstract

A method was developed and validated for the determination of two plant-derived doping agents, higenamine (HG) and tretoquinol (TQ), in 26 kinds of spices. This was undertaken using ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and isotope internal standards. The samples were extracted with ethanol containing 0.5% formic acid and purified using an Oasis MCX solid phase extraction cartridge. Subsequently, a C18 column was used for chromatographic separation using methanol and 0.05% formic acid aqueous solution as the mobile phase. UPLC-MS/MS in positive ESI and multiple reaction monitoring mode with HG-D4 and TQ-D9 as the internal standards were used for detection and quantification of analytes. The method was successfully calibrated in the range of 0.2–50 ng mL−1. The limit of detections (LODs) and limit of quantifications (LOQs) of HG were 0.57–0.88 µg kg−1 and 1.80–2.72 µg kg−1, respectively; the LODs and LOQs of TQ were 0.39–0.58 µg kg−1 and 1.27–1.88 µg kg−1, respectively. The average recoveries of the analytes fortified at four levels ranged from 77.1% to 98.7%, with a relative standard deviation < 15%. The proposed method has been successfully used to monitor real samples, and shown to be sensitive, rapid, and convenient. Hence, this method could be used for regulatory purposes to screen for the presence of HG and TQ in various spices.