Abstract: A method was developed for the determination of chlorpyrifos residues in paddy field aquatic products by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples were extracted with acetonitrile and purified by using 0.2 g primary secondary amine (PSA) sorbent and 1.2 g MgSO₄. The target compound was separated on a Hypersil GOLD C₁₈ column (100 mm×2.1 mm, 5 μm), and was determined using a heated electrospray ionization (HESI) source in the positive ion selective reaction monitoring (SRM) mode. The analyte was quantified with external standard using the matrix-matched standard calibration curve method. The results showed that good linearities were obtained in the range of 0.5-100.0 μg/L, and the correlation coefficients were greater than 0.999. The spiked recoveries of chlorpyrifos ranged from 86.2% to 103.6% with RSDs of 3.5%-7.6% (n=6). The limits of detection and quantification were 0.25 μg/kg and 0.5 μg/kg, respectively. This method is simple, quick, sensitive, and suitable for the rapid determination and analysis of chlorpyrifos residues in paddy field aquatic products.

Key words: chlorpyrifos, paddy field aquatic products, QuEChERS, ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)