Rapid and sensitive quantification of paraquat and diquat in human serum by liquid chromatography/time-of-flight mass spectrometry using atmospheric pressure photoionization

摘要

We developed a rapid and sensitive liquid chromatography/time-of-flight mass spectrometry (LC/ TOF-MS) method using atmospheric pressure photoionization (APPI) for the determination of paraquat and diquat in human serum. Serum samples were extracted with aqueous formic acid and acetonitrile. After vortexing and centrifu-gation, the supernatants were filtered with ultrafiltration cartridges followed by APPI-LC/TOF-MS analysis using a hydrophilic interaction chromatography analytical column. The total amount of time required for analyzing serum samples was <20 min. Calibration curves using solvent standards were linear in the range of 0.0005-1.25 ug/ml. The intraday recoveries (n = 6) for paraquat and diquat added to human serum at 0.1 ug/ml were 99.0 and 91.9 %, respectively, with relative standard deviations of 5.8 and 6.5 %. The limits of detection calculated at a signal-to-noise ratio of 3 were 0.005 mug/ml for paraquat and 0.006 ug/ml for diquat. This method was applied in the analysis of four autopsy cases involving suspected paraquat intoxications. The concentration of paraquat and diquat in serum ranged from <0.005 to 72 mug/ml.