Liquid Chromatography-triple Quadrupole Mass Spectrometry Simultaneously Detecting Paraquat and Metabolites in Biological Samples

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Journal Article
Forensic Science and Technology, 2022, 47, (1), pp. 49-57
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Objective To establish an LC-MS/MS method for determination of paraquat (PQ) and its main metabolites [monoquat, paraquat-monopyridone (MP), paraquat-dipyridone (DP) and 4-carboxy-1-methylpyridinium ion (MINA)] in biological samples. Methods The biological samples (blood and tissues for this assay) were added with Paraquat-d8 Dichloride (PQ-D8), the internal standard substance, successively having them adjusted of pH values and precipitated of proteins with acetonitrile so that their supernatants were cleansed with cyclohexane and consecutively centrifuged to receive the lower layer of acetonitrile. The received fluid was undergone with drying, re-dissolved into methanol, centrifuged and filtrated through membrane, thereafter having been brought to elution with different chromatographic columns of LC-MS/MS apparatus. For the analysis of mass spectrometry into the eluate from column separation, LC-MS/MS apparatus was set under multiple reaction monitoring (MRM) mode plus positive ionization. Results Linear ranges were present with PQ, monoquat, MP, DP and MINA at each individual’s 5-800ng/mL, 0.5-80ng/mL, 5-800ng/mL, 2.5-400ng/mL and 2-320ng/mL (all rendering an r higher than 0.993), with their intraand inter-day precision (RSDs) being 5%~14%, 3%~13%, 3%~15%, 5%~13% and 2%~15% plus the accuracy (RE) being 91%~116%, 80%~100%, 80%~111%, 85%~114% and 91%~114%, respectively. Besides, if the processed samples were placed with the autosampler at room temperature for 72 hours, each analyte (in the order of PQ, monoquat, MP, DP and MINA) demonstrated its own accuracy of 90~119%, 56%~125%, 60%~110%, 78%~98%, 83%~117%, respectively. Conclusions This approach set up here is of simple pretreatment, good separation effect and high extraction efficiency, capable of detecting PQ and metabolites from suspected paraquat poisoning samples. As the optimized update from our team’s earlier attempt to detect paraquat, monoquat and MP in biological samples, this approach could also have detected the trace metabolites even if the PQ is greatly reduced of content lower than certain favorable conditions.
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