Fast determination of paraquat in plasma and urine samples by solid-phase microextraction and gas chromatography–mass spectrometry

A simple, sensitive and reliable gas chromatographic–mass spectrometric method (GC–MS) for quantifying paraquat concentration in biological samples has been developed, using ethyl paraquat as an internal standard. The method involved the procedures of sodium borohydride–nickel chloride (NaBH4–NiCl2) reduction and solid-phase microextraction (SPME) of the perhydrogenated products. GC–MS was used to identify and quantify the analytes in selected ion monitoring (SIM) mode. Under the optimal conditions, recoveries in plasma and urine samples were 94.00–99.85% and 95.00–100.34%, respectively. Excellent sample clean-up was observed and good linearities (r = 0.9982 for plasma sample and 0.9987 for urine sample) were obtained in the range of 0.1–50 μg/mL. The limits of detection (S/N = 3) were 0.01 μg/mL in plasma and urine samples. The intra-day precision was less than 8.43%, 4.19% (n = 3), and inter-day precision was less than 10.90%, 10.49% (n = 5) for plasma and urine samples, respectively. This method was successfully applied to the analysis of the biological samples collected from a victim who died as a result of ingestion of paraquat.