Quantification and toxicokinetics of paraquat in mouse plasma and lung tissues by internal standard surface-enhanced Raman spectroscopy.

Paraquat is a quaternary ammonium herbicide with an excellent herbicidal effect but is highly toxic to human and animals. Although prohibited by many countries, paraquat intoxication occurred occasionally and caused severe consequences. Rapid and accurate determination of paraquat concentration in intoxication samples is urgently needed in the clinic to promptly evaluate the prognosis of poisoning patients. Here we report an internal standard surface-enhanced Raman spectroscopy (IS-SERS) quantification method on paraquat in mouse plasma and lung tissues for the first time. One measurement per sample was fulfilled within 10 s via this IS-SERS method. Paraquat had good linearity in the range of 1 ~ 500 μg/L (plasma sample) and 1 ~ 100 μg/g (lung sample), with the LOD and LOQ of 0.5 μg/L and 0.1 μg/g (plasma sample), and 5 μg/L and 1 μg/g (lung sample), respectively. This IS-SERS method was validated according to the international guidelines and applied to a quantitative determination and the toxicokinetics on paraquat in mouse plasma and lung tissues. The results indicated that paraquat had a fast absorption rate and a slow elimination rate in mouse plasma and lung tissues. Paraquat was prone to accumulate in target organs after entering the blood. It also proved its good practical applicability in one clinical intoxication sample. Meanwhile, we unveiled an underestimation of free paraquat amount towards common biological sample pretreatment, a certain amount of paraquat bound to components with molecular weight less than 30 kDa in the plasma; we hope it could provide some interesting information for possible clinic treatment.