An improved approach for extraction and high-performance liquid chromatography analysis of paraquat in human plasma

A simple, sensitive, reliable and economical HPLC method for quantifying paraquat concentration in human plasma has been developed, using diethyl paraquat as an internal standard. The drugs were extracted from the sample and separated on Xtimate C18 column with a mobile phase of 15% acetonitrile in 0.1M orthophosphoric acid containing SDS (150 mg/l). The pH of the mobile phase was adjusted to 3 with triethylamine and the detection wavelength was 256 nm for both paraquat and the internal standard. The average extraction recoveries were 91.9%. Good linearity (R(2)=0.9984) was observed throughout the range of 0.02-10 μg/ml in 0.5 ml plasma. The overall accuracy of this method was 97.6-107.3% and the lower limit of detection was 0.01 μg/ml. The intra- and inter-day variations were lower than 3.65% and 2.64%, respectively. We used this method to examine the paraquat concentrations of 53 patients with acute paraquat intoxication of whom 26 (49.1%) survived. In conclusion, this method was suitable for quantification of paraquat plasma concentration in toxicological samples. It was helpful in both assessing the severity of intoxication and predicting the outcome of paraquat poisoning.