Simultaneous determination of paraquat and diquat in human tissues by high-performance liquid chromatography

A simple, sensitive, reliable, and economical method for simultaneous determination of paraquat dichloride and diquat dibromide in human biological materials has been developed, using high-performance liquid chromatography. The drugs were extracted from the sample with a Sep-Pak C18 cartridge and applied to a chromatograph with the internal standard, L-tyrosine. Paraquat and diquat were clearly separated on the octadecylsilica column with a mobile phase of 0.5% potassium bromide in 5% methanol solution, containing triethylamine (1 ml/l). The pH of the mobile phase was adjusted to 3-4 with 1.3 M phosphoric acid. Two ultraviolet wavelengths were selected, 256 nm for paraquat as well as the internal standard, and 310 nm for diquat. The calibration curves were linear in the concentration range 0.1-10 micrograms/g, and the lower limit of detection was 0.05 microgram/g. We used this method to examine the concentrations of paraquat and diquat in tissues of an individual at autopsy.