Selective determination of paraquat and diquat in blood by high-performance liquid chromatography and high-performance liquid chromatography/mass spectrometry

Selective determination of paraquat (PQ) and diquat (DQ) in human whole blood was carried out by high-performance liquid chromatography (HPLC) combined with UV and with fast atom bombardment (FAB) mass spectrometry (MS). The blood sample was deproteinized with 10 % trichloroacetic acid. The drugs present in the supernatant were extracted using a Sep-Pak C₁₈ cartridge and applied to a chromatograph. Isonicotinic acid was used as external standard. PQ and DQ were clearly separated by HPLC on an octadecyl-silica column with a mobile phase of distilled water containing 0.05 % trifluoroacetic acid, 0.05 % perfluoro-n-butyric acid and 0.1 % triethylamine. The calibration curves were linear in the range from 0.1 to 10 μg/ml. The lower limits of detection were 0.05 μg/ml for both PQ and DQ, and recoveries of the compounds were about 80 %. When the precision of the method was evaluated, the coefficients of variation were found to be within 10 %. Confirmation of PQ and DQ in blood was carried out by HPLC with FAB-MS using a mobile phase of distilled water containing 0.1 % trifluoroacetic acid, 0.1 % perfluorc-n-butyric acid and 1 % thioglycerol. This method proved most useful in accurately identifying PQ and DQ in blood from two men who committed suicide by ingesting the herbicides.