Gas chromatographic determination of parathion and paraoxon in fish plasma and tissues

A sensitive capillary gas chromatographic (GC) method for the simultaneous determination of the organophosphate insecticide, parathion, and its active metabolite, paraoxon, in biological samples was developed. This method involved a simple liquid-liquid extraction of parathion and paraoxon from water, plasma, or tissues and capillary GC determination using electron- capture detection and splitless injection; malathion was used as the internal standard. A gradient oven temperature program was used; the injection port and detector temperatures were 200 and 300°C, respectively. These techniques allowed quantitative determination of parathion and paraoxon at 9-210-ng/mL concentrations; recoveries ranged from 79.4 to 110.3% for tissues and from 91.9 to 100.0% for plasma and water. The within-day and between-day coefficients of variation were less than 8.0%. The method was used to characterize the pharmacokinetics of parathion and paraoxon and the tissue distribution of paraoxon in rainbow trout.