Determination of paraquat in tissue using ion-pair chromatography in conjunction with spectrophotometry

Homogenized tissue was deproteinized with sulfuric acid. Paraquat in the supernatant was quantificated directly with the dithionite reagent (step 1) or concentrated by the XAD-2 column chromatographic technique before paraquat determination (step 2). Tissue paraquat levels in the range of 0.01-75 mg/kg could be quantificated by second-derivative or zero-order spectroscopy using 2.5 g of tissues. The sensitivity could be increased tenfold by using 25 g of tissue samples. The coefficients of variation of within-run and day-to-day precisions of spiked paraquat in tissue homogenates were below 5% at concentrations of 10.0, 1.0 and 0.1 mg/kg, respectively. The recoveries of the spiked paraquat in tissues ranging from 0.1-10 mg/kg were 91% by step 1 and 74% by step 2. Using these simple methods, steps 1 and 2, the paraquat concentrations in the psoas muscle, liver, lung and kidneys of a swine dosed with 0.16 g/kg of paraquat were investigated. The results were in close agreement with those of the TCA deproteinization method followed by cation-resin column chromatography. The proposed method offers the advantages of simplicity, rapidity, reasonable sensitivity and a wide range of concentrations.