Derivative spectroscopic determination of paraquat in serum

A reliable and sensitive method is described for the quantitative determination of the herbicide paraquat in serum. It involves the formation of dodecyl sulfate-paraquat ion pairs, adsorption of these ion-pairs on XAD-2 resin, and determination of the sensitive derivative spectrum of reduced paraquat. Analytical recovery of paraquat added to serum was about 86% at concentrations of 0.02-1.0 mg/L. Assay sensitivity is 0.005 mg/L, but this could be increased two- to fivefold by using greater volumes (4-10 mL) of serum/plasma without encountering problems of turbidity. The proposed method also avoids interferences from severe jaundice, which generally occurs in patients with paraquat poisoning.