A simple and rapid method for the determination of paraquat in serum

A simple and rapid method for the determination of paraquat in the serum was developed by a modification of the method originally reported by Knepil. Serum samples were treated with a mixture of chloroform-ethanol and ammonium sulfate and centrifuged to obtain a clear aqueous paraquat solution. Alkaline dithionite solution was added to the supernatant and the absorbance at 396 nm was recorded as A. A small amount of acetic acid was added to the same cuvette to distinguish the coloured paraquat radical and the absorbance at 396 nm resulted from the serum constituents was again measured as B. From the difference between A and B, the concentration of paraquat was determined in the range of 0.1-4 μg/ml serum, with the recovery of about 90%. This method posesses the advantages of 1) no need of special instrument and 2) short time for the determination. By using this method, paraquat concentration in the serum was monitored succesively during 7 d in a poisoning case.