Extraction and quantitation of paraquat and diquat from blood

Trace amounts of paraquat and diquat in blood were extracted with phenol after deproteinization of blood protein with a chloroform:ethanol mixture and ammonium sulfate. The color reaction of paraquat was achieved by addition of alkaline sodium dithionite to the phenolic extract. The blue paraquat radical produced was determined directly by measurement of the absorption of the phenol layer. The assay of paraquat (> or = 0.5 micrograms) in 1.0 ml of blood (recovery, 93.4%) could be performed within 30 min. Furthermore, simultaneous analysis of paraquat and diquat in the phenolic extract of the sample could be achieved by use of second-derivative spectroscopy within 30 min.