Determination of the Herbicides Paraquat and Diquat in Blood and Urine by Gas Chromatography

A gas chromatographic method is described for determining paraquat (I) and diquat (II) in human blood and urine. I or II was readily precipitated as its reineckate complex (III and IV) by addition of Reinecke reagent, although blood required deproteination with 3.4% perchloric acid or 10% trichloroacetic acid. The precipitation is completed in 1 h at room temperature. III and IV were easily reduced by treatment with a mixture of sodium borohydride and nickel(II) chloride to afford corresponding perhydrogenated products, 1,1'-dimethyl-4,4'-bipiperidine (V) from III and trans- and cis-perhydrodipyrido[1,2-a:2',1'-c] pyrazine (VI) from IV. The perhydrogenated products were determined by gas-liquid chromatography (GLC) without interference from the original components of the blood and urine. The GLC method (5% potassium hydroxide solution with 5% Apiezon L on Chromosorb W AW DMCS) is suitable for simultaneous determination with hydrogen flame-ionization detection in the range 1-70 micrograms/ml (0.7-50.7 micrograms/ml as I ion; 0.5-35.6 micrograms/ml as II ion) of I and II in blood and urine. The method could be applicable to the determination of the chemicals in postmortem tissue and as pollutants in soils.