Gas chromatographic determination of diquat and paraquat in crops

A sensitive and reproducible gas chromatographic procedure for the determination of diquat and paraquat in potatoes and rapeseed was developed. The volatilization of analytes was carried out via their hydrogenation with sodium borohydride-nickel(II) chloride. After their isolation from the reaction mixture, the derivatives of bipiperidine were separated on a column packed with Apiezon L plus potassium hydroxide. Comparable detection limits (0.005 mg/kg) were achieved with a nitrogen-phosphorus detector and by mass fragmentography, however, the latter method was preferred for analyses of rapeseed extracts owing to its higher selectivity.