A rapid method for the simultaneous determination of paraquat and diquat in pond and river waters by pyrolysis and gas chromatography

Abstract

A rapid method is described for the determination, in aqueous systems, of two widely used herbicides known commercially as paraquat and diquat. Pyrolysis of these herbicides under carefully controlled conditions, followed by gas-chromatographic analysis of the pyrolysate, allows detection of the herbicides down to 0·01 p.p.m. At the lowest concentration levels (0·01–0·1 p.p.m.), there is some loss of linearity of response, possibly as a result of adsorption of the herbicides on the glass surfaces of the vessels used. This effect may have resulted in substantial errors in previously reported low levels of paraquat and diquat and may also occur in the determination of other ionic herbicides.