Detection and confirmation of paraquat and diquat by capillary gas chromatography/mass spectrometry and capillary gas chromatography/fourier transform infrared spectrometry.

Abstract

The simultaneous detection and confirmation of paraquat and diquat which are components of Preeglox L, a bipyridylium-type herbicide formulation, by fused silica capillary gas chromatography/mass spectrometry was investigated. After reduction of paraquat and diquat with a mixture of sodium borohydride-nickel (II) chloride, the reduction products were gas chromatographed on a non-polar (DB-1) and two polar (DB-17 and Supelcowax 10) fused silica capillary columns by using a mass spectrometer as a detector or an ion trap detector. Of the above three columns, a DB-17 column was the most suitable for the simultaneous detection and confirmation of paraquat and diquat as their perhydrogenated products. Further enhancement of specificity was achieved by mass chromatography at the molecular ions of the perhydrogenated products (m/z 196 and 194) and their base peak ions (m/z 96 and 83). The retention indices of the perhydrogenated product of paraquat, and the trans- and cis-isomer of perhydrogenated diquat were 1525, 1530 and 1588 for DB-1, 1740, 1800 and 1840 for DB-17, and 1895, 1920 and 2035 for Supelcowax 10, respectively. Paraquat and diquat as their perhydrogenated products could be also identified by GC with a Fourier transform infrared detector on a DB-17 column.