An analytical method by GC/MS has been established for the herbicide difenzoquat in cereals. Difenzoquat is extracted with acetone, concentrated with a rotary evaporator, and applied to an Extrelut 20 column. The column is washed with n-hexane, eluted with ethyl acetate containing 4 formic acid, and concentrated. The residue is dissolved in 0.1 mol/litre NaOH solution, adsorbed on an ODS mini-column, washed with 50 methanol, and eluted with ethyl acetate containing 4 formic acid. The elute is concentrated and analysed by GC/MS. This method gives a recovery of over 80, with a CV below 6 and a detection limit of 1μg/kg.
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