Rapid kinetic spectrophotometric determination of phosalone (Zolone) in a commercial formulation

A kinetic study of the degradation of phosalone in an alkaline medium was undertaken by using a pneumatic stopped-flow system. A rapid semiautomatic method is proposed for determining phosalone. Linear calibration graphs up to 8.0 x 10(-5) M (detection limit = 1.40 x 10(-6) M) were obtained, with a measurement period of only 3.5 s per sample and a relative standard deviation of 1.4%. Several pesticides were assayed as interference species, and several did not interfere even at a 6:1, M:M foreign species/phosalone ratio. A strong interference (ratio < 1) was generated by azinphos-methyl and carbaryl. The proposed method was applied to the analysis of a commercial formulation, and the results were validated by comparison with those for a chromatographic method.