Simultaneous Determination of Carbaryl, Chlorpyrifos, and Its Metabolite 3,5,6-Trichloro-2-pyridinol (TCP) by Derivative Spectrophotometry. Direct Determination of the Degradation Grade of a Pesticide Formulation by Measurement of TCP

Abstract

The degradation grade (DG) of a commercial pesticide formulation composed of carbaryl and chlorpyrifos has been directly determined by taking the first-derivative signal at 339 nm originated by 3,5,6-trichloro-2-pyridinol (TCP), which is the major breakdown product of chlorpyrifos. Detection and determination limits of 1.3×10 -6 and 4.4×10 -6 M, respectively, have been determined by using a commercial undegraded formulation (previously 1:50 diluted). Simultaneous determination of carbaryl, chlorpyrifos, and TCP can be performed in commercial formulations up to DG values of 25%