Differential pulse polarographic study of the hydrolysis of endosulfan and endosulfan sulphate in emulsified medium. Application to the determination of binary mixtures of organochlorine pesticides

Hydrolysis reactions of endosulfan and endosulfan sulphate in the emulsified medium formed with ethyl acetate and a mixture of the two surfactants Hyamine 2389 and Triton X-405 are studied by differential pulse polarography. Besides the heptachlor-endosulfan sulphate pair, whose peak potentials are sufficiently different at pH 8.0 to allow their simultaneous determination, the organochlorine pesticide binary mixtures endosulfan-endosulfan sulphate, dieldrin-endosulfan and dieldrin-endosulfan sulphate can be determined based on their hydrolysis reactions in basic medium and on their different reaction rates. The endosulfan-endosulfan sulphate pair can be determined by allowing the mixture to hydrolyse at pH 11.0 and measuring the endosulfandiol peak for the determination of endosulfan. The analysis of the mixture dieldrin-endosulfan is based on endosulfan hydrolysis at pH 12.0 in which dieldrin is not hydrolysed. Dieldrin and endosulfan sulphate can also be determined simultaneously in a 0.5M sodium hydroxide medium. When determining one pesticide in binary mixtures containing a 5.0 x 10(-6)M concentration of the other pesticide, the lower limits of the calibrations obtained were: endosulfan-endosulfan sulphate mixture, 4.0 x 10(-6) and 1.0 x 10(-6)M respectively; heptachlor-endosulfan sulphate mixture, 2.0 x 10(-6)M for endosulfan sulphate; all other cases, 3.0 x 10(-6)M.