Indirect atomic absorption spectrometric determination of dimethoxydithiophosphate with back-extraction

Abstract

Two methods for the indirect determination of dimethoxydithiophosphate (DDTP) are described, based on the extraction of the complexes formed by this species with copper and bismuth; these complexes were subsequently back-extracted into an aqueous medium to determine the metals by atomic absorption spectrometry. The Cu(DDTP)₂ complex was extracted into CHCl₃ and back-extracted into a 0.2 M NH₄⁺-NH₃ buffer (pH 10), and the Bi(DDTP)₃ complex was extracted into CCl₄ and back-extracted into an aqueous 10^–2M solution of ammonium oxalate. The precision, detection limit and final recovery of the method involving the copper complex are 0.8%, 4.4 × 10^–3µmol of DDTP (4.4 × 10^–7M in the final aqueous solution) and 92.7%, respectively, while those of the method involving the bismuth complex are 0.9%, 2.2 × 10^–2µmol of DDTP (2.2 × 10^–6M in the final aqueous solution) and 95.8%, respectively. The potential interference of some cationic species and other pesticides was also investigated. Both methods were applied to the determination of malathion, a DDTP derivative, in an agricultural formulation.