Abstract
Abstract We developed a new procedure for the indirect determination of the organophosphorus pesticide dimethoxydithiophosphate (DDTP) by coupling, in continuous mode, flow injection analysis (FIA) with liquid-liquid extraction and atomic absorption spectrometry with hydride generation in the organic phase. Both continuous-mode extraction of the species Bi(DDTP)3 in isobutylmethylketone (IBMK) organic medium and the process of hydride(BiH3) generation in the same organic medium were optimized. The most suitable solvent of the reducing agent, NaBH4, was a 1 % solution of N,N-dimethylformamide in glacial acetic acid medium. Phase separation was accomplished with an original design that has been patented for use (Spain patent 10,118,929 Y). The hydride generated is transported by the FIA setup in continuous mode to the quartz cell where the analytical signal was measured. The procedure developed was rapid, continuous, and involved little manipulation, thus avoiding possible errors and contamination. Moreover, only small amounts (250 μL) of sample were required in the injection of the aqueous sample, and a volume of 30 μL was used in the injection of the organic phase extracted. The values obtained for the detection limit (5 ppb DDTP in the aqueous phase injected) and for precision (3.0%, expressed as coefficient of variation) are very acceptable in comparison with other procedures described in the literature. The accuracy obtained was in agreement with the imprecision of the method when it was applied to the aqueous samples. The procedure can be used for the analysis of surface waters subject to different types of treatment prior to their use for human consumption. For this type of water, European legislation permits pesticide concentrations up to 5 ppb, which is the value of the detection limit obtained in the proposed procedure.
Published Version
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