Flow injection/atomic absorption spectrometric determination of zineb in commercial formulations of pesticide based on slurry sampling

This paper reports on a new strategy for the slurry sampling determination of dithiocarbarnate pesticide zineb {[ethylenebis(dithiocarbamato)]zinc} employing a FIA system with a flame atomic absorption spectrometry detector. In the flow system, an on-line alkaline hydrolysis of the pesticide is performed, allowing the release of Zn(II) ions to the solution, which are easily detected by a flame AAS technique. Several parameters that could affect the performance of the analytical methodology were studied, such as the concentration of NH3(aq) used in the hydrolysis step. the effect of the presence of Triton X-100 on the sensitivity and precision, and the FIA parameters (carrier flow rate and mixing coil volume). Under optimized conditions. aqueous slurries containing 2.5 to 25 mug ml(-1) zineb provided good linear calibration fits. From the obtained data, a detection limit (3sigma) of 1.0 mug ml(-1) zineb was found and a repeatability of 2.7% was obtained from 12 measurements of a slurry containing 2.5 mug ml(-1) zineb. On the other hand, a precision (reproducibility) of 7.8% was achieved from three determinations of a sample containing 128 mg g(-1) of the pesticide. Also, the developed system provides a sampling frequency of 72 h(-1).