Analytical Sciences

Flow Injection/Atomic Absorption Spectrometric Determination of Zineb in Commercial Formulations of Pesticide Based on Slurry Sampling

Ricardo J. CASSELLA,*  Verônica A. SALIM,** Salvador GARRIGUES,*** Ricardo E. SANTELLI,** and Miguel de la GUARDIA***

*CEFETEQ/RJ, Rua Senador Furtado 121-125, Rio de Janeiro/RJ, 20270-021, Brazil
**Departamento de Geoquímica, Universidade Federal Fluminense, Niterói/RJ, 24020-007, Brazil
***Departamento de Química Analítica, Universidad de Valencia, Dr. Moliner 50, Burjassot, Valencia, 46100, Spain

This paper reports on a new strategy for the slurry sampling determination of dithiocarbamate 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 µg ml^-1 zineb provided good linear calibration fits. From the obtained data, a detection limit (3sigma) of 1.0 µg ml^-1 zineb was found and a repeatability of 2.7% was obtained from 12 measurements of a slurry containing 2.5 µg 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.

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