Analytical Sciences

Abstract − Analytical Sciences, 18(11), 1253 (2002).

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.