STUDIES ON SOLVENT-EXTRACTION TO DETERMINE IODIDE INDIRECTLY BY ELECTROTHERMAL ATOMIC-ABSORPTION SPECTROMETRY

Preliminary studies addressed to the determination of iodine, as iodide, by indirect ETAAS and applying solvent extraction are described. The work was carried out to achieve a selective quantification of the iodide contained in the complex formed with mercury(II) in acid medium, but selectivity problems were found. The formation of an ion association complex between mercury(II), iodide and 2,2'-dipyridyl was studied. Several parameters were optimized related to the extraction process: the optimal pH interval, 6.8-7.6; volume of extractant, 2 ml; and shaking time 30 s are proposed. Regarding the performance of the measurements, the optimized graphite furnace temperature programme was also studied, yielding 200 and 1000 degrees C as the best temperatures for the mineralization and atomization steps, respectively. The standard calibration and the standard additions methods were performed. The RSDs of the procedure were between 4.9 and 8.0%, for the standard calibration and from 3.2 to 15.6% for the standard additions method.