Analytical Sciences

Abstract − Analytical Sciences, 20(4), 679 (2004).

Sequential Injection Analysis of Lead Using Time-based Colorimetric Detection and Preconcentration on an Anionic-Exchange Resin
Nestor Zárate ARACAMA,** Alberto N. ARAÚJO,* and Ricardo PEREZ-OLMOS**
*REQUIMTE, Dep Química-Física, Faculdade Farmácia U.P., Rua Aníbal Cunha, 164, 4050 Porto, Portugal
**Lab. Química Analítica, Escuela Universitaria de Ingenieria Técnica Industrial (U.P.V.), Plaza de la Casilla 3, 48012 Bilbao, Spain
The development of a sequential injection analysis manifold for the colorimetric determination of lead in water samples is described. The concentration of lead was assessed from its catalytic effect on the reaction of resazurine reduction caused by sulfide in an alkali medium. To that effect, the reaction zone was stopped at the detector, and the time interval required for the attainment of an absorbance decrease of 0.800 at the wavelength of 610 nm was estimated. Interference of other transition metals of the samples was minimized by adding potassium iodide to the sample and retaining the iodocomplexes formed in an on-line anionic resin (AG1 X8). Elution was made with a 2 mol/L sodium hydroxide solution. The relationship [SIA] µg/L = 0.99 (±0.11) x [ETAAS] µg/L + 0 (±4) was obtained upon comparing the results given by the proposed system and by electrothermal atomization atomic absorption spectrometry (ETAAS) after the analysis of ten water samples.