DESARROLLO Y VALIDACIóN DE UN MéTODO VOLTAMPEROMéTRICO PARA DETERMINAR ESTA O TOTAL EN AGUA

A sensitive analytical method to determine traces of tin in distilled water, deionized water, tap water, river water and sea water by adsorptive differential pulse cathodic stripping voltammetry, oxalic acid as a ligand and methylene blue as a catalytic reagent was developed, under optimal conditions: initial potential -300 mV, final potential -700 mV, preconcentration potential -350 mV, electrodeposition time 30 s, scan rate 20 mV/s, pulse amplitude 40 mV and pulse width 20 ms. Different peaks signals were studied by cyclic, differential pulse and square wave voltammetry, for oxidation and reduction processes and systems: Sn2+ / Sn0, Sn0 / Sn2+ and Sn2+ / Sn4+. The proposed methodology has a limit of detection 0.03 g/L and a limit of quantification 0.11 g/L, with an average sensitivity 24 nA/( g/L) in a dynamic range between 0.1 and 20 g/L. Recovery rates of spiked water samples of 109, 109 and 113 % were obtained for 0.50, 2.00 and 10.02 g/L of tin in water, and variation coefficient of 7.5, 4.8 and 6.9 %, respectively. Total tin concentration found among different water samples vary between 0.5 and 5.4 g/L.