Some observations on the on-line anion-exchange preconcentration for microwave plasma torch atomic emission spectrometry

Abstract

An on-line anion-exchange pre-separation and preconcentration technique was coupled with microwave plasma torch (MPT) atomic emission spectrometry. Analytes in the sample solution formed anionic chloro-complexes in a hydrochloric acid medium. The anionic complexes in a higher acidity solution were preconcentrated on an anion-exchange resin and then eluted with a lower acidity solution. Aqueous samples were introduced into a low-powered Ar-MPT with a pneumatic nebulizer, and the solvent (water) was removed by a desolvation system. The effect of some experimental parameters on determination of Fe, Zn, Cd and Mo was examined and the operating conditions optimized. The detection limits for Fe, Zn, Cd and Mo were 6.5, 0.23, 2.9 and 7.2 ng ml^–1, respectively. The enhancement factors are in the range 10–25 and the dynamic linear ranges are 4–5 orders of magnitude. The interferences caused by easily ionized elements and other concomitant ions tested were eliminated. Some real samples were analysed and the accuracy and precision (1.4–5.0%) obtained were satisfactory.