SELENIUM DETERMINATION BY HG-ICPAES - ELIMINATION OF IRON INTERFERENCES BY MEANS OF AN ION-EXCHANGE RESIN IN A CONTINUOUS-FLOW SYSTEM

An accurate procedure for the elimination of iron interferences in the determination of selenium in geological materials by the Hydride Gene ration-Inductively Coupled Plasma Atomic Emission Spectrometry techniq ue (HG-ICPAES) is proposed. A selective removal of iron is achieved by on-line incorporation of a microcolumn filled with strongly acidic ca tion exchange resin (Dowex 50W-X8). The microcolumn manifold used was interfaced with the hydride generation manifold by a flow injection sa mple injection valve. After the removal of the iron, a 500 mu l sample was injected into a carrier stream of water. This was merged with hyd rochloric acid and sodium tetrahydroborate in order to generate the co rresponding selenium hydride. The system was found to have a limit of detection of 0.4 ng ml(-1) and a relative standard deviation of 2% for 20 ng ml(-1) selenium. The application of the method on different Geo chemical Standard Reference Samples demonstrated that results were sta tistically indistinguishable from certified values.