Enrichment of artificial sea water. A critical examination of Chelex-100 for group-wise analyte pre-concentration and matrix separation

Abstract

Within the framework of a stability study in a project to propose stable solutions of trace elements that can be used as reference materials for the analysis of, inter alia, sea water and mineralised biological materials, Chelex-100 was used for sample enrichment prior to establishing possible variations of the concentration of the test elements (Cd, Co, Cu, Mn, Pb and Zn) as a function of the storage time. As ICP-AES was the analytical method of choice, group-wise concentration of trace elements is preferred. The widely varying success with which Chelex-100 has been used for sample enrichment compelled us to undertake a systematic examination of each of the procedures involved in sample enrichment.

It became apparent that the conditions required for the realisation of experimentally controlled trace-element recovery are considerably more critical than is generally assumed. Thus, it appears that pH, column washing conditions and amount of resin are the most critical parameters. Under the derived optimum conditions, quantitative recovery was attained for Cd, Co, Cu, Pb and Zn from artificial sea water that was spiked with these test elements in the concentration range 5–100 µg l^–1. The resulting enrichment factor was sufficient for the aim intended.