Chelation preconcentration with resin analysis by direct sample insertion inductively coupled plasma spectrometry

Batch preconcentration with Chelex-100 followed by direct analysis of the analyte-laden resin by direct sample insertion inductively coupled plasma atomic emission spectrometry (DSI-ICP-AES) is described. The performance of the technique is element specific. Quantitative retention of Cu, Zn, Cd and Pb on the resin is achieved, but only for Cu and Zn does the ratio of the signal before and after preconcentration approach the theoretical preconcentration factor. This observation is mainly caused by the adverse effect of the remnants of the resin after ashing on the excitation properties of the plasma. This is clearly shown by monitoring the ratio of the intensity of a Pb ionic line to a Pb atomic emission line. If the ashing temperature is increased, Cd and Pb are prematurely vaporized in the ashing stage, which is performed with inductive heating in the graphite DSI probe. Increasing the radiofrequency power sustaining the ICP improves the performance of the technique.