A new dialysis-ion exchange technique for determining the forms of trace metals in water

Abstract

A new separation technique is described which should aid attempts to determine the physicochemical forms of trace metals in aquatic systems. The technique involves combined dialysis and ion exchange, and permits the dialysis experiment to be completed in times very much shorter than normal. Experiments reported in this paper indicated that an optimum time of 5 h was necessary for complete dialysis of all dialysable species from natural water samples. The method has been tested for Cd, Cu, Pb, Zn and Fe in synthetic solutions prepared from distilled-deionized water. In all cases it was apparent that, within the precision of the technique, almost 100% of the added trace metals was dialysed in the 5-h time period. The results give in- formation on the concentration of ionic species present in the water. Three natural river water samples were also dialysed, and the results compared with total and filterable (< 0.4 �m) trace metal concentrations obtained for the same samples.