Comparison of chelating agents immobilized on glass with chelex 100 for removal and preconcentration of trace copper(II).

Three types of chelating agents immobilized on glass were compared with Chelex 100 for removing and preconcentrating trace Cu(2+) from laboratory-prepared solutions. Columns of immobilized N-propylethylenediamine (diamine), its bis(dithiocarbamate) (DTC) and immobilized 8-hydroxyquinoline (8-HQ) quantitatively remove Cu(2+) (10-200 mug l. ) from buffered solutions at pH 6.00. Addition of isolated natural organic matter at concentrations typical of organic-rich fresh waters (25-100 mug l. ) complexed Cu(2+) and hindered the performance of Chelex and the immobilized chelating agents. In the presence of organic matter the DTC performed very well, removing about 98% of the Cu(2+). However, the Cu(2+) removed could not be readily recovered from the column. Chelex gave the poorest results, removing only 62 and 75% of Cu(2+) at the two levels tested. The other immobilized reagents gave results that were strongly dependent on their contact time with the solution. Longer columns and slower flow-rates tended to improve results. Overall, the immobilized 8-HQ is probably the most suitable of the materials tested for preconcentration work. A batch titration of 8-HQ with Cu(2+) monitored by ion-selective electrode indicated a conditional stability constant of 6.2 x 10(7), which is larger than the corresponding value for the complex with non-immobilized 8-hydroxyquinoline, measured under the same conditions.