Effects of capacity on the preconcentration of trace metals and matrix elimination by an iminodiacetate chelating adsorbent

Low capacity adsorbents, based on iminodiacetic acid and a crosslinked agarose, Novarosetrade mark, have been synthesised for the enrichment of metal ions. Test ions Cu(2+) with high, and Cd(2+) with a moderate affinity for the sorbent were selected. The study includes the effect of specific capacity and matrix composition on the rate of uptake and recovery of these ions. Using a column packed with 0.25 ml of a sorbent and a sample volume of 100 ml, Cu(2+) is quantitatively accumulated from all of the matrices studied even at a capacity of 6 mumol ml(-1) of adsorbent and a flow rate as high as 100 ml min(-1). The enrichment of Cd(2+) is affected by the matrix and for quantitative recovery the flow rate and capacity must be properly adjusted. In the presence of 0.01 M Ca(2+), a specific capacity of 45 mumol ml(-1) is needed for quantitative retainment and a flow rate of 100 ml min(-1), whereas a capacity of 10 mumol ml(-1) suffices at 10 ml min(-1). The advantage of low specific capacity on the removal of matrix elements has been demonstrated. A method based on the determination of conditional stability constants of the metal sorbent complex is suggested for predicting the sorbent capacity needed to acquire quantitative recovery and optimal matrix elimination.