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

Abstract

Low capacity adsorbents, based on iminodiacetic acid and a crosslinked agarose, Novarose™, 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 μmol 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 μmol ml −1 is needed for quantitative retainment and a flow rate of 100 ml min −1, whereas a capacity of 10 μmol 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.