Study of sorption of copper on complexing resin columns by solid phase extraction.

The position of the breakthrough pro®le of a substance sorbed on solid phase columns is given by the central point of the breakthrough curve, VC. This is the volume of eluted solution for which the concentration of the substance is half of that present in the original solution. VC depends on the characteristics of the column (volume of the stationary and mobile phase) and on the distribution ratio KD. In the case of the sorption of metal ions on complexing resins, the distribution ratio can be evaluated from the exchange coef®cients of the metal ion on the resin, which in turn depend on the conditions considered. In the present paper the dependence of the exchange coef®cients on the conditions (acidity and composition of the solution, composition of the resin phase) is accounted for by the Gibbs±Donnan model for the ion-exchange resin. In this work it is shown that KD calculated on the basis of the model is suf®ciently accurate to allow the prediction of VC. The sorption of copper(II) on column of complexing resin was studied by determining the breakthrough curves, whose position on the eluted volume axis was evaluated by the central point VC. Two complexing resins were considered, with different sorbing properties towards copper(II), Chelex 100 and Amberlite CG50, containing iminodiacetic and carboxylic groups, respectively. It was found that the values of VC calculated from the model are in acceptable agreement with those obtained experimentally under different conditions. The presence in solution phase of substances able to complex copper(II) was also examined. They have an in¯uence on KD and VC as expected on the basis of the model, considering the values of the side reaction coefficients.