Experimental determinations and computer predictions of trace metal ion concentrations in dilute complex solutions

Abstract

A comparison has been made of experimentally determined and computed metal ion concentrations in the following aqueous solutions of ionic strength <0.015 M containing: (i) up to four trace metals; (ii) ligands selected from glycine or citric, nitrilotriacetic or salicylic acids; (iii) calcium or potassium nitrates as a background electrolyte; and (iv) different pH values. Metal ion concentrations in these solutions were measured using an ion-exchange equilibrium technique and, where appropriate, Cu or Cd electrodes. The metal speciation of the same solutions was also calculated from stability constant data by computer simulation using the programs GEOCHEM and ECCLES. For the well defined solutions studied, the calculated values agreed closely with those determined experimentally, and the two programs gave identical results provided that they used identical stability constant data.