SIMULTANEOUS STOPPED-FLOW KINETIC DETERMINATION OF GALLIUM AND INDIUM BY A LIGAND SUBSTITUTION-REACTION

A kinetic method for the analytical determination of binary mixtures of gallium and indium in liquid samples is described. The method is based on the spectrophotometric determination of the variation in absorbance connected with the displacement of a metallochromic ligand from the metal ions to be determined. The different reaction rates of gallium and indium enable the single metals to be distinguished and to be determined down to concentrations of 0.2-mu-g ml-1, in binary mixtures. Determinations in water samples from the River Po have been performed with satisfactory accuracy and precision. Standard deviations were around 4-5%, and mean relative errors were around 5-7%.