Kinetic separation in flow injection spectrophotometry: Simultaneous determination of copper and zinc in a single run

A flow injection spectrophotometric method for the simultaneous determination of copper (II) and zinc (II) in mixtures was developed, utilizing metal–zincon complex formation and kinetic differences in the ligand substitution reaction of these complexes with aminopolycarboxylic acids at pH 9.18. The linear range for the determination of zinc is 0.2–9.7 μg ml−1 and for copper is 0.2–3.5 μg ml−1. About 90 samples can be determined in 1 h. The proposed method has been applied to the determination of zinc and copper in various vitamin formulations with no need for previous separation.