Use of graph theory for evaluating the selectivity of flow-injection analysis based on displacement reactions: Determination of alkaline-earth metalsin water-ammonia media

A theory was developed for quantitatively evaluating the selectivity in the determination of metals by the flow-injection technique with spectrophotom etric detection. The theory was applied to flow-injection analysis based on the ability of alkaline-earth metals to displace copper(II) ions in the Cu (II)-EDTA-4-(2'-pyridylazo)resorcinol system in water-ammonia solutions. Th e feasibility of the theory was demonstrated. It was shown how the theory c ould be used for the selection of justified conditions in the determination of Ca, Sr, and Ba and for the evaluation of the selectivity of the determi nation. Practical examples of the determination of Ca confirm the usefulnes s of the approach developed.