Flow injection determinations of polyphosphates based on colored metal complexes of xylenol orange and methylthymol blue

Abstract

Substitution reactions between samples and colored metal complexes, such as magnesium-methylthymol blue and cerium(III)-xylenol orange, are applied to flow injection determinations of orthophosphate, diphosphate, triphosphate and EDTA. Various types of manifold with a stopped-flow device are used; the importance of addition of reagents in a logical sequence is stressed. Kinetic and thermodynamic factors associated with the substitution reactions were found to be significantly reflected in the f.i.a. profiles and stopped-flow signals. The working ranges of the methods are 10 -5–10 -4 M.