Reverse flow injection analysis of complexing agents and its application to estimation of complexing capacity

A redox reaction of copper(II) with iron(II) proceeds slowly in the presence of neocuproine, although the reaction would not take place in its absence. This reaction is accelerated by the presence of complexing agents such as EDTA, DTPA, CyDTA, EDTA-OH, NTA, citrate, pyrophosphate, producing a copper(I)-neocuproine complex (lambda(max) = 454 nm). A reverse flow injection analysis (r-FIA) method is presented for the determination of trace amounts of complexing agents by measuring the increase in absorbance at 454 nm. Complexing agents at the 10(-6)M level can be determined at a rate of 120 samples/hr. By using this r-FIA system, a new procedure for the measurement of complexing capacity with metal ions such as Al(III), Cu(II), Zn(II), Cd(II) and Pb(II) has been developed. Complexing capacity for each metal ion can be measured at a rate of 120 samples/hr.