pH-stat techniques in titrimetric analysis: IV. pH-stat monitoring of chelatometric titrations Original Research Article

The theory of pH-stat chelatometric titrations recently developed [Anal. Chim. Acta 456 (2002) 313] is experimentally substantiated here. The titrations of four representative doubly charged cations having different behaviour (copper, zinc, calcium, magnesium) are taken as examples. Copper is titratable between pH 3 and 5, zinc between 3 and 6, calcium between 6 and 10, and magnesium between 7 and 10. The shapes of the titration plots agree well with the theory, accounting for simultaneous equilibria involving proton exchange. The technique yields accurate and precise results, which compare favourably with those of other instrumental techniques, in particular photometric titrations.