Semi-automatic catalytic titration of aminopolycarboxylic acids and metal ions with the 4,4′-dihydroxybenzophenone thiosemicarbazone - hydrogen peroxide - copper(II) system

Abstract

A semi-automatic spectrophotometric method is described for the catalytic titration of EDTA and ethylene glycol bis(β-aminoethyl ether)-NN′-tetraacetic acid (EGTA), based on their inhibitory effect on the copper(II)-catalysed oxidation of 4,4′-dihydroxybenzophenone thiosemicarbazone by hydrogen peroxide. Amounts of EDTA and EGTA in the 370–1100 and 380–1 140 µg ranges, respectively, can be determined with a relative standard deviation of about 0.5%(n= 11). Methods are also described for the indirect catalytic titrations of copper(II), nickel(II) and manganese(II), in the range 10–120 µg, with a relative standard deviation of about 0.6%(n= 11).