SIMULTANEOUS KINETIC DETERMINATION OF METAL-ION MIXTURES BASED ON A LIGAND SUBSTITUTION-REACTION

The rates of the ligand substitution reactions between 2-(4-sulfophenylazo)-l,8-dihydroxy-3, 6-naphthalenedisulfonic acid (SPADNS) complexes of Co2+, Ni2+, Pb2+ and Cu2+ and EDTA (or CDTA) have been studied at 25.0°C, pH 8.0-9.3, by stopped-flow spectrophotometry. The reactions are first order in SPADNS complex and in incoming ligand. The absorbance change during the reaction progress can be kinetically separated for each component of a mixture, so that metal ions down to 10-6 M can be determined. Components of very high reactivity, such as Cd2+, Mn2+ or Zn2+, can also be determined as part of a multicomponent mixture. © 1989.