Voltammetric studies of the Co(II)-tris(hydroxymethyl)aminomethane and sodium perborate volumetric catalytic system

Abstract

It has been shown that in the tris(hydroxymethyl)aminomethane (THAM)/HCl buffer, Co(II) ions catalyze the oxidation of THAM by sodium perborate. The reaction occurs at boiling temperature, and the product of the catalytic THAM oxidation, tris(hydroxymethyl)nitrosomethane, gives a well-defined quasireversible cathodic wave preceding that of the Co(II) ions by about 160 mV. The voltammetric responses of this product are proportional to the amount of sodium perborate and to the concentration of Co(II) ions. In the volumetric catalytic system of Co(II) ions/THAM/sodium perborate, the sensitivity of the determination of Co(II) is increased by one to two orders of magnitude, depending on the voltammetric technique used. Prior to the detection of tris(hydroxymethyl)nitrosomethane, EDTA was added to the solution to form voltammetrically inactive complexes with Co(II) and other interfering ions. Therefore, this method may be applied for the determination of Co(II) ions at low concentrations in the presence of a large excess of interfering ions, in particular Ni(II) and Zn(II).