Determination of iron(III) and titanium(IV) as their Solochrome Violet RS complexes by constant-current stripping potentiometry: Part 1. Automated single-point calibration method for iron(III)

Abstract

An automated constant-current stripping potentiometric method for the determination of iron(III) as its Solochrome Violet RS complex is described. The instrumentation is based on a stripping potentiometry unit, a sample changer, a burette system and a conventional three-electrode system with a mercury film electrode. The method can be utilised over a large concentration range [0–500 μg 1−1 iron(III)], by an automated adaption of the experimental conditions to the concentrations found in the samples. A single-point calibration procedure with calibration for three different concentration ranges is used. The possibility for normalisation of the electrode response to compensate for variations in hydrodynamic conditions and electrode area is demonstrated. Using this normalisation, the reproducibility is better than 5% for samples at the 15 μg 1−1 iron(III) level. For higher concentrations (65 and 300 μm 1−1), the corresponding values are 2.9 and 3.5%, respectively. The applicability of the method for the determination of titanium(IV) is discussed. The method is applied to the determination of iron(III) in tap water and rain water samples.