Abstract

The customary diphenylcarbazide (IUC-18) procedure and several modifications thereof have been studied with a view to accommodate coloured extracts and to improve the sensitivity of the procedure for determining the concentration of hexavalent chromium in leather samples. The unmodified IUC-18 procedure is generally inapplicable to leather samples that produce a coloured extract. Even otherwise, the sensitivity of the IUC-18 procedure is limited.

We propose here a pre-bleaching procedure that allows reliable analysis of the majority of the samples studied based on results obtained with Induction Coupled Plasma-Optical Emission Spectrometry (ICP OES) of cation exchanged samples as the reference method. A liquid core waveguide based flow-through absorbance detector deployed in a flow injection format was utilized to significantly improve on the sensitivities normally attainable in the diphenylcarbazide method. Ion exchange of the samples through H+form cation exchangers has also been found to be essential to prevent gross overestimation of the Cr(V1) concentrations, presumably the interference occurs from the presence of other metals in the extract. Concentrations of Cr(VI) in cation exchanged, bleached leather extracts as low as 1 tg/l can be readily measured with inexpensive equipment.