Quantitative analysis of chromium(V) by EPR spectroscopy

A procedure to accurately quantitate chromium(V) in environmental and medicinal chemistry samples was developed using electron paramagnetic resonance spectroscopy (EPRS) as the method of detection. It was found to have an error in the order of +/-10% and a detection limit of 0.010 mM (0.5 mg l(-1)) chromium(V). The method has been used to quantitate the formation of chromium(V) in the interaction of chromium(VI) with fulvic acid and a simple model of this acid, viz, 1.2-dihydroxybenzene. Analysis of solutions obtained from the reaction of 1,2-dihydroxybenzene with chromium(VI) demonstrated that even when the organic substrate was present in a 182-fold excess, the maximum chromium(V) concentration attained represented just 1.44% of the initial chromium(VI). Reactions between chromium(VI) and fulvic acid yielded similar results. It was therefore concluded that at background environmental concentrations of chromium and fulvic acid, the production of chromium(V) is insignificant, however, its possible importance in contaminated systems cannot be disregarded on this basis alone. The method for quantitative analysis reported in this paper should be an invaluable tool for investigations into the significance of chromium(V) in the toxicological mechanism of chromium(VI) and its role as a mutagenic agent.