Spectrophotometric study of the chromium(III)/azide system in the ultraviolet region and its analytical application

Abstract

A sensitive and alternative method for the spectrophotometric determination ofchromium(III) based on the formation of chromium(III)/azide complexes was established byinvestigating a new band in the ultraviolet region. The best experimental conditions for the analyticaldetermination of this metallic ion were: ligand and perchloric acid analytical concentration = 493 and12.0 mmol L -1 , respectively; aqueous medium; T = 25.0 oC; contact time = 1 hour. The maximummolar absorptivity coefficient occurred at 287 nm (average 1.481 ± 0.008 × 10 4 L mol -1 cm -1 ), leadingto the determination of metal ion concentrations one hundred times lower than the ones formerlydetermined in the visible region. The system obeys Beer’s Law and is suitable for chromiumdetermination in the 0.702-2.81 mg L -1 concentration range (15-65% T, 1.00 cm-width quartz cells).Analytical applications of the current method were tested with a nutritional supplement containingchromium. Results were compared with those obtained with atomic absorption spectrometry.