SPECTROPHOTOMETRIC DETERMINATION OF CHROMIUM BASED ON ION-PAIR FORMATION

A sensitive spectrophotometric method for the determination of trace a mounts of chromium(VI) is described. Chromium(VI) forms chlorochromate anion in the presence of acid and chloride ion. The formed anion is e xtracted in toluene as ion-pair with a cationic dye - rhodamine 6G. At 535 nm absorption maximum molar absorptivity is 2x10(4) 1 mol(-1) cm( -1). The colour is stable for 4 h and the system obeys the Beer's law in the range 0-8 mu g of chromium(VI). Chromium(III) is determined aft er oxidation to chromium(VI) with potassium permanganate. The method h as been applied for the determination of chromium in standard alloy st eels, pharmaceutical preparations, geological samples and industrial e ffluents.