Spectrophotometric determination of chromium in geological samples

A method for the determination of chromium is presented, based on the oxidation of hydroxylamine hydrochloride to nitrous acid by chromium(VI) in acetic acid medium followed by diazotization of the nitrite produced with p-aminophenylmercaptoacetic acid and subsequent coupling of the diazonium salt with N-(1-naphthyl)ethylenediamine di-hydrochloride in acidic medium to form a stable blueish azo dye. The method is suitable for the determination of chromium(VI) from 0.04 to 1.2 mg l-1 in a 1.0-cm cuvette. The molar absorptivity and Sandell's sensitivity are 3.65x104 l mol-1 cm-1 and 0.0014μg cm-2, respectively. (author). 17 refs.; 3 figs