Spectrophotometric determination of chromium by using sulphanilic acid and N, N-dimethylaniline

Abstract

<span style="font-size:9.0pt; mso-bidi-font-weight:bold" lang="EN-GB">A sensitive and selective spectrophotometric method for the determination of trace amounts of chromium(VI) directly and chromium(III) after oxidation to chromium(VI) with bromine water has been developed. Chromium(VI) oxidises hydoxylamine using acetate buffer of <i>p</i>H 4 to nitrite, which then diazotises sulphanilic acid to form diazonium salt. These diazonium salts are then coupled with N, N-dimethylaniline in alkaline medium resulting azo dye methyl orange, which induces orange colour in acidic medium shows an absorption maximum at 507 nm. The method is free from the interferences of several metal ions and obeys Beer’s law in the range of 0.1 to 1.8 µg/mL in acidic medium. Molar absorptivity and Sandell’s sensitivity of the system with sulphanilic acid diazoniumchloride and N,N-dimethylaniline couple(methyl orange) in acidic medium are found to be 1.74 × 10⁴Lmol^-1 cm^-1and 3.84 × 10^-3µg/cm² respectively.The optimum reaction condition evaluation and interference of other ions on the determination have been described. The method is useful for the analysis of chromium in soil and pharmaceutical samples.

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