Analytical Sciences

Chromium(III) Determination with 1,5-Diphenylcarbazide Based on the Oxidative Effect of Chlorine Radicals Generated from CCl₄ Sonolysis in Aqueous Solution

Sivanildo da Silva BORGES,* Mauro KORN,**  and José Luis Fontes da COSTA LIMA^***

*Instituto de Qu<ímica, Universidade Federal da Bahia, Campus de Ondina, 40.170-290 Salvador, Bahia, Brazil
**Departamento de Ci<ências Exatas e da Terra, Universidade do Estado da Bahia, Estrada das Barreiras, s/n 41194-000 Salvador, Bahia, Brazil
***CEQUP/Departamento de Qu<ímica-F<ísica, Faculdade de Farmacia, R. Anibal Cunha 164 4050-047 Porto, Portugal

Oxidation of Cr(III) during sonication in carbonated aqueous solutions saturated with CCl₄ leads to the quantitative formation of Cr(VI) and provides a simple and rapid method for spectrophotometric chromium determination with 1,5-diphenylcarbazide. The key to this method is the production of chlorine radicals when aqueous solution saturated with CCl₄ is exposed to ultrasonic waves of 40 kHz. The effects of sonication period, CCl₄ solution volume, acidity, and interferences were discussed. The time required for a single determination is lower than 2 min. The relative standard deviation obtained for aqueous solutions with 1 ug of Cr was <2% (N = 10) and the calculated detection limit (3sigma) was 5 ng of Cr.

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