Analytical Sciences

Simple and Sensitive Electroanalytical Method for the Determination of Ascorbic Acid in Urine Samples Using Measurements in an Aqueous Cationic Micellar Medium

Alaécio Pinheiro dos REIS,* César Ricardo Teixeira TARLEY,** Lucilene Dornelles MELLO,* and Lauro Tatsuo KUBOTA*

* Instituto de Química, UNICAMP, P. O. Box 6154, Campinas, SP, 13083-970, Brazil
** Departamento de Ciências Exatas, Unifal-MG, Alfenas, MG, 37130-000, Brazil

An electroanalytical study for the amperometric determination of ascorbic acid (AA) in a human urine sample at a bare glassy carbon electrode using the CPC (cetylpyridinium chloride) surfactant is described. Under the optimized conditions of E_pa, I_pa, CPC concentration and pH, the oxidation peak potential of the AA shifts towards a less positive potential, and the peak current increase in a significant way in the presence of the surfactant. Under the best conditions, the method provided a linear calibration curve to AA in a 0.1 mol L^-1 phosphate buffer solution (pH 7.0) in the concentration range from 5.0 × 10^-7 up to 4.3 × 10^-4 mol L^-1, with a detection limit of 2.0 × 10^-7 mol L^-1 and a high correlation coefficient (r = 0.9996). The recovery test presented values of 98 - 105%, suggesting a great potential of the proposed method for AA determination in complex samples, such as urine.

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