Resumo

SALES, M. Goreti F. et al. Chemically Modified Carbon Paste Electrodes for Ascorbic Acid Determination in Soft Drinks by Flow Injection Amperometric Analysis. Port. Electrochim. Acta [online]. 2008, vol.26, n.1, pp.147-157. ISSN 0872-1904.

Simple, rapid and precise amperometric methods for quantification of ascorbic acid (AA) are presented. Glassy carbon (GC), carbon paste (CP) and modified carbon paste (MCP) electrodes are used for this purpose. MCP electrodes are of CP with 10 % vanadate (V). All electrodes are inserted in a wall-jet device with an Ag/AgCl reference electrode and a platinum auxiliary electrode. This device is coupled to a flow injection analysis (FIA) set-up. Hydrodynamic and amperometric parameters are optimized unvaryingly. GC electrodes present slopes of 4.75 ´ 10⁵ nA L mol^-1 (± 6.4 %) under optimum conditions. CP and MCP electrodes show higher sensitivity, with slopes of 6.37 ´ 10⁵ nA L mol^-1 (± 6.6 %) and 7.32 ´ 10⁵ nA L mol^-1 (± 4.4 %). Linear responses range (1.0-2.0) ´ 10^-6 to (0.8-1.0) ´ 10^-5 mol L^-1. Correlation coefficients were > 0.994 and about 48 samples are analysed per hour. Application of the proposed method to the analysis of soft drinks is presented.

Palavras-chave : ascorbic acid; chemically modified electrodes; flow-injection analysis; amperometry.

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