Analytical Sciences

Abstract − Analytical Sciences, 19(4), 505 (2003).

Monitoring of Oxidation Steps of Ascorbic Acid Redox Reaction by Kinetics-Sensitive Voltcoulometry in Unsupported and Supported Aqueous Solutions and Real Samples
Jozef ORLICKÝ,* Katarína GMUCOVÁ,**  Ilja THURZO,** and Juraj PAVLÁSEK***
*Institute of Molecular Physiology and Genetics, Slovak Academy of Sciences, Vlarska 5, 833 34, Bratislava, Slovak Republic
**Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 845 11 Bratislava, Slovak Republic
***Institute of Normal and Pathological Physiology, Slovak Academy of Sciences, Vlárska 5, 833 34 Bratislava, Slovak Republic
Aqueous solutions of ascorbic acid in unsupported and supported aqueous solutions and real samples were studied by the kinetics-sensitive double-step voltcoulommetric method with the aim to contribute to a better understanding of its behavior in biological systems. The data obtained from measurements made on analytes prepared in the laboratory, as well as those made on real samples (some commercial orange drinks, flash of the fresh fruits) point to the redox reaction of L-ascorbic acid (L-AH2) being very sensitive to both the presence of dissolved gaseous species (O2, CO2) and the ionic strenght in the analyte. Either the dissolved gaseous species, or the higher ionic strength caused by both the presence of supporting electrolyte and increased total concentration of ascorbic acid, respectively, give birth to the degradation of LAH2. Naturally, the highest percentage of L-AH2 was spotted in fresh fruit.