Affiliation:
1. Innovation Centre of the Faculty of Chemistry Ltd Studentski trg 12 11000 Belgrade Serbia
2. Department of Analytical Chemistry University of Belgrade – Faculty of Pharmacy Vojvode Stepe 450 11000 Belgrade Serbia
3. Miphem laboratory Matice Srpske 57e 11000 Belgrade Serbia
4. University of Belgrade – Faculty of Mining and Geology Đušina 7 11000 Belgrade Serbia
5. Department of Analytical Chemistry University of Belgrade – Faculty of Chemistry Studentski trg 12 11000 Belgrade Serbia
Abstract
AbstractIn this paper, a simple, sensitive, and precise flow injection system was optimized and applied to ascorbic acid determination with a carbon paste electrode modified with the Schiff base copper complex. The modified sensor showed increased sensitivity toward ascorbic acid oxidation with a decrease of oxidation potential by 200 mV. Under optimized flow parameters, working potential, gasket thickness, sample and reaction coil volumes, and flow rate, the developed flow system gave a linear response from 5 to 75 μmol/L of ascorbic acid. The calculated limit of detection was 4.5 μmol/L, calculated as 3σ/s which corresponds to the absolute value of 40 ng for the 50 μL sample coil. The precision for six consecutive injections of 5 and 75 μmol/L ascorbic acid solutions was determined as a relative standard deviation of 5.8 % and 1.5 %, respectively. The flow injection system enabled up to 120 analyses per hour. An optimized flow system was applied to the determination of ascorbic acid in dietary supplements, after simple preparation.