1. Determination of ascorbic acid using a enzymatic rotating bioreactor incorporated into a flow injection system

GERMÁN ALEJANDRO MESSINA; IRMA ESTER DE VITO; ROBERTO A. OLSINA; JULIO RABA

Merlo, San Luis. Argentina.

Congreso; Cuyo Biology Society. XXII Annual Scientific Meeting.; 2004

l-ascorbic acid (AA) is important in processes of oxidation and reduction in humans, participating in several metabolic reactions. AA has been used for the prevention and treatment of the common cold, mental diseases, infertility, cancer, and AIDS. Thus, the determination of AA content is particularly important in the pharmaceutical and food industry, where it is extensively used as an antioxidant. In this work, an enzymatic rotating bioreactor is proposed for determining AA in pharmaceutical formulations. Horseradish peroxidase (HRP), immobilized on a rotating disk, in presence of hydrogen peroxide catalyses the oxidation of hydroquinone to p-benzoquinone whose electrochemical reduction back to hydroquinone is detected on glass carbon electrode surface at -0.15V. Thus, when AA is added to the solution, this acid reduce chemically p-benzoquinone to hydroquinone and act as mediator of HRP, decreasing the peak current obtained proportionally to the increase of its concentration. The recovery of AA ranged from 99.09 to 101.10%. This method could be used to determine AA concentration in the range 12 nM–3.5µM (r = 0.998). The determination of AA was possible with a limit of detection of 6 nM, processing 25 samples h-1. The method was successfully applied for the analysis of AA in pharmaceutical formulations.