Continuous-flow/stopped-flow system for determination of ascorbic acid using an enzymatic rotating bioreactor.
The high sensitivity that can be attained using an enzymatic system and mediated by hydroquinone, has been verified by on-line interfacing of a rotating bioreactor and continuous flow/stopped-flow/continuous-flow processing. Horseradish peroxidase, HRP, [EC 1.11.1.7], 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 glassy carbon electrode (GCE) surface at -0.15V. Thus, when l-ascorbic acid is added to the solution, this acid is reduced chemically (p-benzoquinone to hydroquinone) and acts as mediator of HRP, decreasing the peak current obtained proportionally to the increase of its concentration. The recovery of l-ascorbic acid from four samples ranged from 99.09 to 101.10%. This method could be used to determine l-ascorbic acid concentration in the range 12nM-3.5muM (r = 0.998). The determination of l-ascorbic acid was possible with a limit of detection of 6nM in the processing of as many as 25 samplesh(-1). The method was successfully applied for the analysis of l-ascorbic acid in pharmaceutical formulations.
Messina
Germán A
GA
Department of Chemistry. National University of San Luis. Chacabuco y Pedernera. 5700 San Luis, Argentina.
Torriero
Angel A J
AA
Vito
Irma E De
IE
Raba
Julio
J