Continuous-Flow/Stopped-Flow Determination of Ascorbic Acid Using a Enzymatic Rotating Bioreactor

GERMÁN ALEJANDRO MESSINA; ANGEL TORRIERO; IRMA ESTER DE VITO; JULIO RABA

TALANTA

Elsevier

Año: 2004 vol. 64 p. 1009 - 1017

0039-9140

The high sensitivity that can be attained using an enzymatic system and mediated by hydroquinone, has been verified by on-line interfacing ofa rotating bioreactor and continuous flow/stopped-flow/continuous-flowprocessing. Horseradish peroxidase, HRP, [EC 1.11.1.7], immobilizedon a rotating disk, in presence of hydrogen peroxide catalyses the oxidation of hydroquinone to p-benzoquinone, whose electrochemicalreduction back to hydroquinone is detected on glassy carbon electrode (GCE) surface at −0.15V. Thus, when l-ascorbic acid is added to thesolution, this acid is reduced chemically (p-benzoquinone to hydroquinone) and acts as mediator of HRP, decreasing the peak current obtainedproportionally to the increase of its concentration. The recovery of l-ascorbic acid from four samples ranged from 99.09 to 101.10%. Thismethod could be used to determine l-ascorbic acid concentration in the range 12 nM–3.5
M (r = 0.998). The determination of l-ascorbicacid was possible with a limit of detection of 6 nM in the processing of as many as 25 samples h−1. The method was successfully applied forthe analysis of l-ascorbic acid in pharmaceutical formulations.