Simple solid wire microdisc electrodes for the determination of vitamin C in fruit juices

Five micrometre gold microwire encapsulated in a thin sheath of borosilicate glass produced by the Taylor wire process can be used in the fabrication of gold microdisc electrodes. By combining glass-coated wire with fluorinated ethylene propylene lined poly(tetrafluoroethylene) tubing, disposable, high quality electrodes suitable for a range of applications, can be fabricated easily. Chemical etching techniques were investigated as a means of finishing the electrode surface, and the resulting surfaces were studied using scanning electron microscopy and evaluated electrochemically using model redox compounds. The electrodes obtained by this fabrication method were used to determine L-ascorbic acid and the results were compared with values obtained using high-performance liquid chromatography and iodimetry. Measurements were taken in buffered solutions, fruit juices, and directly in fruit. Previous studies have shown that ascorbic acid fouls the electrode surface during voltammetric analysis; these problems were overcome by using potential cycling techniques.