Determination of ascorbic acid levels in food samples by using an ionic liquid-carbon nanotube composite electrode.

A novel carbon composite electrode consisted of ionic liquid n-octylpyridinum hexafluorophosphate (OPFP) and single-walled carbon nanotube (SWCNT) was fabricated and investigated. This electrode combined the advantages of ionic liquid and SWCNT together with the "bulk" composite electrode. Compared with other composite electrodes using graphite or paraffin oil, the ionic liquid-SWCNT (IL-SWCNT) composite electrode exhibited remarkable increase in the electron transfer rate for electroactive compound and significant decrease in the overpotential for ascorbic acid oxidation reaction. Based on the greatly enhanced electrocatalytic activity for the oxidation of ascorbic acid, a wide linear detection range from 3.0 μM to 4.2 mM with a low detection limit of 1.0 μM was obtained. Furthermore, the IL-SWCNT electrode was applied to determine ascorbic acid levels in real food samples. Experimental results showed that the proposed electrode could be used as an effective and sensitive sensor for direct detection of ascorbic acid.