Low Potential Amperometric Determination of Ascorbic Acid at a Single-Wall Carbon Nanotubes-Dihexadecyl Hydrogen Phosphate Composite Film Modified Electrode

A sensitive and selective electrochemical method was developed for the amperometric determination of ascorbic acid (AA) at a glassy carbon electrode (GCE) modified with single-wall carbon nanotubesdihexadecyl hydrogen phosphate (SWNT-DHP) composite film. The SWNT-DHP composite film modified GCE was characterized with SEM. The SWNT-DHP composite film modified GCE exhibited excellent electrocatalytic behaviors toward the oxidation of AA. Compared with the bare GCE, the oxidation current of AA increased greatly and the oxidation peak potential of AA shifted negatively to about -0.018 V (vs. SCE) at the SWNT-DHP composite film modified GCE. The experimental parameters, which influence the oxidation current of AA, were optimized. Under the optimal conditions, the amperometric measurements were performed at a applied potential of -0.015 V and a linear response of AA was obtained in the range from 4 ${\times}$ $10^{-7}$ to 1 ${\times}$ $10^{-4}$ mol $L^{-1}$ and with a limit of detect (LOD) of 1.5 ${\times}$ $10^{-7}$ mol $L^{-1}$. The interferences study showed that the SWNT-DHP composite film modified GCE exhibited good sensitivity and excellent selectivity in the presence of high concentration uric acid and dopamine. The proposed procedure was successfully applied to detect AA in human urine samples with satisfactory results.