3.2. Voltammetric investigation
The Fig. 2 inset shows current density derived from the cyclic voltammograms
of 300 μmol L−1 vitamin C (pH 7.0) at the surface of electrodes.
The obtained results confirm that the presence of CdO/NPs and
1-methyl-3-butylimidazolium bromide together causes the increase of
the electrode. The direct electrooxidation of vitamin C on the types of
electrodes was investigated by the voltammetry method (Fig. 2). The
CdO/NPmodified ionic liquid carbon paste electrode exhibited great oxidation
current around 414 mV with the peak current of 60.1 μA (curve
a). In contrast, low electrooxidation signal was observed at bare CPE
(curve d) over the same condition. The vitamin C oxidation peak potential
at CdO/NPs/CPE and at bare CPE were observed around 425 and
433 mV with the oxidation current of 27.7 and 12.1 μA, respectively.
Also, at the surface of the ionic liquid carbon paste electrode, the
oxidation peak potential appeared at 420 mV while the oxidation peak
current was 44.2 μA (curve b), which indicated that the presence of 1-
methyl-3-butylimidazolium bromide in CPE could enhance the oxidation
peak currents and decrease overpotential. The results indicated
that the presence of CdO/NPs and 1-methyl-3-butylimidazolium bromide
on the CdO/NP/IL/CPE surface had a large improvement with the
electrooxidation response of vitamin C