An Ionic Liquid Bulk-Modified Carbon Paste Electrode and Its Electrocatalytic Activity toward p-Aminophenol

An ionic liquid bulk-modified carbon paste electrode (M-CPE) has been fabricated by using 1-heptyl-3-methylimidazolium bromide as a modifier. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to evaluate the electrocatalytic activity of the proposed electrode by choosing p-aminophenol (p-AP) as a model compound. Both at a bare carbon paste electrode (CPE) and the M-CPE, p-AP yielded a pair of redox peaks in 0.1 mol·L⁻¹ phosphate buffer solution (PBS, pH 7.0). At the CPE, the peak-to-peak potential separation (ΔE_p) was 0.233 V, while at the M-CPE the ΔE_p was decreased to 0.105 V. Furthermore, the current response to p-AP at the M-CPE was 10.2 times of that at the CPE by DPV. The electron transfer rate constant (k_s) of p-AP at the M-CPE was 13.3 times of that at the CPE. Under the optimal condition, a linear dependence of the catalytic current versus p-AP concentration was obtained in the range of 2.0×10⁻⁶ to 3.0×10⁻⁴ mol·L⁻¹ with a detection limit of 6.0×10⁻⁷ mol·L⁻¹ by DPV. In addition, compared to other modified method the proposed electrode exhibited distinct advantages of simple prapartion, surface renewal, good reproducibility and good stability. It has been used to determine p-AP in simulated wastewater samples.