Electrocatalytic oxidation of uric acid on a carbon ionic liquid paste electrode

Xiamen Entry-Exit Inspection and Quarantine Bureau of the Peoples Republic of China,

Xiamen 361012, P. R. China

College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology,

Qingdao 266042, P. R. China

E-mail : swyy26@hotmail.com Fax : 86-532-84022681

Manuscript received online 28 August 2012, revised 04 June 2014, accepted 04 June 2014

An ionic liquid (IL) modified carbon paste electrode (CILE) was fabricated by using N-butylpyridinium hexafluorophosphate (BPPF6 ) as binder to substitute the traditional paraffin and the voltammetric behaviors of uric acid (UA) on CILE were studied in pH 7.0 phosphate buffer solution. Due to the presence of the IL on the surface of the modified electrode, CILE showed strong electrocatalytic activity to the oxidation of UA. On cyclic voltammogram a pair of redox peak appeared with the anodic peak potential (E_pa) as 345 mV and the cathodic peak potential (E_pc) as 270 mV (vs SCE). Compared with that on traditional carbon paste electrode (CPE), the overpotential of anodic peak was decreased for 155 mV. UA showed a quasi-reversible adsorption-controlled electrochemical process on CILE and the electrochemical parameters such as the charge transfer coefficient (α), the number of electrons transfer (n), the standard heterogeneous rate constant (k_s ) etc. were calculated according to the relationship of scan rate with the peak potential. Under the selected conditions the anodic peak current was proportional to the UA concentration in the range from 2.0 × 10^–6 to 6.0 × 10^–4 mol/L by cyclic voltammetry with the detection limit estimated as 1.0 × 10^–6 mol/L (3σ). The proposed method was further applied to the detection of UA content in human urine samples with satisfactory results.