Electrochemical behavior of modified electrodes with carbon nanotubes and nanofibers: Application to the sensitive measurement of uric acid in the presence of ascorbic acid

•Properties of carbon nanotubes and nanofibers modified electrode were compared.•Anionic polyacrylamide was used to the dispersion of carbon nanomaterials.•Determination of UA in the presence of excessive level of AA was performed.•The further application was demonstrated by determining UA in human serum and urine.

In this work, the electrochemical behavior of carbon nanofibers (CNFs) and carbon nanotubes (CNTs) modified electrodes and their electrocatalytic activity toward the oxidation of uric acid (UA) and ascorbic acid (AA) was compared. Both the CNFs and CNTs were suspended in anionic polyacrylamide (PAM) solution to obtain a homogeneous and stable dispersion. The CNTs-PAM modified electrode presents broader peak-to-peak separation and bigger oxidative current to both UA and AA, when compared with the CNFs-PAM modified and bare electrode. The difference was mainly contributed to the bigger electrode surface area provided by CNTs than CNFs. Therefore, the CNTs-PAM modified electrode was applied to the differential pulse voltammetric determination of UA in the presence of excessive level of AA. The peak currents were linearly related to the concentration of UA in the range of 4.0 μM–0.4 mM. The detection limit was estimated to be 1.0 μM. The practical application of the prepared modified electrode was demonstrated by determining the concentration of UA in the real biological fluids.