Effects Of Ph On Electrocatalytic Activity Of Carbon Nanotubes In Poly(Acrylic Acid) Composites Used For Electrochemical Selective Detection Of Uric Acid And Dopamine In The Presence Of Ascorbic Acid

Effects of pH on dispersion of carbon nanotubes (CNT) in poly(acrylic acid) (PAA) composites and on electrocatalytic activity of CNT toward oxidation reactions of uric acid (UA) at the composite-modified glassy carbon electrode (GCE) were investigated. Cyclic voltammetry data found that CNT in PAA could electrocatalyze the oxidation reactions of UA as indicated by a significant increase in the anodic peak current (I-pa). Better dispersion of CNT in the PAA cast film exhibited a higher I-pa and electrocatalytic activity. The I-pa was increased with increasing CNT content, with the highest increasing rate from pH 7 at which the electrode was modified by the composite. For a given pH, CNT had higher electrocatalytic activity than fCNT (the functionalized CNT). In the presence of an excess of ascorbic acid, UA and dopamine (DA) could be simultaneously detected by the PAA/CNT 10/2.5 of pH 7-modified GCE. The sensitivity for simultaneous detection of DA was higher than that for UA. The linear range for the DA detection was 0.04-6 mu M and for the UA detection was 0.04-3 mu M.