Electrochemical determination of ascorbic acid at the surface of a graphite electrode modified with multi-walled carbon nanotubes/tetradecyltrimethylammonium bromide

A multi-walled carbon nanotubes (MWCNTs)tetradecyltrimethylammonium bromide (TTAB) filmcoated graphite electrode (GE) was fabricated, and the electrochemical oxidation of ascorbic acid (AA) was studied in Britton-Robinson (B-R) buffer (pH 7.0) using cyclic, square wave, and differential pulse voltammetry (CV, SWV, and DPV). An electroanalytical study of AA and acetaminophen (ACOP) and of several mixtures of these compounds in different ratios was made. A sensitive linear voltammetric response for AA was obtained for the concentration range of 5 x 10(-7) to 1.7 x 10(-4) mol L-1, with a correlation coefficient of 0.992, and the detection limit for AA was found to be 1.1 x 10(-7) mol L-1 using DPV. The relative standard deviation (RSD) was 2.7%, suggesting that the film electrode has excellent day-to-day reproducibility. The proposed voltammetric approach was also applied to the determination of the AA concentration in commercial tablets.