Selective voltammetric determination of norepinephrine in the presence of acetaminophen and folic acid at a modified carbon nanotube paste electrode

A carbon paste electrode (CPE) was modified by incorporation of carbon nanotubes and a molybdenum (VI) complex (MC) and studied in pH 7.0 phosphate buffer solution (PBS) by cyclic voltammetry (CV). The apparent charge transfer rate constant, ks, and transfer coefficient, α, for electron transfer between MC and CNT paste electrode were calculated. The modified electrode showed an excellent electrocatalytic effect on the oxidation of norepinephrine (NE). In PBS of pH 7.0, the oxidation current increased linearly with two concentration intervals of NE, one is 0.08–30.0 μM and, the other is 30.0–700.0 μM. The detection limit (3σ) obtained by differential pulse voltammetry (DPV) was 43.0 nM. Then the modified electrode was used to determine NE in an excess of acetaminophen (AC) and folic acid (FA) by DPV. The peak potentials recorded in a PBS of pH 7.0 were 220, 480 and 800 mV vs. Ag/AgCl/KCl (3.0 M) for NE, AC and FA, respectively. Finally, this method was used for the determination of NE in NE ampoule and urine samples.