Simultaneous Determination of Ascorbic Acid, Acetaminophen, and Tryptophan by Square Wave Voltammetry Using N‐(3,4‐Dihydroxyphenethyl)‐3,5‐Dinitrobenzamide‐Modified Carbon Nanotubes Paste Electrode

N‐(3,4‐Dihydroxyphenethyl)‐3,5‐dinitrobenzamide modified‐multiwall carbon nanotubes paste electrode was fabricated and used as an electrocatalyst for the oxidation of ascorbic acid (AA), acetaminophen (AC), and tryptophan (TP) at pH 7.0. In a mixture containing AA, AC, and TP, the separation potentials were large enough to determine those compounds individually and simultaneously. The peak currents obtained were found to be linearly dependent on AA, AC, and TP concentrations in the ranges of 0.03–70, 0.6–452, and 0.7–270 µmol L−1, respectively. The sensor was used for the determination of AC, AC, and TP in different real samples with satisfactory results.