A Voltammetric Sensor Based on Modified Multiwall Carbon Nanotubes for Cysteamine Determination in the Presence of Tryptophan Using p‐Aminophenol as a Mediator

Determination of cysteamine and tryptophan is described by electrochemical methods using p‐aminophenol‐multiwall carbon nanotubes paste electrode. Cysteamine and tryptophan in mixture can each be measured independently from each other with a potential difference of 600 mV. The results showed that the electrocatalytic currents increased linearly with cysteamine and tryptophan concentrations over the ranges 0.5–300 µmol L−1 and 10.0–650 µmol L−1, respectively. The detection limits for cysteamine and tryptophan are found to be 0.14 and 5.9 µmol L−1, respectively. The proposed method is successfully employed for the determination of cysteamine in both capsule and urine samples.