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 mu mol L-1 and 10.0-650 mu mol L-1, respectively. The detection limits for cysteamine and tryptophan are found to be 0.14 and 5.9 mu mol L-1, respectively. The proposed method is successfully employed for the determination of cysteamine in both capsule and urine samples.