Simultaneous Determination of L-Tyrosine and Caffeine Based on Their Electrocatalytic Oxidation at a 4-tert-butylcalix[6] arene-Modified Carbon Paste Electrode

Abstract

Simultaneous determination of L-tyrosine and caffeine was performed at a carbon paste electrode modified with 4-tert-butylcalix[6]arene and in situ Ni2+ ions. Surface characterization of the electrode was carried out by means of scanning electron microscopy. Electrochemical impedance diagnosis revealed that oxidation of both molecules is kinetically facile on the modified electrode. The electrochemical behavior of both molecules was studied using cyclic voltammetry, and further quantified using differential pulse voltammetry (DPV). The results revealed a high sensitivity for their simultaneous detection. DPV allowed simultaneous detection of L-tyrosine and caffeine in the range of 10(-6) to 10(-3) M, with LODs of 2.19 x 10(-7) and 4.03 x 10(-7) M, respectively. The modified electrode was used for individual determination of L-tyrosine and caffeine in various pharmaceutical formulations and simultaneous monitoring in human body fluids.