Oxidation of melatonin on a glassy carbon electrode modified with metallic glucosamines. Synthesis and characterization

In this study, a glassy carbon electrode modified with different cobalt glucosamines (CoGlu-R), iron glucosamines (FeGlu-R), and nickel glucosamines (NiGlu-R) was used for the electroanalytical determination of melatonin in buffer solutions at pH 7.3 using cyclic and square wave voltammetry. The complexes were synthesized and characterized by IR-TF, ¹H-NMR, and UV–visible spectroscopy. When comparing glucosamines of different metals, the influence of the nature of the metal on the activity is not very strong. The most active complex was CoGlu-R. The oxidation peak was used to determine melatonin in the concentration range of 10^?8–10^?5 M with a detection limit of 2.15?×?10^?7 M (LOD). Our results indicate that the current peak is under mass-transport control and probably suggest that chemical reactions coupled with electrochemical steps are involved. The melatonin oxidation current with this kind of modified electrodes is small but this modified electrode shows high selectivity in medium-199 (glutamine, phenol red, glucose, Na⁺, CO₃ ^2?) with human placental tissue; trophoblast and endothelial cells (K⁺, Ca²⁺, traces of Cu²⁺ and Mg²⁺), yet the tryptophan causes interference.