Electrochemical behavior of catecholamines and related compounds at in situ surfactant modified carbon paste electrodes

The voltammetric characteristics of catecholamines: epinephrine (E) and norepinephrine (NE) and related compounds: isoproterenol, metanephrine, L-dopa, metbyldopa, vanillylmandelic acid (VMA), and homovanillic acid (HVA) at unmodified and in situ surfactant-modified carbon paste electrodes were comparatively evaluated. For the basic and amphoteric compounds the modification of the electrode surface with submicellar concentrations of anionic surfactants (sodium dodecylsulfate, sodium decylsulfate or sodium dodecylsulfonate) produce an important current enhancement in its oxidation and reduction peak current together with the improvement in the reversibility of the processes. These effects were explained in basis on electrostatic and hydrophobic interactions. On the other hand, the oxidation of acidic metabolites, HVA and VMA, was studied at electrodes modified in situ with cationic surfactants. Under certain conditions the surfactant could stabilise some of the electrochemical reaction intermediates, thus explaining the different voltammetric behaviour of HVA and VMA.