Electrochemical Behavior of Catecholamines and Related Compounds at In Situ Surfactant Modified Carbon Paste Electrodes

Abstract

The voltammetric characteristics of catecholamines: epinephrine (E) and norepinephrine (NE) and related compounds: isoproterenol, metanephrine, l-dopa, methyldopa, 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.

Application of ionic liquid–TiO2 nanoparticle modified carbon paste electrode for the voltammetric determination of benserazide in biological samples

“…Several methods have been used for the determination of benserazide in pharmaceutical preparations such as capillary electrophoresis [6][7][8][9][10], spectrophotometry [11][12][13][14][15][16], high performance liquid chromatography [17,18], chemiluminescence [19] and voltammetry [20,21]. As yet, no paper has been reported on the voltammetric determination of benserazide using IL-TiO 2 /CPE.…”

Lignosulfonate‐Modified Electrode for Electrocatalytic Reduction of Acidic Nitrite

“…On the basis of literature reports dealing with structurally similar systems, such as monomethylated catecholamine derivatives [4,5], surface-grafted [6] and electropolymerized [7] eugenol, one may predict that the oxidation reaction leads to the development of a reversible redox couple involving quinone/hydroquinone functionalities. This oxidative demetoxylation and formation of reversible redox couple can be easily observed on a cyclic voltammogram recorded in acidic electrolyte containing dissolved lignosulfonate (not shown).…”

Sensitive Electrochemical Sensor for Determination of Methyldopa Based on Polypyrrole/Carbon Nanoparticle Composite Thin Film Made by In Situ Electropolymerization

“…Compared to the bare GCE, the electrochemical response of PPy/CNP/ GCE reduces in the presence of the negatively charged analytes like Fe(CN) 6 4À (Figure 2A), but considerably in- creases when a positively charged analyte such as Ru(PPy) 3 2 + is present ( Figure 2B). This can be related to electrostatic interaction between the negative charge density of the modified film and the analytes, as it has been discussed in the literature for over-oxidized polypyrrole [39].…”

“…Sodium dodecylbenzenesulfonate (SDBS) was purchased from Fluka. Ascorbic acid (AA) and Potassium ferrocyanide (K 4 Fe(CN) 6 ) were purchased from Merck. Ru(bpy) 3 Cl 2 was synthesize in our laboratory based on a reported procedure [37].…”

“…As blood vessels relax, m-dopa relieves high blood pressure [1]. Several techniques have been reported in the literatures for the determination of m-dopa [2][3][4], but electrochemical methods have attracted great interests because of their simplicity, rapidness and high sensitivity in determination of m-dopa and various other analytes, without any tedious pre-treatments [5][6][7].…”