beta-Sonogel-carbon electrodes: a new alternative for the electrochemical determination of catecholamines.

In this work, a new alternative for the electrochemical determination of catecholamines based on beta-cyclodextrin-Sonogel-Carbon electrodes is reported. The incorporation of beta-CD and graphite in the preparation of the Sonogel-Carbon material leads to a modification of the electrode surface properties which causes a significant increase in the oxidation peak current of biomolecules such as dopamine, L-epinephrine, D,L-norepinephrine and catechol. This phenomenon might be attributed to the formation of an inclusion complex between beta-CD and the catecholamines. The amount of beta-CD necessary to form the Sonogel electrode was studied and optimization of electrochemical parameters, perm selectivity and mechanical stability of the sensor are discussed. Scanning electron microscopy and electrochemical impedance spectroscopy measurements were employed to characterize the electrical parameters and the structural properties of the new electrode surface, respectively. Cyclic voltammetry (CV) and Adsorptive differential pulse voltammetry (AdDPV) measurements were also used to explore the electrochemical behaviour of the electrode versus the quoted catecholamines. The beta-CD-Sonogel-Carbon electrode offers fast and linear responses towards dopamine, norepinephrine, epinephrine and catechol, with good and low detection limits: 0.164, 0.294, 0.699 and 0.059 micromol L(-1), respectively.

A novel electrochemical synthesis of poly-3-methylthiophene-gamma-cyclodextrin film Application for the analysis of chlorpromazine and some neurotransmitters.

Gamma-cyclodextrin is an eight glucose unit conical structure, which possesses a hydrophobic internal cavity exhibiting supramolecular complexing properties and a hydrophilic exterior due to the presence of hydroxyl groups. In this work, we have synthesized for the first time a functionalized stable film of poly-3-methylthiophene combined with gamma-cyclodextrin (P3MT/gamma-CD) in tetrabutylammonium hexafluorophosphate/acetonitrile solution. A potentiostatic mode was employed for the film growth. Cyclic voltammetry and electrochemical impedance spectroscopy were used for the characterization of the new film. The resulting conducting polymer sensor offers interesting analytical performances such as: (a) fast and linear responses towards the neurotransmitters dopamine and l-dopa towards the neuroleptic chlorpromazine with low detection limits of 2 x 10(-7), 10(-6), and 10(-7)M, respectively, and (b) simultaneous detection and well-resolved signals between the compounds of interest and ascorbic acid. To the best of our knowledge, these LOD are among the lowest found in the literature. Optimization of parameters such as interference effect, perm-selectivity, and mechanical stability of the sensor are discussed.

Electrosynthesis and analytical performances of functionalized poly (pyrrole/beta-cyclodextrin) films.

The supramolecular complexing properties of cyclodextrins (CDs) have been investigated inside a conducting polymer environment. In this work, we report the synthesis and characterization of a polypyrrole/beta-cyclodextrin (Ppy/beta-CD) film at a glassy carbon (GC) electrode surface. The polypyrrole/beta-cyclodextrin (Ppy/beta-CD) film was prepared by a simple electropolymerization of a 20:1 mixture of the CD and the pyrrole monomer LiClO(4) supporting electrolyte. The resulting functionalized polymer film features interesting electrochemical properties such as selective, simultaneous and quantitative detection of some organic compounds of interest such as polyhydroxyphenyls and neurotransmitters derived from pyrogallol and catechol. The fabricated electrochemical sensor exhibits a fast and reversible linear response toward catechol within the concentration range of 1.5x10(-7) to 8x10(-6)M and towards pyrogallol within the concentration range of 1x10(-6) to 1x10(-5)M. The detection limit was 4x10(-7) and 1.8x10(-6)M for catechol and pyrogallol, respectively. Studies of neurotransmitters such as epinephrine, metanephrine and l-dopa (l-3,4-dihydroxyphenylalanine), showed better response toward epinephrine and l-dopa than for metanephrine. Calibration curves for these two neurotransmitters were linear over the concentration range of 1x10(-6) to 1x10(-5)M. The detection limit was 4x10(-6) and 1x10(-6), respectively. The complexation capability of the Ppy/beta-CD system is addressed here in terms of structure-electrochemical activity relationship. The mechanical stability of the film is also discussed. Measurements were performed using cyclic voltammetry (CV), scanning electron microscopy (SEM) coupled to energy dispersive analysis of X-ray (EDAX) and electrochemical impedance spectroscopy (EIS).