Surface Modified Electrodes Used as Nano-electroanalytical Tool-in the Electrochemical-profiling of Hydrocortisone (Medicated Cream), Top Lemon and Extra Clair (Beauty Creams)

Abstract

In this thesis, surface modified electrodes were used to study hydrocortisone cream (medicated cream), Top lemon and Extra Clair (beauty creams). The results presented show that in the 1.0 M sulphuric acid supporting electrolyte the oxidation/reduction peak potentials versus saturated calomel electrode (SCE) for the Top Lemon occurred at 0.61V/0.21V. The Extra Clair had a broad oxidation peak and a reduction peak at 0.44V while Hydrocortisone had a reduction peak at approximately 0.61 V. The cyclic voltammetric responses obtained for Top lemon and Extra Clair beauty creams confirm the presence of quinonic peaks. The results from charge calculations obtained from the cyclic voltammograms gave the electro-gravimetric value of the Quinone as 6.1 x 10-9 g/cm2; this gives the percentage Quinone in the Top-lemon cream as 0.0001%. This fall within the acceptable hydroquinone limits in beauty creams. The total mass of cream in the Top-lemon in the tube was 15g net weight. The electro-gravimetric amount of hydroquinone in the tube is 3.75 x10-5g. This result significant in that it shows that surface modified electrodes can be used in determination of quantities of hydroquinone in beauty creams. Top lemon is also shown to inhibit the polyaniline electro-degradation process. The carbon graphite working electrode was further modified with electronically conducting polymer –polyaniline. This polymer can be switched from insulating to conducting state by varying the potential. The redox properties of Hydrocortisone, Top-lemon and Extra Clair were significantly altered. The results also indicate that modification of the carbon-graphite working electrode with bentonite, a clay montmorillonite with a structured lattice having octahedral and tetrahedral sites affect significantly the redox processes associated with Hydrocortisone, Top lemon and Extra Clair. The Extra Clair oxidation/reduction peaks are well defined and occur at 0.84V/0.48V. The Top lemon had oxidation/reduction peaks at 0.58V/0.28V. The Hydrocortisone had broad misshapened peaks. The effect of the bentonite host matrix is attributed to pre-concentration, structural and entropic effects which represent the ‘Nano’ -electrochemical behavior of these host-matrices. It has also been shown that the nature of cations and anions affect the redox properties of the creams referred to above. This has been attributed to protonation-deprotonation equilibria in the case of polyaniline host matrix. In bentonite the cationic effect is attributed to isomorphous substitution of the cations into the octahedral-layer of the bentonite host matrix. The anionic effect is associated with ionic radii and charge density p-Aminophenol has also been shown to affect the redox properties of the Hydrocortisone, Top-lemon and Extra Clair. FTIR spectrophotometric analysis confirms the presence of hydroxyl, ketonic, aliphatics and aromatic functional groups in Hydrocortisone, Top lemon and Extra Clair.