Surface Modified Electrodes Used In Cyclic Voltammetric Profiling Of Quinine An Anti-Malarial Drug

Abstract

In this paper electrochemical profiling of quinine, an effective anti- malarial drug administered to humans, was done using primarily the very versatile electrochemical technique- cyclic voltammetry. In the electro-analysis, the main supporting electrolyte used was sulphuric acid. The surface of the working electrode was modified using electronically conducting polymer- polyanailine and a clay montmorillonite- bentonite. Quinine and metal cation Cu 2+ , Co 2+ , Zn 2+ and Sn 2+ were also used to modify the electrode surface.The results obtained showed that quinine oxidation /reduction potential on bare carbon graphite electrode occured at 0.495V/0.300V and 0.015V (0.25M H2SO4 supporting electrolyte). Bentonite modified electrode gave 0.434V/0.480V (1M H2SO4 supporting electrolyte) and 0.360V/0.345V (1M HCl supporting electrolyte). A mechanistic pathway for the oxidation of quinine has also been proposed. It was also observed from the results obtained from studies on the effect of consumables such as tea, glycine and milk on quinine, that milk totally suppressed the redox process in quinine. Amino acids which are the building blocks in proteins and which is an important macromolecule in humans, does not affect significantly the redox process in quinine. Cyclic voltammetric profiling of quinine interaction with metal cations such as Cu 2+ , Co 2+ , Zn 2+ and Sn 2+ and All solutions were prepared using de-ionized water. The clay montmorillonite, bentonite (sourced from Athi River Mining Company Ltd., Kenya) was purified as described by Bard(18-19). It has a mesh size ranging from 150 to 200 um, cation exchange capacity (CEC) 1.18-1.22 mM/g and a pH range of 8.4-9.6. The density of the bentonite is 1.25g/cm3 which are comparable to other clay minerals from different parts of the world (18). It has a solvent retention capacity of 22.5% and 4.8% for water and organic solvents respectively, while its moisture content is 8.5%. It swells by a factor of 1.7 and 1.4 in water and organic solvents respectively In generating the cyclic potential scans, two sets of instruments were used. These comprised of a Princeton Applied Research (PAR) model 173 pontentiostat/galvanostat, a logarithmic current converter model 369 that controlled the current, a PAR model 175 universal programmer and a PAR RE 0089 X-Y recorder.