Adsorption Studies and Selective Determination of Epinephrine at Glycerol-Clay Modified Glassy Carbon Electrode

Cyclic voltammetry (CV) was employed to conduct continuous repetitive scans of epinephrine (EP) at glassy carbon electrode coated with a mixture of glycerol and Standard Wyoming montmorillonite clay (SWy-2). The glycerol-clay modified electrode (GCME) was used to monitor the interfacial behavior and adsorption properties of EP and its oxidation product, adrenochrome. The clay film catalyzed EP oxidation and greatly enhanced the generation, accumulation, and adsorption of adrenochrome, without compromising system sensitivity. Progressive adsorptive accumulation was observed during repetitive scanning and maximum adsorptive accumulation (MAA) was achieved only when system pH was 7.4. A linear response was obtained in the range of 0.2 mu M to 75.0 mu M, with detection limit of 0.1 mu M (S/N = 7). The surface coverage of the adsorbed species exhibited linear relationship with the bulk concentration, in accordance with the Langmuir isotherm. The adsorption coefficient obtained from the Langmuir isotherm was 41.3 L/g. The enhanced adrenochrome reduction peak was utilized as a simple and unique approach for selective determination of EP in the presence of serotonin, ascorbic acid, and uric acid.