Studies about the adsorption of progesterone (P4) at glassy carbon electrodes in aqueous buffer solution by square wave voltammetry

FERNANDO JAVIER ARÉVALO; PATRICIA GABRIELA MOLINA; MARÍA ALICIA ZÓN; HÉCTRO FERNÁNDEZ

JOURNAL OF ELECTROANALYTICAL CHEMISTRY

ELSEVIER

Año: 2009 vol. 629 p. 133 - 137

0022-0728

ABSTRACTThe adsorption of progesterone (P4) on the glassy carbon (GC) electrode surface bymean of square wave stripping voltammetry measurements is studied. A cathodic peakis obtained at -1.65 V (vs. ECS) in pH 8 buffer solution after accumulation onto GCsurface at open circuit. Peak current variations with the accumulation time, P4concentration and temperature are presented. The adsorption is characterized by anonlinear pseudosigmoid temperature dependence of the Gibbs free energy, whichreveals that the adsorption strength is increased at higher temperatures. During theadsorption of P4, strong lateral interactions are developed between neighboringadsorbates, which are severely weakened as the temperature increases. The Frumkinisotherm is the model which best fit to experimental results. Values of the Gibbs freeenergy, enthalpy and entropy of adsorption are calculated. Also, the apparentheterogeneous rate constant for the electron transfer reaction of adsorbed species isdetermined.