SPECIFIC ADSORPTION OF POTASSIUM PENICILLIN-G ON MERCURY-ELECTRODE

The specific adsorption of penicillin G (salt K) on the mercury in aqu eous solution has been determined from electrocapillary and capacity m easurements. The adsorption of penicillinium anions can be fitted by a Frumkin isotherm with a value of -3.5 for the interaction parameter. The standard Gibbs energy of adsorption, Delta G(0), is a linear funct ion of the surface charge and the Delta G(0) value at zero charge is - 38.6 kJ mol(-1). The inner layer capacity is analysed into its compone nts and these are related to the distances from the inner and outer He lmholtz planes to the metal surface. The possible orientation of the a ntibiotic on the electrode surface is discussed.