Adsorption of N-tosylglycine at the Hg/aqueous solution interface at various pH values

The adsorption of N-tosylglycine (CH3-Ø-SO2-NH-CH2COOH) has been studied at the mercury/aqueous solution interface (0.1 M NaClO4 as base electrolyte) with the aim of comparing the interfacial properties of the molecular forms of the amino acid present in solution at different pH values. The analysis of the interfacial behaviour was performed by tensammetric measurements using an ac phase selective polarographic method of pH = 4, 6 and 12. It has been shown that the adsorption isotherm. (Frumkin type) is congruent with respect to the potential, with a slight attractive interaction factor at pH = 4, but higher and repulsive at pH = 6 and 12. At pH = 4 the species adsorbed seems to be the neutral one, white at pH = 6 and 12 the monoanionic species seems to be involved in the electrode interaction. Moreover, there is evidence that the molecule, in its neutral or ionic form, is always adsorbed with the tosyl group flat on the surface and the glycine moiety turned toward the solution.