  We analyze the changes in the vicinal acidity (pH) at a spherical amphiphilic
membrane. The membrane is assumed to contain solvent accessible, embedded,
dissociable, charge regulated moieties. Basing our approach on the linear
Debye-H\"uckel as well as the non-linear Poisson-Boltzmann theory, together
with the general Frumkin-Fowler-Guggenheim adsorption isotherm model of the
charge regulation process, we analyse and review the dependence of the local pH
on the position, as well as bulk electrolyte concentration, bulk pH and
curvature of the amphiphilic single membrane vesicle. With appropriately chosen
adsorption parameters of the charge regulation model, we find a good agreement
with available experimental data.
