Calcium and strontium hydroxyapatites (HA) were synthesized via a microwave accelerated inorganic sol-gel method. The acid-base properties of synthetically prepared phosphates are investigated at ambient temperature, by potentiometric titrations. Potentiometric mass, time and surface charge titration techniques were used to achieve this purpose. Isoelectric point (IEP) is evaluated as the pH of the intersection point of the suspension or time titration curves. For both phosphates the point of zero charge (PZC) is equivalent to isoelectric point indicating no specific adsorption of ions other than the potential determining H+/OH– ions at the surface. PZC (IEP) values of 6.4 and 7.2 were found for Ca-HA and Sr-HA, respectively.
