New approach of the extrapolation procedure in the determination of acid-base constants of poorly soluble pharmaceuticals.

A new approach to the graphic extrapolation procedure is proposed for the determination of pK-value of pharmaceuticals poorly soluble in water. It is based on a direct potentiometric method for the determination of acid-base constants in non-aqueous and mixed solvents in which no preliminary calibration of the galvanic cell is needed (glass and calomel electrodes). In this way the applicability of the graphic extrapolation procedure is enlarged for a great number of organic solvents miscible with water for which no buffer pH-standards are available.