A novel method for the detn. of partition coeffs. in aq.-org. two-phase systems is described. It is applicable for characterizing the distribution of substances undergoing proton dissocn. in the aq. phase. The method is based on titrn. by means of the org. phase. A linear form of the resp. model is given for parameter estn. by linear regression. This strategy is used for the detn. of the partition coeffs. of some N-unprotected n-alkyl esters of phenylalanine in various aq.-org. biphasic systems. These esters are of interest for the optical resoln. of phenylalanine with chymotrypsin. [on SciFinder (R)]