A dimensionless “relative-to-parent” RT was introduced, calculated as the RT ratio of a TP to its corresponding parent compound,in order to correct for chromatographic shifts among different analytical runs. The relative standard deviation (RSD) of this relative-to-parent RT for all TPs is between 0.2% and 1.7%. Gener-ally, a relative-to-parent RT 1(Table 1), the reduced polarity can be explained by their molecular structures. Compared to their parent compounds metoprolol and propranolol, these TPs lose their secondary amine group which is a major contributor to their polarity due to the strong specific intermolecular interaction (hydrogen-bonding) with the mobile phase[38].