Surface Characterization of Phenylpropanolamine Drug by Inverse Gas Chromatography

The surface thermodynamic properties can be used to understand the interactive potential of a drug surface with a solid or liquid excipient during its formulation and drug release process. The retention data were measured for n-alkanes and polar solutes at intervals of 5 K in the temperature range 318.15–333.15 K by Inverse Gas Chromatography (IGC) on the solid surface of phenylpropanolamine (PPA) drug. The retention data were used to evaluate the dispersive surface free energy, , and Lewis acid-base parameters, and , for the PPA drug. The values, , were decreasing linearly with increase of temperature and at 323.15 K the value was found to be  mJ/m2. The specific components of enthalpy of adsorption of polar solutes have been applied to evaluate Lewis acid-base parameters. The and values were found to be and , respectively, which suggests that the PPA surface contains more basic sites and interact strongly in the acidic environment.