N-(Trifluoroacetyl)-l-prolyl- (N-TFA-l-prolyl-) d- and l-amphetamine diastereoisomers were separated by high-performance liquid chromatography and confirmed by an interfaced mass spectrometer system, using the commercially available N-3,5-(dinitrobenzoyl)phenylglycine chiral column. A separation factor of 1.52 and resolution of 3.8 were observed. N-TFA-l-prolyl-d- and -l-methamphetamine diastereoisomers were only partially resolved. The chiral stationary phase-solute interactions were studied by varying the mobile phase (2-propanol in hexane). Results indicate the separation mechanism proceeds via dipolar and hydrogen-bond interactions between the chiral stationary phase and the solute. A modified "dipole-stacking" model takes into account these interactions and explains the difference in separability observed for N-TFA-l-prolyl-d- and -l-amphetamine and N-TFA-l-prolyl-d- and -l-methamphetamine.