The resolution of N-trifluoroacetyl (N-TFA) ter-isopropylesters of Ala, Ile, Leu, Val and Phe by gas chromatography on the (S)-5-isobutyl-$N^3$-phenyl-2-thiohydantoin as stationary phase was investigated. The phase was employed at several column temperatures $(140^{circ}C{sim}200^{circ}C)$ and the separation factors were $1.18{sim}1.45$ range for five amino acid enantiomers. The possible mechanism of chiral recognition was investigated by NMR technique and the association constant$(K_c)$ was calculated as 201.3(r=0.98) for alanyl derivative.