To improve the efficiency of gas chromatography for hydrogen isotope separation near room temperature, feasibility of new columns was examined for H-D and H-D-T mixture gases. One kind of the column was the mixture of Pd-Pt alloy and Cu powders as the previous study. But special attention was paid for preparing the separation column; Pd-Pt alloy particles below 200 mesh was mixed with copper powder of 150–200 mesh and packed into a loading tube of stainless steel as uniform as possible. The separation for H-D mixture gases could be remarkably improved by this column even at temperatures around 300 K. This column also could separate tritium as T2 from H-D-T mixture gas containing only 0.13 % T. The other column was prepared by Pd-Pt alloy supported by porous SiC powder for economical use of the expensive alloy. Although this column gave similar separation chromatograms, the separation efficiency was still insufficient and further studies are required.