A planar separation component for gas chromatograph includes a substrate made of aluminum, a porous anodic aluminum oxide separation member, and a cover unit. The substrate has a planar body, and a first flow channel having a first inlet and a first outlet. The separation member is formed on the substrate, and has a channel-defining wall defining the first flow channel and a plurality of nanosized pores in spatial communication with the first flow channel. The cover unit is bonded to the planar body for covering the first flow channel. Methods for manufacturing the planar separation component and separating a mixture containing compounds different in boiling point using the planar separation component are also disclosed.