Carbon nanotubes (CNTs) are known to have high thermal and mechanical stability and have the potential to be high-performance separation media that utilize the nanoscale interactions. CNT can be applied in long capillary tubes for the development of gas chromatography columns. A film of CNTs can be deposited by chemical vapor deposition (CVD) to form the stationary phase in the open tubular format. Altering the CVD conditions can vary the thickness and the morphology of the CNT film, which opens the possibility of selectivity tuning. The ability to fabricate long tubes coated with CNTs can be readily employed in other gas- and liquid-phase separations as well.