Methods have been found to prepare fused silica capillary gas chromatographic columns where the stationary phase is a molecular sieve affixed to the silica capillary wall without the aid of an organic binder by modifying the interior surface of the silica prior to contact with the molecular sieve. These totally inorganic columns greatly expand the application and range of gas chromatographic separations and allow the use of non-traditional carrier gases, even air, while not degrading the separation of components. The columns are films of small molecular sieve particles affixed to a silica surface modified by such treatments as hydrogen peroxide, alumina deposition, or silica deposition followed by fixation at 80.degree.-160.degree. C.