A capillary column (10) including monodispersed particles. The capillary (10) is formed using a suitable substrate, wherein two plates (12, 18) are bonded together. At least one of the plates (12, 18) includes a channel (14) where particles are housed. Particle bead positions are of defined and equivalent diameter are arranged along the longitudinal axis (16) of the housing structure. These positions are used to position packing material used to occupy the column (10). The particle beads themselves are of equivalent diameter.