Dual diatom skeletons:

The individual dual diatom skeletons are extremely small, highly porous and have a high surface area. There are five forms or kinds of chromosorb that is Johns Manville's registered trade mark for GC support material i.e., chromosorb A, G, P, W and T. Every is available either untreated or treated and within a variety of mesh ranges. Supports are commonly sized through screening by standard ASTM screens. Mesh numbers refer to the number of openings per linear inch. Particles in which will pass through 60 meshes but not 80 meshes are referred to as 60-80 mesh. The more uniform the packing, the smaller the Eddy difussion and more the column efficiency. For 3 mm I.D. Columns, 100/120 or 80/100 mesh support is preferred, for 6 mm I.D. columns, 40/60 or 60/80 mesh is appropriate.

The chemical composition of a few of these supports is given in Table.

Table:   Chemical Analysis of Supports