Topics - Support
In chromatography the support
is an inert material made in the form of particles ca 100 to 150 micron in diameter, on which a stationary phase can be coated and then packed into a chromatographic column. The support gives permeability to the column and allows the mobile phase to flow through it while in direct contact with the stationary phase. The ideal support should be completely inert and should not contribute to the chromatographic process in any way. The early supports used by A. J. P. Martin in gas chromatography were made from Celite a diatomaceous earth (composed of the skeletons of diatoms). To reduce its activity, the Celite was washed with acid, then with water, then with acetone and gently ‘tumble dried’ in rotating flask. More recently, the washed Celite is also treated with hexamethyldisalazane to block surface hydroxyl groups. Other materials have been used as chromatography supports, calcined Celite (natural ground fire-brick and various forms of heat treated and chemically treated Celite), glass beads, polymer beads and for the separation of highly corrosive materials polytetrafluorethylene. Supports must have reasonable mechanical strength to survive the packing process and must not be friable as any ‘fines’ produced during packing will significantly decrease the column permeability and the resulting column efficiency.