FABRICATION OF COLUMNS FOR OPEN-TUBULAR LIQUID-CHROMATOGRAPHY USING PHOTOPOLYMERIZATION OF ACRYLATES

In liquid chromatography, a significant improvement of separation can be achieved by using 5-10-μm I.D. open capillaries instead of packed columns. In these capillaries relatively thick (0.3-2 μm) films of stationary phases are required. These are difficult to prepare if polymer solutions are to be used. The fabrication of thick polymer films inside quartz-glass capillaries using chain cross-linking photopolymerization of monomers in liquid solution rather than cross-linking of polymers cast from solution is described. In a 9-μm capillary a film thickness of about 0.3 μm was readily prepared and plate numbers of 7 · 104 to 1.2 · 105 m-1 were obtained. The photopolymerization process can be carried out under either static or dynamic conditions. The latter method facilitates the manufacture of long columns with a length of several metres. The experimental conditions for making smooth coatings using a siloxane acrylate together with lauryl acrylate as a reactive diluent, and methods for inspection and testing of these columns, are described. © 1990.