Patent GB-1233907-A (GB)
IPC: B01L99/00
Filed: 1968-04-19
Abstract: 1,233,907. Coated tubes. INCENTIVE RESEARCH & DEVELOPMENT A.B. 19 April, 1968 [20 April, 1967], No. 18572/68. Heading B2E. [Also in Divisions B3, C7 and G2] A glass, quartz or like tube for use in electrophoresis apparatus which is straight has constant wall thickness and smooth inner and outer surfaces, is provided with a neutral hydrophilic coating on the inner wall to increase flow resistance to eliminate electroosmotic effect. The coating may be of a polymer which does not react with water to produce ions, e.g. methyl cellulose, formaldehyde or polyethylamide. The tube may be prepared for coating by grinding the inner and/or outer suprfaces by reciprocating the tube contact with an abrasive compound along its axis. Grinding. In the grinding process for the outer surface a block 10, Fig. 1, having wheels 11 running on steel rods 12, has a V-channel 10a containing a suspension of grinding powder, e.g. carborundum. A tube 13, e.g. of quartz, is filled with quicksilver to press it against the grinding medium. The tube is rotated, by a motor 14, and the block is reciprocated by a motor (not shown) whereby the outer surface of the tube is ground. For grinding the inner surface of the tube 13, the latter is clamped between V-channeled metal bars 14, 15, Fig. 2, mounted in metal plates 17, 18 and rotated by a motor 16 on the plate 17. The plates 17, 18 are connected by side plates 19, 20 and the whole assembly is vertically reciprocated, by a motor (not shown), on guides 21, 22 clamped between metal plates 24, 25. A copper wire 23 clamped between the plates 24, 25 passes through the tube. Grinding powder, e.g. carborundum in suspension, is placed in the tube. The copper wire is replaced at intervals by wire having successively greater diameters. The outer surface is then polished, using a suspension of iron oxide in water which is poured on a support, e.g. of wood coated with pitch. The support is moved back and forth along the rotating tube. The inner surface is polished by filling the tube with a suspension of iron oxide and moving it up and down over a rotating polyvinychloride rod coated with pitch. Coating. The coating of the tube bore provides a high viscosity solution or a gel which adheres to the tube. A water soluble polymer may be used, but should not be so soluble that it is rapidly dissolved by the buffer solution in the tube; it should not contain ionizdole groups. In one example, 0.4g. methyl cellulose is dissolved in 100 ml. distilled water, and 7 ml. formic acid (as catalyst) and 35 ml. formaldehyde added with stirring. The tube is filled with the solution and after 5 min. the tube is drained and placed in an oven at 120‹C for 40 mins to effect cross-linking; hydroxyethyl cellulose may be used instead of methyl cellulose. In a modification, polyacrylamide is used to provide a high-viscosity solution without cross-linking. Alternatively, polyacrylamide may be formed by polymerization in the tube from a monomer solution comprising, e.g. acrylamide, N-N'- methylenebisacrylamide, #-dimethylaminopropionitrile and ammonium persulphate in distilled water, the solution being rendered highly viscous by the addition of methyl cellulose or non cross-linked polyacrylamide. A polymer may be used which is not watersoluble but which expands in water. The polymer is dissolved in an organic solvent, the tube is filled with the solution and after draining the solvent is removed, e.g. in an oven. Methyl cellulose with a methoxyl content of about 30% and a hydroxypropoxyl content of about 10% is dissolved in 80% ethyl alcohol. Alternately, polyvinylacetate in which about half of the acetate groups have been replaced by OH groups to make it more hydrophilic is dissolved in 50% ethylalcohol.