Press-fit glass connectors for GC capillary columns are normally discarded after use: the gas-tight seal formed between the polyimide layer of the column and the tapered section of the connector is so strong that any attempt to disconnect the column from the glass is fruitless; part of the column will always be retained, preventing further use of the connector. Rinsing the connectors with various solvents, strong acids, and alkalis has failed.
The connectors can, however, be reused after heating at 550 "C; at this temperature the polyimide layer disappears completely.
After use, the connector or splitter (Pressfit, Schmidlin Labor + Service AG, Switzerland) is removed by cutting the column at a distance of about 1 cm from the glass. The glass connector is placed in a crucible which is transferred to an oven. The temperature is increased to 550 "C and held at this temperature for three hours, after which the oven is cooled to 200 "C. The crucible can then be removed and cooled to room temperature. (If the crucible is removed at 550 "C, the glass will crack.)
The column sections extending from the glass may now be easily withdrawn and the splitter or connector re-used We have tested this method repeatedly without observing any drawbacks other than the disappearance of the colour codes from the connectors We use press-fit splitters for dividing the eluate of a GC column to flame ionization and Hall electrolytic conductivity detectors, and several additional splitters and reducing connectors for trapping fractions containing organochlorine compounds in coils of fused silica capillary tubing Each assembly for trapping three fractions requires the use of three two-way splitters and three connectors, if the glass parts were not reusable, the high cost of the splitters would have presented an obstacle to the performance of such experiments, especially in view of the knowledge that the first attempts were unlikely to be successful Ms