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SummaryFive commercial varieties of uncoated fused silica capillary tubing used in high resolution gas chromatography were subjected to cobalt-60 gamma radiation. The advantages and superior performance of fused silica open tubular columns coated with OV-1 and subsequently immobilized or crosslinked in situ by radiation is reported in a previous paper in this Journal; however, in this investigation a loss in flexibility of irradiated capillaries was also noted. Quantitative measurements on flexibility were performed on specimens of irradiated fused silica capillaries, indicating that changes do indeed occur upon irradiation. Scanning electron micrographs also illustrate slight deterioration of the outer protective polyimide coating. Most surprisingly, it was alsoestablished thatavariationdoesexistintheflexibilityofthe commercially available raw material studied.

Commercially available OV-17 was partitioned into a low and a higher molecular weight fraction by supercritical fluid extraction with carbon dioxide. This higher molecular weight fraction is more thermally stable than the original OV-17 due to its more viscous and gum-like nature. Based on the growing evidence in the literature that a deactivating agent for fused silica open tubular columns should be compatible with the stationary phase, a precoat of 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane was applied prior to the static coating of high molecular weight OV-17. Fused silica OV-17 columns prepared in this fashion are stable up to 300%.