A study on glass open tubular columns used in gas chromatography

• Published in: Bunseki kagaku Vol. 23; no. 4; pp. 339 - 347
• Main Authors: SAITO, Hisashi, FURUKAWA, Osamu
• Format: Journal Article
• Language: English
• Published: Tokyo Japan Science and Technology Agency 1974
• ISSN: 0525-1931
• DOI: 10.2116/bunsekikagaku.23.339

In most of papers relating to the making of the glass wall coated open tubular (WCOT) columns, the pretreatment process, which means the inner surface modification of the glass capillary by various corrosive reagents, was regarded as indispensable to achieve the uniform stationary phase coating. We aimed in this paper to dispense with this complicated pretreatment process and produced glass WCOT columns which have no modification on their inner surfaces to investigate the column characteristics. For the preparation of glass WCOT columns, glass capillaries (0.7 mm outside diameter, 0.25 mm inside diameter, 20 m long) were produced by using a commercially available glass drawing machine, and they were coated with different stationary phases by the dynamic coating method by the use of a newly constructed coating apparatus. The coating apparatus was so constructed that the flow in the glass capillary could be switched without any pressure change by the one-touch action from the gas to the stationary phase solution and vice versa, and that the fluctuation of the flow rate of the stationary phase solution in the capillary was minimized by the two auxiliary capillary attached before and after of the main. For searching the optimum coating conditions, the relationship between the coating flow rate and the column efficiency, and the relationship between the coating flow rate and the partition ratio k were studied by using 0.3 ml of a 10% (w/v) OV-17/n-hexane solution. The suitable coating flow rate was found to be in the range 5 to 8 cm/sec, and the average film thickness coated on the capillary inner wall was confirmed to be proportional to the coating flow rate. From these results, glass WCOT columns having no modification on inner surface were produced, and attached to the newly constructed all-glass capillary column holder, then examined by gas chromatography. The maximum number of theoretical plates determined at 250°C for cholestane was 2300/m. To examine the temperature stability and lifetime, these columns were used continuously for 840 hrs under the condition of the 250°C column temperature, and the minimum HETP values before and after that were compared. Only 30% change could be found out between them. These results show that the glass WCOT columns having no modification on inner surface is promising for the practical use. For the application, various samples mainly related to biochemical substances such as sterols in soybean, a mixture of cholesterol and cholestanol, amino acids, a mixture of steroids, etc. were analysed with the glass WCOT columns coated with OV-17 (phenyl methyl silicone), OV-101 (dimethyl silicone), Poly I-110 (polyimide). Campesterol and stigmasterol, cholesterol and cholestanol, which were very difficult to resolve completely with a conventional packed column, were separated with these glass WCOT columns by 3.6 and 2.0 of peak resolution R respectively. Good results were obtained for other substances with these glass WCOT columns.