Preparation Of Three Stationary Phases In High Temperature Gas Chromatography And Their Chromatographic Performance Evaluation

With the development of science and technology, there are increasing demands in high temperature gas chromatography (HTGC). It is known to all, there are mainly two aspects which affect the use temperature of the HTGC. First, the thermal endurance of stationary phases. second, the materials of the capillary columns. The two facts must be changed better, the HTGC will be got.There are several ways to improve gas chromatography (GC). Firstly, stationary phases with good thermal stability were used in GC. Currently, the stationary phases people used mostly were polysiloxane which were commercialized, by modifying the polysiloxane, the stable stationary phases were obtained. Secondly, the capillary column material would be changed. The most use column is the capillary column with the wall coated by polyimide. Not only the flexibility of the column coating with polyimide is pretty good, but also there is no distance between the polyimide and the column. But it had a fatal weakness, which is the using temperature was not very high. The use temperature of common polyimide must be below 360～380℃, the polyimide with good properties could bear 400～420℃. In high temperature, the polyimide was degenerated and could not be used in a long time. In addition, stainless steel capillary column was used instead of capillary column, due to the lively inner surface of stainless steel, it is not fit to be used to analyze the active substances. The capillary column coating with metal outside also shows good thermal stability, but there were different coefficient of expansions between the metal and quartz, it was not used for a long time. And the production cost was very high, which was a kind of adverse factors obstructing the wide use of the capillary column.In order to solve the problems above, at first, the polysiloxane was instead by polysilazane. The degradation of the polymer can be restrained by the structure of cyclodisilazane, and the temperature can be improved. In the use of the capillary column coated with polyimide outside, the maximize allowable operating temperature was more than 400℃, and the baseline drift was below 1.0mv.Another column we produced was improved, not only stationary phase was modified, but also the material was changed. The common column coating with polyimide outside was hit in high temperature forming carbon film, and then nickel was electro less plated outside the carbon film. Carbon film can protect the quartz and can buffer coefficient of expansion. The polysiloxane was modified as the stationary phase we used, the maximize allowable operating temperature was higher than 410℃, and the using time was also increased. When the using temperature was 410℃, the baseline drift was below 1.2mv.At last, the method of preparation of sol-gel gas chromatography capillary column was introduced with cyclodisilazane as the stationary phase. The sol-gel capillary column was stable and can be used in high temperature, which owed to the chemical bonds between the inner wall of the capillary and the coating layer. And the method is simple, which can be produced easily.The three above method which was used to prepared GC capillary column was very useful for analyzing the mixture with high boiling point. The service time of the GC capillary column with excellent characteristics was longer than the common column.