Characteristics of moving feed-injection system by gas-liquid chromatography

Abstract

The moving feed-injection chromatography was compared with the conventional preparative case and the characteristics of the system were fully developed by using the theoretical plate model. The experiments for the separation of diethylether(DEE) and dichloromethane (DCM) by gas-liquid chromatography were carried out to test the validity of the model. The chromatographic beds consisted of 10 segmented columns, each of which was 10mm. in diameter and 26 cm. in length. The variables were the feed port velocity, column temperature, total feed-injection time, the number of ports for feed injection, and particle size. Theoretically and experimentally it was proven that the moving feed system had much sharper bands, improved resolution and impurity, and higher outlet concentration when compared to the conventional preparative case. Moreover, the system was very flexible to some degree in that the achievement of the separation could be adjusted by the velocity of feed-injection port, $^V$feed. The feed port velocity had an optimum value with respect to the resolution and impurity. Effect of the column temperature was serious. The lower temperature gave a higher resolution but, also, wider band-widths. At the higher temperature, resolution was lower with decreasing retention times of the two components. There was a limitation in improving the resolution as the total feed time increased. Even though the feed port velocity was the same, the larger number of feed ports gave the better result. The finer particle size resulted in an improved resolution. But, in this case, the total bandwidth increase.