A study of HETP and efficiency for an annular preparative-scale gas-liquid chromatographic column

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Virginia Polytechnic Institute and State University

The purpose of this investigation was to test the effect of sample size and carrier gas flowrate on the efficiency (relative to an analytical column) of an annular preparative-scale column.

The chromatographic system for this investigation consisted of η-methyl-butyrate injections with nitrogen carrier gas and a liquid phase of Craig polyester succinate on Chromosorb W. The analytical column had an inside diameter of 0.061 inches. The preparative-scale column had an outside diameter of 2.075 inches and an inside diameter of 1.050 inches. The operating temperature for both columns was 215 degrees Fahrenheit. A sample size range of 0.1 to 3.0 milliliters was studied on the preparative-scale unit; this corresponded to a 0.2 to 3.6 microliter range on the analytical unit. Carrier gas flowrates of 4305, 8610 and 17,220 milliliters per minute were studied on the preparative-scale unit. This corresponded to flowrates of 5, 10 and 20 milliliters per minute on the analytical unit.

Preparative-scale efficiencies of 20.43, 41.95 and 45.34 per cent were obtained at a sample size of 0.1 milliliter. The above efficiencies correspond to flowwates of 4305, 8610 and 17,220 milliliters per minute. As the sample size was increased to 3.0 milliliters the corresponding efficiencies dropped to 7.20, 17.71 and 27.11 per cent respectively.