The determination of HETP and column efficiency for an annular preparative-scale gas-liquid chromatographic column

The purpose of this investigation was to design, build, and test a preparative-scale column which contained a blocked-off center tube, thus forming an annular space for the packing.

The chromatographic system for this study consisted of 1-methylnaphthalene injections with helium carrier gas and a liquid phase of Craig polyester succinate on crushed firebrick. The analytical column had an inside diameter of 0.061 inches. For the preparative-scale column, the outer diameter was. 2.075 inches and the inside diameter was 1.050 inches. The operating temperature for both columns was 300 degrees Fahrenheit. The flow rates were 0.012 and 10.30 liters per minute for the analytical and preparative-scale columns, respectively.

Several sample sizes were injected on both columns. Variation of HETP with sample size was determined. Preparative-scale column efficiencies were calculated from average HETP's at all sample sizes tested.

Efficiencies of 36.5, 33.4, 58.2, 69.3, and 52.7 per cent relative to the analytical column were calculated for preparative-scale injections of 0.1, 0.3, 0.5, 0.7, and 0.9, milliliters, respectively. HETP for the preparative-scale column was very sensitive to variation in sample size in the range from 0.l to 0.9 milliliters. HETP for the analytical column was not sensitive to variation in sample size in the range from 0.12 to l.00 microliters, as was expected from literature data.