Detection of voids in packed chromatographic columns

The objective of this research has been to develop the understanding of the detection of voids in packed chromatographic columns using one component added to another pure carrier gas. This has been successfully accomplished with an apparatus in which the transients displayed by adding the small gas perturbation flow produced mirror images of the transients displayed by removing the perturbation flow. Flow rates are measured in these experiments. The transients are displayed when a composition front passes a void in the column. The achievement of the objective is mainly due to the way in which the perturbation to flow is introduced into the system. Instead of the perturbation flow being switched from one column to the other, the flow is simply added and removed sharply from a single column. This has involved the development of a gas sample mixing device which greatly reduces the problem of dead volume. The dead volume causes different effects when the perturbation flow is added and when it is removed. Another aspect of the new system is that the perturbation flow rate can be measured exactly by switching the gas through a soap film bubble flowmeter. Further development and re-design of the back pressure regulator have successfully eliminated the effect of atmospheric pressure fluctuation on the noise' level on the flow rate measurement. Analysis of the deviation in the flowrate caused by desorption and resorption as a composition front passes through a column shows that this research provides, quick, accurate, and a simpler method of obtaining composition residence times from the flow rate records.