Determination of the Extra Column Dispersion Occurring in the Different Components of a Chromatographic System

Abstract

The design and construction of it conductivity detector having a volume of 0.08 µl and a connecting tube volume of 0.36 µl is described. The detector is used to determine the extra column dispersion that occurs in the different components of a chromatographic system at the maximum flow rate normally employed with small bore columns (viz.20 µl/min). The correctly modified Valco (Houston, Texas) valve, having a sample volume of 0.2 µl, was shown to contribute 0.054 µl² to the overall variance of the eluted peak; a capillary connecting tube, 0.010 inch i.d., contributed about 0.093 µl² cm of length; a scintered frit, 1/16 inch and 0.020 inch o.d. thick, contributed about 0µl² and an ultraviolet (UV) adsorption cell contributed between 0.4µl² to 4.9 µl², depending on the geometry of the cell. It was also shown that coiling a connecting tube reduced the dispersion significantly at high flow rates, but not at the flow rates normally used with microbore columns.