Interpreting the difference between conventional and bi-directional plate-height measurements in liquid chromatography |
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Authors: | Hui Guo Douglas D Frey |
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Institution: | Department of Chemical and Biochemical Engineering, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA |
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Abstract: | An experimental and theoretical study was conducted of the column characterization technique in which plate heights determined using the conventional pulse-response method are compared with those determined using a bi-directional method where an eluite sample is introduced into one end of a chromatographic column and elution occurs at the same end after the flow direction is reversed inside the column. Experiments are presented for a micropellicular HPLC column before and after its performance has been degraded by repeated sample injections, for a low-pressure column containing nonporous glass particles, and for an HPLC column containing particles with 300 Å pores. The results obtained are interpreted in terms of several different theories which apply in various Fourier number ranges. It was shown that the transcolumn contribution to convective dispersion in a chromatographic column is largely responsible for the difference observed between conventional and bi-directional plate-height measurements and that a collocation method can be employed to develop a useful analytical expression for this contribution. |
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Keywords: | Bi-directional plate-height measurement Theory of chromatography Convective dispersion A term van Deemter equation |
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