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Unformatted text preview: for Chem 422
10. There is a minimum in a plot of plate height versus flow rate because band
broadening due to longitudinal diffusion effects decreases with increasing flow
rate while broadening due to mobile-phase and stationary-phase mass-transfer
effects increases with increasing flow rate. Since longitudinal diffusion is much
less a factor in liquid chromatography, the minimum plate height is found at a
much lower flow rate than for gas chromatography. 11. Gradient elution is a method used in liquid chromatography in which the
composition of the mobile phase is changed continuously or in steps in order to
improve separations. 12. The variables that...
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