Changes in peak width and concentration at the inlet and outlet of a chromatographic column

Abstract

SummaryThe original plate model of chromatography is extended to the sorption process occurring at the column inlet and the desorption process at the column exit. At the column inlet it is shown that sufficiently wide feed bands undergo no change in concentration but a fall in band width, i.e., the volume of mobile phase occupied by the solute band is reduced. The reduction factor is (1 + k) where k is the mass distribution ratio (capacity factor). Narrower bands suffer partial reduction in both band width and concentration. On desorption at the outlet, however, the change is always in band width and not concentration. A perfect detector registers the true concentration-time profile of the band in the column if the solute mass fraction in the stationary phase is below lov3 at the column outlet. The risks of stripping the stationary phase at high solute concentrations in analytical and preparative or production gas chromatography are compared.

Laser beam deflection sensor as a detector for high-efficiency chromatography

“…However, the sensitivity of the concentration gradient method improves even more with on-column detection. Gaussian bands which travel through the column in the mobile phase are characterized by the same amplitude but they are more compressed ("sharper") than they appear after desorption from the column (13). The ratio of corresponding standard deviations can be expressed as ffD/<Tc = (k' + 1) where 0 is standard deviation of the desorbed peak while cc is the standard deviation of the on-column Gaussian band.…”

Direct examination of the injection process in liquid chromatographic separations

“…Schematic diagram of on-column fluorescence detection system for microcolumn liquid chromatography: I = injection valve, T = splitting tee, R = restricting capillary, FOP = fiber optic positioner, MONOmonochromator, PMT = photomultiplier tube, AMP = current-to-voltage converter and amplifier. chromatographic separations (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Although the methods of theoretical treatment vary widely, it is generally accepted that the influence of the injection process is dependent on the initial peak profile and the equilibration of solutes between the mobile and stationary phases.…”