Visualization of solute migration in liquid chromatography columns

By matching the refractive indices of the mobile phase, the stationary phase and the material of the bed enclosure, one can render transparent to the eye the chromatographic column which is normally opaque in nature. As a result, band visualization is readily obtained. High-definition on-column detection becomes feasible by using a photographic detector instead of the conventional post-column, on-line (UV-Vis or similar) detector. Quantitative information regarding the concentration distribution in the band is obtained by utilizing optical scanners to obtain a digital image and computer imaging software. The processes of data collection and image analysis are discussed in detail and are illustrated by observing the concept of the infinite diameter column following a central point injection. The performance of the photographic detection method is compared to that of regular detection procedures. The efficiency of the column was determined with both on-column measurements and regular post-column measurements. A minimum reduced plate height (h) of 1.9 was recorded with post-column detection, in agreement with the average of the results given by on column detection. On-column analysis allowed the determination of the local plate height which was found to vary across the central region of the column between 2.7 and 0.95. (C) 1998 Elsevier Science B.V. All rights reserved.