COLUMN EFFICIENCY AND RADIAL HOMOGENEITY IN LIQUID-CHROMATOGRAPHY

Local, on-column electrochemical detection was carried out in the amperometric mode at different points of the column outlet cross-section. This permitted the determination of the spatial distribution of analyte molecules within the chromatographic zone at the column exit. The radial distribution of the peak-maximum velocity, the local efficiency and the analyte concentration were determined for a commercial column and for several laboratory-packed columns made with different solid particles and with a commercial silica-based stationary phase. An important region of the packing close to the wall is denser, has a lower permeability and a lower efficiency than the core of the packing. The concentration along the wall is lower than average, in part because of the lower efficiency.