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in figure 18.   The apparatus consists of a column (capped at the top with a stainless steel frit) having a precisely controlled internal diameter and finish. The column contains a close fitting piston. The piston, which is mounted on a constant-pressure hydraulic jack, can be moved throughout the entire length of the column. It contains a porous frit at the top and a channel for passage for the mobile phase through its center. The channel is connected to the detector and thence to the fraction collector. To pack the column, the piston is withdrawn to bottom of the column and the column filled with the measured mass of packing. The amount of packing used will determine the effective length of the column. The hydraulic jack is activated and the packing compressed to the maximum pressure which is determined by the mechanical strength of the packing. If the packing is crushed by the use of too great a pressure, many fines will be produced, which cause the permeability to be

The basic procedure is as follows. The two valves are set so that solvent from the reservoir is pumped through the injection valve to the column and the column outlet valve is set to the fraction collector. After the sample has been placed on the column, the column outlet valve is set to pass the column eluent back to the pump and the solvent selection valve set to the column eluent. Thus the mobile phase is continuously circulated through the column, through the detector, back to the pump and then back to the column. As a result the column is used over and over again many times, and each time the sample passes through the column, the resolution is improved. Unfortunately, the

The core houses the inner frit, through which the eluent percolates and exits at the base of the column to a detector and hence to a fraction collector. The outer frit constitutes the column inlet, and consequently the sample has initially an extremely large area of stationary phase with which to interact. This renders the loading capacity of the radial flow column also very high. It is interesting to note, that as the solute progress radially through the stationary phase bed towards the center, the effective cross-sectional area of the column will become smaller. Consequently, the plate volume of the column will decrease (

The method used for packing radial columns is depicted in figure 33. The packing is prepared in the form of a slurry and is pumped directly into the column between the two frits. The column exit to the detector and fraction collector is closed, and, as a result, the slurry solvent passes through the outer frit and exits via the normal mobile phase inlet port. The columns are very easily unpacked by adopting the reverse procedure. Figure 34. The Separation of Some Large Biomolecules Using Radial-Flow Reverse Phase Chromatography