Moving port technique

The flow rate and the pressure drop per unit length of the chromatographic column are much lower for the stationary port compared to the moving port system. Also, the moving port system is much less capital intensive. The moving port technique, however, is calculated to require only one-third of the column volume and ion exchange volume and two-thirds of the desorbent volume compared to the stationary port technique. 

After the expiration of the UOP patent covering the rotary valve, there have been several modifications to the moving port technique by Amalgamated Sugar,l l Illinois Water Treatment,and Mitsubishi. Each manufacturer has its own proprietary approach for the establishment and control of the chromatographic pattern. 

This is the equivalent of the injection port for the GC technique. With GC you could inject through a rubber septum directly onto the column. With HPLC it s very difficult to inject against a liquid stream moving at possibly 1000 psig. That s why they invented injection port valves for HPLC you put your sample into an injection loop on the valve that is not in the liquid stream, then turn the valve, and voila., your sample is in the stream, headed for the column. 

A simultaneous countercurrent movement of solid and gaseous phases makes it possible to enhance the efficiency of an equilibrium limited reaction with only one product (Fig. 4(a)) [34]. A positive effect can be obtained for the reaction A B if the catalyst has a higher adsorption capacity for B than for A. In this case, the product B will be collected mainly in the upper part of the reactor, while some fraction of the reactant A will move down with the catalyst. Better performance is achieved when the reactants are fed at some side port of the column inert carrier gas comes to the bottom and the component B is stripped off the catalyst leaving the column (Fig 4(a)). The technique was verified experimentally for the hydrogenation of 1,3,5-trimethylbenzene to 1,3,5-trimethylcyclohexane over a supported platinum catalyst [34]. High purity product can be extracted after the catalytic reactor, and overequilibrium conversion can be obtained at certain operating conditions. 

A modification of this technique, the simulated countercurrent moving-bed chromatographic reactor [35], comprises several catalyst beds (Fig. 4(b)). The locations of inlet and outlet ports between the catalyst beds are changed sequentially, thus the countercurrent movement of solid and gaseous phases is simulated in a discrete manner. Such an operation avoids the technical difficulties (catalyst attrition, nonuniformity of solid flow, etc.) associated with solid-phase movement. Part of the reactor sections can be purged by the carrier gas. To increase the separation effect, a bed of adsorbent can be added in each section. 

GC is inherently a technique for the study of volatile compounds. Fig. 1 shows a block schematic of the components that comprise a typical GC instrument equipped with split injection port and capillary column. For headspace sampling, a gaseous sample is introduced by injection into an inert moving gas stream called the mobile phase or carrier gas. 

Different manifold geometries have been proposed for implementing in-line SPE in flow analysis, generally involving the placement of a minicolumn before, at or after the sample introduction port. Alternatively, by integrating SPE within the detection unit, moving beads, hyphenated techniques and/or commutation facilities can be exploited, as discussed at the end of this section. 

Another group of FUSO combines chemical reaction with separation of products. These methods can employ a reactor with circulating bed of catalyst [3,4] or by periodic changes of feed and product ports in a reactor with several fixed beds, known as simulated moving bed reactor [5-7]. Reaction and separation can include periodic pressure changes using the known separation technique of pressure-swing adsorption. 

Exactly the same process takes place as that in the Hurrel system but, in effect, the valving makes the columns appear to move instead of the packing. Part of the feed moves with the mobile phase and is collected by a small take-off flow in front of the feed port (B + solvent). The other, more retained portion of the sample, accumulates in a column on the other side of the feed port and is collected by a another small take-off flow behind the feed port (A + solvent). This particular system ideally, produces two products and thus lends itself specifically to the separation of enantiomeric pairs. However, for effective separation with high purity yields, the stationary phase capacity for the two enantiomers must be fairly large and thus the phase system must be carefully selected. The technique has been successfully used to isolate single enantiomer drugs [15-17]. 

In contrast to the above technique, OVD injection begins during introduction of the cannula into the access port on its way into the intraocular space (Fig. 49) in order to move the iris towards the lens. 

To apply this technique the 179th Smoke Generator Company on 18 March moved from the harbor area toward the forward positions. The smoke line, now forming a ly-mile arc around the port, included nineteen generator positions on land and two generators mounted on Navy patrol craft in the harbor. (Map 4) The latter prevented enemy observation from the flanks of the concave contour of the coast line. 

Both the conventional basestock (lOOVI) and the RHC derived basestock (116 VI) were separated in a thermal diffusion column, see Figure 5. Thermal diffusion is an analytical technique that applies a thermal gradient across a narrow annular wall, driving the basestock sample in this space to move in a convection cycle.After about one week, the sample separates by density with the least dense, paraffinic species, at the top and most dense, clustered ring species, at the bottom, as shown in the right-hand illustration. Samples from each of ten ports can be characterized both for basestock properties and composition. 

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