Annular Column

Compared to the continuous annular chromatography systems sold by Isopro International and used throughout the ORNL studies, the P-CAC units developed by Prior Separation Technology feature several design modifications which will be presented hereafter. As can be seen from Fig. 3, the P-CAC system consist of three major parts the P-CAC head, the annular column, and the drive including the control panel. Figure 3 represents a schema of the laboratory sized P-CAC used as a Research and Development tool. 

The annular column consists of an outer and an inner cylinder standing one inside the other and held together by the ground plate. Depending on the material, the outer cylinder withstands an operating pressure of maximal 3 bar in the case of the glass cylinder and maximal 10 bar in the case of the stain-... 

The space between inner and outer cylinders forms the annulus. The column bottom plate is made of stainless steel and typically contains 90 exit holes below the annulus. The holes are covered by a filter plate to keep the stationary phase in place. Three different column sizes are available for the laboratory P-CAC unit the physical characteristics of the different annular columns are summarized in Table 1. The collection of the different fractions at the lower end of the annular column is regulated by a fixed glide ring system. Each chamber in the fixed glidering corresponds to an exit holes in the bottom plate of the column. The number of exit holes equals the number of chambers. The fixed glide ring system allows the continuous and controlled recovery of the separated fractions at the end of the column. Thus cross contamination is avoided and precise fraction collection is ensured. The whole process of collecting the fractions is conducted in a closed system. Unused eluent can be easily recycled. 

Blanche et al. [45] showed that the P-CAC technology is very promising for the purification of Plasmid DNA at preparative scale especially when resins with low binding capacities for the product of interest are used. The aim of the study was to purify the Plasmid DNA out of a clear lysate of E. coli. The lysate containing RNA, nicked DNA, as well as the Plasmid DNA was loaded onto the annular column filled with Poros 20 R2 beads as the stationary phase. The chromatographic process for the purification is shown in Fig. 7. 

The feed is introduced at the top of the annular column at the 0° position. The feed solution is followed by a wash buffer, which is introduced to the annular column through the main inlet port. A 1 vol.% mixture of 2-propanol in a 100 mmol/1 ammonium acetate buffer was used as wash buffer. In the washing zone the nicked DNA followed by the RNA are eluted from the column according to their affinity to the resin. At 180° offset from the feed nozzle the elution buffer (5 vol.%) 2-propanol in 100 mmol/1 ammonium acetate) was pumped to the annulus of the column. The elution buffer was used to strip off the bounded Plasmid DNA. Regeneration of the column was achieved by a 20 vol.% mixture of 2-propanol in 100 mmol/1 ammonium acetate buffer. All of the above-mentioned steps, i. e., feed, wash, elution, and regeneration, were done simultaneously and continuously on the P-CAC system. 

Rotary annular columns and rotary disc columns... 

With these columns as described by Thornton and Pratt 34 and Vermijs and Kramers 351, mechanical energy is provided to form the dispersed phase. The equipment is particularly suitable for installations where a moderate number of stages is required, and where the throughput is considerable. A well dispersed system is obtained with this arrangement. Figure 13.38 shows a rotary annular column. 

THORNTON, J. D. and Pratt, H. R. C. Trans. Inst. Chem. Eng. 31 (1953) 289. Liquid-liquid extraction. Part VII. Flooding rates and mass transfer data for rotary annular columns. 

At the top of the column the feed injection port is situated at a fixed position. Over the whole remaining circumference of the packed bed the eluent is introduced into the column and moves towards the bottom. The annular column rotates at slow velocities. This rotation results in a crosscurrent movement of stationary and mobile phase. The components of the feed mixture are separated into several product streams, which can be withdrawn at the bottom of the column at fixed port positions. A batch chromatogram can easily be transferred to an annular chromatographic system by replacing the retention time by positional degrees. Therefore productivity is... 

Figure 1.5 Chromatographic system based on a rotating annular column. Reproduced with permission from A.. Howard, G. Carta and C.H. Byers, Ind. Eng. Chem., 27 (1988) 1873 (Figs. 1 and 1). (c)1988 American Chemical Society.

Rotating annular column An implementation of preparative chromatography using a cylindrical, annular column rotating aroimd its axis. A continuous feed stream is injected at a fixed position just above the packing. Each component band follows a helical trajectory and is collected as a continuous stream along a fixed sector of the outlet annulus. 

Chini ZitteUi G, Rodolfi L, Biondi N, Tredici MR Productivity and photosynthetic efficiency of outdoor culmres of Tetrasehnis suecica in annular columns. Aquaculture 261(3) 932-943, 2006. 

Rotary columns. The rotary annular column, - 21 as shown in Fig. 4.13,... 

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