Columns radial compression

Radial compression columns are used by Waters Associates (see section 4.3.1) [144-146,603]. A flexible-walled plastic... 

Turner and Warnock [56] determined miconazole in human saliva using high performance liquid chromatography. Deproteinated human saliva samples containing miconazole was chromatographed on a C8 reversed-phase radial compression column using 77% methanol in 0.01 M EDTA with 0.005 M w-nonylamine at a flow... 

Pietrzyk, D.J. and Cahill, W.J., Amberlite XAD-4 as a stationary phase for preparative liquid chromatography in a radially compressed column, J. Liq. Chromatogr., 5, 781, 1982. 

This assay is based on the separation and quantitation of bilirubin. The column was a C18 Novapak radial compression column. Solvent A contained 49% 0.1 M monobasic ammonium phosphate, 40% methanol, 10% acetonitrile, and 1% DMSO, adjusted with H3PO4 to pH 3.6. Solvent B contained 79% methanol, 20% acetonitrile, and 1% DMSO. The 16-minute run included a linear gradient from 50 to 100% solvent B in 3 minutes, maintaining 100% B for 13 minutes, followed by a return to starting conditions. The eluate was monitored at 450 nm, and detector response was linear with 0 to 500 pmol of bilirubin. 

Fig, 9, The chromatography of apolipoprotein A-1 on a Waters Cis radially compressed column (A) and on Spherisorb ODS (B). In each case the mobile phase was 19f triethylam-monium phosphate and the flow rate was 1.5 ml/min. Both analyses were made on 100 /ag of protein. Adapted from Hancock and Sparrow (1981d). 

The concentrates are analysed by High Performance Liquid Chromatography (HPLC) coupled to a fluorescence detector. Elution is performed using a gradient of methanol in a phosphate buffer on a Cj g radial compression column. In order to render the amino acids amenable to fluorescence detection ( X Xgjjj = 455 nm), it is first necessary to derivatize them using orthophtaldialdehyde (O.P.A.) in the presence of mercapto-2 ethanol. Up to 20 amino acids can thus be analysed and quantified, and the complete analysis takes only 35 minutes. Table 2 presents the most commonly determined amino acids during the course of this study. 

R2. Reid, A. D., and Baker, P. R., High-performance liquid chromatography of bile acids with a reversed-phase radial compression column. /. Chromatogr. 247, 149-156 (1982). 

Curry, S.H. Brown, E.A. Hu, O.Y.-R Perrin, J.H. Liquid chromatographic assay of phenothiazine, thiox-anthene and butyrophenone neuroleptics and antihistamines in blood and plasma with conventional and radial compression columns and UV and electrochemical detection. J.Chromatogn, 1982, 231, 361-376... 

Note In order to determine the interstititial fraction, one needs to know the interstitial volume and the column volume. The interstitial volume can be measured readily using a marker that is excluded from the pores. For beds in a fixed-volume container, the column volume is known as well, but it is unknown for radially compressed beds. However, the volume occupied by the particles can be determined from the pore volume, which also is easily measurable if the particle porosity is known. The particle porosity, in turn, can be determined in a separate experiment using the same markers for the totally included volume and the interstitial volume in a column of a known column volume. Therefore, after the particle porosity has been determined, the column volume in a radially compressed column can be calculated as the sum of the interstitial volume, the p>ore volume and the skeleton volume of the particle.)... 

The homogeneity of the bed of radially compressed columns can also be studied conveniently by injecting dyes into the b. The walls of a Radial-Pak cartridge are made of polyethylene and can be cut without disturUng the bed. The bands of the dye can then be easily studied. These studies confirm the high uniformity of a property prepared radially compressed bed. 

A better approach to the problem is the active compression of the bed through axial compression (13). This technique has not been used for analytical columns, but is widely practiced for large-diameter preparative columns. As is the case for radially compressed column, the permeability of an axially compressed column is lower than the permeability of an uncompressed column (14), but the effect is much smaller because of the lower compression factor. Axial compression maintains column efficiency. In repeated packing trials, reproducible efficiencies can be obtained, but the peak shapes reported do not indicate a good uniformity of the packed bed. There are no studies available yet that allow one to judge whether this is an intrinsic property of axial compression or if this is due to the technical difficulties associated with the packing of large-diameter columns. 

Also shown in Figure 3.13 are the actual results obtained for a steel column and a radially compressed column packed with the same particles. The results for the steel column follow closely the standard curve. The radially compressed column shows inferior results at high velocity. This is due to the convention used here that the apparent particle diameter in the column is determined from the permeability. Ra ally compressed columns have a denser bed, and thus a higher pressure drop. The particle diameter determined via the measurement of the permeability was S.7 fim instead of the true diameter of 8 /expected performance of a SJ-fim column is not met at high velocity. On the other band, the maximum of the curve for the radially compressed column matches the expectation. This is because the increased unfformity of the packed... 

Sarker, M., and G. Guiochon, Study of the Padcing Behaviour of Radial Compression Columns for Preparative Chromatography, J. Chromatogr. A683, 293-309 (1994). 

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