Home-made column packings

Commercially successful methods for the production of chemically bonded polymer phases suitable for HPLC have not been widely advertised and can only be referred to in general terms. Nevertheless, there are two principle methods for their production. Firstly, modification of a pre-formed support is possible providing that suitable sites are available. Alternatively, a method which has proved popular with polystyrene-type supports is to prepare the required support by copolymerisation of appropriate monomer units. 

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It should be in volumetric excess compared to the column s geometric volume. Many suppliers sell (expensive) column packing devices that are suitable for preparative and semi-preparative columns. A simple, home-made, column packing device can be assembled by joining two HPLC columns with a double female joint—the first column acts as a reservoir, the second is the column to be packed. 

Clamp either a pre-packed or home-made column vertically in a retort stand and remove the Luer cap. 

Figure 17. Instrumental set-up of preparative-scale gas chromatography in a conventional GC apparatus (Carlo-Erba, HRGC 5300). Tim home-made packed column (4 m x 7 mm (i.d.)) utilized the modified condenser of a discarded rotary evaporator.

Figure 14 An home-made HPLC column packing device.

A. technique not as commonly used as chemical methods it can none the less provide good yields of eluted antigen in a small volume without subjecting it to extremes of pH or denaturants (40, 41). It requires the use of additional apparatus, either home-made or commercial (e.g. Bio-Rad Model 422 electro-eluter). The washed matrix canying the adsorbed antigen has to be transferred from the column to an electroelution tube for the process to be carried out, so is more suited to self-packed or batch processed material rather than ready-packed colimuis. The antigen is eluted by the electric field into a small chamber sealed with a dialysis membrane and can be recovered in a small volume (400-600 JJ.1) of suitable buffer. The membrane enclosed chamber can be obtained with membranes of different molecular wei t cut-off to suit the size of the protein being eluted. 

Yebra et al. [83] used a continuous-flow procedure for the indirect determination of sodium cyclamate by flame atomic absorption spectrometry (FAAS). This method is based on oxidation of the sulfamic group derived from cyclamate to sulfate in acidic conditions and in the presence of sodium nitrite. The procedure is adapted to a flow system with precipitate dissolution (Figure 24.11), where sulfate formed is continuously precipitated with lead ion. The lead sulfate formed is retained on a filter, washed with diluted ethanol, and dissolved in ammonium acetate (because of the formation of soluble lead acetate) for online FAAS determination of lead, the amount of which in the precipitate is proportional to that of cyclamate in the sample. In this work a home-made filtration device was used made of a Teflon tubing packed with a cotton pulp and the ends of the filter column were plugged with filter paper (chamber inner volume 141 J,L). This precipitate collector was effective in retaining the precipitate and did not produce excessive back-pressure if the precipitate was dissolved following each precipitation cycle. 

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