Capital HPLC

Why use 4.6mm i.d. columns ?

Over the past twenty or so years, the most popular analytical HPLC column format has been the 4.6mm i.d. column. At the time of its introduction, this choice of a 4.6mm diameter column was dictated mainly by the limitations of the analytical instrumentation available then.
For efficient chromatography, the dispersion caused by external instrumentation must be small relative to the volume of the eluting peaks. One means of ensuring this to be the case, is to increase the effective peak volumes by increasing the column bore. However, with the improvements in instrumentation, particularly in the area of miniaturisation, it is now possible to reduce the
column bore and still maintain the efficiency of the column. This approach, which is made possible by the low dispersion characteristics of modern HPLC instrumentation offers the chromatographer a number of significant advantages over the use of conventional
4.6mm diameter columns.

Capital Narrow Bore Columns

Capital HPLC are able to supply high performance narrow bore columns of 3.2, 2.1mm and 1.0mm i.d., in a conventional column format, packed with any of the materials from our vast range.
In addition to the standard 4.6mm i.d. format, UCC cartridge inserts are available in both 3.2mm and 2.1mm i.d. formats. Both the 3.2mm and 2.1mm inserts are fully compatible with the standard UCC cartridge holder, so it is not necessary to purchase specific narrow bore holders. At present the UCC range is the only cartridge system available which supports 2.1mm i.d. inserts.

Solvent Consumption

The use of narrow bore columns leads to a considerable reduction in solvent consumption. From figure 1, which shows the relative solvent consumption for 4.6, 3.2, 2.1 and 1.0mm i.d. columns or cartridges, it can be seen that even a moderate reduction in diameter from 4.6 to 3.2 can lead to a 50% saving in solvent costs. Not only does this save on solvents, but also on time spent preparing mobile phases and cuts waste disposal costs. As can be seen from the diagram below, the use of 1.0mm diameter columns results in a 95% saving in solvent costs. With such savings in the costs of solvent, it is even possible to consider the use of more exotic mobile phases containing expensive additives, such as chiral selectors.

Perhaps the most dramatic effect of reducing the cartridge diameter is the increased mass sensitivity.
In situations where only a very small sample volume
is available, it is often possible to obtain a five fold increase in sensitivity by changing from a traditional 4.6mm cartridge to a 2.1mm i.d.. A twenty fold increase in sensitivity can be achieved by switching from a 4.6mm to a 1.0mm i.d. column.