Column

The column is the part of the HPLC in which the separation occurs. HPLC columns are mainly constructed from smooth-bore stainless-steel tubing due to the high-pressure aspects of HPLC. Nowadays columns are sometimes constructed from heavy-walled glass, titanium, or plastic (e.g. PEEK®) to offer the analyst better performance for particular analytes. Common dimensions for analytical-scale

Vent

Counterclockwise load

To column 3

Vent columns are in the range of 10 to 30 cm long and 4 to 10 mm inner diameter. The common particle sizes of packings are 3, 5, and 10 |im. Columns of the these dimensions often have efficiencies of 40 000 to 60 000 plates per metre. The current trend has been the use of higher performance, high-speed columns, which have smaller dimensions than those described. Such columns have efficiencies of 100000 plates per metre and have the advantage of speed and minimal solvent consumption. Hundreds of packed columns in differing size and packing material are available from numerous manufacturers.

It is important to read the manufacturers' literature relating to the maintenance, handling, and limitations of the column (e.g. silica-based columns are only compatible with pH values from 2 to 7). In addition to chemical limitations of the packing material, columns are easily degraded by the irreversible adsorption of impurities from samples and solvents. Hence, a small guard column is often used to protect the integrity of the analytical column, which is much more expensive. Also, for analytes, which may contain particulates, an inline filter can be placed between the injector and guard column. It should be noted that with the addition of each component after the injector, the efficiency of the separation is degraded. Hence, judicious use of inline devices is necessary.

For many applications, close control of column temperature is not necessary and HPLC separations are performed under ambient conditions. However, temperature control can enhance chromatographic reproducibility and afford opportunities to improve separation efficiency. Modern instruments can be equipped with column heaters/ovens that control column temperature to a few tenths of a degree from near ambient to 150°C.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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