Tips for passing the column of column chromatography
Column chromatography can be divided into: pressurized, normal pressure, and reduced pressure according to the pressure when passing through the column. Pressure can increase the flow rate of the eluant and reduce the time for product collection, but it will also reduce the number of plates in the column. Therefore, when other conditions are the same, the atmospheric pressure column is the most efficient, but it also takes the longest time. For example, for the separation of some natural compounds, it is sometimes possible for a column to take several months.
The pressure reduction column can reduce the use of silica gel, but because a large amount of air passes through the silica gel, the solvent will evaporate, and sometimes water vapor will condense outside the column. In addition, some things that are easier to decompose may not be available, and a water pump must be used at the same time to pump air, which is noisy and takes a long time, so decompression columns are rarely used.
Pressurizing the column is a better method, similar to the normal pressure column, but using external pressure can make the eluent move faster. The pressure can be provided by compressed air, a double-connected ball or a small air pump (just use a pressure pump that supplies air to the fish tank). It is particularly suitable for separation of easily decomposed samples. Generally, the pressure should not be too high, otherwise the solvent will move too fast and the separation effect will be reduced. Because the pressurized column has high efficiency and good separation effect, the pressurized column is very suitable for the separation of ordinary organic compounds. Some low-boiling point solvents often produce bubbles in the column when they are packed into the column, causing the column to become distorted. This problem can be effectively solved by using the pressure-passing method when packing the column, and the column can be packed quickly.
With the development of science and technology, chromatography technology is also changing rapidly, but column chromatography experimental technology is still relatively simple and practical. When using column chromatography, each scientific researcher can constantly explore according to his or her actual situation, and constantly summarize and improve the experimental technology of column chromatography.