In general, the column chromatography process is usually accompanied by lateral diffusion. This diffusion will cause a large decrease in resolution. Therefore, when the column is taken, the column chromatography time should be shortened as much as possible, especially to avoid column overnight. The flash column is to reduce this lateral diffusion with the fastest possible flow rate without sacrificing exchange efficiency (adsorption and desorption).
Advantages of flash column
Fast column chromatography has at least the following advantages:
1. Time is greatly saved, from packing to completion (excluding concentration), generally only 30 minutes (the whole preparative thin layer chromatography takes about 4 hours);
2. The compound has a short residence time on the column and a reduced possibility of chemical change, which is suitable for the separation of unstable compounds;
3. It is suitable for separation of 20-100mg samples
4. It is also suitable for separating large quantities of samples and can load 10-25g at a time. Stainless steel cylinders are even used in the factory and can be loaded 100-200g at a time. For example, if 10g of crude product is separated, a glass column with a diameter of 8.0 cm can be used, and the height of the silica gel is only 16 cm, that is, the filling height: diameter, only 2:1. the rest will contain eluent, the amount of eluent is roughly the same as that of conventional column chromatography.
Fast column chromatography has at least the following advantages:
1. Time is greatly saved, from packing to completion (excluding concentration), generally only 30 minutes (the whole preparative thin layer chromatography takes about 4 hours);
2. The compound has a short residence time on the column and a reduced possibility of chemical change, which is suitable for the separation of unstable compounds;
3. It is suitable for separation of 20-100mg samples
4. It is also suitable for separating large quantities of samples and can load 10-25g at a time. Stainless steel cylinders are even used in the factory and can be loaded 100-200g at a time. For example, if 10g of crude product is separated, a glass column with a diameter of 8.0 cm can be used, and the height of the silica gel is only 16 cm, that is, the filling height: diameter, only 2:1. the rest will contain eluent, the amount of eluent is roughly the same as that of conventional column chromatography.
Components
The fast column consists of a “chunky” pressure-resistant glass column, an air-conditioning valve, a compressed air source, and a set of tubes that can move freely. It is equipped with 4 columns with diameters of 2.5, 4.5, 6.0, 10 cm and heights of 30, 45, 60 and 80 cm respectively, which can meet the requirements of general experiments and can separate 20mg-20g crude products.
The fast column consists of a “chunky” pressure-resistant glass column, an air-conditioning valve, a compressed air source, and a set of tubes that can move freely. It is equipped with 4 columns with diameters of 2.5, 4.5, 6.0, 10 cm and heights of 30, 45, 60 and 80 cm respectively, which can meet the requirements of general experiments and can separate 20mg-20g crude products.
Compressed air can be supplied by a low-pressure air compressor, plus a tank for buffering air pressure and smooth airflow. The pressure can be controlled by a regulating valve. This control valve is fully closed, always allowing some of the air to escape and adjust to ensure the safety of the entire system.
Since the eluent flows down continuously, the automatic fraction collector is no longer suitable, and a tube assembled on the test tube can be pushed by hand to collect the fraction. Usually, it takes a few dozen seconds to collect a test tube.
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