We often say that column chromatography is actually column chromatography separation, also known as column chromatography. It was first developed by Russian scientists in 1903Invention and use: The solution of plant pigments is crushed into calcium carbonate powder, and different color bands are found on the calcium carbonate powder from top to bottom. By separating and extracting different color bands, relatively pure chlorophyll, lutein, etc. are obtained.

This method has been developed for a hundred years and is now relatively mature, with a fixed phaseIt has also developed from a single calcium carbonate powder to alumina (which can be classified as acidic, neutral, alkaline), silica gel, activated carbon, etc. Among them, silica gel is commonly used in major laboratories, generally divided into normal phase silica gel and reverse phase silica gel!

The stationary phase (silica gel) generally needs to be purified and activated, and the particle size should be uniform. In theory, the smaller the particle size and the larger the surface area per unit mass, the higher the adsorption capacity and the better the separation effect.However, in practical use, when the fixed phase particles are too small, there are often two situations: one is that they are lighter in weight and easily float in the air (silica gel cannot be degraded by the human body, and the finer, the more toxic it is); Secondly, small particles can also lead to small gaps between particles, resulting in a slow solvent flow rate and time consumption; Taking silicone as an example, it currently has the largest commercial usageThe size of silicone is 200-300 mesh.

In addition to the automatic analysis equipment such as forward circulation preparation, efficient liquid phase preparation, and column passing machine mentioned earlier,There are mainly three types of manual column passing: atmospheric pressure column passing, depressurization column passing, and pressurization column passing.

among whichReduce pressure through the column,Because the eluent flow rate is too fast, it will lose most of the number of trays, resulting in poor separation efficiency,Suitable for separating TLC plates from relatively open samples,Especially suitable for samples with only one large polar impurity in the product; Most of its time is spent on the pre-treatment of compounds, removing some impurities before careful purification. It should be noted that solvent evaporation caused by negative pressure during use can lead to the condensation of a large number of water droplets on the outer surface of the column. Water sensitive compounds should not be easily attempted.

Atmospheric pressure column passing is the better separation method among the three, but because the solvent often moves too slowly, even the best separation effect can affect efficiency. Therefore, pressure is usually applied at this time, which is called pressurized column passingBut the pressure should not be too high. Generally, a double chain ball is used for manual operation, and a fish pump is used for automatic operation. Both can be modified.

(Source: Organic Cabbage)