Micron Spherical Silica Gel Powder for Cosmetics Additive and Column Chromatography
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Column packing techniques for column chromatography

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Column packing for column chromatography is very important, and the effect of column packing will directly affect the chromatographic separation effect. When packing a column (adding silica gel), there are two methods: wet column packing and dry column packing, both of which have their own advantages and disadvantages.


Regardless of the dry method or the wet method, the upper surface of the silica gel (stationary phase) must be flat, and the height of the silica gel (stationary phase) is generally about 15cm. If it is too short, the separation effect may not be good. If it is too long, the separation effect will be poor due to diffusion or tailing.


Wet column packing is to mix the silica gel with an appropriate solvent first, then fill it into the column, and then pressurize and use eluent to "walk the column". The biggest advantage of this method is that the column is generally packed relatively firmly without bubbles.


For dry column packing, silica gel is directly filled into the column, and then the sides of the column are gently tapped until the silica gel interface no longer drops, and then the silica gel is filled to the appropriate height. Finally, use the oil pump to pump directly, so that the column will be installed very firmly. The next step is to "walk the column" with an eluent. Generally, the eluent is a solvent that is diluted twice as much as the ratio of the developing agent obtained by TLC analysis. Usually the top is pressurized and the bottom is pumped with an oil pump, which can speed up the process. Dry column packing is more convenient, but the biggest drawback is that when "walking the column", due to the adsorption heat between the solvent and the silica gel (which can be clearly felt by touching the column with your hand), bubbles are easily generated. This is more obvious when using low-boiling eluents such as diethyl ether and methylene chloride. Although the bubbles generated are not easily noticeable under pressure, they will be released once the pressure is removed, such as when loading samples, adding solvents, etc. In severe cases, the entire column becomes wrinkled and the sample cannot pass smoothly, and of course separation is out of the question. The solution is: first, the silica gel must be filled firmly; second, more solvent must be used to "walk the column" until the lower end of the column is no longer hot, and the pressure must be removed after returning to room temperature.