How to use silica gel for column chromatography correctly?

Column chromatography silica gel has a wide range of uses and is needed in many industries. Although its advantages are relatively clear, it must be used in the correct way.

When you use column chromatography silica gel, you must master its correct method. If you are not clear, it is not recommended to use it. Generally speaking, you should weigh it before using it. For 200-300 mesh silica gel, weigh 30-70 times the amount of sample. If you don't want good powder, you can also use 100 times the amount of silica gel H. And the apparent density of dry silica gel is about 0.4, so if you want to weigh 40g of silica gel, you can also use a beaker to measure 100ml. Of course, this amount must be accurate. Then what you have to do is to stir it into a homogenous slurry. When adding a solvent that is twice the volume of dry silica gel, stir it thoroughly with a glass rod. If the eluent inside is petroleum ether, you should use petroleum ether to mix it. If it is an alcohol system, use mixing. If the silica gel for column chromatography cannot be stirred into a homogenate, it means that the water content in the solvent is too high. If you find that its water compatibility is for distribution chromatography, it is necessary to use anhydrous sodium sulfate to dry it for a long time. If you find that the sample is sensitive to acid, then you cannot use the system to pass the column at this time. These two steps are very critical, and everyone must master them in advance.

When using silica gel for column chromatography, after you have completed these two tasks, the next thing you need to do is to install the column. During this process, you must first plug the bottom of the column with cotton, without sea sand, about 1/3 volume of petroleum ether, and then install the liquid storage ball, open the piston under the column, and pour the homogenate into the liquid storage ball at once. When it slowly settles, some silica gel will be stuck in the liquid storage ball, and it will be flushed into the column with petroleum ether. After it is completely settled, add more petroleum ether. Next is to load the sample. After loading the sample, add some eluent, and then plug a ball of absorbent cotton close to the surface of the silica gel, and then you can safely add a large amount of eluent. Finally, you need to test it. Use more special spray developer. If only UV lamp is used, more product will be lost. The collected product is spin-dried and usually needs to be recrystallized before sending for spectrum.