One Method For Sampling In The Flash Columns
Generally speaking, there are three options for sampling. Here we talk about the complicated one: silica gel adsorption method.
The principle of the silica gel adsorption progress is to adsorb compounds onto silica gel, which is useful for some liquids and all solids. But we have to notice that silica gel is acidic. In this step, some acid-sensitive compounds will be destroyed, which usually need to be regenerated on silica gel columns.
At first, we should dissolve the mixture with dichloromethane in a round-bottom flask and add silica gel in it. The quality of silica gel is about twice that of the compounds. Then concentrate the solution on a rotary evaporator. Here we need to care that silica gel is a very fine powder and is easily absorbed into the rotary evaporator.
Using glass wool to plug the joint or pump protection device can prevent solids from being sucked into the pump, or fast rotation. When most solids have fallen off the wall of the container, indicating that the solids have dried. And assuming there is no volatile substance in the mixture at this moment, remove the flask from the rotary evaporator and exhaust the solvent with a vacuum pump.
Following all the above, we can add this solid to the top of the flash column with a powder funnel, and then wash it with an eluent.