Basically, there are three methods of sample loading in flash column: sample cleaning method, solvent method, and silica gel adsorption method.
If the sample is a non-sticky oily substance, it is easy to use the sample cleaning method. We can use a long dropper filter to inject the liquid into the flash column, and then elute the sample into the column with the pre-designed solvent system.
In general, a sample cleaning method sometimes may cause a fault in the flash column. So as for liquid and solid, the more common method is the solvent method, which is to dissolve the sample in the solvent and then inject the solvent into the flash column.
The third method is the silica gel method. This technique is to adsorb the compound in the silica gel. It is effective for a part of the liquid and all solid. However, it should be noted that the silica gel is acidic, so that this process may destroy some compounds which are sensitive to acid. Normally, they need to be regenerated in the silica gel column.
Furthermore, silica gel is an extremely fine powder, so it can be easily sucked in the rotary evaporator. In that case, we should use glass wool to bung the contact or the protector of the pump.