Tricky test 2 mix the chemicals
Carefully add solvent to your column so that the solvent level is about 2–3 cm above the top of the silica.If it is still an oil, add more silica and repeat the procedure. Gently evaporate the solvent by using a rotary evaporator until the silica is dry and free-flowing.Swirl or stir gently to ensure all of the silica is suspended within the solution.Add dry silica to the dissolved sample (approx.Transfer it to a round-bottomed flask if it is not already in one. Dissolve the sample in an appropriate solvent.To dry-load your compound, you will need:Ī solvent in which the sample dissolves completely If your compound has poor solubility in the solvent system that gives the best separation, it is possible to dry-load the sample onto the column. You are now ready to start running your column. Finally, add as much solvent as required.This will ensure that your sample is absorbed onto the silica. Repeat steps 5 and 6 once or twice more.Allow this solvent to drain until the solvent level is approximately 1–2 mm above the top of the sand.Use a pipette to carefully add more solvent so that the solvent level is about 10 mm above the top of the sand.This will help prevent the surface of the silica from being disturbed as more solvent is added. Carefully add a layer of sand (approx.Once the entire sample has been added, allow the column to drain so that the solvent level touches the top of the silica.Ideally, the sample should be equally distributed across the surface so that it forms a thin horizontal band. Using a pipette or syringe with a thick needle, drip the sample directly onto the top of the silica.If you need to use a solvent like dichloromethane or something stronger, the dry-loading method described below may be preferable. A slightly more polar solvent than the one you will be using for the column can be used if this helps with dissolution of the sample. Dissolve the sample in the minimum amount of solvent (5–10 drops).Loading the column involves placing the sample directly onto the top of the column and allowing it to absorb onto the silica. Once you have set this up, you will be ready to load and run your column.
#Tricky test 2 mix the chemicals how to
We have previously looked at how to pack a column and how to choose the necessary equipment and solvents.
#Tricky test 2 mix the chemicals full
Here we provide some tips and tricks for running a column, troubleshooting for some problems commonly encountered during column chromatography, and some "quick and dirty" alternatives to a full column. But like many aspects of practical chemistry, the quick and efficient setting up and running of a column is something that can take years to master. Done right it can simply and quickly isolate desired compounds from a mixture. Column chromatography is a commonly used purification technique in labs across the world.