Kromasil silica is superior when it comes to mechanical and chemical stability, and can therefore, under most circumstances, be reused over and over again.
Kromasil can be stored either as a dry powder, or in a solvent. For storing the silica in a solvent it is recommended that you unpack and store the used silica in the solvent that you later will use in the packing process as a slurry solvent. For recommended slurry solvents please see our packing instructions.
If you intend to use toluene/2-propanol as a slurry solvent during your next packing, you should, before unpacking, switch to pure 2-propanol. You should allow at least 3 column volumes of solvent to flush through the silica. This will clean the silica, as well as being a good solvent for storing.
When unpacking a reversed phase silica, it is important to first rinse the column bed from any buffer. Recommended mobile phases for this are for instance 2-propanol/water, ethanol/water, or methanol/water. After that all water should be flushed out using 100 percent of a water-soluble solvent. We recommend for instance 2-propanol, ethanol, or methanol. Before unpacking you should then switch to a packing solvent in the same way as for bare silica.
To store Kromasil dry, apply the methods above, and use either acetone* or THF as the last solvent. Unpack the column, and dry the packing in an oven at 90°C for derivatized Kromasil, and 120°C for bare silica.
* For Kromasil NH2, only THF is recommended, since acetone will react with the amino phase.