A cannula filtration is carried out in a similar way to a cannula transfer. The cannula is modified to place a filter on one end, so that only the liquid is transferred and any solid material remains in the original flask. The filter is constructed as follows:

1. Prepare a cannula of suitable length, with one sharp, bevelled end and the other with a blunt end.

2. Use a small filter paper to fold over the blunt ended cannula opening and tightly wrap the filter paper around the cannula. Secure the filter in place using Teflon tape.

The filtration is carried out in a similar fashion to cannula transfer, ensuring the filter end of the cannula is placed into the donor Schlenk tube. The liquid will be transferred from the starting Schlenk tube to an empty tube leaving behind any solids as a residue.

Where the residue is the product of interest, filtrations are usually followed with solvent washing of the solid residues. These are carried out as follows:

1. The cannula for the filtration should still be in place connecting the residue Schlenk tube to the tube of filtrate. Raise the filter end of the cannula from the bottom of the Schlenk tube towards the top of the flask.

2. Add in the desired solvent for washing the residue and agitate the flask to ensure the residue is washed with the solvent.

3. Lower the filter back into the flask and begin transferring the wash solvent by closing the gas bubbler in the same way as for cannula transfer.

4. Repeat the washing steps as required.

For both cannula filtration and washing, it is likely that significant product is stuck to the filter paper attached to the cannula. It is often prudent to cut the cannula as the septum is removed in order to leave behind the filter paper in the Schlenk tube in order to avoid losing material. A typical procedure to complete a transfer would be:

1. Remove the exit needle from the receiving Schlenk tube.

2. Reopen the sidearm tap on the receiving Schlenk tube so that the flask is open to the gas manifold.

3. Remove the cannula from each septum.

If a cannula filter is fitted, cut the tubing close to the filter end and allow it to drop into the Schlenk tube. You should do this as you are replacing the septum with a stopper (otherwise the cannula will still be gripped by the septum), but only allow it to drop into the Schlenk tube if you have not exposed it to air.

1. Ensuring each flask is open to the gas manifold, replace the septa with stoppers.