Stoltz Lab

[moderator]

For transfer of liquids away from solids without exposure to air.

To make a cannula filter:

Method 1: Uses a metal cannula, filter paper, and coppper wire. Place the tip of the cannula at the edge of a 10 cm diam. filter paper. Tightly roll up the cannula in the filter paper so that the tip of the cannula is half way down the roll when you are finished. Fold the emtpy part of the roll up to meet the other end such that the cannula tip is at the fold. Tightly secure the folded roll around the cannula with copper wire. If it is not secured tightly enough, the filtration will not work well.

Method 2: Uses 1.5 mm diam. PTFE intramedic tubing, filter paper and teflon tape. Cut a narrow, triangular piece of filter paper. The base should be approx. 1.5 -2cm and the length approx 5 cm. The tip of the tubing should be square, not angled. Place the tip about 1.5 cm from the base and in the center of the filter paper. Fold over the narrow end of the paper using two creases so that the tip of the tubing has a flat paper surface. Fold up the edges of the rest of the paper while maintaining the flat surface. Tightly secure with two pieces of teflon tape, all the way to the tip leaving the flat surface exposed. The other end can be cut at an angle to puncture septa (make a large hole in the septum first with a small spatula).
Try also different shapes of filter paper. All should be relativley narrow so that it can be folded up the sides of the tubing easily.