Filter Dissolution: Using forceps and a spatula, remove the filter from the cassette, fold the filter
three times, and place in the bottom of a 40- or 50-mL centrifuge tube. Add 10 mL THF and allow
to stand for at least 5 m in. Cap the centrifuge tube with aluminum foil to prevent contamination.
Gently agitate the centrifuge tube by hand or with a vortex mixer making sure the THF does not go
near the top of the tube. Place the tube in an ultrasonic bath (water level 2.5 cm from top) for at
least 10 m in. (The filter should be totally dissolved.) Just prior to filtering, agitate the sample for
10 to 20 sec on a vortex mixer. Continue with step 6, substituting THF for 2-propanol and
centrifuge tube for beaker.