dialyze for 20-22 hours. Cover the solution with aluminum foil.
remember to use the silk within 3 days after this concentration dialysis!
Observations
Our solution that we put into the tubing is 5.2% w/v.
the PEG solution is too dense. The dialysis tubing is essentially floating on top, buoyed by the dialysis clips.
I think this might slow down the diffusion of water out of the tubing. Maybe more dialysis time will be needed?
PEG dialysis start: 4:25 pm
should end the dialysis at like 2:00 pm tomorrow.
PEG dialysis start: 2:00 pm, May 21
the concentration dialysis does not look promising
most of the solution was unsalvageable -- it gelled up inside the dialysis tubing
solution is too difficult to retrieve from the dialysis tubing
ended up squeezing out about 100 uL of solution from it
pipetted 10 uL onto a weigh boat to determine concentration (uncertain if our milligram-sensitivity scales will be able to determine an accurate dry weight)
Dry weight is 2 mg. That is 20% w/v, very close to what we had expected.
solution looks extremely cloudy
after about 2 hours, the 100 uL that we had was completely gelled up. I think I exerted too much shear force when removing it from the dialysis tubing.
Lesson learned: the concentration dialysis must run for less than 22 hours
Also, use the dialysis cassettes instead of the dialysis tubing
What might have gone wrong
the dialysis tubing was horizontal, rather than vertical in the PEG solution. As such, there was an air bubble at the roof of the tubing. Could this air surface contact caused the silk to gel up?