Diffusion on shaker
I ran a few experiments using the stir cell on the shaker table. Diffusion occurs faster on the shaker, but more air bubbles form around the membrane, thus preventing further passage of rhodamine. The first experiment I ran was with .2mM rhodamine diluted from 2mM in a PBS solution. For all of the experiments PBS was used in the lower wells and rhodamine diffused into the PBS solution. I started the speed of the shaker at 120 rpm, but lowered it to 110 rpm for later experiments to see if that would help with the air bubble problems. Lowering the speed did not make a big difference on diffusion rate, nor air bubble formation. Below are the graphs for the various trials I ran this week.
I also had issues with evaporation when I let the stir cell run overnight. When I ran another trial I made sure to cover the box better with parafilm, experiencing less evaporation for subsequent trials.