O-ring position doesn't matter
Christine and I have been looking into whether the O-ring position affects transport through pnc-Si transwells. The hypothesis was that the unstirred water layer under the Sepcon might be diminished by switching the O-ring from its normal position (“O-ring bottom”) at the bottom of the Sepcon to above pnc-Si (“O-ring top” or “pnc-Si bottom”). This turns out to NOT be the case.
I collected Christine’s posts below. She did these experiments at a very low rpm (~30).
Here is data from an earlier post of mine. This was done with SC065 at 100 rpm:
And here is new data from SC062 at 300 rpm:
All of these graphs show that the transport of Na-F through pnc-Si doesn’t depend on the O-ring position. In fact, the normal position (O-ring down) seemed to be slightly higher than that of the “pnc-Si down” samples in these experiments. Although we only tested O-ring position once or twice at each rpm speed (~30, 100 and 300), the trend was identical across rpm values. Therefore, I think it’s safe to conclude that O-ring position doesn’t matter in pnc-Si transwell transport experiments.