Update on Track-Etched Membranes
I ran some tests today using the 0.01um, 0.05um, and 0.10um pore diameter track-etched membranes from sterilitech. The tool the paul built to cut the membranes works very well, and assembly into the microcon systems it simple. I used the standard vertical-wall o-rings that come in the microcon systems because based on yesterdays test results they seemed to withstand leaks.
The numbers at the top of each section of bar plots is the diameter of the pores for the given membrane. Based on the pore density values (given at the sterilitech website) I calculated the porosity values of membranes (from left to right) to be 471E-6%, 11.77E-3%, and 31.40E-3% respectively. So, from left to right the membranes get more porous.
I do not think this data gives us any good results other then showing that about 50% of the devices leak once we cut the membrane and place it in the microcon system. After a 4min spin at 1000RPM the membranes with spiked permeability (both right bars in set one, the first bar in set two, and the middle bar in set three) we at near equilibrium, so there was definitely a leak present. As for the other points I am not sure how confident we can be that they did not have leaks either.
Maybe you could bring one of your retrofitted devices to the next meeting, so we can look at it? The TE membranes are much thinner than the original millipore UF membranes in the spin tube. Do you use some type of shim to make up the difference? If not, substantial leaking is possible. Maybe we can buy some type of microfiltration membrane that you could cut to fit under it – it’s a difficult problem.