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Message | User | Date(yyyy-mm-dd) |
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filtration over a Dynagard 0.2 micron syringe tip filter | isabelle | 2000-08-23 | Click here to register. |
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I used this filter to filter monoS fractions (in 50 mM MES)of an extract of a transgenic plant, after adding TFA to a final concentration of 0.1% (which causes a pH drop to about pH 2). I'm looking at a basic peptide in an HPLC run (on a C8 column, eluting with increasing concentrations of acetonitrile) and I observe a shift of this peptide in the gradient of acetonitrile (the peptide elutes now with a lower concetration of acetonitrile). Then I filtered a pure sample of that basic peptide (also after adding TFA to a final concentration of 0.1%) and eluted that on the same C8 column. I see that this pure peptide also undergoes that shift. When I don't filter the pure peptide and elute that on a C8 column, I don't observe this shift.
Is it possible that the filter can not be used with a very low pH? | | |
| lil stevie | 2000-08-24 | Click here to register. |
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 | Polypropylene membranes are probably pretty stable under the conditions you have listed.
One thing you didn't mention is if you washed the filter prior to use. As-molded polypropylene parts generally have a bunch of "gunk" (mold release agents and plasticizers) on their surface. If you run your sample through the filter without first washing the filter, you may rinse some of this gunk into your sample. |
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