dialysis membranes

Achim Recktenwald achimr at home.com
Mon Aug 9 21:53:38 EST 1999

Cornelius Krasel <krasel at wpxx02.toxi.uni-wuerzburg.de> wrote in message
news:m64no7.d58.ln at wpxx02.toxi.uni-wuerzburg.de...
> "D.Schnapp" <D.Schnapp at qmw.ac.uk> wrote:
> > I just received some cellulose membrane dialysis tubing and it came with
> > instructions of lengthy preparation, including wash under running water
> > for several hours to remove glycerin (which would not interfere with my
> > stuff), treatment with sodium sulfide (which we don't have) and
> > acidification with sulphuric acid. Is all this really necessary? I
> > remember just boiling up the membranes in some water plus - I think-
> > (not sure whether it was EDTA or why it was added).
> I was taught to boil dialysis membranes once in 500 mM EDTA and 7-8
> times in water afterwards. The EDTA is supposed to remove trace
> contaminations of heavy metal atoms which apparently occurred quite
> frequently in cellulose membranes (not sure whether this is still
> true). So far, I have not encountered any problems with dialysis
> membranes prepared this way.

Add some sodium bi-carbonate to neutralize the acidic EDTA and raise the pH
to ~7.8.

The instructions that came with your dialysis membranes and the one by
Cornelius have the same purpose. The membranes are produced using salts of
heavy metals. These metals react especially strong with cysteines. I order
to get rid of them you can use boiling in slightly alkaline EDTA, or the
more rigorous method that came with your membranes. EDTA will only be
successful with divalent metal ions, the first method with a strong
reductant and subsequent acid wash will remove all of them.


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