dialysis membranes

Dr. Peter Gegenheimer PGegen at UKans.nolospamare.edu
Wed Aug 11 18:21:24 EST 1999


On Mon, 9 Aug 1999 15:30:12, D.Schnapp at qmw.ac.uk ("D.Schnapp") wrote:

ð
ð Hi folks,
ð
ð I just received some cellulose membrane dialysis tubing and it came with
ð instructions of lengthy preparation, including wash under running water
ð for several hours to remove glycerin (which would not interfere with my
ð stuff), treatment with sodium sulfide (which we don't have) and
ð acidification with sulphuric acid. Is all this really necessary? I
ð remember just boiling up the membranes in some water plus - I think- EDTA
ð (not sure whether it was EDTA or why it was added). Anybody using other
ð ways of preparing cellulose membranes? Sigma technical services do not
ð have any alternative advise.
ð
ð Cheers,
ð
ð Denni
ð
ð ****************************************************************************
ð Denni Schnapp
ð Dept. of Paediatric Gastroenterology
ð St. Bartholomew Hospital
ð Dominion House						Phone:(0)171/6018469
ð 59 Bartholomew Close					Fax:  (0)171/6005901
ð London EC1A 7BE			 http://www.st-and.ac.uk/www_sa/personal/~ds4
ð ****************************************************************************
---
Treatment of standard dialysis tubing is required to remove the heavy metals
and sulfides present from the manufacturing process. Also, dry tubing usually
contains glycerol as a preservative.

The "preferred" treatment -- one I've seen referenced frequently and which
does not damage the membrane -- is as follows

Make a sulution of ca. 10 mM Na2EDTA (heavy-metal scavenger) and 10%
Na-carbonate or -bicarbonate (buffer). Heat the solution to 70 degrees C -- no
higher -- and immerse the tubing for ca. 10 min. Pour off the solution and
rinse the tubing with distilled water. Repeat these steps; then heat the
tubing twice in distilled water. The tubing is stored at 4 C in the final
solution. (Presumably because any cellulase enzymes, secreted by fungi in your
"pure" water, will have been inactivated by heating.)

Many years ago I read information from a dialysis tubing
manufacturer--Spectrum, I think--saying that higher heating can damage the
pore structure of the membrane. In addition, at 70 degrees you do not get the
formation of air bubbles _inside_ the tubing, which causes the tubing to float
out of the water. (If dry tubing touches the hot dry glass of the beaker it's
heated in, the tubing can develop leaks.) Spectrum currently lists the
temperature limit for its regenerated dialysis tubing as 60 C (see
http://www.nbsbio.co.uk/spectrm5.htm).

Variation: The Cold Spring Harbor cloning manual's procedure uses one heating
with 1 mM EDTA and 2% Na-bicarbonate; a distilled water wash; one heating with
1 mM EDTA.


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| Dr. Peter Gegenheimer       | Vox: 785-864-3939  FAX: 785-864-5321   |
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