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Science Forum Index » Chemistry Forum » agar gel replacement
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| Mark |
 Posted: Fri Dec 26, 2003 11:15 am |
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For a demonstration of a medical device, a rotating device is placed
in a clear tube with a red gel and water. The rotating device breaks
up the red gel which then slowly dissolves into the fluid. For the
gel, I selected agar because the tubes need to stored at temperatures
ranging from freezing to 130 F. The problem is that the Agar shrinks
after just a few days. We need to store the tubes at least 6 months.
Does anyone have suggestions for a substitute for the agar gel?
Thanks,
Mark |
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| Muhammar |
| Posted: Fri Dec 26, 2003 6:17 pm |
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I do not know the reason for the agar shrinking. If the shrinking is
caused by dessication, you would need to either seal the tube to
prevent evaporation or to add hygroscopic substance like glycerol or
potassium acetate to keep the moisture in.
If the shrinking is caused by microbial degradation of agar, you can
add some antimicroial preservative used in cosmetic industry or
experiment with a different water-based gel. Since the gel substance
should be cheap nontoxic and non-perishable, I would suggest some
modified cellulose-based gel, for example carboxymethylated cellulose
sodium salt.
corexdg@aol.com (Mark) wrote in message news:<94da384d.0312260815.6886cac6@posting.google.com>...
Quote: For a demonstration of a medical device, a rotating device is placed
in a clear tube with a red gel and water. The rotating device breaks
up the red gel which then slowly dissolves into the fluid. For the
gel, I selected agar because the tubes need to stored at temperatures
ranging from freezing to 130 F. The problem is that the Agar shrinks
after just a few days. We need to store the tubes at least 6 months.
Does anyone have suggestions for a substitute for the agar gel?
Thanks,
Mark |
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| CorexDG |
| Posted: Fri Dec 26, 2003 7:05 pm |
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Guest
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Thanks for the reply. Yes the tubes are sealed. The agar fills the bottom 1/3
of the tube with water filling almost the remainder. I left enough air in the
tube to allow for expansion when froozen. Your suggestions of adding a
hygroscopic substance or antimicroil preservative is interesting. I will look
into this. I am thinking of replacing the water with polypropelene glycol.
This should prevent expansion during freezing and is non-toxic. I am not
familiar with carboxymethylated cellulose sodium salt based gel. Do you know
where the formulation and components can be located?
Thanks |
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