paterekjr at aol.com
Wed Feb 21 10:13:22 EST 1996
You could add a reducing agent, such as sodium sulfide or cysteine
hydrocloride, along with the oxidation/reduction indicator, resazurin.
Resazurin is blue in solution until you boil the solution to drive out the
dissolved gases. As you sparge the cooling solution with nitrogen, the
resazurin turns pink at Eh near zero, as the oxidation-reduction
potential drops (after addition of sodium sulfide or cysteine) the
indicator is colorless. If your medium turns pink, you know that oxygen
or another oxidation agent has entered the medium.
You can sample by have a nitrogen gas flow at a high enough rate that when
you open the flask the headspace stays positive. This keeps the
I assume you are growing the cyano in the dark as heterotrophs, so they
will not produce oxygen. If so, the above should work. I would be
interested in more info on your research. Please contact me with any
other questions or comments.
J. Robert Paterek, Ph.D.
Manager, Environmental Biotechnology
1700 South Mount Prospect Road
Des Plaines, IL 60018
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