any success with PdCl2 and H2 to reduce media?

Nicholas Landau nlandau at eden.rutgers.edu
Sat Jan 2 21:07:35 EST 1999

Peter Stroot <p-stroot at ux1.cso.uiuc.edu> writes:

>i'm looking for assistance with using PdCl2 and H2 to reduce
>media to very low Redox levels....
>(i want to use viologens for redox indicators...-300mV to

All anaerobic chambers use the Pd catalyzed 2H2 + O2 ---> 2H2O
reaction to scavenge O2 from the gas in the chamber.  I have not
heard of it ever used *in* media, for the simple reason that all
media are aqueous (or moist solids) and water drives the reaction
in the wrong direction!

Whenever this reaction is used in anaerobic chambers, dessicant is
used alongside the palladium catalyst to insure that humidity in
the chamber does not inhibit the reaction.  The Pd needs to be dried
periodically in a hot oven to eliminate the accumulated H2O.

I can tell you from experience that the chambers which I have used
which employ the Pd-reaction are not reliably at -300 mV or below.
I used to grow methanogens, using resazurin as an indicator in the
media.  Opening a culture in the anaerobic chamber would lead to the
slow evolution of the indicator's pink color.

What is wrong with traditional Hungate technique?  Why is Pd more
suitable for your purposes that the use of a gassing manifold and
one of the many chemical reductants out there?  I think that you can
use one of the sulfur II compounds (like sulfide, cysteine, or
mercapthoethane sulfonic acid) or titanium citrate to get to the
redox potential you need.

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