RE: Activated Charcoal

From:"Monson, Frederick C."

Dear Charles,
	Just for reference, when I prepare 20% formaldehyde from
paraformaldehyde, I always filter, by suction, on a Buetner funnel using #2
Whatman paper after the heated solution has cooled.  This is because there
is always some suspended material in the solution.  The solution is always
clear after filtering.  Aged paraformaldehyde usually leaves more suspended
debris - I don't know why, but flakes are depolymerized with greater
difficulty than the powder.
	I do not use activated charcoal to remove impurities, but my guess
is that the charcoal removed suspended particles of undepolymerized
paraformaldehyde or other material from your prep.  I would have used
regular #2 Whatman in a small funnel [IN the hood].
	None of us really characterizes the formaldehyde concentration after
depolymerization, so the final concentration of HCHO is always less than the
percent of paraformaldehyde used in the prep.  I NEVER perfuse without
filtering first, but I always use simple paper filters. 


Fred Monson

Frederick C. Monson, PhD   
Center for Advanced Scientific Imaging
Schmucker II Science Center
West Chester University
South Church Street and Rosedale
West Chester, Pennsylvania, USA, 19383
Phone:  610-738-0437
FAX:  610-738-0437
Visitors URL:

> ----------
> From: 	Charles W. Scouten, Ph.D.
> Sent: 	Friday, April 26, 2002 3:16 PM
> To:
> Subject: 	Activated Charcaol
> Several years ago, I was using a perfusion with sucrose (instead of
> saline) first, as described by Brain Cragg, 1980, followed by standard
> paraformaldehyde (cooked into formaldehyde, don't yell)/glutaraldehype
> fixative.  I had a bottle of Bakers paraformaldehyde of indeterminant,
> but probably ancient, age.  Everything worked.  I ran out, and switched
> to a new bottle of Fishers paraformaldehyde.  Half the fixative ran
> through, then the flow stopped.  Why the change?  I made the untrained
> amateurs guess that an impurity in the new paraformaldehyde was causing
> the problem, that activated charcoal removed impurities, and ran the
> fixative through activated charcoal after preparing it and just before
> use.  This let it all flow through, and got satisfactory results.
> Question:  What was going on?  Did the charcoal remove impurities, or
> only reduce the concentration?  Does paraformaldehyde deteriorate with
> age?  Why did the flow stop?
> I have a current need to know.
> Cordially,
> Charles W.  Scouten, Ph.D.
> 5918 Evergreen Blvd.
> St. Louis, MO 63134
> Ph: 314 522 0300  
> FAX  314 522 0277

<< Previous Message | Next Message >>