[Histonet] a much easier chemistry question

[John Kiernan]

Your unsuccessful efforts were all acidic, 
neutral or hydrophobic. Trypan and Evans blue are 
anionic dyes with large, very hydrophilic molecules.
Alkaline solutions extract anionic dyes, and urea 
(high concentration) can disrupt the non-ionic, 
non-covalent bonding that holds large hydrophilic
dye molecules to substrates such as cellulose (cotton). 

Try a strong urea solution (8M=48%) made alkaline
with borax or washing soda. Geoff McAuliffe's
simpler suggestion of soap and water may work,
because soap is alkaline. 

Keep us informed. All who use dyes need this sort
of information. (I have a grey tie with alcian 
blue spots dating from the 1960s; wouldn't want to 
remove them now, though I'm sure it would be
impossible without dissolving the fabric.)

John Kiernan
London, Canada
-------------------------------------
Jack England wrote:
> 
> Aloha all,
> 
> Here's a much more fun chemistry question for anyone that wants to bite:
> what is the best method to remove trypan/evans blue from cotton fabric?  One
> of my colleagues got some on her pants the other day and asked what the best
> way to get it out was.  I did not know, so I put some on cotton gauze, and
> tried:
> 
> --acid alcohol...faded the stain a little, but didn't get rid of it
> --DI water...no change
> --absolute ethanol...no change
> --xylene...no change
> --ethanol/non-ionic detergent/DI water rinse...no change
> --citrus oil clearant...no change
> 
> Given that her fabric is tan (and thus not white, and thus likely not
> bleach-able), can anyone out there in histo-land suggest a way of
> de-staining trypan-blue-stained fabric? I've been wondering about this for a
> while now and figured I'd pass it around.
> 
> --Many thanks and aloha to all,
> Jack England
> Tissue Genesis, Inc.
> http://www.tissuegenesis.com
> 
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