[Histonet] RE: Congo red stain

[Grover, Valantou]

Dear Dorothy,
 In commercial preparations of Congo Red are pretty consistent but not pure, a yellow monoazo dye may be present as this impurity.  Although this may not affect staining solutions of Congo Red stain are not stable in salt or alkali solutions, so these do need to be prepared fresh.  You could always choose to under differentiate and use polarized light to distinguish non specific background by using polarized light.  Try to view this birefringence in sections greater than that of 5 microns, usually Congo Red sections are cut thicker at 10 microns or above, depending on the protocol.  Alcoholic fixatives, Bouin's, etc.  Other have chosen to use Sirius Red in the protocol also known as Direct Red 80.  You can always contact me offline if you would like.
vgrover <@t> general-data.com

Best regards,
Valantou

-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Webb, Dorothy L
Sent: Friday, January 03, 2014 10:00 AM
To: 'histonet <@t> lists.utsouthwestern.edu'
Subject: [Histonet] Congo red stain

We have been experiencing major difficulty with our Congo Red stain.  We used to do it on the Artisan, but they changed raw products which has altered the stain and is not acceptable by our hematopathologists.  Now we are back to manual and cannot seem to get it consistently acceptable.

I would appreciate any ideas from the experts out there and if you want to send me offline your procedure, would be appreciated.  Also, does anyone use a negative control , such as a keloid, on the slide?

Thanks, as always, for your help!

Dorothy Webb, HT (ASCP)
Regions Histology Technical Specialist
651-254-2962



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