[Histonet] Re: Filtering stains

[gayle callis]

Filtering stains was a long standing habit in our lab.  It didn't matter if
the solutions were coming from a stock bottle or reused and filtered into a
clean container.     

 

However, the kind of filter paper is  important and something I learned
early on from Lillie and Fullmer's book, Histopathological Technic and
Practical Histochemistry.   It was recommended to NOT use a high retention
paper (slow filtration) and use a medium fast paper.   If the porous filter
paper is  too slow, dye molecules are retained on the paper plus it takes
forever to filter a solution when tends to be thicker or flocculent.
Nuclear Fast Red is one that takes forever to filter - very annoying when
there was a time crunch.  Plan ahead!   

If you use a fast paper e.g. more porous, then fine particles can go through
the pores,  creating some contamination on the section.   Some stains were
not filtered e.g. working silver solution for GMS.     

 

As for hematoxylin solutions, regardless of a new stock solution or reusing
the stain the next day, we always filtered to get rid of any oxidation
product and/or tissue particles.    If I didn't filter hematoxylin solution
before IHC counterstaining, there was always an ugly precipitate on the
sections.  

 

Some stains in alcohol, e.g. Luxol fast blue and eosin were not filtered
although reused solutions do contain tissue particles, and then were
filtered.     

 

Rule in our lab:   Filter stains through medium fast paper, daily for H&E,
but top off to keep replenished and at correct level for staining racks.   I
know that some vendors say not to filter the hematoxylin before routine use,
but I could never get out of the filtering habit.   

 

An addition bead of wisdom for people.    Filtering is a messy procedure but
using the correct funnel is important to prevent splashing.   Years ago and
in a chemistry class, I learned to use a tapered end funnel for
filtering/introducing a fluid into a container.  Make sure the tapered end
touches the side of the container.   Use wide, open ended (non-tapered)
funnels are for introducing dry chemicals to a container as wide ends will
cause splashing. 

 

Gayle Callis

HTL/HT/MT(ASCP)