[NHCOLL-L:875] re: rehydrating specimens

[John E. Simmons]

Dear Dr. Zich Reiss,
2-phenoxyethanol is another name for Phenoxetol BPC, which had a brief spurt of
popularity as a replacement preservative for formaldehyde and alcohol in Great
Britain back in the late 1970s and 1980s.  It was used as 1-2% solution in most
applications.  It proved not to be very effective as a biocide, particularly
against bacteria and fungus.  It is more acidic than alcohol, and has no
fixative properties, which is to say, it does not arrest autolysis.  I have
discussed this chemical briefly in:
Simmons, J.E.  1995.  Storage in fluid preservatives.  Pp 161-186 in Rose,
Hawks and Genoways (editors).  Storage of Natural History Collections: A
Preventive Conservation Approach.  SPNHC, 448 pp.

You might also wish to check:
Crimmen, O.A.  1989.  Phenoxetol: an unsatisfactory preservative for fishes.
Biology Curator Group Newsletter 5:26-27.

Many fixatives and preservatives which work fine in histological preparation or
for short-term (less than 10 years) storage of specimens do not work for true
fixation and long-term storage of specimens.  For example, in histology it is
rare to use more than about a cubic centimeter of tissue.  Many fixatives which
have rapid penetration of this small amount of tissue will not penetrate the
whole body of a small animal rapidly enough to be effective fixatives.  Most
histological techniques are designed to yield very short-term results (the
specimen is kept around a few years at best).  There are no good studies of the
long-term effects or efficiency of most fixatives and preservatives.

Similarly with preservatives, in the rush to get away from formaldehyde (which
is truly dangerous) and alcohol (which is expensive), quite a variety of
"preservatives" have been promoted, usually phenols or solutions of ethylene
glycol.  Some of these are safer for use with cadavers for dissection, some
aren't.  None, not one, is as good as 70% ethyl alcohol.  The phenols are
particularly insideous--due to the way phenols are regulated, they are declared
"safe" for laboratory use, but they are not.  The cadavers used in the human
anatomy labs here, for example, are preserved in a phenol based solution.
Although technically safer than formaldehyde based solutions, many of the
teaching assistants have had serious skin and respiratory problems from working
in the lab with them.

My basic recommendations are these:  (1) if you are concerned about DNA
preservation, do not formalin fix your specimens.  Put them directly into 70%
ethyl alcohol (non-denatured, mixed with distilled or de-ionized water).  The
specimens will have to be cut open to allow the penetration of the alcohol.
Larger specimens (mouse or frog size on up) will do far better if you perfuse
the alcohol through the circulatory system.  (2) If you are not concerned about
DNA preservation, fix in 10% buffered formalin (buffered with a dibasic and
monobasic salt, as described in Simmons 1995).  After a few days, rinse the
specimen in water and stage it up through 30% to 50% to 70% ethyl alcohol for
permanent storage.  (3) Avoid using any of the proprietary solutions (e.g.,
Nascoguard, Carosafe) or other solutions (phenols, glycols, and so forth) until
they are thoroughly tested.  Remember that we have 300+ years experience with
ethyl alcohol, but practically none of the other preservatives have ever been
tested.

--John

John E. Simmons
Natural History Museum
University of Kansas

Karen Zich Reiss wrote:

> Has anyone out there had any experience with 2-phenoxyethanol?
>
> I have no idea what it would do to a completely dessicated fish but for
> moderately dessicated formalin preserved specimens it's fantastic.
>
> I keep all my dissection specimens in it and it's in use in some med
> schools for cadavers. It is a preservative, a "moisturizer", relatively
> non-toxic, and it gradually displaces the formalin to yield more pliable
> and pleasant smelling specimens.  I have fluids that have been in
> phenoxyethanol for 5 years and have noticed no deterioration, molding, etc.
> You cannot transfer alcoholic specimens into phenoxyethanol or ugly things
> happen but there's no problem with formalin.
>
> I'd be interested to know of anyone else's experiences with this stuff.  I
> found out about it through the following reference:
>
> Wineski and English (1989) Phenoxyethanol as a non-toxic preservative in
> the dissection laboratory.  Acta Anatomica 136: 155-158.
>
> Dr. Karen Zich Reiss
> Department of Biological Sciences
> Humboldt State University
> Arcata, CA  95521
> tel. 707-826-4156
> fax 707-826-3201
>
>       -- Nature will castigate those that don't masticate. --