[NHCOLL-L:5592] Re: PREFER as an alternative fixative to Formalin

Fri Aug 12 05:26:30 EDT 2011

Thanks for this information John and Moretta,

I would think that any fixative fluid with a higher-than-average specific  
gravity would be doomed at the outset.  Fish are one of the most vulnerable  
vertebrate groups due to their high muscle content which makes, as John 
says,  tissue penetration rate a vital issue.  
Testing would need to be done by histological analysis of stained tissue  
that has been fixed - I always stick with liver tissue as it's one of the 
most  sensitive.  Also by cutting body steaks of fixed tissue to check  
penetration levels and see whether there has been any tissue  deterioration.  Of 
course, the fixative must be injected into specimens  along the body to 
prevent autolysis.  

This type of testing will need to be continued at 6 monthly intervals to  
check for changes at histological level for up to 2 years.  Proposed  
changing of fixative solutions always brings a large burden of testing work with  
it.  Written up results, even if negative (especially if  negative!) are 
vital to the advancement of fluid preservation  science.  Good luck!

With all good  wishes, Simon

Simon Moore MIScT, FLS, ACR,
Conservator of Natural  Sciences,

_www.natural-history-conservation.com_ 
(http://www.natural-history-conservation.com/)  
_www.pocket-fruit-knives.info_ (http://www.pocket-fruit-knives.info/)  

_http://uk.linkedin.com/in/naturalsciencespecimenconserve_ 
(http://uk.linkedin.com/in/naturalsciencespecimenconserve)   

In a message dated 11/08/2011 18:20:27 GMT Daylight Time,  
simmons.johne at gmail.com writes:

I have  not used PREFER solution myself, but there are several reasons why 
you should  be very cautious about doing so.

The problem with most formaldehyde  alternatives is that the solutions have 
proprietary components, which means  that you don't know what chemicals you 
are using to preserve your  specimens--this is analogous to having an 
uncontrolled variable in an  experiment (in other words, not a good idea).  
According to the MSDS,  Prefer is an aqueous solution of an unknown ratio of 
glyoxal, ethanol, and a  secret buffer.  You don't know if the ehtanol was 
denatured or not  (probably not) but without knowing what the buffer system is, 
you have no way  of knowing how it will behave long-term (is it stable?  Is 
it prone to  oxidation or reduction?).  Because the ratio of the components 
is  unknown, you have to worry that it could be very high in alcohol, which 
would  dehydrate your specimens, or it could be overloaded with buffer and 
cause  post-fixation preservation problems, etc.  According to the MSDS, the 
pH  of PREFER is 3.75 to 4.25, which is okay for fixing a biopsy sample but 
far  too acidic for long-term specimen preservation.  Not knowing what buffer 
 system PREFER uses, you run the risk of further complications if you try 
to  buffer it to close to neutral yourself.

Glyoxal itself (formula OCHCHO)  is an aldehyde similar to formaldehyde, 
used in industry to cross-link  proteins and collagen, so its fixative action 
is likely to be very similar to  that of formaldehyde, but probably has much 
less ability to penetrate  tissues.  One of the great advantages of 
formaldehyde over all other  aldehyde fixatives is how deeply and how quickly it 
penetrates tissues.   However, Prefer solution is marketed specifically for 
fixing biopsy samples,  which are very small tissue blocks.  There are dozens 
of great  histological fixatives that work well on tissue blocks under a 
cubic cm that  are completely unsuitable for larger specimens because of their 
inability to  penetrate deep tissue blocks or to penetrate rapidly enough to 
fix  them.

Another potential serious drawback to glyoxal is its density  (1.27 g/cm3), 
which is much greater than that of formaldehyde (0.8153 g/cm3)  so your 
specimens are probably going to float in it rather than be submerged,  which 
will make thorough fixation of a fish very difficult to do.   According to the 
MSDS, the specific gravity of PREFER is 1.003,which can still  cause 
problems (and it is hard to evaluate this number because the ratio of  the 
components is proprietary).

If you are preserving fish for  classroom use or exhibit use, then the use 
of a proprietary formula could be  justified.  However, if you are 
preserving fish for scientific  collections, I caution against using unknown 
chemicals that might well affect  the long-term stability of the specimens or affect 
the ability to later  chemical analysis of the specimen, DNA extraction, 
etc.

If you do try  PREFER solution, please write up your results and let us all 
know how it  goes.  There is a great need for a better alternative to  
formaldehyde.

Hope this helps,
John

John E.  Simmons
Museologica
128 E. Burnside Street
Bellefonte, Pennsylvania  16823-2010
_simmons.johne at gmail.com_ (mailto:simmons.johne at gmail.com) 
303-681-5708
_www.museologica.com_ (http://www.museologica.com/) 
and
Adjunct Curator of  Collections
Earth and Mineral Science Museum & Art Gallery
Penn  State University
University Park, Pennsylvania
and
Lecturer in  Art
Juniata College
Huntingdon, Pennsylvania

On Thu, Aug 11, 2011 at 10:52 AM, Frederick, Moretta  RBCM:EX 
<_MFrederick at royalbcmuseum.bc.ca_ (mailto:MFrederick at royalbcmuseum.bc.ca) >  wrote:

Does anyone  have experience with a glyoxal-based fixative called PREFER 
made by  Anatech?  It has been suggested to us as an alternative to formalin  
fixation of fish.  I would be interested in hearing from anyone using  this 
fixative with fish, invertebrates, and/or  herps. 
_http://www.anatechltdusa.com/productlit/preferlit.html_ 
(http://www.anatechltdusa.com/productlit/preferlit.html)  
Thanks,   
Moretta 
____________________________________________________________________________
__________________ 
Moretta  Frederick      Collections Manager, Invertebrates,  Fish, 
Amphibians, Reptiles  |  Natural  History      

675 Belleville Street, Victoria,  BC Canada V8W 9W2
T _250  387-2932_ (tel:250%20387-2932)  
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