[NHCOLL-L:3028] Denatured Ethanol vs. Isopropyl for Insects

[Matthew Sarver]

Hello all - 
   
  I apologize to those of you who may have already read my request for information on this topic on ENTOMO-L.
   
  I am still searching for information on types of alcohol for preservation of insect bulk samples for a biodiversity inventory study.  Our program does not have easy access to pure ethanol, and I am trying to evaluate the alternatives.
   
  We have been using a denatured ethanol formulation (Carolina Biological) containing 95% ethanol, 4% methylisobutyl ketone, and 1 % heptane.  I am diluting this to 70% ethanol by volume.  This solution is used in wet malaise collecting heads, for storage of bulk samples, and for storage of insects after they are sorted out from bulk samples.  We are storing all taxa in alcohol and mounting only the ones we wish to work with (right now just Carabid beetles).  We will not be needing to do any DNA work with these specimens.  
   
  I am considering switching over to isopropyl for the collections from the current field season.
   
  Here are the questions I am facing:
   
  1. Does denatured ethanol have a detrimental effect on insect specimens vs. pure ethanol?
   
  2. Does the storage of specimens in denatured ethanol or in isopropyl present a problem if we wish to transfer fluid-preserved specimens to a museum or university collection (most of which use undenatured ethanol)?
   
  3. Is 70% isopropyl a better alternative than denatured ethanol for general long-term storage purposes?
   
  4. Would switching specimens already in denatured ethanol over to isopropyl damage those specimens?
   
  And, on a related note:
   
  5. Is water washing to fractionate alcohol-preserved bulk samples into workable subsamples an acceptable practice?  The specimens would then be put back into alcohol after being fractionated and picked over.
   
  Any thoughts would be very much appreciated.  Again - my apologies for cross-posting.
   
  Thanks
  Matt
   
  Matthew Sarver
  Wildlife & Heritage Service
  Maryland DNR
   

		
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