[Nhcoll-l] Test for formalin

[Simon Moore]

Dear Mandy,

I fully understand your predicament! Although most organisms (and I’m talking generally) will not suffer when changing from formalin to alcohol, the more gelatinous beasties look much worse, becoming opaque sometimes even embrittled and undergo osmotic pressure stress. Not very helpful but just an awareness. I used to transfer these into glycol-based preservatives which don’t have evaporation and flammability issues and are basically non toxic, however, although effective for some organisms in the longer term, they did cause tissue swelling leading to specimen fragility (rather than embrittlement) over time and are now deemed to be only partly reliable.
What the sector needs is a reliable preservative panacea that doesn’t also have all of these issues, including taxes and there have been many new preservatives that have come and gone because they will not stand up to the test of time or have other issues (cost, specific gravity problems &c.)

However you were asking about spot tests for formalin. I was unaware that Schiff’s reagent was carcinogenic although the formulation has been modified over the years. I still use Feulgen’s reagent, used in enzyme histochemistry and which is basic fuchsin decolourised using charcoal and known as leuco-basic fuchsin (sorry the auto-correct is giving me a hard time!).  There are test strips available from several sources, quite expensive and they have a short shelf life!  My own home-made ones based on filter paper strips dipped in Feulgen, were a pain to make but worked for about 3 months before the papers turned a dull purple even though they were stored in a dark brown glass bottle.

Hoping that some of this may help.

With all good wishes, Simon.

Simon Moore MIScT, RSci, FLS, ACR
Conservator of Natural Sciences and Cutlery Historian, 



www.natural-history-conservation.com 




> On 26 May 2020, at 23:45, Mandy Reid <Mandy.Reid at austmus.gov.au> wrote:
> 
> We are about to embark on a project in our Malacology collection at the Australian Museum to transfer all our formalin stored specimens to ethanol. The formalin specimens are in 5%-10% formalin/seawater solution. Not all specimen lots are stored in formalin, and the preservative is unknown for some, particularly historic material.
>  
> Our routine test is to determine whether the storage solution is miscible with water when a few drops are placed on dish or tray (therefore formalin), whereas an alcohol solution will ‘repel’ a water droplet. This test is not always clear and ideally I would like to use something like test strips, or a stain solution that would give a quick and clear result. I understand that Schiffs reagent works, but that is also a carcinogen.
>  
> I have an excellent paper that gives a method of making test strips: Waller, R. (1987). A spot test to distinguish formalin from alcohol solutions. Curator, the Museums Journal. 240-249.
>  
> I am wondering whether anyone can recommend commercially available test strips that would be suitable? (Or some other method.) The strips that I have investigated online seem to be used mainly to test contaminated water samples and are too sensitive for our needs.
>  
> Thank You!
>  
> Dr Mandy Reid
>  
> Collection Manager, Malacology | Australian Museum Research Institute
> Australian Museum  1 William Street Sydney NSW 2010 Australia
> T 61 2 9320 6412 | M 61 431 829 842 | F 61 2 9320 6253
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