[Nhcoll-l] Test for formalin

Thu May 28 21:42:08 EDT 2020

Thanks Irene
For our purposes, I have no need to quantify anything. We (as will be the case, I expect, for most museum collections) simply need to know whether a specimen is stored in formalin, and therefore needs soaking out of formalin before transfer to ethanol  for long term storage, or whether it is preserved in ethanol, in which case it simply may need topping up and is comparatively safe to handle. Testing ethanol concentrations is a separate issue at this stage and I suspect the purchase of a digital density meter or hydrometer will be a much less expensive option than conducting other tests in terms of large collections, and, therefore, the cost of staff time when handling possibly thousands of specimen lots.

As we have a large collection in Malacology, we need a method that is quick, cheap and effective. The percentage of formalin, which is, of course a dilute stock solution is of no importance in terms of WHS issues because we treat any concentration of liquid containing formalin equally in terms of care and safety, by using appropriate PPE and working under a fume hood.

Cheers
Mandy

From: Irene Finkelde <irenefinkelde at gmail.com>
Sent: Friday, 29 May 2020 11:09 AM
To: Hawks, Catharine <HawksC at si.edu>
Cc: Mandy Reid <Mandy.Reid at austmus.gov.au>; Robert Waller <rw at protectheritage.com>; nhcoll-l at mailman.yale.edu
Subject: Re: Test for formalin

Hi All

The paper test suggested by Dries and the NIWA test with marker, which bleeds in alcohol, are great because they are quick and simple – but they do not give quantitative results of how much formalin/formaldehyde is in the fluid preservative, nor the concentration of the alcohol solution. For your purposes Mandy, this may not be necessary, but I thought I would share some methods for quantitatively determining formalin/formaldehyde concentration in case anyone else on the list-serv is also looking for methods.

For testing alcohol concentration, a digital density meter is really the most effective method. However, this is a very costly piece of equipment and many organisations do not have budget to buy one. A hydrometer can be used if you have sufficient fluid volume. I have refined a method, initially published by Theresa Mayfield, that uses salts (potassium carbonate and sodium chloride) to distinguish between ethanol, isopropanol and aqueous solutions (formalin). It requires a 2-4ml sample of fluid and can give a good indication of alcohol concentration. As highlighted by Rob, this is not a test for the presence of formalin, but rather just that the solution is aqueous or an alcohol with water combination. This method is awaiting peer review, but if anyone has any queries please get in touch and I would be happy to share my research.

To determine the amount of formaldehyde/formalin in solution there are several methods available. I have tested three commercially available methods, and a titration method to determine formalin concentration initially developed by Rob Waller and refined (very slightly) by myself. In testing these different methods, comparisons and assessments about the advantages and disadvantages of each method were made.

One of the first challenges is getting your head around the terminology we use when describing formalin, and this seems to vary between countries and institutions. What we often call “10% formalin” is actually a dilution factor, from diluting a 1 part 100% formalin stock solution with 9 parts water. This 100% formalin stock solution is 37% by weight or 40% by volume formaldehyde gas in water. This means that “10% formalin” is 3.7% (w/w) or 4% (w/v) formaldehyde gas in water, which is 40,000 mg/L formaldehyde.

The titration method, has the best resolution of the methods tested, only needs to be conducted once without the need for multiple dilutions, also gives results for titratable acidity, and has a small sample size of 0.75ml. Due to the costs of equipment set up and materials for analysis, this would be a good method for institutions who want to quantify the amount of formalin/formaldehyde in solution in fluid preservatives and were aiming to conduct many tests, which would reduce the overall cost per test.The paper that details the titration method and comparison to the commercially available methods, is also currently awaiting peer review, to be published later this year in Collection Forum.

Two types of commercially available formaldehyde test strips were tested (MQuant and Quantofix), and these give semi-quantitative results. As discussed on the listserv previously, these test strips can be very challenging to use and require significant dilution and calculations to get accurate results. They measure in the range of 0mg/L to 100mg/L or 200mg/L. “10% formalin” (4% w/v formaldehyde gas in water) is 40,000mg/L so to get results in the range that the test strips can read dilutions up to 1:1000 may need to be made. This can be time consuming and costly as often more that one test strip and dilution are required to get a result within the test strips range.

A commercially available titration test kit, which uses the same chemical reaction as the titration method above, was also tested (Hach Formaldehyde Test Kit: Model FM-1). This can test formaldehyde concentration in solution within the ranges of either 0.05 - 1% or 0.5% - 10% formaldehyde in solution (here is where terminology is important – what we often call “10% formalin” is 4% w/v formaldehyde gas in water).
The solid reagent supplied with this test kit is insoluble in ethanol, which is an issue when testing for residual formalin in alcohol solutions. When I tested ethanol solutions, I first dissolved the contents of the reagent sachet in 10ml demineralised water and added that to the sample before titration. Even though the sample was diluted the drops of titrant were still counted as though each drop represented 0.05% formaldehyde.
The resolution of the results with this commercially available method is not as great as the titration method above, and the sample size for the tests is significantly larger (1ml or 10ml), however it is a simple to use method and all the required materials are supplied. I would recommend for people wanting to use this method to contact the supplier when ordering and request for a lid for the test vial, to avoid spills when mixing the solid reagent with the fluid preservative sample using the manufacturer's published method.

Methods to test fluid preservatives need a lot more research, and this will enable us to have a greater understanding of the fluid chemistry and the impacts on specimens long-term preservation.
From a health and safety perspective it is important for us to quantify how much formaldehyde is in solution in fluid preservatives, be it from preservation in formalin or residual in alcohol preservatives from initial fixation in formalin.

If anyone would like more information about any of these methods, they will hopefully be published later this year, but in the meantime I would be happy to discuss them with you – please get in touch!

All the best,
Irene Finkelde

On Fri, May 29, 2020 at 7:51 AM Hawks, Catharine <HawksC at si.edu<mailto:HawksC at si.edu>> wrote:
Am hoping that Irene will be able to respond - her work on this issue has been phenomenal and is soon to be published.
Sent from my iPhone
Catharine Hawks
________________________________
From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu<mailto:nhcoll-l-bounces at mailman.yale.edu>> on behalf of Mandy Reid <Mandy.Reid at austmus.gov.au<mailto:Mandy.Reid at austmus.gov.au>>
Sent: Thursday, May 28, 2020 5:40 PM
To: Robert Waller; nhcoll-l at mailman.yale.edu<mailto:nhcoll-l at mailman.yale.edu>
Subject: [Nhcoll-l] Test for formalin

External Email - Exercise Caution
Thanks Rob
You are absolutely right and I agree this is a very important distinction. I hope you don’t mind that I have copied it to the broader mailing list but kept the header so it is linked to the previous comments.
Cheers
Mandy

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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From: Robert Waller <rw at protectheritage.com<mailto:rw at protectheritage.com>>
Sent: Friday, 29 May 2020 3:53 AM
To: Mandy Reid <Mandy.Reid at austmus.gov.au<mailto:Mandy.Reid at austmus.gov.au>>
Subject: RE: Test for formalin

Hi Mandy,
That may be completely adequate for your needs but from a health and safety perspective we should recognize this is not a test for the absence of formalin but, rather, for the presence of alcohol. In that sense, it should not be thought of as a “test for formalin” but a “test for alcohol” with the understanding that the alcohol may or may not also have a significant concentration of formalin. Again, that may not be important in your application but we always do well to ensure terminology does not lead to misunderstandings.
Rob

From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu<mailto:nhcoll-l-bounces at mailman.yale.edu>> On Behalf Of Mandy Reid
Sent: Thursday, May 28, 2020 2:21 AM
To: nhcoll-l at mailman.yale.edu<mailto:nhcoll-l at mailman.yale.edu>
Subject: [Nhcoll-l] Test for formalin

Thank you to all the people who responded regarding testing for formalin when you are unsure whether a specimen is stored in ethanol or formalin (particularly problematic in historic museum specimens). I had an excellent idea sent to me by colleagues from NIWA (The National Institute of Water and Atmospheric Research in Wellington, New Zealand) that I would like to share. It is very simple, very inexpensive and it is very effective.

Simply draw a line of permanent marker on a strip of wet label paper. Dipped into a formalin solution, the marker stays intact. Dipped into an into an ethanol solution the marker starts running, or bleeding into the paper.

I tried it and it works perfectly. I have attached an image.

Cheers
Mandy
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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