[Nhcoll-l] [MOGELIJK SPAM ! *****] Antw: Re: Test for formalin

[A.J.van_Dam at lumc.nl]

Dear Joachim,

When a buffer like borax or a humectant like glycerol is added to ethanol 70 it might indeed significantly change the density of the fluid. However, dissolved animal fats and small excretions from the body likely lead to only a very slight offset in density.

In ethanol just about 2% of animal fat can dissolve, which will give a very minimal change in the density of the fluid (<1% EtOH), also because animal fat itself has a density which is in the same range as that of ethanol 50-60%. Also, most organic salt excretions from the body don't dissolve very well in ethanol 70.

Therefore, I believe density measurement by hydrometer, by digital density meter, or by using the Alcomon Indicator System are sufficiently accurate, convenient and very useful tools in collection management of fluid preserved specimens.

Kind regards,

Dries

Andries J. van Dam | conservator

Museum of Anatomy | Leiden University Medical Center | Building 3 (V3-32)
P.O.Box 9600 | 2300 RC Leiden | The Netherlands
Visiting address: Hippocratespad 21 | Tel: +31 (0)71 52 68356 | E-mail: A.J.van_Dam at lumc.nl<mailto:A.J.van_Dam at lumc.nl>

Scientific associate | Natural History Museum London | http://www.nhm.ac.uk<http://www.nhm.ac.uk/>
________________________________
From: Nhcoll-l [nhcoll-l-bounces at mailman.yale.edu] on behalf of Joachim Händel [Joachim.Haendel at zns.uni-halle.de]
Sent: Friday, May 29, 2020 8:16 AM
To: irenefinkelde at gmail.com
Cc: nhcoll-l at mailman.yale.edu
Subject: [MOGELIJK SPAM ! *****] [Nhcoll-l] Antw: Re: Test for formalin

Hi all,
Dear Irene,

Thanks very much for the interesting information.

I heard about the use of digital density meters and I also know museums and collections that work with such devices.
But I am still sceptical about this.
What about the organic components, which are dissolved out of the preparations by the alcohol (fats, dyes, stomach contents of small animals ...)
In this case it is no longer a pure water-alcohol solution and the density datas are falsified.

Allthe best
Joachim






--
Joachim Haendel

Center of Natural SciencesCollections
of the Martin-Luther-University
- Entomological Collection -

Domplatz 4
D-06099 Halle (Saale)
Germany

Phone:  +49 345 - 55 26 447
Fax:  +49 345 - 55 27 248
Email: joachim.haendel at zns.uni-halle.de



>>> Irene Finkelde <irenefinkelde at gmail.com> 29.05.20 3.09 Uhr >>>
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




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