The easiest way is to divide the stock 25% solution to vials with volume which one typically needs for one preparation and store them in a conventional - 20 C freezer.

Hi! It should be less than 25°C

Dear Tatiana,

thank you for your quick answer. So is it not necessary to store it in the fridge? At least, in winter...

Usually in the storage rooms the temperature is constant and should be between 17-23 °C What temperature is in the place of the storage in your company? Of cource glutaraldegide shouldn't be frosen. But it can be about -18 °C . I guess you have no such frost.

We store it in a safety cabinet in the lab, but during summer temperatures may reach 25-30 degrees. Maybe in that period would be optimal to store it in the fridge

Yes, it will be much better

So, succus: as of my experience, storage of glutaraldehyde solution (hydrous 25%, and working solution for fixation 2.5 - 5% too) not only ALWAYS was in the fridge (say 4-8 degrees C), but always the "empty" volume after dispensing for working solution was filled up with N2 gas from pressure-cylinder to prevent oxidation.

Thank you Wolfgang H. Muss !

I always stored glut in a fridge. I prefer to buy it in ampules. I have seen too many specimens ruined by old glut, so I am a bit overcautious. I prefer to store prepared fixative in a freezer (in plastic bottles, of course).

From https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma-Aldrich/Product_Information_Sheet/g5882pis.pdf

Purified samples of 25% glutaraldehyde stored at -20 °C showed virtually no change in their UV absorbance characteristics even after 8 months.1 However, solutions are very heat sensitive.

Dear Barbara Loi , you're welcome.

I only would ask honestly for more detailed characterization of your "grade II" GA, 25%, "... It is not for electronic microscopy, but only for fixation of histological samples coupled with formalin. On the package, there is no indication on the optimal temperature" ...

so we can assume you're using e.g. SIGMA # G6257 (or other supplying company)

".. Caution : This grade is not recommended for use as an electron microscopy fixative.

• Not refrigerated en route and
• Preparation Note : Not specially purified. "

Contrary to the former, Glutaraldehyde solution, Grade I, 25% in H2O, specially purified for use as an electron microscopy fixation (as ascribed for SIGMA #G5882), is

• shipped in (sic!) [must read: ON or with !] dry ice [which is - at normal pressure - approx. minus 78 to minus 76°C], and the
• storage temperature is recommended to be −20°C.

I understood that you "don't need" purified Grade I Glutaraldehyde stock solution for your task (assuming you are doing 'histology only' on fish or other marine animals?), and I don't think you are using (the previously termed quality: "For histological use" or "For use in Histology") that quality for some reason, BUT not because of financial restrictions of your lab budget... [seconding Vladimirs reply abov: ".... have seen too many specimens ruined by old glut ..."]...

Why in my previous answer I recommended cooling the Grade II GA-stock as well as the working fixative solution at least in a lab-fridge I would like to comment as follows:

1) Grade II - as indicated above (regardless of other supplying companies) is not specially purified, hence: 'unpurified' .... which means that it contains plenty of di-,tri and polymers of aldehydes depending on duration of (mostly) unfavorable storage conditions after production.

2) Further polymerisation of the aldehyde solution occurs permanently on storage at room temperature and might be boosted by higher temperature, and/or by increased oxidation due to opening and leaving open the storage bottle more often and for longer time than really needed, as well as increasing water percentage/ pulling moisture *)[see bottom note], especially in / under warm/hot and humid climate conditions.

3) so one could recommend to prepare convenient volumes of working fixative portions

- if known to be needed more often in the near future *)[see bottom] or standardised for many specimen preparations *)[see bottom]

- e. g. 10 x á 100 ml in plastic vials with tightly lockable screw-caps - replacing slowly & cautiously residual space of air by N2-gas, which is heavier than our atmosphere, before closing the screwcap), then store **)

*) 'near future': at the maximum 1-1.5 months (provided being stored **) in the lab-fridge at 0°C to 4°C).

NB: BEFORE opening the storage bottle or storage vials/tubes always let warm up the content to room temperature!

DISCLAIMER: I am not affiliated with the company mentioned herein [SIGMA] and have no financial interest. I - in former times - just was happy user of highly purified, critically (and documented) - during storage and shipping - cooled 25% Glutaraldehyde solution from another (EM-lab chemicals) supplier.

The easiest way is to divide the stock 25% solution to vials with volume which one typically needs for one preparation and store them in a conventional - 20 C freezer.

Dear all,

the reason why I bought Glutaraldehyde solution, Grade II (yes, similar to SIGMA # G6257 but from another company) is not for saving money, but because I am not going to work with electron microscopy. Specifically, I need it to prepare the 4F:1G fixative (4 parts of formaldehyde+1 part of glutaraldehyde) for fish larvae, as suggested by Papadakis et al. I contacted with the company that sold me the solution, they told me to store it in the fridge. I hope it will work well without losing important samples!

Dear Barbara Loi , thank you for your kindly given explanation... I appreciate that.

I am sure you found out already that 'ready to use' '4CF-1G fixative' (originally "invented" / published by McDOWELL & TRUMP 1976, *) cf. bottom line and see pdf enclosed)

will precipitate easily on longer storage at RT, especially when made up in plastic containers up to 5 L and without light shielding. as of the second Literature Reference given below you might use specimens also for ultratsructural examination, provided you embedded some of your specs into (acrylic, methacrylic, expoxy-)resin.

Added here just for bibliographical reasons and convenience of other readers ogf this thread:

PAPADAKIS et al.(2009) (unfortunately only PPV=Pay-Per-View, US-$ 39,95):

Histological evaluation of the elimination of Artemia nauplii from larval rearing protocols on the digestive system ontogeny of shi drum (Umbrina cirrosa L.)

( Aquaculture, Vol 286, Iss's 1–2, 7 January 2009, Pages 45-52 )

https://www.sciencedirect.com/science/article/abs/pii/S0044848608006601,

but most interesting also (since besides macro-images) also 'thin' methacrylic resin sections (histopathology) as well as (S)EM & (T)EM and FISH-images of affected larvae are shown in that really impressive article (free access) by:

Katharios et al.(2015): 'Environmental marine pathogen isolation using mesocosm culture of sharpsnout seabream: striking genomic and morphological features of novel Endozoicomonas sp.'

[ Scientific Reports volume 5, Article number: 17609 (2015) ], cf.

@ https://www.nature.com/articles/srep17609

McDowell EM, Trump BF (1976): Histologic fixatives suitable for diagnostic light and electron microscopy. Arch Pathol Lab Med 100 pp. 405-414 (1976)

also see: Article Histologic Fixatives Suitable for Diagnostic Light and Elect...

(I intended to reference to = https_://europepmc.org/abstract/MED/60092

NB: since the ResearchGate system links rapidly to the own source = Article

Histologic Fixatives Suitable for Diagnostic Light and Elect...

it is necessary to include here another letter / sign in the previously added original URL to be visible as such: therefore: if copying and pasting into your browser, prior to clicking for access, DELETE the UNDERSCORE sign in between

https _ :// !)

Best wishes and regards, W.H.M.

The storage temperature of glutaraldehyde (grade II, 25% in H2O) is 4°C. And it is preferable that it be prepared in filtered water from where it extracts the larvae, either seawater or fresh water, but filtered. And it is necessary to keep the sample at 4 ° C (in refrigeration) while making the fixation