preserved specimens

Preserved specimens: We have some preserved baby sharks for which the solution needs topping up. We don't know what solution is currently in the glass container—was here before I started. What is the correct solution to top the container up with? Thanks.

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Publication Date: 11 February 2015
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preserved specimens

Firstly, if you do not know what the solution is, it is important not to top it up. Extra care is required in handling unknown chemical solutions. We understand that it is difficult when you inherit a situation where a preserving solution is not labelled.

Handling unknown chemical solutions

It is not advised to top up the unknown chemical solution that has been preserving the shark specimens for several reasons.

  1. You may be combining incompatible chemicals, which may generate new substances that have unknown properties and unknown hazards.
  2. The stability of the chemical is not known and you may create a violent chemical reaction or dangerous substance.
  3. The concentration of components of the original preserving fluid may have altered due to the evaporative loss.
  4. The solution that is produced may damage the specimen.
  5. The solution may discolour or become cloudy not allowing the specimen to be viewed.

‘Managing risks of hazardous chemicals in the workplace – Code of Practice’[1], states:

Sections 2.1 Identifying hazards

“The first step in managing risks involves identifying all the chemicals that are used, handled, stored or generated at your workplace…”

Section 2.3 Labels

“If the contents of the container are not known, this should be clearly marked on the container, for example, 'Caution - do not use: unknown substance'. Such a container should be stored in isolation until its contents can be identified and, if it is then found to be hazardous, the container is appropriately labelled. If the contents cannot be identified, they should be disposed of in accordance with relevant local waste management requirements.”

Sections 4.2 Specific Control Measures: Keeping Hazardous Chemicals Stable and Transfer of Hazardous Chemicals.

“This section includes information on key control measures that should be considered when managing risks from hazardous chemicals in the workplace.”

The chemicals used to fix and preserve specimens can be hazardous and dangerous and may include chemicals such as formalin[2], 70% ethanol and a range of other chemicals. Science ASSIST recommends you treat all unknown chemicals as hazardous and conduct a site-specific risk assessment to assess and control the risks. You will need to determine how to safely handle and dispose of the solution. We have developed a Risk Assessment template for schools to use, see Risk Assessment Template. You will also need to make sure that any new preservatives you use are approved for use in your jurisdiction and educational sector. Local guidelines for the disposal of waste fixative and preservative chemicals should be followed.

Replacing the old preserving solution

If you consider the shark specimens to be in a condition worth saving, it is recommended to go through a procedure of decanting followed by rinsing then replacement with new preservative solution. You will need to take precautions to avoid exposure by contact with skin and eyes, inhalation, and ingestion.  It is recommended to work in a fume cupboard and wear appropriate PPE. You should not pour any unknown chemical down the sink. And, at all times care must be taken to avoid damaging the specimen in the process.

When working with preserved specimens it is important to:

  • refer to the specific SDS for the new chemicals being used;
  • wear appropriate PPE (i.e., safety glasses, gloves, laboratory coat, closed-in shoes);
  • work in a fume cupboard or well ventilated area.

Here is a simple method for replacing your old preserving solution.

  1. Working in the fume hood or well ventilated area, decant the solution into a glass container which can be properly sealed to avoid evaporative loss. Label as 'Caution - Do Not Use - Unknown Substance (possible fixative or preservative)' for disposal via a chemical waste contractor. Whilst waiting for pickup, store and segregate the waste chemicals safely in approved store rooms or chemical storage cabinets.
  2. Wash the specimen several times by soaking for 30 minutes in tap water to remove the old preservative. Collect the washings and store and dispose of as above.
  3. Take the specimen through several increasing concentrations of the new fresh preservative (e.g., 1 day in each of the following concentrations 30%, 50% and 70%) to avoid any osmotic issues. Always handle one specimen at a time.
  4. Place the specimen into the final preservative solution in a clean glass container that has a tight-fitting lid to prevent any evaporation. Use either 70% ethanol or one of the safer alternatives (see below). The use of Parafilm or some silicone sealant can be used to provide a good seal.
  5. Label the container to state type of specimen, type and date of preservative. Most museums put the jar label inside the jar, not on the outside or on the lid.  This will lessen the likelihood of the specimen and label being separated. It is important to use paper intended for long-term preservation in fluids. There are a several papers that will do. The Australian Museum[3] currently uses Resistall paper, which they source from the US, but other types of papers have been used in the past including laundry tag paper: http://www.universityproducts.com/cart.php?m=product_list&c=241 . Soft lead pencil can be used to write on the paper and there are certain inks or ink pens that can be used as well. Any inks used should be of archival quality, resistant to fading and smearing, and be insoluble in the preservative solution. Suitable inks and ink pens can be found in some art or office supply stores and museum supply companies. It is recommended to allow the ink to completely dry before placing the label into the storage solution. Ordinary ballpoint pens should not be used for labelling as they generally dissolve in most preservative solutions. See the Science ASSIST School science suppliers list for local museum supply companies for similar products.
  6. Store under conditions to prevent any deterioration i.e. a cool dry place in low light levels and out of direct sunlight.

FIXATION & PRESERVATION METHODS

When preparing specimens for preservation they are generally put through a multi-stage process.

  1. Fixation to prevent autolysis and microbial breakdown.
  2. Water wash to remove excess fixative.
  3. Preservation for long-term storage.

Fixation: Traditionally, marine vertebrates are fixed in a solution of formalin, usually a 10% solution made by combining 1 part formalin with 9 parts water. This is still the best fixative in use today. Formalin is toxic, carcinogenic, highly irritating, acts as a potent sensitizer and should be handled with great care in a fume cupboard or well ventilated area.

Long Term Storage: 70% ethanol has been the method of choice for long-term preservation. Ethanol is highly flammable, prone to rapid evaporation and is a skin irritant. It is also possible to preserve fish specimens for a long time in formalin. Some reports indicate that the formalin is required to be buffered, as the high acidity is able to render some specimens brittle and transparent.

Here are some links to interesting articles on the fixation and preservation of wet collections in general as well as some specific to fish:

http://conservation.myspecies.info/node/33  

https://www.nps.gov/museum/publications/mhi/appendixt.pdf  

http://www.burkemuseum.org/research-and-collections/ichthyology  

http://research.amnh.org/vz/ichthyology/congo/other05.html

ALTERNATIVES

Today there are some less-hazardous alternatives to these traditional fixatives and preservatives. However, some are untried for long-term storage and may not protect the specimen adequately.

Glycerol (synonyms: glycerin, glycerine) is a safe and reliable alternative to ethanol. Glycerol has low-toxicity, a flash point at 160°C, preserves and revives colour. And, if the specimen is transferred through baths of increasing concentration, it will not shrink the specimen. The Australian Museum3 uses either 100% glycerol or 70% ethanol for preservation of its fish specimens.

Another alternative is 2-phenoxyethanol (synonyms: phenoxetol, phenoxytol) which is non-flammable compared with 70% ethanol and is less volatile and of lower toxicity when compared with formaldehyde. See the following article which discusses the relative hazards of 2-phenoxyethanol compared with formaldehyde and ethanol: https://www.academia.edu/9751098/Phenoxetol_as_a_formaldehyde-removing_agent_for_long-term_preservation_our_experience

See the following link for a recipe: https://web.archive.org/web/20170219043724/http://www.rtg.wa.edu.au/solu... (redirected to Internet Archive's Wayback Machine, July 2017). Note that this is a storage solution only and was introduced because it is non-flammable. This removed the requirement in WA to store specimens that were preserved in 70% ethanol in a flammable liquids cabinet.[4]

The following link has good information on traditional and alternative fixation and preservation fluids:  Fluid Preservation: A Comprehensive Reference

It is important to check that the preservative you choose is approved for use in your jurisdiction and educational sector.


[1] Safe Work Australia. 2012. ‘Managing risks of hazardous chemicals in the workplace – Code of Practice’ http://www.safeworkaustralia.gov.au/sites/swa/about/Publications/Documen... Copyright https://creativecommons.org/licenses/by-nc/3.0/au/

[2] Formalin is a solution of formaldehyde (methanal), usually a saturated (37%) solution.

[3] McGrouther, Mark. 2015. Fish Collection Manager, Australian Museum Research Institute, Australian Museum, Sydney. Personal communication

[4] Kempton, Ruth. 2014. Team Leader, Regional Laboratory Technicians, WA Department of Education. Personal communication

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