Hello, I am currently working on the impact of cyanotoxins on fish and in my protocol they told me to freeze-dry the organs, my question is which desiccation choose? primary or secondary? thank you
Hello - freeze drying has primary drying (removing bulk solvent, most often water) and secondary drying (removing water molecules bound to the sample). They are two parts of the same process, often using different conditions.
This paper may help:
https://www.scientificproducts.com/resources/articles-tech-notes/basic-principles-of-freeze-drying
Drying an organ takes time, as it is a complex structure - most papers are written about drying a single homogenious sample e.g. a drug. If you do not need to maintain the structure of the organ, macerate it first and dry that - it will freeze dry faster and it will be easier to remove all the water from the cells. If not, then then suggest freezing the organ first in a [small] block of ice, to maintain tissue structure as best as possible. Put this in the freeze dryer and run for some days, time is hard to tell as you are waiting for water to diffuse out of the inmost cells.
Rob
it is recommended to use a secondary desiccation for lyophilizing fish organs for cyanotoxins analysis. This is because a secondary desiccation system can trap the moisture that is released during the lyophilization process, preventing it from contaminating the samples. Additionally, secondary desiccation can help to maintain the integrity of the samples during the lyophilization process. However, it is always best to consult your protocol or supervisor for specific guidance on the best desiccation system to use for your experiment.
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