Hi guys,
So I am currently working on the methodology for a macroalgae decomposition study, assessing changes in weight and nutrient contents (specifically N and P) at varying stages through the decomposition process. My question really relates to the preparation of the samples for shipment to a lab for the necessary analysis:
1. Like similar studies I have read, I intend to dry the recovered material at 60 degrees C, and grind the thalli using mortar and pestle. I have read that liquid nitrogen can be used to make the use of the mortar and pestle more efficient, as it freezes the thalli making it more brittle. Since the liquid nitrogen obviously makes the material brittle enough to grind into a powder, is it still necessary to dry the thalli at 60 degrees C?
Its a good idea to check if any changes occur due to drying using nitrogen. and if usual procedures dry the material, its good idea to do same unless you find its ok through your experience
Yes, it should definitely be dried, and that is why proteins (a source of nitrogen) have a high capacity to absorb water and store it in the tissues. Therefore, the final results of calculating the nitrogen percentage will be definitely affected.
Changes to some organic and ephemeral inorganic species can occur during drying at 60-80 C, but if you are interested in N, P and other nutrient elements those can be ignored. The important thing is that the drying is rapid, i.e. do not try to dry large amounts that 'sweat' and 'cook' internally. Rough cutting with scissors can speed up the drying.
Using liquid nitrogen on fresh green material and grinding results in a paste, and to maintain the benefits of the low temperature, the paste should be freeze-dried
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