Is 4% formaldehyde is better or 70% ehthanol is better...or any other presevative i use for long time presevation
Dear Nilima,
To prevent fungal contamination, we routinely add a few drops of formaldehyde [you do not need a final concentration of 4% to preserve digested material in which only silica frustules and possible remains of organic substance should be present] to vials that are to be stored for long periods of time (diatom collection).
Best wishes.
Marco Cantonati
Ok sir...kenneth M Tore and Marco cantonati sir..thxs for your reply..
Dear Nilima,
I preffer to preserve diatom frustules in a 70% Ethanol in 5 mL glass bottles (not plastic). After my experience if I re-used stored diatom frustules in formaldehyde, by the preparation the permanent slides were not always usefull for a high quality microscopy (fine structures). Especially in a case if there were a lot of small diatoms (5 um) and small sediment particles in samples. After using formaldehyde stored frustules there were still residues of some undeffinied maybe formaldehyde particles inside the frustules in a permanent slides. The another reason why I do preffer to use a 70% Ethanol that it has not so much potentially hazardous levels as formaldehyde has.
Thank you for sharing your question.
Best wishes
Bohuslav
for a good fixation of diatoms or phytoplankton in general, Lugol is the most recommended because it keeps the shape of the cell in a good state. For the health side of the analyst, it does not present problems for the eyes unlike formalin and counterparts that cause anergy.
Ethanol is recommended for long term preservation.It is safe to use.and less hazardous than formaldehyde.
Thank you.
How did you clean them? Did you acid wash and oxidize with hydrogen peroxide? If so, I feel there's no need for formaldehyde. Ethanol or Lugol's will be fine. I often mount mine in resin, such as Naphrax, on microscope slides for permanent archival.
Yes jay sir..i use dr.cantonati's method..hydrogen peroxide and acid wash..it gives very good results..and thxs for ur reply..
can i use 70% ethanol for presevation..or just put few drops in clean diatoms..i want it for long time presevation..
And for permanant slide can i use canada balsum or dpx...in india..pleurax ,zrax is not aviable..
Thxs for ur reply sir..
I store them in plastic bottles.. n add few drops of formalin and distilled water in it..n store in room temp..
Later i use that stored samples for permanant slide preparetion..
Can i use mountant canada balsum..or dpx..i was tried it in dpx..on 40x diatoms are seen clear..but on 100x they seen dim,blurry..is it problem due to use fixative dpx?
I also try for semipermanent slides..with glycerin...nailpaint was use as sealent..but slide was not good as like.. in water mounting..
I also want other good sealent..which fix coverslip very peoperly..
With regard to refrigerating clean diatoms in distilled water be carful when long term storing is carried out material might be damaged
You bring up a valid concern about storing in distilled water. Due to health concerns (I work with undergraduate students), I choose not to add a few drops of formaldehyde to the vials. If I plan on making slides within a few weeks or months of cleaning, I store at 4 C in distilled water. If longer, I'll use something to preserve.
Thxs moshe sir..for ur reply..n thxs also to jay sir..
N jay sir..what is use you for long time presevation..is it lugol or ethanol or any other...give me total procedure for it..
After we have cleaned the diatom material, we add 1 drop of 10% HCL and then allow the material to dry in a glass vial.
For long-term preservation of diatoms after thorough cleaning and separation, the preferred preservative is a mixture of ethanol and glycerol. This combination helps to immobilize and stabilize the diatoms, maintaining their morphology and preventing degradation over extended periods. Here's a general guideline for preparing the preservative:
It's important to note that preserving diatoms in the ethanol-glycerol mixture does not immobilize them entirely. Diatoms may still move slightly within the preservative, making it suitable for long-term storage and morphological studies.
Another commonly used preservative for diatoms is formaldehyde (formalin). However, formaldehyde is a hazardous and potentially toxic chemical, so its use requires careful handling in a well-ventilated area and adherence to safety guidelines. Additionally, formaldehyde may cause changes in the morphology of some diatom species, which can impact scientific analyses and taxonomic studies.
Overall, the ethanol-glycerol mixture is a widely accepted and safer option for preserving diatoms for extended periods while maintaining their structural integrity. Properly preserved diatom samples can be used for various scientific studies, such as ecological assessments and paleo ecological investigations.
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