Sample prep artifacts with plankton strews

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Sure Squintsalot
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Joined: Mon May 16, 2022 3:44 pm

Sample prep artifacts with plankton strews

#1 Post by Sure Squintsalot » Sat Feb 25, 2023 11:42 pm

Not entirely clear what's going on here:
Screenshot 2023-02-25 161211.jpg
Screenshot 2023-02-25 161211.jpg (76.07 KiB) Viewed 872 times
Eyepiece photos with phone at 200x with DIC, heavily cropped. I know, I know....pretty lousy shots.
Screenshot 2023-02-25 161427.jpg
Screenshot 2023-02-25 161427.jpg (113.42 KiB) Viewed 872 times
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This is a strew that had been rinsed out of a plankton net with 91% isopropyl alcohol (IPA) then rinsed again a few days later in fresh IPA and stored since October. I rinsed again in fresh, clean IPA, and dropped the sample on to a cover slip and let dry. So far, I've not done anything different with this sample that I've not done with other plankton strew slides I've prepped.

After the cover slip dried, I put Permount on a slide, dropped on the cover slip, and sucked out the air bubbles in my vacuum chamber. Like my other strew samples, it fairly effervesced with bubbles. Following this, the sample was weighted on an inverted iron at about 100 deg. C for a few hours until the mountant set hard. Again, nothing different than the other dozen samples I've prepped.

However:
1) A lot of my plankton has developed tiny squarish crystals within the walls. They could be cubic crystals....can't really tell, but they are overwhelmingly found within plankton walls (A). Actually, they don't look birefringent. Could they be halite? How did they form and why now? Could they be crystal casts?
2) Parts of this slide have also developed much larger, odd, birefringent crystals in random parts of the mounting medium (B).
3) I keep a working bottle of Permount with a rubber eyedropper for slide prep. Over time, the Permount seems to spontaneously disappear; I guess the volatiles are escaping from the rubber squeeze bulb, so I periodically add a little Xylene to thin it some. Did my mixture cross some chemical stability threshold?


Anyone have any ideas?

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