Diatom cleaning by incineration

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MicroBob
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Diatom cleaning by incineration

#1 Post by MicroBob » Tue Jun 30, 2020 9:55 am

Hi together,
in the past I have cleaned diatom samples in a small oven at 450 degree C for 30 min.
Frustule pairs and algae groups stay together and the frustule structure is visible very clearly. Now I'm experimenting with more compact setups with stainless steel plate, alcohol stove, micro gas torch and micro gas powered heat gun. The main difficulty is to oxydize the carbon (black becomes gray) and to avoid deforming the cover slip. Depending on the diatom species they too could deform, probable weakly silicified marine diatoms are most vulnerable here.

Have you tried this before, what methods did you use and how were your results?

Here two photos:
1. Asterionella group with well oxydized carbon
2. The carbon imprint of a Pediastrum group that should have been removed completely :?

Bob
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Hobbyst46
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Re: Diatom cleaning by incineration

#2 Post by Hobbyst46 » Tue Jun 30, 2020 7:42 pm

Bob,

You probably remember my diatom incineration experiments from more than a year ago. Some folks found it of interest. i was not happy with the results. Burnout was incomplete, it left black dots on the slide, and diatoms (not all of them) were deformed, although the temperature was controlled.

Diatom incineration is mentioned in the literature. For example, in the book by MacLaughlin (published by McCrone), pages 234-236. They mention that cleaning by incineration is usually not perfect. They do not mention the frustule deformations. Perhaps incineration (as well as other protocols) is practical for certain, specific diatoms. It is, after all, much easier to do than chemical cleaning. Certainly easy for a research lab, where an oven of up to 600-800C is common. I have surveyed the methods and results sections of more than 20 research articles on diatoms. None of them included cleaning by burn and incineration.

To me, it means that incineration is a rapid yes-or-no test, to verify that frustules of interest are in the collected sample - just what you are now enjoying on the lake !

Keep them coming !
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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75RR
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Re: Diatom cleaning by incineration

#3 Post by 75RR » Tue Jun 30, 2020 7:57 pm

To me, it means that incineration is a rapid yes-or-no test, to verify that frustules of interest are in the collected sample - just what you are now enjoying on the lake !
One would think that viewing wet slides would provide that information, to genus level anyway. I wonder if it would be possible to add a temporary mountant to the incinerated slide that would allow ID to species level with high power objectives?
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
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MicroBob
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Re: Diatom cleaning by incineration

#4 Post by MicroBob » Wed Jul 01, 2020 8:18 am

Hi Doron,
I recently read an article where they specifically compared inicineration and chemical cleaning for low silicified mediterranean sea diatoms. They found much less broken frustules after incineration cleaning. The research was probably directed towards identifying and counting and they probably didn't look for deformed diatoms and clean slides that much. Hustedt also wrote that harsh chemical cleaning is not usable for very fragile diatoms.

Hi Glen,
water with r.i. of 1,3 should give goog contrast but loosen the diatoms from the cover slip. Cinnammon bark oil has an r.i. of 1,6 as far as I remember. But generally I like to make permanent slides to have a second look at them later. Interestingly some diatoms were so concealed in live state that they only became apparent after the cleaning.

Bob

Hobbyst46
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Re: Diatom cleaning by incineration

#5 Post by Hobbyst46 » Wed Jul 01, 2020 11:58 am

75RR wrote:
Tue Jun 30, 2020 7:57 pm
To me, it means that incineration is a rapid yes-or-no test, to verify that frustules of interest are in the collected sample - just what you are now enjoying on the lake !
One would think that viewing wet slides would provide that information, to genus level anyway. I wonder if it would be possible to add a temporary mountant to the incinerated slide that would allow ID to species level with high power objectives?
I would call my home-bred mountant recipe "temporary" since it stays usable and clear up to about 3 months. Easily made from cinnamon bark oil (NOT cinnamon leaf oil) and styrofoam (which is polystyrene). It smells of cinnamon (unastonishingly), so better use in a ventilated space, but is not considered harmful AFAIK. The CBO-PS mixture does not harden, but is viscous enough to allow immersion oil high NA viewing. The coverslip should be sealed with GEL nail polish, that is cured with UV (a few minutes) or with strong direct sunlight.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MicroBob
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Location: Northern Germany

Re: Diatom cleaning by incineration

#6 Post by MicroBob » Wed Jul 01, 2020 7:35 pm

So what is diatom cleaning by incineration good? Find the answer yourself, here an image of a Tabularia diatom ensemble doing a half roll. :D
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Hobbyst46
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Re: Diatom cleaning by incineration

#7 Post by Hobbyst46 » Wed Jul 01, 2020 7:56 pm

1:0 Bob ! very charming !
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

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