I am looking to combine and crush 5 foraminifera to create a homogeneous carbonate powder that I will then be sending out for oxygen analysis. Does anyone have any good methods to make these little guys into powder without creating contamination? I was initially thinking of using a mortar and pestle, but the sets that I have access to seem very large and scratched up. I fear that the carbonate powder may get trapped in the scratches between samples and get moved to a later sample. Thank you for any input!
Hi,
You can use micro-drilling machine to take a few mg
Cordially
If you put your foraminifera in the sample holder of the mass spectrometer (they are usually little tubes of around 3-4 mm in diameter, with a hole) then you can crush them with a small glass stick with a smaller diameters. Then you clean the glass stick with acid to remove any carbonate remains.
You need not crush the tests, unless you plan to clean them. Generally, whole pristine tests are used for stable isotopic analysis. If you want to clean the tests, then use a clean glass plate. Carefully place your tests on the glass plate. Place another clean glass plate on the top of the glass plate with tests. Gently press the upper glass plate, so as to break open the chambers, without powdering the fragments. If you want to crush benthic foraminifera tests, it is better to add a drop of MiliQ water to avoid spluttering of fragments. Transfer the fragments to centrifuge tube by using a clean brush.
I do not know what mass spectrometer the colleague Saraswat uses, his method looks very strange to me.
For isotopic analyses you NEED to crush and powder the specimens. The powder afterward is placed to react with orthophosforic acid. Otherwise the whole test or even fragments do not react properly, and they do not give enough CO2 for the isotopic analyses.
Dear Silvia, several labs world wide use whole tests for O-C isotopic analysis, unless (A) splitting the samples for both elemental and isotopic analysis and (B) clean the tests prior to O-C analysis.
Pick clean shells approximately 20 numbers in the narrow size range
(I took 250-315 microns) , cleaned, and homogenised by grinding
with ethanol. A sub-fraction (~40 mg) was used for oxygen isotope
analysis. Silvia Spezzaferri
Sorry, I am working a lot with isotopes and with prestigious isotope labs and I have never heard about using whole tests. The cleaning mentioned is for Mg/Ca.
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