#RealTimeChem and Isotopic Analysis of Fossil Teeth

Here’s another post for #RealTimeChem week (@RealTimeChem on Twitter). Today, we’re running isotopic analyses of the fossil teeth that we pretreated earlier.

Earlier this week, I weighed the samples. Well, I tried to weigh the samples.

I made it back into the lab, and started again.

 

You don’t need a lot to get an analysis, but these tiny samples are pushing the limits!

 

Sometimes it’s hard to be sure you’ve actually weighed something.

Isotopic analysis is meaningless without laboratory standards of known isotopic value.

Weighing standards can be frustrating, though.

 

 

Ready to go!

 

The next phase will be making the mass spectrometer happy, and go through the analytical steps. This isn’t something I have tweets for, but I do have pictures. (Go me!)

The first part is to get the mass spectrometer linear. That means that it’ll give you the right isotopic value, no matter what gas pressure goes in. This is hard.

Please go linear, mass spectrometer!

Please go linear, mass spectrometer!

This involves turning the carbon dioxide regulator knob every 40 seconds for at least 20 minutes.

Carbon dioxide regulator knob.

Carbon dioxide regulator knob.

I usually get a little sword practice in while this is going on.

Sword practice in the laboratory. Fencing is serious business, but a dowel makes a good practice foil.

Sword practice in the laboratory. Fencing is serious business, but a dowel makes a good practice foil.

Once you’ve got the instrument running right, you can inject acid into your sample vials. The mass spectrometer can only measure gasses. Reacting carbonates and bioapatites with phosphoric acid causes carbon dioxide to be released, which can be measured.

Acid injected. The vials are flushed with helium prior to acid injection, so that atmospheric carbon dioxide doesn't screw up our analyses.

Acid injected. The vials are flushed with helium prior to acid injection, so that atmospheric carbon dioxide doesn’t screw up our analyses.

You’ve got to get the needle in the right place to insert into the vials.

Aiming the sample needle.

Aiming the sample needle.

Once you’ve got all that set up, then you can just hit the ‘start’ button on the computer that controls the mass spectrometer. Then go home and have an adult beverage. As it should be.

About Penny

Scientist (Paleontology, Geochemistry, Geology); Writer (Speculative and Science Fiction, plus technical and non-technical Science); Mom to great boy on the Autism spectrum; possessor of too many hobbies.
This entry was posted in Geochemistry, Research, Science, Stable Isotopes. Bookmark the permalink.

4 Responses to #RealTimeChem and Isotopic Analysis of Fossil Teeth

  1. Dave H says:

    So is each of those sample vials an overnight run? Or will the mass spectrometer step through and analyze all of them?

    I wonder if a powder trickler might make weighing out your chalk calibration samples easier.

    • Penny says:

      Good questions.

      Each vial takes about 15 minutes to analyze, so the whole set runs over night.

      The biggest problem with the standards is static, to be honest. Next comes getting the weights to be 200 micrograms plus/minus 20 micrograms. Once you get good, the weighing goes really quickly.

      The best way to make weighing anything easier is to pay a student to do it for you! ;)

  2. Dave H says:

    Students are probably the better solution. Powder tricklers are used to precisely measure gunpowder for loading into firearm cartridges. They’re usually static-free. Those that aren’t, well, they don’t last very long. (grin) “Precisely” in this case means to a tenth of a grain, which is about 6500 micrograms.

  3. Pingback: #Realtimechem Carnival Round up: Day 4 and 5 | The Organic Solution

Leave a Reply

Your email address will not be published.

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>