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Ba138 contamination

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Ofir

Master

Posts: 75

Joined: Thu Nov 07, 2013 12:46 pm

Location: US, CA

Post Tue Jan 21, 2014 8:36 pm

Ba138 contamination

Hi all,
We just finished running samples from one of our users and found out that there was a non-negligible amount of (environmental) Ba138 in the sample. :cry:
I am worried that oxidation of Ba138 will cause signal in Sm154 where we have an antibody for CD11c (can be a rare population in our experiments and therefore sensitive to false positives).
I can't seem to find the data for % oxides for Ba138. Does anyone have any data on this?

Thanks!
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robs

Contributor

Posts: 40

Joined: Mon Dec 02, 2013 3:42 pm

Location: University of Connecticut

Post Thu Jan 23, 2014 3:11 pm

Re: Ba138 contamination

Hi Ofir,
We do see a small signal boost in our 154 channel with samples with high Barium. I ran some Barium-high media in free metal mode and left the 138 and 154 channels open. For one media the oxide was 0.2% of the 138 channel, for another it was 0.12%.
So it seems small, but obviously that would depend on the instrument and the torch temperature/gas flow.
I guess if you had extra cells you could run cells without the 154- 11C Antibody and observe the background, or you could digest some unlabelled cells in HCl and run them in free metal mode, leaving the 138 and 154 channels open.
-Rob
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mleipold

Guru

Posts: 5796

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Thu Jan 23, 2014 4:30 pm

Re: Ba138 contamination

Hi Ofir,

First of all, tell your user to throw out all his/her buffers, then remake them in bottles that have never been through laboratory dishwash, and have never seen soap. Preferable brand-new bottles (glass or plastic). And don't forget, this goes for the water that you use to make the buffers too.

Second: La is more easily oxidized than Ba. Therefore, if you're controlling the La139+O16 signal=155 signal, then you're automatically controlling all the others. But the only way to control Ba levels is to make sure that the cells never "see" Ba.


In terms of cleaning your machine: 3% nitric acid does a better job of removing it than Wash Solution (HF; 0.05%, I think) does. This also works better for Cd from Qdots, or Pt, Pd, or Ag.


Mike
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Ofir

Master

Posts: 75

Joined: Thu Nov 07, 2013 12:46 pm

Location: US, CA

Post Thu Jan 23, 2014 5:41 pm

Re: Ba138 contamination

Thanks Mike!
Some users are not as appreciative of the sensitivity of the CyTOF as we'd like. I now have data to demonstrate the issue.
Regardless, do you happen to have the data on %oxides for Ba? I'd like to better control my contaminated channel.
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mleipold

Guru

Posts: 5796

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Thu Jan 23, 2014 11:18 pm

Re: Ba138 contamination

Hi Ofir,

I don't have data on that.

However, if you take cells, label them with Ir, and then wash them with water from a dishwashed-bottle a couple times, you should load them with Ba. Then just monitor the Ir channels, Ba138, and 154.


I would recommend doing that, or Rob's metal-minus-one experiment. You won't have spillover into 154(Sm) from 153(Eu) or 155(Gd).

The digestion in HCl or HNO3 is another option, but we've seen some slight differences in contamination/spillovers when run in free metal/liquid mode vs cell mode. This is primarily when looking at antibodies, comparing the impurities in the metal salt stock solution with data from a Kappa-capture-bead experiment with a labeled antibody form that stock. I'm almost positive the metal is present in excess, and while the "good" metal and the "bad" metal *should* enter the polymer chelators at the same ratio with which they're present in solution, I wonder if there's some slight statistical effect in the loading of the polymer when [binding site] << [metal].

That, or we're just under the detection limit for some of the impurities in the antibody-bead experiment.


Mike

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