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Barium contamination - how does it normally show up?

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rgrenfell

Contributor

Posts: 30

Joined: Thu Aug 27, 2015 12:31 pm

Post Fri Oct 07, 2016 9:56 am

Barium contamination - how does it normally show up?

Hi everyone

We’ve just run some samples that showed a high signal in the Ba138 channel.
We’ve not see it before & detergent/glasswash would be my first idea. I might expect the signal to be relatively continuous while running, but this did seem to be very much associated with the cell rather than spread throughout (like the Pb)

Would a conventional Ba138 contamination show up as cell specific rather than in solution or should I be looking at some contamination of the cells (before analysis)

Thanks

Richard
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mleipold

Guru

Posts: 5796

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Fri Oct 07, 2016 3:29 pm

Re: Barium contamination - how does it normally show up?

Hi Richard,

Ba contamination (easiest to see as the major Ba138 isotope just on the edge of the Xe area) is often cell-associated, in my experience. I think in many cases this comes from the cells having "seen" Ba-containing buffers and such, perhaps even during initial processing (eg, during PBMC processing and such). Even if you switch to Ba-free buffers after, you might not be able to get rid of all of it.

Here's a recent example:
100616-Lyobead sample-end of sample.jpg


Not too bad....I've certainly seen far worse. But you can see some additional Ba associated with the cell, particularly in the bottom cell event (relative to the background, non-cell-event level).

Unfortunately, I don't know of any way to retroactively get rid of initial Ba contamination. As far as I can tell, it just keeps diffusing out with each wash. Therefore, you can *decrease* it, but not completely remove it....similar to Iodine levels sometimes seen in PBMCs from the Ficoll-Paque step (usually highest on Monocytes, in my experience).


In short, though, I don't know how much difference it makes: we don't us the 138 channel (or any other Ba isotope channel) for any reagent. And as long as your level is comparatively low, you don't have to worry about M+16 spillover into the 154 channel.....as long as you're monitoring Ba138, you can detect any potential problem.


Mike
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Chowduck

Contributor

Posts: 29

Joined: Wed Nov 19, 2014 4:39 pm

Post Fri Oct 07, 2016 9:04 pm

Re: Barium contamination - how does it normally show up?

Hi Richard,

We have noticed Ba138 contamination in a sample specific manner. In our case it turns out it was coming from the food our mice were eating. Attached is a screen cap of the mouse food crushed, dissolved in 2% nitric acid, filtered and diluted in water. I’m not certain why this contamination varies between animal samples; we haven’t looked into it further.

LAS food.jpg


-Greg
UHN/Sickkids FCF
Toronto, Canada
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OLIVIASP

Participant

Posts: 6

Joined: Fri Jun 17, 2016 9:04 am

Post Tue Oct 11, 2016 6:39 am

Re: Barium contamination - how does it normally show up?

Hi Richards,

We found the same problema with run our samples, they showed a high signal in Ba, Pb and Ce. We discover that it came from hand made PBS, from one of the components, we think it came from monosodium phosphate. We have changed to commercial PBS, and the problem dissapeared.

We are very young in mass cytometry, we have Cytof2 upgrade to Helios and have not a lot of experience, but I hope we help you.

Best,
Olivia

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