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How many atoms escape?

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rgrenfell

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Posts: 12

Joined: Thu Aug 27, 2015 12:31 pm

Post Tue Mar 03, 2020 3:08 pm

How many atoms escape?

Hi everyone
I'm trying to get a feeling for how many metal atoms escape up the exhaust chimney (or get stuck somewhere other than the detector)

I dont really have an idea of if it's something close to 100% of the measureable atoms, that make it to the detector, or if its closer to 1%

and if its closer to 1%, would the expectation be that most of the 99% end up going up the chimney, or stuck to surfaces inside the instrument.

Anyone got an insight as to whats going on in there?

Thanks

Richard

ps, not really trying to count atoms, just trying to work out the proportion of sample atoms left behind
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mleipold

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Posts: 2086

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Tue Mar 03, 2020 3:52 pm

Re: How many atoms escape?

Hi Richard,

This isn't a straightforward question.

Ion transmission efficiency is "how many ions do I put in" vs "how many ions do I get measured". From thr Tricot et al 2015 paper (and similar tests afterwards that I and other people have done), this is on the order of 1/10,000 (1e-4) for CyTOF1 and CyTOF2, and on the order of 1/5000 (2e-4) for Helios instruments, though individual instruments vary.

But, that doesn't fully address your question of "if I *don't* get a measurement for an atom, where did it actually *go* rather than the detector?" Some of the atoms wind up on the cones (the "soot" and other black buildup). Some of the atoms wind up in the interface pump oil. Some of the atoms don't make the turn to the quadrupole. And some ions don't make it through the quadrupole.

Maybe Fluidigm (or some other mass spec person) will chime in with numbers for each step along the way.


Mike
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rgrenfell

Participant

Posts: 12

Joined: Thu Aug 27, 2015 12:31 pm

Post Wed Mar 04, 2020 2:54 pm

Re: How many atoms escape?

Thanks Mike

I've sent a request to Fluidigm

For a bit of context, we have some samples with a radioactive isotope in the cells. Its a fairly short half life, and we are talking about low amounts, but envrionmentally, we are allowed no gaseous radioactive release from the building.
The follow up question would be, if it doesnt get out of the building, where does it end up?

My hunch is that pretty much nothing gets out of the instrument, but it would be good to have some more concrete confirmation from Fludidigm

Richard
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mleipold

Guru

Posts: 2086

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Wed Mar 04, 2020 4:00 pm

Re: How many atoms escape?

Hi Richard,

Is this radioactive isotope one that you're trying to measure by CyTOF (eg 89Zr, or 111In), or is it incidental (present in the sample, but not something you're trying to measure)?

The reason I ask, I've been asked before whether 89Zr (PET tracer) is something that could be measured by CyTOF. Based on the calculations at the time (amount of 89Zr + ion transmission efficiency), it didn't seem like it would be detectable by CyTOF.


Is there a possibility for you to stain the cells, then freeze them for 5-8 half-lives before you run them? That way, there shouldn't be any detectable radiation *to* release.....


Mike
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rgrenfell

Participant

Posts: 12

Joined: Thu Aug 27, 2015 12:31 pm

Post Wed Mar 04, 2020 4:24 pm

Re: How many atoms escape?

Hi Mike

It's the indium111 we're looking for. The samples will have been left long enough to decay to the point where they wouldnt need any consideration.
That seemed ok to us.
The problem now is that there is some indium114 contamination in there, with a much longer half life.

We're looking to show that the indium labelling doesnt affect the staining profile of the sample (that we have been running (unlabelled with indium) for a while)

Thanks
Richard
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mleipold

Guru

Posts: 2086

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Wed Mar 04, 2020 4:42 pm

Re: How many atoms escape?

Hi Richard,

Interesting. Are these samples labeled by you in vitro as an Indium-containing probe, or is the indium treatment coming during patient treatment?

Is 114In a common contaminant in 111In preps? If so, how do doctors deal with that isotope's excretion when dosing their patients with 111In treatments? According to Wikipedia, 114m1-In has a half-life of ~50 days; it's not likely anyone would be willing or able to stay in a hospital for about a year to make sure all the 114m1-In radioactivity is......collected.

In other words, how much are you using relative to standard medical treatment, and could you use medical guidelines as a metric for release potential?


Mike

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