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Samarium contamination from PFA?

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Ofir

Master

Posts: 75

Joined: Thu Nov 07, 2013 12:46 pm

Location: US, CA

Post Fri May 23, 2014 12:13 pm

Samarium contamination from PFA?

Hey CyTOFers,
In the CyTOF user meeting (during the CYTO pre-conference) a couple of labs noted that they see Samarium contamination that they were able to trace back to their PFA from EMS. Reportedly there is batch to batch variation, and some batches are just fine.
I have not seen this phenomenon in our experiments, but I was not looking for it really...

I was wondering how widespread this phenomenon really is. Please post a quick note if you have seen this with your PFA.

Thanks!
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mleipold

Guru

Posts: 2256

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Fri May 23, 2014 2:50 pm

Re: Samarium contamination from PFA?

Hi Ofir,

We have not seen any issue at the HIMC, for PFA from EMS.

However, I remember about 12-18 months ago, the Nolan lab had 2 lots of PFA that were contaminated with some kind of particulates. I believe they were Gadolinium and something else. They noticed ultra-bright signal intensity that hadn't been seen before, particularly in lineages that should have been negative for those metal-antibodies.

To my knowledge, this has not recurred for them.


Mike
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ErinSimonds

Contributor

Posts: 49

Joined: Tue May 13, 2014 8:04 pm

Post Fri May 23, 2014 9:49 pm

Re: Samarium contamination from PFA?

Mike is right about the Nolan lab's experience -- we found samarium in 2 lots of the PFA from EMS. This led to a search for alternative PFA from other vendors and several conversations with EMS, the upshot of which was actually that EMS prepares the PFA for several other vendors. Since it turned out to be a lot-to-lot issue, and quite rare overall, we now simply test each new lot.

Interestingly, it was not simply ionic samarium in solution, it was actual chunks of precipitated samarium. These showed up as cell-like "events" on the CyTOF, rather than simply a constant background of metal in solution. We never figured out why there were chunks samarium in the PFA, but I love the BIC lighter theory. That could very well be it. Our best guess at the time was that it came from a magnetic stir bar.

The artifactual events tended to be iridium-negative and they had the isotopic abundance profile of naturally-occurring samarium:

144: 3.1%
147: 15.1%
148: 11.3%
149: 13.9%
150: 7.4%
152: 26.6%
154: 22.6%

It's easy enough to test each new lot of PFA and make sure this isn't an issue. It's good practice to test each new reagent you bring into your CyTOF workflow by either checking them in solution-mode, or running some unstained cells in each experiment to check for background.

- Erin
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mleipold

Guru

Posts: 2256

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Fri May 23, 2014 10:10 pm

Re: Samarium contamination from PFA?

I do know that there are lanthanides in certain lab items.

When I was at University of Toronto, we found that striker flints for bunsen burners had super-high levels of certain lanthanides:

http://en.wikipedia.org/wiki/Ferrocerium#Composition

Not only was it a problem when someone was doing ICP-MS/CyTOF work while someone was igniting the Bunsen burner for bacteria work or pulling TLC capillaries, but that meant it also got into the dust in the lab. We had to make sure to keep the Bunsen burner areas super-clean, and make sure that anyone doing lanthanide work in a lab with a burner would cover their samples whenever someone was lighting up.


I'm not saying EMS uses Bunsen burners, but.....weird things can happen, and when they happen rarely and randomly, are a pain to troubleshoot or track down.
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AdeebR

Grand master

Posts: 169

Joined: Thu Mar 13, 2014 5:58 pm

Location: NYC

Post Sat Dec 13, 2014 2:14 am

Re: Samarium contamination from PFA?

Just wanted to update this to note that I've now also found samarium (and praseodymium) contamination in my samples that I've tracked back to the EMS 16% formaldehyde ampules. In my case, it wasn't chunks of precipitated samarium as Erin described, but cells that were incubated in 1.6% formaldehyde showed high levels of samarium background (at natural isotope abundance staining intensities) and also very high background contamination of Pr-141. I've attached a pdf to show what this looks like (whole lysed blood sample incubated in either PBS or PBS+1.6% formaldehyde from two different lots).

I should also note that I've been using the same box/lot (131007) of formaldehyde for a few months now, and this wasn't as much of a problem with previous ampules in the box, which suggests that there can be variation within a given box/lot (though I popped open the last four ampules in the box to test and found that were all pretty uniformly contaminated). An ampule from a different lot that I tested at the same time was fine.

I spoke to EMS and of course they denied any possibility that such contamination could have originated in their facility.
Attachments
141212_background.pdf
(714.78 KiB) Downloaded 357 times
Adeeb Rahman
Icahn School of Medicine at Mount Sinai, NYC
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komalkumaralienboy

Contributor

Posts: 44

Joined: Tue May 20, 2014 2:24 pm

Location: Linkoping University, Sweden and Finnish Institute of Molecular Medicine, Finalnd

Post Mon Dec 15, 2014 9:22 am

Re: Samarium contamination from PFA?

Hi,

Before i do have some concern about Samarium contamination in PFA, decided to test contamination for Samarium in PFA (lot no131007)
sample1 with CD45Sm +PFA and sample 2 without CD45Sm and PFA. It looks like there is no considerable signal for samarium in sample2, i could say very low signal and negative. But there was high background signal for Pr141, Ta181.
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ErinSimonds

Contributor

Posts: 49

Joined: Tue May 13, 2014 8:04 pm

Post Mon Dec 15, 2014 9:29 pm

Re: Samarium contamination from PFA?

@Adeeb: I've started to wonder if the contamination is actually from the brown glass in the ampules themselves. I always get a bit of fine powder when I crack open the vial, which could generate the particles I saw. We have been able to get rid of the particles with a 0.1 um filter. But if it's in solution as you say, that won't help. Did you ever try filtering the "bad PFA"?

- Erin
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mleipold

Guru

Posts: 2256

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Mon Dec 15, 2014 10:02 pm

Re: Samarium contamination from PFA?

Hi Erin and Adeeb,

From what I was able to find just now about amber glass, its color comes from iron oxides and sulfides.

For example:

http://www.gerresheimer.com/uploads/med ... Gx51-L.pdf

http://www.gpi.org/learn-about-glass/wh ... lorization


That's not to say there couldn't still be some samarium (or other) contamination in there, just that Sm isn't explicitly mentioned in the formulations for the glass itself.

I think Erin's idea of taking a "known bad" lot of PFA, filtering it, and trying it again is a great plan....it would at least tell you whether most of it is physically removable (which, in a practical sense, is one of the most important things).


Mike

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