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Compressed Argon Gas Contamination

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mleipold

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Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Mon Oct 08, 2018 8:59 pm

Re: Compressed Argon Gas Contamination

Hi Takuya,

When Stanford had the high Xe issue, Praxair supplies were affected but Airgas supplies were not.

Therefore, depending on gas supply arrangements in your area (sometimes one supplier may work with another one, at least on specialty gases), switching suppliers may work. Unfortunately, the only way to find out is to try.


Mike
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EHaasDFCI

Contributor

Posts: 24

Joined: Thu Jun 15, 2017 5:34 pm

Post Tue Oct 09, 2018 5:28 pm

Re: Compressed Argon Gas Contamination

takuya wrote:Hi all,

We, at the University of Pennsylvanian, are seeing very high Xenon in Argon gas these days too. Multiple tanks from Airgas. We are considering purchasing higher grade gas, or switching supplier. The problem is higher grade gas cost $100 more per 160L tank, which is not a small cost increase. But according to the posts here, changing supplier does not solve the problem unless they fill only from the top of the bulk tank? Any suppliers guarantee the quality of their product at the consumer level?

Thank you,
Takuya


This is very interesting as we too use Airgas and have had the exact same experience. Historically the tanks have been great, but the last 4 or so have had too much Xenon (to answer your question Mike). I wonder if there is something going on with the supply on the east coast.

Has anyone else that uses Airgas on the east coast/northeast seen an uptick in Xenon lately?
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mleipold

Guru

Posts: 2095

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Tue Oct 09, 2018 5:48 pm

Re: Compressed Argon Gas Contamination

Hi Takuya and Eric,

Back when this happened to us, I did calculations on whether Praxair could even give a spec on Xe levels. From what I was told, they mainly use GC, with a LOD around 1ppm.

Calculations I sent to Praxair are below:

-------------------
"I *can* give [Praxair] an estimate on the regular Xe signal. During the Tuning process, we do measure the Xe131 signal. Then, by comparing that signal to the closest Tuning Solution isotopes, we can get at least a rough number.

----If Cs133 and La139 are 0.5ppb, then on a recent good Xe tuning:
Xe131 (21.18% of total Xe) is a Dual of 60,822 --> 287,167 @ 100% Xe
La139 (99.91% of total La) is a Dual of 898,504 --> 899,313 @ 100% La
Cs133 (100% total Cs) is a Dual of 1,023,182 --> 1,023,182 @ 100% Cs

Therefore, if total Cs and total La are each at 0.5ppb, then total Xe would be at approximately 0.15ppb in a regular tank.

From above: the Xe131 has a software QC limit of ~400,000 Counts, which is about 6x what I measured on the "good" tank. If so, then total Xe to allow pass of Tuning would be roughly (0.15ppb x 6 =) ~0.9ppb. Since labs are failing tuning and based on the Xe comparison I attached, I'd say we're well above that on the "bad" tank.

One thing I didn't think about until last week was whether Xe was being fully ionized in the Ar plasma. From looking up the first ionization energy of Xe compared to Ar, it seemed likely that (unlike Cs or the other Ln metals), Xe would *not* be fully ionized.

So, I asked Fluidigm, and they confirmed that Xe is only ~10% ionized in an Ar plasma. Therefore, we should multiply my previous numbers of a factor of 10. As such, ~1.5ppb for "good", >10ppb for these "bad" tanks would be the "new" values.

From what [Praxair] told me about the detection limit of [their] GC (usually ~1ppm), we're still ~100x below that for our max allowable.
---------------------


Mike


So, there's still a question whether they can even really *measure* down to the levels that we need it........and therefore, it's not clear whether they can even write a spec for it....'
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GregHopkins

Participant

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Joined: Tue Apr 11, 2017 8:39 pm

Post Fri Jun 07, 2019 7:07 pm

Re: Compressed Argon Gas Contamination

We are having this problem persistently over the past few weeks now. Our Argon supplier is local (Middlesex Gases in Massachusetts), but don't know where they get their main supply from or if others are starting to experience high Xenon levels in their tanks recently in the Boston area. I've tried giving the tanks time to let the Xenon purge, but to little avail. Is there anything I can do to get the Xenon levels down to a usable point? I"m running tunes and they are passing with flying colors on all accounts other than the Dual Counts of Xe, which are causing consistent failure.

Greg H
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mleipold

Guru

Posts: 2095

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Fri Jun 07, 2019 7:55 pm

Re: Compressed Argon Gas Contamination

Hi Greg,

Xe will only get worse as you go down in the liquid tank. Therefore, if you have a Xe-bad tank, it will be Xe-bad for the entire tank....there's nothing you can do to remove/vent Xe.

So, you have a few options:
1. Return the tank, and run off something else until you get a good tank (since they can stockpile them, sometimes cylinders are OK even when the liquid tanks aren't).
- advantage: not blasting your instrument with Xe
- disadvantage: time, money, inconvenience of changing cylinders

2. Go into Service Mode and uncheck Xe upper limit as part of the testing, so it won't cause failure of the QC report.
- advantage: easy fix
- disadvantage: still blasting your detector with Xe, not recommended by Fluidigm
- also, if particularly bad, potential Miscalibration if the Mass Calibration locks onto Xe132 or Xe134 rather than Cs133. Though, you can tighten the M1 search "window" in service mode to avoid that.


Mike
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twightman

Participant

Posts: 17

Joined: Thu Oct 23, 2014 5:49 pm

Post Mon Nov 11, 2019 3:59 pm

Re: Compressed Argon Gas Contamination

EHaasDFCI wrote:
takuya wrote:Hi all,

We, at the University of Pennsylvanian, are seeing very high Xenon in Argon gas these days too. Multiple tanks from Airgas. We are considering purchasing higher grade gas, or switching supplier. The problem is higher grade gas cost $100 more per 160L tank, which is not a small cost increase. But according to the posts here, changing supplier does not solve the problem unless they fill only from the top of the bulk tank? Any suppliers guarantee the quality of their product at the consumer level?

Thank you,
Takuya


This is very interesting as we too use Airgas and have had the exact same experience. Historically the tanks have been great, but the last 4 or so have had too much Xenon (to answer your question Mike). I wonder if there is something going on with the supply on the east coast.

Has anyone else that uses Airgas on the east coast/northeast seen an uptick in Xenon lately?


In Rochester we're in the middle of a mess of bad Argon tanks from Airgas. Is anyone else having these issues again here in the Northeast? We've tried 2 standard liquid dewars, 2 high purity, 1 cylinder and just today another high purity liquid dewar that we were told was from a different source tank, but they're all really bad.

We're hoping to try a liquid dewar from Praxair soon, but this is getting rediculous. Are we alone now or is this happening all over? Does it have something to do with the season since it seems this happened last year around this time?
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mleipold

Guru

Posts: 2095

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Mon Nov 11, 2019 4:32 pm

Re: Compressed Argon Gas Contamination

Hi Terry,

I don't think it has anything to do with the time of year, exactly. Air is air, regardless of season (so, not like getting a tasteless melon out of season).

The Bay Area often has issues with Praxair in the April time-frame: I think there's yearly (or twice-yearly) maintenance that goes on around that time. That shuts down their Pittsburg CA extraction plant for a couple days, and if they run low, they bring extra in by rail car from other parts of the country. Unfortunately for us, the Texas plants appear to be their main resupplier and always run high on Xe.

Praxair's ICP-grade supply is a completely separate extraction unit, so even when the industrial tank (which supplies both industrial liquid argon and high-purity compressed gas) gets "poisoned" with Xe, the ICP-grade is usually fine. Unfortunately, once in a while, they mess up and empty into that supply too. In that case, it's Praxair's fault, and they have to deal with emptying and reventing liquid dewars and the main supply tank until they get rid of it (since that has specs on Krypton and regular industrial-grade won't pass that). Otherwise, technically Praxair has no specs on Xe levels in Argon.


Mike
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twightman

Participant

Posts: 17

Joined: Thu Oct 23, 2014 5:49 pm

Post Mon Nov 11, 2019 5:20 pm

Re: Compressed Argon Gas Contamination

mleipold wrote:Hi Terry,

I don't think it has anything to do with the time of year, exactly. Air is air, regardless of season (so, not like getting a tasteless melon out of season).

The Bay Area often has issues with Praxair in the April time-frame: I think there's yearly (or twice-yearly) maintenance that goes on around that time. That shuts down their Pittsburg CA extraction plant for a couple days, and if they run low, they bring extra in by rail car from other parts of the country. Unfortunately for us, the Texas plants appear to be their main resupplier and always run high on Xe.

Praxair's ICP-grade supply is a completely separate extraction unit, so even when the industrial tank (which supplies both industrial liquid argon and high-purity compressed gas) gets "poisoned" with Xe, the ICP-grade is usually fine. Unfortunately, once in a while, they mess up and empty into that supply too. In that case, it's Praxair's fault, and they have to deal with emptying and reventing liquid dewars and the main supply tank until they get rid of it (since that has specs on Krypton and regular industrial-grade won't pass that). Otherwise, technically Praxair has no specs on Xe levels in Argon.


Mike



Thank you so much Mike! Do you have any idea if the Xe stays in the lines at all? We have never had this issue before and unsure how it will look if we do get a good tank in. I'm assuming it's air so it shouldn't stay in the lines but I guess I could be wrong.
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mleipold

Guru

Posts: 2095

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Mon Nov 11, 2019 5:37 pm

Re: Compressed Argon Gas Contamination

Hi Terry,

It doesn't persist in the lines (unlike, say, Barium or Iodine in the tubing): once you get a good tank, the Xe problem will go away immediately.


Mike
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Diane1

Participant

Posts: 7

Joined: Thu Jun 08, 2017 9:55 pm

Post Mon Nov 11, 2019 7:21 pm

Re: Compressed Argon Gas Contamination

Hi All,
We have had a lot of problems with Argon from Praxair in September and October. We were ordering the ICP grade liquid and also gas cylinders. Everything was contaminated with xenon. We finally had a liquid Dewar that was doing great, low Xenon, when at about 50% Argon left in the tank, plasma would not start. I went through all the trouble shooting issues to no avail. Finally, plasma started and that user got his samples done. Xenon dual counts were not bad at about 150,000. Several days later, we experienced the same problem. We could never get plasma to start. We tried a new cylinder we had and it still did not start. Fluidigm tech was able to come by the second day of our problem and diagnosed that Xenon was high. It was now showing over 800,00 dual counts!

The reason why the cylinder would not work for us was because there was still Xenon in the lines. Fluidigm showed us how to purge the lines to remove the previous gas with xenon. There is a small release switch near the pressure valve on the right hand side of the machine.

The whole experience was frustrating because in the past plasma always started when we had high xenon (tuning would fail). So, when we switched to the cylinder and it still did not start, we still did not think it was Xenon. We were down for 2 days with this problem.

Hope this helps others out there!
Diane
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