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QC - Bead Means

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ianfrank

Contributor

Posts: 29

Joined: Thu Nov 21, 2013 11:59 pm

Location: Tampa, FL

Post Tue Mar 11, 2014 5:32 pm

QC - Bead Means

Dear All,

I’ve noticed the means of my beads (DVS EQ 4 Element) slipping below the 1000 mark on the Eu151 axis. Everything else about the optimizing and QC looks really good. I have switched to the 4 element beads a few weeks ago, and I think they have a lower mean than the previous 2 element beads from DVS. Should I be concerned about getting the mean to be above 1000?

Ian
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mleipold

Guru

Posts: 5792

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Tue Mar 11, 2014 5:50 pm

Re: QC - Bead Means

Hi Ian,

Are you saying that only the Eu in the 4-element beads is changing (ie, Ce, Ho, and Lu are steady, but Eu is changing)?

Or are you saying that the Eu in the 4-element beads is lower than in the Eu-only beads?

From my time in Toronto, I know that there is some lot-to-lot (or batch-to-batch) variation in the lanthanide content in polystyrene bead synthesis. Therefore, if you are going to be using these for tracking performance, you should probably record which lot they came from.

Similarly, if you use the 4-element beads for data normalization, you'll want to make sure you aren't mixing bead lots in the same normalization. At least, not without checking the comparative signal intensities of the lots to confirm they're sufficiently similar.


Mike
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robs

Contributor

Posts: 40

Joined: Mon Dec 02, 2013 3:42 pm

Location: University of Connecticut

Post Wed Mar 12, 2014 2:17 pm

Re: QC - Bead Means

Hi Ian,

To follow up on Mike's first question, are the other elements in the 4-element stronger than the Eu? because they should roughly all have the same signal/MFI. If the signal is bad in all the bead channels but the tuning solution looks good, you could try adjusting your current or gases and see what effect they have on the bead ion clouds making it into the mass spec.

Do the tuning solution dual counts in the mid-range elements seem to have the same ratio as before (eg. Tb is twice as much as La) or does it seem to no longer favor the middle of the TOF range?

I ask because after an instrument tune up, we were actually getting higher terbium than thulium counts, which wasn't the case before. The adjustment to the ion focusing resulted in a slight change in the transmission efficiencies of each one.

Mike, something led me to believe that right now there is only one lot of the 4 element beads commercially available. Do you think that's true? Because if thats the case and Ian is getting good signals on the other elements but not Eu that would point to an instrument issue with transmission of that specific element.

Rob
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mleipold

Guru

Posts: 5792

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Wed Mar 12, 2014 3:30 pm

Re: QC - Bead Means

Hi Rob,

Based on my records, the HIMC has received at least 3 different 4-element bead lots in the time frame 9/19/13-3/5/14. The last two bottles (2/19/14 and 3/5/14) have been from the same lot, so maybe DVS has scaled up.

Regarding Tb and Tm: in my experience, it can be a bit arbitrary which is the highest intensity signal (note: I'm talking about pulses-count mode, since we're still using that version of software). Generally speaking, between cleanings, one of them is consistently on top. However, after cleanings (and XY realignment, etc), occasionally it will switch. In most cases, if you run tuning solution for a super-long time, the two will eventually wind up overlapping (they're at the same concentration, and have close to the same "brightness", at least for CyTOFv1). For the purposes of calculating the <3% ratio, it doesn't matter which one is on top.

Based on observation, I think that Tb has a slightly higher affinity for the plastic tubing and such than Tm does. This is why at first (or on the first injection of tuning solution), Tm can be on top and then with more injections/runtime, they start to merge as the system equilibrates (stops artificially depleting the Tb). Similarly, when you then use Wash solution to remove residual Tuning solution, the Tb signal stays higher for longer.


Mike
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robs

Contributor

Posts: 40

Joined: Mon Dec 02, 2013 3:42 pm

Location: University of Connecticut

Post Wed Mar 12, 2014 3:48 pm

Re: QC - Bead Means

That makes sense, Mike, I think metal loss in the introduction was definitely part of it.
The theory about the scaling up is most likely the case because we only got the 4-element beads once they were commercially available a couple months ago and like you both our new bottles are the same lot. In the v6.0.626 software you can choose the lot to use for normalization and it only lists one which must be the one they put into wide production.
Rob
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mleipold

Guru

Posts: 5792

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Wed Mar 12, 2014 5:30 pm

Re: QC - Bead Means

Tb and Tm appear to be the main Ln in the Tuning solution that have affinity for the plastic tubing/etc. You tend to see a greater increase with them on a second injection than you do La or Cs.

We always run Wash solution during warm-up and then rinse with water back down to background levels. Even so, it's fairly common for us to start the Tuning solution, see the tuning solution metals start to go up, and then see the Tb and Tm signals plateau briefly while Cs and La continue to increase smoothly and getting a short spike in Ir191/193. The Tm and Tb start to increase again as the Ir191/193 starts to go down again.

Since they're correlated in time, we attribute this to the Tuning solution Tm/Tb "kicking off" Ir from the tubing/etc, and as further evidence about the equilibration that happens early on in tuning solution injections.

However, since Current and Makeup Gas optimization for the day is largely independent of the absolute signal intensity, we go ahead and tune those parameters. Then do a second injection to check the Tb gain/DetVolt setting and then get a final reading on signal intensities and oxidation levels.


Mike
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ianfrank

Contributor

Posts: 29

Joined: Thu Nov 21, 2013 11:59 pm

Location: Tampa, FL

Post Fri Mar 14, 2014 6:22 pm

Re: QC - Bead Means

Dear All,

Thanks for the responses. After some troubleshooting, DVS seems to think that the problem is with the 4 Element QC beads that I was using. The drift below 1000 is due to the beads. It's a very early lot. In fact I think it was a beta test lot. (Although the bottle doesn't say it's beta.) Anyhow they've assured me that the problem with instability was fixed a long time ago. So I just need to dispose of the old lot and start with a new one. They still are insistent that the mean of the beads in the 153Eu channel should be above 1000 in order to pass QC. If anyone has an opinion on the stability of non-beta 4 Element QC beads, I would like to hear it.

Ian

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