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CyTOF2 warmup time

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AdeebR

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Location: NYC

Post Tue Apr 08, 2014 11:09 pm

CyTOF2 warmup time

For those of you running a CyTOF2, how long does it take after you turn on the plasma before you get steady maximal tuning signals?

The manual indicates a plasma warmup time of 15-30mins, but I suspect that our instrument is taking much longer (1-2hrs).
Adeeb Rahman
Icahn School of Medicine at Mount Sinai, NYC
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bjcarter

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Post Fri Apr 18, 2014 6:01 pm

Re: CyTOF2 warmup time

I usually let the plasma warm for at least an hour before tuning. Like you, I've found that 15-30 minutes isn't sufficient and I've seen upwards of a 30% increase in Dual Mean values with the extra 30 minutes warm-up time. Definitely allow for extra time as able. All other QC values seem steady without the extended warmup time. -brandon
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bertran

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Post Tue Apr 22, 2014 11:57 am

Re: CyTOF2 warmup time

Providing you have stable Argon flow(s), it seems unlikely that a plasma needs to "warm up". To me this points much more towards a detector HV warm up time and perhaps instability. Well worth raising this issue with the folks of DVS Fluidgm.

\bertran
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mleipold

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Post Tue Apr 22, 2014 3:00 pm

Re: CyTOF2 warmup time

There definitely is a warm-up time needed with the detector and other internal electronic components.

There is also probably a plasma stability issue.

However, if you monitor oxide ratio, the oxide signal typically *does* go down over the warm-up period, even if you don't wind up changing Current, Makeup Gas, or Detector Voltage. This might only be going from, say, 4-5% down to 2-3% oxide, but does occur. And this is separate from any equilibration that usually happens between the tuning solution solution-phase ions and the ions adsorbed to the tubing.
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Ofir

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Post Tue Apr 22, 2014 3:48 pm

Re: CyTOF2 warmup time

So Mike, does that mean that the ICP itself changes over time or that other components are heated by the plasma and related optics?
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mleipold

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Post Tue Apr 22, 2014 3:56 pm

Re: CyTOF2 warmup time

It is known that the TOF is affected by temperature. This is one reason why there's a decrease in signal intensity over very long (6hr+ or so) runtimes: a given ion shifts to higher TOF, which starts moving it out of the TOF acquisition (start+integration time) window for that mass. If you adjust your TOF (Cs133 and Ir193 in mass Calibration window, at least on CyTOFv1) periodically, you can slow down the intensity decline.

I honestly don't know, regarding the thermal equilibration of other components, from glassware through cones and quadrupole.
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Ofir

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Post Tue Apr 22, 2014 5:38 pm

Re: CyTOF2 warmup time

Thanks. How does that relate to change in oxide levels though?
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mleipold

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Post Tue Apr 22, 2014 6:27 pm

Re: CyTOF2 warmup time

As I said earlier, it's been my experience that the oxide ratio goes down over 15-20min warmup, as the plasma stabilizes and/or gets fully hot. The hotter the plasma, the lower the oxide amount.

After that 20min or so, the oxide ratio doesn't usually change for the rest of the time it's on.


If you were asking whether the oxide mass is properly detected over time, then yes....its mass behaves just like any other mass in terms of the ion peak shifting to higher TOF over long runtimes as the TOF machinery itself is affected by temperature.
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anitamkant

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Post Wed Apr 23, 2014 1:20 am

Re: CyTOF2 warmup time

For ICP-MS a warm up time of 30 min is considered sufficient. When the plasma is ignited vacuum interface heats up and the cones actually change size as well as the gas- dynamics changes affecting the ion transport conditions. The warm-up time allows equilibration of the bulk of the interface chamber so that the thermal transport to the coolant channel stabilizes. Basically, allows time for the interface block and chamber temperature to stabilize. Any surface condensed materials (water, salts) that have accumulated during the off-period are also desorbed in this warm-up period.
Detector warm up (if needed at all) does not contribute to the long periods mentioned here.
How clean are the cones?

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