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low end noise

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lisanichols

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Posts: 5

Joined: Mon Apr 24, 2017 9:40 pm

Post Tue Mar 06, 2018 8:38 pm

low end noise

Just had our detector replaced and we are seeing a lot of low end noise...it's below where signals from samples should be detected, but definitely abnormal. No other changes to materials or reagents since the detector change. This is how it looked after the conditioning. Perhaps unrelated, the bead signals are also quite high compared to their usual values. Any ideas on what this contaminant could be? Any help appreciated - thanks, Lisa
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mleipold

Guru

Posts: 5796

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Tue Mar 06, 2018 8:42 pm

Re: low end noise

Hi Lisa,

Do you have some before/after data? It doesn't look like it attached, if you tried in your initial post.


Mike
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lisanichols

Participant

Posts: 5

Joined: Mon Apr 24, 2017 9:40 pm

Post Tue Mar 06, 2018 8:48 pm

Re: low end noise

I don't think my upload went through. Let me try again....
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lisanichols

Participant

Posts: 5

Joined: Mon Apr 24, 2017 9:40 pm

Post Tue Mar 06, 2018 8:52 pm

Re: low end noise

View of streaking attached.
Attachments
cropped rainplot.jpg
Just above argon dimer
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mleipold

Guru

Posts: 5796

Joined: Fri Nov 01, 2013 5:30 pm

Location: Stanford HIMC, CA, USA

Post Tue Mar 06, 2018 9:08 pm

Re: low end noise

HI Lisa,

It looks like really bright Argon Dimer to me.

If you run in Tuning mode to see the rainbow plot of Signal vs Time for the various Tuning isotopes, does it give Ar dimer signal as much higher than normal?


If so, and your Beads are really brighter than normal, it seems like your Detector Voltage might be turned up too high. What was the last DV before the detector change, and what is your new (current) DV value?


Mike
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lisanichols

Participant

Posts: 5

Joined: Mon Apr 24, 2017 9:40 pm

Post Tue Mar 06, 2018 9:37 pm

Re: low end noise

Well, I suppose that would be a good thing if it's just that the detector was set way too high...hadn't considered that. The data was from the first tuning after they replaced the detector and did the 'conditioning' to get the detector set at the correct stable voltage. Sounds like we need to get back in touch with the FSE and have them re-evaluate how the conditioning was done. It would explain the brightness of the beads as well...figured that had to be 'too good to be true'.
Thanks for the feedback!
Lisa
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lisanichols

Participant

Posts: 5

Joined: Mon Apr 24, 2017 9:40 pm

Post Tue Mar 06, 2018 9:46 pm

Re: low end noise

Just verified voltages - pre-detector they were around -1115; currently at -2030

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