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Topic: Instrument drift  (Read 2539 times)

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Offline austanius

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Instrument drift
« on: December 13, 2016, 02:51:30 PM »
I use a chemilulecence analyzer that measures nitorgen but it has no units/not calibrated. So I use standards of known concentrations before and after to create a linear line to plug my measurements in. Problem is the instrument gradually changes over time(let's assume linearly) so my standards have different measurements than the beginning. I want to create one standard curve that I could use that would adjust to the instrument change over time. Let's say the fist set of standards has a slope of y=2x and at the end it's y=3x and it took 2 hours. I have a time stamp of when each sample went in as well. What would be the value for a measurement of let's say 30, 45 minutes into my run? I can almost visualize how it should work but am not quite sure how to do this.
« Last Edit: December 13, 2016, 07:43:11 PM by Arkcon »

Offline Arkcon

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Re: Instrument drift
« Reply #1 on: December 13, 2016, 07:48:46 PM »
For an analytical application, I wouldn't try to do it that way.  First of all, we should try to understand the drift:  random, or rising or falling?  All three have different explanations possible.  What happens if you leave the instrument powered for a long time?  Drift may stop if you do.  Perhaps the instrument specifies a warmup time, 15 minutes or an hour.  And perhaps you discover that it needs more -- that happens.

If the drift is linear, then you can develop a curve for standards that flank your samples.  If your drift is random, then the average of your standards may be the best answer you can get.

But a lot of this is outside of how most people like to report their analytical results.  You should give us some information on your application.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

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