Get Empowered: Review Window and the Processing Method | Tip #70, System Suitability
Tip #70: Working with the System Suitability Option (Part 3)
In this week’s tip, we are going to learn how Empower calculates Baseline Noise and Drift (part 3).
If you are not in a regulated laboratory environment, you probably want to calculate Signal to Noise without the USP, EP, or JP formula (Tip #28). One of the options for noise is Baseline Noise. This is the original option that was available with Millennium chromatography software in the 1990s.
Let me show you how it is done.
We begin by bringing a Sample Set into Review, open a Processing Method, and Integrate/Calibrate or Integrate/Quantitate a channel (Figure 1).
Go to the Processing Method window, click the Suitability tab, and select Baseline Noise from the Noise Value for s/n drop-down list (Figure 2).
The Baseline Noise minimum is either a minimum time interval or minimum number of data points used to calculate baseline noise (Figure 3).
So, how does Empower calculate Baseline Noise? The software calculates noise based on the maximum signal change over a 30-second interval. The reported noise value is an average of two 30-second intervals, as determined by the parameter % Run Time Over Which to Average. To determine the 30-second intervals, the software begins counting from the Baseline Start time and the Baseline End time toward the middle of the chromatogram.
In figure 4, we have a 10-minute run time. 0.5% of 10 minutes is 0.5 minute. Therefore, region 1 is 1 to 1.5 minutes and region 2 is 8.5 to 9 minutes. Be sure to pick areas of the baseline that only contain noise and not peaks, otherwise you will have a high noise value reported.
In our chromatogram, we have a 15-minute run time, therefore, if we use 3.5 for the % Run Time Over Which to Average, that will give us 30-second intervals. We set the Baseline Start to 0 and the Baseline End to 15 (Figure 5).
Return to the Main Window and Integrate/Calibrate or Integrate/Quantitate. The Signal to Noise is calculated using Baseline Noise for each integrated peak (Figure 6).
Go to the Results window and we can see the Baseline Noise, Baseline Drift, and Scale to microvolts fields in the Chromatogram Result table (Figure 7). The Baseline Drift is simply the signal at Baseline End minus the signal at Baseline Start.
It’s that easy!
- Peak height is in microvolts and baseline noise is in millivolts, therefore, Empower uses the scale to microvolts factor to convert the baseline noise into microvolts.
- This procedure can be followed using the QuickStart or Pro interface.
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Next week in Empower Tip #71 – Working with the System Suitability Option in Empower (part 4)
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