Get Empowered: Review Window and the Processing Method | Tip #28

By August 2, 2017


Tip #28: Calculating signal-to-noise ratio

In the last tip-of-the-week post for Empower Software, we explored how to use the System Suitability option to flag failing results. The next several tips will address how to calculate signal-to-noise ratio.

Just about everyone wants to calculate signal-to-noise (S/N) ratio and Empower Software can make the calculation in several different ways.  Let’s begin by looking at the simple calculation of peak height divided by noise. [Part 1 | Part 2 (#29) | Part 3 (#30)]

Step 1

Bring raw data (Channels, Injections, or Sample Set) into Review and open the processing method. Click the Processing Parameters tool (Figure 1).

Empower Tip: Processing Parameters tool | figure 1

Figure 1

Step 2

Click the Suitability tab and check the box that says Calculate Suitability Results. Enter the Void Volume Time; an estimate is fine (Figure 2).

Empower Tips: Calculate Suitability Results | figure 2

figure 2

Step 3

Select how you want noise calculated from the Noise Value for S/N drop-down list (Figure 3). Peak to Peak Noise is a popular choice.

Empower Tips: Select noise calculated/ noise value | figure 3

Figure 3

Step 4

Select where in the chromatogram you want noise calculated by clicking the Noise and Drift tab. Click Yes to the message that appears (Figure 4).

Empower Tips: Noise and Drift tab | figure 4

Figure 4

Step 5

Select Calculate Detector Noise and Drift (Figure 5).

Empower Tips: Calculate Detector Noise and Drift | figure 5

Figure 5

Step 6

Enter a time region in the chromatogram that is free of peaks (Figure 6). This time region must be equal to or greater than the Segment Width, and must contain at least 60 data points. The Segment Width is used for calculating average noise and drift values and it must contain at least 30 data points.

Empower Tips: Entering segment width | figure 6

Figure 6

Step 7

Return to the Main Window and click Integrate followed by either Calibrate or Quantitate (Figure 7).

Empower Tips: Integrate >Calibrate/Quantitate | figure 7

figure 7

Step 8

Signal-to-noise is a hidden field by default so let’s add it to our Peaks table. Right-click on the Peaks table and select Table Properties (Figure 8).

Empower Tips: Peaks table/select Table Properties | figure 8

Figure 8

Step 9

On the Columns tab, find s/n and remove the check mark to make it visible in the table (Figure 9).  Click OK.

Empower Tips: Table properties/Remove the check mark | figure 9

Figure 9

Step 10

The signal-to-noise ratio is displayed for every integrated peak (Figure 10).

Empower Tips: signal to noise ratio is displayed | figure 10

Figure 10

Step 11

To keep the S/N field in the peaks table, select Save Preferences from the File menu (Figure 11).

Empower Tips: Save Preferences | figure 11

Figure 11

Step 12

Finally, save all changes to the Processing Method (Figure 12).

Empower Tips: Save changes in Processing method | figure 12

Figure 12

It’s that easy!

I can calculate signal-to-noise ratio in #EmpowerCDS! #EmpowerTips Click To Tweet

Final notes:

  1. You must have the System Suitability option and enable it in the project.
  2. This procedure can be followed for both the QuickStart and Pro Interfaces.
  3. Since peak height is in microvolts and detector noise is in plot units, Empower automatically corrects for the difference in units by applying a Scale to Microvolts factor.

Please rate this Empower Tip of the Week


 

Next week in Empower Tip #29: Calculating Signal-to-Noise Ratio (Part 2)

 

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