Processing methods - Calculate signal-to-noise ratio using a specified segment from the blank injection - wkb260922

OBJECTIVE or GOAL

Calculate signal-to-noise ratio using a specified segment from the blank injection.

ENVIRONMENT

• Empower
• Empower Tip of the Week #325

PROCEDURE

STEP 1
USP signal-to-noise is calculated as 2x Height of peak/noise. Empower uses the following formula to comply with USP: 2x[Height of peak – (0.5xPeak to Peak Noise/Scale to microvolts)]/(Peak to Peak Noise/Scale to microvolts) (Figure 1).

STEP 2
From the Sample Set Method, Blank is the label for the blank injection, and there is only one injection. This is single-channel UV data, so there is no need to specify the channel (Figure 2).

STEP 3
Create a peak Custom Field using intersample syntax. We need the Scale to µV field in the equation because peak height is in µV (microvolts) and peak-to-peak noise is in detector units, which in this case is AU (Figure 3).

STEP 4
The full view of the Custom Field is provided (Figure 4).

STEP 5
On the Suitability tab in the Processing Method, select peak-to-peak noise from the Noise Value for s/n drop-down list (Figure 5).

STEP 6
On the Noise and Drift tab in the Processing Method, select the time region from the blank injection from which peak-to-peak noise will be calculated (Figure 6).

STEP 7
After the Sample Set is processed, take the Result Set into Review. Go to the Results window. In the Chromatogram Result table we can see the peak-to-peak noise calculated from the blank injection (Figure 7).

STEP 8
Click on a result for one of the standards or samples. The Custom Field is calculated based on the noise from the blank injection specified in the Custom Field (Figure 8).

Important Note: Peak-to-peak noise will be calculated for every injection, but it is the peak-to-peak noise from the blank injection thatis used to calculate signal-to-noise for all peaks in all injections.
 

ADDITIONAL INFORMATION

This can be done with either the Pro or QuickStart interface.