Empower Tip: Processing Methods

In this tip for Empower Chromatography Data System (CDS), we will continue our series on Processing Methods. In the last tip, we continued our series on creating Processing Methods and learned about calculating signal-to-noise ratio in a regulated lab, Tip 323.

In this tip, we will learn how to set up the Processing Method to calculate signal-to-noise ratio, in a non-regulated laboratory.

In this example, we are not bound by the pharmacopeias.

The area within the dark yellow box on the Suitability tab has the selections for signal-to-noise calculation. The rest of the information on this tab can be ignored.

STEP 2:

Select how you want noise calculated from the Noise Value for s/n list, in this case peak-to-peak noise.

For everything except Baseline Noise, you need to select a portion of the baseline within the chromatogram which will be used for noise determination.

Go to the Noise and Drift tab and enter that time region over which peak-to-peak noise will be calculated. The difference between the start and stop time must contain at least 60 data points. The segment width is used for calculating average noise and drift. The segment width must contain at least 30 data points. Hint: Check the sampling rate in the Instrument Method which is in points per second and then multiply that by the segment width in seconds. This will give you the number of data points in the segment.

Once the data is processed, you’ll see signal-to-noise and the peak-to-peak noise calculated from the region selected in Step 4.

Let’s consider using Baseline Noise for our signal-to-noise calculation.

Baseline Noise is calculated by selecting two segments within the baseline from which noise is calculated. The noise in those two regions is averaged and Baseline Noise is reported. The two segments must have a minimum of 30 seconds each or 30 points each. Set the % Run Time Over Which to Average as a percentage of the runtime which results in a segment of at least 30 seconds or 30 points. Empower starts at the Baseline Start and adds 30 seconds, for the first segment. Empower starts at the Baseline End and subtracts 30 seconds, for the second segment.

In this example, the run time is 5 minutes, therefore, set the % Run Time Over Which to Average to 10% which results in a segment width of 30 seconds. The Baseline Start Time is 0 and the Baseline End Time is 5.

Once the data is processed, you’ll see the signal-to-noise, the Baseline Noise and Baseline Drift calculated from the region selected in Step 8. Baseline Drift is calculated as the Baseline Noise at the selected Baseline End Time minus the Baseline Noise at the selected Baseline Start Time.

It’s that easy!