How to Check the signal-to-noise ratio with Agilent OpenLab CDS (version 2.x)

Answer

This Information Applies To: Agilent OpenLab CDS (version 2.x)

Content:

The following procedure shows how to check the signal-to-noise ratio in OpenLab CDS (version 2.x). 

Steps to Follow:

Prerequisites

• Use a processing method configuration that includes system suitability parameters feature. (see Figure 1)

Figure 1. System Suitability location in the processing method description

• To be able to carry out the procedure as described, you need the privilege Processing Method > Edit system suitability parameters. Privileges are configured in the Control Panel (see Figure 2).

  Figure 2. Edit system suitability parameters location

Edit the processing Method.

1. Optimize data integration.

Switch to Home tab and click Processing Method. Set the desired integration parameters according to the chromatogram (see Figure 3).

Figure 3. Processing Method window.

2. Set system suitability parameters.

In the Processing Method window, select System Suitability > Properties. Then fill out the parameters on the page, see Figure 4. The following is a detailed explanation of these parameters:

• Signal-to-noise: choose All Peaks.
  
  
• Noise Calculation: Select the required Noise calculation, Software supplies four options to calculate noise ASTM, 6SD, P2P, RMS.

• 6 sigma or RMS method.

The signal-to-noise is calculated using the formula:

Signal-to-noise = Height of the peak / Noise of closest range

• Peak to peak or ASTM method

The signal-to-noise is calculated using the formula:

S/N = 2 H/h

Where:

H – Height of the peak corresponding to the component concerned in the chromatogram obtained with the indicated reference solution.

h – The absolute value of the largest noise fluctuation. It is calculated considering the value of the baseline after injection or application of a blank. It is observed over a distance equal to 20 times the width at half-height of the peak in the chromatogram obtained with the reference solution, and situated equally around the place where this peak would be found.

According to the European Pharmacopoeia, signal-to-noise is calculated against a blank reference signal. The noise is calculated over the time range that contains the peak, for which the S/N ratio is calculated.

• Noise range:

Automatic(On blank recommended for EP) – the noise is calculated in the last blank run (sample type = Blank) which was acquired before the injection. The range is calculated at the retention time of the peak -10 and +10 times the half peak width on the corresponding signal.

Fixed – the noise is calculated in a fixed range of the current signal or the last blank signal

Relative from – Time region relative to the peak start or end, on the same signal or on a blank reference signal.

Figure 4. System Suitability parameters.

3. Reprocess the injections.

4. In the Injection Results window, click show column chooser on the left and select columns S/N and Noise. The S/N column contains the signal-to-noise ratio as calculated with the chosen algorithm. You will see the S/N and Noise results in the table (see Figure 5).

Figure 5. Inject Results window.
(1) Injection Results tab, (2) Show column chooser, (3) Noise column, (4) S/N column.

Learn more on how to effectively operate Agilent OpenLab CDS: Data Analysis Reference Guide user manual