Empower Tip: Review Window and the Processing Method

Let’s start by creating the custom calculation. This is done in the properties of your project. Go to the Configuration Manager window by clicking Configure the System from the Pro Interface.

Right-click on the row number for your project and select Properties.

Click the Custom Fields tab and then click the New button to launch the New Custom Field Wizard.

On the Data and Type Selection screen select Peak for the Field Type and Real for the data type. A peak custom field is a calculation that can be applied to every peak in the chromatogram. Click Next.

Do not change anything on the Source Selection screen. Click Next.

We will enter the formula on the Formula Entry screen. Signal-to-noise ratio is peak height divided by detector noise. In the Fields list scroll to the right and double-click on Height.

From the Operations list double click the forward slash which is the division symbol.

Height is in microvolts and detector noise is in plot units so we will need to correct for the difference in units. In the denominator enter a left parenthesis.

In the Fields list locate Detector Noise and double click to add it to the formula. Then double-click the forward-slash.

In the Fields list locate Scale to uV and double-click to add it to the formula. The Scale to uV will correct for the difference in units. Then add the right parenthesis. Click Next.

Set the desired precision on the Numeric Parameters screen and click Next.

Enter a name on the Name Entry screen and click Finish. Note: you cannot use spaces in the name but could do shift underscore.

Click OK on the warning message.

Now let’s use the custom field. Open the project and bring raw data (Sample Set, Injection, or Channel) into review and open the Processing Method. Click the Processing Method tool.

Click the Noise and Drift tab.

Check the box for Calculate Detector Noise and Drift and enter a time interval which is free of peaks for calculating noise. 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.

Return to the Main Window and click the Integrate tool.

If signal-to-noise ratio is not visible we can add it to the Peaks table. Right-click on the Peaks table and select Table Properties.

On the Columns tab, find signal-to-noise ratio and remove the check mark to make it visible in the table. Click OK.

The signal-to-noise ratio is displayed for every integrated peak.

It’s that easy!