For research use only. Not for use in diagnostic procedures.
Signal to noise measurements can be performed in Analyst software by the following two methods.
Using Explore Mode is suitable for when the measurement is to be performed on a single chromatogram and mass range.
Using Quantitate Mode is best suited to routine measurements across a batch where the resulting value is to be compared across samples. This method will also measure the value for multiple mass ranges at the same time.
Using Explore Mode:
Click Open Data File and select the file and sample on which you wish to perform the measurement.
Select your area of signal by moving the cursor to the start of the area and swiping sideways whilst holding the left mouse button. This will cover the area of your signal with a light blue shading.
To select the noise region hold down the shift key and move the cursor to the start of your noise region. Whilst holding the shift and left mouse button swipe the cursor over your noise region and then release the mouse button and shift key.
You should now see 2 areas selected.
To Calculate the signal to noise Select Script from the menu bar and select S-To-N Script.
The signal to noise values will then be written directly above the Signal area.
Using Quantitate Mode:
Select ‘Build Quantitation Method’ and then select a representative sample which to use as the basis for the quantitation method. In order to define the signal and noise regions for any the analytes select the Integration tab.
For each analyte select the area you wish to use as the signal (also defines the peak retention time) by moving the cursor to the start of the peak, clicking and holding the left mouse button whilst sweeping across the peak. Once you have selected the area of the peak click the ‘Select Peak’ button.
This will change the value in the Expected RT: box. Then define the noise by using the mouse in the same way (left click and hold then sweep the mouse to cover the area) and then click the ‘Set Parameters From Background Region’ button
Once this process has been completed for all analytes you can save the method and use it to quantitate as normal. Once you have created your results table you may need to show the Analyte Signal To Noise column from the Analyte section in your table settings.
You can now see that the signal to noise has been calculated according to the regions specified in the method. It is also possible to redefine the signal and background regions using the same buttons as in the method in the peak review pane, however changing the settings here will only apply to this peak and will require that ‘Accept’ is clicked before the results table is updated.