Confirming the identity of a compound by using the signal ratio

The identity of a compound can be confirmed by using a dual wavelength detector in conjunction with the Virtual Detector and checking if the signals ratio is constant with the following procedure. Prerequisite to this is a know signal ratio for used wavelengths. With correct comparison formula the Virtual Detector signal should result in flat line when the peak is pure compound, impurities with different signal ratio would be represented as response change on the Virtual Detector signal.

  1. Add the Virtual Detector as well as your dual wavelength detector to the instrument, if not already present, based on chapter Adding a new device.
  2. Open the Method Setup dialog and navigate to Acquisition tab.
  3. Select VD: Channel 1 in the Select Detector drop-down list .
  4. On the Argument settings tab, tick the Argument X checkbox, select an Ext. Source , then click on the Settings button , select the appropriate detector Channel and click OK .
  5. Repeat the same steps for Argument Y and select the second channel from the detector.
  6. If want to use the same signal ratio for entire analysis you can fill in the Resulting Formula field with the proper formula. If you need multiple formulas for different times skip this step and continue with the next one.
  7. To set multiple formulas for different time intervals navigate to the Advanced settings, check the Use Advanced Settings checkbox and fill the time table as needed.
  8. On the Detector settings tab, set the Time to 0 to avoid distortion and fill Sampling Rate equal to the actual detector sample rate.

Method prepared this way can be used to check compound identity as mentioned in the beginning of this chapter.