Skip to main content
Waters

Peak Purity using the QDa Detector - Tip253

Article number: 223616

OBJECTIVE or GOAL

This article will discuss Peak Purity using the QDa Detector

ENVIRONMENT

  • Empower
  • Empower Tip of the Week #253

PROCEDURE

STEP 1
When the Photodiode Array (PDA) Detector and QDa Detectors are connected in series, there is a time offset between the two, i.e., the peaks will elute earlier on the PDA Detector. The first peak has a retention time of 1.378 minutes in the UV chromatogram and 1.381 in the MS chromatogram (figure 1).


Figure_1.png

 

STEP 2
In the Mass Analysis window, Empower takes the Apex spectra (both UV and MS) from the retention times of the peaks in the UV chromatogram. The MS spectra are extracted a little bit earlier than desired (figure 2) 


Figure_2.png

 

STEP 3
You can correct for the offset on the Smoothing/Offset tab in the Processing Method. Calculate the average difference in retention times between the two channels and enter that value in the Time Offset (min) field for the PDA Channel (figure 3)


Figure_3.png

 

STEP 4
Now the MS spectra are extracted at the proper times (figure 4).


Figure_4.png

 

STEP 5
Changing to Purity view, Empower displays the MS spectra from the leading edge, apex and trailing edge of each of the integrated peaks. In the first peak, the MS spectra for the leading and trailing edge are noisy as they are being extracted from the baseline (figure 5).


Figure_5.png

 

STEP 6
There are two factors which can influence where Empower extracts those spectra. The integration can be adjusted so that the peak starts/ends are not in the noisy baseline. You can also adjust where Empower extracts those spectra on the MS 3D Channel tab under MS Spectra Extraction. The percentage is from peak start to the retention time of the peak. For example, if you set the Leading Extraction Spectra Point (%) to 50, then it extracts the leading-edge spectrum halfway between peak start and the retention time (figure 6).
Figure_6.png

 


STEP 7
The resulting spectra for the leading and trailing edges are not as noisy, and in this case, the MS spectra appear to be consistent over the three points across the peak (figure 7).


Figure_7.png


 

ADDITIONAL INFORMATION

Final Note: This can be done with either the Pro or QuickStart interface.

id223616, EMP2LIC, EMP2OPT, EMP2SW, EMP3GC, EMP3LIC, EMP3OPT, EMP3SW, EMPGC, EMPGPC, EMPLIC, EMPOWER2, EMPOWER3, EMPSW, SUP

Not able to find a solution? Click here to request help.