QDa MS Data in Empower - Base Peak Values - Tip357

OBJECTIVE or GOAL

How to obtain Base Peak Values from the UV Chromatogram

ENVIRONMENT

• Empower
• Empower Tip of the Week #357

PROCEDURE

STEP 1
Bring the 3D PDA channel into Review and extract a wavelength of interest (figure 1).

STEP 2
Integrate the peaks either manually or by using a processing method and the base peak field is populated for any integrated peaks and the UV spectra for those peaks appear in the Spectrum Review window (figure 2).

STEP 3
Click the Mass Analysis tool to open the Mass Analysis window or select Mass Analysis Window from the Window menu. The UV and MS spectra are displayed for every integrated peak (figure 3). The Mass Analysis window displays a variety of information which we will explore in future tips.

STEP 4
From the 2D Channels tab, we can select the MS TIC and overlay it with the UV chromatogram. (Be sure to click the Autoscale tool to correct for the difference in scaling.) You can see that the peaks in the MS chromatogram elute slightly later than those in the UV chromatogram because the QDa detector is second in the series (figure 4). 

STEP 5
Click on the MS chromatogram and you can see the MS spectra for the peaks in Spectrum Review.  The retention times in the Spectra table are taken from the peaks in the UV chromatogram (figure 5).

STEP 6
We can correct this slight offset in the Smoothing/Offset tab of the processing method by entering a small offset. It is recommended to calculate the average retention time difference for the peaks between the two channels and use that as the offset value (figure 6). 

STEP 7
Reprocessing the injection with the revised processing method gives us a better overlay of the chromatograms and the retention times of the spectra are corrected to correspond to the peaks in the MS chromatogram (figure 7). 

 

ADDITIONAL INFORMATION