Empower Tip: Review Window and the Processing Method

In this tip, will we will learn how to use a function called Combine Spectrum. This creates a single, summed, or averaged scan from selected spectra across a chromatographic peak or baseline, yields an enhanced signal-to-noise ratio, and thus improves mass accuracy. It can also be used as a quick check of spectral homogeneity.

EXAMPLE 1

STEP 1 We start by bringing a 3D MS channel into Review, extract a TIC plot, and integrate a peak. Note the spectrum for the peak.

Click on the Combine Spectrum tool (or select Combine Spectrum from the Process Menu). This dialogue box allows us to either average or sum spectra across a peak and subtract a baseline spectrum from all spectra selected across that peak.

Right-click, and while holding down the button, drag the cursor thru the peak to select the portion of the peak you want to use for the average. Repeat the procedure by right-clicking and dragging the cursor thru a portion of the baseline.

The ‘Average’ and ‘Subtract’ fields are now populated. Click ‘Apply’ or ‘OK’ to view the combined spectrum in Spectrum Review. The original apex spectrum for the peak was an average of 5 spectra as set in the Processing Method. The combined spectrum was an average of 23 spectra. In this case, there is very little difference between the 2 spectra.

EXAMPLE 2

Repeating the process with a different peak, you will notice a significant difference between the apex spectrum and the combined spectrum which indicates spectral heterogeneity and further investigation of this peak should be done.

It’s that easy!