MassQC Help > Metrics > Dynamic Sampling > Trigger Point          
Trigger Point

The Trigger Point is the intensity on the extracted ion current (XIC) chromatogram where the MS2 scan is triggered.

High Trigger Point mean that the mass spectrometer is efficiently sampling the signal for the MS2 scans. A low Trigger Point means that only a small portion of the available signal is being used for peptide identification.

The Trigger Point metric is the percentage of the maximum MS1 peak which is sampled for MS2. The metric is the median value of this measurement over all the times that MS2 is sampled.

Units:

Percent (%)

Optimal:

Higher

The most reproducible LC-MS performance is when this metric remains in a narrow range over a series of runs. Wide variability in any metric means your process is not reproducible.

What the Metric Detects:

Under ideal circumstances, chromatographic peaks would be sampled at their maximum intensity. That is, the Trigger Point metric would be 100%. If the Trigger Point is too low, there may be insufficient ion current for the MS2 spectrum to have a signal-to-noise ratio that is adequate for successful peptide identification.

Since the Trigger Point is a percentage of the peak height, an unusually high Trigger Point may indicate that there are many peaks just above the Trigger Point. In other words, the MS/MS is triggering on noise.

Related Metrics:

The Trigger Point is calculated for all the MS2 spectra attached to peptides. The Low Intensity Trigger Point is the same as the Trigger Point except it is calculated only for the MS1 peaks with low intensity, i.e., lowest 50% in abundance.

If the MS/MS instrument is set to trigger MS2 scans at a very low intensity, then the MS2 may often be triggered on noise. This circumstance might be detected by the MS1 Signal to Noise Metric.

Related Troubleshooting Topics:
Forum:

If you have questions, comments and/or insights about MassQC, you can share them on the MassQC Users Forum.

Search the MassQC Site and the Help Center: