MassQC Help > Metrics > Ion Source > Percent +4H          
Percent +4H

Percent +4H is the percentage of all spectra matching peptides that have a charge of +4.

Higher Percent +4H indicates that the mass spectrometer may favor long peptides.

Percent +4H is calculated by looking at the charge state of all spectra that match to a peptide.

Units:

Percent (%)

Optimal:

Consistent

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:

A high Percent +4H means that there are an unusual number of plus 4 ions. This might mean that the electrospray is behaving erratically..

Related Metrics:

Large Percent +4H means that the other charge states don't get as many ions. The metrics Percent +1H and Percent +3H also report the ion's charge state. Any ions that are not charge +1, +3, or +4 are probably charge +2.

If the distribution of charge differs, it may affect the size of the peptides that are detected. Another way to look at this is with the metric Precursor m/z.

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