MassQC Help > Metrics > MS1 > Signal to Noise          
MS1 Signal to Noise

Signal to Noise estimates how strong the signal is, that is, how much larger the large peaks in the spectrum compared to the the background noise.

Higher Signal to Noise indicates the strength of the signal that can be used to identify peptides, that is, higher signal discrimination.

The MS1 Signal to Noise metric is estimated by taking the ratio of the maximum to the median of the MS1 peaks heights. The Signal to Noise metric is calculated over the Retention Spread, the middle part of the elution time when most of the peptides are elution.

Units:

Ratio of Signal to Noise

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:

Signal to Noise estimates the signal strength. The estimate of the noise level depends upon threshold settings that determine which low level peaks get included. Often there are lots of very low intensity peaks so that the median is a very low level. The result is that the reported Signal to Noise, the ratio of the max peak to the median, often looks higher than one would estimate by looking at the spectra. However it is useful for comparing the signal strength over runs.

Related Metrics:

According to the research done at NIST, the Signal to Noise provides a more stable measure of the signal strength than either the Total Ion Current or Peak Intensity. Note that all measures of signal strength can't differentiate between variations in the amount of sample injected and changes in instrument sensitivity.

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