Threshold calculation

The reference threshold at 50% sensitivity is calculated using the following formula:

where

VARnoise

Calculated variance threshold of the noise spectra

VARpeak

Variance of the peak spectra

VARtarget

Variance of the spectrum used for the comparison (peak start for data points purity calculation before the apex, and at peak end for data points purity calculation after the apex)

The threshold (Ts) used in the software depends on the sensitivity value. It is calculated with following formulas:

If the sensitivity is greater than 50%:

If the sensitivity is lower than or equal to 50%:

where

TS

threshold [0 – 1000] for selected sensitivity S

T

Reference threshold at 50% sensitivity

S

Sensitivity [0 - 100] %

For each individual threshold value, at each raw data point, one of these formulas is applied.

The red curve is the automatically calculated threshold curve. The automatically calculated threshold value for this curve example is 980 (which is the sensitivity value 50%).