N = level of peak-to-peak noise
S = peak height for the analyte of interest
P = purity level for the analyte of interest
The above equation expresses LOQ as a function of signal-to-noise ratio and the observed
purity of the analyte. Both parameters can change from test-to-test, due to equipment
variability and sample purity variability. Therefore this equation should be viewed as the
dynamic (live) assessment of LOQ.