The limits of detection (LOD) and quantification (LOQ) are evaluated using the following equations [1-4]:

LOD=3.3 S0/b
LOQ=10 S0/b

   where S0 is the standard deviation of the calibration line’s y-intercept
where b is the slope of the linear regression line of best fit.

The limit should be subsequently validated by the analysis of a suitable number of samples known to be near or prepared at the quantitation limit.

References:
[1]  Ermer, J.; Validation in pharmaceutical analysis. Part I: an integrated approach; Journal of Pharmaceutical and Biomedical Analysis, (2001); 24: 755-767.
[2] Perez-Bendito, D., Silva, M.; Kinetic Meth. in Analytical Chemisry; Chichester, Ellis Horwood, (1988), pp. 254.
[3] Mottola, H.A.; Kinetic Aspects of Analytical Chemisry; New York, Wiley, (1988), pp. 40.
[4] Thomsen, V., Schatzlein, D., Mercuro, D.; Limits of detection in spectroscopy; Spectroscopy, (2003); 18(12): 112-114.
[5] Dolan, J.W.; What’s the Problem with the LLOQ? — A Case Study, LC-GC North America, 31 (11), pp. 926-931.

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