Limit of detection (LOD) and limit of quantitation (LOQ)

LOD is the lowest concentration the instrument can reliably distinguish from blank, defined as three times the standard deviation of the blank or a signal-to-noise ratio of 3:1. LOQ is where the response is reliable enough to put a number on, ten times SD of blank or S/N of 10:1. A case result below LOQ is reported as 'detected, below LOQ', not as a number.