The limit of quantitation is the lowest amount of a compound a validated method can put a reliable number on. It sits above the LOD, often around ten times the blank standard deviation. Between the LOD and the LOQ a lab can say "something is there" but not "how much".
In practice
A potency COA might show CBN "<LOQ" with an LOQ of 0.05% w/w: the lab thinks it's probably present, below 0.05%. When labs report totals, check how they treat <LOQ values: counting them as zero, as half the LOQ, or as the LOQ itself changes the sum slightly. For contaminants, an LOQ above the regulatory action limit would make the test useless; accredited methods are validated so the LOQ sits comfortably below the limit.
Units and formula
Same units as the result. A common estimate is LOQ ≈ 10 × SD of the blank, divided by the calibration slope; labs confirm it by spiking samples at that level.
Don't confuse with
- LOD: the lower "is it there at all" threshold.
- ND: not detected, meaning below the LOD.
