Limit of quantitation (LOQ)
LOQThe limit of quantitation is the lowest concentration at which an analytical method can assign a numerical value with acceptable accuracy and precision.
It sits above the limit of detection: between the two, the method can tell that something is present but cannot say reliably how much. Laboratories set the limit of quantitation through validation studies, and it varies by analyte, method and sample matrix. Results between the two limits are often reported as trace or as below the quantitation limit rather than as a number.
On a certificate of analysis the limit usually appears in its own column, and reading it explains why some entries show a symbol instead of a figure. For THC, a result of 0.0% THC tells the reader the measured amount fell below the reporting threshold the laboratory applies, and the quantitation limit column shows how low that threshold was. Comparing certificates from different laboratories is only meaningful when their quantitation limits are similar.