In order to start a harmonization on the the reporting of LoQ in water analysis, I would be glad to know how this descriptor of method performance is established in your country, and if the protocol leads to LoD or to LoQ.
(I'm French, I'm seeking for non-french way od doing)
USA:
LOQ is defined in various ways in the US. A typical definition would be 3 times (or 3.3 times) the LOD. However, for water analysis TNI (the NELAC Institute) defines the LOQ as your lowest calibration standard, which should be somewhere around 3-5 times your LOD.
The definition of LOD is not at all straightforward, as there are multiple methods used to determine "LOD". The most common is the USEPA definition found in 40 CFR 136 Part B, which is a statistical determination based on the noise inherent in the analysis of multiple replicates (7) of a known concentration standard. However, this is not the only means of measuring LOD. Since LOQ is dependent upon the measurement of the LOD, your definition of the LOD impacts your definition of the LOQ.
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