The limit of detection (LOD)

[shafaifer]

The LOD is defined as the minimum concentration of an analyte required, wherein the
analytical signal is significantly different from the blank signal (background signal).

Am I right in this:

• The lower LOD-value, the higher analyte concentration.

In an AAS study of the mass of calcium carbonate in potsherds (first dissolving the sherds in concentrated nitric acid, then measuring an absorbance-value, calculating a concentration for calcium --> m_CaCO3(s) is obtained), what use is it to know what the minimum concentration of calcium is, wherein the
analytical signal is significantly different from the blank signal? If this cannot be answered, what use is it in general in analytic chemistry?

[CharonY]

Am I right in this:

• The lower LOD-value, the higher analyte concentration.

This is sometimes used in a confusing fashion. But the "lower" part typically refers to the concentration at which the analyte can be distinguished from background. I.e. a lower level means that lower amount of analyte can still be detected. I.e. a low LOD has a high sensitivity. The phrasing is confusing however, as a low LOD does not tell you anything about the actual sample concentration. Only how low you can go before you cannot detect it anymore.

 

I am not quite following the second part of your question. Are you asking what the purpose of identifying the LOD is?

[shafaifer]

Thank you very much, Charon. Yes, that is what I am asking.

[CharonY]

If your question why establishing LOD is important, it is a benchmark for analyses. Obviously, if the detection limit is not adequate for your sample, it means that you either need to change your sample prep, or your instrument.