Limit of Detection (LOD)

Last Updated: May 23, 2018

Definition - What does Limit of Detection (LOD) mean?

The Limit of Detection (LOD) is typically defined as the lowest concentration or quantity of a component or substance that can be reliably distinguished with a specific analytical method. Instinctively, the LOD would be the lowest amount of concentration that is obtained from measuring a sample that contains the component that we would be able to differentiate from the concentration that has been obtained from a measured blank sample (one which doesn’t contain the component).

The LOD is used to express the lowest concentration of an analyte that can be detectable by a specific instrument, method or sample. If a measured sample is found to have a concentration that is lower than this value or gives a reading that cannot be distinguished from the set reference point, the best that we can confidently say about the sample is that the existing analyte is below the LOD.

However, you can never assert that the sample doesn’t completely contain the analyte in question because there is always a possibility, however bleak, that it does, but not in amounts that can be sufficiently detected.

The LOD may also be referred to as lower limit of detection or the detection limit.

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WorkplaceTesting explains Limit of Detection (LOD)

The corresponding LOD is always calculated whenever and instrument calibration is performed. Any result that is below this value is quoted as being "<LOD" with the determined LOD being stated clearly. The LOD concept has been and is still among the most controversial subjects in analytical chemistry. This is because already, there are several proposed definition and methods of calculation.

Even though in the recent years, multiple international organizations such as IUPAC (International Union of Pure and Applied Chemistry) or ISO (International Organization of Standardization) have made an effort to reach a consensus in their definitions of this term and have issued out guiding principles for the assessment of this crucial parameter in chemical analysis, it is still a subject of scientific debate.