Detection limit

Limit of detection (LOD) is the smallest amount of an analyte whose signal can be distinguished from noise.

The detection limit (LDD) is usually defined as the minimum amount or concentration of substance that can be reliably detected by a given analytical method. Intuitively, the LDD would be the minimum concentration obtained from the measurement of a sample (containing the analyte) that we would be able to discriminate from the concentration obtained from the measurement of a target, that is, from a sample with no analyte present .

wiki