Detection limit

The detection limit ( English limit of detection , LOD, or lower detection limit , LDL) describes the extreme value of a measurement process up to which the measured variable can just be reliably detected (yes / no decision).

The measured value at the detection limit has an increased inaccuracy, but this does not exceed a specified statistical confidence interval . Measured values ​​(facts) that are more inaccurate than the specified interval are outside the detection limit and are referred to as immeasurable or undetectable in terms of measurement technology .

The criterion of "reliable evidence" is usually based on the precision of the measurement method in the case of a zero measurement or blank measurement. This means the statistical error or the fluctuation of the measurement signal when no sample is available (e.g. the standard deviation of the background signal or blank value ).

A measurement is often considered evidence if the measured value is at least three standard deviations above the zero measurement.

${\displaystyle \mathrm {LOD} =y_{B}+3s_{B}}$

• ${\displaystyle y_{B}}$: Mean value of the blank value
• ${\displaystyle s_{B}}$: Standard deviation of the blank value

See also

• Limit of quantitation

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• DIN 32645: chemical analysis; Detection, detection and quantification limits; Determination under repetitive conditions; Terms, procedures, evaluation.

Web links

• Quality assurance through DIN-compliant calibration