Detection limit

Detection limit, also known as the limit of detection (LOD), is the lowest quantity of a substance that can be distinguished from the absence of that substance (a blank value) within a stated confidence limit (generally 1%).

Definition

The detection limit is estimated from the mean of the blank, the standard deviation of the blank and some confidence factor. Another consideration is that the (statistical) noise in the signal (which is determined from the standard deviation of the blank measurement) can be defined in a number of ways.

Calculation

The calculation for the detection limit uses the standard deviation of the response and the slope of the calibration curve. The slope of the calibration curve is estimated from the data collected for the standard samples. If a more sensitive instrument is used, the standard deviation of the response will be smaller and the slope of the calibration curve will be larger; therefore, the detection limit would be expected to be smaller.

Applications

The detection limit is used in a variety of fields, including chemistry, pharmacology, environmental science, and forensic science. It is used to determine the lowest concentration or absolute amount of analyte that can be reliably detected by an analytical procedure.

See also

• Limit of quantitation
• Sensitivity
• Specificity