When is a lower limit of detection low enough?

In cleanup operations and environmental surveillance efforts, a level of concern usually specifies a concentration limit for a particular radionuclide above which some action may be warranted. It is critical that the analytical method selected for measurements has a detection limit well below the action level. This is to guarantee that the technique used provides precise assessment at the level of concern. Sample analysis made with good precision is one of the major steps for obtaining quality data that allow a sound decision on whether the nuclide concentration is in compliance. This paper examines how the magnitude of the detection limit of an analysis method affects the precision of a measurement at the action level. With the established relationship, the detection limit that would achieve a pre-set precision for measurements at a level of concern can be quantitatively determined. The desired detection capability thus serves as a guide for selecting the appropriate measurement system.