An Alternative Minimum Level Definition for Analytical Quantification

This paper presents a new approach to quantitative de termination in analytical chemistry. Various historical ap proaches to determining the quantification limit are reviewed. The Alternative Minimum Level (AML) directly models the relationship between variability and concentration and can incorporate variability from multiple analysts, instruments, and laboratories. In addition, the AML incorporates uncertainty in the calibration function that relates instrument response to true concentration and uncertainty in the standard deviation at the AML. The net result is that the AML is robust to selection of spiking concentration and only requires that we have a reasonably accurate model of the relationship between concentration and standard deviation of instrument response or measured concentration. Computation of the AML and comparative approaches is illustrated in detail using research data provided by the U.S. EPA on ICPMS Method 1638 for cadmium in reagent water.