Evaluation of Approximate Methods for Calculating the Limit of Detection and Limit of Quantification

In a previous paper, a computational method was presented for determining statistically rigorous limits of detection and quantification. The main purpose of this study is to evaluate similar but less computationally complex methods. These “approximate” methods use data at multiple spiking concentrations, are iterative, can be derived from either prediction intervals or statistical tolerance intervals, and require at a minimum ordinary least-squares regression for calculating the intercept and slope. Approximate detection and quantification limits calculated for various PCB congeners were similar to those calculated using the computationally exact method. Although the exact methods should be employed whenever possible (they include uncertainty in the calibration function and provide greater weight to less variable data), approximate methods can provide detection and quantification limits that are sufficiently accurate for most applications. Practical application of multiconcentration-based methods may involve the use of routinely generated quality control data in the statistical calculations.