Journal of Analytical Toxicology, Vot, 14, September/October 1990 Precision and Accuracy in the Quantitation of Carboxytetrahydrocannibinol by Isotope Dilution Gas

The classical definitions of method detection limit (MDL) and limit of quantltatlon (LOQ) are redefined using caUbration curve regression analysis. Traditional ways of determining these parameters provide scant Information on the daily preclslon of the analysis at all concentration levels. These parameters are time consuming to acquire and hold only for the moment of acquisition. It Is illustrated, with experimental data, using isotope dilution analyses of THC-COOH, a marijuana metabollte, that not only can MDL and LOQ be obtained directly from the calibration curve, but confidence Intervals for the calibration curve can also be obtained, which define the precision of the analyses at all levels calibrated. If calibration and analyses of unknowns take place simultaneously, then an MOL and confidence intervals that are relevant to data acqufsitton are obtained. Confidenc