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Estimating Detection Limits in Ultratrace Analysis. Part I: The Variability of Estimated Detection Limits

Volume 45, Number 8 (Oct. 1991) Page 1217-1224

Stevenson, Christopher L.; Winefordner, James D.


The limit of detection (LOD) of a trace analytical method is often used as a gauge of the sensitivity of the method. Improvements and comparisons of similar methods usually involve comparisons of the LODs. However, the calculated LOD value is sensitive to a number of factors such as the method of calculation used, the choice of calibration standards, and the number background (blank) measurements. In this paper, the calculated LOD of a particular analytical method is viewed as an estimate of the true, unknown LOD. Factors which affect the variability of the estimate are investigated. Knowledge of the variability of the estimated LOD can help when analytical methods are being compared on the basis of LOD values. In addition, by knowing which experimental factors contribute to the uncertainty in the calculated LOD, it is possible to determine the analytical protocol which estimates the true LOD most efficiently with no loss in precision.