Analytical Methodologies with Very Low Blank Levels: Implications for Practical and Empirical Evaluations of the Limit of Detection

Limit of detection criteria in analytical chemistry are regularly specified in terms of the distribution of the measured blank response. The consequences of an analytical blank response with a negligible distribution of measured values on the calculation and significance of limit of detection criteria receive scarce attention. A consideration of a hypothetical analytical methodology where the blank response is zero and the distribution of blank values is negligible is described. The impact of this situation on the traditional limit of detection criteria and on calibration relationships is discussed in detail. A simple, empirical method of estimating indicative method detection limits based on whole-method repeatability is proffered. This model has been validated with experimental data.