Accuracy in the Determination of Chlorinated Dibenzo-p-Dioxins and Dibenzofurans in Environmental Samples

Abstract

The analytical chemist involved in industrial trace analysis is frequently confronted with many varied problems. Programs to produce acceptable data can be divided into two classes depending upon the level of quality assurance that is required. Frequently, unvalidated analytical procedures can be used to generate data for screening programs or process control. On the other hand, validated methods with rigorous quality assurance guidelines are absolutely necessary for work involving product specifications, industrial hygiene, or regulatory matters. When the analyst is asked to develop a trace analytical method, he must determine the end-use of the data. There are many parameters which must be factored into the analytical method. The analyst would like to build into the method the highest achievable sensitivity, accuracy, and reliability; and the customer wants the lowest cost and fastest analysis time possible. We can see then, from a practical viewpoint, the method development begins with a series of compromises. When implemented properly, these compromises can improve the overall quality of the method. The American Chemical Society has published "Principles of Environmental Analysis" [Anal. Chem. 55, 2210 (1983)] to aid in designing analytical measurements on environmental samples. The relationship between the number of samples necessary to obtain data within a defined acceptable error, and the standard deviation of the method, is shown by the equation: