Decision limit, trace analysis

When the analysis is complete, the analyst must translate the results into terms that can be understood by others. A most important feature of any result is its limitations. What is the statistical uncertainty in reported results If you took samples in a different manner, would you obtain the same results Is a tiny amount (a trace) of analyte found in a sample really there or is it contamination Once all interested parties understand the results and their limitations, then people can draw conclusions and reach decisions. 

Historically, the simple ka criteria used in Figure 2 are based on numerous simplifications. They are usually based on the standard deviation a of blank value measurements The limit of decision is defined with A = 3. the limit of detection with A = 6, and as one possibility, the limit of quantitation with k= 10 [16). (The k values take into consideration the probability ot of erroneous statistical and, therefore, erroneous analytical decisions. Thus, by fixing k or a, the purpose of the particular trace-analytical procedure can be taken into account.) The basic considerations in such definitions of method limits extend back to H. Kaiser (I4J and G. Ehrlich [17], Kaiser also tried to define characteristic quantities of methods for multicomponent analysis. For reasons of space, simultaneous multicomponent analysis cannot be discussed here [ 18]. [ 19]. The previous discussion reveals how delicate results of trace analyses are in general. To achieve a re.sponsible discussion in public it should be at least reported together with... 

This statistical error is still present even when the element in question occurs in amounts well above the limit of detection.. .. It is, however, fair to add that activation analysis is only used for macro-determination when speed and convenience, rather than sensitivity, are decisive. So far, the main uses of the technique have been in microdetermination of elements close to—or beyond—the limits of sensitivity offered by other methods. Though several elements can often be determined in a single sample, it is generally not possible to obtain a complete survey of all trace constituents, as can for example be expected from spectrographic analysis. 

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