Uncertainty determination for nondestructive chemical analytical methods using field data and application to XRF analysis for lead.

Air sampling and analytical methods are developed to provide a basis for decision making. They are evaluated in the laboratory against prescribed fitness-for-use criteria even though laboratory validation does not take into account all possible sources of uncertainty in field application. Field evaluation would be preferable but is complicated by the lack of controlled conditions, which limits the ability to compare analytical methods and to recognize outliers and assess variance homogeneity across the range of interest.