For screening purposes, can an XRF be used instead of laboratory analysis for metals soil samples and how should the data be evaluated?
If XRF data is collected, the size of the data set needs to be considered. Typically, at least 10% of all samples analyzed using an XRF should also be laboratory analyzed to ensure the quality of the XRF results and reliability of the data (this does not preclude the evaluation of 20% of the samples collected for the lead finer fraction analysis explained above). DEQ recommends that samples selected for laboratory analysis be focused around data that is near the action level, with a minimum of 25% of the XRF high and low range concentration samples sent to the laboratory for analysis. For smaller data sets, laboratory analysis only may be more appropriate. The relative percent difference (RPD) of each XRF/laboratory sample pair should be calculated. The average RPD of the XRF/laboratory sample pairs should not exceed 35% (per EPA National Functional Guidelines for Inorganic Data Review, October 2004). A graph showing the correlation between the XRF and laboratory results should be prov
