Volume 9, Issue 5 (May 2012)
Statistical Comparison of Analysis Results for Lead on Dust Wipe Samples by X-ray Fluorescence Analysis and Flame Atomic Absorption Spectrometry
The traditional method of determining dust lead loading (mass per unit area) on surfaces is to send dust wipe samples to a laboratory for analysis, and typically it takes one or more days to obtain results. Field-portable techniques taking 10 to 15 min for dust wipe lead analysis have been developed but need to be further evaluated. Dust wipe samples (n = 878) collected from a nationally representative sample of child care centers were tested by means of x-ray fluorescence (XRF) analysis with two XRF analyzer instrument models and subsequently analyzed for lead using flame atomic absorption spectrometry (FAAS). Samples were collected from floors and interior window sills and included blank and spiked quality control samples. Weighted linear regression was used to model the relationship between XRF and FAAS measurements. The correlations between FAAS and XRF measurements exceeded 0.80 (p < 0.0001). The highly significant statistical correlation suggests that the XRF method could be used to quantify dust lead loadings to determine compliance with dust lead hazard standards as defined by the U.S. Environmental Protection Agency. Small, but significant, differences in regression parameters were found between floor or sill and quality control sample types. The use of 95 % prediction intervals could allow for rapid screening of clearance samples in the field if method standards were developed. Additional work is needed in order for researchers to understand differences among XRF instruments and the conditions under which the use of XRF testing in the field could reduce the time or cost required in order to complete clearance testing.