A portable x-ray fluorescence instrument for analyzing dust wipe samples for lead: Evaluation with field samples

Dust wipe samples collected in the field were tested by nondestructive X-ra y ftuorescence (XRF followed by laboratory analysis with flame atomic absor ption spectrophotometry (FAAS). Data were analyzed for precision and accura cy of measurement. Replicate samples with the XRF show high precision with an intraclass correlation coefficient (ICC) of 0.97 ( P< 0.0001) and an ove rall coefficient of variation of 11.6%. Paired comparison indicates no stat istical difference (P = 0.272) between XRF and FAAS analysis. Paired sample s are highly correlated with an R-2 ranging between 0.89 for samples that c ontain paint chips and 0.93 for samples that do not contain paint chips. Th e ICC for absolute agreement between XRF and laboratory results was 0.95 (P <0.0001). The relative error over the concentration range of 25 to 14,200 m u g Pb is -12% (95% CI, -18 to -5). The XRF appears to be an excellent meth od for rapid on-site evaluation of dust wipes for clearance and risk assess ment purposes, although there are indications of some confounding when pain t chips are present. (C) 2000 Academic Press.