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Published online by Cambridge University Press: 06 March 2019
Federal laws require that urban redevelopment projects characterize the Pb hazard of old painted surfaces. In large metropolitan surveys, the Pb analyses are commonly obtained with a portable XRF unit; however, for small surveys, capital investments in such instrumentation may be unwarranted. In 1988, the city of Las Cruces, NM, requested our help in providing needed Pb in paint analyses. We developed an economical XRF method for Pb analysis suitable for small scale urban surveys and the requirements of individual home owners, it is described below.
1) A standard wavelength dispersive XRF spectrometer is used to determine the CI countrate from a 3.6 cm KCl disk and the countrate per square cm is computed. 2) The paint chip is weighed to the nearest 0.1 mg and cemented onto the disk. 3) The prepared disk is counted for CI, Pb, and Rb using the same spectrometer. 4) The CI countrate deficit is used to compute the area of the paint chip. 5) The mass of Pb corrected for Rb interference is determined from an appropriate calibration curve, and the results are reported in mg Pb/cm2.
The Pb analysis is calibrated against geochemical standards. Spex Mix containing Pb is sprinkled on double faced mylar tape of known area and used as an independent check on the calibration curve. We present the results of our calibration curves and our analytical experience over the last 5 years.