Methods for Measuring Lead Concentrations in Paint Films

摘要

Recent legislation required the U.S. Department of Housing and Urban Development (HUD) to establish procedures to abate lead-based paint in existing HUD-assisted housing. The legislation also required HUD to assess the accuracy, precision, reliability, and safety of methods for measuring lead content of paint films and to investigate the availability of testers and samplers. The National Institute of Standards and Technology was requested to carry out the assessment. With regard to accuracy and precision of field measurements, it was concluded that: chemical spot tests when carried out by an experienced analytical chemistry technician can detect the presence of lead in paint films having concentrations in excess of 1 mg/sq cm about 90% of the time; the estimate of the precision of a field measurement procedure using lead-specific portable X-ray fluorescence (XRF) analyzers for lead concentrations near 1 mg/sq cm is + or - 0.6 mg/sq cm and the estimate of the bias is 0.2 mg/sq cm; this results in a 95% confidence interval of + or - 1.4 mg/sq cm; and based upon very preliminary measurements using the latest version of the spectrum analyzer portable XRF, the 95% confidence interval for field measurements is estimated to be + or - 0.5 mg/sq cm. In addition to field methods, standard laboratory procedures can be used to measure the lead content of paint samples to within a few percent of the quantity present over a wide range extending from less than 0.1 to over 10 mg/sq cm. Sample collection and sample dissolution procedures were also investigated.