- Author
- Rossiter, W. J., Jr. | Vangel, M. G. | McKnight, M. E. | Signor, A. | Byrd, W. E.
- Title
- Ultrasonic Extraction/Anodic Stripping Voltammetry for Determining Lead in Household Paint: A Laboratory Evaluation.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Sponsor
- Department of Housing and Urban Development, Washington, DC
- Report
- NISTIR 6571, April 2001, 64 p.
- Keywords
- paints | lead | anodic stripping voltammetry (ASV) | lead-based paint | lead recovery | overlayer effect testing | ultrasonic extraction (UE)
- Abstract
- A laboratory study was conducted to evaluate the reliability of commercial, field-portable ultrasonic extraction-anodic stripping voltammetry (UE/ASV) for determining the lead levels of laboratory-prepared paint films when tests were performed by certified lead inspectors trained to conduct UE/ASV testing. Two factory-calibrated UE/ASV apparatuses from the same supplier were purchased and used to conduct an experiment investigating the effects of lead level, apparatus, lead pigment type, operator, paint-film substrate, and overlayer applied to the lead-based paint film. Test panels, with either white lead (i.e., basic lead carbonate) or lead chromate pigments, had 10 lead levels ranging from 0 mg/cm2 to 3.5 mg/cm2. The lead-based paint films were adhered to steel or plaster substrates, which were considered for experimental design purposes to be difficult or easy to sample, respectively. The overlayers were either a thickly applied oil-based paint (about 0.75 mm to 1.4 mm) or a thinly applied latex paint (about 0.13 mm to 0.28 mm). The five operators were trained by a UE/ASV supplier's representative to conduct the tests using a written protocol developed from the supplier's instructions. The study showed that one of the two ASV electrochemical instruments was in calibration, whereas the response of the second ASV instrument was low at the lower lead concentrations used to check calibration. Consequently, the data were analyzed both as "unadjusted for calibration" and "adjusted for calibration." Lead levels determined by the UE/ASV tests were often considerably less than the lead levels in the test panels. Depending on the combination of five experimental factors-apparatus, operator, lead pigment type, substrate type, and overlayer-the recovered lead for the data adjusted for calibration ranged from 28% to 94%, with the median recovery being 63%. These findings are in sharp contrast with previously published results of an UE/ASV field study in which lead recoveries generally ranged from 75% to more than 100%. In the present study, ASV measurement error did not appear to play a role in the low lead recoveries based on quality assurance measures. A key contributor appeared to be incomplete lead solubilization during paint specimen sonication. The major experimental factor affecting UE/ASV response was overlayer, with test panels having thick-oil overlayers yielding lower lead recoveries than those with thin-latex overlayers. It may have been that thick-oil overlayers were more difficult to sonicate, and/or grind before sonication, than thin-latex overlayers. Effects of the other experimental factors on UE/ASV response were considered primarily for the calibration-adjusted data. Operator and substrate factors were found to have a significant effect; whereas no effects were found for lead pigment type or apparatus.