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Factors Affecting Ultrasonic Extraction of Lead From Laboratory-Prepared Household Paint Films.


pdf icon Factors Affecting Ultrasonic Extraction of Lead From Laboratory-Prepared Household Paint Films. (351 K)
Rossiter, W. J., Jr.; Toman, B.; McKnight, M. E.; Anaraki, M. B.

NISTIR 6834; 48 p. May 2002.

Sponsor:

Department of Housing and Urban Development, Washington, DC

Keywords:

paints; extraction; lead; particle size; temperature; tests

Abstract:

In a previous National Institute of Standards and Technology (NIST) study on the reliability of ultrasonic extraction-anodic stripping voltammetry (UE/ ASV) for quantitatively determining lead in paint films, it was found that the amount of lead was often considerably less than the known lead levels of the specimens. An important contributor appeared to be incomplete lead solubilization during ultrasonication. This report presents the results of a follow-up study performed to examine factors affecting ultrasonic extraction of lead from laboratory-prepared paint films that had been characterized using common analytical methods. The current study had three phases. In Phase I, five experimental variables--sonicator power, specimen mass, specimen particle size, sonication temperature, and sonication time---were systematically examined in a controlled two-level experiment. Three significant main effects---particle size, temperature, and time---were identified. Two significant two-way interactions---particle size with temperature and particle size with time---were also observed. No three-way interactions were found. The effect of particle size was strong. When the particle size was small (425 mm), mean lead recovery was quantitative regardless of the conditions of sonication time and temperature. In contrast, when the particle size was large, only in the case relatively high temperature ('" 65DGC) and long time (90 min) was the mean recovery quantitative (i.e., 80 % and above). ]n Phase IT, ultrasonic extractions, conducted under temperature and time conditions found in Phase] to be most effective, were performed on specimens sampled from each of the 80 NIST paint-film panels. Lead recoveries were higher than the mean recoveries reported in the previous N]ST UE/ ASV study for each panel. ]n Phase III, lead extractions from specimens sampled from a limited number of NIST paint-film panels were performed without ultrasound using a water bath with mechanical stirring of the specimens in acid solution. The results were compared with those obtained when extraction was conducted using a sonicator. Lead recoveries with and without ultrasound were comparable for the same conditions of temperature and time. ]n conducting UE/ASV analysis of paint-film samples, small particle size of the ground specimen needs to be maintained.