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