Factors Affecting Ultrasonic Extraction of Lead From Household Paint Films: Further Investigations.
Factors Affecting Ultrasonic Extraction of Lead From
Household Paint Films: Further Investigations.
(213 K)
Rossiter, W. J., Jr.; Toman, B.; McKnight, M. E.;
Emenanjo, I.; Anaraki, M. B.
NISTIR 6948; 33 p. March 2003.
Sponsor:
Department of Housing and Urban Development, Washington,
DC
Keywords:
paints; extraction; lead; particle size; temperature;
tests; investigations
Abstract:
Previous studies at NIST on the use of ultrasonic
extraction/anodic stripping voltammetry (UE/ASV) for
determining lead in household paint found that the
particle size of the ground specimen plays an important
role in lead extraction efficiency, particularly when
the extraction is performed under the commonly used
sonication conditions of 45DGC and 30 min. Consequently,
it was proposed that, in conducting an UE/ASV analysis
of a paint-film specimen in the field, the specimen
particle size should be estimated prior to selecting an
appropriate combination of sonication temperature and
time. This report presents the results of a follow-up
study performed to evaluate the reliability and
practicality of the particle size recommendation. In
the laboratory phase, specimens from lead-containing
paint-film panels were prepared using 16 commercial
paints and analyzed using UE/ASV. Experimental variables
were: grinding method, sonication temperature,
sonication time, paint manufacturer, paint type, gloss
level, and binder type. The laboratory-prepared
paint-film specimens were difficult to grind manually.
The combination of specimen particle size, sonication
temperature and sonication time had a highly significant
effect on UE/ ASV lead extraction efficiency. When
particle size was small (passing through a No. 40, 425
mm mesh sieve), and sonication temperature and
sonication time were 45DGC and 30 min, respectively, lead
recovery was quantitative. When particle size was large
(> 425 mm), lead recovery was quantitative only upon
65DGC and 90 min extractions. Paint manufacturer, paint
type, gloss level, and binder type generally had little
or no effect on UE/ASV lead recovery. In the field
phase, NIST research staff and four certified lead
inspectors and risk assessors (i.e., operators) trained
to perform UE/ASV analyses sampled lead-containing paint
from houses and similar buildings. The field samples
included older lead-containing paint films that had been
recently overcoat. Such samples were taken to determine
whether they would be difficult to grind manually into
small particles. It was found in the laboratory that
manual grinding of the dry ice cooled field specimens
readily produced a powder. Appropriate conditions of
temperature and time for extracting lead from the field
specimens were successfully selected by visually
comparing the particle size of the ground specimens
against that of a black pepper reference powder (i.e.,
known to pass through a No. 40, 425 mm mesh sieve).
Estimating particle size through sieve analyses of
ground field specimens did not result in selecting
appropriate extraction temperature and time. It was
recommended that, if a ground specimen appears to have
adequately small particle size when compared against
that of a reference powder, then extraction during a
UE/ASV analysis may be performed at 45DGC and 30 min, as
is presently carried out in common practice.
