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Factors Affecting Ultrasonic Extraction of Lead From Household Paint Films: Further Investigations.


pdf icon 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.