Factors affecting ultrasonic extraction of lead from laboratory-prepared household paint films

et al. 2003

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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 45 °C 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 μm mesh sieve), and sonication temperature and sonication time were 45 °C and 30 min, respectively, lead recovery was quantitative. When particle size was large (> 425 μm), lead recovery was quantitative only upon 65 °C 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 overcoated. 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 μm 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 45 °C and 30 min, as is presently carried out in common practice.

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Factors affecting ultrasonic extraction of lead from household paint films:

Rossiter¹,

Toman²,

et al. 2003

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Ultrasonic extractionanodic stripping voltammetry for determining lead in dust:

Rossiter¹,

Toman²,

et al. 2004

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Previously published laboratory studies have indicated that ultrasonic extraction/anodic stripping voltammetry (UE/ASV) may be suitable for quantitative field analysis of dust wipe samples. Nevertheless, on-site lead extraction and analysis of dust wipes by UE/ASV are not currently used in federal programs for controlling and abating lead hazards in housing. A reservation to adopting UE/ASV is that the effect of the field operator (i.e., the analyst) is unknown. The availability of a reliable field test procedure for determining the amount of lead in dust could allow for on-site extraction and analysis. Thus, the U.S. Department of Housing and Urban Development (HUD) sponsored a study to evaluate the effect of operator when certified lead risk assessors or inspectors, trained to conduct UE/ASV analyses, performed such analyses of laboratory-prepared dust wipe specimens using commercial, field-portable apparatus.Four operators analyzed 640 dust wipe specimens following a test protocol developed in accordance with the UE/ASV apparatus instructions. These specimens were prepared using four commercial wipes spiked with one of six lead-containing certified reference materials (CRMs). Six lead levels spanned a range from 0 µg to 2000 µg. After UE extraction, the solutions were either filtered or not filtered before conducting the ASV analyses. Key findings from these analyses were that lead recoveries were quite variable, ranging from < 20 % to > 100 % depending upon the combination of experimental variables, and only 42 % of the specimens spiked with a CRM afforded quantitative recovery defined as falling within the range of 100 % ± 20 %. When the entire data set was analyzed, all experimental variables had a significant effect on recovery. The majority of the twoway interaction effects were also significant. The operator effect was essentially associated with three of the four operators determining higher lead recoveries than the fourth. The three operators reporting the higher recoveries followed a test protocol that was a slight modification of that used by the fourth operator. It was not determined whether this modification accounted for the observed operator effect.To provide data regarding the role of extraction and ASV measurement in the low recoveries, the lead concentrations of a limited number of UE extracts were analyzed using inductively coupled plasma (ICP) atomic emission spectrometry. A key finding was that wipe type had an effect on lead recovery when determined using either ICP or ASV analyses of the UE extract solutions. In addition, one wipe may have produced an interferant(s) to ASV analysis.Based on the study results, a main conclusion is that the UE/ASV test procedure lacked robustness for analyzing dust wipe specimens. That is, it was found that changes in the experimental variables incorporated in the study design could lead to low lead recoveries. Future investigations should address improving robustness.

Ultrasonic extractionanodic stripping voltammetry for determining lead in dust:

Rossiter¹,

Toman²,

et al. 2004

Self Cite