Ultrasonic Extraction/Anodic

Stripping Voltammetry for

Determining Lead in Dust:

Analyses of Field-Sampled Wipes

Walter J. Rossiter, Jr.

Blaza Toman

Mary E. McKnight

Ijeoma Emenanjo

Prepared for:

U.S. Department of Housing and Urban Development

Office of Healthy Homes and Lead Hazard Control

NISTIR 7109
 

NISTIR 7109

Ultrasonic Extraction/Anodic

Stripping Voltammetry for

Determining Lead in Dust:

Analyses of Field-Sampled Wipes

Walter J. Rossiter, Jr.*

Blaza Toman**

Mary E. McKnight*

Ijeoma Emenanjo*

*

Building and Fire Research Laboratory

**Information Technology Laboratory

National Institute of Standards and Technology

Gaithersburg, MD 20899-8615

 October 2004

Prepared for:

U.S. Department of Housing and Urban Development

Alphonso Jackson, Secretary

Office of Healthy Homes and Lead Hazard Control

Joseph F. Smith, Deputy Director

U.S. Department of Commerce

Donald L. Evans, Secretary

Technology Administration

Phillip J. Bond, Under Secretary for Technology

National Institute of Standards and Technology

Arden L. Bement, Jr., Director
iii

ABSTRACT 

Knowledge of the amount of lead in settled dust is important in clearance examinations, risk 

assessments, and related activities wherein decisions are made regarding lead hazards in houses and 

related buildings. At present, analyses of lead in dust are normally performed in laboratories, since 

quantitative methods are not readily field-portable. In recent years, field portable ultrasonic 

extraction/anodic stripping voltammetry (UE/ASV) has been suggested as a candidate procedure for 

field analysis of dust wipe specimens. However, the reliability of UE/ASV analyses of field dust 

wipe specimens has not been demonstrated. The present study compared the results of ASV 

analyses of UE extracted field-sampled dust wipes against those of inductively coupled plasma 

(ICP) atomic emission spectrometry analyses of the same extract solutions. The main objective of 

the study was to investigate whether lead in dust wipe specimens obtained in the field can be 

efficiently and effectively extracted, and reliably quantified using common UE/ASV field 

procedures when the analyses are performed by certified risk assessors. The U.S. Department of 

Housing and Urban Development (HUD) sponsored the research because of the benefits to be 

gained in having available a reliable, practical method for on-site analysis of lead in dust in houses 

and related buildings. 

In a preliminary laboratory phase, data on the use of an ICP procedure for estimating the true values 

of lead in dust wipe specimens were obtained. Experimental variables were: dust wipe, leadcontaining certified reference material (CRM), specimen lead level, and filter treatment (i.e., 

filtering versus no filtering) of the UE extracts before ASV analyses. Lead recoveries determined 

by both ASV and ICP analyses were compared. The effects of wipe and lead level were significant, 

whereas the effects of CRM and filter treatment were insignificant. All ICP recoveries were 

quantitative (100 % ± 20 % of the lead applied to the wipe), whereas only 72 % of the ASV 

measurements were quantitative. 

In the field phase, NIST research staff along with three certified lead risk assessors, who had 

participated in a previous NIST dust wipe study, sampled lead-containing dust from houses using 

the same dust wipe products used in the laboratory phase. Three experimental variables were 

examined: operator, wipe, and filter treatment of the UE extract. Percent lead recoveries by ASV 

analysis were calculated relative to the lead contents determined by ICP; 88 % of the recoveries 

were quantitative. None of the three variables was significant when the entire data set was 

considered. A filter treatment effect was present for a data subset comprised of specimens found to 

have less-than-500 μg of lead. Based on analyses of the entire data set and also on the less-than500 μg data subset, the probabilities of a future ASV analysis yielding a result within ± 25 % of an 

ICP result were estimated to be 0.93 and 0.96, respectively. A recommendation for increasing the 

efficacy of the UE/ASV protocol is given. 

Key words: anodic stripping voltammetry (ASV); building technology; dust wipes; field study; 

lead-containing dust; lead recovery; operator effect; testing; ultrasonic extraction (UE) 
iv

TABLE OF CONTENTS 

Page

ABSTRACT..... ................................................................................................................................. iii

1. INTRODUCTION...........................................................................................................................1 

1.1 Background ............................................................................................................................1 

1.2 Objective and Scope...............................................................................................................2

2. EXPERIMENTAL ..........................................................................................................................2 

2.1 UE/ASV Apparatus ................................................................................................................2 

2.1.1 ASV Instrument..........................................................................................................2

2.1.2 Sonicator.....................................................................................................................3 

2.2 UE/ASV Dust Wipe Protocol.................................................................................................3

2.3 Dust Wipe Specimens ............................................................................................................3 

2.3.1 Laboratory-Prepared Specimens ................................................................................3 

2.3.2 Field Specimens .........................................................................................................5

3. RESULTS, ANALYSIS, AND DISCUSSION...............................................................................6 

3.1 Laboratory-Prepared Specimens ............................................................................................6 

3.1.1 Effect of Wipe, CRM, Lead Level, and Filter Treatment ..........................................6 

3.1.2 Effect of Analytical Method.......................................................................................9 

3.2 Field Specimens ...................................................................................................................12 

3.2.1 Ultrasonic Extraction................................................................................................12 

3.2.2 UE/ASV Lead Content.............................................................................................12 

3.2.3 Lead Recovery..........................................................................................................15

3.2.4 Comparison with the NIOSH Criterion....................................................................16 

3.3 Future Work .........................................................................................................................16

4. SUMMARY AND CONCLUSIONS............................................................................................16

5. ACKNOWLEDGMENTS.............................................................................................................18

6. REFERENCES..............................................................................................................................18

APPENDIX A. UE/ASV DATA......................................................................................................A1

APPENDIX B. REGRESSION PLOTS COMPARING ASV AND ICP FIELD SPECIMEN 

RESULTS BY OPERATOR................................................................................... B1 
v

LIST OF TABLES 

Page

Table 1. Certified reference materials (CRMs) used in the laboratory phase .....................................4

Table 2. Combinations of CRMs, wipes, and lead levels used in the preparation of the 

laboratory dust wipe specimens.............................................................................................4

Table 3. Analysis of variance examining effect of wipe, CRM, lead level, and filter treatment 

for the laboratory-prepared specimens ..................................................................................6

Table 4. Percentage of analyses providing quantitative lead recovery in the current and 

previous NIST studies ...........................................................................................................7

Table 5. Analysis of variance examining effect of analytical method on lead recoveries for the 

laboratory-prepared specimens, as determined by ASV and ICP .........................................9

Table 6. Analysis of variance examining effect of operator, wipe, and filter treatment for the 

field specimens ....................................................................................................................13

Table 7. Linear regression analysis coefficients for the ASV versus ICP comparison for all 

field data ..............................................................................................................................15

Table A1. Results of lead analyses of laboratory specimens prepared using Wipe 2......................A1

Table A2. Results of lead analyses of laboratory specimens prepared using Wipe 3......................A2

Table A3. Results of lead analyses of laboratory specimens prepared using Wipe 4......................A3

Table A4. Results of lead analyses of NIST field specimens ..........................................................A4

Table A5. Results of lead analyses of Operator 2 field specimens ..................................................A5

Table A6. Results of lead analyses of Operator 3 field specimens ..................................................A6

Table A7. Results of lead analyses of Operator 4 field specimens ..................................................A7

Table B1. Linear regression analysis coefficients for the ASV versus ICP comparisons 

by operator....................................................................................................................... B1 
vi

LIST OF FIGURES 

Page

Figure 1. Laboratory-Prepared Specimens: The Effect of Filtering of the UE Extract on 

ASV Lead Recovery by Wipe, CRM, and Lead Level (LL) ...............................................8

Figure 2. Laboratory-Prepared Specimens: ASV Recovery Versus ICP Recovery by Wipe, 

CRM, and Lead Level (LL) ...............................................................................................10

Figure 3. Laboratory-Prepared Specimens: Amount of Lead Measured by ASV Versus That 

Determined by ICP for Specimens Prepared Using Wipes 2, 3, and 4..............................11

Figure 4. Field Specimens: Lead Content Determined by ASV Analyses of Filtered and 

Unfiltered UE Extracts for Each Operator.........................................................................13

Figure 5. Field Specimens: ASV Results Versus ICP Results..........................................................14

Figure 6. Field Specimens: Percent ASV Lead Recovery.................................................................15

Figure B1. Field Specimens: ASV Results Versus ICP Results by Operator................................... B2 
1

1. INTRODUCTION 

1.1 Background

A major potential source of lead exposure, particularly for young children, is lead in dust [1]. 

Consequently, quantitative analysis to determine the amount of lead in dust is important for 

identifying and controlling lead hazards in houses and related buildings. At present, analyses of 

lead in dust are normally performed in laboratories, since quantitative methods are not readily fieldportable. The availability of a reliable, practical field test procedure for analyzing lead in dust 

would be beneficial in expediting decisions regarding identification of dust lead hazards or safe 

reentry of housing subjected to lead hazard abatement. 

Sampling of settled dust is generally performed by manually wiping a surface with a disposable 

towellette, called a dust wipe, that has been pre-moistened with a wetting agent. The dust wipe is 

then sent to a laboratory. Soluble lead is extracted and the extract solution is analyzed for lead 

using a method such as inductively coupled plasma atomic emission spectrometry (ICP-AES) or 

atomic absorption spectrometry (AAS). ASTM E 1728, “Standard Practice for Collection of Settled 

Dust Samples Using Wipe Sampling Methods for Subsequent Lead Determination,” describes 

standardized surface-wiping methods [2]. ASTM E 1792, “Standard Specification for Wipe 

Sampling Materials for Lead in Surface Dust,” sets performance requirements for dust wipes [3]. 

Field portable ultrasonic extraction/anodic stripping voltammetry (UE/ASV) has been suggested as 

a candidate procedure for field analysis of dust wipe specimens. UE/ASV studies performed using 

laboratory-prepared dust wipe specimens generally have shown that lead was quantitatively 

analyzed (i.e., recoveries were in the range of 100 % ± 20 %) [4-7]. However, the study by Ashley, 

Wise, Mercado, and Parry [5] also demonstrated limitations to the UE/ASV dust wipe methodology. 

Specifically, they found that only three of the four wipes studied were suitable for analysis by 

UE/ASV. Also, for some wipes, the UE extract solutions needed to be filtered before ASV 

analysis. 

Recently, the National Institute of Standards and Technology (NIST) reported on the results of an 

UE/ASV study [8] that was conducted mainly to examine the effect of the operator on lead recovery 

from dust wipe specimens. In addition to studying operator effect, four other variables were 

examined: wipe, the lead-containing Certified Reference Material (CRM)* applied to the wipe, lead 

level of the dust wipe specimen, and filter treatment of the UE extract. A key finding was that lead 

recoveries were variable, ranging from < 20 % to quantitative depending upon the combination of 

experimental variables. All experimental variables had a significant effect on recovery, as did many 

of the two-way interactions. Three of the four operators obtained significantly higher lead 

recoveries than did the fourth operator. In this case, the fourth operator used a different test 

procedure than the other three. Two of the four wipes provided significantly higher recoveries than 

the other two. These results were consistent with those of Ashley et al. [5], who found variable lead 

recovery depending upon the combination of wipe and CRM. 

UE/ASV analyses of field-sampled dust wipes have not been validated against measurements 

performed using a reference method such as ICP. This present study compares the results of ASV 

and ICP measurements of solutions obtained by ultrasonic extraction of field-sampled dust wipes. 

 

*

 A Certified Reference Material is “a reference material accompanied by a certificate, one or more of whose property 

values are certified by a procedure that establishes its traceability to an accurate realization of the unit in which the 

property values are expressed” [9]. CRM is the generic term used in this report to denote all certified reference 

materials including NIST Standard Reference Materials (SRMs). 
2

The majority of the field sampling and UE/ASV analyses were performed by certified risk assessors 

as such individuals would be expected to perform UE/ASV field analyses. The research was 

sponsored by the U.S. Department of Housing and Urban Development (HUD). At present, on-site 

dust analysis is not integral to federal programs for identifying, abating, and controlling lead 

hazards associated with lead in paint, dust, and soil in housing. This limitation could be reviewed if 

a practical field test procedure for determining lead in dust is available. 

 

1.2 Objective and Scope

The main objective of the study was to investigate whether lead in dust wipe specimens sampled 

from housing can be efficiently and effectively extracted, and reliably quantified using common 

UE/ASV field procedures when the analyses are performed by certified risk assessors. A second 

objective was to compare the results of ASV and ICP measurements performed on UE extracts of 

dust wipe specimens. The study was performed in two phases: a laboratory phase and a field phase. 

The laboratory phase was conducted to develop experience under idealized experimental conditions 

on using ICP analysis for estimating the true value of lead in dust wipe specimens, because ICP was 

selected as the reference test method to estimate the true lead values of the field specimens. In the 

laboratory phase, lead-containing dust wipe specimens were prepared using some of the same 

commercial dust wipe products and lead-containing CRMs used in the previous NIST dust wipe 

study [8] (See Section 2.3.1). NIST research staff conducted the UE/ASV analyses on these 

laboratory specimens. In the field phase, NIST research staff along with three certified lead risk 

assessors, who had participated in the previous NIST dust wipe study, sampled dust from houses 

with the same dust wipe products that were used in the laboratory phase of the study. The field dust 

wipe samples were brought to the NIST laboratories for UE/ASV analysis by the individual 

performing the field sampling. For both the laboratory and field specimens, the reliability of the 

UE/ASV method for determining lead in dust wipe specimens was examined by evaluating whether 

measured lead recoveries were quantitative; that is, were the lead recoveries within ± 20 % of the 

estimated true lead values. Determination of quantitative recovery has been used by others in 

judging the reliability of UE/ASV for analysis of lead in environmental media [5,10]. Also for the 

field specimens, UE/ASV reliability was examined vis-à-vis a National Institute for Occupational 

Safety and Health (NIOSH) criterion that “a method must give a result that is within ± 25 % of the 

true concentration value at least 95 % of the time” [11]. 

2. EXPERIMENTAL 

2.1 UE/ASV Apparatus

A commercial, field-portable UE/ASV apparatus was used in the study. 

 

2.1.1 ASV Instrument. The field-portable ASV instrument is battery operated, uses disposable 

electrodes, and was factory-calibrated. The lead content output is in units of micrograms (μg). The 

range of detection for lead in dust wipe specimens reported in the ASV instruction booklet is 25 μg 

to 1500 μg. For UE extracts found to have lead levels exceeding 1500 μg, dilution of the extract 

using 7.5 % nitric acid is performed before ASV re-analysis. The uncertainty of the ASV 

measurements, taken as the pooled standard deviation for mean lead recoveries determined for 

specimens prepared using six CRMs*

 but without a dust wipe present, was estimated to be 7 % [8]. 

 

*

 A minimum of six specimens was analyzed for each CRM. 
3

Factory calibration of the ASV instrument was checked at the beginning of the study against eight 

standardized lead nitrate solutions of 7.5 % volume fraction nitric acid having lead contents ranging 

from 1 mg/L to 50 mg/L. The instrument remained in calibration, and the ASV response versus 

lead concentration was linear (r2

 = 0.998). In addition, at the beginning and end of each day’s 

analyses, operators rechecked the instrument calibration using two standardized solutions of lead 

nitrate (7.5 % volume fraction nitric acid with lead contents of 1 mg/L and 28 mg/L). These daily 

checks indicated that the ASV instrument remained in calibration throughout the study, and that 

instrument drift over the course of the day did not occur. 

2.1.2 Sonicator. The sonicator*

 is specified as having an average power of 45 W. The bath 

dimensions are 146 mm by 133 mm by 100 mm (length, width, and depth). 

2.2 UE/ASV Dust Wipe Protocol

All UE/ASV analyses were conducted in the NIST laboratories. The dust wipe test protocol was in 

accordance with the UE/ASV apparatus instructions. This protocol, which has been previously 

described [8], involves the following steps: 

• pushing the dust wipe specimen into 15 mL of 25 % volume fraction nitric acid in a 50 mL 

plastic screw-capped centrifuge tube using a disposable plastic stirring rod, 

• rotating and tumbling the dust wipe specimen in the acid with the plastic stirring rod until trapped 

air bubbles in the wipe are apparently released and the wipe is well wetted, 

• extracting the specimen for 30 min using the sonicator at an initial water bath temperature of 

45 °C ± 3 °C, 

• briefly suspending sonication to re-rotate and re-tumble the dust wipe specimen in the acid using 

the plastic stirring rod, 

• extracting the specimen for an additional 15 min at 45 °C ± 3 °C using the sonicator, 

• diluting the extract to 50 mL with water, and 

• analyzing the resultant solution for lead using ASV. 

Note that the initial 45 °C sonicator bath temperature deviated from the UE/ASV apparatus 

instructions, which prescribed water at room temperature. Water heated to 45 °C (taken from a 

laboratory tap) was used based on previous NIST results showing that UE/ASV lead recovery from 

laboratory-prepared paint film specimens is enhanced at higher bath temperatures [12]. 

2.3 Dust Wipe Specimens

2.3.1 Laboratory-Prepared Specimens. Two CRMs, each at three lead levels, and three commercial, 

individually packaged dust wipe products were used in preparing the laboratory specimens. The 

CRMs were SRM 2581 (NIST) at lead levels of 90 μg, 250 μg, and 500 μg, and CRM 01450 

(Resource Technology Corp, Laramie, WY; available through Fisher)† at lead levels of 40 μg, 

 

*

 In a previous NIST UE/ASV study [12], aqueous acidic extractions of lead-containing specimens from a limited 

number of paint-film panels, and also from reference material samples, gave comparable lead recoveries when 

performed with and without ultrasound under the same conditions of temperature and time. It has been recommended 

[12] that sonicators be used for lead extraction in the field, because they provide a practical and affordable means for 

agitating and heating specimens during lead extraction. Consequently, a sonicator was used in this study. Studies have 

not been reported comparing the results of aqueous acidic extractions of lead-containing dust-wipe specimens 

performed with and without sonication. 

†

 Certain trade names or company products are mentioned in the text to specify adequately the test specimens, 

experimental procedure and equipment used. In no case does such identification imply recommendation or 
4

250 μg, and 500 μg. These two CRMs were included in the previous NIST UE/ASV dust wipe 

study [8]. Both CRMs have been found to provide quantitative recovery when analyzed neat (i.e., 

no dust wipe was present) without filtering of the extract UE solution (Table 1). 

The selection of the three dust wipes in this study was based on their performance in the previous 

NIST study [8]. Specifically, for three of the four operators, 96 % of the Wipe 2, 3, and 4 

specimens subjected to UE followed by ICP analysis afforded quantitative lead recovery*†. In 

contrast, only 13 % of the Wipe 1 specimens analyzed using UE/ICP showed quantitative lead 

recovery. Wipe 1 was not included in the present study. The suppliers of Wipes 2, 3, and 4 

had reported [8] that these products conformed to the requirements of ASTM E 1792. 

In the laboratory phase of the study, four replicate specimens were prepared for each combination 

of CRM, wipe, and lead level (Table 2) for a total of 72 specimens. The dust wipe preparation 

procedure was developed by the Research Triangle Institute (RTI) and used in the previous NIST 

study [8]. Thus, an appropriate amount of CRM as specified in the experimental design was 

deposited onto a wipe. One analytical balance was used for all weighing. The calibration of the 

balance was checked before and after each weighing period using either a 50 μg or a 100 μg Class 1 

weight. Rubber gloves were worn throughout the procedure. In initiating the procedure, the bulk 

Table 1. Certified reference materials (CRMs) used in the laboratory phase 

Certified Reference Material Results of UE/ASV Analysesa 

 Lead Mass Fraction Lead Recovery, % CoVd

Designation Material Type % nb Min Max Mean SDc % 

SRM 2581 Powdered Paint 0.449 6 83.9 92.8 89.3 3.0 3.3 

CRM 01450 Bag House Dust 0.1914 11 92.3 111.2 103.8 6.2 5.9 

a

 Analyses were performed on the CRM specimens prepared without dust wipes; UE extracts were not filtered. 

b

 Number of analyses. 

c

 Standard deviation. 

d

 Coefficient of variation (standard deviation/mean*100). 

 Table 2. Combinations of CRMs, wipes, and lead levels used in the preparation of 

 the laboratory dust wipe specimensa

 a

 Four specimens were prepared for each combination. 

 endorsement by the National Institute of Standards and Technology, nor does it imply that the equipment is the best 

available for the purpose. 

*

 This discussion is limited to three of the four operators, because the fourth operator used a different UE/ASV test 

protocol and achieved significantly lower lead recoveries than the other three operators [8]. 

†

 These dust wipe designations are the same as those used in the previous NIST dust wipe study [8]. 

 Lead Level, μg CRM

ID 

Lead in CRM

% Mass Fraction 

Wipe

No. LL1 LL2 LL3 

SRM 2581 0.449 2 90 250 500 

 3 90 250 500 

 4 90 250 500 

CRM 01450 0.1914 2 40 250 500 

 3 40 250 500 

 4 40 250 500 
5

container of CRM was tumbled several times, and floating dust in the container was allowed to 

settle before opening it. CRM was removed from the container using a spatula and transferred to a 

tared sheet of weighing paper. Wipes were prepared for receiving the CRM by opening the wipe 

packaging, removing the wet folded wipe, and reducing excess moisture in the wipe by hand 

squeezing. The wipe was then unfolded and briefly placed on a dry laboratory paper towel to soak 

up moisture. The wipe was then transferred to a flat plastic board for deposition of the CRM. The 

weighing paper containing the pre-weighed CRM was removed from the balance using tweezers 

and held over the unfolded wipe. By tilting the weighing paper, the CRM was allowed to slide onto 

the center of the wipe after which, while holding the weighing paper manually, it was tapped with 

the tweezers. The wipe was folded and placed in a 50 mL plastic centrifuge tube that was capped 

and labeled*

. 

The amount of lead in each dust wipe specimen (i.e., estimated true lead value) was taken as the 

mass of CRM deposited onto a wipe multiplied by the certified % mass fraction of lead in the CRM. 

Lead recovery (LR %) determined by UE/ASV (or UE/ICP) analyses of a laboratory-prepared dust 

wipe specimen was calculated as: 

 LR % = (UE/ASV Result/Estimated True Lead Value) x 100. (Eq. 1a) 

2.3.2 Field Specimens. NIST research staff along with three certified lead risk assessors (referred to 

as operators) followed the procedure in ASTM E 1728 [2] to obtain the field specimens from four 

vacant row houses in Baltimore, MD†. The houses were known to contain substantial amounts of 

lead and were awaiting rehabilitation. Little maintenance had been performed on the houses in 

recent years so that it was expected that wiping surfaces would pick up measurable amounts of lead. 

A total of 108 specimens were obtained: 36 by NIST research staff and 24 each by the three 

operators. Specimens were mainly sampled from interior window troughs and sills, and interior 

floors beneath windows and doors. 

The three operators had participated in the previous NIST dust wipe study and, at the time, had been 

designated Operator 2, Operator 3, and Operator 4‡ [8]. For comparison with the previous study, 

these operator designations were retained in the current study. When conducting the analyses of the 

24 field specimens, each operator also analyzed at least two control specimens prepared using 

CRM 01450 without a dust wipe present. 

2.3.2.1 Lead Content. The amount of lead (i.e., estimated true value) in each field specimen was 

unknown and needed to be determined by a reference test method. In this regard, after the UE/ASV 

analysis of a field specimen was performed, ICP lead analyses of both the UE extract solutions and 

the UE residues remaining in the centrifuge tubes (see Section 2.2) were conducted§

. For the ICP 

analyses of the UE extracts, a 20 mL aliquot of each extract solution was decanted from the residue 

and filtered through a disposable 0.45 μm hydrophilic polytetrafluoroethylene (PTFE) filter cassette 

(Millipore Millex LCR) using a disposable polypropylene syringe. The filtrate (i.e., UE extract 

solution) was placed in a capped vial and sent to a National Lead Laboratory Accreditation Program 

(NLLAP) [13] laboratory. The NLLAP laboratory performed the lead analysis using the ICP 

procedure prescribed by EPA Method 6010B [14]. 

 

*

 For specimens prepared without dust wipes, the weighed CRM was deposited directly into the centrifuge tube. 

†

 The dust specimens were collected according to the procedure in a 2003 proposed revision of ASTM E 1728. 

Subsequent to the field sampling, the revision was approved by ASTM International [2]. 

‡ The Operator designated as No. 1 in the previous study was not available to participate in the current study.

§

 The UE/ASV specimens in the laboratory-phase of the study were also subjected to the ICP reference procedure. 
6

For the ICP analyses of the UE residues, the extract solution remaining in each centrifuge tube after 

PTFE filtering of the 20 mL aliquot was decanted and vacuum-filtered through Whatman No. 40 

ashless filter paper. The PTFE filter was removed from its cassette and placed in the centrifuge 

tube along with the Whatman filter paper. The centrifuge tube was capped and sent to the NLLAP 

laboratory for lead analysis of its contents (i.e., residue and filters) using the hot plate digestion 

method prescribed by EPA Method 3050B [15] followed ICP analysis [14] of the digestion solution. 

For approximately 40 % of the laboratory and field specimens, the amount of lead in the residue and 

filters was less than the NLLAP laboratory’s ICP method-reporting limit (i.e., 20 μg). When the 

amounts of lead in the residues were reported by the NLLAP laboratory, 97 % ± 4 % (1 SD) of the 

lead was in the UE extract solutions. Accordingly, the true values of lead in the field specimens 

were estimated based on the NLLAP ICP lead contents determined for the UE extract solutions. 

The percent lead recovery (LR %) measured by a UE/ASV analysis of a field specimen was 

calculated as: 

 LR % = (UE/ASV Result/Estimated True Lead Value) x 100, (Eq. 1b) 

 where the estimated true lead value was based on the amount of lead in the 

 UE extract solution, as determined by NLLAP ICP analysis. 

3. RESULTS, ANALYSIS, AND DISCUSSION 

3.1 Laboratory-Prepared Specimens

Tables A1 through A3 present* the amount of lead (in μg) determined by ASV and ICP analyses of 

the UE extract solutions for specimens prepared using Wipes 2, 3, and 4, respectively. The ASV 

analyses were conducted on unfiltered or filtered UE extracts; the ICP analyses were performed 

only on filtered UE extracts. 

3.1.1 Effect of Wipe, CRM, Lead Level, and Filter Treatment. Because both filtered and unfiltered 

specimens of the same UE extracts were analyzed, repeated measures analysis of variance 

(ANOVA) [16] of the lead content data could be used to evaluate the effect of wipe, CRM, lead 

level, and filter treatment (Table 3). The effects of wipe and lead level were significant (p-value 

 Table 3. Analysis of variance examining effect of wipe, CRM, lead level, and filter 

 treatment for the laboratory-prepared specimens 

 Analysis Resulta

 

Parameter F-Value P-Value 

Wipe 12.65 < 0.0001 

CRM 1.92 0.1708 

Lead Level 93.69 < 0.0001 

Filter Treatment 1.08 0.3019 

Filter Treatment – Wipe 3.75 0.0289 

Filter Treatment – CRM 0.14 0.7107 

Filter Treatment – Lead Level 0.30 0.9128 

 a By convention, p-values less than 0.05 are considered to be statistically significant. Bold font is used to 

 denote significant p-values. 

 

*

 Raw data from all UE/ASV analyses are given in Appendix A. 
7

< 0.05). In contrast, those for CRM and filter treatment were not significant. There was a 

significant two-way interaction between filter treatment and wipe. 

The effects of wipe, CRM, lead level, and filter treatment are illustrated in Figure 1, which shows 

three bar plots representing lead recoveries for specimens prepared with Wipes 2, 3, and 4. As seen 

in Figure 1, lead recovery varied considerably, ranging from 32 % to quantitative depending on the 

combination of wipe, CRM and lead level. Seventy-two percent (72 %) of the recoveries were 

quantitative. In the previous NIST study [8], 71 % of the recoveries were quantitative for 

specimens prepared with Wipes 2, 3, and 4, and either SRM 2581 or CRM 01450. In each plot in 

Figure 1, a pair of adjoining bars having light and dark fills represents the effect of filter treatment 

for the same combination of CRM and lead level. Observe that, as expected from the ANOVA 

results, adjoining bars in each plot generally have comparable heights indicating the lack of a filter 

treatment effect. Observe also in Figure 1 that, for Wipe 4, two-thirds of the unfiltered extracts 

provided higher recoveries than the filtered extracts. This observation could explain the significant 

two-way interaction found between filter treatment and wipe (Table 3). The finding of higher 

recoveries for unfiltered extracts contrasts with previous NIST results [8] wherein 58 % of the 

filtered extracts from Wipe 4 specimens spiked with either SRM 2581 or CRM 01450 provided 

higher recoveries than the unfiltered extracts 

The significant effect of wipe on lead recovery is also observable in Figure 1. As evident, Wipe 3 

and Wipe 4 specimens provided generally higher recoveries than Wipe 2 specimens. This wipe 

effect was present in the previous NIST study [8], wherein Wipe 3 and Wipe 4 specimens had 

significantly higher recoveries than Wipe 2 specimens. Table 4 provides, as a function of 

combination of wipe and CRM, a summary of the percentages of the lead recoveries that were 

quantitative in the present and previous NIST studies. Consistent with the findings that Wipe 3 and 

Wipe 4 specimens had higher recovery than Wipe 2 specimens, the percentage of analyses 

providing quantitative recovery for Wipe 3 and Wipe 4 specimens was 75 % or more, whereas that 

for Wipe 2 specimens was 42 % or less. 

The significant effect of lead level on lead recovery of Wipe 2 and CRM 01450 is also exhibited in 

Figure 1. For the combinations of these two parameters, it is seen that lead level 1 (LL1) specimens 

had recoveries that were much higher than lead level 2 (LL2) and lead level 3 (LL3) specimens. 

Table 4. Percentage of analyses providing quantitative lead recovery in the current and previous 

NIST studies 

 Current NIST Study Previous NIST Studya 

 SRM 2581 CRM 01450 SRM 2581 CRM 01450 

Wipe 

No. No. of 

Analyses 

Quant.b 

% 

No. of 

Analyses 

Quant.b 

% 

No. of 

Analyses 

Quant.b 

% 

No. of 

Analyses 

Quant.b 

% 

2 24 42 24 42 18 17 18 39 

3 24 75 24 100 18 94 18 100 

4 24 83 24 88 18 83 18 94 

a The summary is for data from three of the four operators in the study, because the fourth operator used a different 

UE/ASV test protocol than the other three [8]. 

b

 This column indicates the percentage of the analyses for which the ASV lead recovery was quantitative. 
8

WIPE 4

0

20

40

60

80

100

120

ASV LEAD RECOVERY, %

Filtered Extract

Unfiltered Extract

LL 1 LL 2 LL 3 LL 1 LL 2 LL 3

SRM 2581 CRM 01450 WIPE 4

0

20

40

60

80

100

120

ASV LEAD RECOVERY, %

Filtered Extract

Unfiltered Extract

LL 1 LL 2 LL 3 LL 1 LL 2 LL 3

SRM 2581 CRM 01450

Figure 1. Laboratory-Prepared Specimens: The Effect of Filtering of the UE Extract on ASV Lead 

Recovery by Wipe, CRM, and Lead Level (LL). Recoveries are relative to the amount of 

lead applied on the dust wipes. 

WIPE 2

0

20

40

60

80

100

120

ASV LEAD RECOVERY, %

Filtered Extract

Unfiltered Extract

LL 1 LL 2 LL 3 LL 1 LL 2 LL 3

SRM 2581 CRM 01450

WIPE 3

0

20

40

60

80

100

120

ASV LEAD RECOVERY, %

Filtered Extract

Unfiltered Extract

LL 1 LL 2 LL 3 LL 1 LL 2 LL 3

SRM 2581 CRM 01450
9

Specifically, whereas at LL1 all recoveries were quantitative with an average of about 95 %, at LL2 

and LL3 most recoveries (88 %) were not quantitative with the majority ranging between 40 % and 

60 %. This lead level effect for Wipe 2 and CRM 01450 specimens was also found in the previous 

NIST dust wipe study [8]. 

3.1.2 Effect of Analytical Method. ANOVA was conducted to determine the significance of the 

analytical method, i.e., ASV versus ICP, on lead recovery. From Table 5, the analytical method 

was significant (p-value < 0.05), as were the two-way interactions between analytical method and 

the three specimen variables, wipe, CRM, and lead level. Figure 2 illustrates the effect of analytical 

method on lead recovery. In each plot, a pair of adjoining bars having light and dark fills represents 

ASV and ICP recoveries, respectively, for the same combination of CRM and lead level. Figure 2 

shows that all ICP recoveries were quantitative whereas, as previously mentioned, only 72 % of the 

ASV recoveries was quantitative. Specifically observe, for Wipe 2, the higher recoveries 

determined by ICP for specimens prepared using CRM 01450 at LL2 and LL3. The finding that all 

ICP measurements were quantitative supports the results from the NLLAP analyses 

(Section 2.3.2.1) that the UE procedure successfully extracted the lead from the laboratory-prepared 

dust wipe specimens [5]. 

In the previous NIST study [8], ASV and ICP comparative analyses were performed on UE extracts 

from three specimens prepared with Wipe 2 and CRM 01450 at the lead levels used in the present 

study. Two of these specimens were at LL3 and the other was at LL1. The two LL3 specimens in 

the previous study provided ASV and ICP recoveries of about 45 % and 95 %, respectively; 

whereas the LL1 specimen gave 104 % and 101 % recovery for the ASV and ICP analyses, 

respectively. That is, the trends for the ASV and ICP analyses for specimens prepared with Wipe 2 

and CRM 01450 at various lead levels were similar for the present and previous NIST studies. 

3.1.2.1 ASV Versus ICP Plots. Complementary to the bar charts (Figure 2) used to illustrate the 

effect of analytical method, Figure 3 provides plots of ASV lead recovery versus ICP lead recovery 

for Wipes 2, 3, and 4. In each plot, the data symbol denotes the CRM, and the 45° solid line 

represents perfect agreement between the two analytical methods. The Wipe 2 plot illustrates the 

effect of lead level for CRM 01450 specimens, as it is evident that almost all the data points for the 

Wipe 2 CRM 01450 specimens having about 250 μg of lead (LL2) and 500 μg of lead (LL3) fall 

below the perfect agreement line. Moreover, a couple of the data points for Wipe 2 specimens 

prepared with SRM 2518 at LL2 and LL3 also fall below the perfect agreement line. 

 Table 5. Analysis of variance examining effect of analytical method on lead recovery 

 for the laboratory-prepared specimens, as determined by ASV and ICP 

 Analysis Resulta

 

Parameter F-Value P-Value 

Analytical Method (i.e., ASV versus ICP) 23.07 < 0.0001

Analytical Method – Wipe 11.13 < 0.0001

Analytical Method – CRM 4.36 0.0408 

Analytical Method – Lead Level 5.81 0.0002 

 a By convention, p-values less than 0.05 were considered to be statistically significant. Bold font is used 

 to denote significant p-values. 
10

Figure 2. Laboratory-Prepared Specimens: ASV Recovery Versus ICP Recovery by Wipe, CRM, 

and Lead Level (LL). For each method, recoveries are relative to the amount of lead 

applied on the dust wipes. 

WIPE 2

0

20

40

60

80

100

120

LEAD RECOVERY, %

Determined by ASV

Determined by ICP

LL 1 LL 2 LL 3 LL 1 LL 2 LL 3

SRM 2581 CRM 01450

WIPE 3

0

20

40

60

80

100

120

LEAD RECOVERY, %

Determined by ASV

Determined by ICP

LL 1 LL 2 LL 3 LL 1 LL 2 LL 3

SRM 2581 CRM 01450

WIPE 4

0

20

40

60

80

100

120

LEAD RECOVERY, %

Determined by ASV

Determined by ICP

LL 1 LL 2 LL 3 LL 1 LL 2 LL 3

SRM 2581 CRM 01450
11

Figure 3. Laboratory-Prepared Specimens: Amount of Lead Measured by ASV Versus That 

Determined by ICP for Specimens Prepared Using Wipes 2, 3, and 4. In each plot, the 

45° line represents perfect agreement between the two measurements. 

WIPE 2

0

100

200

300

400

500

600

0 100 200 300 400 500 600

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, 

μ

g

SRM 2581

CRM 01450

(A)

WIPE 3

0

100

200

300

400

500

600

0 100 200 300 400 500 600

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, 

μ

g

SRM 2581

CRM 01450

(B)

WIPE 4

0

100

200

300

400

500

600

0 100 200 300 400 500 600

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, 

μ

g

SRM 2581

CRM 01450

(C)
12

3.2 Field Specimens 

3.2.1 Ultrasonic Extraction. The finding that after sonication of the field specimens essentially all 

the lead was found by NLLAP ICP analysis to be in the UE extract (Section 2.3.2.1) indicated that 

the sonicator operation conditions were successful in extracting lead from these specimens. 

Successful sonicator extraction of lead in field-sampled dust, which has generally small particle size 

(sub-millimeter range), was consistent with the results of previous NIST research on UE/ASV 

analysis of lead-containing paints [12,17]. In those studies, lead in paint specimens was 

successfully extracted by sonication at temperatures and times similar to those used in the present 

study provided that the paint specimens were ground sufficiently small (i.e., generally < 425 μm 

particle size). Similarly, Drake et al. [11] found that lead in air particulate is readily extracted using 

UE (provided that lead-containing compounds that may need to be extracted using hydrofluoric acid 

are not present). Drake et al.’s sonication temperature and time were similar to those used in the 

present dust wipe study, although the extraction solution was 10 % (volume fraction) nitric acid as 

opposed to the 25 % nitric acid solution used here. On the other hand, in the previous NIST [8] and 

the Ashley et al. [5] dust wipe studies, it was observed that, for some combinations of wipe and 

CRMs (which are powdered), the ultrasonic extraction did not successfully solubilize lead in the 

dust wipe specimens. 

3.2.2 UE/ASV Lead Content. Table A4 contains the results of the UE/ASV analyses of the field 

specimens sampled by NIST research staff. Similarly, Tables A5, A6, and A7 give the results of the 

UE/ASV analyses of the field specimens sampled by Operators 2, 3, and 4, respectively. The 

amount of lead measured in the field specimens varied considerably, ranging from about 25 μg to 

more than 17 000 μg, although 58 % had less than 500 μg. These findings were consistent with the 

experimental plan that the houses chosen for sampling would provide specimens having measurable 

amounts of lead. Nevertheless, four specimens sampled by NIST research staff (Table A4) afforded 

UE/ASV results that were “below the detection limit” (i.e., 25 μg). The amount of lead found in the 

UE extracts for each of these four specimens by NLLAP ICP analysis was 25 μg or less. 

The results of the UE/ASV analyses of the field specimens are plotted in Figure 4 for each operator 

as a function of filter treatment of the UE extracts before ASV analyses. For clarity in presenting 

the data for specimens having low lead contents (e.g., < 100 μg), the y-axis scale for lead content is 

truncated at 2000 μg. Note that many of the pairs of adjacent bars have comparable height 

suggesting little difference between the ASV analyses of the filtered and unfiltered extracts. 

Repeated measures ANOVA [16] was performed on the entire data set to examine the effect of filter 

treatment, operator, and wipe on lead recovery (Table 6). Consistent with Figure 4, the ANOVA 

results for the entire data set indicated that filter treatment and the two-way interactions of filter 

treatment with operator and wipe were not significant (p-value > 0.05). Additionally, the effects of 

operator and wipe were also not significant. The lack of a wipe effect in the field phase was in 

contrast with the wipe effect observed in the laboratory phase of the present study (Section 3.1.3) 

and also in the previous NIST dust wipe study [8]. 

Repeated measures ANOVA was also conducted on a data subset that contained only those points 

for which the amount of lead determined by ICP analysis was < 500 μg. Analyses of dust wipe 

specimens found to have low lead contents play a role in identifying lead hazards in residential 

properties, as defined in federal regulations [18]. For example, dust clean-up after lead abatement 

activities is considered to be inadequate if lead levels in dust on floors, interior windowsills, and 
13

Figure 4. Field Specimens: Lead Content Determined by ASV Analyses of Filtered and Unfiltered 

UE Extracts for Each Operator. 

 Table 6. Analysis of variance examining effect of operator, wipe, and filter 

 treatment for the field specimens 

 Analysis Resultb 

Data Set Analyzeda Parameter F-Value P-Value 

All Data Operator 2.51 0.0631 

 Wipe 0.08 0.9205 

 Filter Treatment 1.59 0.2109 

 Filter Treatment – Operator 0.54 0.6569 

 Filter Treatment – Wipe 0.81 0.4476 

Less-Than-500 μg Operator 1.41 0.2507 

 Wipe 0.05 0.9468 

 Filter Treatment 9.50 0.0032 

 Filter Treatment – Operator 2.87 0.0447 

 Filter Treatment – Wipe 1.65 0.2015 

 a ANOVAs of the field data were performed twice: (1) using all points in the data set, and 

 (2) using a data subset containing only those points for which the amount of lead determined 

 by ICP analysis was < 500 μg. 

 b By convention, p-values less than 0.05 are considered to be statistically significant. Bold font 

 is used to denote significant p-values. 

NIST

0

500

1000

1500

2000

WIPE No.

ASV LEAD CONTENT, μg

Filtered Extract

Unfiltered Extract

Wipe 2 Wipe 3 Wipe 4

(A)

Operator 2

0

500

1000

1500

2000

WIPE No.

ASV LEAD CONTENT, μg

Filtered Extract

Unfiltered Extract

(B)

Wipe 2 Wipe 3 Wipe 4

Operator 3

0

500

1000

1500

2000

WIPE No.

ASV LEAD CONTENT, μg

Filtered Extract

Unfiltered Extract

(C)

Wipe 2 Wipe 3 Wipe 4

Operator 4

0

500

1000

1500

2000

WIPE No.

ASV LEAD CONTENT, μg

Filtered Extract

Unfiltered Extract

(D)

Wipe 2 Wipe 3 Wipe 4
14

window troughs are equal to or exceed 40 μg/ft2, 250 μg/ft2 and 400 μg/ft2, respectively.* For the 

less-than-500 μg data subset, a filter treatment effect was found (Table 6), with the filtered UE 

extracts providing greater recovery than the unfiltered extracts. In addition, an interaction between 

filter treatment and operator was observed. The filter treatment effect for the less-than-500 μg 

subset supports previous recommendations [5] that filtering of UE dust wipe extracts should be 

performed before conducting ASV analyses to enhance lead recovery. 

3.2.2.1 ASV Versus ICP Plots. Figure 5 compares the results of the ASV and ICP lead analyses 

determined by all operators†

. The left linear regression plot (A) shows all data with the exception of 

the data point of about 17 000 μg of lead determined by Operator 2 (Table A5)‡. The right linear 

regression plot (B) presents the less-than-500 μg data subset. In both the (A) and (B) plots, the plot 

character denotes the wipe number. The dashed line is that from the linear regression analysis. The 

45° solid line represents perfect agreement between the two measurement methods. Table 7 gives 

the coefficients for the linear regression analyses. For the entire data set, the slope and intercept 

were not significantly different from 1 and 0, respectively. For the less-than-500 μg data subset, the 

slope was significantly different from 1, but it was only about 12 % less. The intercept was again 

not significantly different from 0. For both data sets, as evident in Figure 5, the variability around 

the regression line was small. This observation is quantified by r2

-values (Table 7) of 0.99 and 0.95 

for the entire data set and for the less-than-500 μg data subset, respectively. 

Figure 5. Field Specimens: ASV Results Versus ICP Results. The left plot (A) shows all data with 

exception of one point with a lead content of ≈ 17 000 μg that was not presented for 

purposes of clarity. The right plot (B) is for the less-than-500 μg data subset. In each 

plot, the plot character represents the wipe number. The dashed line is that from the 

linear regression analysis. The solid 45° line represents perfect agreement between the 

two measurements. 

 

*

 Micrograms per squared foot (μg/ft2) is the unit of measurement for dust levels prescribed in federal regulations [18]; 

sampling is often performed on a 0.09 m2

 (1 ft2) area. 

†

 Comparison of the ASV and ICP lead recoveries by operator is a main objective of the study so regression plots of the 

ASV and ICP results by operator are presented in Appendix B. 

‡

 The data point was included in the regression analysis. 

222 2

2

22

2

22 2

2

22 2

2

2

2 2

2

2222 232 33

3

3 3 3

3

3

3 3

3

3

3

33

3

3

3 3

3

3

3

3

33

3

3

4

4 4

4

4 4 44

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

4

444

4

0

2000

4000

6000

8000

0 2000 4000 6000 8000

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, μg

(A)

2

2

2

2

2

2

2 2

2

2

2

2

2 2

2

2

2

2

2 2

2

2

2

2

2

3

3

3

3

3

3

3

3

3

3

3

3

3

3

3 3

3 3 3 3

4

4

4

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4

4

4 4

4

4

4

4

4

4

4 4

4

4 4

4

0

100

200

300

400

500

0 100 200 300 400 500

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, μg

(B)
15

40

60

80

100

120

140

160

12345

WIPE No.

ASV LEAD RECOVERY, %

NIST

Operator 2

Operator 3

Operator 4

3.2.3 Lead Recovery. Figure 6 shows the percent lead recoveries (using filtered extracts) by 

operator relative to the amount of lead determined by ICP analyses. Eighty-eight percent (88 %) of 

the 104 UE/ASV field specimen analyses providing results greater than the ASV instrument 

detection limit were quantitative. In comparison, in the laboratory phase of the study, 72 % of the 

UE/ASV analyses were quantitative. 

 Table 7. Linear regression analysis coefficients for the ASV versus ICP comparison for all 

 field data 

 Coefficients Significantc 

Operator 

Data Set 

Analyzeda Slopeb Interceptb r

2

-value Slope Intercept 

All Ops. All Data 1.008 (0.010) - 40.553 (22.937) 0.991 No No 

< 500 μg 0.883 (0.026) 3.531 (4.972) 0.953 Yes No 

 a Linear regression analyses were performed twice: (1) using all points in the data set, and (2) using a data subset 

containing only those points for which the amount of lead determined by ICP analysis was < 500 μg. 

 b The value in parentheses is the standard error. c These two columns indicate whether the slope and the intercept were significantly different from 1 and 0, 

respectively. 

 

Figure 6. Field Specimens: Percent ASV Lead Recovery. The percent ASV lead recovery is 

relative to the amount of lead determined by ICP analysis. A recovery falling on or 

between the two horizontal bold lines is quantitative, i.e., recovery is 100 % ± 20 % of the 

estimated true lead value. 
16

3.2.4 Comparison with the NIOSH Criterion. The National Institute for Occupational Safety and 

Health (NIOSH) prescribes that “a method must give a result that is within ± 25 % of the true 

concentration value at least 95 % of the time” [11]. Statistical analysis of the field specimen results 

was performed to examine the reliability of the UE/ASV method vis-à-vis the NIOSH criterion. 

The calculation was based on the predictive probability distribution of a future observation [19], and 

used ICP results as the estimated true lead values of the field specimens. Using the entire NIST 

data set for all operators and an estimated 8 % uncertainty for the ICP measurements, the 

probability of a future ASV analysis yielding a result within ± 25 % of an ICP result was estimated 

to be 0.93. This value was low in comparison with the NIOSH criterion that, for at least 95 % of 

the time, the result should be within ± 25 % of the true concentration. For the less-than-500 μg data 

set for all operators, the probability of a future ASV analysis yielding a result within ± 25 % of an 

ICP result was estimated to be 0.96, which was in agreement with the NIOSH criterion. 

3.3 Future Work. 

The evidence from this and previous studies [4-8] suggests that UE/ASV can be a viable procedure 

for the analysis of lead in dust. However, an important factoring affecting the reliability of 

UE/ASV analysis is the wipe used for the dust sampling, as this and other studies [5,8] using 

specimens prepared from commercial dust wipes and a variety of CRMs have shown a significant 

dust wipe effect. Not all wipes have been found to be suitable for use with UE/ASV analyses. A 

need exists to identify the attributes of wipes that make them exceptionally effective in the UE/ASV 

protocol. Once these attributes have been identified and their effectiveness verified, then it would 

be possible to publish these attributes and amend ASTM Standards such as E 1792 [3] or E 1775 

[20] so that only effective wipes are used in the UE/ASV protocolthus increasing the efficacy of 

the UE/ASV protocol. 

4. SUMMARY AND CONCLUSIONS 

Knowledge of the amount of lead in settled dust is important in clearance examinations, risk 

assessments, and related activities wherein decisions are made regarding the identification of lead 

hazards in houses and related buildings. For example, under certain circumstances such as reoccupancy of the living space after lead abatement, it could be worthwhile having a test procedure 

for on-site dust analysis so that quick decisions regarding any hazards due to lead in dust could be 

made. At present, dust analyses are performed in laboratories, because quantitative analysis 

methods generally used for analysis of lead in dust are not readily field-portable. In recent years, 

field portable ultrasonic extraction/anodic stripping voltammetry (UE/ASV) has been suggested as a 

method for field analysis of dust wipe specimens. A reservation to accepting UE/ASV for field use 

is that the method’s response in analyzing field-sampled dust wipe specimens has not been 

demonstrated. As a step toward overcoming this limitation, this study sponsored by the U.S. 

Department of Housing and Urban Development (HUD) compared the results of ASV analyses of 

UE extracted field-sampled dust wipes with the results of ICP analyses of the same extract 

solutions. The main objective was to investigate whether lead in dust wipe specimens obtained in 

the field can be efficiently and effectively extracted and reliably quantified using common UE/ASV 

field procedures when the sampling and analyses are performed by certified risk assessors. 

In the laboratory phase, data on the use of an ICP procedure for estimating the true value of lead in 

dust wipe specimens were obtained, because ICP was selected as the reference test method for 

estimating the true lead values of the field specimens. Seventy-two (72) specimens including four 

replicates per wipe, CRM and lead level combination were prepared by applying two lead-
17

containing CRMs at three lead levels on three commercial dust wipe products. Lead in the 

specimens was extracted using ultrasonication, and ASV analyses were performed on both filtered 

and unfiltered UE extracts. In addition, ICP analyses were conducted on filtered UE extracts, and 

compared with the ASV analyses. The reliability of the UE/ASV method for determining lead in 

these dust wipe specimens was examined by evaluating whether the lead recoveries were 

quantitative; that is 100 % ± 20 % of the estimated true lead value. For the laboratory specimens, 

the estimated true lead values were taken relative to the amounts of CRM deposited on the wipes. 

Key findings of the laboratory phase were: 

• The wipe effect was significant; two of the three wipes provided higher recovery than the third 

wipe. 

• The lead level effect was significant; one of the three lead levels incorporated in specimens 

prepared with one wipe and one CRM provided higher recovery than the other two lead levels. 

• The CRM effect was insignificant. 

• The filter treatment effect was insignificant, although the two-way interaction between filter 

treatment and wipe was significant. For one wipe, the unfiltered extracts provided higher 

recoveries than the filtered extracts. 

• ICP recoveries were significantly higher than ASV recoveries. All ICP recoveries were 

quantitative, whereas only 72 % of the ASV recoveries were quantitative. 

• The quantitative ICP analyses indicated that the sonicator operating conditions successfully 

extracted essentially all the lead from the specimens. 

In the field phase, three experimental variables were examined for their effect on dust wipe lead 

recovery: operator, wipe, and filter treatment of the UE extract before ASV analysis. NIST research 

staff along with three certified lead risk assessors, who had participated in a previous NIST dust 

wipe study, obtained 108 dust wipe specimens from houses using the three dust wipe products 

incorporated in the laboratory phase of the study. The individual who performed the field sampling 

conducted the UE/ASV analyses at NIST. ASV analyses were conducted on filtered and unfiltered 

UE extracts. The true lead values of the specimens were estimated using the results of ICP 

analyses. UE/ASV lead recoveries were calculated relative to the lead contents determined by the 

ICP. As in the laboratory phase, the reliability of the UE/ASV method for determining lead in these 

dust wipe specimens was examined by evaluating whether the lead recoveries were quantitative. 

Additionally, UE/ASV reliability was analyzed vis-à-vis a National Institute for Occupational 

Safety and Health (NIOSH) criterion that “a method must give a result that is within ± 25 % of the 

true concentration value at least 95 % of the time.” Statistical analyses of the field specimen results 

were performed for the set of all data collected by the operators, and also for a data subset 

consisting of those points for which the ICP lead results were less than 500 μg. 

Key findings of the field phase were: 

• None of the three variables incorporated in the field phase, operator, wipe, and filter treatment, 

was significant when the entire data set was analyzed. A filter treatment effect was present for 

the less-than-500 μg data subset. 

• The lack of a wipe effect contrasted with the results of the laboratory phase in which two wipes 

afforded significantly higher recoveries than the third wipe. 

• Eighty-eight percent (88 %) of the field-specimen analyses provided quantitative recovery. 

• Ultrasonic extraction was successful in solubilizing the lead from the field specimens. 

• Based on analyses of the entire data set and also of the less-than-500 μg data subset, the 

probabilities of a future ASV analysis yielding a result within ± 25 % of an ICP result were 

estimated to be 0.93 and 0.96, respectively. 
18

The results of this and previous studies suggest that UE/ASV lead analysis of dust wipes can be a 

viable procedure provided that suitable wipes are selected for dust sampling and subsequent 

analysis. Not all wipes have been found to be suitable for use with UE/ASV analyses. A need 

exists to identify and verify those attributes that make wipes exceptionally effective in the UE/ASV 

protocol. Future work should be directed toward this goal. 

 

5. ACKNOWLEDGMENTS 

The U. S. Department of Housing and Urban Development (HUD), Office of Healthy Homes and 

Lead Hazard Control (OHHLHC), sponsored this study. The authors acknowledge with thanks the 

support and encouragement of HUD colleagues Peter Ashley, Warren Friedman, David E. Jacobs, 

and Eugene Pinzer. Thanks are extended to NIST colleagues, Joannie Chin, Dennis Leber, and 

Jonathan Martin, for their thorough reviews and noteworthy comments on the report. The authors 

especially appreciate with thanks the assistance of David Binstock, Research Triangle Institute 

(RTI), who also provided critical review and important comments. 

6. REFERENCES 

 [1] “Guidelines for the Evaluation and Control of Lead-Based Paint Hazards in Housing,” U.S. 

Department of Housing and Urban Development, HUD-1539-LBP (July 1995), available at: 

www.hud.gov/offices/lead/guidelines/hudguidelines/index.cfm. 

 [2] “Collection of Settled Dust Samples Using Wipe Sampling Methods for Subsequent Lead 

Determination,” ASTM Standard Practice E 1728, Annual Book of Standards, Vol. 04.12, 

ASTM International, West Conshohocken, PA (2003). 

 [3] “Wipe Sampling Materials for Lead in Surface Dust,” ASTM Standard Specification 

E 1792, Annual Book of Standards, Vol. 04.12, ASTM International, West Conshohocken, 

PA (2003). 

 [4] Ashley, K., Song, R., Esch, C.A., Schlecht, P.C., Baron, P.A., and Wise T.J., “Ultrasonic 

Extraction and Anodic Stripping Voltammetry of Lead in Paint, Dust Wipes, Soil, and Air: 

An Interlaboratory Evaluation,” Journal of Environmental Monitoring, 1 (1999), pp. 459-

464. 

 [5] Ashley, K., Wise, T.J., Mercado, W., and Parry, D.B., “Ultrasonic Extraction and FieldPortable Anodic Stripping Voltammetry Measurement of Lead in Dust Wipe Samples,” 

Journal of Hazardous Materials, 83 (2001), pp. 41-50. 

 [6] Dindal, A.B., Bayne, C.K., Jenkins, R.A., and Koglin, E.N., Environmental Technology 

Verification Report, Lead in Dust Wipe Measurement Technology, U.S. Environmental 

Protection Agency, EPA/600/R-02/057 (September 2002), available at: www.epa.gov/etv. 

 [7] Dindal, A.B., Bayne, C.K., Jenkins, R.A., and Koglin, E.N., Environmental Technology 

Verification Report, Lead in Dust Wipe Measurement Technology, U.S. Environmental 

Protection Agency, EPA/600/R-02/060 (September 2002), available at: www.epa.gov/etv. 

 
19

 [8] Rossiter, W.J., Jr., Toman, B., McKnight, M.E., Emenanjo, I, and Baghai Anaraki, M., 

“Ultrasonic Extraction/Anodic Stripping Voltammetry for Determining Lead in Dust: A 

Laboratory Evaluation,” NISTIR 6998, National Institute of Standards and Technology, 

Gaithersburg, MD (September, 2004), 47 pages. 

 [9] “Terminology Relating to Lead in Buildings,” ASTM Standard Terminology E 1605, 

Annual Book of Standards, Vol. 04.11, ASTM International, West Conshohocken, PA 

(2003). 

 [10] Ashley, K., “Ultrasonic Extraction and Field-Portable Anodic Stripping Voltammetry of 

Lead from Environmental Samples, Electroanalysis, Vol. 7, No. 12 (1995), pp. 1189-1192. 

 [11] Drake, P.L., Lawryk, N.J., Ashley, K., Sussell, A.L., Hazelwood, K.J., and Song, R., 

“Evaluation of Two Portable Lead-Monitoring Methods at Mining Sites,” Journal of 

Hazardous Materials, 102 (2003), pp. 29-38. 

 [12] Rossiter, W.J., Jr., Toman, B., McKnight, and Baghai Anaraki, M., “Factors Affecting 

Ultrasonic Extraction of Lead from Laboratory-Prepared Household Paint Films,” NISTIR 

6834, National Institute of Standards and Technology, Gaithersburg, MD (May 2002), 48 

pages. 

 [13] EPA National Lead Laboratory Accreditation Program Laboratory Quality System 

Requirements (LQSR), Revision 2.0,” (August 1, 1996); available on the web at: 

www.hud.gov/offices/lead/labs/LQSR.pdf. 

 [14] U.S. Environmental Protection Agency, Test Methods SW-846, Test Method 6010B, 

“Inductively Coupled Plasma-Atomic Emission Spectrometry,” available on the web at: 

www.epa.gov/SW-846/pdfs/6010b.pdf. 

 [15] U.S. Environmental Protection Agency, Test Methods SW-846, Test Method 3050B, “Acid 

Digestion of Sediments, Sludges, and Soils,” available on the web at: 

 www.epa.gov/SW-846/pdfs/3050b.pdf. 

 

 [16] Crowder, M.J. and Hand, D.J., Analysis of Repeated Measures, Chapman & Hall, London 

(1990). 

 [17] Rossiter, W.J., Jr., Toman, B., McKnight, Emenanjo I., and Baghai Anaraki, M., “Factors 

Affecting Ultrasonic Extraction of Lead from Paint: Further Investigations,” NISTIR 6948, 

National Institute of Standards and Technology, Gaithersburg, MD (March 2003), 33 pages. 

 [18] “Identifying Lead Hazards in Residential Properties,” EPA Fact Sheet 747-F-01-002 (April 

2001); available on the web at: www.epa.gov/lead/403FS01.pdf. 

 [19] Schervish, M.J., Theory of Statistics, Springer Verlag, New York (1995). 

 [20] “Evaluating Performance of On-Site Extraction and Field-Portable Electrochemical or 

Spectrophotometric Analysis for Lead,” ASTM Standard Guide E 1775, Annual Book of 

Standards, Vol. 04.12, ASTM International, West Conshohocken, PA (2003).
A1

APPENDIX A. UE/ASV DATA 

This appendix presents tables of data from all UE/ASV and UE/ICP analyses performed during the 

study. Tables A1 through A3 summarize the data for the laboratory-prepared specimens, while 

Tables A4 through A7 summarize the data for the field specimens. 

Table A1. Results of lead analyses of laboratory specimens prepared using Wipe 2 

 Lead Content of UE Extract 

Wipe CRM

Target Lead 

Level Replicate

Lead Spiked

on Wipe ASV-UFEb ASV-FEc ICP-FEd

No. ID μg No. μg μg μg μg 

2 SRM 2581 90 1 104 67 69 90 

 2 103 89 78 83 

 3 87 74 66 74 

 4 97 76 78 81 

2 SRM 2581 250 1 243 207 214 204 

 2 247 132 127 216 

 3 262 201 193 236 

 4 252 212 218 213 

2 SRM 2581 500 1 493 365 396 399 

 2 489 373 387 440 

 3 500 332 302 437 

 4 517 456 429 434 

2 CRM 01450 40 1 39 41 43 36 

 2 40 37 39 37 

 3 42 43 41 41 

 4 40 32 32 37 

2 CRM 01450 250 1 250 214 210 224 

 2 252 114 121 241 

 3 255 158 125 248 

 4 256 108 147 248 

2 CRM 01450 500 1 501 177 158 484 

 2 505 223 223 493 

 3 499 396 300 455 

 4 505 202 238 479 a ASV-UFE indicates ASV measurement of the unfiltered extract. 

 b ASV-FE indicates ASV measurement of the filtered extract. c ICP-FE indicates ICP measurement of the filtered extract. 
A2

Table A2. Results of lead analyses of laboratory specimens prepared using Wipe 3 

 Lead Content of UE Extract 

Wipe CRM

Target Lead 

Level Replicate

Lead Spiked

on Wipe ASV-UFEb ASV-FEc ICP-FEd

No. ID μg No. μg μg μg μg 

3 SRM 2581 90 1 91 87 84 77 

 2 101 80 79 93 

 3 98 79 82 85 

 4 96 79 80 84 

3 SRM 2581 250 1 249 206 215 219 

 2 248 210 197 203 

 3 252 230 220 201 

 4 259 236 244 220 

3 SRM 2581 500 1 499 410 417 444 

 2 505 395 456 454 

 3 504 389 412 442 

 4 508 391 434 452 

3 CRM 01450 40 1 39 43 46 42 

 2 44 45 43 44 

 3 44 43 42 44 

 4 42 45 42 42 

3 CRM 01450 250 1 253 267 251 238 

 2 254 261 261 243 

 3 254 239 252 229 

 4 254 254 249 253 

3 CRM 01450 500 1 502 468 513 471 

 2 503 527 525 476 

 3 501 443 484 498 

 4 502 474 476 500 a ASV-UFE indicates ASV measurement of the unfiltered extract. 

 b ASV-FE indicates ASV measurement of the filtered extract. c ICP-FE indicates ICP measurement of the filtered extract. 
A3

Table A3. Results of lead analyses of laboratory specimens prepared using Wipe 4 

 Lead Content of UE Extract 

Wipe CRM

Target Lead 

Level Replicate

Lead Spiked

on Wipe ASV-UFEb ASV-FEc ICP-FEd

No. ID μg No. μg μg μg μg 

4 SRM 2581 90 1 91 72 76 83 

 2 103 95 97 94 

 3 93 87 82 86 

 4 91 84 84 81 

4 SRM 2581 250 1 264 246 240 227 

 2 264 252 250 238 

 3 266 244 212 235 

 4 261 208 160 235 

4 SRM 2581 500 1 505 442 345 446 

 2 505 426 453 454 

 3 504 438 482 451 

 4 500 440 365 443 

4 CRM 01450 40 1 40 43 43 41 

 2 41 44 42 41 

 3 43 43 39 42 

 4 40 49 44 40 

4 CRM 01450 250 1 249 240 224 249 

 2 249 226 205 243 

 3 249 220 257 251 

 4 249 275 236 244 

4 CRM 01450 500 1 501 236 285 492 

 2 498 519 474 500 

 3 498 478 435 498 

 4 498 595 493 481 a ASV-UFE indicates ASV measurement of the unfiltered extract. 

 b ASV-FE indicates ASV measurement of the filtered extract. c ICP-FE indicates ICP measurement of the filtered extract. 
A4

 Table A4. Results of lead analyses of NIST field specimens 

 Lead Content of UE Extract 

Specimen Operator Wipe ASV−UFEa ASV−FEb ICP−FEb

Lead 

Recoveryc

No. ID No. μg μg μg % 

1 NIST 2 68 74 71 104.2 

2 2 39 43 49 88.7 

3 2 417 412 435 94.8 

4 2 777 960 1130 85.0 

5 2 439 480 520 92.3 

6 2 105 113 114 99.6 

7 2 234 259 285 90.9 

8 2 63 68 64 107.1 

9 2 84 84 94 89.4 

10 2 173 187 202 92.6 

11 2 143 133 170 78.2 

12 2 < ADLd < ADL 25 -- 

13 NIST 3 160 166 172 96.8 

14 3 89 89 96 93.2 

15 3 84 95 92 103.8 

16 3 288 273 276 99.1 

17 3 63 65 64 102.4 

18 3 265 303 341 88.9 

19 3 284 307 308 99.7 

20 3 72 84 76 110.5 

21 3 2890 2160 2130 101.4 

22 3 < ADL < ADL 20 -- 

23 3 < ADL < ADL 11 -- 

24 3 < ADL < ADL 18 -- 

25 NIST 4 4315 4080 4450 91.7 

26 4 285 275 311 88.6 

27 4 367 402 490 82.1 

28 4 232 226 239 94.8 

29 4 41 41 45 92.1 

30 4 29 25 30 83.3 

31 4 468 527 635 83.0 

32 4 59 57 58 99.1 

33 4 221 72 147 49.1 

34 4 59 63 63 100.8 

35 4 1069 1103 1180 93.5 

36 4 620 542 625 86.7 a

 ASV-UFE indicates ASV measurement of the unfiltered extract. 

b ASV-FE and ICP-FE indicate ASV and ICP measurements, respectively, of the filtered extract. c

 Lead recovery (%) = [(ASV−FE/ICP−FE) x 100]. 

d

 < ADL indicates the result was below the ASV detection limit (i.e., 25 μg). 
A5

 Table A5. Results of lead analyses of Operator 2 field specimens 

 Lead Content of UE Extract 

Specimen Operator Wipe ASV−UFEa ASV−FEb ICP−FEb

Lead 

Recoveryc

No. ID No. μg μg μg % 

1 2 2 47 59 79 74.7 

2 2 423 478 525 91.0 

3 2 19 550 17 300 16 700 103.6 

4 2 663 1467 1950 75.2 

5 2 93 145 154 94.2 

6 2 219 257 237 108.4 

7 2 400 556 615 90.4 

8 2 215 259 265 97.9 

9 2 3 139 126 229 55.1 

10 3 3730 3885 3835 101.3 

11 3 194 204 300 68.0 

12 3 419 499 570 87.5 

13 3 1412 3165 3065 103.3 

14 3 91 126 124 101.6 

15 3 868 969 1180 82.1 

16 3 207 240 237 101.3 

17 2 4 6330 6715 6850 98.0 

18 4 595 626 620 101.0 

19 4 156 168 210 80.0 

20 4 3295 3515 3395 103.5 

21 4 162 183 204 89.9 

22 4 95 99 99 100.0 

23 4 1099 1287 1660 77.5 

24 4 3455 3435 3235 106.2 a

 ASV-UFE indicates ASV measurement of the unfiltered extract. 

b ASV-FE and ICP-FE indicate ASV and ICP measurements, respectively, of the filtered extract. c

 Lead recovery (%) = [(ASV-FE/ICP-FE) x 100]. 
A6

 Table A6. Results of lead analyses of Operator 3 field specimens 

 Lead Content of UE Extract 

Specimen Operator Wipe ASV−UFEa ASV−FEb ICP−FEb

Lead 

Recoveryc

No. ID No. μg μg μg % 

1 3 2 141 156 168 92.9 

2 2 2985 3365 2775 121.3 

3 2 495 525 580 90.5 

4 2 309 343 625 54.9 

5 2 47 55 55 100.9 

6 2 36 42 50 84.8 

7 2 8150 7575 8200 92.4 

8 2 796 924 1135 81.4 

9 3 3 183 208 194 107.5 

10 3 168 194 210 92.4 

11 3 4060 3720 3610 103.0 

12 3 928 1124 1235 91.0 

13 3 394 447 585 76.4 

14 3 725 796 945 84.2 

15 3 5240 5090 5850 87.0 

16 3 515 638 650 98.2 

17 3 4 1311 1394 1505 92.6 

18 4 1403 2535 1925 131.7 

19 4 752 833 1700 49.0 

20 4 210 231 265 87.2 

21 4 3155 2890 2605 110.9 

22 4 1365 2390 1850 129.2 

23 4 168 202 210 96.4 

24 4 149 191 231 82.9 a

 ASV-UFE indicates ASV measurement of the unfiltered extract. 

b ASV-FE and ICP-FE indicate ASV and ICP measurements, respectively, of the filtered extract. c

 Lead recovery (%) = [(ASV-FE/ICP-FE) x 100]. 
A7

 Table A7. Results of lead analyses of Operator 4 field specimens 

 Lead Content of UE Extract 

Specimen Operator Wipe ASV−UFEa ASV−FEb ICP−FEb

Lead 

Recoveryc

No. ID No. μg μg μg % 

1 4 2 68 74 88 84.1 

2 2 107 112 122 92.2 

3 2 74 97 133 72.9 

4 2 53 63 71 89.4 

5 2 32 32 33 98.5 

6 2 89 91 92 98.9 

7 2 221 294 310 94.8 

8 2 307 343 378 90.7 

9 4 3 949 1131 1140 99.2 

10 3 3505 3720 3820 97.4 

11 3 42 51 54 94.4 

12 3 59 68 97 70.5 

13 3 63 59 69 85.5 

14 3 390 461 875 52.7 

15 3 468 692 755 91.7 

16 3 47 49 50 99.0 

17 4 4 2720 3970 3500 113.4 

18 4 2430 1795 1755 102.3 

19 4 34 36 35 102.9 

20 4 569 574 565 101.6 

21 4 91 89 91 98.3 

22 4 99 107 114 94.3 

23 4 116 131 144 91.0 

24 4 1029 1069 1030 103.8 a

 ASV-UFE indicates ASV measurement of the unfiltered extract. 

b ASV-FE and ICP-FE indicate ASV and ICP measurements, respectively, of the filtered extract. c

 Lead recovery (%) = [(ASV-FE/ICP-FE) x 100]. 

 
B1

APPENDIX B. REGRESSION PLOTS COMPARING ASV AND ICP FIELD SPECIMEN 

RESULTS BY OPERATOR 

This Appendix provides linear regression plots (Figure B1) comparing the ASV and ICP field 

specimen results by operator. Although the effect of operator on the UE/ASV lead analyses of the 

field specimens was not statistically significant (Section 3.2.2), some readers may have interest in 

observing the individual operator data because an examination of operator effect was a main 

objective of the study. 

In Figure B1, the plots in the left column show all data for each operator with the exception of the 

17 000 μg data point determined by Operator 2 (Table A5); this data point was included in the 

regression analyses. The right plots in the figure present the less-than-500 μg data subset for each 

operator. In each plot, the plot character denotes the wipe number. The dashed line is that from the 

linear regression analyses. The 45° solid line represents perfect agreement between the two 

measurement methods. Table B1 gives the coefficients for these linear regression analyses. 

 Table B1. Linear regression analysis coefficients for the ASV versus ICP comparisons by 

operator 

 Coefficients Significantc 

Operator 

Data Set 

Analyzeda Slopeb Interceptb r

2

-value Slope Intercept 

NIST All Data 0.930 (0.009) -4.212 (8.926) 0.997 Yes No 

< 500 μg 0.885 (0.030) 4.970 (6.404) 0.974 Yes No 

2 All Data 1.033 (0.009) -88.534 (37.033) 0.998 Yes Yes 

< 500 μg 0.773 (0.173) 19.510 (35.670) 0.688 No No 

3 All Data 0.943 (0.037) 34.939 (91.033) 0.968 No No 

< 500 μg 0.885 (0.077) 7.161 (14.439) 0.957 No No 

4 All Data 1.043 (0.026) -36.316 (31.145) 0.987 No No 

< 500 μg 0.919 (0.026) -1.806 (3.901) 0.989 Yes No 

 a For each operator’s data set, regression analyses were performed twice: (1) using all points in the data set, and (2) 

using a data subset containing only those points for which the amount of lead determined by ICP analysis was 

< 500 μg. 

 b The value in parentheses is the standard error. c These two columns indicate whether the slope and the intercept were significantly different from 1 and 0, 

respectively. 
B2

Figure B1. Field Specimens: ASV Results Versus ICP Results by Operator. The plots in the left 

column show all data for each operator, except one point with a lead content of 

≈ 17 000 μg (Operator 2). The plots in the right column give data for specimens found 

by ICP analyses to have less than 500 μg of lead. In each plot, the plot character 

represents the wipe number. The dashed line is that from the linear regression analysis. 

The 45° solid line represents perfect agreement between the two measurements. 

2 22

2

2

2 2

2

22 23

3 3

3

3 3 33 3

4

4

4

4

4

4

4 4 44 4

4

0

800

1600

2400

3200

4000

4800

0 800 1600 2400 3200 4000 4800

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, μg

 NIST

(A)

2

2

2

22 2 23

3

3 3

3

3

3

3

4

4

4

4

4

4

4

0

2000

4000

6000

8000

0 2000 4000 6000 8000

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, μg

OPERATOR 2

(C) 2

2

2 2

3

3

3

3

4

4

4

0

100

200

300

400

500

0 100 200 300 400 500

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, μg

OPERATOR 2

(D)

2

2

22 2

2

2

3

3

3

3 3

3

3

4

4

4

4

4

4

4 0

2000

4000

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8000

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0 2000 4000 6000 8000 10000

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, μg

 OPERATOR 3

(E)

2

2

2

3 3

4

4 4

0

100

200

300

400

500

0 100 200 300 400 500

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, μg

 OPERATOR 3

(F)

2222 22

3

3

333

3

3

4

4

4

4

444

4

0

1000

2000

3000

4000

5000

0 1000 2000 3000 4000 5000

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, μg

 OPERATOR 4

(G) 2

2 2

2

2

2

2

2

3 3 3 3 4

4 4

4

0

100

200

300

400

500

0 100 200 300 400 500

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, μg 

 OPERATOR 4

(H)

2

2

2

2

2

2 2

2

2

3

3

3

3

3

3

3

3

4

4

4

4

4

4 4

4

0

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0 100 200 300 400 500

ICP LEAD CONTENT, μg

ASV LEAD CONTENT, μg

 NIST

(B)