EPA/600/R-10/068 October 2006 www.epa.gov/ord 

Report on the State of Development, Availability, 

Evaluation, and Future Use of Test Kits for the 

Measurement of Lead in Paint 

Prepared by 

W. F. Gutknecht, W. Winstead, C.A. Salmons, and D.A. Binstock 

RTI International 

3040 Cornwallis Road 

Research Triangle Park, NC 27709 
ii 

Disclaimer 

The information in this document has been funded wholly or in part by the U.S. Environmental 

Protection Agency (EPA) under EPA Contract No. EP-D-05-065 to Alion Science and 

Technology, Inc., and RTI Subcontract No. SUB1174861RB. It has been subjected to the 

Agency’s peer and administrative review. Mention of trade names or commercial products does 

not constitute endorsement or recommendation for use. 
iii 

Acknowledgments 

This document was prepared under the direction of the Work Assignment Contracting Officer’s 

Representative, Ms. Sharon L. Harper, National Environmental Research Laboratory, U.S. 

Environmental Protection Agency, Research Triangle Park, NC. 

Special acknowledgment is given to Dr. Hunter Daughtrey, Alion Science and Technology, Inc., 

for his support of this effort and careful review of this document. 
iv 
v 

Table of Contents 

List of Tables................................................................................................................................ vi 

List of Figures ............................................................................................................................. vii 

1.0 INTRODUCTION...............................................................................................................1 

1.1 Test Kits ...................................................................................................................2 

1.1.1 Spot Test Kits ...............................................................................................2 

1.1.2 Semi-quantitative and Quantitative Test Kits................................................5 

1.2 Early Issue Papers ...................................................................................................5 

1.2.1 Proposed Performance Parameters .............................................................5 

1.2.2 Manufacturer Outreach.................................................................................7 

1.3 Preparation of this Issue Paper ................................................................................8 

2.0 AVAILABLE TEST KITS ..................................................................................................8 

3.0 PREVIOUS STUDIES OF TEST KITS..............................................................................9 

3.1 Spot Test Kits...........................................................................................................9 

3.1.1 RTI Laboratory Evaluation............................................................................9 

3.1.2 HUD/QuanTech Field Study .......................................................................21 

3.1.3 OSHA Study ...............................................................................................23 

3.1.4 Laboratory Evaluation of the LeadCheck Test Kit ......................................23 

3.1.5 RTI Pilot Field Study...................................................................................24 

3.1.6 Field Evaluation of the LeadCheck Test Kit................................................25 

3.1.7 RTI Large Field Study.................................................................................26 

3.1.8 NIST Laboratory Study ...............................................................................27 

3.1.9 Testing Using the HUD Archive..................................................................32 

3.1.10 Reports from Jim Weydt of Acc-U-Test Test Kit.........................................33 

3.1.11 Test Kit Based on DNAzyme Nanoparticles ...............................................34 

3.1.12 Immunoassay-Based Test Kits...................................................................34 

3.1.13 Summary for Qualitative Test Kits ..............................................................35 

3.2 Semi-quantitative and Quantitative Test Kits .........................................................35 

3.2.1 Semi-quantitative Test Kits.........................................................................35 

3.2.2 Quantitative Test Kits―Laboratory Study...................................................36 

3.2.3 Quantitative Test Kits―Field Studies .........................................................39 

3.2.4 Immunoassay-Based Test Kits...................................................................43 

4.0 AVAILABILITY OF PERFORMANCE EVALUATION MATERIALS..............................43 

5.0 STANDARD PROCEDURES FOR EVALUATION OF TEST KITS ...............................44 

6.0 SUMMARY AND RECOMMENDATIONS FOR FUTURE KIT EVALUATION...............46 

6.1 Historical Perspective.............................................................................................46 

6.2 Issues with Qualitative or Spot Test Kits ................................................................46 

6.3 Addressing the Basic Issue of Performance ..........................................................50 

6.4 Method Selection and/or Development ..................................................................50 

6.5 Method Evaluation..................................................................................................51 

6.5.1 Performance Evaluation Samples ..............................................................51 

6.5.2 Evaluating the Testing/Measurement Results ............................................53 

6.6 Summary ................................................................................................................53 

7.0 REFERENCES................................................................................................................53 
vi 

List of Tables 

1. Metallic Elements Having at Least One Black Sulfide .........................................................4 

2. Proposed Analysis Performance Criteria for Pb in Paint as of 1991....................................6 

3. Summary of Available Test Kits and Their Operational Parameters..................................10 

4. Test Kit Response to Pb2+ in Solution ................................................................................18 

5. Test Kit Response to Pb in Paint Films..............................................................................19 

6. Results of Nontechnical User Tests ...................................................................................20 

7. Comparison of Target Performance Criteria and Actual Performance Results on 

Paint...................................................................................................................................20 

8. Overall False Positive and False Negative Rates for Test Kits Compared to 

Laboratory Analytical Results Using the 1.0 mg Pb/cm2

 Threshold...................................22 

9. Overall False Positive and False Negative Rates for Test Kits Compared to 

Laboratory Analytical Results Using the 0.5% Pb Threshold.............................................22 

10. Pb Level (mg/cm2

) at Which There Is a 50% Probability of a Positive Test Kit Result.......22 

11. Pb Level (Percent Pb by Weight )at Which There Is a 50% Probability of a Positive 

Test Kit Result....................................................................................................................23 

12. OSHA Study Results..........................................................................................................24 

13. Summary of Method of Usage for Test Kits Evaluated in RTI Pilot Field Study.................25 

14. False Negative and False Positive Rates for Field Evaluation of LeadCheck Kit ..............26 

15. False Negatives and False Positives at Pb Levels of Less Than and More Than 

1.0 mg/cm2 .........................................................................................................................29 

16. Pb Level Corresponding to a 95% Probability of a Positive Response for an 

“Average” Operator ............................................................................................................32 

17. Results of HUD Archive Testing on White-Lead-Based Paint............................................33 

18. Summary of Results for the Analysis of RTI Core Paint Materials Using the 

EM Science Reflectoquant.................................................................................................37 

19. Summarized Results for the Measurement of RTI Core Paint Materials Using the 

PaceScan 2000..................................................................................................................39 

20. Range of Recovery Values for the Colorimetric Test Kit Test............................................40 

21. Pooled Standard Deviation for Triplicate Analyses Performed within Each Test Kit 

Location..............................................................................................................................41 

22. Accuracy and Precision Values for Real-World and NIST SRM Samples .........................41 

23. Results of Regression Analysis Comparing ICP Results with Quantitative Test Kits.........42 

24. Results of Regression Analysis Comparing AAS Results with PaceScan Kit Results.......42 

25. NIST SRMs for Leaded Paint Films ...................................................................................44 

26. Summary of Studies Reviewed in This Issue Paper ..........................................................47 

27. Test Kit Response to Pb Ion in Solution: 100% Negative to 100% Positive ......................50 
vii 

List of Figures 

1. ICP results versus LeadCheck results (mg/cm2)................................................................27 

2. ICP results versus LeadCheck results (percent Pb). .........................................................28 

3. Probability of a positive response versus Pb level for LeadCheck – Type 1 on 

nonreactive and reactive substrates. .................................................................................30 

4. Probability of a positive response versus Pb level for MA Sulfide – Type 1 on 

nonreactive and reactive substrates. .................................................................................31 

5. Response of DNAzyme-based test kit using benchtop and portable colorimeters; 

ideal sensor defined by Rossiter et al. (2000)....................................................................34 

6. Plot of the Pb concentration measured by the EM Science Reflectoquant versus 

ICP-AES for RTI paint materials. .......................................................................................38 

7. Plot of the Pb concentration measured by the PaceScan 2000 versus ICP-AES for 

RTI paint materials.............................................................................................................40 
viii 
1

1.0 INTRODUCTION 

Lead (Pb)-based paint is a major source of Pb poisoning for children and also can affect adults. 

In children, Pb poisoning can cause irreversible brain damage, impair mental functioning, retard 

mental and physical development, and reduce attention span. In adults, it can cause irritability, 

poor muscle coordination, and nerve damage to the sense organs and nerves controlling the 

body. Pb poisoning also may cause problems with reproduction (such as a decreased sperm 

count) and also may increase blood pressure. Thus, young children, fetuses, infants, and adults 

with high blood pressure are the most vulnerable to the effects of Pb. 

Pb-based paint is a major source of Pb that poses this risk to children and adults. Pb-containing 

paint may be a direct hazard if eaten, but it poses its greatest hazard when it is broken down 

into small particles and becomes a component of house dust or soil around the house. It is 

these particles, which stick to the hands of children and are ingested through hand-to-mouth 

activity, that pose the most significant potential for harm. 

Some 38 million houses (Jacobs et al., 2002) in this country still contain leaded paint. The U.S. 

Department of Housing and Urban Development (HUD) has an ongoing major effort that 

includes grants to communities and citizen organizations for removal of Pb hazards from 

dwellings. This effort and the efforts of other groups, including commercial paint testing, control, 

and abatement firms, all need to analyze the paint in dwellings to determine if Pb is present at 

or above the levels of concern identified by the U.S. Environmental Protection Agency (EPA) 

and HUD (Title X, 1992; HUD, 1995). Those levels of concern are 0.5% Pb by weight or 1.0 mg 

Pb/cm2

, the Federal regulated levels. Some States and localities may use other definitions of 

Pb-based paint; for example, Wisconsin defines “lead-bearing” paint as surface coating material 

containing more than 0.06% Pb by weight or more than 0.7 mg Pb/cm2

 in the dried film of 

applied paint (Wisconsin Statutes, 2004). 

Methods of analysis for Pb in paint include portable X-ray fluorescence (XRF), anodic stripping 

voltammetry (ASV), atomic absorption spectrometry (AAS), inductively coupled plasma (ICP) 

emission spectrometry, and quantitative test kits. Homeowners also may perform Pb testing 

using spot or qualitative test kits specifically designed for in-home use by untrained people. An 

alternative is for the homeowner to collect a paint sample and send it to a commercial laboratory 

for analysis; kits for this purpose can be purchased that give guidance for collection of a paint 

sample and the materials for submitting it. 

Test kits offer the potential for performing field measurements that will indicate whether Pb 

levels in paint are above or below the Federal regulated levels. Suitable performance of these 

kits could lead to rapid decisions about the presence of unacceptable risk, faster and lower cost 

testing, immediate indication of need for some form of control or abatement, and real-time 

tracking of the effectiveness of performance of control or abatement. The Federal regulated 

level is defined as paint containing Pb at or above 1 mg/cm2

 or 0.5% by weight. For a test kit to 

The purpose of this issue paper is to address the availability and performance 

characteristics of portable lead test kits especially suited for lead in paint, procedures 

for evaluating the performance of these test kits, and the availability of performance 

evaluation materials suitable for test kits. Knowledge and understanding of these 

issues will provide a platform for identifying approaches or modifications that can be 

used with current or newly developed test kits for lead in paint to adjust their 

performance to meet the new Federal performance standards found in Lead; 

Renovation, Repair, and Painting Program; Proposed Rule (EPA, 2006). 
2

be recognized by EPA, it must meet the following performance standards and goals (from Lead; 

Renovation, Repair, and Painting Program; Proposed Rule [EPA, 2006]). 

• Has a demonstrated probability (with 95% confidence) of a false negative response to Pb 

levels above the regulated level of less than 5% 

• Has a demonstrated probability (with 95% confidence) of a false positive response to Pb 

levels below the regulated level of no more than 10% 

• Can be used reliably by a person with minimal training 

• Provides results within an hour 

• Costs less than $2 per test 

To further clarify whether these goals can be met, a study of the current status of test kits has 

been performed. The primary objectives of this study are to perform a literature search and 

prepare an issue paper discussing the availability and performance characteristics of portable 

Pb test kits especially suited for testing Pb in paint, procedures for evaluating the performance 

of these test kits, and the availability of performance evaluation materials suitable for test kits. 

This study included the following. 

• Conduct literature search and contact experts 

• Identify portable Pb test kits and their sources 

• Develop a matrix that presents the key operating parameters for each test kit identified 

• Locate in the literature and summarize performance evaluations, if available, of each test kit 

identified 

• Identify performance evaluation materials suitable for use with test kits 

• Describe protocols suitable for determining the performance of test kits, especially for Pb in 

paint 

1.1 Test Kits 

Test kits are analytical systems based on relatively simple measurement technologies. The 

most common type is based on the development of a color resulting from the reaction between 

Pb and some other chemical agent; this color can be noted visually or its intensity measured 

with a simple colorimeter. Test kits are generally of two types: (1) spot test kits (Sections 1.1.1 

and 3.1) and (2) semi-quantitative or quantitative test kits (Sections 1.1.2 and 3.2). 

Semi-quantitative test kits are those that give an approximate value for the Pb level. They 

typically work by visually comparing the intensity of the color formed with some standard chart 

of colors or through a color comparator. The quantitative test kits usually involve an instrumental 

measurement of the product of reaction with Pb. This may be measurement of the intensity of 

the colored product of Pb with rhodizonate or some other reagent or measurement of some 

other unique property of Pb, such as its electrochemical properties, using a Pb-ion-selective 

electrode. 

1.1.1 Spot Test Kits 

Qualitative spot test kits are those wherein the formation of a color is observed visually. The 

paint is either tested directly (i.e., on the substrate material to which it has been applied) or after 

removal from the substrate. The color-forming reagent may be applied directly on the paint or to 

a paint sample that has been treated with a reagent that releases the Pb from the organic paint 

matrix to some extent and, thereby, increases the potential for color formation. Spot tests have 

great potential to complement other laboratory and field methods currently in use. Spot tests 

currently are being used as a qualitative test for the presence of Pb (i.e., a level equal to a 

method-defined limit of detection). Nevertheless, the analytical performance and reliability of the 

tests remain unvalidated or incompletely validated. Spot tests often serve as an initial testing or 

screening tool, followed by portable XRF or laboratory analysis after considering the results of 

the spot tests. A spot test that meets the proposed Federal performance standards would be 
3

very useful in that it potentially provides a way to perform the tens of thousands of onsite 

analyses required for future work. There are, however, limitations to the spot tests, which 

include the following. 

• The technique is qualitative, so no analytical reference standards for accuracy and precision 

are available; performance will be judged by the rates of false positive and false negative 

results (Song et al., 2001). 

• The presence of ions other than Pb (e.g., barium) can give rise to positive results, so there is 

a built-in false positive factor. 

• Detection is by visual comparison of color changes, so the results are subjective and may be 

inconsistent. 

• Results for colored paints may be difficult to interpret. An observed darkening may be the 

result of wetting with the solution, rather than the formation of a colored precipitate. 

• Detection in layers below the surface may be affected by the briskness of application and, 

thus, extraction. This effort may not be reproducible. 

• Interpretation is often a function of available lighting. 

In the early 1990s, two principle chemistries were used for Pb spot tests: (1) reaction with 

sodium sulfide to form the dark gray or black lead sulfide precipitate and (2) reaction with 

rhodizonate to form a pink complex. These chemistries are discussed in more detail in the 

following subsections. 

1.1.1.1 Sodium Sulfide 

Detection. In the sodium sulfide test, a drop of sodium sulfide solution is placed on exposed 

layers of paint. Layers that contain Pb will turn gray or black as a lead sulfide precipitate is 

formed. In a test of this method at the Naval Civil Engineering Laboratory (Vind and Mathews, 

1976), positive results for Pb were observed at a minimum concentration of 0.5% (w/w). The 

authors stated that, even though the detection limit of the test was approximately the regulatory 

limit (0.5% [w/w]), detection of Pb at this level in darker paints would not be possible. This is not 

necessarily the case when one considers that, in pre-1978 housing, there likely are many layers 

of paint and layers of different colors; the dark sulfide may be difficult to differentiate from some 

layers but likely not all layers. 

Studies by McKnight et al. (1989) and Blackburn (1990) have shown inconsistencies in the 

detection limit of the sulfide-based spot test. Blackburn tested 377 paired paint chips. The 

concentration of Pb for one chip in each pair was determined by flame atomic absorption 

spectroscopy (FAAS) and converted to milligrams per square centimeter. The concentration of 

the other chip in the pair was determined using the spot test method. The author found 

variations in the color of the precipitates: black, gray, green, blue, brown, copper, and orange. 

The observation of black or gray precipitates was correlated with 96% of the "positive results." 

Blackburn observed positive results (black coloration) to increase with Pb concentration from 

28.3% at a concentration of 0.7 to 0.9 mg/cm2

 to 80.4% at FAAS concentrations of 

≥10.0 mg/cm2

. The frequency of negative results was found to be technician dependent. On 

wood substrates only, negative test results at 0.7 to 0.9 mg/cm2

 were 51.1%; whereas negative 

results at concentrations of ≥10.0 mg/cm2

 decreased to 20.5%. Blackburn (1990) concluded that 

the overall false negative results on wood were 25.0%. This is inconsistent with the findings of 

McKnight et al. (1989) who estimated the false negative results of sodium sulfide spot tests to 

be about 10%. 

Selectivity. A number of inorganic compounds contain metals whose sulfides are dark (see 

Table 1). Vind and Mathews (1976) and studies by Midwest Research Institute (1990) evaluated 

the formation of colored precipitates with sodium sulfide solution for inorganic materials having 

potential uses in paint formulations (biocides or pigments). The authors observed positive 
4

Table 1. Metallic Elements Having at Least One Black Sulfide 

Element Colors of Sulfides Some Uses of Compounds in Paints 

Antimony Black, red Pigment 

Bismuth Black, brown, gray Pigment 

Cadmium Black Pigment 

Chromium Black, brown, gray Pigment, corrosion inhibitor 

Cobalt Black, gray, red Pigment, drier 

Copper Black Biocidal pigment 

Iron Black, green, yellow Pigment 

Lead Black Pigment, drier, corrosion inhibitor 

Manganese Black, green, pink Pigment, drier 

Mercury Black, red Pigment, biocide 

Molybdenum Black, brown, gray Pigment, corrosion inhibitor 

Nickel Black, gray, yellow Pigment 

results for mercuric oxide, mercuric iodide, and phenylmercuric oleate, all of which are used as 

biocides. 

Cobalt naphthenate and manganese naphthenate, used as curing or drying agents, also turned 

black with the application of sodium sulfide solution. Bismuth trioxide changed from greenishwhite to light brown in the presence of the sodium sulfide solution. The most common pigments 

in older paints included Pb, chromium, iron, and cadmium; common driers included cobalt, Pb, 

manganese, and zinc (Gooch, 1993). Despite the plethora of reactions of different metals with 

sulfide, sulfide serves as a useful indicator for Pb in that Pb is usually the predominant metal in 

older paints. 

1.1.1.2 Sodium Rhodizonate 

Sodium rhodizonate forms a pink complex with Pb in acidic solutions (Feigl and Suter, 1942). It 

may be used to detect Pb in 

• paint, 

• dust, 

• soil, 

• dilute solutions, 

• ores and minerals, 

• alloys, and 

• pigments and glass. 

Detection. The test is rapid and sensitive. In evaluation studies performed at the Research 

Triangle Institute (RTI) (Luk et al., 1993b), four commercially available rhodizonate-based kits 

yielded a positive reaction to Pb ranging from about 0.5 μg Pb (absolute in solution) to 5 μg Pb, 

with the reproducibility being ±0.05 to ±0.5 μg, respectively. Consumer Reports (1995) 

presented levels yielding positive responses for several of the rhodizonate-based test kits as 

follows. 

• Lead Zone 5% 

• Know Lead 0.5% 

• LeadCheck 0.5% 

• Merck EM Quant 5% 
5

Selectivity. The rhodizonate is known to react with sulfate as found in plaster and wallboard. 

This reaction depletes the amount of rhodizonate available to react with the Pb and, thus, can 

cause false negative results. The National Institute of Occupational Safety and Health (NIOSH) 

Manual of Analytical Methods, Fourth Edition, 1996, Methods 7700 and 9105, lists Cd2+ and 

Sn2+ as interferences. The EM Quant Lead Test Catalog No. 10077 from Gallade Chemical 

Incorporated, Santa Ana, CA, lists the anions iodite, oxalate, sulfide, and sulfite and the cations 

Cu2+, Sr2+, Fe3+, and Ba2+ as significant interferences. Of these potential interferents, only 

cadmium, iron, and barium are likely to be found in old paints and, therefore, be potential 

problems. 

1.1.2 Semi-quantitative and Quantitative Test Kits 

Semi-quantitative and quantitative test kits generally measure the intensity of a Pb 

concentration-dependent parameter against some standard. A variety of kits involve reaction of 

Pb ion in solution to form a colored complex with a Pb-specific reagent; the intensity of the 

absorbance measured with a colorimeter gives a measure of concentration (see Section 3.2.3). 

Reflectometry is a technique wherein the intensity of the color complex is measured by 

reflectance of incident wavelength-specific light from the complex on a substrate into a detector 

(see Section 3.2.2). 

One quantitative test kit available is not based on color intensity measurement, but on the 

electrochemical reaction of Pb that has been dissolved to form the Pb ion, Pb2+ (see Section 

3.2.2). This method, ASV, involves reducing the Pb ion in solution to form Pb metal on an 

electrode (i.e., Pb2+ + 2 e → Pb0

). After a period of time, the Pb metal is rapidly oxidized back to 

the ion form in solution, and the electrical current associated with this oxidation is related to the 

concentration of the Pb ion in the original solution. 

1.2 Early Issue Papers 

In the early 1990s, EPA assigned RTI two tasks: (1) to write a paper that would lay out the 

required performance parameters for test kits and (2) to conduct outreach to producers of test 

kits. Test kit manufacturers were very responsive to these efforts, which had a positive effect on 

the direction of early test kit development; today’s kits are probably better because of this effort. 

The early work described here indicates the beginning of a concerted effort to advance the 

science and harmonize test kit performances. 

1.2.1 Proposed Performance Parameters 

In the first effort (EPA, 1991), performance requirements for test kits were proposed with 

respect to 

• sensitivity, 

• selectivity, 

• accuracy, 

• response time, 

• safety, 

• appearance, 

• reproducibility, and 

• stability. 

The requirements proposed are described as follows. 

Sensitivity. The optimum criteria for test kit sensitivity is the detection of Pb at the lowest 

concentration associated with adverse health effects (i.e., increases in blood lead levels). 

Criteria (EPA, 1991) were proposed for Pb in paint; these are shown in Table 2. Because a 

quantitative relationship between Pb-based paint and elevation of blood lead levels had not 
6

Table 2. Proposed Analysis Performance Criteria for Pb In Paint as of 1991 

Standards for New/Replacement Paint 

Reference Concentration 

 CPSC, FDA 600 ppm, 0.12 mg/cm2

Proposed Performance Criteria 

Concentration Level of Concern: 0.06 % (w/w), 600 ppm 

95% of results positive ≥ 0.045% (w/w), 450 ppm 

95% of results negative ≤ 0.015% (w/w), 150 ppm 

Standards for Abatement 

Reference Concentration 

HUD 1.0 mg/cm2

State of Maryland 0.7 mg/cm2

State of Wisconsin 0.7 mg/cm2

Proposed Performance Criteria 

Concentration Level of Concern: 0.7 mg/cm2

95% of results positive ≥ 1.0 mg/cm2 

95% of results negative ≤ 0.1 mg/cm2

Comments 

• No quantitative relationship between Pb level in paint and health effects had been established. 

• With pica activities, difficulty arises in transforming XRF values to average daily intake. 

• HUD considers 1.0 mg/cm2

 (5000 ppm) a positive XRF measurement for Pb and requires abatement at this 

concentration. 

• CDC considers 0.7 mg Pb/cm2

 paint a positive XRF measurement for Pb. 

• CPSC level of concern for new paint is 0.06% (600 ppm).

• FDA = Food and Drug Administration

been established, criteria for paint were proposed for both abatement and clearance on the 

basis of guidelines already in existence. For abatement, levels considered positive from an 

instrumental standpoint were used to propose measurement criteria. Concentrations of 

0.7 mg/cm2

 (positive by Centers for Disease Control and Prevention [CDC] standards) and 

1.0 mg/cm2

 (positive by HUD standards) were considered unacceptable risks (i.e., abatement is 

necessary) and should result in a positive detection. A minimum level of approximately one-fifth 

of the CDC “positive” concentration (i.e., 0.1 mg/cm2

) was proposed as negative for Pb. 

Clearance standards were proposed on the basis of the 1978 maximum level for Pb in new 

paint (600 ppm) proposed by CPSC, and consideration of abated paint as a dust source (i.e., a 

clearly positive concentration of 450 ppm). Accordingly, clearance performance criteria 

recommended were 95% positive results at 0.45% and 95% negative results at 0.15%. Results 

of evaluations of test kits showed that a threefold range from clearly negative to clearly positive 

results is achievable for total Pb in solution (Luk et al., 1991). Test kit sensitivity is limited by the 

ability to extract Pb from the medium. 

Selectivity. The test kits be selective for Pb over potential interferences. Through selection of 

the primary color-forming reagent; use of chemical agents to mask interferences; and other 

chemical parameters, such as pH; the selectivity ratio for Pb to any other potential interferences 

shall be 100 to 1. 

Accuracy. Test kits on the market were shown to have poor accuracy. Results (EPA, 1991) 

were found to depend on the ability to extract Pb from the matrix, which is a function of the Pb 

species and the physical form of the matrix, rather than of the concentration of Pb in the matrix. 
7

Criteria for accuracy, 95% of the results positive at a specified sensitivity, were believed to be 

achievable for concentrations proposed if test kit solutions extract Pb quantitatively (EPA, 1991). 

Response Time. The test kits develop full color or change within 30 s and be stable for a 

minimum of 1 h to allow for a delay in noting the results or confirmation, if needed. 

Safety. Hazard of materials (i.e., sodium rhodizonate) should be evaluated. Information on 

dermal effects, toxicity, etc., shall be indicated, if necessary, on enclosures similar to package 

inserts for medications or Material Safety Data Sheets for chemicals. Precautions and personal 

protection (e.g., gloves) shall be included if special handling needs are required. 

The use of fracture- or splatter-resistant containers is important. The design of containers is 

particularly important when kits contain solutions. Special considerations for child safety, such 

as child-proof containers and vials, must be given to kits used by homeowners. Testing 

solutions, strips, etc., shall be sealed so that they are inaccessible to children. 

Disposal instructions for solutions, paper strips, test ware (e.g., vials, cups, wands) shall be 

included in the test kit. Options, including flushing into the sanitary sewer or wrapping in 

newspaper for disposal in a landfill, shall be specified. 

Appearance. Warnings be included in the test kit about physical properties that may affect 

accuracy and reproducibility of the test kit, including change in color or reagents, precipitates, 

etc. 

Reproducibility. The test kits include some reference device or material to assure the 

reproducibility of the test kit. Options for this material include 

• a standard test solution or Pb-impregnated strip, and 

• a color chart or wheel. 

Reproducibility shall be ±10% between individual test kits and between production lots. 

Stability. Test kits be labeled with a production log number and an expiration date. Test kits 

shall have a shelf life of a minimum of 6 mo. 

1.2.2 Manufacturer Outreach 

In the outreach effort (Luk et al., 1992), manufacturer’s of five test kits ([1] Frandon Lead Alert, 

[2] Verify LeadTest, [3] Hybrivet LeadCheck. [4] Merck EM Quant; and [5] Lead Detective) were 

asked to review a draft of the report, “Evaluation of Lead Test Kits for Analysis of Paint, Soil and 

Dust,” (Luk et al., 1991) and two RTI/EPA documents, (1) “Options for a Lead Analysis 

Laboratory Accreditation Program” (Estes et al., 1991a) and (2) “Options for a Test Kit 

Certification Program” (Estes et al., 1991b) and to provide comments on the test kit evaluation 

report. Only three of the five companies successfully completed the outreach process. 

Those three companies all indicated a serious interest in being of service to their customers 

through the availability of a toll-free, 800 number. This interest also was demonstrated through 

their plans or willingness to clarify the instructions included with each kit. None of the 

manufacturers considered the reagents in their kits to be hazardous. None thought laboratory 

gloves were needed. Frandon, HybriVet, and Merck all stated that they had the capability to 

manufacture as many kits as could be sold. The Frandon test kit was designed for home use, 

whereas the HybriVet and Merck kits were designed for both home and professional use. 

HybriVet was promoting their kit as an adjunct screening tool to XRF, with their protocol for 

detection of more than 200 μg/ft2

 of Pb on surface. Also, all three manufacturers planned to 

develop and market quantitative kits. They also stated that the availability of reference materials 

would be extremely useful, both for development of new, quantitative kits and also as quality 

assurance materials for both qualitative and quantitative kits. Finally, all three manufacturers 
8

agreed that verification of test kit performance is desirable. However, there were reservations 

about a verification process slowing the development and marketing of new products. 

1.3 Preparation of This Issue Paper 

As noted in the introduction, EPA’s Proposed Rule Lead; Renovation, Repair, and Painting 

Program (EPA, 2006), provides the following performance standards and goals for a test kit to 

be recognized by EPA. 

• Has a demonstrated probability (with 95% confidence) of a false negative response to Pb 

levels above the regulated level of less than 5% 

• Has a demonstrated probability (with 95% confidence) of a false positive response to Pb 

levels below the regulated level of no more than 10% 

• Can reliably be used by a person with minimal training 

• Provides results within an hour and costs less than $2 per test 

The principle issue to be considered is whether test kits already available meet these standards 

of performance, and, if not, whether there is the potential for modified or newly developed kits to 

meet these standards. The principle purpose of this issue paper is to provide a detailed picture 

of the current status of test kits for Pb in paint, put in perspective with a limited history of their 

development and performance. 

This issue paper has involved several tasks. First, a literature search was performed, and 

experts and test kit manufacturers were contacted. From this effort, a matrix was produced that 

describes all spot and quantitative tests that have been identified. Second, reports of past 

studies of the performance of test kits were identified and reviewed; summaries of these studies 

are provided in this issue paper. Next, a search for standard test materials was conducted and 

also is reported on in this paper. Finally, methods for evaluation of test kits were identified and 

are described. 

2.0 AVAILABLE TEST KITS 

An extensive search for available test kits was performed. Sources of information included the 

Internet, lists of test kits in previous reports, and communication with those in the field. Table 3 

presents the results of this search in a matrix format. The parameters covered in this matrix are 

listed below. 

• Kit name or type 

• References 

• Description 

• Summary of method 

• False negative rate 

• False positive rate 

• Training required 

• Cost 

• Analysis time 

• Response range 

• Types of coatings and Pb compounds that can be tested 

• Interference 

• Hazardous materials 

• Target and current users 

Because of the scope of all this information, the table is organized in the following manner. The 

first page shows the first five columns (through false negative rate) for the first group of test kits. 
9

Then the second page shows the remaining columns for those same test kits (with the names of 

the test kits repeated for reference). The third and fourth pages show the same data for next 

group of test kits, and so on. 

The information for each parameter for each test kit was taken from the literature that comes 

with the kit, from manufactures or sellers of the kits, and from written reports of studies of the 

test kits. Information for many of the parameters for many of the kits is not available because it 

has not been determined by the manufacturers or by researchers evaluating the kits. In some 

cases, manufacturers have indicated the information is proprietary. Although a thorough search 

was performed, it is likely that not all studies have been identified. Table 3 does contain all wellknown brands of test kits. 

3.0 PREVIOUS STUDIES OF TEST KITS 

Following are summaries of several past studies of test kits. These summaries are provided to 

give an overview of the types of evaluations these kits have been subjected to and also to 

provide a history of the performance of the kits. They are presented to provide knowledge and 

understanding that hopefully will serve as a platform for identifying approaches or modifications 

that can be used with current or newly developed test kits for Pb in paint to adjust their 

performances to meet the new performance standards found in Lead; Renovation, Repair, and 

Painting Program; Proposed Rule (EPA, 2006). 

3.1 Spot Test Kits 

The majority of studies of test kits identified are focused on the spot test kits because the 

majority of the kits developed are spot test kits. They offer the simplest, fastest, and cheapest 

means of testing, and homeowners can use them, so they offer the greatest opportunity for 

retail sale and profit to the manufacturer. 

3.1.1 RTI Laboratory Evaluation 

In an early laboratory evaluation, RTI tested the performance of five spot test kits in the 

laboratory (Luk et al., 1993b). Through a search of the literature and trade journals and through 

contact with experts, the following five test kits were identified. 

(1) LeadCheck (Hybrivet Systems) 

(2) Verify LeadTest (Verify, Inc.) 

(3) Frandon Lead Alert (Frandon Enterprises) 

(4) Merck EM Quant (EM Science) 

(5) The Lead Detective (Innovative Synthesis Corp.) 

A limited study of these five kits was performed to identify both positive attributes and 

limitations. Tests were performed with trained analytical chemists or technicians, except for the 

nontechnical user tests (which are described below). The following tests were performed. 

• Response relative to test sample Pb content 

• Potential metal interferences 

• Potential salt interferences 

• Response to laboratory-prepared and real-world paint, dust, and soil samples 

• Color stability 

• Accuracy of use by nontechnical personnel 

Lower Level of Response. The first test determined the range of Pb content in test samples 

over which test kit responses went from negative to positive. This experiment was intended to 

estimate the identification limits (lower limits of response) of the kits. 
Table 3. Summary of Available Test Kits and Their Operational Parameters 

Kit Name or Type References Description Summary of Method 

Accukits, 970-330-4238 

Available from www.professionalequipment.com 

Sample is sent to a lab for atomic absorption or inductively coupled plasma-atomic emission spectrometry (ICP) analysis. 

The user sends a sample to the laboratoSW846 7000 methods are used, either AICP. Homeowners can send in wipes or samples. 

Acc-U-Test, South Shore Lead Paint Testing, 781-337-5546 

www.sslpt.com; Rossiter et al. (2000) 

Color change, sodium sulfide Place a drop of the reagent in a notch in 

paint and look for formation of a dark or color. 

Bionanotechnology, DzymeTech, Dr. Lu, 217-333-2619 

Lu (2005) Under development. Small Business 

Innovative Research Contract from EPA. Dzyme proposes to develop a spot test kit based on Dr. Yi Lu's work at University of Illinois. The technology is a catalytic DNAgold nanoparticle colorimetric sensor for Pb. 

DNAzyme is selective for Pb (II). Gold nanoparticles assembled by the DNAzymform blue aggregates; Pb causes substrcleavage, inhibition of assembly of nanoparticles, and red color formed. 

Cole’s Test, Cole Environmental, Sandra Cole, 216-961-7030 

Information from EPA Docket and U.S. patents 6800485 and 6489170 

Proprietary. Patented. Not yet commercially available. The test is based on the reaction of Pb with sodium rhodizonate under strong acid conditions. Dilute hydrochloric acid is used. 

Cole’s test forms a blue-purple color whis present. The reaction is immediate. Tsolutions are used—an acid and sodium rhodizonate. A positive paint chip for qucontrol (QC) would be provided. A color would be used for comparison. 

D-Lead, Esca Tech, 877-532-5323, Dan Askin 

www.esca-tech. com 

Two solutions. Color change. Trade secret but not patented. Originally developed for industrial applications but can be used by homeowners. 

Contact one surface with one solution athe second solution. Appearance of yellocolor indicates Pb. 

EM Quant, 888-830-9092 (number is for a distributor) 

Gallade Chemical Incorporated, www.emdchemicals. com, Gutknecht et al. (1997) 

Rodizonic acid; test strips and reagent available 

Pb reacts with rodizonic acid in an acidic solution (acetic acid is used) to form a recomplex. Graduations of 0, 20, 40, 100, and 500 ppm Pb available. The test deteionic Pb. 

 10
Table 3. Summary of Available Test Kits and Their Operational Parameters (cont’d.) 

Kit Name 

orType 

False 

Positive Training Cost Time 

Response 

Range 

Types of 

Coatings 

and Pb 

Compounds That Can Be 

Tested Interferences 

H

Accukits No data Unknown $12.95 Sample 

collection 

ICP or AAS range 

Paint None of 

significance 

N

Acc-U-Test 41% at 

1.0 mg/cm2 Required $12.95 5 min 0 to > 0.5% Paint Metals that form sulfide 

precipitates 

Sca

Bionanotechnology, DzymeTech 

No data; currently testing 

Two sensors are being investigated. With the colorimetric approach, the test would be a dipstick (yes or no answer) and a homeowner could use it. For the fluorescence sensor (quantitative answer), a trained inspector would use it. 

Unknown Testing is 

ongoing, but the sensing step takes about 2 min. The extraction step currently takes about 20 min. 

The color change is clearly visible at 1 mg/cm2. 

The range can be adjusted for the sensor or by using 2 sensors. 

Pb (II) Currently iron is 

one, but they are working to overcome the problem. 

D(svi

Cole’s Test No data Approximately 

5 min 

$0.25 per test to manufacture; not yet commercially available 

Immediate reaction 

“99.999%” accurate; low end of range around 0.05% 

Mainly paint None known, 

according to company. According to the patent, this test avoids interference from barium. 

Dhyac

D-Lead No data For the test, read 

the instructions. Taking a good sample is critical. 

$75/120 tests; three sizes available 

Immediate As low as 

20 μg Pb 

Paint, hands, ceramics, etc., for surfaces; the kit does not work for chromate. 

Dirt and bleach N

EM Quant Essentially 

0% 

None To be 

determined 

5 min >0.0+% Ionic Pb only Potentially red or 

pink paint 

N

11
Table 3. Summary of Available Test Kits and Their Operational Parameters (cont’d.) 

Kit Name or Type References Description Summary of Method 

First Alert, BRK, 800-323-9005 www.firstalert.com Can use for “Rapid Method” or 

“Patented Leach Method;” yellow, black, or brown on the swab tip indicates that Pb is present. 

For the rapid method, the swab is dippeindicator solution, then rubbed on the suleach test uses vinegar to leach the Pb btest. The company representative indicaof their information is available on their W

Frandon All-In-One (Card), 800-359-9000–number is now Caremark, not Frandon. EMS, 727-530-3602, sells a Pace Environs Lead Alert Professional Lead Test Kit; also Web site www.pactape.com has a Pb alert kit. 

Rossiter et al. (2000) Colorimetric with a test card Pink or red on the applicator tip or test c

indicates the presence of Pb. They recogrinding the sample. A leaching solution 

Full Disclosure (Surface Wipe), SKC, 724-941-9701, Connie Kelly 

SKC, www.skcinc.com 

Surface wipe with a color change if Pb is present; designed for occupational uses, including workers’ hands 

The wipe turns pink or red in the presenThe wipes also can be sent for atomic aspectrometry or anodic stripping voltammRhodizonate compound and acetic acid 

Hach LeadTrak Pocket Colorimeter II, 800-227-4224. Hach Co., P.O. Box 389, Loveland, CO 80539 

Simplified Testing for Lead and Copper in Drinking Water, Hach, Technical Information Series-Booklet 19, www.hach.com 

Colorimeter The sample is preserved and fixed with 

column is used to separate the Pb. pH is The sample is mixed with an indicator. Tread with the colorimeter. Uses 4-(2 pyrresorcinol as color-forming reagent. 

HazCat Lead in Paint Test Kit, David Mandeville, 800-543-5487. Associated with HazTech System, Inc., Mariposa, CA 

www.hazcat.com, Costa (1961) 

Chloranilic acid as indicator. A positive detection results in a brown precipitate. 

A pea-size amount of crushed paint is pwatch glass. Three drops of metal extrasolution and four drops of Pb test are adindicated by brown solution or precipitat

Home Free (MACS); Jim Richards, 800-622-7522 

Available from www.professional equipment.com and mall.ballparks.com 

Atomic absorption spectroscopy 

The user sends a sample to the laborato

 12
Table 3. Summary of Available Test Kits and Their Operational Parameters (cont’d.) 

Kit Name or 

Type 

False 

Positive Training Cost Time 

Response 

Range 

Types of 

Coatings 

and Pb 

Compounds That Can Be 

Tested Interferences 

Ha

M

First Alert No data Read the 

manual before use 

Locally owned hardware store, $9.99 

Up to 4 h As low as 

1 to 3 ppm. 

Paint, ceramics, dust, etc. 

Copper and bismuth are potential interferences. 

Sucau

Frandon All-In-One (Card) 

15% Unknown EMS sells 

the Frandon’s professional kit for $29.95. 

Unknown At a concentration 

of 0.3 mg/cm2, 

there is a 95% probability of a negative result. 

Paint Red paint may 

cause a problem. Barium may produce an orange response. Gypsum, plaster, and stucco may interfere. 

No

Full Disclosure (Surface Wipe) 

Unknown No more 

than 5 min training would be required. 

$29.95 for kit Immediate 

reaction 

18 μg is the lower limit of detection. 

Designed for testing hands; not meant for detecting lead chromate, alkyl Pb, or other less soluble Pb types 

Silver, cadmium, barium, mercury, and titanium 

Dilac

Hach LeadTrak Pocket Colorimeter II 

No data 1 h+ Set up is 

$300 to $1600; cost per sample is $4 to $5. 

3 min to set up; 10 min per test 

Minimum detection limit in the manual is 5 μg/L. Manual 

lists precision of 70 ± 10 μg/L. 

Detection limit of 2 μg/L; range of 

2 to 150 μg/L. 

Water The manual lists 

several metal interferences, including aluminum, copper, iron, and zinc. 

Bumi

HazCat Lead in Paint Test Kit 

Unknown Unknown $111 for 25 

to 100 tests 

Unknown Limit of 

identification is 5 μg Pb. 

Paint Co (II), Ag (I), Hg 

(I), Hg (II), Bi (III) 

Chac

Home Free (MACS) 

No data Unknown $21.95 Sample 

15 min, read 20 min 

Unknown Paint, water, soil Unknown Un

 13
Table 3. Summary of Available Test Kits and Their Operational Parameters (cont’d.) 

Kit Name orType References Description Summary of Method 

Know Lead Kit by Carolina Environment, 704-598-1397, 800-448-LEAD 

Unable to contact; neither phone number was working. 

Lead Alert Wipe/Sanding Test Kit (according to OSHA notes, Lead Alert was developed by Frandon Enterprises, formerly sold by Sensidyne, owned by Pace Environs; number for Pace Environs from Web, 467-7578, no answer, no matches with AnyWho)–EMS, 727-530-3602, sells a Pace Environs Lead Alert Professional Lead Test Kit; see more details under Frandon. 

EMS, www.emssales.net; PPI Pace, www.pactape.com 

Color change According to the OSHA Web site

includes an indicating solution, lesolution, and indicating tablet. 

LeadCheck (Hybrivet), 800-262-LEAD www.leadcheck.com, 

Luk et al. (1993b), EPA (1995b), Gutknecht et al. (1997), Rossiter et al. (2000) 

Colorimetric The swab contains two ampules, 

broken open and mixed. The swasqueezed until yellow liquid comedistinctive pink or red color forms present. 

Chromate Check (Hybrivet), 800-262-LEAD, Marcia Stone 

www.leadcheck.com Colorimetric Lead chromate is not often used 

household paints, but may be foumarine or industrial paints. A pink color change indicates the presenchromate pigments. 

Lead Detective, 617-965-5653 www.gis.net/~mtf/ 

tldhome.htm 

Sodium sulfide solution Sodium sulfide is mixed with pain

present, the sample turns black. 

JNJ Lead Detector, 800-554-9994 www.jnj-industries.com The kit includes 

LeadCheck test swabs, detecting powder, acetic acid extraction solution, and developing solution. The Web site has all of the information, the representative said. JNJ_Industries.com 

Pink or red color develops if Pb is Positive wipes and swabs can be for quantitative analysis. 

Lead Inspector (Abotex), 800-268-LEAD 

www.leadinspector.com Sodium sulfide solution The swab is dipped into the indic

The surface is rubbed with the swchange indicates that Pb is prese

 14
Table 3. Summary of Available Test Kits and Their Operational Parameters (cont’d.) 

Kit Name 

orType 

False 

Positive Training Cost Time 

Response 

Range 

Types of 

Coatings 

and Pb 

Compounds That Can Be 

Tested Interferences 

H

Know Lead Kit 

―

― $11.95 for four 

(old data) 

―

―

―

―

Lead Alert Wipe/ Sanding Test Kit 

19% to 20% None $20/kit according 

to OSHA Web site 

5 min per test 

0.5 μg (-) to 0.7 μg (+) 0.6 mg/cm2 (-) to 1.2 mg/cm2 (+) 

Paint Thallium, 

silver, cadmium, tin 

N

LeadCheck (Hybrivet) 

20% to 70%. See EPA (1995b), Gutknecht et al. (1999), Rossiter et al. (2000) 

None Local Home 

Depot, $5.67; locally owned hardware store $6.99; EcoKitchen sells a four-pack for $9.99. 

Less than 1 min 

0.38% w/w 0.5 μg (-) to 1 μg (+) 

1.2 mg/cm2 (-) to 

1.9 mg/cm2 (+) 

Wood, paint, metal, ceramics, vinyl, costume jewelry, etc. 

Potentially red or pink paint 

N

Chromate Check (Hybrivet) 

No known cross reactions 

Read and follow directions 

$39.95 for eight; lower if more are purchased; expect the price to come down 

Immediate reaction 

0.5 μg is the low end. 

Plated surfaces and paints; chromate 

No known A

hm

Lead Detective 

40% to 70% Required $29.95 5 min 0.5 μg (-) to 

2 μg(+) 

Paint Metals that 

form sulfide precipitates 

Sc

JNJ Lead Detector 

Same as LeadCheck 

None 5 min Same as 

LeadCheck 

Paint Potentially red 

or pink paint 

N

Lead Inspector (Abotex) 

Copper, bismuth, and iron 

 Eight-pack for 

$12.99 

Immediate reaction. 

1-ppm detection limit 

Any surface–vinyl, paint, ceramic, etc. 

Copper, bismuth, iron 

 

 15
Table 3. Summary of Available Test Kits and Their Operational Parameters (cont’d.) 

Kit Name orType References Description Summary of Method 

MacLellan Water Technology 

William Vanderwilp, 800-200-0865, www.mwater.ca 

Color change Fill pipette with water; add the test 

turns black if greater than 15 ppb. 

Palintest SA-1000 Scanning Analyzer, 800-835-9629, George Belarski 

www.palintestusa.com; Sussel and Ashley (2002) 

Voltammetry, disposable electrode The test sample is mixed with a 

conditioning tablet in a tube. The electrode is immersed in the sampl

Pro-Lab, 800-427-0550 www.prolabinc.com Impregnated test pad. No additional 

information that the company representative could send. 

The test pad is moistened and then rubbed over the surface. Pink or pucolor indicates the presence of Pb. 

PurTest Lead Test for Water 

www.silverlakeresearch.com Immunoassay test Add Lead-a-Finders to water. Place 

strip in reaction bottle. Pink line appon strip if Pb is greater than 15 ppb. 

Rapid immunochromatographic strip tests, Silver Lake Research, Mark Geisberg, 888-438-1942 

www.silverlakeresearch.com Under development. Small 

Business Innovative Research Contract from EPA. Silver Lake intends to develop a paint test strip using immunoassay. They have an immunoassay test for water (see above). 

The test is still under development. 

SenSafe Lead Paint Test Kit 

www.sensafe.com Same as Watersafe below Same as Watersafe below 

Watersafe, Silver Lake, 888-438-1942 is a distributor, Industrial Test Systems is the manufacturer, 888-861-9712 

Industrial Test Systems, Inc., www.sensafe.com; Watersafe, www.watersafetestkits.com 

Test strips with dithizone Vinegar (reagent A) is used to extra

the Pb. Dithizone is used as a color indicator. Pink is indicative of Pb. 

 16
Table 3. Summary of Available Test Kits and Their Operational Parameters (cont’d.) 

Kit Name 

orType 

False 

Positive Training Cost Time 

Response 

Range 

Types of 

Coatings 

and Pb 

Compounds That Can Be 

Tested Interferences 

Ha

Ma

MacLellan Water Technology 

No data None Paint $14.99, soil 

$24.99, water $23.99 

10 min > 600 ppm 

and > 5000 ppm 

Water Unknown Unk

Palintest SA-1000 Scanning Analyzer 

No data 1 to 2 h $1028 for 

instrument with sensor pack 

Collection, extraction, 10 min measure 

2 to 100 μg/L Water only for 

the 1000 

None Extr

reag

Pro-Lab No data Read the 

instructions before use 

Locally owned hardware store, $9.99 

5 min Unknown Paint, 

ceramics, etc. 

Unknown No 

PurTest Lead Test for Water 

None observed 

Unknown $14.95 Within 

10 min 

At 13 ppb 10/10 are negative; at 18 ppb, 10/10 are positive 

Water No crossreactivity 

observed. 

Unk

Rapid immunochromatographic strip tests 

No data No needed 

training is anticipated. 

Planned to be under $5 

Expected to take under 10 min 

Unknown Paint Unknown No 

SenSafe Lead Paint Test Kit 

Same as Watersafe below 

Same as Watersafe below 

Same as Watersafe below 

Same as Watersafe below 

Same as Watersafe below 

Same as Watersafe below 

Same as Watersafe below 

SamWatbelo

Watersafe No data Unknown $14.95 for 10 Within 

5 min 

At 600 ppm, 80% read positive. Range of 600 to 5000 ppm 

Lead chromate would not be extracted with vinegar and would not be detected. 

Zinc, cadmium, silver, tin, gold, molybdenum, and chromium may give a positive result. Nitrate and chloride may reduce sensitivity. 

Unk

 17
18

Following instructions provided with the test kits, each brand of kit was tested with solutions 

prepared with Pb(NO3)2 and PbCl2 to determine range of response. The test kits were reacted 

with 10 to 80 mL quantities of Pb solution from well below the point of color development to well 

above the point of color development. The test sample Pb content ranges corresponding to all 

negative responses to all positive responses are given in Table 4. 

Table 4. Test Kit Response to Pb2+ in Solution (All Negative to All Positive) 

Test Kit Pb(NO3)2 PbCl2

LeadCheck (original and new) 0.5 – 1.0 μg <0.4 – 0.8 μg 

Verify LeadTest 0.1 – 0.3 μg <0.1 – 0.2 μg 

Frandon Lead Alert 0.5 – 0.7 μg 0.1 – 0.3 μg 

Merck EM Quant (A) 0.5 – 0.6 μg NA 

Lead Detective Kit 0.5 – 2.0 μg 0.5 – 1.0 μg 

Based on these results, the kits rank as follows from lower level of response to higher. 

(1) Verify LeadTest (0.3 μg/g) 

(2) Merck EM Quant (A) (0.6 μg/g) 

(3) Lead Alert (0.7 μg/g) 

(4) LeadCheck (1.0 μg/g) 

(5) Lead Detective (2.0 μg/g) 

The chemical form of the Pb solution affects the responsiveness of the kits. This effect may be 

result from a combination of competition for complexation of Pb2+ by species other than 

rhodizonate ion and/or changes in pH or ionic strength. The size of the range over which 

rhodizonate-based kits went from all negative to all positive varied from 0.1 μg for the Merck EM 

Quant A (all negative at 0.5 μg to all positive at 0.6 μg) to 0.5 μg for the LeadCheck (all negative 

at 0.5 μg to all positive at 1.0 μg). 

Metal and Salt Interferences Tests. Paints, dusts, and soils may contain metal species other 

than Pb that react with the rhodizonate ion or sulfide to form a colored product and thus yield 

false positive results. Other species in the samples may inhibit color formation by reacting with 

the Pb or causing shifts in pH or ionic strength and thus yield false negative results. 

Color-forming (positive) interferences by metals were investigated for the Frandon Lead Alert kit 

using atomic absorption standard solutions. The Frandon Lead Alert kit was used because it 

appeared to represent the average rhodizonate-based kit. The standard solutions were usually 

acidic (2% HNO3, dilute HCl) as were the kit reagent; thus the test conditions were assumed to 

be acidic. When nominally 100 μg (100 μL, 1000 ppm) of potentially interfering metal ions were 

put in contact with the test element (i.e., swab) of each kit, only Ba2+ (which gives an orange 

color with Pb) and Ni2+ yielded responses that could be interpreted as positive for Pb. Feigl and 

Suter (1942) reported that Ag1+,Hg2+, T11+, Pb2+, Cu2+, Sn2+, Zn2+, Ba2+, and Sr2+ all gave 

responses to sodium rhodizonate in neutral and/or pH 2.8 solution. Their test procedure 

involved mixing high levels of the metal (1%, 10,000 ppm) with 0.2% sodium rhodizonate, which 

could account for the difference in results. They reported that the selectivity of sodium 

rhodizonate favors Pb2+ over the majority of these metals and, in particular, that the selectivity 

for Pb over barium is 10,000 to 1. The sulfide-based Lead Detective kit tested with these same 

samples showed responses to Ag1+, Cd2+, Co2+, Cu2+, Fe3+, Hg2+, Ni2+, and Ti2+, all of which are 

known to form insoluble sulfides. Both high levels (2000:1, Cl-

:Pb2+) and moderate levels (200:1, 

Cl-

:Pb2+) of chloride (as NaCl) were found to result in decreased response (negative 

interference) for the Frandon Lead Alert, Verify LeadTest, and Lead Detective kits. Other salts 

were tested as possible interferences. A series of solutions was prepared with different 
19

concentrations of NaNO3, KNO3, Na(C2H3O2), and K(C2H3O2) mixed with 1 μg of Pb2+ and tested 

in duplicate using the LeadCheck test kit. The purpose for testing these materials was that they 

had potential for use as buffers, which might be needed to make Pb paint extracts compatible 

with test kits chemistries. The Na1+ (or K1+) to Pb2+ ratios at which negative interferences 

occurred are as follows. 

Compound Na1+(or K1+):Pb2+ Ratio 

NaNO3 1000:1 

KNO3 1300:1 

Na(C2H3O2) 200:1 

K(C2H3O2) 200:1 

Thus, it appears that the sodium and potassium salts interfere, although it is not clear if the Na1+

and/or K1+ interfere. The effect of the salts may be a result of a change in ionic strength. The 

acetate presents even a greater extent of interference, which may result, in part, to a pH effect 

or formation of a lead acetate complex. 

Response to Laboratory-Prepared Paint Films. After tests with National Institute of 

Standards and Technology (NIST) Standard Reference Materials (SRMs), the test kits were 

further challenged by measuring responses to laboratory-prepared paint films (EPA, 1995a). 

Seven oil-based paint films spiked with white lead were prepared. Following kit instructions, 

paint sections averaging 1.1 cm2

 in area were tested. Concentration ranges over which the color 

appeared (i.e., all negative to all positive) are given in the Table 5. Because a limited number of 

paint films were prepared and used, transition curves (response versus concentration) were not 

well defined. 

Table 5. Test Kit Response to Pb in Paint Films (All Negative to All Positive) 

Test Kit Response Range 

LeadCheck (original) 1.9 – 2.6 mg/cm2 

LeadCheck (new) 1.2 – 1.9 mg/cm2 

Verify Lead Test 0.6 – 1.2 mg/cm2

Frandon Lead Alert 0.6 – 1.2 mg/cm2

Merck EM Quant (A) 1.2 – 1.9 mg/cm2

Lead Detective Kit <0.11 mg/cm2 (i.e., transition occurs below 0.11 mg/cm2) 

Color Stability Tests. A concern with the test kits was the rate of formation and stability of the 

color formed as a result of a positive response. Slow formation or rapid fading of the color could 

lead to a positive response being interpreted as a negative response. To test color formation 

and stability, the rhodizonate-based kits were tested with respect to time stability of the color 

developed. When exposed to amounts of Pb in solution just above the detection limit, only the 

Verify LeadTest and EM Quant Method A kits showed fading of the color from pink to yellow 

within 30 min. All kits showed no fading for at least 15 min after reaction with Pb.

Nontechnical User Tests. The test kits were designed for use by homeowners or 

professionals. Any improper use of the kits could affect the outcome of the tests. Therefore, 

ease and accuracy of use were tested by having nontechnical personnel use the kits while 

being observed by an experienced chemist. Two nontechnical staff members were provided 

with kits, written procedures, and RTI-prepared paint films for analysis. Each was instructed to 

perform duplicate analyses. There was considerable variation in the results, as shown in 

Table 6. 
20

Table 6. Results of Nontechnical User Tests 

Number of Negative and Positive Responses 

Test Kit Tester #1 Tester #2 

Test Paints (1.6 mg/ cm2) Negative Positive Negative Positive 

LeadCheck (new) 1 1 2 0 

Verify LeadTest 2 0 0 2 

Frandon Lead Alert 0 2 0 1 

Merck EM Quant 4 0 3 1 

Lead Detective 0 2 0 2 

Example problems noted by an experienced observer included those that follow. 

• Not following instructions 

• Confusion over the order of use of the two reagent tubes in the LeadCheck kit 

• Variation in firmness of rubbing paints 

• Stirring with the reaction zone of the Merck Em Quant test strips rather than the “upper end” 

as called for in the instructions 

Relationship to Proposed Performance Criteria (EPA, 1991). EPA had developed target 

criteria for performance of the test kits for different media (Estes et al., 1991b). The approach 

proposed a 95% negative response at levels corresponding to minimal known health effects or 

not requiring regulatory action and a 95% positive response at levels corresponding to 

suspected significant health effects or requiring regulatory action. The target and actual results 

are shown in Table 7, which shows that the measured ranges of response to paint (negative to 

positive) were higher than the proposed target levels for all the rhodizonate-based kits. The 

opposite is true for the sulfide-based Lead Detective kit, which had a response range (negative 

to positive) below target levels. 

Table 7. Comparison of Target Performance Criteria (EPA, 1991) and 

Actual Performance Results on Paint (Luk et al., 1993b) 

Test Kit 

Early Target EPA 

Performance Criteria Actual Performance Results 

LeadCheck (new) 95% positive at 0.7 mg/cm2

95% negative at 0.1 mg/cm2

All positive at 1.9 mg/cm2

All negative at 1.2 mg/cm2

Verify LeadTest 95% positive at 0.7 mg/cm2

95% negative at 0.1 mg/cm2

All positive at 1.2 mg/cm2

All negative at 0.6 mg/cm2

Frandon Lead Alert 95% positive at 0.7 mg/cm2

95% negative at 0.1 mg/cm2

All positive at 1.2 mg/cm2

All negative at 0.6 mg/cm2

Merck EM Quant 95% positive at 0.7 mg/cm2

95% negative at 0.1 mg/cm2

All positive at 1.9 mg/cm2

All negative at 1.2 mg/cm2

Lead Detective 95% positive at 0.7 mg/cm2

95% negative at 0.1 mg/cm2

All positive at 0.6 mg/cm2

All negative at 0.1 mg/cm2

The general conclusions from this earlier study (Luk et al., 1993b) were as follows. 

(1) The kits generally respond to less than 1 μg of Pb2+ in solution. 

(2) Positive interferences were not found for the rhodizonate kits for the limited set of paint, dust 

and soil samples used in this study. However, barium, which yields a “pinky” orange color 

with rhodizonate, may be interpreted by some as Pb. 
21

(3) The dark colors of certain dust samples masked observation of formation of lead sulfide at 

low levels with the Lead Detective Kit. Positive responses with the Lead Detective resulted 

from Ag+

, Co2+, Cu2+, Fe2+, Fe3+, Hg2+, Ni2+, and Tl2+. Many of these metals may be found in 

paints, dusts, and soils. 

(4) All kits showed adequate stability (>15 min) of the developed color. 

(5) Tests with untrained, nontechnical personnel showed significant variability in usage and, 

consequently, in results. 

(6) The measured response ranges (negative to positive) of the rhodizonate-based kits were 

generally above the targeted ranges set by EPA. The sulfide-based Lead Detective kit 

yielded positive responses to “blank” paint (i.e., with no Pb added), and, therefore, for RTI 

test paint films, response ranges were below the targeted ranges. 

Based on the results of this limited study, the rhodizonate kits were considered to have 

adequate sensitivity to measure available Pb in solution to meet the EPA target criteria. That is, 

the chemistry of the kits allowed easy detection of Pb at the lower levels of concern, provided 

that the Pb is available to react with the test kit reagent(s). The sulfide-based kit responds to 

levels below the target level for most samples. 

The issues addressed in this work included the following. 

• False positive and negative results 

• Interferences 

• Need for training 

3.1.2 HUD/QuanTech Field Study 

Midwest Research Institute and QuanTech, Inc., performed a large field study in 1993 that 

included evaluation of portable XRF and field test kits (EPA, 1995b). The study was conducted 

in Louisville (pilot study), Denver, and Philadelphia. The study involved both multifamily and 

single-family dwellings. Including those locations in the pilot study, a total of 1290 individual test 

locations on six substrate types in 22 housing units were tested. The breakdown of testing 

locations by substrate was as follows: 93 brick, 226 concrete, 124 drywall, 217 metal, 242 

plaster, and 388 wood. 

The test kits in this study represented the range of kits available at the time the study was 

conducted. Test kits from five different manufacturers were tested in this study: three 

rhodizonate based kits, two sodium sulfide based kits, and one proprietary kit. The rhodizonatebased kits included were LeadCheck and the sanding and coring versions of Lead Alert; the 

sodium sulfide kits were Lead Detective and the Massachusetts State-approved kit. The pilot 

study also included the Lead Zone kit, which uses proprietary chemistry. The results of the spot 

tests performed in the field were reported as either negative or positive. Paint was taken from 

the 1290 test locations and returned to the laboratory for analysis for Pb using acid digestion 

and measurement using ICP. These ICP results were then used to evaluate the test kits 

responses. 

Table 8 shows overall false positive and false negative rates for the test kits compared to 

laboratory analytical results using the 1-mg Pb/cm2

 threshold. Table 9 shows the corresponding 

rates for the 0.5% threshold. 

One immediately notes a great deal of variability with these spot tests. For example, for both the 

1.0-mg/cm2 and the 0.5% thresholds, false negative percentages vary from a few percent to 

more than 50%. Also, the high levels of false positive results indicate the spot test kits are very 

sensitive and are responsive to amounts of Pb that are effectively less than the threshold 

values. 
22

Table 8. Overall False Positive and False Negative Rates for Test Kits Compared to 

Laboratory Analytical Results Using the 1.0 mgPb/cm2

 Threshold 

Test Kit False Positive Percentage False Negative Percentage 

LeadCheck 46% 6% 

Lead Alert: Coring 15% 24% 

Lead Alert: Sanding 9% 53% 

Lead Detective 36% 23% 

Lead Zone 28% 14% 

MA Sodium Sulfide 65% 1% 

Table 9. Overall False Positive and False Negative Rates for Test Kits Compared to 

Laboratory Analytical Results Using the 0.5% Pb Threshold 

Test Kit False Positive Percentage False Negative Percentage 

LeadCheck 42% 11% 

Lead Alert: Coring 11% 36% 

Lead Alert: Sanding 19% 67% 

Lead Detective 32% 27% 

Lead Zone 25% 25% 

MA Sodium Sulfide 62% 6% 

It is possible to have interferences from the substrates as described in Section 3.1.1. The 

calcium in plaster apparently ties up the rhodizonate resulting in false negatives for kits based 

on this reagent. On the other hand, metals such as iron react with sulfide, and, therefore, a steel 

substrate will lead to false positives with kits based on the sulfide reaction with Pb. In this study, 

as noted above, the paint samples were taken from a variety of substrates. Table 10 shows the 

Pb level in mg/cm2

 at which there is a 50% probability of a positive test kit result, as estimated 

from a statistical model developed in this study. Table 11 shows the Pb level in percent by 

weight. These values represent the 50:50 point or inflection in the normal response curve. One 

sees very few combinations of test kit and substrate yielding 50:50 points at either 1.0 mg/cm2

or 0.5% Pb. 

Here too, one sees that the substrate has an impact on the results for the individual spot test 

kits, and, again, there is great variability between the spot test kits. 

Table 10. Pb Level (mg/cm2

) at Which There Is a 50% Probability of a 

Positive Test Kit Result 

Test Kit Brick Concrete Drywall Metal Plaster Wood 

LeadCheck 0.02 0.19 1.14 0.34 0.13 0.03 

Lead Alert: Coring 0.33 1.84 NA 0.65 NA 0.77 

Lead Alert: Sanding NA NA NA NA NA 1.24 

Lead Detective 0.05 0.60 NA 0.55 0.98 0.20 

Lead Zone 0.08 1.38 0.31 0.82 0.71 0.15 

MA Sodium Sulfide 0.01 0.01 0.08 0.08 0.02 0.04 
23

Table 11. Pb Level (Percent Pb by Weight) at Which There Is a 50% Probability of a 

Positive Test Kit Result 

Test Kit Brick Concrete Drywall Metal Plaster Wood 

LeadCheck 0.02 0.16 0.56 0.32 0.14 0.07 

Lead Alert: Coring 0.13 1.14 NA 1.09 NA 0.97 

Lead Alert: Sanding NA 0.88 NA NA NA 1.68 

Lead Detective 0.01 0.33 NA 0.63 0.58 0.38 

Lead Zone 0.07 0.49 0.35 1.03 0.44 0.26 

MA Sodium Sulfide 0.01 0.01 0.13 0.08 0.02 0.09 

High levels of Pb were not always detected with complete certainty using test kits. In a number 

of cases, the limiting probability of a positive test kit result was much lower than the desired 

value of 100%. This occurred for four of the six kits: Lead Alert (Coring) on metal; Lead Alert 

(Sanding) on concrete, metal, and wood; Lead Detective on concrete, metal, and plaster; and 

Lead Zone on plaster. 

The principle issue addressed in this work was the following. 

• False positive and negative results 

3.1.3 OSHA Study 

In an OSHA study (Adler, 1994; www.osha.gov/SLTC/leadtest/leadkits.html), the LeadCheck 

and Lead Alert All-in-One Professional kits were evaluated. Interference tests showed that 

barium yielded an orange color, which could be misinterpreted, and that gypsum, plaster dust, 

and stucco yielded negative interferences with these kits. Samples tested in this study included 

soluble Pb films in Petri dishes and paint from wood and plaster of older homes. Soluble salt 

films were prepared in Petri dishes at 0.1, 0.6, 1.0, 1.4, and 24 mg/cm2

. Both test kits showed 

positive responses at the 0.1 mg/cm2

 level. The expected values for the real-world paints were 

determined using inductively coupled plasma-optical emission spectrometry (ICP-OES) and 

AAS. Some of the results are presented in Table 12. 

From experiments both with the Petri dish films and the real-world paints, one can see the kits 

demonstrate their “protective” nature and respond to well below 1 mg Pb/cm2

 and 0.5% Pb. 

The issues addressed in this work included the following. 

• False positive and negative results 

• Interferences 

3.1.4 Laboratory Evaluation of the LeadCheck Test Kit 

The LeadCheck test kit was evaluated by Scharman and Krenzelok (1996). These researchers 

tested 26 paint chip samples in triplicate following the manufacturer’s instructions. The samples 

ranged from <0.00007% to 28.0%, as determined by AAS; 14 of the samples contained less 

than 0.5% Pb. A false positive was defined as a failure of the pink or red color change when the 

paint sample contained more than 0.5% Pb. The results were reported as “sensitivity” and 

“specificity,” where 

Sensitivity = (# true positives)/(# true positives + # false negatives), and 

Specificity = (# true negatives)/(# true negatives + # false positives). 
24

Table 12. OSHA Study Results 

Paint Source LeadCheck Results Lead Alert Results 

ICP Analysis 

(wt%) 

Cut made at angle into 

paint - intense pink. 

Pealed paint, side adjacent 

to wood - intense pink 

Total Pb test - immediate dark pink color on 

swab 

Garage (green 

paint) (home #1) 

Surface test - immediate 

distinct pink on swab 

Surface test - immediate distinct pink on 

swab 

Pb 3.1 

Zinc 14 

Total Pb test - no pink color observed on 

swab. 

Surface test, side of paint 

formerly toward wood 

(dirty), cleaned with wet 

wipe - distinct pink Surface test, side of paint formerly toward 

wood (dirty), cleaned with wet wipe - faint 

pink, obscured by dirt 

Paint chips from 

fence (home #1) 

Surface test, side of paint 

away from wood - no pink 

Surface test, side of paint away from wood - 

no pink color observed. 

Pb 0.03 

Zinc 3.0 

Total Pb test - no pink color observed on 

swab. 

Surface test, side of paint formerly toward 

wood (green) - faint but distinct pink on swab 

Paint chips from 

bottom of doorpost 

outside living room 

door (home #2) Surface test, side of paint 

formerly toward wood 

(green) - pink patches on 

paint 

Surface test, side of paint away from wood 

(white) - no pink, even after 15 min 

Pb 0.14 

Zinc 6.9 

At room temperature, the sensitivity was found to be 91.7% and the specificity to be 77.8%. 

Similar to other studies, the false negatives were in the range of 5 to 10% and the false 

positives were in the range of 20% to 30%. 

The principle issue addressed in this work was the following. 

• False positive and negative results 

3.1.5 RTI Pilot Field Study 

A pilot field study (Gutknecht et al., 1997) was conducted for EPA that served as means of 

establishing procedures for a larger field study to follow (see Section 3.1.7). The research 

involved the evaluation of three brands of portable XRF instruments, seven qualitative test kits, 

and a quantitative colorimetric test kit. The tests were conducted on a set of nine wood cabinet 

doors and nine locations on a painted fiberboard wall in residential dwellings in Durham, NC. 

Paint samples returned to the laboratory were analyzed using microwave digestion and 

inductively coupled plasma emission spectrometry (MW/ICP). This method is well established 

(Binstock et al., 1991). 

The method of sample preparation was critical. In this laboratory study, the paint from the wood 

was first ground using a mortar and pestle. This ground material showed the presence of flecks 

of paint, probably a latex overcoat that did not readily grind into fine powder. When this same 

paint was ground at dry ice temperature, a finer powder was obtained. The cryogenic grinding 

reduced the standard deviation of the MW/ICP analyses by about 80% relative to that achieved 

with the mortar and pestle. 

The variability between test point locations determined by MW/ICP was considerable. The Pbin-paint-on-wood levels varied from 3.30 + 0.02% (1.73 + 0.01 mg/cm2

) to 4.79 + 0.12% (2.40 +

0.06 mg/cm2

), and the Pb-in-paint-on-fiberboard levels varied from 1.34 + 0.21% 

(2.26 + 0.36 mg/cm2

) to 1.97 + 0.19% (2.14 + 0.21 mg/cm2). 
25

Seven qualitative kits were selected for testing. Each kit was tested on three different 1 x 1-in 

squares in the same location used for the quantitative kit test. The test area, which was adjacent 

to the area used for XRF measurements and collection of paint for MW/ICP analysis, was 

2 x 12 in and divided into 24 1 x 1-in squares. Of the 24, 3 squares were used for the 

quantitative kit and 21 squares were used for the qualitative test kits; the individual squares 

were assigned randomly to the different kits. 

The kits tested were as follows. 

Sulfide Based 

• Accu-U-Test 

• Lead Detective 

• Lead Inspector 

Rhodizonate Based 

• EM Merck 

• Frandon Lead Alert 

• LeadCheck 

• Frandon-All-in-One 

Table 13 summarizes the method of usage of these kits. 

Table 13. Summary of Method of Usage for Test Kits Evaluated in RTI Pilot Field Study 

Sample Form Method of Testing Brand of Kit 

Surface of paint Press test strip EM Merck 

Rub with swab Frandon Lead Alert 

LeadCheck 

Acc-U-Test 

Notch paint and test 

Lead Detective 

Invasive 

Core paint and test Frandon All-in-One 

Extract into solution Lead Inspector 

Five of the seven test kits showed all positive responses to all the tests for both the paint on 

wood and the paint on fiberboard. The EM Merck and Frandon Lead Alert showed a mixture of 

negative and positive responses to the paint on wood and all negative responses to the paint on 

fiberboard. This difference is due in large part to the method of testing. When the invasive 

method of notching was used with the EM Merck and Frandon Lead Alert kits, the paint on the 

wood yielded all positive responses for these two brands; using the invasive technique of 

notching resulted in some positive responses on the fiberboard using the EM Merck kit and all 

but one positive response using the Frandon Lead Alert kit. 

The principle issue addressed in this work was the following. 

• False positive and negative results 

3.1.6 Field Evaluation of the LeadCheck Test Kit 

A study was carried out by Ashley et al. (1998) that involved testing of XRF, ASV, and 

qualitative test kits at some 200 locations in an old school building. The paint substrates 

included plaster, wood, metal, and brick. The expected values were determined by removing a 

paint sample, grinding it, extracting the Pb in acid using ultrasonication, and measuring the Pb 

level using AAS. 
26

Only one brand of qualitative test kit was used, the LeadCheck swabs (HybriVet Systems, Inc.). 

In situ spot test kit analysis was conducted according to ASTM Standard E1753 (ASTM, 2004).

First, the surface was cleaned using a new individually wrapped wet wipe (Wash N Dry). A 

notch was then cut into the center of the paint film sample area down to the substrate so as to 

expose all paint layers. The chemical spot test then was conducted in the cut following the 

ASTM procedure and the manufacturer’s instructions, and the presence or absence of the 

characteristic color for Pb was noted. Also, the relative intensity of the pink color formed was 

noted. Swabs showing a negative response were checked after 24 h for any color formation. 

Any negative result was confirmed with the use of a positive control, wherein a test card that 

contained lead nitrate was tested using the same LeadCheck swab that gave a negative in situ 

reading on the paint film sample. 

The resulting response curves were very similar to those reported previously (as described in 

Section 3.1.4), with a relatively large number (about 30%, based on estimation from the plots in 

the publication) of positive responses below the action levels of 0.5% or 1 mg/cm2

. The test kit 

data showed 4.5% false negative readings for samples with Pb levels above the 0.5% action 

level. The test kit results also showed about 4% false positive readings for samples with Pb 

levels below the CPSC action level of 0.06% Pb. The number of false negative results and false 

positive results by substrates are shown in Table 14. 

Table 14. False Negative and False Positive Rates for Field Evaluation of 

LeadCheck Kit (Ashley et al., 1998) 

Substrate 

Number of 

Observations 

Number of Negative 

Results at >0.5% 

Number of Positive 

Results at <0.06% 

Plaster 44 1 0 

Metal 41 1 1 

Wood 40 0 1 

Brick 41 1 2 

All substrates 166 3 4 

The principle issue addressed in this work was the following. 

• False positive and negative results 

3.1.7 RTI Large Field Study 

RTI performed a large field study in the mid-1990s for EPA (Gutknecht et al., 1999). In this 

study, samples were analyzed using test kits, XRF, and ICP at 115 different primary test 

locations. These primary test locations were found in five buildings associated with a residential 

hospital and four buildings associated with an old school. Substrate materials encountered in 

these buildings included plaster, metal, concrete, fiberboard, and wood. At each primary test 

location, three measurements were made of the Pb in the paint with each of nine test kits: 

(1) Acc-U-Test, 

(2) EM Merck, 

(3) Frandon All-in-One (card), 

(4) Frandon All-in-One (solution), 

(5) Frandon Lead Alert (card), 

(6) Frandon Lead Alert (solution), 

(7) LeadCheck, 

(8) Lead Detective, and 

(9) Lead Zone. 
27

The tests were performed by a number of different staff. In addition, three different samples 

were taken for ICP-AES analysis at each of these 115 locations. The responses of the 

qualitative test kits were rated as follows: no apparent color change (N), weak color change (P-

), 

clearly positive response (P), and strong color formation (P+

). These four ratings were assigned 

numeric values of 0, 0.1, 1.0, and 1.2, respectively. The average of the three numbers for each 

location was compared to the average ICP-AES values. Because of the lack of resources, a full 

analysis of these results, including statistical analyses, never was completed. However, simple 

visual comparisons were made. Figures 1 and 2 show the results for the LeadCheck in mg/cm2 

(Figure 1) and percent Pb (Figure 2). There are a large number of positive responses below the 

1.0 mg/cm2

 level (in Figure 1) and the 0.5% level (in Figure 2). Figure 1 shows 1 of 81 results as 

false negatives and 35 of 81 results as false positives. Figure 2 shows 5 of 88 results as false 

negatives and 16 out of 88 results as false positives. The same trends were observed with the 

other rhodizonate-based kits and even more so with the sulfide-based Lead Detective kit. 

The principle issue addressed in this work was the following. 

• False positive and negative results 

3.1.8 NIST Laboratory Study 

A laboratory study was performed to determine the reliability of spot test kits using a large 

number of laboratory-prepared paint samples (Rossiter et al., 2000) For the study, four 

Figure 1. ICP results versus LeadCheck results (mg/cm2). 

Note: Responses presented as numeric average of three results from each site rated as 0 - no apparent 

color change, +0.1 - a weak color change, +1.0 - a clearly positive response, and +1.2 - a strong color 

formation. All positive results at concentrations less than 1 mg Pb/cm2

 represent false positive results 

relative to the proposed Federal performance standards. 
28

Figure 2. ICP results versus LeadCheck results (percent Pb). 

Note: Responses presented as numeric average of three results from each site rated as 0 - no apparent 

color change, +0.1 - a weak color change, +1.0 - a clearly positive response, and +1.2 - a strong color 

formation. All positive results at concentrations less than 0.5% Pb represent false positive results relative 

to the proposed Federal performance standards. 

rhodizonate-based kits ([1] Lead Zone, [2] LeadCheck, [3] Lead Alert Home Kit, and [4] Lead 

Alert Professional Kit) and four sulfide-based kits ([1] Acc-U-Test, [2] Heads Up, [3] Lead 

Detective, and [4] Sulfide Massachusetts [MA]) were used to investigate the effects of Pb level, 

Pb pigment type, operator, substrate, overlayer paint type, and overlayer paint thickness. 

Three substrates were used for the test panels: (1) wood, (2) plaster, and (3) steel. For the 

purposes of experimental design, each substrate was categorized as either reactive (i.e.,

causing interference) or nonreactive to the test kit reagent. Wood was considered to be

nonreactive for both rhodizonate and sulfide test kits. Plaster substrates may interfere with the 

development of the characteristic color for rhodizonate test kits and result in false negative 

responses (ASTM, 2004), so plaster is considered to be reactive for rhodizonate test kits. 

Metals present in steel substrates may react with sulfide test kits resulting in false positives 

(ASTM, 2004), so steel substrates were considered to be reactive for sulfide-based test kits. 

The experiments were designed so that rhodizonate reagents were applied to specimens having 

plaster and wood substrates, and sulfide reagents were applied to specimens with steel and 

wood substrates. 

The leaded-paint films were prepared by spreading a Pb-spiked commercial paint on a smooth, 

nonporous surface, using a drawdown blade to provide films having uniform thickness. The 

leaded-paint film/substrate assemblies were overcoated with a thin or thick layer of latex or oilbased household paint to assess the impact of overlayer paint type and thickness. 
29

The Pb levels for each test panel were determined quantitatively by a commercial laboratory 

accredited in the National Lead Laboratory Accreditation Program (NLLAP) using ICP 

spectrometry according to NLLAP protocols. Operators conducted the spot tests according to 

protocols written for each of the eight spot test kits. For each protocol, the basic steps for the 

spot test kit were taken from the manufacturer's instructions. 

Several of the test kits were tested in different ways. For the LeadCheck test kit, Type 1 refers 

to the first swab examined within 2 min, Type 2 refers to the first swab reexamined after a 

period of time, and Type 3 refers to a second swab checked for up to 18 h. For the Lead 

Detective and Sulfide MA test kits, Type 1 refers to testing a notch, and Type 2 refers to testing 

a paint chip surface. 

Table 15 summarizes the false negatives and false positives at the 1.0 mg/cm2

 Pb level for 

paints spiked with white lead and lead chromate on wood substrate. Regarding false negatives, 

the results varied considerably depending on the Pb pigment type. For white lead, the percent of 

false negatives was generally low (<4%), except for Acc-U-Test and Lead Alert Home Kit. In five 

Table 15. False Negatives and False Positives at Pb Levels of Less Than and 

Greater Than 1.0 mg/cm2

False 

Negatives 

False 

Positives 

Pb 

Pigment 

Type Kit 

Total No. of 

Observations No. % 

Total No. of 

Observations No. % 

Acc-U-Test 40 5 13 200 81 41 

Heads Up 30 0 0 114 91 80 

Lead Zone 45 0 0 195 132 68 

LeadCheck – Type 1 45 1 2 195 124 64 

LeadCheck – Type 2 45 1 2 195 124 64 

LeadCheck – Type 3 45 1 2 195 125 64 

Lead Alert Home Kit 45 12 27 195 87 45 

Lead Alert Prof. Kit 45 0 0 195 88 45 

Lead Detective Type 1 40 1 3 200 97 49 

Lead Detective – Type 2 40 0 0 200 126 63 

MS Sulfide – Type 1 24 1 4 120 41 34 

White 

lead 

MS Sulfide – Type 2 24 0 0 120 67 56 

Acc-U-Test 115 57 50 125 34 27 

Heads Up 69 29 42 75 41 55 

Lead Zone 125 75 60 115 18 16 

LeadCheck – Type 1 125 33 26 115 34 30 

LeadCheck – Type 2 125 25 20 115 36 31 

LeadCheck – Type 3 125 1 1 115 57 50 

Lead Alert Home Kit 125 100 80 115 12 10 

Lead Alert Prof. Kit 125 97 78 115 9 8 

Lead Detective – Type 1 115 6 5 125 64 51 

Lead Detective – Type 2 115 2 2 125 70 56 

MS Sulfide Type – 1 69 3 4 75 31 41 

Lead 

chromate 

MS Sulfide Type – 2 69 1 1 75 39 52 
30

cases (Heads Up, Lead Zone, Lead Alert Professional Kit, Lead Detective – Type 2, and 

MA Sulfide – Type 2), no false negatives were observed. In contrast, for lead chromate, only 

LeadCheck – Type 3, Lead Detective – Types 1 and 2, and MA Sulfide – Types 1 and 2 had low 

percentages (<5%) of false negatives. Regarding false positives, the vast majority (about 85%) 

of the spot tests for both Pb pigment types showed percentages greater than 30%. That is, most 

spot test kits gave positive responses when the true value was less than 1.0 mg/cm2

. 

The probabilities of positive response as a function of Pb concentration and other covariates 

were estimated using logistic regression models. Plots for the LeadCheck – Type 1 and MA 

Sulfide – Type 1 are shown in Figures 3 and 4. The filled circles represent the proportions of 

Figure 3. Probability of a positive response versus Pb level for LeadCheck – Type 1 (here 

presented as STK4a) on nonreactive (wood) and reactive (plaster) substrates (reproduced from 

Rossiter et al., 2000). 
31

Figure 4. Probability of a positive response versus Pb level for MA Sulfide – Type 1 (here 

presented as STK8a) on nonreactive (wood) and reactive (steel) substrates (reproduced from 

Rossiter et al., 2000). 

positive responses at a given Pb level, and the error bars are the associated 95% binomial 

confidence intervals. The two horizontal dashed lines represent the 0.5 and 0.95 probabilities of 

a positive response. Circles are the 0.95 probability point for each operator; they are repeated 

above the horizontal axis for clarity. 

A separate model was fit for each kit, as well as for white lead and for lead chromate. The 

substrate effect was treated as a fixed effect in the regression model (except for Heads Up), and 

the operator effect was modeled as random. The results of these calculations are presented in 

Table 16. 
32

Table 16. Pb Level Corresponding to a 95% Probability of a 

Positive Response for an “Average” Operator 

Pb Level (mg/cm2) 

White Lead Lead Chromate 

Spot Test Kit 

Reactive 

Substrate 

Nonreactive 

Substrate 

Reactive 

Substrate 

Nonreactive 

Substrate 

Acc-U-Test 1.9 2.3 6.2 8.4 

Heads Up ― 0.4 ― 89.8 

Lead Zone 0.1 0.1 8.1 7.7 

LeadCheck – Type 1 0.5 0.4 4.1 3.5 

LeadCheck – Type 2 0.5 0.4 3.6 2.8 

LeadCheck – Type 3 0.5 0.4 0.6 0.7 

Lead Alert Home Kit 3.9 2.1 24.6 21.6 

Lead Alert Prof. Kit 0.9 0.7 14.3 11.6 

Lead Detective – Type 1 1.1 1.2 1.1 1.5 

Lead Detective – Type 2 0.3 0.4 0.8 1.0 

MS Sulfide – Type 1 1.9 1.6 1.3 1.5 

MS Sulfide – Type 2 0.5 0.5 0.8 0.9 

The issues addressed in this work included the following. 

• False positive and negative results 

• Interferences 

• Need for training 

3.1.9 Testing Using the HUD Archive 

In a study led by QuanTech, four rhodizonate-based test kits and one sulfide-based test kit were 

applied to a set of the real-world painted building components from the HUD archive materials 

that are used for evaluating portable XRF instruments (Cox et al., 2001). The objectives were to 

(1) determine the extent to which manufactured paint films previously tested by NIST (Rossiter 

et al., 2000) are representative of field paint samples with respect to the evaluation of test kit 

performance, and (2) investigate the development of Performance Characteristic Sheets 

fromthe data collected at NIST using the manufactured paint samples. The real-world samples 

and manufactured samples had similar Pb levels. The same protocols were used for testing 

both the NIST and archive samples. The substrates were divided into reactive and nonreactive 

substrates based on the potential for chemical interaction between test kit reagents and the 

substrate. Wood was the nonreactive substrate for both types of kits. The reactive substrate 

was plaster for the rhodizonate kits and metal for the sulfide kit. 

Testing of the archive samples was carried out by two of the five trained staff involved in the 

NIST testing. The results achieved with the white lead-based paint are shown in Table 17. 

The number of false negatives at or above 1.0 mg/cm2 is small, averaging about 6%; as noted, 

three out of five of the kits gave no false negatives. The number of false positives below 

1.0 mg/cm2

 is large, averaging close to 50%. Even at close to 0 mg/cm2, false positives occur. 
33

Table 17. Results of HUD Archive Testing on White-Lead-Based Paint 

Response 

Low Pb Level 

> 0.01 mg/cm2

Low Pb Level 

< 0.01 mg/cm2

Pb Level 

≥ 1.0 mg/cm2

Pb Level 

< 1.0 mg/cm2

False negatives 1.7% to 35.6% 

av 17% ± 14% 

― 0% to 26.7% 

av 6% ±12%a

―

False positives ― 0% to 11.7% 

av 5.3% ± 4.3% 

― 44.6% to 67.7% 

av 60% ± 11% a

Three out of five kits gave 0.0% (no false negatives). 

As noted earlier, a test kit that meets the proposed Federal performance standards must have a 

high probability of obtaining a positive result when the Pb level is at or above 1.0 mg/cm2 and a 

high probability of obtaining a negative result when the Pb level is below 1.0 mg/cm2

. As stated 

by the authors, “None of the test kits in this research have this capability as shown in the 

response curves.” 

As to the goals of this study, the test kit evaluation system using manufactured samples was 

found to be acceptable for predicting performance of test kits on nonreactive substrates; that is, 

the manufactured samples appeared to be representative of the archive samples in that the 

response curves for the archive samples fell between the response curves for white lead-based 

and lead chromate-based paints (which were taken as most soluble and least soluble common 

Pb pigments, respectively). For reactive substrates, the response curves generated with the 

archive samples were generally outside of the two curves for the white lead-based and lead 

chromate-based paints, indicating significant differences between the archive and manufactured 

samples.

The principle issues addressed in this work were the following. 

• False positive and negative results 

• Need for training 

3.1.10 Reports from Jim Weydt of Acc-U-Test Test Kit 

Jim Weydt of Acc-U-Test, Weymouth, MA, provided a summary of a number of reports of work 

with the sulfide-based kits (Weydt, 2006). In one report (Vind et al., 1978), tests were made of 

the sensitivity of the sodium sulfide reagents to various Pb compounds. In that work, Vind and 

colleagues report that the minimum concentration of Pb that could be detected in light-colored 

paints was approximately 0.5%, although the basis of the relationship between the test 

compounds and paint concentrations is not clear. In a different report in Consumer Reports in 

July 1995, the sensitivity of the sulfide-based Acc-U-Test is given as 0.05%, which is more 

consistent with the sensitivities reported by others, such as Rossiter et al. (2000). In other work, 

Weydt (1993) reported that 16 metal pigments considered to be potential interferents with the 

sulfide-based test kit were reacted with 6% to 8% sodium sulfide test solution. These metal 

pigments were antimony, bismuth, cadmium, chromium, cobalt, copper, iron, manganese, 

magnesium, mercury, molybdenum, nickel, silver, tin, titanium, and zinc. All but one of these 

metals are used as fire retardants, biocides, fungicides, and drying agents in paints for 

industrial, commercial, and marine use. The possibility of these materials causing false positive 

test results in paints intended for residential use is very unlikely. If present, the levels are 

expected to be so low as to not interfere with an in situ sulfide-based test. 

The principle issues addressed in this work were the following. 

• False positive and negative results 

• Interferences 
34

3.1.11 Test Kit Based on DNAzyme Nanoparticles 

Lu (2005) describes a new Pb test kit based on the reaction of Pb with a component of an 

enzyme. Studies have shown that DNA has enzymatic properties. A component of the DNA is 

termed a DNAzyme, which consists of a substrate strand and an enzyme strand. The DNAzyme 

is highly selective towards Pb(II) as a cofactor over other metal ions to carry out hydrolytic 

cleavage of the substrate strand. In the presence of Pb(II) ion, the enzyme cleaves its substrate 

into two pieces. The strand is extended on both ends, with the extended fragment 

complementary to DNA attached to gold nanoparticles. As a result, gold nanoparticles can be 

assembled by the DNAzyme to form blue aggregates. In the presence of Pb, the substrate is 

cleaved and the assembly of nanoparticles is inhibited, which results in a red color. Then, the 

ratio of spectrophotometric absorptions at 522 nm and 700 nm (which correspond to blue and 

red) can be used to determine Pb(II) ion concentration. 

Synthetic samples with varying concentrations and latex overlays were prepared for the study. 

Results reported are shown in Figure 5. The change from essentially all negative responses to 

essentially all positive responses occurs over the range of about 1 mg/cm2

 to about 2 mg/cm2. 

This compares to a range of about 0 mg/cm2

 to 0.5 mg/cm2 for LeadCheck (see Figure 3) and a 

range of about 0 mg/cm2

 to 1.5 mg/cm2 for MA Sulfide (see Figure 4). 

Figure 5. Response of DNAzyme-based test kit using (A) benchtop and (B) portable colorimeters; 

(C) ideal sensor defined by Rossiter et al. (2000) (reproduced from Lu, 2005). 

Additionally, the tests of the method were performed with paint samples made in the laboratory 

by mixing commercially available white latex or white oil-based paints with Pb (II) carbonate, 

basic powder. 10% acetic acid and soaking and ultrasonication for about 40 min yielded 

quantitative recovery with diced paint samples. 

The principle issue addressed in this work was the following. 

• False positive and negative results 

3.1.12 Immunoassay-Based Test Kits 

Pb test kits may be based on the use of an immunoassay. This is a biochemical test that 

measures the level of a substance using the reaction of an antibody or antibodies to its antigen 

(in this case, Pb). The assay takes advantage of the specific binding of the antibody to its 

antigen. Monoclonal antibodies often are used, as they usually bind to only one site of a 

particular molecule and, therefore, provide a more specific and accurate test. The antibodies 

picked must have a high affinity for the antigen (if there is antigen available, a very high 
35

proportion of it must bind to the antibody). In a competitive immunoassay, the antigen in the 

unknown sample competes with labeled antigen (e.g., Pb ion bound in a fluorescent complex) to 

bind with the antibodies. The amount of antigen that transfers from the labeled state to being 

bound to the antibody site is then measured by a change in the label’s color, fluorescence, etc. 

The PurTest Immunoassay Lead test kit is used for Pb in water (www.silverlakeresearch.com). 

In less than 10 min, the test can be used to detect Pb in water at or below the EPA action level 

of 15 ppb. 

The principle issue addressed in this work was the following. 

• False positive and negative results 

3.1.13 Summary for Qualitative Test Kits 

In summary, a number of qualitative test kits have been developed and studied. The majority of 

these are based on the rhodizonate or sulfide reactions with Pb. The kits generally demonstrate 

a level of false negatives that meets the proposed Federal performance standard of less than 

10%, along with a high level of false positives, as high as about 70%. The high level of 

sensitivity found with these kits seems appropriate if the manufacturer is concerned that the 

users have a tool that is conservative and reveals very low levels of Pb because there is no way 

to determine how much of the actual Pb present will be extracted to react with the kit reagents. 

3.2 Semi-quantitative and Quantitative Test Kits 

3.2.1 Semi-quantitative Test Kits 

Semi-quantitative test kits are those that give an approximate value for the Pb level. They 

typically work by visually comparing the intensity of the color formed with some standard chart 

of colors or through a color comparator. To get some estimate of the concentration, the sample 

must be removed from the substrate and homogenized to some degree and subjected to 

extraction to get a total sample value. One such kit is the Merck EM Quant, which uses 

rhodizonic acid in an acidic solution to form a red complex with the Pb ion. The test procedure is 

as follows. 

• Add three drops of reagent (acetic acid) to the sample solution and swirl cautiously. 

• Immerse the test strip in the solution for 1 s so that the reaction zone is thoroughly moistened. 

Remove excess liquid by stroking the edge of the strip against the rim of the vessel. 

• Wait 2 min and compare the reaction zone with the color scale on the package. 

The scale on the package is graduated in different concentrations: 0, 20, 40, 100, 200, and 

500 mg Pb2+/L (ppm). The pH of the solution being tested should be between 2 and 5. This is 

normally the case once the reagents have been added. If the quantity of reagent specified in the 

directions is not sufficient to adjust the solution to this pH (which can be checked with a pH 

indicator strip), strongly acidic solutions must be buffered prior to the determination with 1 M 

sodium hydroxide solution, and alkaline solutions with 1 M nitric acid. 

In the study by Luk et al. (1993b) the Merck EM Quant was used to test for Pb on the surface of 

laboratory-prepared paints. Method A for this kit calls for wetting the surface and then contacting 

the surface with the test strip after the reaction has gone on for 1 min; Method B calls for wetting 

the strip and then contacting the strip with the paint surface. For paints with 0.1 and 0.6 mg/cm2

, 

Method A values for three samples of each paint were all 0 ppm. At 1.9 mg/cm2

, the three 

readings were all 10 ppm. For paint at 2.6 mg/cm2

, the three readings were 40, 100, and 

200 ppm. Again, it must be noted that this semi-quantitative mode is intended for solubilized Pb 

(i.e., Pb ion). No study has been identified that evaluated the Merck EM Quant with solubilized 

paint. 
36

Other test kits intended for the measurement of Pb in water using visual comparison are 

available and could be used for testing solubilized Pb, including PurTest Lead and Lead 

Inspector Lead Test Kit. 

3.2.2 Quantitative Test Kits―Laboratory Study 

The quantitative test kits usually involve an instrumental measurement of the product of reaction 

with Pb. This may be measurement of the colored product of Pb with rhodizonate or some other 

reagent or measurement of some other unique property of Pb. A number of ASTM methods for 

quantitative measurement of Pb in paint that are or could be applied in the field have been 

developed and are available, including 

• E1729-05 Standard Practice for Field Collection of Dried Paint Samples for Subsequent Lead 

Determination; 

• E1979-04 Standard Practice for Ultrasonic Extraction of Paint, Dust, Soil, and Air Samples for 

Subsequent Determination of Lead; 

• E2051-01 Standard Practice for the Determination of Lead in Paint, Settled Dust, Soil, and Air 

Particulate by Field-Portable Electroanalysis; and 

• D3559-96 Standard Test Methods for Lead in Water (using ASV). 

Three different quantitative kits have been studied by RTI. These are based on color intensity 

measured by reflectance, color intensity measured with a simple colorimeter, and 

electrochemical oxidation of Pb that has been concentrated on an electrode through a period of 

reduction or plating out of the sample extract (ASV). 

In a laboratory study (Williams et al., 1996), the EM Science Reflectoquant (based on 

reflectance) and the Pace Environs PaceScan 2000 (based on ASV) were evaluated with a 

series of paint reference materials that were either from the Environmental Lead Proficiency 

Analytical Testing (ELPAT) program or other paints that were ground to a powder and verified 

by multilaboratory analysis. Pb concentrations ranged from 222 μg/g to 118,700 μg/g. Materials 

were extracted according to the manufacturer's recommendations. Pace Environs, Inc., 

prescribed the RTI Ultrasonic/Acid Extraction Method (Luk et al., 1993a) to extract paint, dust, 

and soil samples for analysis by the PaceScan 2000. However, EM Science did not prescribe 

an extraction method for the Reflectoquant, so RTI modified its original ultrasonic/acid extraction 

method (Luk et al., 1993b) to address sensitivity requirements for the Reflectoquant. 

EM Science Reflectoquant. With this instrument, the Pb-containing samples (detection limit 

goals determine appropriate sample weight) were digested (or extracted) in a nitric acid solution 

and diluted to 50 mL, and 10-mL aliquots were removed. The aliquots were buffered into a pH 

range of 3 to 4 (previously determined to optimize the formation and stability of the lead 

rhodizonate complex [Luk et al., 1993b]). The test strips were removed from the vial and 

immersed in the buffered solutions (10 mL of extract plus volume of buffer) for approximately 

2 s, then placed in the optics of the reflectometer. The measurement requires a total of 2 min 

(immersion and optical measurement). At the end of the 2-min interval, the Pb concentration in 

the solution (μg Pb/mL) is displayed on the Reflectometer. 

The Lead Test instructions enclosed with each Reflectoquant kit of test strips, bar code, and 

Lead Test reagent indicated that the instrument measured Pb in the range of 20 to 200 mg Pb/L 

(equivalent to 20 to 200 μg Pb/mL or 20 to 200 ppm). The instrumental detection range of 20 to 

200 μg Pb/mL correlates to a method detection range of 10,000 to 100,000 μg Pb/g paint (for a 

100-mg sample extracted using the RTI ultrasonic/acid extraction method [Luk et al., 1993b]).

The maximum recovery of Pb with the test samples (151%) was observed for ELPAT Sample 

5P1 extracted and buffered with NH4OH/NH4OAc. The measured means for three of the six 

samples were statistically different from the expected mean concentration. When ELPAT 
37

performance criteria were applied to the ELPAT samples analyzed, three out of five measured 

mean concentrations were found to be in the ELPAT acceptance range (mean ± 3σ). Results 

are summarized in Table 18. 

Table 18. Summary of Results for the Analysis of RTI Core Paint Materials Using the 

EM Science Reflectoquant 

Buffer System 

Analytical Result NaOH/NaOAc NH4OH/NH4OAc 

Sample weight extracted 500 mg 500 mg 

Method detection limit (MDL)

(calculated, n=7) 

7.1 μg Pb/mL (900 μg Pb/g) 10.2 μg Pb/mL (1300 μg Pb/g) 

Method quantitation limit 

(MQL) (calculated, n=7) 

24 μg Pb/mL (3000 μg Pb/g) 34.0 μg Pb/mL (4320 μg Pb/g) 

Range of recoveries 

(all samples) 

63%a to 132%b (n=18) 80.1% to 151%b (n=17) 

Mean recovery 98.5 ± 23.9% (n=18) 114 + 22.0% (n=17) 

Range of reproducibility 1.3 to 16% (1σ, n=6) 1.0% to 22% (1σ, n=6) 

Pooled relative standard 

deviations (RSDs) 

8.2% (n=6) 11.8% (n=6) 

Equivalency of measured mean 

and expected concentration at 

the 95% confidence level 

Measured means for three out 

of six samples were statistically 

different from the expected 

concentration at the 95% 

confidence level. 

Measured means for three out of 

six samples were statistically 

different from the expected 

concentration at the 95% 

confidence level. 

Comparison of measured mean 

with ELPAT performance range 

(ELPAT samples only) 

Three out of five samplesc

 were 

acceptable. 

Three out of five samplesc were 

acceptable. 

pH criteria pH=4, particularly for samples 

with low levels of Pb 

Three to four 

Cost of analyses Cost of instrument: $495.00 

(in 1995 dollars) 

Materials: $1.11/test strip + 

ultrasonicator + reagents a

At low end of linear operating range 

b

At high end of linear operating range 

c

ELPAT samples only 

The Pb concentration of each extract buffered with the NaOH/NaOAc system was verified by 

ICP analysis to evaluate the extraction efficiency of the modification of the RTI ultrasonic/acid 

extraction method (Luk et al., 1993b). A linear regression of the measured concentration versus 

the RTI ICP concentration was generated to eliminate variables from the extraction method and 

to allow only the measurement methods to be compared. The linear regression curve, provided 

in Figure 6, shows a correlation coefficient of 0.986 and a regression y = 1.16x – 3510. The 

slope of the curve suggests the importance of verifying calibration before samples are analyzed 

with this instrument. 

Environs PaceScan 2000. With this instrument, 5-mL aliquots of the extract were taken from 

the extraction tube, the extracts were buffered with the packaged PacePrep tablet (used to 

adjust pH and add an electrolyte for stabilizing the ionic strength of the extract), and analyzed 
38

Figure 6. Plot of the Pb concentration (μg Pb/g) measured by the EM Science Reflectoquant 

versus ICP-AES for RTI paint materials. 

using the anodic stripping analysis instrument. A new, separate electrode is used for each 

analysis. 

The PaceScan offers two ranges, a low range (LR), and a high range (HR), for the 

measurement of Pb in paint. 

LR: 0.025 to 1.5 mg Pb/sample (50 mL extract) 

0.050 to 3.0 mg Pb/cm2

HR: 0.1 to 5.0 mg Pb/sample (50 mL extract) 

0.2 to 10.0 mg/cm2

Measured mean concentrations of the ELPAT samples were compared to the ELPAT range of 

acceptable performance, mean ± 3σ (Esche et al., 1995). An MDL (254 μg Pb/g paint) and an 

MQL (848 μg Pb/g paint) were calculated from the standard deviation of seven analyses of the 

100-mg paint extract with the lowest Pb concentration (MEM Low Paint, measured 

concentration 1420 μg Pb/g). The MDL is consistent with the instrument’s low-range operating 

specification, where 0.025 mg/sample equates to 250 μg Pb/g paint for a 0.100-g aliquot 

extracted using the RTI ultrasonic/acid extraction method (Luk et al., 1993b). Of the 20 samples 

measured, only three showed relative recoveries less than 90%. The high recovery of Pb 

(131%) for ELPAT Sample 5P2 (expected concentration 222 μg Pb/g paint) suggests a positive 

bias at lower Pb levels. Results for the analysis of paint are summarized in Table 19. 

To compare analytical performance only, a linear regression of the measured mean 

concentration versus the RTI ICP concentration was generated; the regression plot is provided 

as Figure 7. The regression equation, y = 0.900x – 103, r2

 = 0.9996, suggests a good 

correlation of PaceScan data to ICP analysis. 
39

Table 19. Summarized Results for the Measurement of RTI Core Paint Materials 

Using the PaceScan 2000 

Measurement Range 

Performance Parameter Low Range 

(0.025 to 1.5 mg Pb/sample) 

High Range 

(0.1 to 5.0 mg Pb/sample) 

Sample weight extracted 100 mg 100 mg 

MDL 0.0254 mg Pb/sample 

254 μg Pb/g 

Not determined 

MQL 0.0848 mg Pb/sample 

848 μg Pb/g 

Not determined 

Mean recovery 88.1± 6.4% (n=18) 89.0% ± 17.1% (n=21) 

Range of individual 

recoveries 

76.1%a to 99.9% 50%b to 110% 

Range of RSDs 3.2% to 10.8% (n=6) 0% to 10% (n=7) 

Pooled RSD 6.1% (n=6) 5.6% (n=7) 

Equivalency of measured 

mean and expected mean 

concentration at 95% 

confidence level 

Measured means for three out of 

six samples were statistically 

different from the expected mean 

concentration at the 95% 

confidence level. 

Measured mean for one out of 

seven samples was statistically 

different from the expected mean 

concentration at the 95% 

confidence level; 2 samples were 

indeterminate (divided by 0) at the 

95% confidence level. 

Comparison of mean result 

to ELPAT acceptable 

performance range 

(mean ± 3σ) 

The measured means for six out of 

six samples are acceptable 

according to the ELPAT 

Performance Range. 

Not determined 

a

Measurement is 1.468 mg Pb/sample, near the upper end of the low range. b

Measurement is 0.1 mg Pb/sample, at the low end of the high range. 

3.2.3 Quantitative Test Kits―Field Studies 

The pilot field study described in Section 3.1.5 included evaluation of a colorimetric test kit 

(Gutknecht et al., 1997). The procedure used in this study was developed by Luk et al. (1993a). 

The method involves weighing 0.1 to 0.25 of paint, soil, or dust into a 50-mL plastic centrifuge 

tube. Then 15 mL of 25% (v/v) nitric acid is added and the sample in the tube is placed in an 

ultrasonic bath for 30 min. Following dilution to a fixed volume, thorough mixing, and separation 

of solids by centrifugation, filtration, or decanting, an aliquot of the resulting extract is pHadjusted and further diluted in two successive steps. The sample solution is then analyzed for 

Pb using the Hach colorimetric kit for Pb (Hach). First a Hach reagent is added. The resulting 

solution is then passed through an ion exchange column provided in the Hach kit to collect and 

concentrate the Pb. The Pb is flushed from the column with an eluent provided in the kit. 

A complexing agent then is added to the eluted Pb solution, and the resulting colored complex 

is measured using a small portable colorimeter, provided in the test kit. Results from the 

laboratory evaluation of the method generally showed a recovery of greater than 90% with 

standard samples and an RSD of less than 10%. 

Samples for this field evaluation of the Hach method were taken from the area used for XRF 

testing and also the qualitative test kit area. The accuracy of the colorimetric test kit was 

estimated by comparison of the MW/ICP values for areas with the test kit results for these 
40

Figure 7. Plot of the Pb concentration (μg Pb/g) measured by the PaceScan 2000 versus ICP-AES 

for RTI paint materials. 

areas. The average mass recoveries (100 plus percent difference) for the wood and fiberboard 

components were 97% ± 17% and 90% ± 14%, respectively. These recovery values of ≥90% 

are consistent with performance reported by Luk et al. (1993b). Comparison of MW/ICP values 

determined from the test kit locations is more tenuous because of the variability of Pb in the 

paint from location to location. Nevertheless, average mass recoveries (100 plus percent 

difference) for the wood and fiberboard components were 99% ± 15% and 92% ± 10%, 

respectively. However, the range of recoveries is relatively large, as presented in Table 20. 

Table 20. Range of Recovery Values for the Colorimetric Test Kit Test 

Sample Mass Concentration Area Concentration 

Paint on wood, area B 71% to 118% 71% to 119% 

Paint on wood, test kit locations 78% to 127% 67% to 134% 

Paint on fiberboard, area B 65% to 107% 66% to 103% 

Paint on fiberboard, test kit locations 77% to 109% 68% to 121% 

The range of concentrations was very limited, as reported above. This, in conjunction with large 

variability in the results, made any regression analysis meaningless. 

The precision was estimated from the replicate analyses in the test kit locations, because it is 

reasonable to assume that variation in this 2 x 12-in limited area would be minimal. The pooled 

standard deviations for the analyses of three different samples in each of the different test kit 
41

locations are presented in Table 21, along with these same values for the MW/ICP analyses. As 

noted, the pooled RSD for the quantitative field kits is about 15% for mass concentration. 

Table 21. Pooled Standard Deviation for Triplicate Analyses Performed within 

Each Test Kit Location 

Analysis Performed 

Mass Concentration, % 

(pooled RSD) 

Area Concentration, mg/cm2 

(pooled RSD) 

MW/ICP, mean of all sample areas 

(A-D3), wood 

0.63 (15) 0.47 (22) 

Colorimetric field kit, wood, 

test kit locations 

0.58 (14) 0.42 (19) 

MW/ICP, mean of all sample areas 

(A-D3), fiberboard 

0.22 (14) 0.29 (19) 

Colorimetric field kit, fiberboard, 

test kit locations 

0.21 (14) 0.18 (15) 

The study described in Section 3.1.5 included evaluation of three quantitative test kits, the 

Reflectoquant; the PaceScan 2000; and a third kit, the Hach Colorimeter. It should be noted that 

other field colorimeters are available for measurement of Pb in water, such as the OrbecoHellige colorimeter (Orbeco Analytical Systems, Farmingdale, NY), which claims a range of 1 to 

150 μg Pb/L. 

The Hach DR 100 analog colorimeter is precalibrated over the range of 0 to150 μg/L. A threepoint calibration is recommended for this instrument. In a standard operating procedure (SOP) 

developed by Luk et al. (1993a), the paint samples are to be digested/extracted in 25% nitric 

acid in a small, field portable ultrasonic bath. This SOP gives a measure of the bias expected 

with well-characterized homogenized real-world paint and NIST SRMs. Values reported are 

shown in Table 22. 

Table 22. Accuracy and Precision Values for Real-World and NIST SRM Samples 

Sample 

Referee Value, % Pb 

(n) 

Mean Kit Value % Pb 

(n) 

Accuracy as 

% Bias % RSD 

Paint 1 0.162 ± 0.004 (3) 0.181 ± 0.014 (15) 11.7 7.7 

Paint 2 0.646 ± 0.023 (3) 0.624 ± 0.023 (15) –3.4 3.7 

Paint 3 3.60 ± 0.03 (3) 3.25 ± 0.20 (15) –9.7 6.2 

SRM 1579 11.87 ± 0.04 10.8 ± 0.8 (25) –9.0 7.4 

The large field study described in Section 3.1.7 involved taking samples from the same location 

for ICP analysis, spot tests, and quantitative test kits. As noted previously, some 115 locations 

in an old hospital and an old school that included plaster, wood, metal, and concrete were 

tested. The data for the Reflectoquant, PaceScan, and Hach kits were not fully statistically 

analyzed because of the lack of resources. Mathematical modeling based on paired values 

should be performed for proper comparison of the kits with the ICP values. Currently, only 

simple regression analysis has been performed. These results are presented in Table 23. 

One can see that the agreement of the ICP values with the test kits values is highly variable. 

One source of the variability is the source of the samples; the slope for the PaceScan for wood 

is 0.63 (see Table 23) for all samples tested, but 1.00 if one looks only at samples from the old 

hospital and excludes samples from the old school. 
42

Table 23. Results of Regression Analysis Comparing ICP Results with 

Quantitative Test Kits 

Reflectoquant 

Substrate Reflectometer PaceScan ASV Hach Colorimetric 

(n) Slope R2 Slope R2 Slope R2 

Wood (59) 2.15 ± 0.26 0.56 0.63 ± 0.065 0.62 2.16 ± 0.25 0.56 

Plaster (19) 0.58 ± 0.43 0.096 1.25 ± 0.11 0.89 0.41 ± 0.40 0.057 

Concrete (10) 0.85 ± 0.39 0.37 0.77 ± 0.30 0.46 0.85 ± 0.39 0.38 

Metal (19) 1.01 ± 0.12 0.80 0.62 ± 0.12 0.63 1.12 ± 0.10 0.87 

Ashley et al. (1998) also included the PaceScan ASV system in a field study. Expected values 

were determined by AAS analysis of samples returned to the laboratory. The results were 

reasonably well correlated, with R2

 = 0.81; the slope was 0.868. This study explained outliers as 

possibly resulting from the samples not being grinded adequately in the field. Ashley and 

co-workers also performed regression analysis; their results are presented in Table 24. 

Table 24. Results of Regression Analysis Comparing AAS Results with 

PaceScan Kit Results 

Substrate Type (n) Slope Intercept (%) R2

Wood (39) 0.894 0.055 0.731 

Plaster (44) 1.28 –0.018 0.821 

Brick (40) 1.09 –0.027 0.965 

Metal (42) 0.762 0.057 0.872 

All (165) 0.868 0.072 0.814 

The slopes and correlation coefficients are similar for the two studies for the PaceScan kit. 

Differences could arise from numerous sources, including the nature of the paints collected, the 

age of the paints, and the difference in extent of homogenizing and extracting the paints. The 

differences also could arise from the variability of the paint across the sampling location. It is 

well known that real-world paint samples, even from the same wall or door frame, show 

considerable point-to-point variability in Pb concentration. This makes sense if one considers 

the mechanics of painting. At the start of application, the brush is full and the layer may be thick, 

but as the paint continues to flow from the brush onto the surface, the layer may become 

thinner. If one multiples this possibility over several coats of paint, one can see that there is a 

strong likelihood of great variability in the point-to-point Pb concentration. 

Finally Sussell and Ashley (Sussell and Ashley, 2002) performed onsite measurement of Pb in 

paint chip samples by ultrasonic extraction and ASV in the field during renovation and 

remodeling activities. Pb in sample extracts subsequently was determined by AAS in a fixed-site 

laboratory. The remaining sample extracts plus undissolved material were then subjected to hot 

plate digestion in concentrated nitric acid-30% hydrogen peroxide prior to AAS analysis for Pb. 

Pb measurements by AAS were compared to Pb determinations by hot plate digestion-AAS; 

these data were highly correlated and demonstrated not-significant bias, thereby showing that 

the ultrasonic extraction procedure is equivalent to the hot plate procedure. Field ASV data were 

compared to AAS and results from the fixed-site laboratory Pb measurements. A significant 

negative bias associated with the ASV measurement was observed and attributed to a matrix 

effect, such as a chemical interference (Rossiter et al., 2001). Additional leaching of Pb from the 
43

paint sample matrix after ultrasonic extraction in the field (i.e., during transport and storage) is 

another possible confounder that could result in the observed negative bias in onsite 

measurements. 

3.2.4 Immunoassay-Based Test Kits 

An area of ongoing development is the use of immunoassay for quantitative measurement of 

Pb. In one study, Pb concentrations were determined by a fluorescence polarization of 

immunoassay method that used polyclonal antibodies raised against the Pb (II) chelate of 

ethylenediaminetetraacetic acid (EDTA) (Johnson et al., 2002). The technique is based on 

competition for a fixed concentration of antibody binding sites between Pb-EDTA, formed by 

treating the sample with excess EDTA, and a fixed concentration of a fluorescent analogue of 

the Pb-EDTA complex. The limit of detection was approximately 1 ppb and cross reactivity with 

15 nontarget metals was below 0.5% in all cases. The authors claim the methods are simple 

and amenable to field testing, allowing “timely and cost effective characterization of suspected 

sources of Pb.” 

4.0 AVAILABILITY OF PERFORMANCE EVALUATION MATERIALS 

ASTM E 1828, “Standard Practice for Evaluating the Performance Characteristics of Qualitative 

Chemical Spot Test Kits for Lead in Paint” (ASTM, 2001b) sets forth requirements and provides 

guidance for the preparation of standard synthetic dry paint films. The ASTM standard 

addresses leaded paint components, substrate, overlayers, thickness, concentration ranges, 

and number of samples. These reference paint films are intended for method evaluation. The 

approach would be to prepare a large number of paint films that are made up of different types 

of Pb pigments, different concentrations of Pb, and different structure (thicknesses and 

overlayers) and to use the kits under consideration to test all these samples. A select subset of 

these materials could be used as quality control (QC) materials for the kits. 

Current test kit manufacturers do not use or recommend using performance evaluation 

materials. Among test kit manufacturers, the accepted practice is to include a QC card (loaded 

with a known amount of Pb) or, in the case of one supplier, an actual paint chip that will provide 

a positive kit response. Inclusion of QC samples with the kits would be very beneficial, both to 

assure the user that the kit is being used properly and that the kit has the expected sensitivity. 

The only current sources of performance evaluation materials for evaluating test kits are 

QuanTech and NIST. QuanTech provides leaded film standards with certified Pb levels from 

<0.06 thru 3.51 mg/cm2

 prepared using a single layer of old formulation white lead paint 

mounted on a nylon substrate support overlaid with 10 layers of nonleaded paint to produce a 

2.9 x 2.5-in rectangular coupon. NIST provides Pb paint films ranging in concentration from 

blank to a high level Pb of 5.59 mg/cm2

 (Table 25). The NIST SRM paint films are intended for 

XRF analysis and are coated with a laminate layer that would have to be removed for use with 

test kits. Recently (in 2006), Dr. Kim Rogers of EPA developed a protocol for the removal of the 

laminate from NIST SRM paint films and reported on testing the protocol with the 1.0 mg/cm2

standard (Harper, 2006). 

NIST also has available RM 8680, Pb in paint on fiberboard, available in a 10.2 x 15.2 x 1.3-cm 

section of painted fiberboard, whose concentration is individually value assigned from 1 to 2 

mg/cm2

. 

For those test kits involving extraction of the Pb in paint followed by colorimetric, reflectance, or 

electrochemical determination, numerous Pb-in-paint reference materials are available. NIST 

produces several powdered Pb-in-paint SRMs, and RTI has accumulated 55 rounds of ground 
44

Table 25. NIST SRMs for Leaded Paint Films 

SRM Description 

Pb Concentration 

(mg/cm2

) 

2570 Pb paint film, blank <0.001 

2571 Pb paint film, nominal 3.5 mg/cm2 3.58 

2572 Pb paint film, nominal 1.6 mg/cm2 1.527 

2573 Pb paint film, nominal 1.0 mg/cm2 1.040 

2574 Pb paint film, nominal 0.7 mg/cm2 0.714 

2575 Pb paint film, nominal 0.3 mg/cm2 0.307 

2576 Pb paint film, high level 5.59 

Pb-in-paint ELPAT materials. In coordination with this work assignment, RTI is preparing intact 

paint films using ELPAT materials for Pb, which, if successful, would more closely mimic real 

world conditions for test kit evaluation. 

In addition, there have been studies reported in the literature that involved both evaluating spot 

test kits and the preparation of paint standards. Two reports used manufactured test samples of 

leaded paint and paint films for test kit evaluations (Rossiter et al., 2000; Cox et al., 2001). Cox 

and co-workers describe in detail the steps involved in the preparation of the manufactured 

performance evaluation samples. Lu (2005) describes a method for extracting Pb from paint and 

quantifying the amount of Pb present using a colorimetric Pb biosensor. For this study, Pb paint 

samples of different concentrations were prepared, with the preparation described. 

5.0 STANDARD PROCEDURES FOR EVALUATION OF TEST KITS 

An examination of the literature has identified several standard methods for evaluating test kits. 

One is ASTM Method E 1828-01, “Standard Practice for Evaluating the Performance 

Characteristics of Qualitative Chemical Spot Test Kits for Lead in Paint.” (ASTM, 2001b). The 

steps of the standard (described just below) are straightforward. 

• Collect paint samples or reference materials, or prepare synthetic standard paint films. 

• Test paint samples with the test kit according to ASTM Practice E 1753-04, “Standard 

Practice for Use of Qualitative Chemical Spot Test Kits for Detection of Lead in Dry Paint 

Films” (ASTM, 2004). 

• Prepare and analyze tested paint samples for quantitative Pb content using ASTM standards. 

• Compare the quantitative Pb content data from chemical analysis to the qualitative Pb spot 

test kit results. 

• Determine the performance parameters of a particular spot test for a particular paint matrix by 

statistically modeling the comparative data. 

Section 7.3 of the standard states that “hundreds of samples spanning the Pb concentration 

range of interest must be obtained for each combination of spot test kit and sample matrix that 

is to be tested.” 

Although modeling the qualitative spot test kit data is very complex, it enables the determination 

of the level of confidence of obtaining a positive or negative response at a given concentration. 

Another method for evaluation is E 1775, “Standard Guide for Evaluating Performance of 

On-Site Extraction and Field-Portable Electrochemical or Spectrophotometric Analysis for Lead” 

(ASTM, 2001a). This method 
45

• provides guidelines for determining the performance of field-portable quantitative Pb analysis 

instruments; 

• applies to field-portable electroanalytical and spectrophotometric (including reflectance and 

colorimetric) analyzers; and 

• addresses sample matrices of concern including paint, dust, soil, and airborne particulate. 

Another study was performed as a test of manufactured paints for test kit evaluation, although it 

is not a standard method. In this study directed by QuanTech, four rhodizonate-based test kits 

and one sulfide-based test kit were applied to a set of the real-world painted building 

components that are included in the HUD archive materials used for evaluating portable XRF 

instruments (Cox et al., 2001). The objectives were to (1) determine the extent to which 

manufactured paint films previously tested by NIST (Rossiter et al., 2000) are representative of 

field paint samples with respect to the evaluation of test kit performance, and (2) investigate the 

development of Performance Characteristic Sheets from the data collected at NIST using the 

manufactured paint samples. The real-world samples and manufactured samples had similar Pb 

levels. The same protocols were used for testing both the NIST and archive samples. The 

substrates were divided into reactive and nonreactive substrates based on the potential for 

chemical interaction between test kit reagents and the substrate. Wood was the nonreactive 

substrate for both types of kits. The reactive substrate was plaster for the rhodizonate kits and 

metal for the sulfide kit. As to the goals of this study, the test kit evaluation system using 

manufactured samples was found to be acceptable for predicting performance of test kits on 

nonreactive substrates; that is, the manufactured samples appeared to be representative of the 

archive samples in that the response curves for the archive samples fell between the response 

curves for the white lead- and lead chromate-based paints. For reactive substrates, the 

response curves generated with the archive samples were generally outside of the two curves 

for the white lead- and lead chromate-based paints, indicting significant differences between the 

archive and manufactured samples. One reviewer of this issue paper noted that in Table 12 of 

the Rossiter and co-workers report, there appears to be very little difference between substrate 

types within pigment types for the three best performing kits in the NIST study: LeadCheck Type 

3, Lead Detective Type 2, and MS Sulfide Type 2. The archive study by Cox and others appears 

to have set aside these results for these three kits in favor of following the traditional approach 

of regarding plaster and drywall as not feasible for a rhodizonate kit and metal as not feasible 

for a sulfide kit. However, it appears possible that collected data may have supported the use of 

these three kits as negative screens on their reactive substrates. 

Song, Schlecht, and Ashley (Song et al., 2001; Ashley et al., 2002) present a statistical 

procedure that enables the estimation of performance criteria and characteristics of field 

screening test methods. These methods, along with subsequent confirmatory analysis, allow 

one to evaluate qualitative, semi-quantitative, and quantitative field methods for their potential 

use in screening analysis. False negative rates, false positive rates, sensitivity, and specificity 

are key characteristics of screening methods that can be determined from performance 

characteristic curves. The authors present various options for using multiple test results to 

improve decisions based on test results. 

Examples of other methods for evaluating and validating quantitative analytical procedures 

established by various organizations, such as EPA, include the following. 

• “Environmental Monitoring and Assessment Program (EMAP), Chemical Method Evaluation 

Guidance,” EPA/620/R-96/001, 1996. 

• NELAC Standard, National Environmental Laboratory Accreditation Conference, Quality 

Systems, Appendix C, “Demonstration of Capability,” June 2003. 

• NIOSH Publication No. 95-117: Guidelines for Air Sampling and Analytical Method 

Development and Evaluation, May 1995. 
46

These procedures typically would be followed for the quantitative test kits such as the PaceScan 

kit. 

The Association of Official Analytical Chemists (AOAC) offers the Performance Tested Methods 

Program (http://www.aoac.org/testkits/perftestedmtd.html), which provides an independent thirdparty review of test kit performance claims. Test kits found to be in conformance with their 

claims are granted Performance Tested Methods status by AOAC. The Performance Tested 

Methods status assures the test kit user that independent assessment has been conducted, and 

the kit performs as claimed. 

6.0 SUMMARY AND RECOMMENDATIONS FOR FUTURE 

KIT EVALUATION 

A summary of the studies reviewed in this issue paper are presented in Table 26. Overall, these 

studies give a comprehensive picture of the performance of qualitative and quantitative test kits. 

6.1 Historical Perspective 

Evaluations of Pb test kits have been performed for some 20 years. The original qualitative test 

kits were based on the reaction of Pb with rhodizonate or sulfide to form pink or gray/black 

colors, respectively. Most of the kits developed over the past 15 years also have been based on 

one of these two reagents because of their specificity for Pb and the ease of visualizing the 

formation of the characteristic color. The sensitivity of the qualitative kits has changed very little. 

Evaluations performed in the early 1990s and more recently demonstrated that most of the 

rhodizonate- and sulfide-based test kits show a positive visual response to only a few 

micrograms of Pb, which makes them conservative and protective but also results in a large 

percentage of false positive responses relative to the Federal regulated level of 1 mg Pb/cm2

 or 

0.5% Pb. Figure 3 in this document shows the inflection point of the response curve for 

LeadCheck to be at about 0.3 mg/cm2

, whereas Figure 4 in this document shows the inflection 

point of the response curve for MA Sulfide to be at about 0.8 mg/cm2

; both show positive 

responses at levels less than 1 mg/cm2

.

Qualitative Pb test kits now are being developed using enzymes and immunochemistry. These 

biochemical systems provide high selectivity for Pb and may show fewer metal interferences 

than the rhodizonate or sulfide approaches. They also provide very sensitive measurements, 

reacting to the same low levels that are detected with rhodizonate and sulfide. One of the issues 

to be addressed is the stability of these biochemical systems. Being organic, they are subject to 

oxidation, loss of activity (denaturation), and sensitivity to the pH and ionic strength of the test 

solution. 

The quantitative methods (colorimetry, ASV, reflectometry, and fluorescence) have been in the 

analyst’s collection of tools for many, many years. What is relatively new in the last 15 years or 

so is the miniaturization of the instruments, which makes them suitable for use in the field. 

These newer, miniaturized versions are small, rugged, and relatively easy to use. The same is 

true for instruments used for preparation of the paint samples, such as field-portable microwave 

ovens and ultrasonic baths.

6.2 Issues with Qualitative or Spot Test Kits 

In the recent past, a number of controlled laboratory studies and field studies of qualitative or 

spot test kits have been performed. Standard test solutions and real-world and synthetic paint 
Table 26. Summary of Studies Reviewed in This Issue Paper 

Kit Types 

Testing 

Location Application Reference Materials Used Other M

Report 

Section 

Study 

Year Reference 

Rhodizonate 

Sulfide 

Quantitiative 

Lab 

Field 

In situ 

Ex situ 

Real World 

Synthetic 

Ground 

Films 

Chips 

Solution Number of Samples/ Number of Tests 

XRF 

AA 

1.1.1 1990 Blackburn (1990) ● ● ● Unknown/ 377 ● 3.1.1 1993 Luk et al. (1993b) ● ● ● ● ● ● 27/144 3.1.2 1993 EPA (1995b) ● ● ● ● ● 1290/7740 3.1.3 1994 Adler (1994) ● ● ● ● 1/179 3.1.4 1998 Sharman and Krenzelok (1996) ● ● ● ● 26/78 ● 3.1.5 1995 Gutknecht et al. (1997) ● ● ● ● ● ● 18/378 3.1.6 1998 Ashley et al. (1998) ● ● ● ● ● ● 166/166 ● ● 3.1.7 1997 Gutknecht et al. (1999) ● ● ● ● ● 115/2415 3.1.8 2000 Rossiter et al. (2000) ● ● ● ● ● ● 20/3000 3.1.9 2000 Cox et al. (2001) ● ● ● ● ● ● 124/1420 

47
Table 26. Summary of Studies Reviewed in This Issue Paper (cont’d.) 

Kit Types 

Testing 

Location Application Reference Materials Used Other 

Report 

Section 

Study 

Year Reference 

Rhodizonate 

Sulfide 

Quantitiative 

Lab 

Field 

In situ 

Ex situ 

Real World 

Synthetic 

Ground 

Films 

Chips 

Solution Number of Samples/ Number of Tests 

XRF 

3.1.10 2006 Weydt (2006) ● ● ● ● Unknown 3.1.11 2005 Lu (2005) Enzyme ● ● ● 26+/ Unknown 

3.2.2 1996 Williams et al. (1996) ● ● ● ● 8/55 3.2.3 1993 Gutknecht et al. (1997) ● ● ● ● 115/345 

48
49

samples have been used for these evaluations. The data presented in the preceding sections of 

this paper, which are representative of the data collected in these studies, clearly show that the 

spot or qualitative test kits have great variability in their responses to Pb in paint samples. The 

results of these studies also show that most kits show a relatively large number of positive 

responses to levels below 1 mg Pb/cm2

, but many fewer negative responses for levels above 

1 mg Pb/cm2. As shown in the work by Luk et al. (1991), the test kits are very sensitive, 

responding positively to only a few micrograms of Pb. Therefore, as most data show, these 

rhodizonate- and sulfide-based spot test kits are generally useful as screening tools for the 

presence of Pb in paint, including very low or “zero” Pb concentrations. 

Various factors account for the lack of reproducible results with direct testing of the paint 

surface. One is that the extraction reagents used in the kits are mild, and, therefore, the amount 

of Pb released for reaction depends on the form of the Pb. Harper et al. (1995) point out that 

inconsistent extraction is one of the primary sources of varying responses. Also, the substrates 

give rise to interferences; calcium in plaster reduces the rhodizonate response, and metal 

substrates cause false positive responses with the sulfide-based kits. The structure of the layers 

of the paint also affects the results. Variation in the structural composition that could include thin 

layers of highly leaded paint overcoated with other layers of either leaded or nonleaded paint 

will have an impact on the tester’s ability to get a reliable visual response. A homogeneous thin 

layer of paint at 1 mg Pb/cm2

 would be expected to test differently than a homogeneous thick 

layer of paint at 1 mg Pb/cm2

. 

With qualitative or spot test kits applied to whole or intact paint, it appears to be very difficult to 

meet the measurement goal, “Demonstrated probability (with 95% confidence) of a false 

positive response no more than 10% of the time to Pb levels below the regulated level.” 

However, it appears the goal, “Demonstrated probability (with 95% confidence) of a false 

negative response less than 5% of the time to Pb levels above the regulated level,” already has 

been met. That is, a test kit easily can be made to react with a minimum amount of Pb expected 

(e.g., a few micrograms), and, therefore, usually be positive above the action level. However, 

having a qualitative or spot test kit applied to whole or intact paint that shows no reaction until 

very close to 1 mg Pb/cm2 or 0.5% Pb will not be reliable because the amount of Pb released for 

reaction with the test kit reagent(s) cannot, as of this time, be controlled. 

Reviewers who commented in EPA Docket # EPA-HQ-OPPT-2006-0044 expressed concerns 

(by more than 10 to 1) about the “reliability, acceptability, and availability of the test kits” (see 

www.regulation.gov). 

In summary, issues that make it difficult for the direct contact, qualitative, or spot test to meet 

the proposed Federal performance standards described previously include 

• variability in the effective sample size (e.g., paint surface versus cut notch); 

• weakness of the kit’s Pb extraction reagent; 

• variability in the chemistry/extractability of the extraction reagent from kit type to kit type; 

• variability in the amount of Pb exposed for extraction from test point to test point on the same 

paint; 

• rate of extraction; 

• effects of varying Pb-containing layer thickness and the presence of additional layers of 

Pb-containing and low-Pb paint; 

• presence of interfering metals or substrates; and 

• capability of the reagents rhodizonate and sulfide to form visually apparent responses with 

only a few micrograms of Pb in solution, thereby yielding a large number of false positive 

results relative to the proposed Federal performance standards. 
50

6.3 Addressing the Basic Issue of Performance 

The most basic issue leading to “false” positive results (as defined by the proposed Federal 

performance standards) is the uncontrolled extraction of Pb from paint during direct-contact 

testing. The high sensitivity of the currently available qualitative test kits, in a sense, 

compensates for this variability, making these tests very well suited for screening for Pb and 

especially useful to the homeowner as a conservative, protective tool. However, to meet the 

goal of less than 10% false positives, there is need to quantitatively control the fraction or 

amount of Pb extracted from the paint. It appears that the only way to control this extraction is to 

extract an entire, well-defined sample. 

The qualitative test kits have potential for meeting the proposed Federal performance standards 

if we assume the following. 

• The paint samples are well defined by collecting a known area or mass. 

• The samples are homogenized. 

• At least 90% of the original Pb is “available” for reaction with the test kit reagents. 

This view is based on the fact that the transition from negative response to positive response is 

narrow, as available amount of Pb ion changes. Table 27 summarizes the ranges from all 

negative to all positive from Luk et al. (1993b). 

Table 27. Test Kit Response to Pb Ion [from Pb(NO3)2] in Solution: 100% Negative to 

100% Positive (Luk et al., 1993b) 

Test Kit Range from All Negative to All Positive 

LeadCheck 0.5 to 1.0 μg 

Verify LeadTest 0.1 to 0.3 μg 

Frandon Lead Alert 0.5 to 0.7 μg 

Merck EM Quant 0.5 to 0.6 μg 

Lead Detective 0.5 to 2.0 μg 

Development of a qualitative test kit that provides a sharp transition or “end point” with a 

solution representing 1 mg/cm2

 (or 0.5%) concentration of Pb possibly could achieve the 

proposed Federal performance standards. One possible way to achieve such an end point is to 

use quantitatively controlled amounts of reagents that visually indicate the complete reaction of 

an exact amount of Pb. 

Solubilizing the Pb opens up the possibility of using semi-quantitative or quantitative test kits for 

the analysis. Use of these kits most likely will be more costly in terms of time and equipment 

than will the qualitative kits. Nevertheless, quantitative kits should be considered as tools for 

meeting the proposed standards because they already have been shown to work well. One can 

see in the laboratory work of Luk et al. (1993b) presented in Section 3.2.3 that the Hach 

colorimeter yields results within about 10% of those expected with real-world paints. In the work 

of Williams et al. (1996), as described in Section 3.2.2, the mean recovery with laboratoryprepared samples averaged about 100% for the Reflectoquant and about 90% for the 

PaceScan ASV system. 

6.4 Method Selection and/or Development 

Any manufacturer or research group that identifies a current method, modifies a current method, 

or develops a new method that meets the proposed Federal performance standards will need to 

address the main issue of performance described above (uncontrolled extraction of Pb from 
51

paint during direct-contact testing). To successfully address this issue of quantitative recovery of 

Pb, new or modified methods will need to 

• collect a defined sample, 

• prepare the sample for extraction/solubilization of the Pb, and 

• perform actual quantitative extraction/solubilization of the Pb. 

As noted in previous sections of this document, Pb in solution can be measured by a variety of 

field portable methods. One of the challenges to be met by the developers is dealing with any 

adverse reactions between the chemistry of the Pb measurement method and components of 

the paint other than Pb and/or the reagents used to extract/solubilize the Pb. 

6.5 Method Evaluation 

When a test kit has been identified or developed that potentially will meet the proposed Federal 

performance standards, it must be put through a thorough series of tests to validate its 

performance. Evaluation of a candidate test kit should be performed both in the laboratory and 

the field. One of the standard methods described in Section 5 is recommended. In the 

laboratory, the evaluation would include testing with standard Pb solutions, standard paint 

extracts, and known synthetic and real-world paint samples. 

6.5.1 Performance Evaluation Samples 

6.5.1.1 Sample Preparation 

The size of the sample will be determined by the sample requirements of the measurement 

method, with more sensitive methods requiring less sample than less sensitive methods. 

Preparation of standard Pb solutions is straightforward. Standard paint samples to be used 

include ground real-world paint samples, such as NIST SRMs and those used in the ELPAT 

program; paint films prepared in the laboratory also could be included. 

Using laboratory-prepared paint film samples and real-world paint samples adds the challenge 

of preparing these intact paint chips or films for extraction. As noted, the size of the sample will 

be determined by the sample requirements of the measurement; sample size is also important 

because a larger sample is generally more representative of the whole area (e.g., painted wall) 

than a small sample. In past studies, field-collected paint samples sizes have varied from circles 

1 cm in diameter to squares 2 in on a side. 

Pulverizing, grinding, or mashing the paint samples into pieces or particles small enough for 

efficient extraction is affected by the thickness, layering, and brittleness/hardness of the sample. 

Harper and Gutknecht (2001) collected paint samples of varying sizes (areas and masses) at 

different locations across a variety of surfaces, including metal, plaster, concrete, and wood, 

and compared a variety of grinding techniques. Manual mortar and pestle grinding for at least 

1.5 min and mechanized grinding techniques were found to generate similar homogenous 

particle size distributions required for aliquots as small as 0.10 g. However, simple grinding in a 

centrifuge tube with a glass rod is unlikely to yield this same degree of homogeneity. When 

samples were about 0.1 g or less, there was a significant amount of sample left in or on the 

grinding apparatus. Homogenization and subsampling steps were found to be the principal 

sources of variability related to the size of the sample collected. In addition, suitable 

homogenization takes time and, therefore, increases costs. 

The challenge for preground, homogenized paint samples is the efficiency of the extraction. The 

efficiency of the extraction reagent/procedure for such samples already may be known from 

previous studies. If not known, the extraction efficiency would be determined by (1) “hard” or 

total digestion of an aliquot of the extract collected by the candidate method; (2) “hard” or total 

digestion of the postextraction paint residue; and (3) measurement of both these total digestion 
52

extracts by AAS or ICP-OES to determine the true amount extracted versus the true or 

expected amount present in the original sample, respectively. One also could perform total 

digestion and ICP analysis of the original, well-homogenized ground paint samples to determine 

the expected concentration. 

The Pb concentration of a real-world paint chip cannot be estimated accurately before analysis. 

Every chip collected, even if from the same painted surface, is different; no two are identical 

because of differences in application of paint across the surface. At the beginning of an 

application, the paint brush or roller is loaded heavily and the paint application is relatively thick. 

At the end of the application, the brush loading is light and the paint application is relatively thin. 

Multiple applications of paint over time compound this difference in the paint composition from 

point to point across a surface. The only way to determine the original Pb concentration value 

for a real-world paint chip is to perform a “hard” or total digestion of the solution and paint 

residue remaining after drawing an aliquot for the test kit measurement and then to analyze this 

digestate with AAS or ICP-OES. The acceptability of the total Pb solubilization procedure— 

sample grinding or pulverizing plus extraction—is determined by the amount of Pb in the extract 

relative to the original or expected amount in the paint sample. 

6.5.1.2 Laboratory-Prepared Paint Films 

Laboratory-prepared paint films have been used by other researchers (Luk et al., 1993b; 

Rossiter et al., 2000) for evaluation of test kits. These materials offer the potential of a supply of 

reproducible reference materials that are well characterized and can be used by different 

researchers and manufacturers to evaluate a variety of different test kits, thereby giving 

comparability of evaluation. However, making these films is a challenge. The variables to be 

considered include the following. 

• Chemical composition of the films (e.g., lead carbonate, lead chromate, red lead, linseed oil 

[raw and/or boiled], organometallic driers, or, alternatively, Pb-spiked, available oil-based 

and/or water-based paints) 

• Substrate selection (reactive or nonreactive) 

• Potential range of Pb concentrations 

• Paint film thickness 

• Layering (single layer versus multiple layers) 

• Coatings 

• Achieving acceptable area uniformity 

• Chemical analysis 

• Artificial aging 

Preparing paint mixtures according to old paint recipes is not technically difficult. However, a 

significant effort must be given to preparing very uniform paint films that will be suitable for use 

as reference materials; this is especially true when multiple layering is performed. A major 

consideration is artificial aging of the laboratory paints such that they exhibit the hardness and 

“exposed” state of old paints; there are no fast and easy methods for this process. Because 

every real-world paint is different in terms of the combination of composition, layers, mix of paint 

types, age, and condition, it is impossible to have a set of synthetic test materials that represent 

all paints that will be found in the field. Limits may include (1) thick and thin, (2) brittle and 

rubbery, (3) few layers and many layers, and (4) white lead-based and other Pb-based pigments 

such as chromate. (Most old paints used white lead as the primary pigment.) It is assumed that 

the Pb concentrations needed will include a few (2 to 3) at levels well below and well above the 

action levels (1 mg/cm2

 or 0.5% by weight) and a moderate number (6 to 10) within ±20% of the 

action levels to fully and accurately characterize the transition range for the test kit from 

negative to positive. This means10 to 15 different concentrations for each different paint 
53

material/structure and substrate combination. As per the tests of Rossiter et al. (2000), one 

might simply use wood as a nonreactive substrate and iron and plaster as potentially reactive 

substrates. With 3 different Pb pigments, 2 different overlayers, and 3 substrates, there is the 

potential need for close to 300 test samples for a thorough evaluation of the most promising test 

kit method or methods. 

6.5.2 Evaluating the Testing/Measurement Results 

The evaluation of the measurement component of a kit is relatively straightforward if we assume 

that the only way to meet the proposed Federal performance standards for test kits is to have 

the Pb removed from the paint sample and in solution, and that this can be done successfully. 

Using both standard Pb solutions and “known” paint extracts, the accuracy of a qualitative test 

end point (i.e., the number of negative values when the concentration is less than a value 

equating to 1 mg/cm2

 [or 0.5%] or the number of positive values when the concentration is 

greater than a value equating to 1 mg/cm2

 [or 0.5%]) can be determined. The response versus 

solution concentration data from this correct/incorrect analysis also can be plotted to produce 

characteristic response curves. The response could be quantified several ways: (1) 0 for no 

response or 1 for a positive response; (2) an average numeric value for replicates at each 

concentration; or (3) giving the intensity of the response a numeric value, as done by Gutknecht 

et al. (1999). The curve could be modeled as done by EPA (1995b) to yield predictions of the 

probability of positive response as a function of test sample concentration. 

6.6 Summary 

In summary, if it is assumed that the accuracy and precision are improved by ex situ testing 

(i.e., analysis of the paint removed from its source), there are still a number of issues to be met 

to meet the proposed Federal test kit performance standards (see just below). 

• Collecting a representative sample or samples of paint 

• Removing an intact sample without substrate (which may have high Pb levels) 

• Accurately controlling or knowing the paint sample area for subsequent area concentration 

calculations 

• Breaking, crushing, grinding, etc., the paint sample to allow rapid Pb extraction and 

dissolution 

• Finding and using an extraction reagent that will extract 90+% of the Pb in the prepared 

(ground) paint sample while still being safe and relatively convenient to use in the field 

• Identifying an apparatus (e.g., ultrasonic bath or field microwave oven) that can be used in the 

field to promote the dissolution of the Pb 

• Applying an analytical method that will yield an accurate (±10%) measure of the Pb in solution 

and be relatively safe to use, with minimum waste generation 

These challenges go beyond the technical issues. Labor requirements and material costs must 

be optimized to meet those proposed goals that relate to time of analysis and cost—less than 

1 h and less than $2 in materials per sample. Finally, the final test kit procedure will need to be 

reasonably easy to perform with some minimum level of training. 

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Technology, 2(1):39-50. 
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