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Copyright © 2006 Air & Waste Management Association 
Validation of Three New Methods for Determination of Metal

Emissions Using a Modified Environmental Protection Agency

Method 301

Catherine A. Yanca, Douglas C. Barth, Krag A. Petterson, Michael P. Nakanishi, and

John A. Cooper

Cooper Environmental Services, LLC, Portland, OR

Bruce E. Johnsen

SAIF Co., Portland, OR

Richard H. Lambert

Engineering Tech Center, Eli Lilly and Co., Indianapolis, IN

Daniel G. Bivins

U.S. Environmental Protection Agency, Research Triangle Park, NC

ABSTRACT

Three new methods applicable to the determination of

hazardous metal concentrations in stationary source

emissions were developed and evaluated for use in U.S.

Environmental Protection Agency (EPA) compliance

applications. Two of the three independent methods, a

continuous emissions monitor-based method (Xact)

and an X-ray-based filter method (XFM), are used to

measure metal emissions. The third method involves a

quantitative aerosol generator (QAG), which produces a

reference aerosol used to evaluate the measurement

methods. A modification of EPA Method 301 was used

to validate the three methods for As, Cd, Cr, Pb, and Hg,

representing three hazardous waste combustor Maximum Achievable Control Technology (MACT) metal

categories (low volatile, semivolatile, and volatile). The

modified procedure tested the methods using more

stringent criteria than EPA Method 301; these criteria

included accuracy, precision, and linearity. The aerosol

generation method was evaluated in the laboratory by

comparing actual with theoretical aerosol concentrations. The measurement methods were evaluated at a

hazardous waste combustor (HWC) by comparing measured with reference aerosol concentrations. The QAG,

Xact, and XFM met the modified Method 301 validation criteria. All three of the methods demonstrated

precisions and accuracies on the order of 5%. In addition, correlation coefficients for each method were on

the order of 0.99, confirming the methods’ linear response and high precision over a wide range of concentrations. The measurement methods should be applicable to emissions from a wide range of sources, and the

reference aerosol generator should be applicable to additional analytes. EPA recently approved an alternative

monitoring petition for an HWC at Eli Lilly’s Tippecanoe site in Lafayette, IN, in which the Xact is used for

demonstrating compliance with the HWC MACT metal

emissions (low volatile, semivolatile, and volatile). The

QAG reference aerosol generator was approved as a

method for providing a quantitative reference aerosol,

which is required for certification and continuing quality assurance of the Xact.

INTRODUCTION

Air toxic metals have been associated with a wide range

of environmental and human health effects, including

respiratory disorders, pulmonary disorders, and cancer.1,2 EPA regulates the emissions of toxic metals from

stationary sources under the National Emission Standards for Hazardous Air Pollutants (NESHAP) or Maximum Achievable Control Technology rule.3 Currently,

emissions are estimated based on control efficiencies

established during performance tests and estimated

feed rates during normal operations. When actual emissions are measured, EPA Reference Method 29 (Method

29) is used.4 However, Method 29 is based on 30-yr-old

IMPLICATIONS

The two measurement methods for determining metal

emissions validated in this study (the Xact and the XFM)

include significant improvements in measurement technology. With these two new methods, plant operators can

make more precise, accurate, and frequent measurements,

leading to a better understanding of emissions. With the

new reference aerosol generator validated in this study (the

QAG), development and evaluation of new measurement

methods are now more practical. The measurement methods are applicable to a wide range of elements and may be

applicable to other sources. The aerosol generator may be

applicable to both organic and inorganic analytes.

TECHNICAL PAPER ISSN 1047-3289 J. Air & Waste Manage. Assoc. 56:1733–1742

Copyright 2006 Air & Waste Management Association

Volume 56 December 2006 Journal of the Air & Waste Management Association 1733
impinger technology with accuracies and precisions on

the order of 15%.5–7 The method also involves hazardous chemicals, and it requires long turnaround times. It

is clear that there are opportunities for improvement in

the current monitoring technology.

There have been attempts over the past decade to

improve metals measurement technology by developing multimetal continuous emissions monitoring systems (CEMS).8 –10 None of the proposed technologies

have been approved for compliance demonstration

other than those discussed in this paper. The new technology presented here includes three new methods applicable to the determination of hazardous metal concentrations in emissions: a multimetal CEMS-based

method (Xact), a sampling and analysis measurement

method (X-ray-based filter method [XFM]), and a National Institute for Standards and Technology (NIST)-

traceable reference aerosol generating method (QAG).

The methods and the instruments used to perform the

methods were developed to provide more precise, accurate, and frequent measurement capabilities than are

offered by Method 29. The Xact method uses a CEMS

based on X-ray fluorescence (XRF) analysis of aerosol

deposits (particulate and vapor phase) on reactive filter

tape.11,12 XFM is comparable to Method 29 but uses

reactive filters (solid sorbants)11,12 instead of impingers

to trap both particulate and vapor phase metals, followed by nondestructive XRF analysis of the filters. The

quantitative aerosol generator (QAG) is based on nebulization of a metal-containing solution and produces a

reference aerosol that can be used to validate measurement methods, such as the Xact and XFM.

To evaluate the performance of the new methods, a

test plan13 based on the requirements of EPA Method

30114 was developed. Method 301 is a defined procedure

for validating new pollutant measurement methods that

could potentially be used to demonstrate compliance

with permits or other EPA applications. A more stringent

modification of this procedure was used to validate the

three methods based on accuracy, precision, and linearity

criteria. This paper presents: (1) an overview of the three

methods, (2) the procedure used for validating these

methods, and (3) the results of the validation tests. Details

about these instruments and methods, performance specifications, and standard operating procedures are presented elsewhere.15–20

EXPERIMENTAL WORK

Quantitative Reference Aerosol Generation

The method for generating a quantitative reference

aerosol involves the operation of the QAG instrument.15,21 Using the QAG, an aerosol of analyte solution droplets is created using a nebulizer.21,22 The droplets are then passed into a settling chamber where the

large droplets are removed and liquid and vapor phases

are equilibrated. Droplets 30 m in diameter are allowed to pass into a drying chamber where they are

dried before being emitted. The aerosol exiting the drying chamber consists of the transport gas, water and

metal vapor, and dried salt particles. The aerosol emission concentration (Ca) is calculated from the analyte

concentration in the nebulized solution (Cs), the solution emission rate (Rm) corrected for vapor loss (Rv),

and the total volume of nebulizing, drying, and dilution gas used to create the aerosol (Ft

).

Ca  Cs

Ft

Rm Rv (1)

Quantitation of the emitted aerosol is made possible by:

(1) using a large reservoir of NIST-traceable analyte solution to minimize the impact of evaporation on solution

concentration, (2) continuously measuring the solution

emission rate (Rm) with a NIST-traceable balance, (3) precise control of nebulizer conditions, and (4) stable control

of the maximum droplet size introduced into the generator’s drying chamber such that only aerosols with high

transport efficiencies are generated. The reference aerosol

produced by the QAG is process NIST traceable and can be

used in addition to its other applications to challenge and

evaluate the accuracy, precision, and linearity of the measurement methods. It is applicable to both metal and

nonmetal species.

Metal Concentration Measurement

Xact. The Xact method of metals measurement uses a

CEMS, called the Xact CEMS, that collects and analyzes

a sample of emissions using filter-based technology and

nondestructive XRF.15,23 During sample collection, the

Xact CEMS directs a continuous flow of stack gas

through a stilling chamber where its velocity is reduced

(i.e., stilled). A continuous subsample is taken from the

stilling chamber and drawn through chemically-reactive filter tape, which traps both particulate and vaporphase metals.11,12,23 The volume of the sample flow is

measured, and the filter tape deposits are advanced to a

position where they are analyzed for metal mass using

XRF analytical procedures similar to those listed in

EPA’s Compendium Method IO-3.3.24 The Xact CEMS

then divides the XRF-determined mass per sample by

the volume per sample and simultaneously reports concentrations for 20 analyte metals every 15 min. During analysis of the current sample, the next sample is

automatically collected. In the Xact CEMS, sampling

and analysis is performed continuously in the same

instrument except for the time required to advance the

tape (3 sec) and the time required for automated

quality assurance checks (1 hr, once per day). Detection limits for the Xact CEMS are listed in Table 1 and

range from 0.1 g/dry standard cubic meter (dscm) to

6 g/dscm with 15-min sampling times. These limits

can be lowered significantly by varying sampling and

analysis conditions. Both the XFM and Xact methods

are generally applicable to elements with atomic numbers ranging from 13 (Al) to 92 (U).

XFM. Like the Xact, the XFM uses filter-based technology

to collect a representative sample of emissions followed

by nondestructive XRF analysis of the sample.15,23 For

sample collection, the XFM sampling train connects to a

stilling chamber, such as the one used for the Xact CEMS.

A representative sample of stack gas is continuously directed into the stilling chamber (at 30 –100 L/min), and

Yanca et al.

1734 Journal of the Air & Waste Management Association Volume 56 December 2006
the XFM pulls a subsample of 1 L/min into its sampling

train. The subsample is diluted and cooled before being

drawn through a stacked filter cassette containing a polytetrafluoroethylene filter followed by a chemically reactive filter.11,12,23 Particulate-phase metals are trapped on

the nonreactive polytetrafluoroethylene filter, whereas

vapor-phase metals, including Hg, are collected on the

chemically reactive filter or solid sorbent. After sample

collection, the filter cassettes are removed from the sampling train, and the resulting filter deposits are analyzed

for metal mass using nondestructive XRF procedures similar to those listed in EPA’s Compendium Method IO3.3.24 The filters do not require handling during any part

of the XFM procedure, and they can be readily shipped to

a laboratory for analysis or analyzed in the field. The

emissions concentration is calculated by dividing the

XRF-determined metal mass by the volume of emissions

that passed through the filters. Typical sample times are

30 min, and analysis turnaround times can be on the

order of a few hours with a field-portable XRF analyzer.

Detection limits typically range from 0.06 g/dscm to 1.6

g/dscm with 30-min sample times (Table 1). Substantially lower detection limits can be attained by varying

sampling and analysis conditions.

Method Independence

The QAG-generated aerosol concentration is independent

of the aerosol concentrations measured by the Xact and

XFM. Method independence is confirmed using NIST

traceability and additional procedures. The concentration

of the aerosol produced by the QAG is procedurally traceable to NIST through nebulized solution standards and

QAG operating parameters. The XFM- and Xact-measured

concentrations are both analytically NIST traceable

through thin film standards and NIST Standard Reference

Materials 1832 and 1833. In addition to the independent

NIST traceability of the generation and measurement

methods, inductively coupled plasma (ICP) analysis conducted at an independent laboratory (Chester LabNet,

Tigard, OR) confirmed the standard solution concentrations used in the QAG and the filter deposit measurements made by the XFM method.

Validation Methodology

The procedures used to validate the QAG, XFM, and Xact

were based on EPA Method 301. This EPA method is

required when new methods of measuring analytes are to

be used on a source in lieu of the standard reference

method. Method 301 establishes accuracy and precision

capabilities of a new method by comparing its determined

concentrations with those of an accepted reference

method. The resulting bias between concentrations from

the two methods is used as an indicator of accuracy.

Simultaneous method measurements are used to determine precision. Following normal Method 301 procedures, the Xact and XFM measurement methods would be

tested against Reference Method 29. However, the precision and accuracy of Method 29, which are on the order

of 15%,5–7 were insufficient for verifying the precisions

and accuracies believed to be attainable with the Xact and

the XFM (i.e., potential precision 5% and accuracy

5%). The validation procedure presented in this section

is a modified Method 301 in which Method 29 comparisons were replaced with QAG reference aerosol comparisons.13 This modified method was more stringent than

Method 301, because it included more replicate runs,

sequential measurements instead of simultaneous measurements, additional validation criteria (e.g., linearity),

and independent NIST traceability of results.

The first step in the modified Method 301 procedure

required laboratory validation of the QAG emissions, and

the second step was a field validation of the XFM and Xact

measurements. The general experimental arrangement

used for both laboratory and field tests is schematically

illustrated in Figure 1. First, the QAG generated an aerosol, which was blended with laboratory air for laboratory

tests and stack gas for field tests. The aerosol flow was then

directed into the Xact CEMS stilling chamber15,17,19 from

which the Xact CEMS and XFM simultaneously withdrew

representative samples. After sampling, the XFM filters

were removed and analyzed, whereas the Xact automatically reported metal concentrations every 15 min for the

duration of the test. It should be noted that an Xact CEMS

located at the Cooper Environmental Services facility was

Table 1. Xact and XFM detection limits.

Element

Xacta

(g/dscm)

XFMb

(g/dscm)

Cr 0.3 0.08

As 0.1 0.08

Cd 2.4 0.8

Hg 0.3 0.14

Pb 0.6 0.12

Mn 0.2 0.08

Co 0.3 0.08

Ni 0.3 0.06

Se 0.1 0.08

Ag 4.2 0.6

Sb 6.2 1.6

Cu 0.5 0.08

Fe 0.9 0.12

Zn 0.2 0.06

Br 0.4 0.2

Sr 0.3 0.18

Tl 0.3 0.14

Notes: a

95% Confidence, interference free, 15-min sample. b95% confidence,

interference free, 30-min sample.

Figure 1. Experimental arrangement for laboratory and field tests.

Yanca et al.

Volume 56 December 2006 Journal of the Air & Waste Management Association 1735
used in the laboratory tests, and an Xact CEMS located at

Eli Lilly and Company’s Tippecanoe facility in Lafayette,

IN, was used in the field.

QAG Laboratory Validation. The QAG was evaluated in a

series of laboratory tests15 in which a QAG-generated

aerosol was combined with ambient laboratory air and

simultaneously sampled by the Xact CEMS and XFM sampling train. The theoretical QAG concentration calculated

using eq 1 was then compared with the actual concentrations measured with the Xact and XFM to determine the

accuracy, precision, and linearity of the QAG method. All

of the QAG-generated aerosols contained As, Cd, Cr, Pb,

and Hg, representing the volatile, semivolatile, and lowvolatility metal categories as defined in the NESHAP HWC

rule.3 Tests were conducted at four concentration levels

(high, mid, low, and blank) ranging from 0 to 130

g/dscm. In these laboratory tests, the QAG aerosol concentrations were compared with results from a total of 22

XFM and 135 Xact runs. Only Xact runs that corresponded with simultaneous XFM runs were used for accuracy and precision determinations. All of the runs for

both methods were used in the linear regression analysis.

The XFM sample time was 30 min per run and the Xact

was 15 min; concentrations from two Xact runs were

averaged to represent a 30-min sample period for comparison with the XFM. All of the methods were performed

according to specifications set forth by their test method

and standard operating procedures.15–20

Xact and XFM Field Validation. The Xact and the XFM

were evaluated in a series of field tests conducted at a

hazardous waste incinerator, where an Xact CEMS was in

operation.15 For each field test, the validated QAG was

used to generate a reference aerosol of known concentration, which was spiked into the hazardous waste incinerator flue gas. This dynamically-spiked flue gas was transported to the Xact CEMS stilling chamber where it was

simultaneously sampled by the Xact CEMS and XFM sampling train. Measured concentrations from each method

were compared with the QAG-spiked stack gas concentration to determine the accuracy and precision of the Xact

and XFM methods. All of the QAG-generated aerosols

contained As, Cd, Cr, Pb, and Hg, and tests were conducted at four concentration levels (high, mid, low, and

blank) ranging from 0 to 130 g/dscm. During these

field tests, a total of 24 XFM and 192 Xact runs were

compared with the QAG aerosol concentrations. Again,

only corresponding Xact/XFM runs were used for accuracy and precision determinations, but all of the runs

were used for linear regression analysis. During these

tests, the background concentrations of the stack gas were

negligible relative to the spiked stack gas concentrations.

All of the methods were performed according to specifications set forth by their test method and standard operating procedures.15–20

Validation Criteria

Criteria for method validation were based on Method 301

bias and precision requirements and were either equal to

those listed in Method 301 or were more stringent. A

general criterion for all of the validation tests was that 9

runs had to be used to demonstrate acceptable values for

accuracy, precision, and linearity.25 Accuracy, precision,

and linearity criteria are defined and discussed below.

Accuracy. Accuracy for the ith element (Ai

) is defined as

bias (Bi

, g/dscm) divided by the theoretical or reference

concentration of the QAG generated aerosol (Ci

QAG, g/

dscm), expressed as a percent.

Ai  Bi

Ci

QAG  100 (2)

Bias is the difference between the mean measured aerosol

concentration (C i

M, g/dscm) and the theoretical or reference concentration (Ci

QAG, g/dscm).

Bi  Ci

M CiQAG (3)

For the QAG, accuracy values 20% were defined as acceptable for validation. For the measurement methods,

this same criterion was required for accuracy values determined at concentrations at or near the emission limit as

required by Method 301. In addition to meeting the

above accuracy criterion, the bias was required to be insignificant relative to the uncertainty in the bias. In this

case, the uncertainty in the bias for the ith element (Ui

B

) is

the square root of the sum of the uncertainty in the QAG

aerosol concentration (Ui

QAG) squared and the standard

deviation of the mean of the measurement method

concentration (SDMi

M) squared, as shown in following

equation:

Ui

B  UiQAG

2  SDMi

M

2 (4)

where the QAG propagated uncertainty was estimated to

be 5% during the laboratory and field tests.15 Bias was

considered significant at the 95% confidence level if Bi 

2Ui

B

. If Bi was found to be significant, a correction factor

was required. The correction factor (CFi

) is calculated by

dividing the concentration of the QAG aerosol (Ci

QAG) by

the concentration of the measurement method (Ci

M).

CFiCi

QAG

Ci

M (5)

Precision. Total precision for the ith element (Pi

t

) is defined as percent relative standard deviation (PRSDi

), or the

standard deviation (SDi

) divided by the mean concentration (C i

) of a given method determined from sequential

measurements.

Pi

t  SDi

Ci

 100 (6)

Because there is random variability associated with both

the QAG aerosol concentration, as well as the measured

aerosol concentration, the total precision (Pi

t

) is an indicator of the combined variability introduced by all

Yanca et al.

1736 Journal of the Air & Waste Management Association Volume 56 December 2006
components of the generation-measurement system; that

is, QAG and measurement method. For this series of tests,

the magnitude of the QAG precision is considered to be

the same as the measurement method. Therefore, the

individual precision of the QAG or measurement method

(Pi

) is defined as the combined, or total, precision (Pi

t

)

divided by the square root of 2.

Pi  PRSDi  Pi

t

2 (7)

A precision 10% was required for the method to satisfy

established validation requirements.

Linearity. Evaluation of linearity was based on parameters

derived from a linear least squares regression analysis of

the theoretical or reference concentrations and the measured concentrations. Although slope and intercept of the

regression line were considered, the key linearity criterion

was the correlation coefficient (r). The QAG and both

measurement methods must have a correlation coefficient (r) that is 0.85 for method validation.

RESULTS AND DISCUSSION

QAG Validation

Accuracy. QAG accuracy results for each of the five metals

tested are listed in Table 2. This table includes results from

a comparison of theoretical QAG concentrations with 40

Xact and 20 corresponding XFM measurements. Concentrations ranged from a low of 20 g/dscm to a high of

130 g/dscm. The QAG demonstrated accuracies 7%

for all of the elements at each concentration level, well

below the 20% validation threshold. These results show

that average QAG accuracy for all runs ranged from a low

of 1.3% for Hg as measured with the Xact to a high of

4.7% for Hg as measured with the XFM. The overall average accuracy including all five elements, all three concentration levels, and both methods is 2.5  2.3%. None of

the biases were determined to be significant. In addition,

independent ICP analysis of a nebulized solution and

Table 2. QAG accuracy determined during laboratory tests.

Measurement

Method Element

Low Concentration

(20 g/dscm)

Mid Concentration

(65 g/dscm)

High Concentration

(130 g/dscm) Average All Runs

N Accuracy Ai % SD N Accuracy Ai % SD N Accuracy Ai % SD N Accuracy Ai % SD

Xact

Cr 8 1.7 1.0 24 1.4 1.4 8 2.4 0.3 40 1.6 1.2

As 8 1.9 1.7 24 4.1 1.7 8 4.9 1.0 40 3.8 1.9

Hg 8 2.3 1.4 24 1.3 1.0 8 0.6 0.5 40 1.3 1.1

Pb 8 2.9 2.1 24 1.5 0.8 8 1.6 1.1 40 1.8 1.2

Cd 8 2.8 1.8 24 1.7 0.9 8 2.0 1.5 40 2.0 1.2

XFM

Cr 4 2.5 1.9 12 2.7 2.7 4 1.5 1.4 20 2.4 2.3

As 4 2.5 1.2 12 3.0 3.0 4 2.6 1.5 20 2.8 2.4

Hg 4 6.3 1.1 12 3.5 3.0 4 6.7 5.1 20 4.7 3.5

Pb 4 2.2 2.2 12 2.3 2.6 4 2.3 1.5 20 2.3 2.2

Cd 4 6.2 3.4 12 2.0 1.4 4 1.1 0.8 20 2.6 2.5

Notes: SD  standard deviation.

Table 3. QAG precision determined during laboratory tests.

Measurement

Method Element

Low Concentration

(20 g/dscm)

Mid Concentration

(65 g/dscm)

High Concentration

(130 g/dscm) Average All Runs

N Precision Pi % N Precision Pi % N Precision Pi % n Precision Pi %

Xact

Cr 8 1.7 24 1.1 8 1.7 40 1.0

As 8 2.0 24 1.0 8 2.0 40 1.2

Hg 8 2.0 24 0.7 8 2.0 40 1.1

Pb 8 2.0 24 0.8 8 2.0 40 1.3

Cd 8 2.5 24 1.5 8 2.5 40 1.7

XFM

Cr 4 1.3 12 2.3 4 1.3 20 1.5

As 4 1.8 12 2.2 4 1.8 20 1.7

Hg 4 0.8 12 2.8 4 0.8 20 2.4

Pb 4 1.7 12 2.2 4 1.7 20 1.6

Cd 4 2.3 12 1.9 4 2.3 20 1.7

Yanca et al.

Volume 56 December 2006 Journal of the Air & Waste Management Association 1737
selected filter samples were supportive of the XFM measured concentrations. Clearly, these results demonstrate

that the QAG is an accurate method for generating a

reference aerosol containing metal concentrations in the

range from 20 to 130 g/dscm.

Precision. Precision for the QAG and the measurement

methods tested in the field was determined from sequential measurements taken during a period of 4 hr. The

results from these tests are presented in Table 3. The QAG

demonstrated precisions well below the 10% validation

threshold; average precisions were better than 3% for all

of the elements at each concentration level. The average

QAG precision for all of the runs ranged from a low of 1%

for Cr as measured with the Xact to a high of 2.4% for Hg

as measured with XFM. Including all five of the elements,

all three of the concentration levels, and both measurement methods, the average QAG precision was 2.2%.

These results show that the QAG is a precise method for

generating aerosols in the concentration range from 20 to

130 g/dscm.

Linearity. Linearity of the QAG was analyzed with linear

least-squares regressions of the measured aerosol concentrations compared with the theoretical concentrations

over all of the concentration levels. Correlation coefficients (r), slopes, and intercepts from these regressions are

presented for each element in Table 4. The correlation

coefficients for all of the elements as determined with

each measurement method were 0.99, well above the

acceptability requirement of 0.85. Slopes ranged from a

low of 0.98 to a high of 1.05, all within 5% of unity (i.e.,

1.00). Intercepts ranged from 	0.01 to 	1.13 and were all

1% of the concentration range. Plots of the regression

analyses using all 5 of the metals combined are presented

for the Xact in Figure 2 and for the XFM in Figure 3. The

QAG again demonstrated correlation coefficients of 0.99,

and slopes were within 0.4% of 1.00. Intercepts were

0.3% of the concentration range. A final regression analysis of all of the measured versus theoretical QAG data

yielded a 0.998 correlation coefficient, a slope within

0.2% of unity (0.998  0.002), and an intercept 0.1% of

the concentration range (	0.04  0.16). This strong linear relationship between the theoretical QAG aerosol concentrations and the independently measured concentrations demonstrates the ability of the QAG to produce

aerosols quantitatively over a wide range of concentrations.

Xact Method Validation

Accuracy. The Xact met the 20% validation criterion for

accuracies demonstrated at the high concentration level

(Table 5). For the measurement methods, this level is

expected to be most representative of concentrations near

the emission limit as required by Method 301. For the 24

high-concentration runs, the Xact accuracies ranged from

1.8% for As to a high of 13% for Hg. The Xact average

accuracies for all 40 runs ranged from a low of 4.9% for As

to a high of 16% for Hg. The average Xact accuracy calculated using all five of the elements was 4.7  4.3% for

the high concentration and 8.3  7.2% for all three of the

concentration levels.

Bias was insignificant for four of the five metals but

was significant for Hg at all of the concentration levels. A

post-test investigation of this bias revealed a 6% calibration error, although these runs were retained in the dataset without correction. Assuming correct calibration, the

Hg accuracies would have been on the same order as the

accuracies of the other four elements; for example, the Hg

accuracy at the high concentration level would be 7% (i.e.,

Table 4. QAG linearity determined during laboratory tests.

Method

Element n R Slope SD Intercept SD

XFM

Cr 22 0.999 1.02 0.005 	0.54 0.35

As 22 0.999 1.05 0.005 	0.71 0.38

Hg 22 0.999 0.99 0.004 	0.01 0.32

Pb 22 0.999 1.02 0.007 	1.13 0.51

Cd 22 0.999 0.98 0.008 0.72 0.56

Xact

Cr 135 0.999 1.01 0.004 	0.42 0.25

As 135 0.999 0.98 0.004 0.31 0.26

Hg 135 0.999 1.04 0.004 	0.67 0.25

Pb 135 0.999 1.00 0.005 	0.41 0.30

Cd 135 0.998 0.98 0.005 0.27 0.35

Notes: SD  standard deviation.

Figure 2. QAG linearity as determined by the Xact using all five

elements.

Figure 3. QAG linearity as determined by the XFM using all five

elements.

Yanca et al.

1738 Journal of the Air & Waste Management Association Volume 56 December 2006
6% of the 13% accuracy can be attributed to the calibration

error). This identified error can be readily corrected and

future bias, thus, eliminated. As a result, a correction factor

was not required. In addition to the calibration error, the

average accuracies for both the Xact and XFM (discussed

below) were somewhat impacted by biases in the middle

concentration runs. These biases appear to be the result of

an increased difficulty in maintaining proper QAG operating conditions in the field compared with the laboratory.

The biases were not significant, and these runs were retained

in the dataset. The results presented in Table 5 demonstrate

a high accuracy for the Xact measurement method even

with the Hg calibration error and midconcentration biases.

Furthermore, these results suggest even better accuracies

with correct Hg calibrations.

Precision. The Xact demonstrated better than 4% for all of

the concentration levels, well below the 10% validation

threshold (Table 6). The average precision for all of the

Xact runs ranged from a low of 1.4% for Hg to a high of

1.9% for Cd. Over all five of the elements and all three of

the concentration levels, the total average precision for

the Xact was calculated as 1.6%. These results demonstrate the high precision of the Xact over a wide range of

concentrations.

Linearity. Xact linearity was evaluated with linear leastsquares regression analysis of the Xact-measured concentrations compared with the QAG-spiked stack gas reference concentrations over all of the concentration levels.

Regression parameters for each element are presented in

Table 7. Xact correlation coefficients for all of the elements were 0.99, easily surpassing the 0.85 requirement. Slopes for all of the metals ranged from 0.87 for Hg

to a high of 1.02 for Pb. Intercepts ranged from 	0.79 to

	1.09, all 1% of the concentration range. A plotted

regression analysis for all 5 of the metals combined (Figure 4) produced a correlation coefficient of 0.995, a slope

within 5% of unity (0.952  0.003), and an intercept 2%

of the concentration range (	1.10  0.18). The strong

linear relationship between the Xact concentrations and

the reference concentrations confirms the Xact linear response and high precision over a wide range of concentrations and demonstrates its ability to accurately measure metals over this range.

XFM Validation

Accuracy. The XFM accuracy results for each element are

presented in Table 8. At the high concentration level, the

XFM accuracies ranged from 3.5% for Hg to 5.8% for Pb,

all well below the 20% validation requirement. None of

the biases were significant relative to their uncertainty.

The average XFM accuracy for all of the runs ranged from

a low of 6% for Cd and As to a high of 7.9% for Pb.

Combining data from all five of the elements, the average

XFM accuracy was calculated as 4.7  3.1% for the high

concentration level and 6.5  4.5% for all three of the

concentration levels. These results clearly demonstrate

the high accuracy of the XFM measurement method.

Precision. The XFM precisions (Table 9) all met the 10%

validation criterion and were better than 7% at all of the

concentration levels. The average XFM precision for all of

Table 5. Xact accuracy determined during field tests.

Element

Low Concentration

(20 g/dscm)

Mid Concentration

(45 g/dscm)

High Concentration

(110 g/dscm) Average All Runs

N Accuracy Ai % SD N Accuracy Ai % SD N Accuracy Ai % SD N Accuracy Ai % SD

Cr 8 7.4 2.9 8 20 1.6 24 4.5 1.7 40 8.2 6.5

As 8 3.3 2.4 8 16 1.9 24 1.8 0.7 40 4.9 5.7

Hg 8 14a 2.1 8 25a 1.7 24 13a 1.0 40 16a 5.2

Pb 8 13 1.4 8 20 1.4 24 2.4 1.5 40 7.9 7.4

Cd 8 3.6 2.6 8 16 1.7 24 2.1 0.8 40 5.2 5.7

Notes: SD  standard deviation; a

Bias was determined to be significant for this value.

Table 6. Xact precision determined during field tests.

Element

Low Concentration

(20 g/dscm)

Mid Concentration

(45 g/dscm)

High Concentration

(110 g/dscm) Average All Runs

N Precision Pi % N Precision Pi % N Precision Pi % N Precision Pi %

Cr 8 2.2 8 1.4 24 1.3 40 1.6

As 8 2.4 8 1.6 24 1.0 40 1.7

Hg 8 1.7 8 1.6 24 0.83 40 1.4

Pb 8 1.2 8 1.3 24 2.0 40 1.5

Cd 8 3.4 8 1.4 24 0.83 40 1.9

Yanca et al.

Volume 56 December 2006 Journal of the Air & Waste Management Association 1739
the runs ranged from a low of 1.8% for Cr and As and to

a high of 3.7% for Pb. The total average XFM precision

was calculated as 2.6% over all five of the elements and all

three of the concentration levels. These results demonstrate that the XFM met this acceptance criterion and is

precise over a wide range of concentrations.

Linearity. The results of the XFM linearity evaluation are

presented on Table 10. These parameters were determined

with linear least-squares regression analysis of the XFMmeasured concentrations compared with the QAG-spiked

stack gas concentrations over all of the concentration

levels. XFM correlation coefficients for all elements were

0.99, well above the 0.85 acceptance value. Slopes for all

of the metals ranged from 1.04 to 1.07, all within 7% of

unity. Intercepts were all 3% of the linearity test concentration range and ranged from 	1.61 to 	2.72. A

plotted regression analysis for all 5 of the metals combined is presented for the XFM in Figure 5. The combined

metal regression yielded a correlation coefficient of 0.996,

a slope within 5% of 1.00 (1.05  0.01), and an intercept

2% of the full concentration range (	1.96  0.6). The

strong correlation of the XFM concentrations with the

reference concentrations demonstrates the ability of the

XFM to accurately measure a wide range of concentrations and confirms its precision over this range.

Summary

A summary of each method’s performance in reference to

the validation criteria is presented in Table 11. This table Figure 4. Xact linearity using all five elements.

Table 7. Xact linearity determined during field tests.

Element N R Slope SD Intercept SD

Cr 192 0.997 0.951 0.00505 	1.08 0.297

As 192 0.998 0.982 0.00487 	0.994 0.287

Hg 192 0.998 0.869 0.00412 	0.788 0.243

Pb 192 0.999 1.02 0.00387 	1.09 0.220

Cd 192 0.997 0.970 0.00573 	0.802 0.337

Notes: SD  standard deviation.

Table 10. XFM linearity determined during field tests.

Element N R Slope SD Intercept SD

Cr 24 0.997 1.04 0.0174 	1.61 1.39

As 24 0.997 1.07 0.0180 	2.72 1.43

Hg 24 0.996 1.04 0.0209 	1.80 1.67

Pb 24 0.995 1.07 0.0221 	2.08 1.81

Cd 24 0.997 1.05 0.0171 	1.61 1.36

Notes: SD  standard deviation.

Table 8. XFM accuracy determined during field tests.

Element

Low Concentration

(20 g/dscm)

Mid Concentration

(45 g/dscm)

High Concentration

(110 g/dscm) Average All Runs

N Accuracy Ai % SD N Accuracy Ai % SD N Accuracy Ai % SD N Accuracy Ai % SD

Cr 4 6.0 3.4 4 12 1.3 12 4.0 2.4 20 6.0 3.9

As 4 1.7 1.0 4 13 2.5 12 5.0 2.9 20 6.0 4.7

Hg 4 5.5 3.4 4 15 3.8 12 3.5 3.4 20 6.1 5.5

Pb 4 8.0 6.4 4 14 2.3 12 5.8 4.0 20 7.9 5.2

Cd 4 6.7 2.0 4 9.0 2.5 12 5.1 2.5 20 6.2 2.8

Notes: SD  standard deviation.

Table 9. XFM precision determined during field tests.

Element

Low Concentration

(20 g/dscm)

Mid Concentration

( 45 g/dscm)

High Concentration

(110 g/dscm) Average All Runs

N Precision Pi % N Precision Pi % N Precision Pi % N Precision Pi %

Cr 4 2.3 4 1.0 12 2.2 20 1.8

As 4 1.5 4 2.0 12 1.9 20 1.8

Hg 4 2.3 4 3.2 12 2.9 20 2.8

Pb 4 6.5 4 1.9 12 2.7 20 3.7

Cd 4 4.7 4 2.0 12 2.4 20 3.0

Yanca et al.

1740 Journal of the Air & Waste Management Association Volume 56 December 2006
clearly shows that the three methods easily passed all of

the required criteria for all five of the metals.

CONCLUSIONS

The three independent methods discussed in this paper

met EPA Method 301 requirements for compliance applications and are precise, accurate, and linear tools applicable to the determination of hazardous metal concentrations in emissions. The QAG and the Xact technologies

have currently been approved by EPA for compliance

demonstration at a HWC.26 In addition to the five elements measured with these tests, the methods are expected to be applicable to most hazardous elements in

stack and fugitive emissions from stationary sources, as

well as in the ambient environment. The QAG reference

aerosol generator could, thus, be used as a generally applicable reference aerosol generator for research, method

certification, and audits. The XFM measurement methods

could be used for performance testing, initial certification,

and continuing quality assurance audits of multimetal

CEMS. Finally, the Xact could be used to demonstrate

ongoing compliance through its use as a CEMS, and its

technology could be extended to an instrumental analysis

procedure with applications similar to the XFM.

In addition to the results presented in this paper, all

three methods have demonstrated high precisions and

accuracies in other field and laboratory tests.27–30 The

measurement methods have also consistently demonstrated frequent sampling times, rapid analysis turnaround times (15 min for the Xact and 2 hr for the XFM

if a field-portable analyzer is used), and low detection

limits. Analysis is nondestructive, and the methods can be

independently audited with the QAG. In addition to metals, the QAG can potentially generate aerosols of both

organic and inorganic analytes.

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Concentration of Metals in Eli Lilly and Company’s Hazardous Waste

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J.A.; Johnsen, B.J.; Lambert, R. H. Aerosol Sci. Tech., submitted for

publication.

17. Determination of Metal Concentration in CES’ Xact CEMS Stilling Chamber

Using the CES XFM; Cooper Environmental Services: Portland, OR,

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CES XFM; Cooper Environmental Services: Portland, OR, 2006.

19. Specifications and Test Procedure for X-Ray Fluorescence Based MultiMetals Continuous Emissions Monitoring Systems at Stationary Sources;

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20. Quality Assurance Requirements for X-Ray Fluorescence Based Multi-Metals

Continuous Emissions Monitoring Systems at Stationary Sources; Cooper

Environmental Services: Portland, OR, 2006.

21. Cooper, J.A.; Barth, D.B.; Nakanishi, M.P.; Petterson, K.A.; Yanca, C.A.

A Quantitative, Traceable-to-NIST, Reference Aerosol Generator for

Evaluating Aerosol Speciation Monitors and Measurement Methods.

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New Filter-Based Methods for Precise, Accurate, and Timelier Measurement of Metal Emissions. In Proceedings of the Air & Waste Management

Figure 5. XFM linearity using all five elements.

Table 11. Summary of validation results.

Parameters Criteria QAG Method XFM Method Xact Method

No. of runs (n) 9 20 12 24

Accuracy (A) 20% 5% 6%a 7%a,b

Precision (P) 10% 3% 4% 4%

Linearity (r) 0.85 0.99 0.99 0.99

Notes: aResults from high concentration level; bAssuming correct calibration

of Hg.

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Volume 56 December 2006 Journal of the Air & Waste Management Association 1741
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About the Authors

Catherine Yanca, Douglas Barth, Krag Petterson, and Michael Nakanishi are environmental scientists at Cooper Environmental Services, LLC. John Cooper is the president of

Cooper Environmental Services, LLC. Bruce Johnsen is a

claims adjuster at SAIF Co. Richard Lambert is an engineering consultant at the Engineering Tech Center, Eli Lilly

and Co. Daniel Bivins is the work assignment manager for

the Emission Measurement Center of the Office of Air Quality Planning and Standards, U.S. Environmental Protection

Agency. Address correspondence to: John Cooper, Cooper

Environmental Services, LLC, 10180 SW Nimbus Ave., Suite

J6, Portland, OR 97223; phone: 
1-503-624-5750; fax: 
1-

503-624-2120; e-mail: jacooper@cooperenvironmental.com.

Yanca et al.

1742 Journal of the Air & Waste Management Association Volume 56 December 2006