Method 301 Evaluation of Candidate Conditional 

Methods 

X-Ray Based Filter Method (XFM) 

Multi-Metals Instrumental Analyzer Procedure 

(Xact-IAP) 

Quantitative Reference Aerosol Generator (QAG) 

Prepared by: 

Cooper Environmental Services, LLC 

10180 SW Nimbus Blvd Suite J6 

Portland, Oregon 97223 

 Revision 1.0

June, 2005 

Executive Summary 

A new metal emissions measurement and validation system has recently been developed that 

has the potential to significantly improve our understanding of metal emissions from a wide 

range of source categories. This system consists of: 

• A continuous emission monitoring system (Xact-CEMS) 

• An instrumental analyzer procedure (Xact-IAP) 

• A sampling and analysis measurement method (XFM) 

• A NIST-traceable reference aerosol generator (QAG) 

The measurement components of this system are based on collecting a representative sample 

of stack gas on a chemically reactive filter (solid sorbent) that traps both particulate and 

vapor phases of metals, followed by non-destructive X-ray fluorescence (XRF) analysis 

using procedures consistent with ambient measurements. This system is applicable to 

elements with atomic number ranging from 13 (Al) to 92 (U), and can measure Be after nondestructive XRF analysis if other analytical procedures are used; it can provide detection 

limits as low as 0.1 μg/dscm with 15 minute turn around times or lower detection limits with 

longer sampling and analysis times; and has demonstrated accuracies better than five percent 

and precisions better than three percent. These generation and measurement components are 

independently traceable to NIST: the QAG through procedural traceability and solution 

standards, while the measurement methods are analytically traceable through thin film 

standards and NIST standard reference materials. 

A series of laboratory and field tests have been conducted to demonstrate that the QAG, 

XFM and Xact-IAP components of this new system meet Method 301 accuracy and precision 

requirements for conditional method status. Each of the methods met the performance 

criteria outlined in the Method 301 test plan. These criteria included the following: 

• Filter ratios – percent of Cr and Pb trapped on the XFM front PTFE filter. Although 

this criterion is not required by Method 301, high percentages assure high particle 

trapping efficiency. 

• Metal ratios - ratio of Pb-normalized solution concentration to Pb-normalized 

aerosol concentration. This criterion is also not required by Method 3011 but ratios 

close to one assure high relative generation, transport and sampling efficiencies for all 

metals including vapors. 

• Efficiency – percent of NIST-traceable reference aerosol concentration measured. A 

high percentage assures high absolute generation, transport and sampling efficiencies.

• Bias correction factor –ratio of reference to measured aerosol concentration. A 

value close to one indicates high method accuracy. 

• Precision – percent relative standard deviation determined from sequential 

measurements. A low percent value indicates a highly precise and stable system. 

• Linearity – correlation coefficient (r) based on a regression analysis of a plot of 

measured versus reference aerosol concentration. 

Method 301 Eval.: V1.0 Page i of xii
These criteria and their acceptance values are based primarily on those in Method 301 and 

were defined in the 301 validation test plan (Appendix A). During these tests, five elements 

(As, Cd, Cr, Pb, and Hg) were spiked at concentrations ranging from blank to about 120 

μg/dscm. All three (QAG, XFM, and Xact-IAP) independent approaches showed good 

agreement over this wide range of concentrations, and all three methods met the required 

criteria for all five metals. These results are summarized in the following three tables for the 

QAG reference aerosol generator, and the XFM and Xact-IAP measurement approaches. 

The Xact-IAP table includes results from all 192 Xact-IAP runs. 

Comparison of QAG laboratory results with criteria acceptance values. 

Criteria Acceptable Resultsa Met Criteria

No. Runs >9 >25 Yes

Filter Ratio (% Front) >98 >99 Yes

Metal Ratio (Sol./Aer.) 0.9 - 1.1 0.95 - 1.01 Yesb

Efficiency (%) >80 94 - 100 Yes

Precision (%) <10 <4 Yes

Linearity - Corr. Coef. ( r ) >0.85 >0.99 Yes aXFM and Xact results for all five elements

 bConfirmed with independent ICP analysis results

Comparison of XFM field test results with criteria acceptance values. 

Criteria Acceptable Resultsa Met Criteria

No. Runs >9 26 Yes

Bias Corr. Factor 0.80 - 1.2 0.94 - 0.97 Yesb

Precision (%) <10 <3 Yes

Linearity - Corr. Coef. ( r ) >0.85 >0.99 Yes a

XFM results for all five elements

b

Confirmed with independent ICP analysis results

Comparison of Xact-IAP field test results with criteria acceptance values. 

Criteria Acceptable Resultsa Met Criteria

No. Runs >9 192 Yes

Bias Corr. Factor 0.80 - 1.2 1.00 - 1.14 Yes

Precision (%) <10 <3 Yes

Linearity - Corr. Coef. ( r ) >0.85 >0.99 Yes a

Xact-IAP results for all five elements

Many more test runs than required by Method 301 were conducted, and all of the data from

these runs were included in this evaluation. The QAG and XFM tables shown below include 

results from all 26 XFM runs. 

The filter and metal ratios listed for the QAG are high and indicate that the relative 

generation, transport and sampling efficiencies for all elements are within the experimental 

accuracy of 100%. The efficiency, precision and linearity values for the QAG are also all 

well within the acceptable range. In the case of the XFM and Xact-IAP measurement 

Method 301 Eval.: V1.0 Page ii of xii
methods, all of the criteria were met and the values were substantially within the acceptable 

range, which in the case of the bias and precision were more restrictive in our test plan than 

required by Method 301. The high correlation coefficients indicate highly linear methods. 

This high degree of linearity is illustrated with the following four representative plots of the 

XFM and Xact-IAP measured values versus the independent QAG reference aerosol 

concentration during laboratory and field tests at a hazardous waste incinerator. 

MERCURY

y = 0.979x - 0.542

R2 = 0.993

0

50

100

150

0 50 100 150

QAG Conc (μg/dscm)

Xact Conc (μg/dscm)

n = 146

CADMIUM

y = 0.995x - 0.134

R2

 = 0.995

0

50

100

150

0 50 100 150

QAG Conc (μg/dscm)

XFM Conc (μg/dscm)

n=26

Representative scatter plots of XFM and Xact-IAP measured concentrations versus 

QAG reference aerosol concentrations during laboratory validation tests of the QAG. 

Lead

y = 0.991x - 1.924

R2

 = 0.992

0

50

100

150

0 50 100 150

QAG Conc. (μg/dscm)

Xact Conc. (μg/dscm)

n=192

Mercury

y = 1.036x - 1.803

R2

 = 0.991

0

50

100

150

0 50 100 150

QAG Conc. (μg/dscm)

XFM Conc. (μg/dscm)

n=24

Representative scatter plots of XFM and Xact-IAP measured concentrations versus 

QAG reference aerosol concentrations during field validation tests of the XFM and 

Xact-IAP. 

The XFM and Xact-IAP are rugged and robust methods that are applicable to a wide range of 

sources and elements. Because these methods include dilution sampling techniques, they are 

relatively insensitive to most stack gas characteristics (temperature, moisture, PM 

concentration, and chemistry) and can be optimized for specific stack conditions by adjusting 

dilution ratios, sampling times, etc... Their range of applicability has been demonstrated by 

results from these tests as well as other laboratory and field tests over the past five years 

including relative accuracy testing using both Method 292

and Ontario Hydro3 reference

methods. Examples of these field validation test results are illustrated with the following two 

figures. The plot of lead shows a strong linear relationship between the Xact and Method 29 

Method 301 Eval.: V1.0 Page iii of xii
results up to 2,200 μg/dscm and had a relative accuracy of 4%. The mercury plot shows a 

similar strong linear relationship between the XFM and Ontario Hydro reference method 

results at concentrations down to about 1 μg/dscm and had a relative accuracy of 11%. 

y = 1.058x - 5.786

R2

 = 1.000

0

500

1,000

1,500

2,000

2,500

0 500 1,000 1,500 2,000 2,500

M29 Conc. (μg/dscm)

Xact C

onc. (μg/dscm)

Lead

n=11

y = 0.908x + 0.152

R2

 = 0.962

0

1

2

3

4

5

6

0 246

OH Conc. (μg/dscm)

XFM Conc. (μg/d

s

c

m)

Mercury

n=9

Examples of field validation test results at a munitions incinerator4 (left) and at a coalfired utility boiler with baghouse and NOx controls5

 (right). 

These tests have included wet and dry incinerators, and wet and dry coal-fired utility boilers 

covering a range of controls including electrostatic precipitators, scrubbers and NOx catalytic 

reduction controls. The XFM and Xact-IAP are also consistent with ambient measurement 

methods6,7

and applicable to most of the elements typically measured in the ambient 

environment. Thus, the recommended range of source categories for which the XFM and 

Xact-IAP are applicable includes fugitive and ducted emissions such as those from

hazardous, municipal, sewage and other incinerators; cement and lime kilns; smelters and 

mills; mineral processing, plating and boiler sources using control technologies such as bag 

house filtration, electrostatic precipitation, scrubbers and NOx controls. 

Also, this technology offers the following additional advantages: 

• Significantly shorter reporting times (As short as 15 minutes compared to 3 weeks) 

• Precise (<3%), accurate (better than 5%), linear (r>0.99) and verifiable results due to 

non-destructive analysis 

• Minimal operator requirements 

• The methods are safe and easy to use and generate no hazardous waste. 

The results from these tests as well as results from previous field tests support the following 

conclusions. 

• The QAG candidate reference aerosol generator is independent of its application, met 

all of the required validation criteria, and should be approved as a NIST-traceable 

reference aerosol generator for compliance and other regulatory applications such as 

initial certification and continuing quality assurance audits of multi-metals CEMS as 

well as calibration and validation of metal measurement methods. 

Method 301 Eval.: V1.0 Page iv of xii
• The XFM and Xact-IAP candidate conditional methods for measuring metal 

concentrations in emissions from stationary sources met all of the required validation 

criteria; have demonstrated their applicability to a range of source types, controls and 

stack conditions; and should be approved for general compliance and other 

regulatory applications such as initial certification and continuing quality assurance 

audits of multi-metals CEMS, emission compliance audits, trial burns, and other 

regulatory applications where stack gas metal emission measurements from stationary 

sources are required. 

Method 301 Eval.: V1.0 Page v of xii
Table of Contents 

Executive Summary................................................................................................................. i

Appendices............................................................................................................................viii

List of Figures......................................................................................................................... ix

List of Abbreviations............................................................................................................. xi

1.0 Introduction.................................................................................................................... 1

What is this report about? ................................................................................................... 1 

Why are we concerned about metal emissions? ................................................................. 1 

Why is the current metals measurement system inadequate?............................................. 1 

What is this new metals measurement system? .................................................................. 2 

What are these candidate conditional methods? ................................................................. 2 

Why are the XFM and Xact-IAP candidate methods more appropriate than Method 29?. 2

Why are these methods important to the EPA and other stakeholders? ............................. 3 

How was the performance of these methods evaluated? .................................................... 3 

Where are the results presented in this report? ................................................................... 3 

2.0 Approach ........................................................................................................................ 3

2.1 Overview.................................................................................................................... 3 

2.2 General Approach ...................................................................................................... 4 

2.3 Method Independence................................................................................................ 5 

2.4 QAG Validation (Phase I).......................................................................................... 7 

2.5 XFM and Xact-IAP Validation (Phase II)............................................................... 11 

2.6 Deviations from Test Plan ....................................................................................... 12 

3.0 Methods......................................................................................................................... 14

3.1 QAG Reference Aerosol Generator......................................................................... 14 

3.2 XFM Candidate Conditional Method ...................................................................... 18 

3.3 Xact Instrumental Analyzer Procedure.................................................................... 21 

4.0 Calculations.................................................................................................................. 24

4.1 Overview.................................................................................................................. 24 

4.2 List of Symbols and Terms...................................................................................... 24 

4.3 QAG Reference Aerosol Concentration .................................................................. 26 

4.4 XFM Measured Aerosol Concentration................................................................... 27 

4.5 Xact-IAP Measured Aerosol Concentration ............................................................ 28 

Method 301 Eval.: V1.0 Page vi of xii
4.6 Validation Comparison Parameters......................................................................... 28 

4.7 Other Comparison Parameters................................................................................. 33 

5.0 Quality Control and Assurance .................................................................................. 35

5.1 Overview.................................................................................................................. 35 

5.2 QAG......................................................................................................................... 35 

5.3 XFM......................................................................................................................... 37 

5.4 Xact-IAP .................................................................................................................. 38 

6.0 Results and Discussion................................................................................................. 40

6.1 Overview.................................................................................................................. 40 

6.2 QAG Validation....................................................................................................... 40 

6.3 XFM and Xact-IAP Validation Overview............................................................... 48 

6.4 XFM Validation....................................................................................................... 50 

6.5 Xact-IAP Validation ................................................................................................ 52 

7.0 Range of Method Application..................................................................................... 55

7.1 Overview.................................................................................................................. 55 

7.2 Criteria for Candidate Method Applicability........................................................... 56 

7.3 Key Sampling and Analysis Features...................................................................... 56 

7.4 Key Emission Characteristics.................................................................................. 57 

7.5 Filter Trapping Efficiency for Vapor Phase Metals................................................. 58 

7.6 Applicable Concentration Range ............................................................................. 62 

7.7 Deposit Stability....................................................................................................... 62 

7.8 Moisture ................................................................................................................... 63 

7.9 Holding Times ......................................................................................................... 64 

7.10 Applicable Elements................................................................................................ 65 

7.11 Other Related Tests.................................................................................................. 65 

7.12 Applicable Source Categories.................................................................................. 66 

8.0 Conclusions and Recommendations........................................................................... 67

9.0 Glossary ........................................................................................................................ 68

10.0 References..................................................................................................................... 73

Method 301 Eval.: V1.0 Page vii of xii
Appendices 

Appendix A: Draft Test Plan for Validating a Reference Procedure for Measuring 

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

Waste Incinerator Stack Gas 

Appendix B: Determination of Metal Emissions from Stationary Sources Using 

Filters and Solid Sorbents with X-Ray Fluorescence Analysis 

Appendix C: Standard Operating Procedure for Generating a Quantitative MultiMetals Reference Aerosol with the CES QAG 

Appendix D: Determination of Metal Concentrations in Emissions from Stationary 

Sources (Instrumental Analyzer Procedure)

Appendix E: Performance Specifications for a Quantitative Reference Aerosol 

Generator

Appendix F: Specifications and Test Procedure for X-Ray Fluorescence Based 

Multi-Metals Continuous Emissions Monitoring Systems at Stationary 

Sources 

Quality Assurance Requirements for X-Ray Fluorescence Based 

Multi-Metals Continuous Emissions Monitoring Systems at Stationary 

Sources 

Appendix G: QA Information during Phase I 

Appendix H: QA Information during Phase II 

Appendix I: Phase I Test Data 

Appendix J: Phase II Test Data 

Appendix K Calculations Used for Method 301 Validation Tests 

Appendix L: Additional Data in Support of Service and Range Extension of 

Candidate Methods 

Appendix M: Related Reports Produced by Cooper Environmental Services 

Method 301 Eval.: V1.0 Page viii of xii
List of Figures 

Figure 1: Schematic flow diagram illustrating key aspects of the general validation 

procedure................................................................................................................................... 5 

Figure 2: Schematic representation of key components of CES’ reference aerosol generation 

system. ...................................................................................................................................... 6 

Figure 3: Flow diagram showing the experimental arrangement used to validate the QAG 

reference aerosol generator....................................................................................................... 8 

Figure 4: Schematic representation of the experimental arrangement used in Phase I to 

validate the QAG reference aerosol generator.......................................................................... 9 

Figure 5: A. Schematic of flow through QAG components. B. Overview of the set-up of 

QAG components.................................................................................................................... 15 

Figure 6: Schematic flow diagram of the sampling train used in Phase I and II XFM 

validation tests. ....................................................................................................................... 19 

Figure 7: Photograph of the assembled port adaptor, extraction assembly and filter holder.. 19 

Figure 8: Exploded schematic view of XFM filter holder with filter cassette........................ 21 

Figure 9: Overview of Xact-IAP components and flow schematic. ....................................... 23 

Figure 10: QAG solution mass loss rate during Phase I testing. ............................................ 36 

Figure 11: QAG solution mass loss rate during Phase II........................................................ 37 

Figure 12: QAG-generated and XFM- and Xact-IAP-measured aerosol concentrations during 

Phase I tests............................................................................................................................. 41 

Figure 13: Ratio of XFM and Xact-IAP measured metal concentrations to the QAG reference 

aerosol concentration. ............................................................................................................. 42 

Figure 14: Phase I QAG linearity plots as determined by the XFM....................................... 46 

Figure 15: Phase I QAG linearity plots as determined with the Xact-IAP............................. 47 

Figure 16: Comparison of the XFM and Xact-IAP measured concentrations with the QAGspiked flue gas concentrations during Phase II testing. .......................................................... 49 

Figure 17: Phase II XFM linearity.......................................................................................... 51 

Figure 18: Phase II Xact linearity. .......................................................................................... 54 

Figure 19. Comparison of Hg concentrations determined by XFM and Ontario Hydro 

reference method at a coal-fired power plant. ........................................................................ 60 

Figure 20 Plot of Xact-IAP concentration versus Reference Method 29 measured 

concentrations showing excellent agreement over two orders of magnitude and at 

concentrations in excess of 2,000 μg/dscm. ........................................................................... 62 

Figure 21. Plot of Pb concentrations determined by Reference Method 29 and the Xact...... 63 

Figure 22: Comparison of results from laboratory XRF analysis in July, 2002 with Xact field 

test results from May 2002 relative accuracy tests at a hazardous waste incinerator............. 63 

Method 301 Eval.: V1.0 Page ix of xii
List of Tables 

Table 1: Overview of Phase I validation test schedule........................................................... 10 

Table 2: Acceptance criteria for QAG.................................................................................... 11 

Table 3: Overview of Phase II validation test schedule.......................................................... 12 

Table 4: Acceptance criteria for Phase II validation of the XFM and Xact-IAP................... 12 

Table 5: Comparison of surrogate and Phase II flue gas characteristics. ............................... 14 

Table 6: QAG Emission Rates for Phase I and II. .................................................................. 36 

Table 7: Flowmeter evaluation during Phase I. ...................................................................... 38 

Table 8: Flowmeter evaluation during Phase II...................................................................... 38 

Table 9: Upscale and zero drift during Phase I testing. .......................................................... 39 

Table 10: Evaluation of NIST thin-film standards by the Xact-IAP. ..................................... 39 

Table 11: Upscale and zero drift during Phase II testing........................................................ 40 

Table 12: Comparison of Average QAG reference aerosol concentrations with XFM and 

Xact-IAP average measured concentrations (μg/dscm).......................................................... 42 

Table 13: Lead and chromium measured on the upstream PTFE filter as percent of total XFM 

lead and chromium (μg/filter)................................................................................................. 43 

Table 14: QAG efficiencies determined during Phase I laboratory tests (%)......................... 45 

Table 15: Summary of QAG Phase I precision (%). .............................................................. 45 

Table 16 Summary of Phase I QAG validation results........................................................... 47 

Table 17: Summary of XFM and Xact-IAP measured concentrations and QAG-spiked flue 

gas concentrations Phase II (μg/dscm). .................................................................................. 49 

Table 18: Summary of XFM Phase II bias values for each metal tested (μg/dscm). ............. 50 

Table 19: Summary of Phase II XFM validation test criteria and results............................... 51 

Table 20: Comparison of Xact-IAP with QAG reference concentrations and bias (μg/dscm).

................................................................................................................................................. 53 

Table 21: Summary of Phase II Xact results. ......................................................................... 54 

Table 22: Comparison of Xact Phase II results with proposed PS-10 criteria........................ 55 

Table 23. List of stack conditions for which Xact-IAP and XFM tests have been conducted58 

Table 24. List of test conditions and references used to evaluate method applicability......... 61 

Table 25: Recent tests of Xact and XFM on wet and dry stacks. ........................................... 64 

Table 26: Xact detection limits determined at Lilly’s T149 incinerator................................. 66 

Method 301 Eval.: V1.0 Page x of xii
List of Abbreviations 

μg/m3 Micro-grams per cubic meter 

As Arsenic 

Cd Cadmium

CEMS Continuous Emissions Monitoring System

CES Cooper Environmental Services LLC of Portland, OR

CFPP Coal Fired Power Plant. 

CFR Code of Federal Regulations. 

Cr Chromium

DAS Data Acquisition System 

DQO Data Quality Objectives 

DSCM Dry Standard Cubic Meters 

DSLP Dry Standard Liters Per Minute 

EPA United States Environmental Protection Agency 

Hg Mercury 

HWC Hazardous Waste Combustor 

IAAP Iowa Army Ammunition Plant 

IAP Instrumental analyzer procedure 

LVM Low Volatile Metals (arsenic, beryllium, chromium) 

M29 EPA Reference Method 29 

M301 EPA Reference Method 301 

MACT Maximum Achievable Control Technology 

MFC Mass Flow Controller 

MFM Mass Flow Meter 

MM-CEM Multi-metal Continuous Emission Monitor 

MRI Midwest Research Institute, Kansas City, MO 

Pb Lead 

PS10 EPA’s proposed Performance Standard 10 for multi-metal CEMS 

QA Quality Assurance 

QAG Quantitative Aerosol Generator 

QC Quality Control 

RA Relative Accuracy 

Method 301 Eval.: V1.0 Page xi of xii
RSD Relative Standard Deviation (% RSD equals precision) 

slpm Standard Liters Per Minute 

SVM Semi-volatile metals (cadmium, lead) 

TEAD Tooele Army Depot 

USACERL U.S. Army Construction Engineering Research Library 

VM Volatile Metals (mercury) 

XCEM X-ray based Continuous Emission Monitor 

XFM X-ray based Filter Method

XRF X-Ray Fluorescence 

Zn Zinc 

Method 301 Eval.: V1.0 Page xii of xii
1.0 Introduction

What is this report about? 

This report describes a new multi-metals measurement and validation system. It also

presents the results of tests demonstrating that each of the system components meet the U. S. 

Environmental Protection Agency (EPA) Method 301 criteria for conditional method status. 

The objectives of this report are to present and discuss these results in support of EPA’s 

evaluation of this system, and obtain EPA acceptance of its components as conditional 

methods. 

Why are we concerned about metal emissions? 

Air toxic metals have been associated with a wide range of environmental and human health 

effects including respiratory disorders, pulmonary disorders, and cancer. Recent findings link 

air toxic metals with in-vivo and in-vitro inflammatory responses8,9

. As such, there is 

continuing concern for potential health effects of metal air pollutants including such metals 

as Sb, As, Cd, Co, Cr, Hg, Mn, Ni, Pb, and Se. The EPA is required to control emissions of 

toxic and hazardous air pollutants under the Clean Air Act Amendments of 199010. Under 

Sections 112(k) and 112(c) of the Clean Air Act, the EPA is also required to monitor the 

ambient air concentrations of these species to evaluate the effectiveness of its reduction 

strategies. For these reasons, the EPA has developed an air toxics objective that includes an 

effort to reduce air toxic emissions and implement area specific control strategies to reduce 

air toxic exposures by 201011. However, our current understanding of metal emissions is 

relatively poor, primarily because our current measurement technology is inadequate. 

Why is the current metals measurement system inadequate? 

A metals emissions measurement system needs to be capable of meeting a range of practical 

requirements in addition to meeting such basic requirements as being accurate, precise, 

reliable and verifiable. Top among practical requirements is that the measurements should be 

timely and representative; that is the results need to be available within a time frame 

adequate for decisions (hours to days) and representative of long term emissions (months to 

years). However, the currently accepted reference measurement system consists of one 

method capable of only infrequent periodic measurements; i.e. EPA Reference Method 29 

(Method 29). 

This method is considered inadequate and inappropriate for current applications primarily 

because it is not a continuous emission monitoring system (CEMS) and therefore may not be 

adequately representative of long term average emissions; but also because of its long 

reporting times, which are typically on the order of several weeks or more. For example, to 

be effective as a quality assurance tool for CEMS validation or trial burn applications, a 

reference method must provide results within hours of the time of sampling or at least by the 

next day so as to allow time for adjustments prior to completing these tests. In addition, it is 

felt that for some metals Method 29 suffers from accuracy and precision limitations12, 13. 

Method 29 is also relatively difficult and dangerous to use, creates large quantities of 

Method 301 Eval.: V1.0 Section 1.0 Introduction Page of 40 1
hazardous waste, recovered samples are difficult to ship in a post-911 environment, and the 

method is costly. In addition, Method 29 is not consistent with current ambient metals 

measurements and as such more likely to have systematic biases relative to these ambient 

measurements. Because of the above noted limitations of Method 29, candidate alternative 

methods are being proposed. 

What is this new metals measurement system? 

The currently proposed metals measurement system consists of two candidate conditional 

measurement methods, a multi-metal CEMS and a quantitative reference aerosol generator. 

The multi-metals CEMS is not addressed in this report. 

What are these candidate conditional methods? 

The two candidate conditional methods are based on collection of representative samples of 

particle and vapor phase metals on a reactive filter followed by metal determination using Xray fluorescence (XRF) analysis. One is a method of collecting periodic samples by drawing 

stack gas through a series of filters contained in a sealed filter cassette. In this X-ray based 

filter method (XFM), particulate phase metals are trapped on a non-reactive filter while vapor 

phase metals including mercury are collected on a chemically reactive filter or solid sorbent. 

The concentration of metals in the resulting filter deposits are non-destructively determined, 

either in the field or laboratory using XRF analysis following analytical procedures similar to 

those listed in EPA’s Compendium Method IO-3.3 (“Determination of Metals in Ambient 

Particulate Matter Using X-Ray Fluorescence (XRF) Spectroscopy in Compendium of 

Methods for the Determination of Inorganic Compounds in Ambient Air, EPA/625/R96/010a, June 1999.)14. The stack gas concentration is calculated by dividing the XRFdetermined metal mass by the volume of stack gas that passed through the filters. The other 

measurement method is an instrumental analyzer procedure (IAP) based on the collection of 

a representative sample of particles and gas phase metals on a reactive filter tape followed by 

determination of metals with XRF analysis (Xact-IAP). 

The other component in this system is a Quantitative Aerosol Generator (QAG). The QAG 

generates a NIST-traceable reference aerosol that can be used, in addition to its other 

applications, to challenge and evaluate the accuracy, precision and linearity of the 

measurement methods and is applicable to non-metal species as well as metal species. 

Why are the XFM and Xact-IAP candidate methods more appropriate than Method 29? 

These candidate methods are more appropriate than Method 29 primarily because of their 

rapid analysis turn around times, which can be as short as 15 minutes in the case of the XactIAP or two hours in the case of the XFM if a field-portable XRF analyzer is used. Not only 

do these methods meet the required turn around times, but they also provide better precision 

and accuracy than Method 29 as the results reported in this document demonstrate, and their 

results can be independently verified because the analysis is non-destructive. In addition, the 

methods provide lower detection limits, require fewer resources, are safe and easy to use, 

generate no hazardous waste and are based on well-established EPA analysis procedures that 

are consistent with EPA ambient measurement methods. 

Method 301 Eval.: V1.0 Section 1.0 Introduction Page of 40 2
Why are these methods important to the EPA and other stakeholders? 

We currently have a poor understanding of metals emitted from the country’s smoke stacks 

because of the absence of metals CEMS, infrequent manual method measurements, and 

substantial uncertainty in how well these measurements represent emissions, operating 

conditions and assumptions. The XFM, Xact-IAP, and QAG candidate conditional methods 

offer the EPA more convenient and reliable tools for measuring and validating metal 

emissions. This should make it easier for plant operators to make more frequent 

measurements, which will provide the EPA and other stakeholders with a higher level of 

understanding of metal emissions. In addition, this technology should make it easier to test 

and evaluate new measurement and control technologies by reducing cost barriers and by 

providing more timely results for engineering evaluation and adjustments. Also, more timely 

results provided by these candidate methods during such tests as trial burns will reduce the 

need for repeating these tests due to extensive delays in receiving Method 29 results, which 

are typically not available until after the completion of such tests. 

How was the performance of these methods evaluated? 

A two phased approach was used to evaluate and validate the aerosol generator and the filter 

based measurement methods. Phase I was a laboratory study in which the accuracy, 

precision and linearity of the QAG was established and ruggedness test data developed for 

the XFM and Xact-IAP. Phase II was a field study conducted to validate the measurement 

methods for applications to stack gases. In Phase II, the validated QAG was used to generate 

a reference aerosol that was spiked into stack gas, which was subsequently measured with the 

XFM and the Xact-IAP. All of the valid data generated during these tests were used in these 

method evaluations, and far more measurements were taken than required by Method 301. 

That is, no valid results were excluded in our analysis, even though a substantial number of 

results could have been omitted while still meeting Method 301 requirements. 

Is this system applicable to other sources and elements? 

This system is applicable to most emissions from stationary sources and all of the hazardous 

elements as well as all of the elements measured in the ambient environment; including Be if

it is measured with other analytical methods after non-destructive XRF analysis. 

Where are the results presented in this report? 

This report presents a summary and discussion of the methods used and test results. The 

details of the methods and results are presented in the appendices of this report along with 

field data sheets, NIST-traceable certifications, sample calculations, all unprocessed data, etc. 

2.0 Approach 

2.1 Overview 

The primary objectives of these tests were to validate the QAG as a reference aerosol 

generator and obtain EPA conditional method acceptance for the XFM and Xact-IAP. The 

Method 301 Eval.: V1.0 Section 1.0 Introduction Page of 40 3
objective of this section is to describe the general approach used to generate the supporting 

data, and discuss how this approach compares to EPA Method 301 requirements and the 

approach proposed in CES’ test plan (Appendix A). 

2.2 General Approach 

Neither an appropriate reference method nor performance audit materials were available to 

evaluate the candidate conditional methods. As such, a new approach was required to 

demonstrate the precision and accuracy capabilities of the candidate methods. Although 

there are numerous standard EPA analytical protocols available that are NIST-traceable, the 

real limitation was in the sample collection part of the sampling and analysis procedure. A 

key sampling issue in this case was the need to verify sample collection efficiencies to a 

precision and accuracy consistent with the potential precision (<5%) and accuracy (<5%) 

believed to be attainable with the candidate methods. 

A two-phased approach was used in this case as schematically illustrated in Figure 1. The 

first phase (Phase I) consisted of laboratory validation of CES’ QAG, while Phase II was a 

field evaluation test of the XFM and Xact-IAP using a reference aerosol generated by the 

validated QAG. The first step was the development of a QAG capable of emitting a

reference aerosol, which could then be validated in the laboratory using independent NISTtraceable aerosol concentration measurements (Phase I). The QAG, thus validated in the 

laboratory, was then used in the field to spike stack gas with a reference aerosol of NISTtraceable concentration to challenge the candidate conditional measurement methods (Phase 

II). The success of this approach depended on several key factors including: 

• Independence of the NIST-traceable aerosol generation process and the NISTtraceable aerosol measurement methods. 

• High level of precision for both the generator and the analytical method (about 2%). 

• The resulting small bias between the generator and analytical method (<5%). 

• The magnitude of the bias being on the same order of magnitude as the expected 

uncertainty in the bias established through propagation of errors in both the generator 

and analytical measurements. 

Although under these conditions, the “true” concentration of the generated aerosol was 

“unknown”, its concentration was known at least to an accuracy comparable to the degree of 

propagated error and independent method agreement or magnitude of the bias; i.e., <5%, 

which is significantly better than the existing metals reference method. The resulting QAG 

could thus be used in the field with a high level of confidence that the generated reference 

aerosol concentration was NIST-traceable to an accuracy of 5% or better. 

The general validation procedure used is illustrated in the schematic flow diagram shown in 

Figure 1. As noted above, a key component of this validation procedure was the fact that the 

QAG not only generated an accurate, NIST-traceable aerosol of known composition, but the 

composition of the generated aerosol was stable over periods of several days as documented 

with the Xact-IAP and XFM performance during evaluation testing. This documented 

Method 301 Eval.: V1.0 Section 2.0 Approach Page 4 of 40 
aerosol stability allowed the determination of precision through the collection of replicate 

sequential samples instead of collection of simultaneous samples using dual sampling trains. 

Phase I

CES Laboratory

Air

Phase II

Lilly Stack Gas

CES AEROSOL

GENERATION SYSTEM

 High Accuracy

 High Precision

 High Long term Stability

 Measured Precision and

Stability

Xact XFM

Figure 1: Schematic flow diagram illustrating key aspects of the general validation 

procedure. 

2.3 Method Independence 

Independence of the aerosol generation and measurement methods is essential to the 

approach used to validate the QAG and subsequently the XFM and Xact-IAP. This method 

independence is schematically illustrated in Figure 2. As illustrated in this figure, the QAG 

generated aerosol concentration is traceable to NIST (Appendix C). In this case, all 

parameters used in the calculation of the aerosol concentration are NIST-traceable including 

the concentration of the standard solution and the rate of solution use. 

Method 301 Eval.: V1.0 Section 2.0 Approach Page 5 of 40 
Figure 2: Schematic representation of key components of CES’ reference aerosol 

generation system. 

The aerosol generation process was evaluated with independent filter samples of the aerosol 

collected by the XFM and Xact-IAP, which were subsequently analyzed by XRF using two 

separate X-ray spectrometers. (Appendices B and D) The XFM and Xact-IAP parameters 

used to determine the volume of aerosol sampled are NIST traceable. (Appendix G) In 

addition, the XRF parameters used to determine the mass of metal in the filter deposit are 

traceable to NIST (NIST SRM 1832 and 1833, and gravimetrically NIST traceable thin film

standards) and are independent of the aerosol generation process. These generation and 

measurement methods are clearly independent. Although further traceability or confirming 

measurements should not be required, additional measurements and routes to traceability 

were established through independent laboratory inductively coupled plasma analysis (ICP) 

of solution and filter samples as illustrated in the lower portion of the schematic illustration 

shown in Figure 2. The resulting independent laboratory-determined elemental 

concentrations and elemental ratios confirmed the standard solution concentrations used in 

Method 301 Eval.: V1.0 Section 2.0 Approach Page 6 of 40 
the QAG. In addition, selected XFM filter samples were analyzed by ICP using an 

independent laboratory to confirm the metal deposit measurements made by the XRF 

analyzer. These independent, third party measurements were also used to confirm the 

elemental concentrations, their ratios and their NIST traceability (See Appendix G). It 

should also be noted that the XRF analyzer used to analyze the XFM filter samples was also 

used in an earlier EPA PM2.5 speciation program in which numerous “round robin” type of 

quality assurance tests were conducted and demonstrated comparable results to two other 

independent laboratories15. Thus, not only are the aerosol generation and measurement 

methods clearly independent, but there is a reasonable degree of independent quality 

assurance between the XFM and Xact measurement methods. In addition, since two 

different Xacts were used in Phase I and Phase II testing (CES and Lilly Xacts) requiring two 

different calibrations, there is a reasonable degree of independence of these two sets of Xact 

measurements. As a result, when there is a high degree of agreement between the generated 

aerosol concentration and the measured concentration, accuracy of both the generator and 

measurement methods are simultaneously validated within the degree of agreement because 

of the independence of their NIST traceability. 

The test procedures used for this validation report were more rigorous and demanding than 

the procedures described in EPA Method 301. For example, the Method 301-based 

evaluation procedures used here include additional linearity requirements as well as the 

Method 301 precision and bias requirements. In addition, substantially more measurements 

were made than were required and none of the valid data was excluded from the data 

analysis. Also, because of the multi-elemental nature of the measurements, inter-elemental 

ratio requirements were added to acceptability criteria. 

2.4 QAG Validation (Phase I) 

The experimental arrangement used to validate the QAG during Phase I testing is illustrated 

in the flow diagrams in Figure 3 and Figure 4 (Details of the test and QAG are discussed in 

Appendices A and C). The QAG components are illustrated on the right side of Figure 4. It 

consists of a Collison-type nebulizer16 maintained at 0°F to minimize water vapor loss from

the NIST-traceable spike solution during nebulization and vapor-droplet equilibration. The 

spiking solution was circulated through a large solution reservoir to minimize the impact on 

solution concentration due to loss of water from evaporation. The rate of QAG metal 

emissions was determined by measuring the solution use rate in grams per minute as 

determined by a NIST-traceable balance and correcting for vapor loss. The resulting 

nebulizer-produced aerosol (about 15 lpm) passed into a settling chamber where liquid 

droplets greater than about 20 μm in diameter settled out of the gas flow and were returned to 

the solution reservoir. The resulting size-selected aerosol was then injected into a drying 

chamber maintained at about 300 °F where it was dried and diluted with about 30 to 50 lpm

of clean, dry laboratory air. The dry salt and metal vapor containing aerosol emerging from

the QAG was diluted further with about 20 to 40 lpm of make-up air. The reference aerosol 

total flow was about 100 to 120 lpm, and was monitored with a NIST-traceable mass flow 

meter.

Method 301 Eval.: V1.0 Section 2.0 Approach Page 7 of 40 
Figure 3: Flow diagram showing the experimental arrangement used to validate the 

QAG reference aerosol generator. 

The QAG-generated reference aerosol contained five metals, (As, Cd, Cr, Pb, and Hg) 

representing the volatile, semi-volatile and low volatility metal categories as defined in the 

Hazardous Waste Combustor (HWC) Maximum Achievable Control Technology (MACT) 

rule17. Aerosol concentrations ranged from 20 to more than 120 μg/dscm, spanning the range 

of their MACT emission limits. This reference aerosol was directed from the QAG to the top 

of the Xact stilling chamber through 2-inch diameter stainless steel (SS) tubing. About 99% 

of the flow passed through the test apparatus and was filtered prior to flow measurement. 

Less than 1% of the reference aerosol was sampled from the stilling chamber by the XactIAP (about 0.7 slpm). During XFM testing, almost 40% of the sample flow was drawn 

through the XFM plenum and returned to the exhaust downstream of the stilling chamber. 

From this subflow, about 1 lpm of the reference aerosol was sampled and drawn through the 

Method 301 Eval.: V1.0 Section 2.0 Approach Page 8 of 40 
Figure 4: Schematic representation of the experimental arrangement used in Phase I to 

validate the QAG reference aerosol generator.

XFM filter cassette. The resulting XFM filters were analyzed by XRF using EPA 

Compendium Method IO-3.3 for particle deposits on filters while the CES Xact-IAP 

automatically reported metal concentrations every 15 minutes for the duration of the test. 

Typical test periods consisted of establishing a stable reference aerosol flow through the 

Xact-IAP stilling chamber and out the exhaust manifold. The concentration of this reference 

aerosol was stable to within a few percent during each series of test runs as demonstrated by 

the Xact and QAG combined precision, which was typically on the order of 2 to 4 %. The 

aerosol metal concentration in the stilling chamber was simultaneously sampled and 

measured by both the Xact and XFM, which provided independent confirmation of the QAG 

reference aerosol concentrations. During linearity evaluation tests, the aerosol concentration 

was increased or decreased by changing the spiking solution concentration. 

Phase I validation testing of the QAG was conducted at CES’ laboratory using spiked 

ambient air. During these tests, the QAG spiked five MACT metals (As. Cd, Cr, Pb and Hg) 

at five concentration levels, including a series of blank runs, which were then compared to 

the measured concentrations reported by the CES Xact-IAP and the XFM. During Phase I, a 

total of 26 XFM and 148 Xact runs were compared to the QAG reference concentrations 

(Table 1). 

Method 301 Eval.: V1.0 Section 2.0 Approach Page 9 of 40 
Table 1: Summary of QAG validation test schedule. 

Nominal 

Date QAG Conc. 

Nominal 

Level for 

MACT 

Metal μg/dscm 

No. of 

XFM 

Runs 

No of Xact 

Runs 

Dec. 14-15, 2004 Mid2 65 12 93 

Dec. 16, 2004 Mid1 50 4 13 

Dec. 16, 2004 Low 20 4 12 

Dec. 16, 2004 High 130 4 11 

Dec. 17, 2004 Blank 0 2 19 

Total Runs 26 148 

The validation metrics or criteria used to establish the validity of the QAG are listed below: 

• Transport Efficiency: The calculated transport efficiency shall be greater than 80% 

for all elements. Since the NIST-traceable reference aerosol concentration is totally

independent from the NIST-traceable filter sampling and analysis method, this

criterion, if met, might be considered adequate to establish an acceptable efficiency 

correction factor for the QAG. 

• Lead and Cr Filter Ratios: To ensure that the filters had adequate particulate 

trapping efficiency, less than two percent of the Pb and Cr were permitted on the 

XFM reactive filter downstream of the PTFE filter. This plus the assumed low 

volatility of these elements will assure a near 100% sample train trapping efficiency 

for these elements. This criterion plus the following criterion provide additional 

assurance that the trapping efficiencies for all of the elements are near 100%. 

• Elemental Ratios: As, Cd, Cr, and Hg concentration ratios to lead measured in the 

aerosol sample must be within ±10% of the concentration ratios in the QAG solution. 

Meeting this criterion assures not only high trapping efficiencies but also high 

generation and transport efficiencies for all of the elements including volatile 

elements. 

• Precision: The QAG must have a precision, as measured by percent relative standard 

deviation (PRSD), of less than 10% for each of the elements. This high precision 

criterion will enable sequential sampling of the candidate methods at each 

concentration level. 

• Linearity: The QAG and both candidate filter-based conditional methods shall have 

a correlation coefficient (r) that is greater than 0.85. This criterion shows that the 

QAG is linear over a wide range of concentrations. 

These criteria and their acceptable ranges are summarized in Table 2. 

Method 301 Eval.: V1.0 Section 2.0 Approach Page 10 of 40 
Table 2: Acceptance criteria for QAG. 

Criteria Measure No. Runs Acceptable Range 

Filter Ratio back to front ratio (Cr, PB) >9 <0.02 

Metal Ratio solution to aerosol ratio >9 0.9 to 1.1

t-statistic >9 < critical value or

Efficiency efficiency factor >9 Between 0.8 and 1.0

Precision percent of spiked conc. >9 <10%

Linearity correlation coefficient >9 > 0.85

hese criteria include required bias (efficiency) and precision validation parameters from

ors

her

2.5 XFM and Xact-IAP Validation (Phase II) 

The primary objective of Phase II testing was to validate the XFM and Xact-IAP while 

y

Following Phase I testing, the QAG was installed at a hazardous waste incinerator18 and a 

s

I

IAP

T

Method 301 (bias or in this case efficiency and precision) and additional validation indicat

relevant to these specific tests: i.e., filter ratio, metal ratio and linearity criteria. The 

acceptability ranges listed in Table 2 were guided by values required by Method 301,

Performance Specifications 11 and proposed Performance Specification 10, and are eit

equal to those listed in these procedures or are more restrictive. 

sampling flue gas. The validity of these sampling and analysis methods was evaluated b

comparing the Phase I validated QAG reference aerosol concentration with the XFM and 

Xact-IAP measured concentrations. It is important to note that a different Xact instrument

was used in Phase II than was used in Phase I. 

series of validation tests were conducted. During these tests, the QAG reference aerosol wa

spiked into incinerator flue gas at four different concentration levels while an XFM sampling

train and Xact-IAP were collecting simultaneous samples from the Xact stilling chamber. 

The experimental arrangement was similar to that used in the laboratory with the primary 

difference that the reference aerosol was spiked into stack gas instead of laboratory air. In

addition, the Xact used in these field tests was different from the one used during the Phase

tests at CES’ laboratory. During Phase II, the QAG spiked five MACT metals at four 

concentration levels (Table 3) into about 35 slpm of flue gas while the XFM and Xactconcurrently sampled the reference aerosol spiked stack gas. A total of 24 XFM and 192 

Xact-IAP runs were completed during Phase II tests while the QAG was operating. 

Method 301 Eval.: V1.0 Section 2.0 Approach Page 11 of 40 
Table 3: Overview of Phase II validation test schedule. 

Nominal QAG 

Date Conc. 

Nominal 

Level 

μg/dscm 

No. of XFM 

Runs 

No of Xact

Runs 

March 4-5, 2005 High 108 12 45 

March 6, 2005 Low 21 4 46 

March 7, 2005 Mid 45 4 37 

March 8, 2005 Blank 0 4 64 

Total Runs 24 192 

Validation criteria used to evaluate the acceptance of the XFM and Xact-IAP were similar to 

those used for the QAG in Phase I and are listed in Table 4. These criteria include bias, 

precision and linearity of the measurement methods. The main difference was the omission 

of the filter and elemental ratio criteria, which were not relevant to Phase II testing. As was 

the case in Phase I, the acceptability ranges listed in Table 4 were guided by values required 

by Method 301, Performance Specifications 1118 and proposed Performance Specification 

1020, and are either equal to those listed in these procedures or are more restrictive. 

Table 4: Acceptance criteria for Phase II validation of the XFM and Xact-IAP. 

Criteria Measure No.

Measurements 

Acceptable Range 

t-statistic >9 < critical value or Bias correction factor >9 Between 0.8 and 1.2 

Precision percent of emission limit >9 <10% 

Linearity correlation coefficient >9 > 0.85 

2.6 Deviations from Test Plan 

The original draft Test Plan was developed in the fall of 2004 to organize validation testing 

of the XFM and can be found in Appendix A. During actual testing, there were five 

significant deviations from this test plan. Why these deviations occurred and any potential 

impacts to the resulting data set are discussed below. 

• Evaluation of the Xact-IAP: The test plan proposed an approach for validating the 

QAG and XFM, but it did not focus on the Xact-IAP as a separate Instrumental 

Analyzer Procedure. Following discussions with the EPA, the scope of the test was 

expanded to include the Xact-IAP, following the same validation criteria as the XFM.

Both the XFM and the Xact-IAP are candidate conditional methods, but the Xact-IAP 

offers end-users more immediate feedback. For this reason, and since the same QAG 

data set could be applied to both approaches, the test plan was expanded to include 

validation procedures for the Xact-IAP. 

• Total Capture: The original test plan proposed using a total capture approach to 

validate the QAG in Phase I. The total capture approach, however, was technically 

Method 301 Eval.: V1.0 Section 2.0 Approach Page 12 of 40 
problematic and was not used during the validation tests. Instead, the approach used 

was based on independent measurements of the resulting QAG generated aerosol 

concentration as described above. 

• Blank Runs: The original test plan called for injection of water for blank runs to 

determine XFM detection limits. During the course of testing, it was determined that 

pure water would freeze in the QAG. For this reason, blank 5% nitric acid was spiked 

instead of water. These blank tests were conducted during both Phase I (five hours) 

and II (eight hours). This blank testing resulted in six XFM and about 100 Xact blank 

test runs. Although all five metals reported blank concentrations of less than one 

μg/dscm for the XFM and the Xact-IAP, actual detection limits were calculated using 

a much larger data set (Appendix K) and then compared to the blank runs as 

discussed in Section 7.11.2. 

• Precision: The precisions measured for the QAG, XFM, and Xact-IAP were based on 

the PRSD of the measured metal concentrations when the QAG was spiking at a 

constant rate. The original test plan called for calculation of precision as a percent of 

the emission limit, and the results indicate that calculating precision in this manner 

would have met the test plan precision criteria of 10%. However, since a range of 

concentrations were used to determine linearity, a more demanding protocol using all 

of the data including the lowest spiked concentrations was used that divided the 

standard deviation at each concentration by the mean concentration at each spiked 

level. This latter approach is consistent with Method 301: Equation 301-622. 

• Flue Gas Composition: Phase II samples were collected when the incinerator was 

burning natural gas instead of waste. In the week prior to Phase II testing, cracks were 

observed in a section of incinerator piping that is exposed to pressures of more than 

1000 PSI. These cracks precluded the burning of waste during testing and, since it 

was a two to three month delay before the pipes could be repaired, it was decided to 

conduct the tests using natural gas rather than delay the tests. A comparison of the 

flue gas characteristics for Phase II tests relative to flue gas characteristics during 

surrogate feed stock burns conducted in the Fall of 2004 is shown in Table 5. In 

general, the incinerator emissions produced while burning natural gas in Phase II 

were very similar to those observed during the surrogate feed stock burns. Most major 

flue gas species such as SO2, H2O, CO, and CO2, were found in the same or higher 

concentrations during Phase II tests than in the surrogate feed stock burn tests in the 

fall of 2004. The primary difference was a decrease of 64% in particulate 

concentrations during Phase II tests. However, the impact of this parameter is 

insignificant at these concentrations (less than 10mg/dcsm @ 7% O2), and would not 

be significant unless it were well over the permitted PM emission limits.

Method 301 Eval.: V1.0 Section 2.0 Approach Page 13 of 40 
Table 5: Comparison of surrogate and Phase II flue gas characteristics. 

Chemical 

Species 

Surrogate Tests 

Fall 2004

Phase II 

March 2005

Phase II 

Surrogate Ratio

SO2, dry (ppm) ND ± ND ND ± ND ----------

HCl, dry (ppm) 2.3 ± 1.2 1.9 ± 0.6 0.8

CO2, dry (%) 8.3 ± 0.7 6.0 ± 0.1 0.7

CO, dry (ppm) 8.4 ± 1.9 13.8 ± 0.7 1.7

O2, dry (%) 9.1 ± 0.9 11.4 ± 0.1 1.3

H2O (%) 9.2 ± 3.3 10.1 ± 0.4 1.1

PM @ 7% O2

(mg/dscm) 9.8 ± 2.8 3.5 ± 0.4 0.4

NOx, dry (ppm) 40.5 ± 10.0 108.1 ± 5.5 2.7

Flow (dscfm) 14196 ± 1096 9952 ± 423 0.7

3.0 Methods 

3.1 QAG Reference Aerosol Generator 

The reference aerosol used in these tests was generated with CES’ quantitative aerosol 

generator (QAG). This aerosol was the primary reference source used to determine bias and 

precision capabilities of the candidate conditional multi-metals methods. The QAG provides 

a continuous reference aerosol whose analyte concentration is NIST-traceable with 

documented accuracy and precision. Once validated in the laboratory during Phase I testing, 

the QAG was used to spike incinerator stack gas in the field during Phase II testing. 

Although the QAG has the ability to generate a wide range of analyte-containing aerosols, 

the only type used in the experiments described in this report were metal containing aerosols. 

The QAG generates its reference aerosol using the following three basic steps: 

• First, an aerosol of analyte solution droplets is created using a nebulizer16. 

• This is followed by the separation and recirculation of large droplets using a settling 

chamber where the large droplets are removed while liquid and vapor phases are 

equilibrated. 

• The third step consists of drying droplets smaller than 20μm in diameter. 

Method 301 Eval.: V1.0 Section 3.0 Methods Page 14 of 40
The dried analyte-containing aerosol emission rate is calculated from the analyte 

concentration in the nebulized solution, the solution droplet emission rate, and the total 

volume of nebulizing, drying and dilution gas used to create the resulting aerosol. Use of 

nebulizers to generate quantitative aerosols is typically limited by three key factors: 

• The magnitude and uncertainty of the water vapor emission rate lost during droplet 

generation and equilibration 

• Changing solution concentration due to evaporation of solution 

• Generation of large droplets, which can represent a significant fraction of the emitted 

mass and could have low transport efficiency due to the large size of the resulting 

dried salt particles. 

These potential problems have been effectively either eliminated or minimized in the current

model of the QAG by (1) generating the droplet aerosol at 32° F using cooled water-saturated 

nebulizing air to minimize and quantify the evaporative component, (2) using a large solution 

reservoir to both minimize the impact of changing concentration due to evaporation and to 

allow for measurement of total solution use rate, and 3) incorporation of a stilling chamber to 

separate and recycle large solution droplets. 

Key QAG components are illustrated with the schematic drawings shown in Figure 5. 

 A. B. 

Figure 5: A. Schematic of flow through QAG components. B. Overview of the set-up of 

QAG components. 

Method 301 Eval.: V1.0 Section 3.0 Methods Page 15 of 40
There are six major components of the QAG: 

• A reference solution control component is used to circulate the analyte-containing 

solution through the nebulizer and measure the total solution use rate. This 

component consists of a peristaltic pump, solution reservoir, balance, connecting 

tubing and a laptop used to record the balance reading every 15 seconds. 

• A nebulizer air control component used to maintain and measure the flow, 

temperature, pressure and saturation of air used in the nebulization process. This 

component uses compressed air at about 20 PSI-gage pressure to force air through the 

nebulizer. The nebulizing air passes through flow and pressure regulators, an external 

bubbler to saturate the air at room temperature and then a second bubbler to assure 

that the nebulizing air is saturated a 32° F prior to entering the nebulizer. 

• A temperature control component (ice bath) is used to control the temperature of the 

nebulizer air, the nebulizer and the settling/equilibrating chamber at 32° F. 

• A Collison-type nebulizer

16 component is used to create the solution droplet aerosol. 

It consists of three major components: the nebulizer cup, the nebulizer and nebulizer 

nozzle as describe in more detail in Appendix C. The nebulizer cup contains the 

standard solution. This solution is continuously circulated from the nebulizer cup to 

an external reservoir to minimize the impact of vapor loss on solution concentration 

and to allow for determination of the solution use rate. 

• A settling/equilibrating chamber component located just above the nebulizer 

component. The nebulizer-generated aerosol is directed into this chamber where 

large droplets settle from the gas stream and the remaining droplets equilibrate with 

water vapor prior to entering the drying chamber. The nebulization process creates a 

droplet spray containing a wide range of droplet sizes. The largest droplets impact on

the walls of the nebulizer cup and are recycled. The smaller droplets are entrained in 

the nebulizer air flow and pass into the settling-equilibration chamber. The function 

of the settling-equilibration chamber is to remove and recycle all droplets greater than 

about 20 μm in diameter as well as to assure droplet-vapor equilibrium at 32°F. 

Thus, the only droplets emitted into the drying chamber have diameters less than 20 

μm and have been equilibrated with water vapor at 32°F. 

• A drying chamber component with temperature and flow controls. In this chamber, 

the size-restricted and vapor equilibrated aerosol from the settling/equilibrating 

chamber is surrounded by dry air at about 300° F, which is used to dry the reference 

solution droplets prior to being emitted from the QAG. The aerosol exiting the 

drying chamber consists of the transport gas (air), water and metal vapor and dried 

salt particles. The size of the salt particles is controlled by the analyte solution 

concentration, the design of the settling chamber and the flow rate of nebulizer air. 

This aerosol is the reference aerosol produced by the QAG. However, in this 

experiment, the aerosol was further diluted with makeup air prior to being transported 

to the Xact stilling chamber from which both Xact-IAP and XFM samples were 

drawn. QAG efficiencies referred to in this report are combination generation 

Method 301 Eval.: V1.0 Section 3.0 Methods Page 16 of 40
(aerosol emitted from the drying chamber of the QAG) and transport to the Xact 

stilling chamber. 

The QAG’s generated aerosol concentration ( ) is process traceable to NIST through 

the traceability of its components (see Appendix C). As demonstrated in Equation 1 below, 

the generated concentration is a function of the solution standard concentration of the 

( ), total flow rate (F

a-QAG Ci

s-QAG Ci t), rate of mass loss of the solution (Rm), and rate of vapor loss 

(Rv). Process traceability to NIST is established by using instruments that are NIST-traceable 

(e.g., calibrated with NIST standards) to measure these parameters and a solution with NISTtraceable concentrations. 

The final product of the QAG is an aerosol containing dried salt particles and vapors of the 

analyte or analytes. The concentration of the analytes in the aerosol and the concentration 

uncertainty are calculated from the QAG’s recorded operating parameters. The equation for 

calculating the generated aerosol concentration is as follows: 

 

(R R ) F

C C m v

t

s QAG

a QAG i

i = −

−

− Equation 1

Where: 

a-QAG Ci = Concentration of the ith element in the reference 

aerosol generated by the QAG 

s-QAG Ci = Concentration of the ith element in the QAG’s NIST-traceable 

solution 

Ft = Total combined flow of the nebulizer air, drying air and makeup 

air or stack gas 

Rm = Total rate of solution mass loss for the QAG, determined from the 

slope of a linear least squares fit of the reservoir mass data over the 

period of a test or series of tests 

Rv = Rate of vapor loss from the reference solution, as calculated using 

the following equation:

 ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = −

c

e

v e v P

P R F M 1 Equation 2

Where: 

Fe = Flow of expanded nebulizer air in the QAG 

Mv = Mass of water vapor in a liter of saturated air at 32°F 

Method 301 Eval.: V1.0 Section 3.0 Methods Page 17 of 40
Pe = Absolute pressure of the expanded nebulizer air 

(atmospheric) 

Pc = Absolute pressure of the compressed nebulizer air 

Uncertainty in the generated reference aerosol concentration was determined using standard 

propagation of error techniques relevant to the parameters used in Equation 1 and Equation 2 

(See Appendix C). The estimated uncertainties for these parameters during Phase I and II 

testing are 0.5% for , 3% for F s-QAG Ci e, 1.5% for Ft, 7% for Mv, 3% for Pc, 1% for Pe, and 1% 

for Rm . These uncertainty values are based on equipment manufacturer certifications, NIST 

and/or engineering estimates of nebulization/equilibration temperature uncertainties. Using 

these uncertainties, the propagated uncertainty during Phase I and II testing was calculated to 

be about 4% for an aerosol concentration ( ) of about 70 μg/m a-QAG Ci

3

. 

3.2 XFM Candidate Conditional Method 

The current reference method for measuring metal emissions from stationary point sources 

(Method 29) is based on 30 year old probe, filter and impinger type sampling trains. This 

method is difficult and dangerous to use, creates large quantities of hazardous waste, 

recovered samples are difficult to ship, and several weeks are required for an analysis to be 

completed. The XFM candidate conditional method summarized in this subsection and 

described in detail in Appendix B is based on a safe, easy to use sampling train that traps 

both PM and vapor phase metals on stacked filters that a field engineer never touches and can 

easily be either analyzed by XRF in the field or express mailed to a laboratory for 24 hour 

turn around times. Although the XFM procedure has been optimized for MACT metal 

analytes, it is applicable to elements with atomic number ranging from 13 (Al) to 92 (U). 

The sampling train used for these Method 301 validation tests is shown schematically in 

Figure 6. It is composed of five major subcomponents: 

• Extraction-stilling chamber interface assembly 

• Filter holder

• Sample flow control 

• Extraction interface flow control 

• Dilution flow control

Method 301 Eval.: V1.0 Section 3.0 Methods Page 18 of 20
Regulator

Pressure

Gauge

2-way

Valve

Regulator

Filter

Holder

D-MFM

Port

Adaptor

Dessicant Dryer Corrosive Trap

Plenum

Compressed

 Air Supply

Pump

To Exhaust

 Stilling

Chamber

Dessicant Dryer

Dilution Flow

Integrator

Extraction

Assembly

Total Flow

Integrator

To

Exhaust

Eductor

T-MFM

Quick

Disconnector

Needle

Valve

Needle

Valve 2-way

Valve

Compressed

 Air Supply

Thermocouple

Figure 6: Schematic flow diagram of the sampling train used in Phase I and II XFM 

validation tests.

A photograph of the assembled extraction-interface and filter holder is shown in Figure 7. 

The port adapter is on the left side in the photograph and consists of PTFE-coated 2-inch 

diameter stainless steel (SS) tubing with a sanitary flange for attaching the assembly to the 

stilling chamber. In the case of normal stack sampling, this interface would be attached 

directly to a large diameter shielded probe type of sample extraction system. This port 

adapter is followed by an extraction assembly that draws stack gas at the rate of about 20 to 

30 lpm into it using an eductor and flow control module. A representative sub-sample of this 

stack gas is blended with dry dilution gas in this assembly prior to being drawn through the 

SS sample filter holder assembly shown on the right side of the photograph. The sample and 

dilution flow rates are on the order of one to two lpm and controlled by the sample and 

dilution flow control components. All temperatures and flows are controlled, monitored and 

recorded during sampling. 

Figure 7: Photograph of the assembled port adaptor, extraction assembly and filter 

holder. 

An exploded schematic view of the XFM filter holder with filter cassette is illustrated in 

Figure 8. The filter cassette shown in the middle contains an off-the-shelf upstream PTFE 

filter, TefloTM by Pall Inc.23 which traps PM and a downstream reactive filter that is used to 

Method 301 Eval.: V1.0 Section 3.0 Methods Page 19 of 20
trap vapor phase metals. The filters are loaded into the filter cassette in the laboratory and 

transported to and from the field in plastic Petri dishes. The field engineer simply removes 

the filter cassette from its Petri dish and places it in the SS filter holder. When sampling is 

finished, the filter cassette is removed from the filter holder and returned to its Petri dish. In 

this process, the filters are not touched by the field engineer, which reduces the possibility of 

contaminating and/or disturbing the deposits. 

The analyte mass on each XFM filter deposit is determined by EPA Compendium Method 

IO-3.314. This method is the same as one used to measure 48 ambient metals for thousands of 

filters collected by EPA’s PM2.5 Speciation Program15. 

The aerosol concentration of each metal is calculated using Equation 3. 

 XFM

d

XFM

t

REO

i

PTFE

e XFM i

i V V

M M C −+ =

−

−

7

Equation 3

Where: 

= Concentration of the i e-XFM Ci

th analyte in the emissions measured by 

 the XFM 

= XRF-determined mass of the i PTFE Mi

th analyte on the PTFE filter.

= XRF-determined mass of the i REO−7 M i

th analyte on the reactive filter 

(REO-723) 

= Total volume (emission plus dilution) sampled by the XFM XFM Vt

= Volume of dilution air drawn through filters of the XFM XFM Vd

Mass and volume measurement uncertainties are typically on the order of one to three 

percent of the value near the emission limit concentrations. This suggests XFM aerosol 

concentration uncertainties on the order of three to five percent. 

Method 301 Eval.: V1.0 Section 3.0 Methods Page 20 of 20
Figure 8: Exploded schematic view of XFM filter holder with filter cassette. 

3.3 Xact Instrumental Analyzer Procedure 

The Xact instrumental analyzer procedure (Xact-IAP) has the ability to provide stack gas 

metals analysis results for up to 20 metals every 15 minutes. This capability could greatly 

facilitate trial burn tests, engineering/design studies as well as compliance testing by 

providing near real time results necessary for rapid evaluation of engineering and/or burn 

conditions, or compliance success or failure. This candidate conditional reference procedure 

is based on sampling of PM and vapor phase metals using a reactive filter tape (PRO-1124) 

followed by XRF determination of metal mass in the resulting deposits while the next sample 

is being collected on a fresh section of filter tape. 

The Xact instrumental analyzer draws a continuous representative sample of 25-100 lpm of 

stack gas through a stilling chamber. A small isokinetic sub-sample (~1 lpm) is extracted 

from the stilling chamber and blended with about 0.2 lpm of dilution gas. The cooled and 

diluted stack gas is drawn through the reactive filter tape where the metals are quantitatively 

trapped. Following collection, the tape is advanced to an XRF analyzer for metal mass 

determination while another sample is collected. The Xact takes the XRF-determined mass in 

μg/sample divides this mass by the stack gas volume for the run, and reports concentrations 

Method 301 Eval.: V1.0 Section 3.0 Methods Page 21 of 23
for up to 20 analyte metals in μg/dscm. Response time depends upon the end-user’s required 

detection limits, but is typically 10 to 30 minutes. 

Figure 9 shows key Xact components. The Xact has a two-foot by three-foot footprint and is 

four-feet tall. Concentrations are determined by the Xact controller, and automatic flow, 

upscale, and blank checks are available to ensure that calibration is maintained. All data is 

stored in a personal computer and can be easily imported into a spreadsheet or data 

acquisition system. XRF calibration is stable over extended periods. Its calibration is 

checked daily, but rarely needs recalibration more frequently than once or twice a year. 

The Xact consists of the following five subsystems (Figure 9): 

• Sample interface: The sample interface withdraws a representative sample of 

effluent from the source and delivers it to the sampling module. The Xact sampling 

probe utilizes a shrouded probe type design to draw a representative sample of 

effluent from the source. The effluent is then transported from the probe through a 

heated transport line to the sampling module. 

• Sampling module: The sampling module consists of all the equipment necessary for 

extracting all elements of interest from the flue gas. The Xact draws a flow of 

between 25 and 100 lpm through a stilling chamber where the flow is slowed prior to 

withdrawing a sub-sample of about 0.50 to 1.0 lpm for analysis. About 0.20 lpm of 

dilution air is added and drawn through chemically reactive filter tape. The metal 

analytes of interest are captured quantitatively on this filter tape. 

• Volume measurement module: After being drawn through the filter tape the flue gas 

is dried and the total gas flow rate is measured. The sample flow rate is calculated by

subtracting the dilution flow from total flow. The flow is totalized over the sampling 

period to obtain a volume measurement. Because the flue gas has been dried prior to 

measurement, the volume and reported aerosol concentration are reported in units of 

dry standard cubic meters (dscm). 

• X-Ray analysis module: The Xact measures the mass for each metal using XRF 

analysis in accordance with the procedures listed in EPA’s Compendium Method IO3.314. 

Method 301 Eval.: V1.0 Section 3.0 Methods Page 22 of 23
Figure 9: Overview of Xact-IAP components and flow schematic. 

• Data recorder: The mass as determined by XRF is divided by the sample flow rate 

using Equation 4 and recorded by the Xact controller. The data can then easily be 

imported into a data acquisition system or can be stored on a personal computer as a 

text file. 

(V V )

M C XACT

d

XACT

t

e XACT

e i

i − =

−

Equation 4

Where: 

e Ci = Concentration of the ith metal in the emissions measured by the Xact 

e XACT Mi− = Mass of the ith metal in the sample as measured by XRF. 

XACT Vt = Total volume as measured by the Xact 

XACT Vd = Dilution volume as measured by the Xact

Method 301 Eval.: V1.0 Section 3.0 Methods Page 23 of 23
The Xact also incorporates a number of procedures to ensure the accuracy and reliability of 

its data. At least once each day the Xact performs upscale and zero checks. The values 

reported each day are compared with the original calibration to ensure the accuracy and 

stability of the XRF analyzer. The Xact also has a palladium rod permanently mounted into 

the XRF analysis area. The reported concentration of this rod is a known and checked with 

every sample analyzed on the Xact. The volume measurement is compared at least once a 

day against another mass flow meter. In addition the calibration of the XRF analysis can be 

checked for all elements using NIST traceable thin film standards and the accuracy of the 

flow meters can be verified by checking them with a NIST traceable flow measurement 

device such as a DryCal® meter

25. 

4.0 Calculations 

4.1 Overview 

This section summarizes key calculations for Phase I and II testing with a more detailed 

discussion presented in Appendix K. Calculations for the QAG, XFM and Xact-IAP are 

shown in the next three subsections while Subsection 4.6 presents the calculations of 

comparison parameters such as bias and precision. The Phase I and II test results show that 

background concentrations of the five MACT metals in the stack gas and laboratory air were 

essentially equal to zero, and that the concentration of the spiked reference aerosol was 

constant to within a few percent. This low background and constant concentration allowed 

for the determination of bias and precision using replicate sequential measurements instead 

of paired measurements. This in turn allowed for simpler calculations of validation metrics 

as discussed in Subsections 4.6 and 4.7. 

4.2 List of Symbols and Terms 

b0 = y intercept 

1 b = slope 

B = bias 

B = absolute value of the bias 

CD = minimum detection limit 

Ci = concentration of the ith element 

a Ci = concentration of the ith element in the aerosol

Ci = mean concentration of the ith element 

a CPb = concentration of lead in the aerosol 

s Ci = concentration of the ith element in the solution 

s CPb = concentration of lead in the solution 

u Ci, j = concentration of the ith upscale metal reported for the jth interval 

u Ci,c = concentration of the ith upscale metal reported at calibration

Method 301 Eval.: V1.0 Section 4.0 Calculations Page 24 of 75
L Ci = Emission limit of the ith metal 

z Ci, j = Blank concentration of the ith metal reported for the jth interval 

z Ci,c = Reference value of the low level calibration standard for the ith metal 

M

Ci = mean metal concentration a M Ci

− = concentration of the ith element in the aerosol as measured by the candidate 

method a M

Ci

−

= mean concentration of the ith element in the aerosol as measured by candidate 

method a QAG Ci

− = concentration of the ith element in the reference aerosol generated by the QAG 

a XACT Ci− = concentration of the ith element in the aerosol reported by the Xact 

a XFM Ci− = concentration of the ith element in the aerosol measured by the XFM 

s QAG Ci− = concentration of the ith element in the standard solution used for the QAG 

REO−7 Ci = concentration of the ith analyte on the XFM reactive filter23

PTFE Ci = concentration of the ith analyte on the PTFE filter 

PRO−11 Ci = concentration of the ith analyte on the Xact reactive filter

CDi = i

th element calibration drift 

CFi = correction factor for the ith element 

d = average of differences

Ei = efficiency of the ith element 

Fe = flow of expanded nebulizer air in the QAG 

Ft = total spiked flow 

Mv = mass of water vapor in a liter of saturated air 

PTFE Mi = XRF-determined mass of the ith analyte on the PTFE filter 

PRO−11 Mi = XRF-determined mass of the ith analyte on the Xact reactive filter

23

REO−7 M i = XRF-determined mass of the ith analyte on the XFM reactive filter 

e XACT Mi− = XRF reported metal mass on the filter (μg/filter) 

n = number of measurements 

i

p = precision for the ith element 

Pc = absolute pressure of the compressed nebulizer air in the QAG 

Pe = pressure of the expanded nebulizer air in the QAG 

PRBi = percent relative bias for the ith element 

PRSD = percent relative standard deviation 

r = correlation coefficient 

2

r = Square of the correlation coefficient 

Rf = filter ratio to confirm total metal trapping efficiency with the XFM filters

Pb Ri = relative ratio for the for the ith element divided by the concentration of lead 

Rm = total rate of solution mass loss for the QAG 

Method 301 Eval.: V1.0 Section 4.0 Calculations Page 25 of 75
RRM = average of the RM data set 

Rv = rate of vapor loss of the QAG standard solution 

RA = relative accuracy

RSD = relative standard deviation 

SD = standard deviation 

SDM = standard deviation of the means 

M

i SDM = standard deviation of the mean of a series of concentration measurements of the 

i

th element 

t = t-statistic 

Vt = total volume sampled 

Vd = volume of dilution air drawn through the XFM 

XFM Vt = total volume sampled through the XFM filters

XFM Vd = volume of dilution air drawn through the XFM filters

XACT Vt = total volume sampled during Xact run (dscm)

XACT Vd = volume of dilution air during Xact run (dscm)

B Ui = Uncertainty in the ith element bias 

a QAG Ui− = Uncertainty in the ith element reference aerosol concentration 

i x = value of the ith data point for data set x

x = average of the values in data set x

i y = value of the ith data point for set of data y

y = average of the values in data set y

ZDi = ith element zero drift 

4.3 QAG Reference Aerosol Concentration 

Calculation of the QAG generated reference aerosol concentration was based on a 

measurement of the nebulization rate of analyte-containing solution and a measurement of 

the rate of flow of gas into which the nebulized solution droplets were injected. The 

concentration of this reference aerosol was calculated using the following equation: 

 (R R ) F

C C m v

t

s QAG

a QAG i

i = −

−

− Equation 1 (see Section 3.1)

Where:

a-QAG Ci = QAG reference aerosol concentration of the ith element (μg/dscm) 

s-QAG Ci = Concentration of the ith element in the solution (μg/g) 

Ft = Total spiked reference aerosol gas flow rate (dscm/min) 

Rm = Measured rate of solution mass loss from a reservoir (g/min) 

Method 301 Eval.: V1.0 Section 4.0 Calculations Page 26 of 75
Rv = Reservoir mass loss rate due to water vapor loss (g/min) 

The total solution use rate (Rm) was determined by measuring the mass of the solution 

reservoir every 15 seconds and determining the slope of a scatter plot of this measured mass 

versus time. The rate of water vapor loss was calculated using to the following equation: 

 ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = −

c

e

v e v P

P R F M 1 Equation 2 (see Section 3.1)

Where: 

Fe = Expanded nebulization air flow rate as measured by the flow 

meter on the nebulizing air line. 

Mv = Mass of water vapor contained in a liter of water vapor 

saturated air at 32 °F. This value has been well defined 

and is listed as 4.84 mg/liter26

Pe = Pressure of the expanded gas outside the nebulizer nozzle. 

Since the droplet generating chamber and the droplet size 

selector are open to the atmosphere, Pe is the atmospheric 

pressure recorded from a field barometer during Phase II 

testing and was assumed to be 14.7 psi for Phase I testing that 

was conducted at near sea level. 

Pc = The absolute pressure of the compressed air upstream of the 

nebulizer aspiration nozzle, recorded from the precision 

pressure gauge located on the nebulizer air line (psi). 

4.4 XFM Measured Aerosol Concentration 

The XFM determined concentration of the five MACT metals in the QAG-generated 

reference aerosol is based on a measurement of the metal mass deposited on the XFM filters

and the sample volume that passed through the filters. The total volume that passed through 

the XFM filter cassette and the volume of dilution air were recorded with flow integrators 

and an operator during each XFM run. Sample volume was calculated by subtracting the 

dilution volume from the total volume. Metal mass concentrations in micrograms per spot 

were determined using a CES XRF analyzer and procedures defined in EPA’s Inorganic 

Compendium Method 3.3 “Determination of Metals in Ambient Particulate Matter Using XRay Fluorescence Spectroscopy”14 The XFM determined concentrations were calculated 

using the following equation: 

 

XFM

d

XFM

t

REO

i

PTFE

a XFM i

i V V

M M C −+ =

−

−

7 Equation 3 (see section 3.2)

Where: 

Method 301 Eval.: V1.0 Section 4.0 Calculations Page 27 of 75
= XFM measured concentration of the i a-XFM Ci

th element in the aerosol 

 (μg/dscm) 

= XRF-determined mass of the i PTFE Mi

th analyte on the PTFE filter 

REO−7 M i = XRF-determined mass of the ith analyte on the reactive filter 

(REO-7)23 

= Total volume sampled during XFM run (dscm) XFM Vt

= Volume of dilution air drawn through filters XFM run (dscm) XFM Vd

4.5 Xact-IAP Measured Aerosol Concentration 

During a sample run, the Xact recorded the total dry volume of gas that passed through the 

filter tape. Following the sampling period, the tape was advanced to the XRF analysis region 

where each metal’s mass was determined in micrograms per spot. The mass was then divided 

by the total dry volume for a given sample run to produce concentrations in μg/dscm. Xact 

concentrations for these tests were calculated using the following equation: 

( ) XACT

d

XACT

t

XACT

a Xact i

i V V

M

C − = −

Equation 4 (see Section 3.3)

Where: 

a Xact Ci− = Xact reported concentration of ith element in the aerosol (μg/dscm) 

XACT Mi = XRF reported metal mass on the filter (μg/filter) 

XACT Vt = Total volume sampled during Xact run (dscm)

XACT Vd = Volume of dilution air during Xact run (dscm)

4.6 Validation Comparison Parameters 

4.6.1 Bias 

The proposed candidate conditional method bias was determined by comparing the candidate 

method’s mean measured concentration ( a M

C i

−

) to the calculated reference aerosol analyte 

concentration ( ). The bias (B) of the proposed candidate conditional method is 

defined as the difference between the mean candidate method measured aerosol 

concentration and the calculated reference aerosol concentration over a common 

measurement interval; i.e.,

a QAG Ci−

Equation 5 

 

a QAG

i

a M Bi Ci C − − = −

Method 301 Eval.: V1.0 Section 4.0 Calculations Page 28 of 75
4.6.2 Bias Significance Test 

The test for significance of bias used in this report is different from that used in Method 301 

primarily because sequential measurements were used in these tests instead of paired 

measurements, but also because the uncertainty in the reference aerosol concentration was 

significant relative to the standard deviation of the mean of the measurements. In this case, 

the criteria for bias significance is whether or not the bias is greater than two times (95% 

confidence level) the uncertainty in the bias. The uncertainty in the bias for the ith element 

( ) is given by the following equation when a reference aerosol spike is used: B Ui

( ) ( ) 2 M 2

i

a QAG

i

B

i U = U + SDM − Equation 6

Where: 

B Ui = Uncertainty in the ith element bias 

a QAG Ui− = Uncertainty in the ith element reference aerosol concentration

M

i SDM = Standard deviation of the mean of a series of concentration 

measurements of the ith element 

Thus, the bias is significant at the 95% confidence level if . B Bi Ui > 2

4.6.3 Correction Factor 

The correction factor is a factor used to correct for significant differences between measured 

and reference concentration; i.e., efficiency difference in the case of the QAG or bias in the 

case of the XFM and Xact. If the efficiency or bias is determined to be significant, a 

correction factor for the ith element (CFi) can be calculated using the following equation and 

applied to future measurements to compensate for the method’s bias or inefficiencies. 

a M

i

a QAG

i

i C

C CF −

−

= Equation 7

4.6.4 Drift 

Drift is generally defined as a percent change in a mean value measured over an extended 

period of time. It is primarily applicable to the Xact CEMS and Xact-IAP and based on a 

comparison of zero and upscale measurements with those made when the instrument was last 

calibrated. These measurements are indicators of instrument calibration drift (CDi) and zero 

drift (ZDi). These drift values are calculated using the following two equations, which are 

based on equations used in proposed performance specification 10 for multi-metal CEMS. 

Method 301 Eval.: V1.0 Section 4.0 Calculations Page 29 of 75
( )100%

C

C C

CD u

i,c

u

i,c

u

i, j

i

− = Equation 8

Where: 

CDi = i

th element calibration drift 

u Ci, j = Concentration of the ith upscale metal reported for the jth 

 interval 

u Ci,c = Concentration of the ith upscale metal reported at calibration

( )100% , ,

L

i

z

i c

z

i j

i C

C C

ZD − = Equation 9

Where: 

ZDi = i

th element zero drift 

z Ci, j = Blank concentration of the ith metal reported for the jth interval 

z Ci,c = Reference value of the low level calibration standard for the ith

metal 

L Ci = Emission limit of the ith metal 

4.6.5 Efficiency 

Efficiency as used in this document is defined as the ratio of a measured concentration to a 

reference concentration expressed as a percent. In the case of the QAG, for example, it is the 

ratio of the aerosol concentration measured in the Xact stilling chamber to the calculated

reference aerosol concentration. Efficiencies other than 100% are due to generation and 

transport inefficiencies and/or errors associated with the generation and measurement of the 

aerosol concentration. The efficiency (Ei) of the ith element is calculated using the following 

equation: 

a QAG 100%

i

a M

i

i C

C E −

−

= Equation 10

4.6.6 Efficiency Significance Test 

The criteria for efficiency significance is whether or not the difference between the measured 

efficiency and 100% is greater than two times (95% confidence level) the uncertainty in this 

Method 301 Eval.: V1.0 Section 4.0 Calculations Page 30 of 75
difference. The uncertainty in the efficiency for the ith element ( ) is given by the 

following equation when a reference aerosol spike is used: 

E Ui

2

a M

i

a M

i

2

a QAG

i

a QAG

i

i

E

i

C

SDM

C

U U E ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

+ ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = −

−

−

−

Equation 11

(See Section 4.6.2)

Thus, the efficiency is significant at the 95% confidence level if 

E Ei Ui − 100 > 2 Equation 12 

 

4.6.7 Filter Ratio

A validation parameter called filter ratio (Rf) was used as an indicator to confirm total metal 

trapping efficiency with the XFM filters. The mass of the low volatility metals Pb and Cr as 

measured on the XFM PTFE filter ( ) and the following reactive filter ( ) were 

used in this calculation. The filter ratio is calculated using the following equation:

PTFE MiREO−7 M i

−7 100%

+ = REO

i

PTFE

i

PTFE

i

f M M

M

R Equation 13

4.6.8 Linearity 

Evaluation of linearity of the QAG and the candidate conditional methods was based on four 

parameters derived from a linear least squares fit of the measured concentration plotted 

against the reference concentration; i.e., slope, intercept, correlation coefficient and variance. 

Given a general set of data (xi , yi ) with n data points, the slope (b1), y-intercept (b0), 

correlation coefficient (r), and the variance (r

2

) are defined by the following equations: 

( )( )

∑( )

∑ −

− − =1 2

x x

x x y y b

i

i i

Equation 14

b y b x 0 = − 1 Equation 15

Method 301 Eval.: V1.0 Section 4.0 Calculations Page 31 of 75
( )( )

∑( )∑( )

∑ − −

− − = x x y y

x x y y

r

i i

i i

2

2

Equation 16

4.6.9 Mean Concentration 

The mean metal concentration (

M

Ci ) measured by a candidate conditional method is equal to 

the sum of the individual measured concentrations (Ci) divided by the number of measured 

concentrations (n). 

n

C

C

M i

i

∑= Equation 17

4.6.10 Metal Ratio 

As used in this report, the metal ratio ( ) is the ratio of the ith metal aerosol concentration 

normalized to the Pb aerosol concentration divided by the ith metal solution concentration 

normalized to the Pb solution concentration; i.e.,

Pb Ri

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

=

s

Pb

s

i

a

Pb

a

i

Pb

i

C

C

C

C

R

Equation 18

4.6.11 Percent Relative Bias 

The percent relative bias for the ith element (PRBi) is the ith element bias (Bi) divided by the 

reference aerosol concentration for the ith element ( ) time 100%, i.e., a QAG Ci

−

% 100

a QAG

i

i

i C

B PRB − = Equation 19 

4.6.12 Precision 

Precision is an indicator of the degree of mutual agreement between individual measurements 

of a parameter having the same value. In this report it is defined as the percent relative 

standard deviation (PRSD) of a series of measurements of the same aerosol concentration 

held constant over a relative short test period in contrast to stability, which is the PRSD of a 

series of measurements determined over an extended period of time. The precision for the ith

element (Pi) is given by the following equation: 

Method 301 Eval.: V1.0 Section 4.0 Calculations Page 32 of 75
100%

i

i C

SD P = PRSD = Equation 20

Because there is random variability associated with both the reference aerosol concentration 

as well as the measured aerosol concentration, the measured precision is an indicator of the 

variability introduced by all components of the generation-measurement system; i.e., QAG 

and candidate conditional method. For this series of tests, the magnitude of the QAG 

precision is considered to be similar to the candidate conditional method. As such, the 

precision of the QAG or candidate conditional method is defined as the measured precision 

divided by the square root of 2. 

4.6.13 Standard Deviation 

The standard deviation (SD) in the concentration is equal to the square root of the sum of the 

differences between the mean concentration and individual concentration measurements 

squared, divided by the number of measurements less one. 

( )

1

2

−

− = ∑

n

C C

SD i i

i Equation 21

4.6.14 Standard Deviation of the Mean 

The standard deviation of the mean (SDM) is equal to the SD divided by the square root of 

the number of measurements (n). 

n

SD SDM i

i = Equation 22

4.6.15 t-statistic 

Equation 23 SDM

B

t =

4.7 Other Comparison Parameters 

4.7.1 Detection Limits 

The minimum detection limit, CD, is defined as the smallest concentration that a particular 

measurement can detect. Using the definition developed by Currie27 detection may be 

Method 301 Eval.: V1.0 Section 4.0 Calculations Page 33 of 75
considered reliable when the probability of detecting a concentration CD is sufficiently large 

(95%), while the probability of incorrectly detecting a blank is sufficiently small (5%). 

Using this definition of detection and the selected probabilities (95% and 5%), it can be 

shown that: 

CD = 3.29SD Equation 24

where SD is the standard deviation of observed results when the true concentration is zero; 

i.e., standard deviation of a series of blank measurements. The minimum detection limit of a 

candidate conditional method will be the analytical detection limit as defined above using a 

blank filter, divided by the typical volume of stack gas sampled; i.e., about 0.012 dscm for 

the Xact-IAP and 0.03 dscm for the XFM. 

4.7.2 EPA Relative Accuracy 

The EPA has defined a figure-of-merit to evaluate candidate measurement methods relative 

to current reference methods or standards. This figure-of-merit, called relative accuracy, 

includes both a component for bias and a component for precision, which is designed to 

exclude imprecise methods with low bias as well as precise methods with high bias. 

However, it does not take into consideration uncertainties in reference method measurements 

nor can it be related to a statistically defined level of confidence. Although this EPA-defined 

relative accuracy term has proved useful in some cases, it is neither required nor is it 

considered appropriate for this evaluation. It is defined here because it is discussed in this 

report. 

RM

i

R

SD

n

t d

RA

0.975 +

= Equation 25

Where: 

RAi = Relative accuracy for the ith element 

d = Arithmetic mean of the difference, d, of paired CEMS and 

reference method (RM) data set 

SD = Standard deviation 

RRM = Average of the RM data set 

Method 301 Eval.: V1.0 Section 4.0 Calculations Page 34 of 75
5.0 Quality Control and Assurance 

5.1 Overview 

The overall objectives of Quality Control (QC) and Assurance (QA) for these tests were to 

assure and document that the accuracy of the measurements were 1) NIST traceable and 2) 

supportive of the method validation goals stated in the test plan (Appendix A). It is clear that 

these goals were met as evidenced by the high level of agreement between the QAG 

generated reference aerosol concentration and the independently measured XFM and XactIAP aerosol concentrations (±5%) as discussed in the following section. Overall, the QAG 

and candidate methods showed good QA/QC and all 240 Xact-IAP and 50 XFM runs taken 

during QAG operations were considered to be valid. Mass, temperature, pressure, XRF 

standards check, Xact-IAP upscale, Xact-IAP blank, and Xact-IAP thin film measurements, 

etc. met the test plan objectives. The complete QA/QC database and calculations are 

presented in Appendices G and H, and the original QA/QC data sheets are provided in 

Appendices I and J. This section provides a summary of key QA/QC results and issues for 

the QAG, XFM, and Xact-IAP Phase I and II tests. 

5.2 QAG 

Generating an aerosol with an accurate NIST-traceable concentration with the QAG required 

control of such parameters as mass, flow, temperature, and pressure. The primary 

measurements for these parameters all met the test plan objectives. One key parameter, 

standard solution use rate (Rm, Equation 5), was a calculated parameter based on the slope of 

a plot of reservoir mass versus time. Although the balance used for the reservoir mass 

measurement was NIST traceable to better than 1%, the uncertainty in the slope (use rate, 

g/min.) for any particular period was on the order of a few percent. The QAG solution use 

rates during Phase I and II test periods are listed in Table 6. The plots from which these rates 

were determined are shown in Figure 10 and Figure 11. For both phases, the total mass 

consumption was reasonably stable with an average correlation (r) of better than 0.99 and an 

average standard solution consumption rate of 0.112 ± 0.009 g/min. 

The total consumption rate depends upon the rate of solution droplet generation and 

evaporation. Since the nebulizer emits at a constant rate as soon as it begins operation, the 

QAG metal emission rate is stable after only a few minutes. The evaporation rate; however, 

is dependent upon the temperature of solution reaching a steady state, which typically 

requires several hours of operation if the solution has not been pre-cooled. QAG 

evaporation rates are typically 20-30% of the total solution consumption rate. For both 

phases, the temperature of the flow was controlled to 32oF using an ice water bath and 

bubbler, pressure was maintained between 17 and 19 PSI, and flow was kept constant at 10.1 

slpm. The ambient pressure is also used to determine evaporation rate and was assumed to be 

14.7 PSI for Portland, OR and 14.3 PSI for Lafayette, IN28. Uncertainty in the evaporation 

rate is on the order of 10% resulting in a 2-3% uncertainty in the total solution consumption 

rate. 

Method 301 Eval.: V1.0 Section 5.0 Quality Control and Assurance Page 35 of 75
Table 6: QAG Emission Rates for Phase I and II. 

Test 

Phase

Date Run

Corr 

Coeff.

QAG

Rate

I 15-Dec-04 1-12 0.999 0.105

I 16-Dec-04 13-16 0.992 0.121

I 16-Dec-04 17-20 0.989 0.105

I 16-Dec-04 21-24 0.973 0.105

I 17-Dec-04 25-26 0.926 0.110

II 4-Mar-05 1-12 0.997 0.130

II 6-Mar-05 15-18 0.976 0.108

II 7-Mar-05 19-22 0.995 0.114

II 8-Mar-05 23-26 0.997 0.110

0.983 0.112

0.023 0.009

2.4 7.6

Avg.

SD

PRSD

On March 5th, the QAG experienced problems with freezing in the nebulization chamber. 

Although the chamber and the tubing leading to it were maintained at 32oF, it is believed that 

the expanding gas and solution evaporation in the chamber lowered the solution to below its 

freezing point. The stainless steel tubing leading to the nebulizer was replaced with TygonTM 

tubing which helped maintain the temperature above freezing. Two XFM runs, 13 and 14, 

were taken during this time and were in good agreement with the Xact-IAP (less than 10% 

difference). These two XFM runs, however, were disregarded since they could not be 

compared to the predicted QAG concentration because of the above noted QAG freezing 

problem. 

XFM Run 1-12

y = -0.1054x + 881.02

R2

 = 0.9988

700

730

760

790

820

850

880

910

0 250 500 750 1,000 1,250 1,500

Elapsed Time (min)

Mass (g)

XFM Run 13-16

y = -0.121x + 1080.3

R2

 = 0.9918

1,055

1,060

1,065

1,070

1,075

1,080

1,085

0 25 50 75 100 125 150 175 200

Elapsed Time (min)

Mass (g)

XFM Run 21-24

y = -0.1051x + 808.9

R2

 = 0.9731

800

801

803

804

806

807

809

810

0 10 20 30 40 50 60 70 80

Elapsed Time (min)

Mass (g)

XFM Run 17-20

y = -0.105x + 1071.1

R2

 = 0.9894

1,045

1,050

1,055

1,060

1,065

1,070

1,075

0 25 50 75 100 125 150 175 200

Elapsed Time (min)

Mass (g)

XFM Run 25-26

y = -0.1099x + 1923.5

R2

 = 0.9261

1,916

1,917

1,919

1,920

1,922

1,923

1,925

0 5 10 15 20 25 30 35 40 45 50

Elapsed Time (min)

Mass (g)

Figure 10: QAG solution mass loss rate during Phase I testing. 

Method 301 Eval.: V1.0 Section 5.0 Quality Control and Assurance Page 36 of 75
March 6, 2005 Runs 15-18

y = -0.108x + 1775

R2

 = 0.9759

1745

1750

1755

1760

1765

1770

1775

1780

0 40 80 120 160 200 240

Elapsed Time (min)

mass (g)

March 7, 2005 Runs 19-22

y = -0.1144x + 1765.4

R2

 = 0.9949

1710

1720

1730

1740

1750

1760

1770

0 40 80 120 160 200 240 280 320 360

Elapsed Time (min)

mass (g)

March 8, 2005 Runs 23-26

y = -0.1098x + 1533.7

R2

 = 0.997

1420

1440

1460

1480

1500

1520

1540

0 100 200 300 400 500 600 700 800 900

Elapsed Time (min)

mass (g)

March 5, 2005 Runs 1-12

y = -0.1304x + 1767.7

R2

 = 0.9969

1700

1710

1720

1730

1740

1750

1760

1770

1780

0 50 100 150 200 250 300 350 400 450

Elapsed Time (min)

mass (g)

Figure 11: QAG solution mass loss rate during Phase II. 

5.3 XFM 

The XFM was operated for 26 runs during each test phase. Other than the two runs that could 

not be compared to the QAG because of solution freezing, all XFM runs were considered 

valid and were used in calculating QAG efficiency and XFM bias and precision. The XFM 

reports concentrations in mass per volume. As part of the QA procedures for these tests, the 

XFM mass and volume measurements were evaluated for accuracy using NIST-traceable 

standards. For these tests, the XRF reported concentrations within 5% of the NIST standards 

(SRM 1832 and 1833) for all elements measured during calibration, and all of the daily XRF 

QA measurements were within 5% of the values obtained immediately after calibration. For 

this reason, no changes were made to any of the reported XRF metal mass concentrations. 

The XFM dilution and total flow meters were found to be biased during Phase I tests by 

about 5% as indicated below in Table 7. In addition, the XFM dilution flow meter was found 

to be biased by about 6% during Phase II tests (Table 8). These flow meter bias 

determinations were made using a NIST traceable DryCalTM primary flow sensor. Following 

Phase II, the DryCalTM was reevaluated by the manufacturer and was found to be within 

0.1% of the NIST standard. If a meter exhibited an average bias of more than 5%, a 

correction factor was applied to the recorded flows and subsequent calculations. Thus, 

correction factors of 5 to 7 % were applied only to the biased XFM flows as noted above. 

Method 301 Eval.: V1.0 Section 5.0 Quality Control and Assurance Page 37 of 75
Table 7: Flowmeter evaluation during Phase I. 

MFM DryCal

slpm slpm

A QAG Neb Air1 01/03/05 10.7 10.8 -0.8 No --

B XFM Total 10/20/04 1.32 1.25 5.6 Yes 0.95

C XFM Dilution 10/20/04 0.75 0.71 5.0 Yes 0.95

D XFM Extract 12/16/04 18.8 18.5 1.1 No --

E Overall Flow 12/16/04 110.4 113.3 -2.6 No --

F Xact (Samp, Dop) 03/03/05 0.71 0.70 0.8 No --

G Xact Dopant 03/03/05 0.20 0.20 -0.4 No --

Flow

Corr. for 

M301

Flows

Corr. 

Factor

Date % 

Diff.

Meter

Flow Check

Table 8: Flowmeter evaluation during Phase II. 

MFM DryCal MFM DryCal

slpm slpm slpm slpm

A QAG Neb Air

1 01/03/05 10.7 10.8 -0.8 3/9/2005 10.7 10.4 2.7 0.9 No --

B XFM Total 10/20/04 1.32 1.25 5.6 3/8/2005 1.60 1.57 1.9 3.8 No --

C XFM Dilution 10/20/04 0.75 0.71 5.0 3/8/2005 0.75 0.70 7.9 6.5 Yes 0.94

D XFM Extract 12/16/04 18.8 18.5 1.1 3/8/2005 16.8 16.2 3.2 2.2 No --

E Overall Flow 12/16/04 110.4 113.3 -2.6 3/25/2005 104.2 103.6 0.6 -1.0 No --

F Xact (Samp, Dop) 03/03/05 0.71 0.70 0.8 3/8/2005 0.71 0.70 1.1 0.9 No --

G Xact Dopant 03/03/05 0.20 0.20 -0.4 3/8/2005 0.20 0.21 -5.8 -3.1 No --

Date

% 

Diff.

Meter

Flow

Corr. for 

M301

Pre-test Post-test Flows

Corr.

Factor

Avg.

% 

Diff. Date

% 

Diff.

5.4 Xact-IAP 

The Xact-IAP was turned on prior to a test and continued operation until the test was 

completed. During Phase I and II tests, the Xact-IAP completed more than 730 runs and 9 

daily upscale/blank checks. Since no outliers were reported for the Xact-IAP and all flows 

met test plan objectives, all Xact-IAP data was accepted as reported. 

The CES Xact-IAP was calibrated on October 8, 2004, two months before the Phase I 

evaluation. Upscale and blank concentrations (Table 9) were determined in December 2004. 

Upscale concentrations were determined automatically by the Xact-IAP while blank 

concentrations were calculated based on measurements taken when spiking was not 

occurring and flue gas/ambient air was being measured. Overall, the Xact-IAP upscale 

concentrations were within 1% of the original calibration and the blank concentrations were 

below 2 μg/dscm for all elements. 

Method 301 Eval.: V1.0 Section 5.0 Quality Control and Assurance Page 38 of 75
Table 9: Upscale and zero drift during Phase I testing. 

Cr Cd Hg Pb Cr Cd Hg Pb 

Original Calibration 11/11/2005 3260 4300 2789 1983 0.00 0.00 0.00 0.00

Avg. Conc. Pre-Test 12/7/05 to 12/14/05 3250 4270 2784 1981 0.09 0.56 1.67 0.09

Avg. Conc. During Test 12/15/05 to 12/17/05 3270 4274 2789 1988 0.32 0.69 1.13 0.39

Pre-Test/Orig Cal. 12/8/05 to 12/14/05 1.00 0.99 1.00 1.00 -- -- -- --

Test/Original Cal. 12/15/05 to 12/17/05 1.00 0.99 1.00 1.00 -- -- -- --

Parameter Date

UPSCALE BLANK

Effective mass/region μg/dscm

The Xact-IAP XRF was calibrated using thin-film standards with NIST-traceable metal 

concentrations. These same standards were analyzed following Phase I and II tests with the 

results shown in Table 10. Overall, the concentrations for the metals remained within 5% of

the original calibration for all metals. The two independent Xacts, CES’ Xact for Phase I and 

Lilly’s Xact for Phase II, were also in good agreement, with concentrations within 5% of 

each other. 

For Phase II testing, the Lilly Xact-IAP was calibrated on January 28, 2005, one month prior 

to the field evaluation. Upscale and zero/blank drifts were determined in February 2005 and 

during the March tests with a summary shown in Table 11. Upscale concentrations were 

determined automatically by the Xact-IAP while blank concentrations were calculated based 

on measurements taken when spiking was not occurring and flue gas/ambient air was being 

measured. Overall, the Xact-IAP showed upscale and blank drifts below 4%, meeting the 

criteria found in proposed Performance Specification 1020. 

All mass and flow checks met QA precision requirements and no Xact-IAP outliers were 

present during the 460 runs of Phase II testing. No changes were made to the reported XactIAP concentrations and no Xact-IAP data was removed from the original data set. 

Table 10: Evaluation of NIST thin-film standards by the Xact-IAP. 

Pre-Test Post-Test Pre-Test Post-Test

10/8/2004 3/28/2005 1/28/2005 3/9/2005

 μg/cm2 μg/cm2 μg/cm2 μg/cm2

As 15207 12.50 12.17 0.97 11.92 12.52 1.05 12.33 12.22 1.01

Cd 15207 8.25 8.14 0.99 8.27 8.32 1.01 8.20 8.30 0.99

Cr 15090 12.16 12.08 0.99 12.23 13.20 1.08 12.12 12.72 0.95

Co 15207 14.39 14.34 1.00 13.71 14.31 1.04 14.36 14.01 1.02

Se 15207 18.55 17.70 0.95 19.41 20.44 1.05 18.12 19.92 0.91

Hg 15102 16.50 16.00 0.97 15.73 16.18 1.03 16.25 15.96 1.02

Ni 15090 10.66 10.47 0.98 10.16 10.71 1.05 10.56 10.44 1.01

Tl 15090 11.36 11.17 0.98 10.84 11.49 1.06 11.27 11.16 1.01

Sn 15090 14.41 14.32 0.99 13.86 13.92 1.00 14.36 13.89 1.03

Mn 15091 12.93 12.98 1.00 NM NM NM 12.96 NM NM

Cu 15091 11.77 11.79 1.00 NM NM NM 11.78 NM NM

Br 15091 4.82 4.76 0.99 NM NM NM 4.79 NM NM

Ba 15091 11.16 11.27 1.01 NM NM NM 11.21 NM NM

Ag 15091 12.39 12.65 1.02 NM NM NM 12.52 NM NM

Fe 15092 14.05 13.62 0.97 13.39 13.80 1.03 13.83 13.59 1.02

Zn 15092 7.82 7.60 0.97 7.45 7.64 1.03 7.71 7.55 1.02

Sb 15092 14.16 13.44 0.95 13.63 13.53 0.99 13.80 13.58 1.02

Pb 15092 13.36 12.93 0.97 12.73 13.13 1.03 13.14 12.93 1.02

Sr 15092 9.41 9.17 0.97 8.96 9.20 1.03 9.29 9.08 1.02

NM: Not Measured

Elem

NISTTraceable

Std No.

PHASE I: CES Xact PHASE II: Lilly Xact PHASE I VS. PHASE II

Post/ Pre 

Ratio

Ratio 

Post-Test/ 

Calib.

Avg

Phase I

Avg. Phase 

II PI/PII

Method 301 Eval.: V1.0 Section 5.0 Quality Control and Assurance Page 39 of 75
Table 11: Upscale and zero drift during Phase II testing.

Cr Cd Hg Pb Cr Cd Hg Pb

Conc. During Calibration 1/28/2005 1812 430 334 475 0.00 0.00 0.00 0.00

Avg. Conc. Pre-Test

1 1/29/05 to 3/1/05 1855 429 346 488 0.23 0.60 0.05 0.09

Avg. Conc. During Test

2 3/4/05 to 3/8/05 1857 427 346 493 0.42 0.71 0.71 0.71

PreTest Avg. Cal. Drift (%)1 1/29/05 to 3/1/05 2.4 -0.1 3.5 2.9 0.2 0.5 0.1 0.1

Test Avg. Cal Drift (%)

2 3/3/05 to 3/8/05 2.4 -0.6 3.5 3.8 0.3 0.6 1.2 0.2

1) Upscale avg. of 26 days. Blank avg. of 2078 runs. One blank run (2/15/05 16:30:00) removed due to possible 

stainless steel contamination from stack operations.

Parameter Date

2) Upscale avg. of 5 days. Blank avg. of 210 runs.

UPSCALE BLANK

Effective μg/region μg/dscm

6.0 Results and Discussion 

6.1 Overview 

This section summarizes the QAG, XFM, and Xact-IAP results from Phase I and II tests. In 

Phase I, the QAG was validated by demonstrating that it met all of the criteria required in 

Method 301 and the study plan. It generated a reference aerosol whose concentration for the 

five test metals was linearly related to the measured concentration over the range from zero 

to120 μg/dscm. The QAG demonstrated a precision and stability of about 2% and an 

efficiency of 100% within the experimental accuracy of the tests. These QAG validation 

results are summarized in Subsection 6.2 and discussed relative to the validation criteria in 

Subsection 6.2.2. 

In Phase II, the XFM and Xact-IAP were evaluated for accuracy, precision, and linearity 

while sampling flue gas spiked with a metals-containing reference aerosol from the QAG. 

The XFM and Xact-IAP met all Method 301 and test plan criteria, with precisions of better 

than 3% and a high linear correlation with the reference aerosol concentration. Phase II 

results for the XFM and Xact-IAP are summarized in Subsection 6.3 and discussed as they 

pertain to the validation criteria in Subsections 6.4 and 6.5. 

The complete set of test data and results is listed in Appendices I and J. Sample calculations 

are presented in Appendix K. 

6.2 QAG Validation 

6.2.1 Summary 

The primary objective of this phase was to validate the QAG by demonstrating that it met the 

criteria in Method 301 and those established in the test plan. During these tests, five metals 

(As, Cd, Cr, Pb, and Hg) were spiked at five concentration levels ranging from zero to over 

120 μg/dscm. The QAG reference concentrations were verified by 146 Xact-IAP and 26 

XFM analyses, with the three independent approaches in good agreement for all five metals 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 40 of 75
(Figure 12 and Table 12). All three independent approaches showed very good agreement 

over the wide range of concentrations and for all five metals. Overall, the XFM to QAG and 

the Xact-IAP to QAG ratios were both 0.98 ± 0.07 (Figure 13). This good agreement 

between the QAG reference concentration and the XFM and Xact-IAP measured 

concentrations indicates that the aerosol generation, transport and collection efficiencies were 

all essentially 100% within the uncertainty. 

The average XFM to QAG ratio for each of the five elements ranged from 0.94 to 1.00, while 

the Xact-IAP to QAG elemental ratios ranged from 0.96 to 1.01. The consistency of the 

XFM/QAG and Xact-IAP/QAG ratios for individual elements confirms the quantitative 

generation, transport and collection efficiency for each element. This suggests that no

significant fractionation of metals took place during these tests. This is particularly 

important because the metals represent both particle and vapor phases. Independent 

inductively-couple plasma (ICP) analyses of the solutions conducted by Chester LabNet21 of 

Tigard, OR confirmed the inter-element concentration ratios. It is important to note that in 

all Phase I and II tests, the two measurement methods were totally independent from the 

QAG reference aerosol generator as illustrated in Figure 2. 

0

20

40

60

80

100

120

140

160

QA

G

XF

M

XAC

T

QA

G

XF

M

XAC

T

QA

G

XF

M

XAC

T

QA

G

XF

M

XAC

T

QA

G

XF

M

XAC

T

HIGH MID2 MID1 LOW BLANK

Conc

e

ntration (

microgr/d

s

c

m)

CR

AS

HG

PB

CD

Figure 12: QAG-generated and XFM- and Xact-IAP-measured aerosol concentrations 

during Phase I tests. 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 41 of 75
Table 12: Comparison of Average QAG reference aerosol concentrations with XFM 

and Xact-IAP average measured concentrations (μg/dscm). 

Approach Metal Blank Low Mid 1 Mid 2 High

QAG CR 0.0 19.8 50.3 65.0 128

AS 0.0 18.7 46.5 59.6 128

HG 0.0 20.0 50.9 65.7 129

PB 0.0 19.9 50.8 66.2 129

CD 0.0 19.9 50.7 65.4 129

XFM No. 244 12 4

CR 0.1 20.2 42.2 65.5 130

AS 0.0 18.4 39.9 61.1 131

HG 0.7 18.7 42.3 63.7 120

PB 0.2 20.3 43.5 66.1 132

CD 0.5 21.1 46.0 65.7 128

XACT-IAP No. 11 23 22 67 23

CR 0.1 19.8 42.0 65.7 131

AS 0.0 18.6 40.7 62.1 134

HG 0.7 19.8 43.1 64.9 128

PB 0.2 19.5 42.8 65.5 131

CD 0.6 19.6 41.7 65.2 126

0.00

0.20

0.40

0.60

0.80

1.00

1.20

CR AS HG PB CD

Candidate Method/

Q

A

G

XFM/QAG

XACT/QAG

Figure 13: Ratio of XFM and Xact-IAP measured metal concentrations to the QAG 

reference aerosol concentration. 

6.2.2 Validation Criteria 

The QAG was validated by comparing the QAG-generated reference aerosol concentration to the 

aerosol concentration measured with the independent, analytically NIST-traceable XFM and 

Xact-IAP methods. The first step in this validation process was to demonstrate high relative 

transport and sampling efficiency for all test metals using metal concentration ratios. The second 

step was to demonstrate high absolute generation efficiency by comparing the QAG predicted 

reference aerosol concentration with the analytically measured aerosol concentration. The 

criteria used to demonstrate high relative transport and sampling efficiency were: 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 42 of 75
• Filter Ratio: More than 98% of two representative particulate metals (Cr and Pb) 

were required to be on the XFM’s front filter to demonstrate high particulate capture 

efficiency. 

• Metal Ratio: A high transport and sampling efficiency for vapor phase metals was assured 

by requiring the measured metal ratios be within 10% of the predicted QAG ratios. 

High absolute efficiency was then demonstrated by showing that the following criteria were 

met: 

• Efficiency: The overall (generation, transport, and sampling) QAG efficiency was 

required to be better than 80% for each metal as measured by the XFM and Xact-IAP. 

• Precision: The combined QAG and filter measurement method were required to have 

a precision of better than 10%. 

• Linearity: The QAG was required to be linearly related to the two candidate methods 

with a correlation of better than 0.85. 

6.2.3 Filter Ratio

The objective of this criterion was to demonstrate that essentially all (>98%) of the Cr (low 

volatility metal) and Pb (semi-volatile metal) were captured on the upstream PTFE XFM 

filter. Meeting this objective demonstrates >98% trapping efficiency for these two MACT 

metal categories. The high concentration XFM runs (21 – 24) were the most sensitive tests 

for this evaluation. The results for these runs are summarized in Table 13. The average 

percent lead on the first filter for these high concentration runs was 99.9%, with no 

measurable Pb or Cr found above their detection limit on the downstream filter. Similar 

results were observed in Phase II where none of the Cr was measured on the downstream

filter and the average Pb on the upstream filter was more than 99%. These high trapping 

efficiencies indicate that all of the Pb and Cr were captured by the XFM’s PTFE filter and 

that this test plan criterion was met. 

Table 13: Lead and chromium measured on the upstream PTFE filter as percent of 

total XFM lead and chromium (μg/filter). 

Upstream Downstream % Upstream Upstream Downstream % Upstream

Run No. μg/filter μg/filter μg/filter μg/filter μg/filter μg/filter

21 3.83 0.017 99.6 3.69 0.000 100.0

22 3.63 0.000 100.0 3.62 0.000 100.0

23 3.61 0.000 100.0 3.57 0.000 100.0

24 3.76 0.000 100.0 3.72 0.000 100.0

AVE 3.71 0.004 99.9 3.65 0.000 100.0

Lead Chromium

6.2.4 Metal Ratio 

The objective of this criterion was to demonstrate quantitative transport and sampling efficiency 

for the other three MACT metals (As, Cd and Hg) with the XFM and XACT-IAP. The metric 

for this comparison was defined as the ratio of the Pb-normalized solution concentration to the 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 43 of 75
Pb-normalized aerosol concentration for these metals. The reasoning is, if the Pb and Cr are 

quantitatively trapped by physical filtration as demonstrated above, and if the ratio of the other 

elements to Pb for the XFM and Xact-IAP is the same as in the nebulized solution, then the total 

sampling and transport efficiency for these metals as measured with the XFM filter cassette is 

the same as that for Pb, i.e., 100%. The acceptable range for this ratio was defined in the test 

plan as 0.9 to 1.1. 

The average metal ratios ranged from 0.99 to 1.05 for the XFM and 0.96 to 1.01 for the XactIAP. These metal ratio values are clearly within the range defined in the test plan. As such, this 

criterion was met. Meeting this and the preceding filter ratio criteria demonstrates that these 

metals do not fractionate during generation, transport and measurement of the reference aerosol. 

6.2.5 Efficiency 

Efficiency is defined as the ratio of the measured aerosol concentration to the QAG-predicted 

reference aerosol concentration expressed as a percent. This efficiency includes the QAG 

generation efficiency as well as the transport and measurement efficiencies. This total 

system efficiency for five metals measured at four concentration levels during Phase I QAG 

validation testing are listed in Table 14. The average QAG efficiency over all five metals 

and all four concentration levels was 97.8±2.3% and 97.7±1.8% as measured by the XFM 

and Xact-IAP, respectively. This represents all 24 XFM and 142 Xact-IAP individual 

efficiency determinations. The average QAG efficiency for each metal as measured with the 

XFM ranged from a low of 94% for Hg to a high of 100% for Cd. The average QAG 

efficiency for each metal as determined with the Xact-IAP ranged from a low of 96% for Cd 

to a high of 101% for As. In addition, the QAG efficiencies at low and high concentrations as 

determined with both candidate analytical methods were greater than 99%, which 

demonstrates that efficiency is independent of aerosol concentration in the range from 20 to 

125 μg/dscm. Thus, the average total system efficiency (generation, transport and 

measurement) is 98 ± 2%. However, the uncertainty in the reference aerosol concentration 

was about 4%. As such, the test plan criterion was met, the measured efficiency was 

essentially 100% within the uncertainty, and no efficiency correction factor is required. A 

complete set of results and sample calculations used for these efficiency determinations are 

presented in Appendices I and K. 

6.2.6 Precision 

QAG precision measurements are summarized in Table 15. This table lists the precision for each 

element as determined for each concentration level, and are based on sequential measurements. 

The average QAG precision over all elements and all concentration levels was better than 2.5%, 

significantly better than the required 10% criteria value. The high precision at each level 

demonstrates the ability of the QAG to maintain a constant concentration over extended periods 

of time. These precision results are based on data listed in Appendix I with sample calculations 

provided in Appendix K. 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 44 of 75
Table 14: QAG efficiencies determined during Phase I laboratory tests (%). 

RUN CR HG AS CD PB CR HG AS CD PB

1 100 97 103 100 98 102 101 101 98 100

2 100 99 102 98 98 93 99 100 99 93

3 101 97 103 98 98 98 94 101 104 99

4 99 98 104 103 97 99 97 100 98 100

5 101 100 107 101 99 101 100 105 99 98

6 103 99 103 98 101 101 100 103 104 101

7 103 99 107 102 101 102 98 101 98 102

8 104 101 107 100 100 101 97 104 99 99

9 100 99 103 98 99 102 90 103 100 102

10 101 99 104 97 98 103 96 104 102 98

11 103 99 103 98 101 109 102 111 105 109

12 100 99 104 102 99 98 92 97 98 98

13 83 86 88 76 83 83 80 83 89 87

14 84 84 87 84 85 85 84 88 87 87

15 82 85 87 84 85 83 86 85 99 85

16 84 84 88 85 85 84 83 87 88 84

17 98 101 100 96 96 102 95 96 105 100

18 103 98 102 103 95 104 93 102 106 99

19 101 102 101 100 99 100 93 98 103 105

20 99 96 96 96 101 104 94 98 111 104

21 103 100 106 97 100 101 100 101 99 104

22 102 99 104 100 102 103 95 104 100 103

23 102 100 104 96 103 100 88 102 98 100

24 103 100 106 99 102 102 90 103 101 102

Avg. 98.2 96.7 100.8 96.3 96.7 98.4 93.6 99.0 99.6 98.2

SD 7.0 5.6 6.5 6.9 6.0 7.3 6.0 6.8 5.5 6.5

%SD 7.1 5.8 6.5 7.2 6.2 7.4 6.4 6.9 5.5 6.6

Xact Determined QAG Efficiency XFM Determined QAG Efficiency

Table 15: Summary of QAG Phase I precision (%). 

Low Mid 1 Mid 2 High Low Mid 1 Mid 2 High

Runs

17-20

Runs 

13-16

Runs 

1-12

Runs 

21-24

Runs 

17-20

Runs 

13-16

Runs 

1-12

Runs 

21-24

(%) (%) (%) (%) (%) (%) (%) (%) (%) (%)

CR 1.3 1.0 2.3 0.9 1.4 1.7 1.0 1.1 0.3 1.0

AS 1.8 2.0 2.2 1.1 1.8 2.0 0.6 1.0 0.7 1.1

HG 0.8 2.1 2.8 3.7 2.3 2.0 1.0 0.7 0.6 1.1

PB 1.7 1.3 2.2 0.8 1.5 2.0 0.8 0.8 1.1 1.2

CD 2.3 4.1 1.9 1.0 2.3 2.5 3.4 1.5 1.2 2.1

AVG 1.6 2.1 2.3 1.5 1.9 2.0 1.4 1.0 0.8 1.3

ELEM

XFM XACT

AVG. AVG.

6.2.7 Linearity 

The test plan linearity criterion for validation acceptance was a correlation coefficient (r) 

value greater than 0.85. The QAG linearity was determined from a regression analysis for a 

plot of the measured aerosol concentration versus the QAG-predicted reference concentration 

over four concentration levels and a blank level. These plots for both the XFM and the XactIAP are illustrated in Figure 14 and Figure 15 (Note that only r

2

, coefficient of determination, 

values are listed in these plots). Since all of the r

2

 values are greater than 0.99, the r values 

are also greater than 0.99 and thus clearly meet the test plan acceptability requirement for r. 

Other linearity defining factors such as slope and intercept were also determined and are 

supportive. As can be seen from the plots in these two figures, the slopes ranged from a low 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 45 of 75
of 0.94 for Hg as measured with the XFM to a high of 1.05 for As measured with the XactIAP. The overall average slope was close to 1.00 verifying the strong agreement between 

these independent approaches. In addition, the intercepts were all below 2% of the full scale 

indicating a low blank bias. 

It is also important to note that none of the data was excluded in these linearity plots. In the 

case of the XFM, results from all 26 runs are included. The Xact-IAP ran continuously 

during the three days of Phase I tests and completed more than 270 runs, of which 146 were 

conducted while the QAG was in operation. All 146 Xact-IAP runs that corresponded to 

QAG runs are included in the plots shown in Figure 15. The Xact reported no outliers, 

experienced no mechanical problems, and had an effective uptime of 100% during Phase I. 

This strong linear relationship between the concentrations measured with the candidate 

methods and the independent QAG-generated reference aerosol concentration demonstrates 

the ability of the QAG to spike quantitatively over a wide range of concentrations. 

 CHROMIUM

y = 1.023x - 2.051

R2

 = 0.990

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

XFM Conc. (μg/dscm)

n=26

 MERCURY

y = 0.941x - 0.054

R2

 = 0.987

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

XFM Conc. (μg/dscm)

n=26

ARSENIC

y = 1.039x - 2.119

R2

 = 0.993

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

XFM Conc. (μg/dscm)

n=26

CADMIUM

y = 0.995x - 0.134

R2

 = 0.995

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

XFM Conc. (μg/dscm)

n=26

LEAD

y = 1.030x - 2.489

R2

 = 0.992

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

XFM Conc. (μg/dscm)

n=26

Figure 14: Phase I QAG linearity plots as determined by the XFM. 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 46 of 75
CHROMIUM

y = 1.019x - 1.421

R2

 = 0.993

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

Xact Conc. (μg/dscm)

n = 146

ARSENIC

y = 1.047x - 1.600

R2

 = 0.993

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

Xact Conc. (μg/dscm)

n = 146

MERCURY

y = 0.979x - 0.542

R2

 = 0.993

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

Xact Conc. (μg/dscm)

n = 146

CADMIUM

y = 0.983x - 0.762

R2

 = 0.990

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

Xact Conc. (μg/dscm)

n = 146

LEAD

y = 1.002x - 1.335

R2

 = 0.992

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

Xact Conc. (μg/dscm)

n = 146

Figure 15: Phase I QAG linearity plots as determined with the Xact-IAP 

6.2.8 QAG Validation Summary and Recommendation 

Phase I results as they pertain to the QAG validation criteria are summarized below in Table 

16. It is clear from this summary that all QAG validation criteria established in the test plan 

were met. As such, the QAG should be approved as a reference aerosol generator that can be 

used for validating emission measurement instruments and methods including CEMS, IAP, 

alternatives to reference methods and conditional methods. 

Table 16 Summary of Phase I QAG validation results. 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 47 of 75

Criteria Acceptable Resultsa Met Criteria

No. Runs >9 >25 Yes

Filter Ratio (% Front) >98 >99 Yes

Metal Ratio (Sol./Aer.) 0.9 - 1.1 0.95 - 1.01 Yesb

Efficiency (%) >80 94 - 100 Yes

Precision (%) <10 <4 Yes

Linearity - Corr. Coef. ( r ) >0.85 >0.99 Yes aXFM and Xact results for all five elements

 bConfirmed with independent ICP analysis results
6.3 XFM and Xact-IAP Validation Overview 

The primary objective of Phase II testing was to validate the XFM and Xact-IAP by 

demonstrating that they met the conditional method criteria established in the test plan. The 

QAG, validated in Phase I, was used in this phase to spike a NIST-traceable reference 

aerosol into incinerator flue gas. As such, it is assumed that the characteristics of the QAG 

reference aerosol generator are those demonstrated in Phase I; i.e., 100% generation and 

transmission efficiency. Validation criteria and acceptance values are the same for both the 

XFM and the Xact-IAP, and include bias, precision and linearity. Phase II results and test 

conditions are listed in Appendix J and sample calculations are provided in Appendix K. The 

general results from Phase II testing for both the XFM and Xact-IAP are summarized below. 

The detailed XFM results as they pertain to the specific validation criteria are presented in 

Subsection 6.4 while the results for the Xact-IAP are presented in Subsection 6.5. 

It needs to be emphasized that: 

• The QAG, XFM and Xact-IAP were independent of each other in Phase II as they 

were in Phase I. That is, the QAG was not used to calibrate the XFM and the Xact as 

is commonly accepted practice in EPA instrumental analyzer procedures such as 

Methods 6C and 7E where the same gas standard used to calibrate the instrument is 

used to spike the stack gas. The XFM and Xact-IAP results are based on NISTtraceable thin film standards. 

• The Xact instrument used in Phase II was not the same one used in Phase I. As such, 

the Xact used in Phase II was calibrated independently of the Phase I Xact. 

• Results from all of the runs were used for the data analysis. In some cases, data from

some runs could have been excluded, which would have resulted in a significant 

improvement in the agreement between the methods. However, even when all the 

data is included, all of the validation criteria are still met. 

Phase II testing consisted of spiking stack gas with a QAG-generated reference aerosol 

containing five elements (As, Cd, Cr, Hg, and Pb) at three concentrations ranging from about 

20 to 120 μg/dscm and at a blank level. The concentration of the QAG-spiked stack gas and 

the measured XFM and Xact concentrations are summarized in Table 17 and Figure 16. 

Concentrations reported by the XFM and the Xact-IAP were in good agreement with each 

other and with the reference aerosol concentration at all three spiked concentrations and the 

blank. Overall, the XFM to reference aerosol concentration ratio was 1.02 ± 0.07 while the 

Xact-IAP ratio was 0.93 ± 0.07. 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 48 of 75
Table 17: Summary of XFM and Xact-IAP measured concentrations and QAG-spiked 

flue gas concentrations Phase II (μg/dscm). 

Approach Avg.

Blank

Avg.

Low

Avg.

Mid

Avg.

High

Number 4 4 6 12

CR 0.0 21.3 46.2 108

AS 0.0 21.2 46.2 108

HG 0.0 21.2 45.9 108

PB 0.0 21.2 45.9 108

QAG

CD 0.0 21.2 46.2 107

CR 0.2 22.9 41.8 112

AS 0.0 21.7 41.0 114

HG 0.3 22.7 40.2 111

PB 0.9 22.6 40.6 115

XFM

CD 0.3 22.3 43.1 113

CR 0.0 20.0 37.8 103

AS 0.1 21.0 39.9 107

HG 0.2 18.5 35.2 95

PB 0.0 18.8 37.9 108

XACT

CD 0.3 21.5 39.9 106

Method 301 Reported Concentrations

0

20

40

60

80

100

120

140

QA

G

XACT

XFM

QA

G

XACT

XFM

QA

G

XACT

XFM

QA

G

XACT

XFM

HIGH MID LOW BLANK

Conc. (

μg/ds

c

m)

CR

AS

HG

PB

CD

Figure 16: Comparison of the XFM and Xact-IAP measured concentrations with the 

QAG-spiked flue gas concentrations during Phase II testing. 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 49 of 75
6.4 XFM Validation 

6.4.1 Bias 

The twelve high concentration runs were used to calculate bias with results shown in Table 

18. Overall, there is very good agreement between the XFM measured concentration and the 

reference aerosol concentration with an average bias over all metals of 4.8±1.3%. Mercury 

exhibited the lowest bias at 3.1% and Pb the highest at 6.3%, which are all below the 10% 

acceptance criterion.Thus, the XFM meets the required bias criteria for all metals tested. 

Table 18: Summary of XFM Phase II bias values for each metal tested (μg/dscm).

Reference

Run Concentration CR AS HG PB CD CR AS HG PB CD

1 108 113 112 109 114 113 5.36 4.40 1.38 5.80 5.22

2 108 114 117 108 118 118 6.54 9.00 -0.21 9.57 10.46

3 108 111 113 114 110 110 2.66 5.29 5.52 2.20 2.48

4 108 112 113 104 113 113 3.80 4.75 -3.97 4.63 4.79

5 108 111 112 109 120 114 3.38 3.76 0.67 11.58 5.91

6 108 114 116 117 116 112 5.63 8.17 8.66 8.29 4.40

7 108 110 112 113 111 112 2.30 4.39 4.52 3.34 4.37

8 108 104 110 117 112 104 -3.63 2.15 9.13 3.89 -3.58

9 108 109 110 109 109 113 0.70 2.49 0.69 0.61 4.96

10 108 116 114 108 124 113 8.50 6.40 0.09 15.90 5.23

11 108 117 121 120 117 119 9.58 13.06 11.44 9.20 11.16

12 108 113 116 111 115 117 5.30 7.70 2.84 6.86 8.87

AVG 108 112 114 111 115 113 4.18 5.96 3.40 6.82 5.35

SD 3.5 3.1 4.6 4.3 3.8 3.54 3.10 4.56 4.34 3.85

XFM SD 2.50 2.20 3.22 3.07 2.72 2.50 2.20 3.22 3.07 2.72

XFM SDM 0.72 0.63 0.93 0.89 0.79 0.72 0.63 0.93 0.89 0.79

% Bias 3.87 5.52 3.14 6.32 4.96

XFM XFM Bias (XFM-Reference)

6.4.2 Precision 

The average XFM precision (PRSD) based on the XFM standard deviations (XFM SD) listed 

above in Table 18 was 2.5±0.4% and ranged from a low of 2.0% for As to a high of 3.0% for 

Hg. This represents a significant improvement over the currently accepted precision for 

Reference Method 29 and well within the 10% criterion acceptance value required for 

validation. 

6.4.3 Linearity 

The key linearity criterion for the XFM is a correlation coefficient (r) value greater than 0.85. 

To test the linearity of the XFM, the flue gas was spiked with all five metals at four reference 

aerosol concentrations using the QAG. The results from these five tests are plotted in Figure 

17. A least-squares regression analysis of all 26 data points provided the correlation 

coefficient as well as the slope and intercept for each metal. All of the correlation 

coefficients were greater than 0.99, easily exceeding the requirement to be greater than 0.85. 

The slopes averaged 1.06±2 and ranged from a low of 1.04 for Hg to a high of 1.07 for As 

and Pb. The intercepts were less than 3% of the full scale indicating low blank values. 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 50 of 75
6.4.4 XFM Summary 

Phase II XFM results are summarized in Table 19. This table shows that all the acceptance 

criteria were met for all of the five MACT metals tested. As such, it is recommended that the 

XFM be approved as a conditional method.

Mercury

y = 1.036x - 1.803

R2

 = 0.991

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

XFM (μg/dscm)

n=26

Chromium

y = 1.042x - 1.605

R2

 = 0.994

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

XFM (μg/dscm)

n=26

Arsenic

y = 1.067x - 2.716

R2 = 0.994

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

XFM (μg/dscm)

n=26

Lead

y = 1.068x - 2.079

R2

 = 0.991

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

XFM (μg/dscm)

n=26

Cadmium

y = 1.054x - 1.613

R2

 = 0.994

0

20

40

60

80

100

120

140

0 20 40 60 80 100 120 140

Reference Conc. (μg/dscm)

XFM (μg/dscm)

n=26

Figure 17: Phase II XFM linearity.

Table 19: Summary of Phase II XFM validation test criteria and results. 

Criteria Acceptable Resultsa Met Criteria

No. Runs >9 26 Yes

Bias Corr. Factor 0.80 - 1.2 0.94 - 0.97 Yesb

Precision (%) <10 <3 Yes

Linearity - Corr. Coef. ( r ) >0.85 >0.99 Yes a

XFM results for all five elements

b

Confirmed with independent ICP analysis results

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 51 of 75
6.5 Xact-IAP Validation 

6.5.1 Xact-IAP Overview 

The Xact multi-metals analyzer, when permanently installed, acts as a CEMS, whereas if it is 

installed for short term emission measurements (days to weeks), it is part of an IAP. It is this 

latter application that is the focus of this subsection. Two different Xact instruments were 

used during Phase I (CES Xact) and Phase II (Lilly Xact) tests, requiring two independent 

calibrations using NIST traceable thin-film standards. 

All of the validation criteria were met for all of the elements. However, as discussed below, 

a key issue is whether or not to apply a bias correction factor if a significant bias is observed. 

6.5.2 Bias 

The twelve high concentration runs (nominal concentration of 110 μg/dscm) were used to 

calculate bias. These bias results along with the measured Xact-IAP results and the reference 

aerosol concentration are listed in Table 20 along with standard deviations and percent bias. 

As can be seen from this table, there is very good agreement between the Xact-IAP measured 

concentrations and the reference aerosol concentration for all the elements. 

Method 301 requires an evaluation for bias in the candidate method in order to determine if a 

correction factor is required1

. For Phase II tests, bias was determined by evaluating the 

systematic differences between the reference aerosol method and candidate method relative to 

the uncertainty in the methods. Bias was considered to be significant when it exceeded two times 

the combined uncertainty in the reference generation and candidate measurement method at the 

95% confidence level. Since the combined Xact-IAP and QAG uncertainty is on the order of 5%, 

the significance criteria resulted in a 10% threshold for determining the significance of bias. Four 

of the elements measured by the Xact-IAP – As, Cd, Cr, and Pb – had biases of less than 2%, 

well within the uncertainty of the methods and below the threshold of significance. For this 

reason, no correction factor is required for As, Cr, Cd, or Pb. The average percent bias for Hg 

was 12.3±1.0%. This bias is clearly above the 10% level of significance for the QAG/Xact-IAP, 

but well within the acceptable range of 30% specified in Method 301; particularly with the high 

precision (±1%) observed for this bias. Although a correction might be considered necessary, it 

is not recommended in this case as is discussed in detail in the following subsection. 

6.5.3 Mercury Bias Correction Factors 

As noted above, a significant, systematic bias greater than 10% was observed in the Hg 

results from Phase II tests of the Xact-IAP. However, even though the percent bias (12.3%) 

was greater than 10%, it is recommended the Xact-IAP be approved without the requirement 

of a bias correction factor, since half of the bias was due to a post-test identified calibration 

error. This error was identified by evaluating the Hg/Pb sensitivity (calibration) ratio, which 

is used to obtain NIST traceability through the Pb concentration in NIST SRM 1833. This 

ratio should have been 0.93, but was instead 0.99. If this 6% error had not existed, the XactIAP Hg results would have been 6% higher and the Hg percent bias would have been about 

6%, well within the required 10%. 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 52 of 75
Table 20: Comparison of Xact-IAP with QAG reference concentrations and bias 

(μg/dscm). 

Ref.

Run Conc. CR AS HG PB CD CR AS HG PB CD

1 108 105 106 94 102 106 -3.07 -2.11 -14.44 -5.65 -1.57

2 108 103 106 96 104 105 -5.26 -2.01 -12.44 -3.84 -2.51

3 108 102 106 95 105 106 -6.14 -1.88 -12.74 -3.17 -1.93

4 108 102 105 94 107 105 -5.77 -2.75 -14.24 -1.02 -2.78

5 108 100 106 94 105 105 -7.94 -2.06 -14.22 -2.55 -2.62

6 108 103 107 94 110 105 -4.92 -1.45 -14.19 1.76 -2.26

7 108 103 107 95 111 109 -5.08 -1.33 -13.18 2.98 1.61

8 108 103 107 94 109 107 -4.64 -1.28 -13.68 1.44 -0.54

9 108 105 108 95 110 106 -2.54 0.05 -13.08 1.65 -1.41

10 108 104 107 94 109 105 -4.10 -1.02 -14.12 1.37 -2.89

11 108 107 110 97 111 107 -1.07 2.27 -11.29 2.99 -1.13

12 108 105 109 97 112 106 -2.44 1.43 -11.32 3.74 -1.30

AVG 108 103 107 95 108 106 -4.41 -1.01 -13.25 -0.02 -1.61

SD 1.9 1.5 1.1 3.1 1.3 1.89 1.52 1.12 3.10 1.25

Xact SD 1.34 1.07 0.79 2.19 0.89 1.34 1.07 0.79 2.19 0.89

Xact SDM 0.39 0.31 0.23 0.63 0.26 0.39 0.31 0.23 0.63 0.26

% Bias -4.09 -0.93 -12.27 -0.02 -1.49

Xact XACT-QAG

This type of error did not appear in Phase I testing using CES’ Xact which had been 

calibrated with the appropriate Hg/Pb sensitivity ratio. For Phase I, the Hg bias was less than 

2% for the 12 runs near the emission limit and was less than 4% averaged over all of the 146 

Xact-IAP measurements. 

This error is readily correctable within the Xact software and should not be present in future 

tests. As such, it is recommended that no correction factor be made to future Xact-IAP 

mercury measurements. 

6.5.4 Precision 

The average Xact-IAP precision (PRSD) based on the Xact-IAP standard deviations (Xact SD) 

listed above in Table 20 was 1.3 ± 0.6% and ranged from a low of 0.8% for Hg to a high of 2.0% 

for Pb. This represents a significant improvement over the currently accepted precision for 

Reference Method 29 and substantially less than the required validation acceptance limit of 10%. 

6.5.5 Linearity 

The Xact-IAP ran continuously during the five days of Phase II tests and completed more 

than 450 runs, of which 192 were conducted while the QAG was operated. The Xact-IAP 

experienced no mechanical problems during Phase II testing and had an effective uptime of 

100%. To test the linearity of the Xact-IAP, the incinerator flue gas was spiked with all five 

metals at four reference aerosol concentrations using the QAG. The results from these tests, 

including a series of blank runs, are plotted in Figure 18. A least-squares regression analysis 

of all 192 data points provided the correlation coefficient as well as the slope and intercept 

for each metal (The coefficient of determination, r

2

, is listed on the figures.) All of the 

correlation coefficients ® were greater than 0.99, easily exceeding the required lower limit 

value of 0.85. 

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 53 of 75
Chromium

y = 0.952x - 1.129

R2

 = 0.994

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Reference Conc. (μg/dscm)

Xact Conc. (μg/dscm)

n=192

Mercury

y = 0.870x - 0.825

R2

 = 0.996

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Reference Conc. (μg/dscm)

Xact Conc. (μg/dscm)

n=192

Arsenic

y = 0.983x - 1.037

R2

 = 0.995

0

20

40

60

80

100

120

0 20 40 60 80 100 12

Reference Conc. (μg/dscm)

Xact Conc. (μg/dscm)

n=192

0

Lead

y = 0.991x - 1.924

R2

 = 0.992

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Reference Conc. (μg/dscm)

Xact Conc. (μg/dscm)

n=192

Cadmium

y = 0.971x - 0.845

R2

 = 0.993

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Reference Conc. (μg/dscm)

Xact Conc. (μg/dscm)

n=192

Figure 18: Phase II Xact linearity. 

6.5.6 Xact-IAP Summary and Recommendations 

The Phase II Xact-IAP results are summarized in Table 21 and Table 22. Table 21 shows 

that all the acceptance criteria were met for all of the five MACT metals tested. Only one 

metal, Hg, might have required a bias correction factor. However, it is recommended that the 

procedure be approved without a correction factor because, as discussed in Subsection 6.5.3, 

the significant bias observed was due to a calibration error, was not observed in Phase I, and 

should not happen in future applications because of changes made to the software and SOP. 

Table 22 compares the Xact-IAP results from Phase II with proposed Performance 

Specification 10 for multi-metals CEMS. It is clear from the comparison, that all of the 

criteria in this proposed performance specification were met.

Table 21: Summary of Phase II Xact results. 

Criteria Acceptable Resultsa Met Criteria

No. Runs >9 192 Yes

Bias Corr. Factor 0.80 - 1.2 1.00 - 1.14 Yes

Precision (%) <10 <3 Yes

Linearity - Corr. Coef. ( r ) >0.85 >0.99 Yes a

Xact-IAP results for all five elements

Method 301 Eval.: V1.0 Section 6.0 Results and Discussion Page 54 of 75
Conclusions and Recommendations

Table 22: Comparison of Xact Phase II results with proposed PS-10 criteria. 

UNITS XACT PS-10

Criteria

MET PS-10 

Criteria

Uptime % 100 NA Yes

Metals Measured During Testing -- 5 2 Yes

Response Time min. 45 240 Yes

Reporting Time min. 15 60 Yes

Upscale/Calibration Drift % <4 5 Yes

Zero/Blank Drift % <2 5 Yes

Precision (PRSD) % <4 15 Yes

No. of Measurements -- 20 9 Yes

Relative Accuracy % 2-16 20 Yes

CRITERIA

* Comparison to EPA Method 29's typical precision of 15%. 

7.0 Range of Method Application 

7.1 Overview 

The results from the preceding section clearly demonstrate the ability of the XFM and XactIAP to accurately and precisely quantify metals in stack emissions over a broad range of 

concentrations, and that these methods are applicable to the quantitative measurement of the 

five validated metals in hazardous waste incinerators. The question then arises as to 

What other source categories and elements is this technology applicable? 

The answer to this question lies in how key features of the sampling and analysis procedures 

depend on and respond to changes in emission characteristics associated with different source 

categories. The EPA suggests in Method 301 that this might be addressed in part by 

conducting a series of ruggedness tests, which are laboratory tests of a method’s sensitivity to 

key method variables1

,

29, 30. This type of evaluation of the XFM and Xact-IAP was conducted 

during Phase I laboratory testing. In addition, a substantial body of previous laboratory and 

field test data on this reactive-filter based technology is also available that supports the 

general applicability of these methods to most sources and elements. 

The above tests and data are summarized in this section along with key aspects of the XFM 

and Xact-IAP methods, and relative characteristics of emissions. The objective of this 

review is to demonstrate that these methods should be considered generally applicable to a 

wide range of emissions and elements including those from regulated sources. This review is 

presented in the following subsections: 

• Method Applicability (7.2) 

• Key Sampling and Analysis Features (7.3) 

• Key Emission Characteristics (7.4) 

• Filter Trapping Efficiency for Vapor Phase Metals (7.5) 

• Applicable Concentration Range (7.6) 

Method 301 Eval.: V1.0 Section 7.0 Page 55 of 75
Conclusions and Recommendations

• Deposit Stability (7.7) 

• Moisture (7.8) 

Page 56 of 75

(7.9)

.10)

Gases (7.12)

The x L and supporting reports are provided in

Appendix M. The conclusion of this review is that there is a substantial body of information 

quirements of Method 301, it is valid for 

the source tested, and may be applicable to the specific source category. Method 301 

iteria

re

trations.

ntative sample of stack gas through a filter 

matrix where metals are concentrated prior to analysis. The XFM draws the stack gas 

and,

(C)

ck

• Holding Times

• Other Related Tests (7

• Applicable Elements (7.11)

• Sensitivity to Reactive Stack

details of this review are presented in Appendi

about the chemistry and physics of the methods and emissions as well as specific test data 

covering some of the more challenging of conditions that strongly supports the extension of 

these methods to other regulated source categories and elements. 

7.2 Criteria for Candidate Method Applicability 

It is clear that when a candidate method meets the re

recommends that additional test data be submitted to extend the applicability of the candidate 

method to other source categories. This recommendation, however, does not specify cr

that can be used to evaluate possible extension of a method’s applicability when direct test 

data is not available. For the following discussion, it will be assumed that the candidate 

methods will be applicable to an untested source category if differences in emission 

characteristics between sources tested and candidate source emissions are such that they a

unlikely to contribute significantly to imprecision and bias in measured metal concen

7.3 Key Sampling and Analysis Features 

Both the XFM and Xact-IAP draw a represe

through an upstream PTFE filter that removes PM from a gas stream and then through a

downstream reactive filter that traps vapor phase metals. The Xact-IAP, on the other h

uses a single reactive filter to trap both the PM and vapor phase metals. Both methods 

measure the mass of each metal deposited on the filter(s) using XRF analysis procedures 

based on EPA’s IO Compendium Method 3.314. The concentration of metal in stack gas

is calculated by dividing the mass of metal in the filter(s) deposit (M) by the volume of sta

gas (V) that passed through the filter(s). That is; 

V C = M Equation 26 

Key sampling and analy

of the metal mass and volume determinations. Consequently, a method will likely be 

me

sis features are thus those that contribute to the quantitative accuracy 

applicable to a particular source emissions category if the differences in stack gas 

characteristics are such that they do not significantly contribute to inaccuracies in volu

and mass measurements. 

Method 301 Eval.: V1.0 Section 7.0
Conclusions and Recommendations Page 57 of 75

as

orrosive species such as acids, SO2, etc. prior to volume 

determination. This dilution and extensive conditioning of the stack gas prior to volume 

the 

n

ciency 

Ag , and control such

sam in e, dew point, and PM concentration in their optimal range. 

As such, the method’s sensitivity to specific stack gas characteristics is significantly reduced 

tion

k

PM are

ell established and generally accepted to be greater than 99% are not expected to be 

l

Characterization of emissions depends on such factors as source type (combustion, process, 

cted or fugitive) and type of controls (filtration, 

electrostatic precipitators, scrubbers, absorbers, reactive, etc.). However, from the method 

nto

In the case of volume determination, both methods dilute, cool, filter, and dry the stack gas

well as denude the gas of c

determination makes it relatively insensitive to differences in stack gas characteristics. Thus, 

if differences in stack gas characteristics are to significantly impact the accuracy of

measured aerosol concentration, it must be through the metal mass determination. 

Accurate determination of metal mass depends on two key factors, which may depend o

stack gas characteristics: 

• XRF analytical determination of metal mass in the filter deposit 

• Filter trapping effi

ain it is important to note that both methods use dilution to maintain

pl g conditions as temperatur

even for these two factors. For example, when applying these methods, the applications 

engineer is directed to adjust non-critical parameters within specified limits such as dilution 

ratio and sampling time to optimize the method for a particular application. Furthermore, 

since there is no direct interaction between stack gas and the analysis, the XRF determina

of metal mass in the filter deposit is only indirectly dependent on the characteristics of the 

stack gas through how the stack gas impacts the characteristics of the deposit on the filter.

Other than the analyte metals of interest, the only species deposited on the filter are nonanalyte PM species, the total mass of which is controlled through the method application by

selecting optimal sampling times and dilution ratios. None of the major components of stac

gas are trapped on the filters and cannot therefore interfere with the XRF analysis. 

For this reason, the only factor that might be sensitive to stack gas characteristics is the filter 

trapping efficiency for PM and vapor phase metals. Filter trapping efficiencies for

23,31

w

dependent on differences in stack gas characteristics. As such, filter trapping efficiency for 

vapor phase metals is the key factor that might be impacted by stack gas characteristics. The

primary focus of the next two sections is on the potential dependence of vapor phase meta

trapping efficiency on flue gas conditions and the available data showing the range within 

which the method has demonstrated acceptable quantitation. 

7.4 Key Emission Characteristics 

fuel type, etc.), type of emissions (du

applicability evaluation perspective, the characteristics of emissions that are most relevant 

are those defined in terms of their physical (primarily temperature) and chemical 

(composition) characteristics. Emissions are generally composed of varying amounts of air

(N2, O2), combustion products (NOx, SOx, CO2, CO, H2O, etc.), contributions from controls

(Na, Ca, H2O, NH3, etc.) and various process species, and can be further divided i

categories such as PM, reactive and non-reactive gases, acid vapors, etc. 

Method 301 Eval.: V1.0 Section 7.0
Conclusions and Recommendations Page 58 of 75

hen

ists, however, for

rs and

te,

t

ce

, and

conducted

Tippe, IN Boardman, OR Midwest Tooele, UT

As discussed above, the filters used by the XFM and Xact-IAP have a high PM metals 

trapping efficiency regardless of the stack gas physical and chemical characteristics w

sampling within the conditions specified by their SOPs. Some potential ex

the vapor phase collection efficiency to be impacted by the stack gas physical paramete

chemical composition. For both the XFM and Xact-IAP, the sampling temperature, flow ra

and pressures are controlled by the operator within the bounds of the SOP and are 

independent of the source type. Thus, the key characteristics of emissions that might impact 

the reactive filter’s trapping efficiency are the sampling interferences caused by reactive 

gases such as NOx, SOx, NH3, Cl2, HCl, HNO3, and H2SO4. Although this list is no

complete, it does represent the more abundant and more reactive species likely to be present 

at varying concentrations in most stacks of regulatory interest. Oxygen was not listed, sin

it is expected to be present in most emissions at ambient concentrations (21%) or less

laboratory tests in Phase I demonstrated high trapping efficiency at the highest likely O2

concentration. Potentially interfering reactive gases are listed below in Table 23 along with 

measured stack gas concentrations during supplemental testing discussed below and in 

Appendix L. Although this list is incomplete, the concentrations and conditions are 

representative of these sources and cover a broad range of concentrations and temperatures. 

Table 23. List of stack conditions for which Xact-IAP and XFM tests have been

Phase II CFPP-CES CFPP-EPA HWC - TEAD Species

CO, dry ppm 14 < 10 NA 10

O2, dry % 11 4.5 12-15 14-15

CO2, dry % 6 12.5 4-8 5

NOx, dry ppm 110 200 70 1200

SO2, dry ppm ND 225 20-35 10

HCl (equiv.), dry ppm 2 NA NA 50

H2O % 9 10 15-20% 5

PM @ 7% O2 mg/dscm 4 27 NA 10

Temp °F 170 300 160 450

NA: Not Available CFPP-CES: CES sponsored collection efficiency test at PGE CFPP

ND: Not Detected CFPP-EPA: EPA sponsored test of Hg monitors

HWC-TEAD: US Army sponsored tests at demiliterization HWC

7.5 Filter Trapping Efficiency for Vapor Phase Metals 

The Clean Air Act lists 11 metals as air toxics: Sb, As, Be, Cd, Cr, Co, Pb, Mn, Hg, Ni and 

. tely in the vapor phase at the

operating temperature of the Xact-IAP and XFM (180°F). For this reason, Hg is the most 

tests

Se10 Of these metals, Hg is the only one that is predomina

challenging to trap by filtration and most sensitive indicator of vapor phase metal trapping 

efficiency. Over the past several years, three series of Hg trapping and relative accuracy

have been conducted in addition to Phase I and II tests described in the first part of this 

report. Whereas Phase II tests demonstrated high Hg trapping efficiencies under conditions

more representative of emissions from modern hazardous waste incinerators, these additional 

tests focused on emissions from coal-fired boilers. The supplemental tests were more 

challenging in part because of their lower Hg concentrations (<10 μg/dscm) but also because

of the presence of higher concentrations (Table 23) of potentially interfering species such as 

Method 301 Eval.: V1.0 Section 7.0
Conclusions and Recommendations Page 59 of 75

by

d

coal-fired power plant in Boardman, OR to 

ev s under a variety of sampling conditions. 

For these tests, mercury was injected into either laboratory air or stack effluent and the 

ry

into the

an EPA sponsored evaluation of mercury 

me er plant5. These tests, conducted in July

2003, compared simultaneous XFM and Ontario-Hydro Reference Method (OH) measured 

based

NOx, SO2, SO3, NH3, PM, etc. The first series of tests discussed below were sponsored

CES and were conducted both in the laboratory and at a coal-fired utility boiler to define the 

concentration range of applicability for the reactive filters. The second and third series of 

tests were sponsored by the EPA and the army, and focused on relative accuracy of the 

measurements at coal-fired boiler emissions. In the following summaries, an acceptable 

relative accuracy when compared to an EPA authorized reference method will be taken to 

imply an acceptable vapor phase trapping efficiency. The supplemental tests summarize

below are discussed in more detail in Appendix L and supporting reports are provided in 

Appendix M. 

7.5.1 CES Sponsored Trapping Efficiency Tests 

A series of tests were conducted at CES and a 

aluate the Hg trapping efficiency of reactive filter

trapping efficiency evaluated with the XFM using two reactive filters in series. The mercu

trapping efficiency was determined by comparing the Hg trapped on the upstream filter with 

the total mercury collected on both filters. Mercuric chloride laboratory tests in the 

temperature range between 100 and 212°F exhibited capture efficiencies greater than 99% for

concentrations ranging in excess of 800 μg/dscm with sampling times up to one hour. 

Similar tests were conducted at the coal-fired power plant using elemental Hg spiked

stack gas. In this case, the elemental Hg trapping efficiency was greater than 99% for 

concentrations ranging up to 300 μg/dscm.

7.5.2 EPA Sponsored Relative Accuracy Tests 

CES tested the XFM filter approach during 

asurement methods at a Midwest coal-fired pow

mercury concentrations between 1 and 6 μg/dscm. The accuracy of the reactive filter

methods at low concentrations was demonstrated using an in-stack version of the XFM. A 

total of 12 two-hour OH runs were conducted. For each OH run, two simultaneous 50

minute, in-stack XFM samples were collected by CES. For these tests, the XFM and the OH

results were in good agreement with a relative accuracy of 11% for the nine valid runs, well

within the 20% criteria for conditional methods specified by EPA’s proposed Performance 

Specification 1232. Three of the 12 OH test runs were omitted from comparison by the EPA 

contractors. Two were omitted because of poor OH replication (>40% difference) and one 

was omitted due to a plant upset. The remaining nine runs were used for comparison, the 

results of which are plotted in Figure 19. The high correlation of these results and low 

relative accuracy demonstrates the effectiveness of the reactive filter approach for trapping

and quantifying Hg concentrations between 1 and 6 μg/dscm. 

Method 301 Eval.: V1.0 Section 7.0
Conclusions and Recommendations

Mercury

y = 0.908x + 0.152

R2

 = 0.962

0

1

2

3

4

5

6

012 3456

OH Conc. (μg/dscm)

XFM Conc. (μg/dscm)

n= 9

RA= 11%

Figure 19. Comparison of Hg concentrations determined by XFM and Ontario Hydro 

reference method at a coal-fired power plant.

7.5.3 US Army Sponsored Relative Accuracy Tests 

The U.S. Army sponsored a series of tests in January 2005 to evaluate a mercury-optimized 

Xact at a coal-fired power plant

33. For these tests, mercury and arsenic were spiked into stack 

gas followed by simultaneous Hg and As measurements using the Xact and Reference 

Method 29. The results from these tests demonstrated relative accuracies of 17% for these 

two elements, meeting the proposed 20% criteria proposed for Performance Specification 10. 

7.5.4 Summary of Trapping Efficiency Sensitivity to Reactive Stack Gases 

Unlike the physical filtration mechanism used to collect particulate metals, vapor phase 

metals react with the chemically treated filter and bind to the filter substrate. Some stack gas 

constituents could potentially interfere with this process. However, the more abundant stack 

gas species such as N2, O2, CO2, CO, and vapor phase H2O are relatively inert, are not 

trapped on the reactive filter, and test results indicate that they do not influence the filter 

trapping efficiency. Oxidants within the gas stream such as Cl2 have been shown to improve 

the vapor phase collection efficiency for Hg. Other minor stack gas components such as 

NOx, SOx, and NH3, have the potential to interfere with vapor phase Hg trapping efficiency. 

However, this potential to interfere has not been observed in the extensive testing that has 

been conducted to date. For example, the possibility of NH3 interference was evaluated 

during EPA’s test of mercury measurement approaches at a Midwest coal-fired power plant 

with state-of-the-art ammonia injection and selective catalytic reduction NOx control 

equipment34. Despite the use of ammonia, the XFM reactive filter demonstrated an 11% 

relative accuracy when compared to the Ontario-Hydro Hg reference method concentrations, 

which ranged from 1 to 6 μg/dscm. Similarly, minor reactive components such as NOx, and 

SOx have the potential to impact vapor phase collection efficiency. However, there is no 

indication that these species affected the Hg trapping efficiency at the concentrations listed in 

Table 22. Indeed, the 99+% trapping efficiency for elemental Hg at the Boardman site was 

completed with measured NOx concentrations of 200 PPM and SOx concentrations of about 

225 PPM. In addition, there is no indication that high acidic concentrations affect the 

trapping efficiency since nitric acid concentrations during Phase I and II testing was greater 

Method 301 Eval.: V1.0 Section 7.0 Page 60 of 75
Conclusions and Recommendations

than 50 PPM. The tests conducted to date and the range of key test parameters are 

summarized below in Table 24. 

Table 24. List of test conditions and references used to evaluate method applicability. 

Test Summary Test

Concentration Range

Particulate Metals 3-2200 μg/dscm 1, 2

Elemental Mercury 1-314 μg/dscm 3, 4

Oxidized Mercury 1-880 μg/dscm 3, 5

Holding Time

XFM: Particulate Filter 12 Months 6, 7

XFM: Vapor Phase Filter 24 Months

a 8

Xact 12 Months 6, 7, 8, 9

Stack Type & Conditions

Filters acceptable for Wet Stacks 3, 10, 11

Filters acceptable for Dry Stacks 1, 2, 4, 9

HWC Filters acceptable for HWC applications 1, 2, 9, 11

CFPP Filters acceptable for CFPP applications 3, 4, 10

Stack Temperature 450°F 1, 2

Filter Temperature

XFM Particulate Filter 400°F 12

XFM Vapor Phase Filter 185°F 4, 5

Xact Particulate/Vapor Phase Filter 185°F

Sampling Time

XFM 60 min 4, 5

Xact 30 min 10

Sampling Flow Rate

XFM 4.5 lpm/cm2 4, 12

Xact 2.4 lpm/cm2 12

Field Blank Det. Limits less than 2 μg/dscmb 11

a) Correction factor of 0.5%/month required after six months.

b) One-sigma limits based upon analysis of 3899 filters measurements at Lilly's T149 Incinerator

1 HWC at TEAD production furnace (Section 2.3).

2 HWC at TEAD research furnace (Section 2.3).

3 EPA test at Midwest CFPP (Section 2.3).

4 CES Test at Oregon CFPP (Section 2.3).

5 CES Laboratory Tests (Section 2.3).

6 Reevaluation of Phase I Filters (Section 2.3).

7 EPA PM2.5 Speciation Program7

; Reevaluation of Phase I Filters (Section 2.3).

8 CES Laboratory Evaluation of XFM Filters (Section 2.3).

9 CES Reanalysis of Xact Filter Tape from TEAD tests (Section 2.3).

10 Xact Test at IAAP CFPP (Section 2.3).

11 Evaluation of Blank Filters at Lilly's T149 Incinerator (Section 2.3).

12 Manufacturers Specifications

13 Phase II Tests at Lilly's T149 Incinerator

Parameter

Moisture

Method 301 Eval.: V1.0 Section 7.0 Page 61 of 75
Conclusions and Recommendations

7.6 Applicable Concentration Range 

The applicable concentration range for these reactive filter based methods was extended to 

over 2000 μg/dscm during Xact and Reference Method 29 relative accuracy tests conducted 

in 2002 at an Army hazardous waste test incinerator34. Twelve Reference Method 29 test 

runs were conducted while the stack gas Pb concentrations ranged from a low of about 10 

μg/dscm to over 2200 μg/dscm. The results from these twelve tests are compared to the 

corresponding Xact results in Figure 20. These results show a high degree of linearity over 

this broad range of concentrations and a high relative accuracy of 4% when compared to the 

Method 29 results. If these results are combined with those in the preceding subsection 

where the Hg results were in good agreement with the reference method down to almost 1 

μg/dscm, it is clear that the method is quantitative over at least three orders of magnitude and 

at concentrations greater than 2200 μg/dscm.

Lead

y = 1.0585x + 1.2181

R2

 = 0.9997

0

500

1,000

1,500

2,000

2,500

0 500 1,000 1,500 2,000 2,500

Method 29 Conc. (μg/dscm)

Xact C

onc. (μg/dscm)

n= 12

RA= 4%

 

Figure 20 Plot of Xact-IAP concentration versus Reference Method 29 measured 

concentrations showing excellent agreement over two orders of magnitude and at 

concentrations in excess of 2,000 μg/dscm. 

7.7 Deposit Stability 

The Xact-IAP uses a reel-to-reel tape system to collect stack gas metal samples, which are 

then transported to a position for XRF analysis. After analysis, the tape is drawn over a take 

up spool where the exposed filter deposits come into contact with following tape as it wraps 

over the previously exposed tape. Some potential exists for transfer of metals from their 

original deposit to the tape covering the deposit. If this transfer were significant, it would 

reduce the potential to post-test validate Xact-IAP results with independent analysis of the 

deposits. As such, post test analyses were conducted on 72 deposits collected during relative 

accuracy tests conducted in May 2002 at a US Army hazardous waste production incinerator 

at the Tooele Army Depot (TEAD) in Tooele, UT34. During these tests, the Xact monitored 

emissions in an instrument shed about 40 feet from the incinerator stack while EPA 

Reference Method 29 samples were collected at the stack. Twelve Method 29 test runs were 

conducted with concentrations varying from 5 to 300 μg/dscm. There was very good 

agreement with the reference method as illustrated in Figure 21. The relative accuracy was 

4% and the results exhibited a high degree of linearity. 

Method 301 Eval.: V1.0 Section 7.0 Page 62 of 75
Conclusions and Recommendations

Following these tests, the exposed filter tape was stored at room temperature at CES. Two 

months after the field tests were completed, the tape was removed from the spool exposing 

the previously collected deposits. These deposits were cut from the tape and analyzed with 

CES’ laboratory XRF analyzer. These laboratory results are compared to the original 

concentrations reported by the Xact in Figure 22. Clearly, there is a high degree of 

agreement between the original Xact Pb results and the laboratory results. The slope and 

correlation suggests that there was not a significant transfer of Pb from the deposit to the 

covering tape at the level of a few percent. 

Lead

y = 1.09x - 9.60

R2

 = 0.98

0

20

40

60

80

100

120

140

160

180

0 50 100 150 200

Method 29 Conc. (μg/dscm)

Xa

ct C

onc. (μg/

d

s

c

m)

n = 12

Figure 21. Plot of Pb concentrations determined by Reference Method 29 and the Xact. 

Lead

y = 0.9727x + 3.4259

R2

 = 0.9685

0

20

40

60

80

100

120

140

160

180

0 50 100 150 200

Xact Conc. (μg/m3); May, 2002

Lab Conc. (μg/m3) July, 2002

n =72

Figure 22: Comparison of results from laboratory XRF analysis in July, 2002 with Xact 

field test results from May 2002 relative accuracy tests at a hazardous waste incinerator 

7.8 Moisture 

Over the last three years, the Xact-IAP and XFM have been evaluated on both wet and dry 

stacks (Table 25) using Method 29, Ontario-Hydro and the QAG reference aerosols. In all 

Method 301 Eval.: V1.0 Section 7.0 Page 63 of 75
Conclusions and Recommendations

cases, the Xact-IAP and XFM showed good relative accuracy and trapping efficiencies. For 

this reason, it is believed that the candidate measurement methods are valid for both wet and 

dry stacks as long as the probe and filter temperature remain above the water vapor dew 

point, which are controlled primarily with dilution. 

Table 25: Recent tests of Xact and XFM on wet and dry stacks. 

Date Test 

Location

Inc. 

Type 

Air Pollution

Control 

Technology 

Wet or 

Dry

Stack 

Elements 

Analyzed Results 

March

2005

Eli Lilly 

Lafayette, 

IN 

HWC Scrubber Wet As, Cr, Cd,

Hg, Pb

Xact and XFM within 

15% of QAG

predicted for As, Cr, 

Cd, Hg, Pb

Jan. 

2005

IAAP 

Ames, IA CFPP Scrubber Wet As, Hg

Xact RA of 17% vs. 

M29 for As, Hg

Sept. 

2003

TEAD 

Tooele, UT HWC High Temp. Baghouse Dry Pb Xact RA of 4% vs. M29 for Pb 

May 

2003 Midwest CFPP

Ammonia 

injection, SCR, 

baghouse 

Dry Hg

XFM RA of 11% vs. 

OH for Hg

Aug 

2002

Boardman, 

OR CFPP Scrubber Wet Hgo Trapping efficiency of 

99% for Hgo 

7.9 Holding Times 

Tests were also conducted to evaluate the holding times for the XFM and Xact-IAP filters. 

These tests included both the XFM PTFE filter and the reactive filter. During the December 

2004 Phase I tests, the PTFE filter had collected particulate As, Cd, Cr, Hg, and Pb at 

concentrations ranging from 20 μg/dscm to 125 μg/dscm. In order to determine PTFE filter 

holding times, CES reanalyzed filters from seven of these tests (Runs 1-4 and 21-24) in April 

2005. During the five months between the initial and second XRF analysis, the filters were 

stored at room temperature in plastic petrie dishes. Both analyses were conducted using XRF 

following the IO Compendium Method 3.314. Overall, the average metal concentrations 

measured in April 2005 were within one percent of the concentrations determined five 

months earlier. All measurements were within 4% of their original concentration, with no 

significant bias. The good replication of the metal mass demonstrates the ability of the PTFE 

filters to retain metal concentrations over a five month period. 

Reactive filter tests were conducted to determine retention efficiencies and estimated holding 

times for vapor phase metals using Hg as an indicator species. These tests are based on 

filters exposed to both elemental mercury and mercuric chloride vapors during tests 

conducted in June and August 2002 and filters from coal-fired power plant flue gas tests. All 

filters were kept at room temperature and analyzed using IO Compendium Method 3.314. 

These filters were reanalyzed periodically over the past two years and were found to have 

lost on average about 10% of the original mercury over this period. This finding was 

Method 301 Eval.: V1.0 Section 7.0 Page 64 of 75
Conclusions and Recommendations

independent of laboratory or field application, or oxidation state of Hg trapped. A linear 

model was developed which assumes the mercury loss from the reactive filter to be constant 

over time. This model showed that, when using a correction factor that assumes a loss of 

about 0.5% per month, the mercury concentrations measured after two years were, on 

average, within 10% of the original mercury concentrations. The good agreement for all of 

these tests supports the use of a correction factor of 0.5% per month for filters that have been 

archived for more than six months. This would allow the holding time to extend to at least 

two years. 

7.10 Applicable Elements 

The XRF analysis determination of metals in the filter deposit is based on EPA IO 

Compendium Method 3.3, which is generally applicable to elements with atomic numbers 

ranging from about 13 (Al) through 92 (U). This range of elemental applicability is expected 

to apply to the XFM PTFE filter but not to the reactive filter. In the case of the reactive 

filter, the lowest atomic number element quantifiable with XRF analysis is Cr (24) because 

of significant impurities in the filter matrix. 

The elements of primary regulatory interest are those the Clean Air Act Amendments classify 

as Air Toxics: i.e. Antimony (Sb), Arsenic (As), Beryllium (Be), Cadmium (Cd), Chromium

(Cr), Cobalt (Co), Lead (Pb), Manganese (Mn), Mercury (Hg), Nickel (Ni), and Selenium

(Se). These eleven elements have been sorted by volatility in the Maximum Achievable 

Control Technology (MACT) rules17 as follows: 

• Non-enumerated metal compounds (N): Sb, Co, Mn, Ni, Se; equated to particulate 

matter in the MACT 

• Low volatile metal compounds (L): As, Be, Cr 

• Semi-volatile metal compounds (S): Pb, Cd 

• High volatile metals (V): Hg 

The metals tested in Phase I and II represented particulate matter as well as all of the metals 

in the three volatility categories except the low volatility element Be. The other elements not 

tested are non-enumerated metals, which the EPA has equated to particulate matter in the 

MACT rules. Although these eleven elements represent the primary focus of this discussion, 

it is important to note that these filter based methods are expected to be applicable to most of 

the elements listed in EPA IO Compendium Methods 3.314 and Be by IO Compendium 

Method 3.435. 

7.11 Other Related Tests 

7.11.1 Sample Collection Times 

The theoretical sampling time for the XFM and Xact-IAP is primarily limited by filter 

loading with PM since XRF correction factors may be required for high particulate deposit 

densities. However, the filter loading can be controlled in sources with high particulate levels 

by adjusting the sampling times and dilution ratios up to 4:1. For this reason, it is believed 

Method 301 Eval.: V1.0 Section 7.0 Page 65 of 75
Conclusions and Recommendations

that, these filter-based methods can sample for periods up to four times greater than has 

currently been demonstrated; i.e. four hours for the XFM and two hours for the Xact-IAP. 

7.11.2 Xact Blank Concentrations 

The Lilly Xact, was installed on the T149 hazardous waste incinerator in May 2004 and 

operated throughout the summer of 2004. During this time, the Xact completed about 4000 

runs while the stack was not burning hazardous waste. These runs were treated as field 

blanks and were used to statistically determine Xact-IAP detection limits. These statistically 

determined detection limits were in good agreement with those calculated from the analysis 

of a few filters. 

Table 26: Xact detection limits determined at Lilly’s T149 incinerator 

XFM1 Xact2

μg/dscm μg/dscm

CR 0.08 0.3

AS 0.08 0.1

CD 0.80 2.4

HG 0.14 0.3

PB 0.12 0.6

MN 0.08 0.2

CO 0.08 0.3

NI 0.06 0.3

SE 0.08 0.1

AG 0.60 4.2

SB 1.60 6.2

CU 0.08 0.5

FE 0.12 0.9

ZN 0.06 0.2

BR 0.20 0.4

SR 0.18 0.3

TL 0.14 0.3

DETECTION LIMITS

Elem

1) 95% Confidence, Interference free, 30 minute sample. 

2) 95% of 3899 Xact blank measurements at T149 Incinerator 

7.12 Applicable Source Categories 

As discussed earlier, the filter-based sampling approach has been successfully tested in the 

laboratory and on two hazardous waste incinerators as well as three coal-fired boilers. Each 

of these tests showed good relative accuracy and trapping efficiencies. Source emissions can 

be divided into two categories: fugitive and ducted emissions. Fugitive sources include 

emissions from processes such as field-burning, slag-pouring, emissions from buildings, 

demolition activities, forest fires, etc. in addition to passive fugitive emissions from sources 

such as wind-blown dust and dust suspended by vehicular traffic. These fugitive emissions 

are typically characterized by substantially lower concentrations of possible reactive species 

Method 301 Eval.: V1.0 Section 7.0 Page 66 of 75
Conclusions and Recommendations

8.0 Conclusions and Recommendations 

than the concentrations in the ducted emissions already successfully tested. As such, the 

XFM and Xact-IAP should be applicable, in general, to these fugitive emission sources 

because the characteristics of their emissions are less challenging than the ducted sources 

already tested. 

Ducted sources, on the other hand, can have emission characteristics similar to those already 

tested, and in some cases may exceed the values for some parameters that may be more 

challenging than those already tested. As discussed earlier, the filter-based approach has 

shown consistent success over the past few years while sampling at two hazardous waste 

incinerators and three coal-fired boilers with a wide range of controls (wet scrubbers, ESPs, 

high temperature ceramic baghouses, ammonia injection, selective catalytic reduction, lime 

spray dryer absorber for SO2 control, and a fabric filter for particulate control). In each case 

the relative accuracy in comparison to the QAG, Ontario Hydro, and Method 29 was better 

than the EPA required 20% for conditional method consideration. In general, the filter-based 

approaches have been accurate regardless of source category, emission control technology 

used, moisture content and stack chemistry. As such, the Xact-IAP and XFM methods 

should be applicable to a wide range of source categories including incinerators, boilers, 

kilns, smelters, plating operations, foundries, mineral processing and other industrial 

processes using a wide range of pollution control technologies. 

The results from Phase I and II tests and the preceding discussion, as well as results from 

previous tests, support the following conclusions.

1. The QAG candidate reference aerosol generator met all of the required validation 

criteria and should be approved as a NIST-traceable reference aerosol generator for 

initial certification and continuing quality assurance audits for multi-metal sampling 

and analysis methods. 

2. The XFM candidate conditional method for measuring metal concentrations in 

emissions from stationary sources met all of the required validation criteria and 

should be approved for initial certification and continuing quality assurance audits of 

multi-metals CEMS. 

3. The Xact-IAP candidate conditional method for measuring metal concentrations in 

emissions from stationary sources met all of the required validation criteria and 

should be approved for use at incinerators for initial certification and continuing 

quality assurance audits of multi-metals CEMS. 

4. The QAG candidate reference aerosol generator is independent of its application and 

should be approved as a generally applicable reference aerosol generator for research, 

method certification, and audit validation. 

5. The XFM and Xact-IAP candidate conditional methods have demonstrated their 

applicability to a wide range of source types, controls and stack conditions; and 

because of their use of dilution techniques and the resulting insensitivity to stack gas 

characteristics; these methods should be approved as conditional reference methods 

Method 301 Eval.: V1.0 Section 8.0 Page 67 of 75
for use in regulatory applications where stack gas metal emission measurements for 

fugitive or stationary sources are required. 

9.0 Glossary 

Accuracy: The closeness of agreement between a measured value and the true value. 

Accuracy involves a combination of random error components and a systematic bias 

component. 

Aerosol: A dispersion of solid or liquid particles in gaseous media. 

Analyte: Element of interest in an analytical measurement. 

Analytical NIST Traceable: Procedure in which NIST-traceability is achieved by 

calibrating the measurement instrument with NIST standard reference materials (SRM) or 

standards which are themselves traceable to NIST. To ensure continuing accuracy the 

calibration of the measuring instrument should be checked against the NIST standard 

reference materials or NIST traceable materials on a regular basis. 

Approved alternative method: A procedure that is an approved alternative to a method 

required by 40 CFR Parts 60, 61 and 63 as described by the General Provisions of the 

corresponding Parts. As such, it may be used by sources for determining compliance with the 

requirements of these Parts per their specified applicability provisions without further EPA 

approval. 

Aspiration: The process by which a liquid is drawn from a reservoir through a narrow tube 

by creating a vacuum above the tube with fast moving air. 

Atomization: The process of converting a liquid into small suspended droplets. 

Attenuation: Reduction of amplitude or change in wave form due to energy dissipation or 

distance. 

Audit: A methodical examination and review. 

Bias: The difference between a measured mean and the true value. Bias represents 

systematic difference. 

Blank: A sample known to have a parametric value of zero. 

Calibration Drift (CD): The difference in measured output readings from a calibrated 

reference value after a stated period of operation during which no scheduled maintenance, 

repair, or adjustment took place. 

Calibration: The process of comparing a sampling or instrumental response with a known 

parametric value for the purpose of obtaining a quantitative relationship between the 

response and the parametric value. This relationship can then be used to determine the 

parametric value for an unknown sample. 

Candidate method: The sampling and analytical procedure selected for validation by the 

method described herein. 

Certification: To attest to being true or as represented or as meeting a standard.

Method 301 Eval.: V1.0 Section 9.0 Glossary Page 68 of 75 
Compendium method: A collection of approved EPA methods for the determination of

inorganic (IO) or organic (TO) compounds in ambient air. 

Conditional test method: Methods that have been evaluated by the EPA and may be 

applicable to one or more categories of stationary sources. These method’s QA/QC 

procedures are required as a condition of applicability and must be approved as alternatives 

before a source may use them to meet Federal requirements under 40 CFR Parts 60, 61, and 

63. They may be used by State and local programs in conjunction with federally enforceable 

programs (e.g., Title V permits, State Implementation Plans (SIP)) provided they are subject 

to an EPA Regional SIP approval process or permit veto opportunity and public notice and 

opportunity for comment. 

Correction factor: A quantity applied to a measurement to adjust the value of that 

measurement to the true value. 

Correlation coefficient: A number or function that indicates the degree of correlation 

between two sets of data or between two variables and that is equal to their covariance 

divided by the product of their standard deviations. 

Detection Limit: The lowest concentration of a chemical that can reliably be distinguished 

from a zero concentration. 

Drift: Percent change in a mean value measured over period of time. 

Elemental ratios: The relationship in quantity, or mass between two or more elements 

trapped during a single sampling period. 

Emissions: The total of substances discharged into the air from a stack, vent, or other 

discrete source. 

Error: The difference between an observed or calculated value and a true value; specifically: 

variation in measurements, calculations, or observations of a quantity due to unsystematic 

factors. 

Filter: A porous medium for collecting particulate matter. 

Filter ratio: The relationship in quantity, or mass of an element trapped on two or more 

filters used in combination during a single sampling period. 

Holding Time: The maximum amount of time a sample may be stored before analysis. 

Impaction: A forcible collision of particles of matter with an object. 

Impactor: A device that employs the principle of impaction. 

Intercept: The distance from the origin to a point where a line crosses a coordinate axis. 

Interferent: A substance that causes systematic errors in the measurement of another 

substance. 

Isokinetic sampling: Emissions sampling in which the linear velocity of the gas entering the 

sampling nozzle is equal to that of the undisturbed gas stream at the sample point. 

Linearity:A check of the degree to which the candidate reference method response is linear 

relative to a change in concentration of a reference aerosol a change in concentration reported 

by a reference method. . 

Method 301 Eval.: V1.0 Section 9.0 Glossary Page 69 of 75 
Low-volatile metals (LVM): Any metal that does not volatilize readily (e.g., arsenic (As), 

beryllium (Be), and chromium (Cr)). 

Metal ratio: The relationship in quantity, or mass of two or more metals trapped on a filter 

or series of filters used in combination during a single sampling period. 

Method 29: An EPA reference method to determine the metals emissions from stationary 

sources it is contained in 40 CFR 60 Appendix A. 

Method 301: An EPA protocol for the field validation of candidate pollutant measurement 

methods from various waste media. 

Negative bias: Bias when the measured result is less than the “true” or reference value. 

NIST: U. S. Department of Commerce, National Institute of Standards and Technology, 

Gaithersburg, MD 20899 

Non-destructive: Not causing destruction of material being investigated or treated 

Ontario Hydro Method A method for determining the concentration of elemental, 

oxidized, particle-bound and total mercury in flue gas generated from coal-fired stationary 

sources.

Outlier: Extreme measurements that stand out from the rest of the sample and may be faulty. 

Particle: A small discrete mass of solid or liquid matter. 

Particulate: Solids or liquids existing in the form of separate particles. 

Performance audit material: EPA-approved material of known composition that can be 

used to simulate an unknown sample to test the candidate procedure. 

Performance Specifications: Performance specifications are used for evaluating the 

acceptability of the CEMS at the time of or soon after installation and whenever specified in 

the regulations. Quality assurance procedures in 40 CFR Part 60 Appendix F are used to 

evaluate the effectiveness of quality control (QC) and quality assurance (QA) procedures and 

the quality of data produced by any CEMS that is used for determining compliance with the 

emission standards on a continuous basis as specified in the applicable regulation. 

Positive bias: Bias when the measured result is greater than the “true” or reference value. 

Practical limit of quantitation (PLQ): The lowest level above which quantitative results 

may be obtained with an acceptable degree of confidence. The PLQ is defined as 10 times 

the standard deviation, So, at the blank level with an uncertainty of ±30% at the 99% 

confidence level. 

Precision: The degree of mutual agreement between individual measurements of a 

parameter having the same value,. In this report it is defined as the percent relative standard 

deviation (PRSD) of a series of measurements over a relative short test period in contrast to 

stability, which is a determined measurement over an extended period of time. 

Process NIST Traceable: A parameter whose value is traceable to NIST through a 

procedure, the steps of which are each NIST traceable1

Method 301 Eval.: V1.0 Section 9.0 Glossary Page 70 of 75 
Quality Assurance/Quality Control: A system of procedures, checks, audits, and corrective 

actions to ensure that all EPA research design and performance, environmental monitoring 

and sampling, and other technical and reporting activities are of the highest achievable 

quality. 

Quantitative Aerosol Generator (QAG): An aerosol generator system that uses analytes of 

known concentrations in aqueous solution to create aerosol emissions of known metal 

concentrations. 

Quantitative: Of, relating to, or involving the measurement of quantity or amount. 

QuanX ®:A Spectrace Instruments energy-dispersive x-ray fluorescence spectrometer. 

R: Correlation coefficient, an indicator of how well the data fits a linear relationship.

R2

 1: proportion of the total sum of squares that can be accounted for by the linear 

regression of y on x 2: a statistic that indicates the strength of the relationship between x 

and y. 

Reference aerosol: An aerosol that contains a known concentration or concentrations of 

analytes. 

Reporting time: The time interval for which the report is representative. 

Representative sample: A portion of material that is as nearly identical in content and 

consistency as possible to that in the larger body of material being sampled. 

Response time: The time interval from a step change in pollution concentration at the input 

to the continuous monitoring system to the time at which 95 % of the corresponding final 

value is reached as displayed on the continuous monitoring systems data recorder. 

Ruggedness test: A laboratory study to determine the sensitivity of a method to parameters 

such as sample collection rate, interferent concentration, collecting medium temperature, and 

sample recovery temperature by changing several variables at a time. 

Sampling system: The system which extracts a sample of effluent gas from a source and 

and delivers it to point where collection or measurement of the analytes in the source can 

occur. 

Secondary Particles (or Secondary Aerosols): Aerosols that form in a gaseous matrix as a 

result of chemical reactions. 

Semi-volatile metals: Lead (Pb), cadmium (Cd). 

Slope: For a line described by the equation y = mx + b, m is the slope of the line. The slope 

expresses the amount of change that will occur in y due to changes in x. 

Spectral Interferent: An interfering element or species that’s absorption or emission 

characteristics overlap or lie so close to the analytes absorption or emission characteristics 

that resolution becomes impossible. 

SRM: Standard Reference Materials.

Stability: The consistency in the measurement of a constant value over an extended period 

of time. 

Method 301 Eval.: V1.0 Section 9.0 Glossary Page 71 of 75 
Standard: An item with a value for a parameter that has been established by authority, 

custom, or agreement to serve as a model or rule in the measurement of quantity or the 

establishment of a practice or procedure.

Surrogate Data: Data from studies of test substance or substances that are used to estimate 

the characteristics or effects on another substances. 

Thin film standard reference material: A NIST traceable standard reference material 

comprised of either an element(s) or compound(s) of a known and stable concentration. The 

thin film standards are used to calibrate X-ray fluorescence instruments. 

Traceable to NIST: A documented procedure by which a measured response is related to a 

standard with an accuracy defined by and certified by the National Institute of Standards 

Technology (NIST). 

Transport efficiency: The percentage of a known concentration of analyte or analytes that 

can be conveyed to an analysis instrument from their source. 

Uncertainty: A statistically defined value associated with a single measurement or a value 

associated with a group of measurements that defines the range and probability of additional 

measurements falling within the defined range, and can include allowance for both 

systematic and random sources of error. 

Unknown: A sample submitted for analysis whose elemental concentration is not known. 

Upscale drift: The difference in an instrument’s output readings from the established upscale 

reference value after a stated period of operation during which no scheduled maintenance, 

repair or adjustment took place. 

Validation: The determination of the degree of validity of a measuring device 

Verifiable: Capable of being confirmed for precision and accuracy. 

Verification: Confirming the precision and accuracy of an instrument. 

Volatile metal: Any metal substance that evaporates readily at low temperature (e.g., 

mercury). 

Xact: Cooper Environmental Service’s X-ray fluorescence based emissions monitor capable 

of measuring metals found in flue gas emissions. 

Xact-CEMS: Cooper Environmental Service’s X-ray fluorescence based continuous metal 

emissions monitor. 

XACT-IAP: An instrumental analyzer procedure utilizing Cooper Environmental Service’s 

XACT to measure metal emissions from stationary sources. 

XFM: Cooper Environmental Service’s X-ray based filter method to measure metal 

emissions from stationary sources. 

Xact-IM: Cooper Environmental Service’s X-ray fluorescence based continuous emissions 

monitor primarily focused on the detection of mercury in flue gas emissions. 

XRF: X-ray fluorescence – An analytical technique used to determine the concentration of 

an element or elements.

Method 301 Eval.: V1.0 Section 10.0 References Page 72 of 75 
Zero Drift: The difference in an instrument’s output readings for zero input after a stated 

period of operation during which no unscheduled maintenance, repair or adjustment took 

place. 

References

10.0 References 

1. EPA Test Method 301, Field Validation of Pollution Measurement Methods for 

Various Media, 40 CFR 56, 27370-27374. June 13, 1991. 

2. EPA Test Method 29, Determination of Metals Emissions from Stationary Sources, 

40 CFR 60, Revised July 1, 1996. 

3. ASTM D6784-02. Standard Test Method for Elemental, Oxidized, Particle-Bound 

and Total Mercury in Flue Gas Generated from Coal-Fired Stationary Sources 

(Ontario Hydro Method), 2002. 

4. Cooper, J.A, B.E. Johnsen, S.C. Fry, May 2003. Installation and Use of an X-ray 

Based Continuous Emissions Monitor for AED Treatability Study. Submitted to US 

Army Equipment Directorate, Tooele Army Depot. Contract No. DAAA14-02-P0216. 

5. Hosenfeld, J., Sept. 2003. Long-Term Field Evaluation of Mercury (Hg) Continuous 

Emission Monitoring Systems: Coal-Fired Power Plant Equipped With Dry Flue Gas 

Desulfurization/Fabric Filtration Emission ControlsPhase III (Field Work Performed 

May-July 2003). Final Report for U.S. Environmental Protection Agency. EPA 

Contract 68-D2-01-002 Work Assignment 3-04. MRI Project No. 110130.3.004. 

6. EPA. May 03, 2005. List of Designated Reference and Equivalent Methods (Ambient 

Methods). Found on EPA website at http://www.epa.gov/ttn/amtic/criteria.html. 

7. EPA. April 1994. Quality Assurance Handbook for Air Pollution Measurement 

Systems. Volume II: Ambient Air Specific Methods (Interim Edition). EPA/600/R94/038b. 

8. Prieditis, H. IYR Adamson 2002. Comparative Pulmonary Toxicity of Various 

Soluble Metals Found in Urban Particulate Dust. Exp. Lung. Res 28: 563-576. 

9. Monn C, Becker S. 1999. Cytotoxicity and induction of proinflammatory cytokines 

from human monocytes exposed to fine (PM2.5) and coarse particles (PM10-2.5) in 

outdoor and indoor air. Toxicol Appl Pharmacol 155:245-252. 

10. Clean Air Act Amendments of 1990 (CAAA), Pub.L. No. 104-549, 104 Stat. 2399 

(1990). 

11. EPA, 2005. Rules and Implementations for Toxic Air Pollutants. Found at EPA’s 

Technology Transfer Network Air Toxics Website. 

http://www.epa.gov/ttn/atw/eparules.html. 

Method 301 Eval.: V1.0 Section 10.0 Page 73 of 75 
12. EPA 450/4-92-013 Vol. 1 December 9, 1991. Evaluation of Two Methods for the 

Measurement of Mercury Emissions in Exhaust Gases from a Municipal Waste 

Combustor. 

13. Rigo, H.G., A.J. Chandler. Quantiation Limits for Reference Methods 23, 26, and 29. 

J. Air & Waste Manage. Assoc. 49:399-411. 

14. EPA Compendium of Methods for the Determination of Inorganic Compounds in 

Ambient Air. June, 1999. Compendium Method IO-3.3 Determination of Metals in 

Ambient Particulate Matter Using X-Ray Fluorescence (XRF) Spectroscopy. 

EPA/625/R-96/010a. 

15. Jayanty, RKM. 2002. PM2.5 Chemical Speciation Nationwide Network and its 

Challenges. Symposium on Air Quality Measurement Methods and Technology – 

2002. San Francisco, CA. 

16. May K.R. (1973) The Collison Nebulizer. Description, Performance & Application J. 

of Aerosol Science, Vol. 4, #3, p. 235 

17. US EPA. NESHAPS Standards for Air Pollutants for Hazardous Waste Combustors 

Final Rule. FR67 No. 31 pp. 6967-6996. February 14, 2002. 

18. Eli Lilly and Company T149 Liquids and Solid Waste Incinerator. Tippe, IN. 

19. US EPA PS-11. Performance Specification 11 – Specifications and Test Procedures 

for Particulate Matter Continuous Emissions Monitoring Systems at Stationary 

Sources. U.S. Environmental Protection Agency, Office of Air Quality Planning and 

Standards, Emissions Measurement Center, FR69 vol. 7. pp. 1785-1821. January 12, 

2004. 

20. US EPA PS-10. Proposed Performance Specification 10 – Specifications and Test 

Procedures for Multi-Metals Continuous Monitoring Systems at Stationary Sources. 

U.S. Environmental Protection Agency, Office of Air Quality Planning and 

Standards, Emissions Measurement Center, August 1997. 

21. Chester LabNet. 12242 SW Garden Place Tigard, Oregon 97223 ph. 503.624.2183 

22. EPA Test Method 301, Field Validation of Pollution Measurement Methods for 

Various Media, 40 CFR 56, 27371. June 13, 1991. 

23. Pall Life Sciences. 2003. Laboratory Filtration and Separation Catalog. pp.30-31. 

24. CES. 2005. Pro-11 Filter used by CES’ Xact Multi-Metals Continuous Emissions 

Monitor. http://www.cooperenvironmental.com/products.html. 

25. Dry Cal DC Lite Primary Flow Calibrators. Found on the web at 

http://www.drycal.com/drycal/index.htm. 

26. Handbook of Chemistry and Physics. 65th Edition. Weight in Grams of a Cubic Meter

of a Saturated Aqueous Vapor (From Smithsonian Tables). p. E-37. 

27. Currie, L.A. 1978. “Detection and Quantitation in X-ray Fluorescence Spectrometry. 

in X-ray Fluorescence Analysis of Environmental Samples. T. G. Dzubay (ed). Ann 

Arbor Science Publishers, Inc. pp. 289-306. 

Method 301 Eval.: V1.0 Section 10.0 References Page 74 of 75 
28. Seinfeld, J.H., S.N. Pandis. 1998. Atmospheric Chemistry and Physics. Page 10. 

Elevation of incinerator is about 630 ft. 

29. Paule, R.C., G. Marinenko, M. Knoerdel, and W.F. Koch. Jan 1986. Ruggedness 

Testing – Part I: Ignoring Interactions. Journal of Research of the National Bureau of

Standards. Vol. 91. No. 1. pp. 3-8. 

30. Paule, R.C., G. Marinenko, M. Knoerdel, and W.F. Koch. Jan 1986. Ruggedness 

Testing – Part II – Recognizing Interactions. Journal of Research of the National 

Bureau of Standards. Vol. 91. No. 1. pp. 9-16. 

31. Ahmed, K. of Pall Corporation personal communication to CES’ B.E. Johnsen June 

3, 2005. Results of Air Techniques TDA-100A standard DOP Test. 

32. US EPA PS-11. Performance Specification 12a – Specifications and Test Procedures 

for Total Vapor Phase Mercury Continuous Emissions Monitoring Systems in 

Stationary Sources. U.S. Environmental Protection Agency, Office of Air Quality 

Planning and Standards, Emissions Measurement Center, FR69. pp. 4701-4750. 

Appendix B Part 60 Jan. 30 2004. 

33. Cooper, J.A., B.E. Johnsen, P. Ginochio. April 2005. Re-design and Field Testing of 

an X-Ray Fluorescence Multi-Metals Monitor at the Iowa Army Ammunition Plant, 

Middleton, Iowa Coal Fired Boiler. Submitted to US Army Corp of Engineers: 

Engineer Research and Development Center under contract no. W9132T-04-P-0065. 

34. Hay, K.J., V.M. Boddu, B.E. Johnsen, J.A. Cooper. January 2005. Report No. 

ERDC/CERL-TR-05-3. X-Ray Fluorescence-Based Multi-Metal Continuous 

Emission Monitor Technology Demonstration. US Army Corps of Engineers: 

Engineer Research and Development Center. 

35. EPA Compendium of Methods for the Determination of Inorganic Compounds in 

Ambient Air. June, 1999. Compendium Method IO-3.4 Determination of Metals in 

Ambient Particulate Matter Using Inductively Coupled Plasma (ICP) Spectroscopy. 

EPA/625/R-96/010a. 

36. Scott Specialty Gases. Scott Gas Mixtures Data: Gas and Liquid Mixture Basics. 

Plumsteadville, PA: Scott Specialty Gases; 2004. 

Method 301 Eval.: V1.0 Section 10.0 References Page 75 of 75