Performance Audit of the U.S. Geological Survey, Energy 

Resource Program Inorganic Geochemistry Laboratory 

By James A. Luppens, Louis G. Janke, Jamey D. McCord, John H. Bullock, Lisa Brazeau, and Ronald H. 

Affolter 

Open-File Report 2007–1136 

U.S. Department of the Interior 

U.S. Geological Survey 
ii

U.S. Department of the Interior 

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

Mark D. Myers, Director 

U.S. Geological Survey, Reston, Virginia 2007 

For product and ordering information: 

World Wide Web: http://www.usgs.gov/pubprod 

Telephone: 1-888-ASK-USGS 

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its natural and living resources, natural hazards, and the environment: 

World Wide Web: http://www.usgs.gov 

Telephone: 1-888-ASK-USGS 

Suggested citation: 

Luppens, J.A, Janke, L.G. McCord, J.D., Bullock, J.H. Brazeau, L., Affronter, R.H., 2007, Performance Audit of 

the U.S. Geological Survey, Energy Resource Program Inorganic Geochemistry Laboratory: U.S. Geological 

Survey, Open-File Report 2007-1136 

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endorsement by the U.S. Government. 

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report. 
iii

Contents 

Abstract ............................................................................................................................1 

Introduction .................................................................................................................1 

Purpose and Goals of the External Audit ........................................................................................2 

Organization of the Audit Tasks and Reports ............................................................................3 

Approach ....................................................................................................................4 

Summary of Findings ......................................................................................................8 

Phase 1: Preliminary Proficiency Assessment ...........................................................................8 

Phase 2: Reconciliation of Preliminary Audit Recommendations ....................................................8 

Phase 3: Reassessment of Performance and On-site Evaluation ......................................................9 

Measurable Benefits of the Performance Audit ......................................................................12 

Future work .................................................................................................................14 

Conclusions ................................................................................................................15 

Acknowledgments .......................................................................................................15 

References Cited ........................................................................................................,16 

Appendix A - Phase 1: Preliminary Evaluations of Quality System and Recommendations......................17 

Appendix A.1: Preliminary Evaluation of Quality System; Initial Report............................................18 

Appendix A.2: Preliminary Evaluation of Quality System; Final Report.............................................33 

Appendix B - Phase 3: Reassessment Analyses, and On-site Audit Final Report ...............................44 

Appendix B.1: Evaluation of Reassessment Results from Chlorine Determinations..............................45 

Appendix B.2: Evaluation of Reassessment Results for Major Oxides..............................................50 

Appendix B.3: On-Site Evaluation of USGS IGL .......................................................................63 

Appendix B.4: References for Cited Standards and organizations ................................................89 

Figures 

Figure 1. The ‘Horwitz Trumpet’ ........................................................................................5 

Figure 2. The Horwitz Function plotted on a log-log scale ............................................................6 

Figure A.1.X1.1. Sulfur expanded uncertainty (2001 – 2004) .........................................................28 

Figure A.1.X1.2. Chlorine expanded uncertainty (2001 – 2004) ..............................................................29 

Figure A.1.X1.3. Mercury expanded uncertainty (2001 – 2004) ......................................................30 

Figure A.1.X1.4. Silica expanded uncertainty (2001 – 2004 ......................................................................................31 

Figure A.1.X1.5. Vanadium expanded uncertainty (2001 – 2004) ...................................................32 

Figure B.2.1. The comparison of reported and corrected silica oxide values ................................... 55 

Figure B.2.2. The comparison of reported and corrected Aluminum oxide values ...............................56 

Figure B.2.3. The comparison of reported and corrected Iron oxide values .....................................57 
Figure B.2.4. The comparison of reported and corrected Calcium oxide values ........................................58 

Figure B.2.5. The comparison of reported and corrected Magnesium oxide values .............................59 

Figure B.2.6. The comparison of reported and corrected Sodium oxide values ..................................60 

Figure B.2.7. The comparison of reported and corrected Potassium oxide values ..............................61 

Figure B.2.8. The comparison of reported and corrected Titanium oxide values ................................62 

Tables 

Table 1. IGL CANSPEXTM results before and after performance audit analyses ..................................13 

Table 2. Summary of CANSPEXTM results before and after IGL performance audit ..............................14 

Table A.1.1. Relative proficiency ranking for a nine laboratory comparison .....................................20 

Table A.1.2. Estimation of Cost savings from recommendations ....................................................21 

Table A.1.3. Recommended purchases of certified reference and reference materials ........................21 

Table A.1.4. Acceptance values of certified reference and reference materials ...............................22 

Table A.1.5. The expected yearly net cost savings realized ................................................................23 

Table A.1.6 Net Per Year Consumable and Man-Hour Savings .......................................................24 

Table A.2.1. Trace element performance summary table .............................................................38 

Table A.2.2. Major and minor element performance summary table .......................................................39 

Table A.2.3: Coal analysis performance ratios ........................................................................41 

Table A.2.X1.1. Estimated cost savings over a four year period for all recommendations ......................43 

Table B.1.1. USGS IGL Raw chlorine data ..............................................................................47 

Table B.1.2. USGS IGL Chlorine results corrected for calibration and control bias ..............................48 

Table B.2.1. Expected major oxide totals for the CRM samples ....................................................51 

Table B.2.2. The major oxide total (weight percent basis) ...........................................................52 

Table B.2.3. Comparison of Precision and Accuracy of Corrected Oxide vs. Reported Oxides ................53 

Table B.3.1. ASTM standards for collection of mine samples and commercial samples .........................65 

Table B.3.2. Riffle slot sizes for particle sizes at each stage of sample reduction ...............................66 

Table B.3.3. The number of standards required by the type of calibration curve .................................73 

Table B.3.4. The point at which the ± 2s uncertainty reaches 20% of the chlorine value ...............................82 

Table B.3.5. The point at which the ± 2s uncertainty reaches 20% of the mercury value ......................85 

Table B.3.6. The major and minor oxides normally determined in coal ash ........................................86 

Table B.3.7. The relevant applicable standards and expected percent uncertainty......................................87 

iv
Performance Audit of the U.S. Geological Survey, 

Energy Resource Program Inorganic Geochemistry 

Laboratory 

By James A. Luppens1, Louis G. Janke2, Jamey D. McCord3, John H. Bullock3, Lisa Brazeau3, and 

Ronald H. Affolter3

 

Abstract 

A performance audit of the U.S. Geological Survey (USGS), Energy Resource Program 

(ERP) Inorganic Geochemistry Laboratory (IGL) was conducted between August, 2003 and 

October, 2005. The goals were to ensure that a high level of analytical performance was 

maintained and identify any areas that could be enhanced. The audit was subdivided into three 

phases. Phase 1 was a preliminary assessment of current performance based on recent 

performance on CANSPEXTM samples. IGL performance was also compared to laboratories 

world-wide with similar scope. Phase 2 consisted of the implementation of the recommended 

changes made in Phase 1. Phase 3 of the audit consisted of a reassessment effort to evaluate the 

effectiveness of the recommendations made in the Phase 1 and an on-site audit of the laboratory 

facilities. Phases 1 and 3 required summary reports that are included in Appendices A and B of 

this report. The audit found that the IGL was one of the top two laboratories compared for trace 

element analyses. Several recommendations to enhance performance on major and minor 

elemental parameters were made and implemented. Demonstrated performance improvements as 

a result of the recommended changes were documented. Several initiatives to sustain the 

performance improvements gained from the audit have been implemented.

Introduction 

The U.S. Geological Survey (USGS), Geologic Discipline, Energy Resources Program 

(ERP) addresses the challenge of increasing demand for affordable energy from environmentally 

acceptable energy sources by conducting basic and applied research on geologic energy 

resources and on the environmental, economic, and human health impacts of their production 

and use. The ERP provides reliable and impartial scientific information and comprehensive 

analyses of oil, natural gas, and coal resources of the nation and the world. The results of USGS 

 

1 U.S. Geological Survey, Reston, VA 20192, USA 

2 Quality Associates International® LDT; Douglas, Ont., Canada, K0J 1S0 

3 U.S. Geological Survey, Denver, CO 80225, USA 

1
data and USGS research are used to shape policies regarding domestic and foreign energy 

resources and to manage energy resources on Federal lands. 

An integral component of that energy research program is the ERP Inorganic 

Geochemistry Laboratory (IGL) located in Denver, CO. The IGL is responsible for the analysis 

of major, minor, and trace elements in coal, overburden, water, and related samples from diverse 

sources not only from coal regions in the US, but also from around the world. Samples come 

from projects such as the National Coal Resource Assessment (NCRA), World Coal Quality 

Inventory (WoCQI), National Coal Quality Inventory (NaCQI), and various research studies on 

coal and coal by-products as well as associated studies on environmental and health impacts. The 

IGL’s primary focus is the analysis of major, minor, and trace elements in coal and related 

samples. Recently, water analyses from studies involving leachate samples from coal combustion 

by-products, coal bed methane (CBM) produced water samples, and air samples have also 

become a significant part of the IGL’s capabilities. Routine coal analyses that include 

proximate, ultimate, equilibrium moisture and ash fusion temperatures are performed under 

contract by Geochemical Testing, Somerset, PA. 

The data generated and the expertise of IGL personnel developed over years of analyzing 

such a unique and varied energy-related sample suite is a critical support component of the 

ERP’s programs. Furthermore, the IGL not only provides production analyses, but also devotes a 

significant amount of time improving existing techniques and developing new standard 

procedures in cooperation with ASTM International Committee D05 on Coal and Coke to meet 

the needs of ongoing and future scientific studies. Increased emphasis throughout the coal 

industry on understanding the impacts of production and usage of coal, including the effects of 

mercury, arsenic, and other toxic elements, will ensure that the major, minor, and trace element 

results generated by the IGL will have increased visibility and importance. 

Purpose and Goals of the External Audit 

Although the term “audit” often has negative implications, it should always be designed 

and perceived as a constructive practice. A basic principle of sound quality management is a 

formal audit by an external examiner at appropriate intervals to verify that operations comply 

with the elements of good laboratory practice. Periodic outside reviews are required regardless of 

a laboratory’s current performance. The ultimate goal is to demonstrate and maintain a high level 

of confidence that the IGL continues to produce data that are of the requisite accuracy. Because 

USGS data are used world-wide, it is vital that the IGL Quality Management System (QMS) 

complies with the elements of good laboratory practice specified in ISO/IEC 17025, “General 

requirements for the competence of testing and calibration laboratories” (ISO/IEC, 2005), to 

maintain international credibility as a lead agency in coal quality assessment. Compliance with 

national standards such as ASTM D 4182 and ASTM D 4621 (ASTM International, 2006), 

which reflect the requirements of ISO/IEC 17025, makes certain that the USGS continues to 

address the interests and needs of the coal industry. 

As part of a continuing effort to demonstrate government accountability, the ERP 

awarded a contract to conduct an operating audit of the IGL to Quality Associates International® 

LDT (QAI) in July, 2003. The fundamental scope of the audit by QAI was to evaluate 

performance of the IGL to ensure that its operations were consistent with ISO 17025 (ISO, 

2005), ASTM D4621-99, and D4182-97 (ASTM International, 2006). Where appropriate, the 

audit was required to make recommendations for incorporation into the QMS that will optimize 

the continuing production of reliable results from major, minor and trace element analyses when 

2
employing industry consensus standards and in-house methods. To ensure a comprehensive 

assessment of all analytical values reported by the IGL, the scope of the audit was expanded to 

include an abridged evaluation of the performance of Geochemical Testing, Somerset, PA, which 

is the contract laboratory currently used for basic coal quality parameters including proximate 

and ultimate analyses. The specific goals of the audit were: 

• Compare recent IGL performance with similar laboratories around the world. 

• Produce consistent, high quality data. 

• Lower operational costs. 

• Create a working environment that optimizes staff involvement in quality assurance that 

fosters a constructive process for continuous improvement rather than just a simple, onetime “score card”. 

• Position the laboratory to become a recognized competent practitioner of analyses based on 

a performance based testing program, an approach that is being adopted by major standards 

writing organizations around the world. 

Performance based testing (PBT) provides the ability to continually demonstrate the 

production of credible analytical results through comparison with accepted performance 

benchmarks. An effective way to accomplish such comparisons is through the continuing use of 

samples with known values that can be to traceable to certified reference materials. Simply 

stated, the essential objectives of PBT are to demonstrate both proof of competency and proof of 

value. Thus, attainment of proficiency in PBT practices is the ultimate goal for the IGL.

Organization of the Audit Tasks and Reports 

This external audit was structured differently than the traditional approach where an 

auditor simply conducts an on-site inspection and writes a report summarizing the findings of 

that visit. In this case, the audited laboratory is then left on its own to address, implement, and 

verify any recommendations. The approach taken for this audit was more interactive and 

comprehensive, consisting of three phases. The purpose of this report is to organize all the 

reports generated during the IGL performance audit into one document and provide a summary 

of the audit process and results. The complete results and conclusions can be found within the 

body of the individual audit reports presented in Appendices A and B. 

Phase 1 consisted of a preliminary assessment of the recent IGL performance and 

submitting recommendations to address specific identified deficiencies. The purpose of this task 

was to verify that the QMS utilized at the IGL produces reliable major, minor and trace 

elemental analytical results from energy-related samples that the IGL routinely analyzes. 

Analytical results from other coal laboratories around the world were also studied to see how the 

IGL operations and results compared with those from organizations with similar scope and 

sample throughput. Reports were prepared by QAI summarizing the preliminary findings of 

Phase 1 audit. These reports included a summary of findings, list of significant deficiencies, 

recommended corrective measures and recommended improvements, and an overall assessment 

of the IGL’s ability to produce reliable analytical results. 

Phase 2 of the performance audit consisted of a period in which the IGL implemented all 

of the recommended changes identified in Phase 1. This included the purchase of additional 

certified reference materials (CRMs), modifications to sample preparation and analytical 

procedures, and acquisition of new equipment and instrumentation. This phase also included a 

trial period to ensure that the IGL personnel had fully implemented all of the recommendations 

3
and that the new instruments were fully functional. No audit reports were generated during this 

phase. 

Phase 3 of the audit consisted of a reassessment task to evaluate the effectiveness of the 

implementation of the recommendations from the Phase 1 reports. An on-site audit of the IGL 

laboratory facilities was also conducted to verify that recommendations made during the 

performance audit had been properly implemented as well as providing a summary of best 

practices methodology as an aid to developing a comprehensive QMS. Phases 1 and 3 required 

summary reports that are included in Appendices A and B of this report. 

Approach 

In developing an approach for conducting the audit, two basic concepts needed to be 

addressed. First, is there a universally recognized laboratory audit standard, and second, is there 

a universally accepted benchmark for comparing laboratory results? 

Fortunately, ISO/IEC Guide 17025 (ISO, 2005) provides a comprehensive framework for 

laboratory performance evaluation. This guide contains all of the requirements that testing 

laboratories have to meet in order to demonstrate that they are able to generate technically valid 

results. The methodology for the IGL laboratory audit followed ISO 17250 which provides the 

following guidelines: 

• Specifies the requirements for technical competence. 

• Facilitates the acceptance of results and cooperation between countries. 

• Includes all quality elements present in the ISO 9000 series. 

• Emphasizes certification using ISO 9000 alone does not demonstrate the competence of the 

laboratory to produce technically valid results. 

• Specifies requirements for management reviews. 

During the preliminary phase of the audit, the approach to benchmarking and laboratory 

comparisons evolved. To provide an initial assessment of the IGL analytical capabilities, a 

comparison of the performance of the USGS with Australian and Canadian Government test 

facilities for silica (SiO2), vanadium (V), sulfur (S), chlorine (Cl), and mercury (Hg) was made 

and is summarized in table A 1.1 (Appendix A 1). The coal indicators compared were chosen 

because they influence opportunities and limitations for coal utilization. The major, minor, and 

trace elements selected are benchmark indicators of the ability to achieve complete recovery and 

acceptable consistency of results. Hg, Cl, and S are important environmental parameters. SiO2 is 

the single-most dominant constituent in both coal ash and fly ash, and V provides a good gauge 

of a laboratory’s ability to perform trace element analyses. This preliminary comparison included 

9 laboratories from both the United States and the world that regularly perform analysis of coal 

and coal-derived ash. The use of proficiency graphs provided a method of identifying suspect 

analytical trends that might require remediation. 

The Horwitz function, which provides a powerful performance benchmark to quantify 

laboratory performance, was utilized for the complete comparison of all analytical parameters for 

the final Phase 1 report (Appendix A.2). Dr. William Horwitz is a pioneer and leading advocate 

of interlaboratory method performance studies (Chemistry International, 2000). In such studies, 

the organizer normally distributes a set of test materials to the participant laboratories that 

analyze them blind by a strictly defined method. The results are returned to the organizer, who 

calculates two fundamental measures of the performance of the analytical method, the 

repeatability (within laboratory standard deviation) and the reproducibility (between laboratory 

standard deviation). 

4
Over 10,000 analytical methods subjected to a collaborative trial were examined by Dr. 

Horwitz. He noticed that as the concentration of the analyte decreased over two orders of 

magnitude, the reproducibility relative standard deviation (RSD) increased by a factor of two. 

Therefore, at 100 percent concentration of analyte the RSD was about 2 percent, at 1 percent the 

RSD was about 4 percent, and at 0.01 percent or 100 parts per million (ppm), the RSD was about 

8 percent. This pattern persisted at least down to part per billion (ppb) levels. These findings 

gave rise to the famous ‘Horwitz Trumpet’ (fig. 1), which depicts the relationship expressed as a 

two-sided one-sigma confidence interval (Thompson, 2004). The Horwitz function or “curve” is 

expressed by the following equation: 

RSD = C -0.1505, where: 

RSD = Relative standard deviation 

 C = Concentration of analyte (weight fraction) 

The "Horwitz Trumpet"

-40

-30

-20

-10

0

10

20

30

40

10 ppb 100 ppb 1 ppm 10 ppm 100 ppm 0.1 wt % 1 wt% 10 wt% 100 wt%

Concentration of analyte

% RSD Reproducibility

Figure 1. The famous ‘Horwitz Trumpet’ that depicts the relationship expressed as a two-sided, 

one-sigma confidence interval (after Horwitz and others, 1980). The trumpet shape of the two 

curves reflects the inverse relationship between analyte concentrations and the RSD (relative 

standard deviation). 

This function expresses the reproducibility relative standard deviations that can be 

expected for any concentration level when competent laboratories use optimized test procedures 

to analyze any matrix for any analyte. It may be used to set aim uncertainties against which to 

5
plan new standard test methods and to assess the performance of existing test methods (ASTM 

International, 2006b). The Horwitz function has gained wide acceptance as a powerful 

evaluation tool as evidenced by the following: 

• It is recognized by the International Union of Pure and Applied Chemists (Pocklington, W. 

D., 1990, Chemistry International, 2000) and employed by the International Association of 

Geoanalysts GeoPT proficiency testing scheme (International Association of Geoanalysts, 

2001) as a fundamental benchmark for comparing laboratory results. 

• It can be employed to compare laboratory results with certified or reference values as well as 

known values from proficiency test programs. 

• It was developed from over 10,000 independent certification, method validation and 

proficiency studies covering a wide range of materials, concentration, and measurement 

techniques. 

Horwitz Function (Log Log Scale)

RSD % = C

-0.1505

1

10

100

1 ppb 10 ppm 100 ppb 1 ppm 10 ppm 100 ppm 0.1 wt% 1 wt% 10 wt% 100 wt%

Weight Fraction (C)

RSD %

2

Certified

Reference

Routine

3

Figure 2. The Horwitz Function plotted on a log-log scale (RSD is the relative standard deviation). 

Certified analyses represent a performance ratio of 1.0 or less. Reference analyses represent a 

performance ratio of 2.0 or less but greater than 1.0. Routine analyses represent a performance 

ratio 3.0 or less but greater than 2.0. Ratios greater than 3.0 indicate either the laboratory or the 

method employed by the laboratory are not capable of consistently producing acceptable results. 

The Reference line in this figure is equivalent to the Horwitz curve in fig. 1. 

To facilitate use of the Horwitz function in evaluating laboratory performance, it is useful 

to plot the function on a log-log scale (fig. 2). The “reference” line on fig. 2 corresponds to the 

6
Horwitz curves plotted on fig. 1. Dividing the standard deviation of a method ILS or of 

laboratory proficiency testing program (PTP) results over a series of samples, by that predicted 

by the function, yields a Horwitz performance ratio. A low Horwitz performance ratio is an 

indicator of highly reliable analytical results. 

QAI recognized several levels of performance: Class 1, appropriate for “certified” 

analysis, constitutes a Horwitz performance ratio of 1 or less; Class 2, appropriate for “referee” 

(reference) analysis, constitutes a performance ratio of less than or equal to 2 but greater than 1.; 

and Class 3, appropriate for “routine” analysis, constitutes a performance ratio of less than or 

equal to 3 but greater than 2. Ratios greater than 3 indicate the laboratory or the method 

employed by the laboratory are not capable of consistently producing acceptable results. 

This report includes a series of performance tables designed to provide the ability to 

determine the capability of a laboratory “at a glance”. The Horwitz PTP performance ratio for 

each laboratory as well as the Horwitz method ILS performance ratio for the best state of the art 

ASTM International standard for each parameter is shown in tables A.1.1, A.1.2, and A.1.3 in 

Appendix A.2. A “blue” performance ratio in the tables indicates the laboratory or method is 

capable of producing certified results (maximum relative analytical error of 1 percent at 100 

percent concentration). A “green” performance ratio in the tables indicates the laboratory or 

method is capable of producing reference results (maximum relative analytical error of 2 percent 

at 100 percent concentration). An “orange” performance ratio in the tables indicates the 

laboratory or method is capable of producing routine results (maximum relative analytical error 

of 3 percent at 100 percent concentration). Performance ratios greater than a maximum relative 

analytical error of 3 percent (at 100 percent concentration) are shown in black. The minimum 

goal of a laboratory should be to achieve a performance ratio at least equivalent to the reference 

standard. It is possible for a laboratory to achieve a lower performance ratio (better results) than 

the reference standard by establishing more rigorous control over environmental, sample 

preparation, and/or instrumental conditions than specified in a given standard. 

The use of CANSPEXTM results throughout the preliminary phase of this proficiency 

audit was essential for making recommendations for improvements that were initiated and 

monitored in subsequent phases. The IGL has participated in the CANSPEXTM intralaboratory 

PTP since 1999. CANSPEXTM is a proficiency testing service that assists a laboratory at 

becoming more competent in performing measurements. Participation in PTPs is a key element 

of good laboratory practice cited in ISO 17025, “General Requirements for the Competence of 

Testing and Calibration Laboratories” (ISO, 2005). Proficiency testing programs should be 

employed by an analytical laboratory to determine the “health” of their quality system. In PTPs, 

analytical performance is measured against samples of known composition (but without any 

identification information) that are submitted to the participating laboratories at periodic 

intervals. These PTPs normally assimilate results from their participants and return nothing 

more than a statistical analysis of the data. This approach is no longer adequate in the testing 

environment of today. CANSPEXTM provides the laboratory specific information on those 

factors that are affecting both short and long term quality control. Currently 114 laboratories 

from 20 countries take part in the CANSPEXTM program. For the sake of objectivity, laboratory 

comparisons for this audit covered the period of time for which the IGL facility has been 

reporting results to CANSPEXTM. 

7
Summary of Findings 

The overall approach utilized for this performance audit of the IGL was successful and 

achieved all of the original major goals of the process. The adoption of the phased method audit 

not only furnished an assessment of the current laboratory performance, but also provided a 

mechanism for implementing and verifying the effectiveness of the recommendations. The 

overall constructive process further strengthened the IGL’s analytical capabilities while, at the 

same time, provided improved laboratory safety conditions and offered a net decrease in 

operating costs. 

Phase 1: Preliminary Proficiency Assessment 

Phase 1 actually consisted of two separate tasks with formal reports generated for each 

activity. The initial audit report dated June 01, 2004 (Appendix A.1) was effective in identifying 

significant areas that needed improvement and in prescribing preliminary recommendations for 

corrective measures to be implemented by the IGL. The final audit report dated September 10, 

2004 (Appendix A.2) supported and refined the recommendations of the initial report. The 

findings of the Phase 1 preliminary assessment results are summarized below: 

• The USGS IGL is one of the two top laboratories included in this assessment for the 

determination of trace analytes in coal-derived ash. 

• Table A.1.1 (Appendix A.1) clearly indicated that there were several performance issues at 

the IGL that needed to be addressed. 

• Inconsistent results for some major and minor elements parameters were documented 

leading to a recommendation to modify the sample digestion protocol. This modification 

will not only sustain a high level of performance for trace element analyses, but also 

improve reliability, reduce costs, and increase the safety of performing major and minor 

parameter analyses by eliminating the perchloric acid digestion procedure. Actually, this 

recommendation should also provide modest improvements to the performance on trace 

element analyses as well. 

• An expanded panel of Certified Reference Materials (CRMs) and Reference Materials 

(RMs) will also improve reliability of mercury and sulfur analyses. 

• Converting to ASTM D 6721 (ASTM International, 2006) for chlorine analysis with the 

purchase of a direct combustion instrument will extend the range, significantly improve the 

quality of the results, and reduce the cost of chlorine analyses (figs. A.1.2 and A.1.5). 

• Even with all the recommended capital purchases, an estimated net decrease in operating 

expenses of about $100,000 over a four year period (table A.2.X1.1, Appendix A.2) is 

projected. ). Savings are attained from both a reduction of consumables and in manpower 

requirements. 

• The USGS contract laboratory, Geochemical Testing, achieved one of the highest levels of 

performance in this assessment for contract parameters (table A.2.3, Appendix A.2).

Phase 2: Reconciliation of Preliminary Audit Recommendations 

Following the preliminary audit, Phase 2 was devoted to implementation of the 

recommendations generated from Phase 1. Some of the recommendations were straightforward 

and involved minor expenditures while others required significant financial commitments. 

The use of the additional recommended reference materials should improve the reliability 

of sulfur and mercury analyses. The suite of available CRMs and RMs was expanded through 

8
the purchase of the suggested materials. This was accomplished promptly and with minimal 

expense. 

A significant methodology modification was the conversion to the acid mix prescribed in 

ASTM D 6349 and D 6357 (ASTM International, 2006) followed by hot block digestion for the 

dissolution of coal-derived ash. This recommendation required the purchase of several hot block 

units from Environmental Express, Mt. Pleasant, S.C. The hot block digestion replaced two 

separate digestions (graphite sinter and Teflon acid digestion) that had been employed by the 

IGL to carry out major, minor and trace element analyses. Changing to this single digestion 

procedure not only significantly reduced operator time and consumables, but also improved the 

safety of the preparation procedure. The hot block digestion eliminated the need for perchloric 

acid, which demands extreme safety precautions requiring a specialized fume hood. 

Furthermore, since a fluxing agent is not required, the solids loading on the Inductively Coupled 

Plasma Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma - Atomic Emission 

Spectrometer (ICP-AES) systems are significantly reduced. One final benefit is that the hot 

blocks can also be employed for the acid extraction of mercury by ASTM D6414 (ASTM 

International, 2006). 

The most significant recommended change in terms of cost expenditures was the 

adoption of ASTM D6721 (ASTM International, 2006) standard for chlorine by the direct 

combustion method. A TOX-100 analyzer, which is capable of meeting the requirements of 

ASTM D6721 (ASTM International, 2006), was purchased from COSA Instrument Corporation, 

Norwood, NJ. The Eschka ignition method, which had been employed by the IGL for the 

preparation of coal samples for chlorine analysis (ASTM D2361, ASTM International, 2006), is 

known to yield highly erratic and inconsistent recovery (and demonstrated by the Chlorine 

Expanded Uncertainty Proficiency graph (fig. A.1.X1.2, Appendix A.1; and table A.2.3, 

Appendix A.2). 

An additional benefit of the Phase 1 recommendations was the potential for significant 

cost savings in addition to improved analytical performance. A revised estimation of the 

substantial anticipated cost savings for all of the recommended changes is found in table 

A.2.X1.1 (Appendix A.2). Savings are attained both in a reduction of consumables and in labor 

requirements. 

Phase 3: Reassessment of Performance and On-site Evaluation 

After the recommended changes were implemented and the sample preparation and 

analytical equipment was received, commissioned, and a reasonable training and trial testing 

period was completed, a reassessment of the performance of the IGL was conducted as part of 

Phase 3 of the performance audit. Specifically, reassessment of the performance results from 

chlorine determinations and the digestion procedures for major oxides were completed. 

Additionally, an on-site audit of the IGL facilities in Denver, CO USA was completed in 

September, 2005. 

Twenty samples distributed through CANSPEXTM from 2000 to 2004 were submitted to 

the USGS IGL as “blind” samples (the expected chlorine concentration was not known to the 

laboratory). Appendix B.1 presents the findings of the chlorine reassessment. The chlorine 

analyses are summarized in tables B.1.1 and B.1.2 (Appendix B.1). The chlorine results 

produced, employing ASTM D 6721 (ASTM International, 2006) for these samples, exhibited a 

marked improvement in accuracy without any degradation in precision, particularly for samples 

with less than 500 μg/g of chlorine. The 20 samples selected cover a wide range of coal rank 

9
and grade and represent coals from 9 different countries. Most importantly, no other 

CANSPEXTM laboratory achieved as high a level of performance for chlorine as the IGL for 

these 20 CANSPEXTM samples. Only one of the 20 IGL results was ranked in the “suspect” 

range. The IGL result for this sample analysis, combined with similar results from other 

laboratories using the same method, suggests that the certified value for chlorine for this sample 

may need to be reassessed. 

Appendix B.2 presents the findings of the major, minor, and trace element reassessment. 

Evaluation of CANSPEXTM results in Phase 1 resulted in a recommendation that the IGL convert 

from a sinter-acid digestion procedure (including use of perchloric acid) for decomposition and 

dissolution of coal derived ash to the mixed-acid decomposition and dissolution recommended in 

ASTM D6349 (ASTM International, 2006). During the reassessment in Phase 3, the IGL 

performed the mixed-acid digestion on four separate test portions of 21 CANSPEXTM samples 

covering the period of 1999 to 2004. Of the 21 samples subjected to the recommended mixedacid digestion procedure, 18 were samples prepared by QAI. The remaining three were CRMs 

from three independent certifying bodies: the Canadian Certified Reference Materials Program 

(CCRMP), the National Institute of Standards and Technology (NIST) USA, and the USGS. 

These CRMs are employed world wide for the calibration and control of procedures employed 

for the determination of major oxides. The homogeneity of all three CRMs is verified by the 

respective certifying agencies. To eliminate any objections concerning the homogeneity of the 

QAI samples, this evaluation was limited to results from the three CRMs. The CRMs used were 

USGS GSP-2 (granodiorite), CCRMP SY-4 (diorite gneiss), and NIST 1633b (coal fly ash). All 

three chosen CRMs pose especially difficult analytical challenges. From the results presented in 

table B.2.3 (Appendix B.2), it is evident that there are significantly more quality exceptions for 

the sinter-acid procedure than for the recommended mixed-acid digestion procedure. This 

validates the Phase 1 recommendation to adopt a mixed acid, hot block digestion for dissolution 

of coal-derived ash. 

There were a particularly significant number of exceptions between the previously used 

sinter-acid and the recommended mixed-acid digestion procedures for the NIST 1633b sample in 

table B.2.3 (Appendix B.2). Of the three CRM samples, NIST 1633b is the only sample that 

contains combustible carbon. The amount of unburned carbon is in the order of 3.4 weight 

percent. The NIST 1633b test portions treated by the sinter-acid digestion procedure were not 

preignited at a temperature sufficient to remove this combustible carbon. The IGL confirmed the 

sinter-acid digestion solutions contained a visible gray residue, which is an indicator of the 

presence of unburned carbon. This residue not only has the potential to absorb soluble oxides, 

but also to create erratic flow of the sample through the ICP nebulizer. When all three CRM 

samples were preignited at a temperature that not only eliminates combustible carbon but also 

decomposes mineral carbonates, sulfides, and hydrates prior to treatment by the recommended 

mixed-acid digestion procedure, no visible residue was observed. Based on the above 

observation, it was emphasized that all samples should be preignited as recommended in the 

section on preparation of ash in ASTM D6349 (ASTM International, 2006). 

Finally, both table B.2.3 and the graphs (figs B.2.1-8) in Appendix B.2 provide strong 

evidence that a significant shift in nebulization is occurring from sample to sample during the 

ICP analysis. It was recommended that this effect be monitored and reconciled by using one or 

more internal standards added to each analysis solution. 

An on-site evaluation of the IGL was conducted on September 12-14, 2005 and a report 

was completed (Appendix B.3). The purpose of this evaluation was two-fold. The first goal was 

10
to observe the laboratory operations first hand and to verify that recommendations made during 

the performance audit had been properly implemented as well as to making additional 

recommendations as appropriate. The on-site audit confirmed recommendations for analytical 

practices intended to improve the efficiency and reliability of test results have been implemented 

and are being monitored on an on-going basis to substantiate the effectiveness of the 

recommendations. The recent implementation of a blind testing program should provide the 

recommended ongoing, real time monitoring of laboratory performance. 

The second goal was to assist the IGL in the finalization of IGL standard operating 

procedures (SOPs) for every significant analytical procedure as part of developing a total quality 

management system. Because there was not sufficient time to perform a detailed analysis of 

each analytical process, much of the on-site report contains a summary of best practices. The 

recommendations and examples included in this report do not necessarily constitute current or 

future practices or procedures employed at the IGL. The USGS management and IGL staff is 

currently reviewing the recommendations and examples to decide whether they can be in whole 

or in part incorporated into current SOPs without adversely impacting the quality of results 

produced. The full report of the On-site Evaluation (Appendix B.3) can be referenced for specific 

information. For the sake of brevity, only the principal topics that were addressed are listed 

below: 

Collection of Coal Samples 

Collection of Ash Samples 

Sample Preparation, Storage and Handling 

• Preparation of coal samples for analysis 

• Preparation of ash samples for analysis 

Quality Control 

• Instrument maintenance 

• Validated operators 

• Instrument conditioning 

• Acceptance limits for calibration and control samples 

• Calibration and calibration verification 

Establishment and Use of Control charts, Method Specific SOPs 

Moisture 

• International, Regional and National standards 

• Type of purging atmosphere (accuracy) 

• Dryness of purging atmosphere (precision and accuracy) 

• Insufficient drying time (precision and accuracy 

• Concurrent drying coals of significantly different rank (precision) 

• Cooling and weighing of samples (precision and accuracy) 

Ash 

• International, Regional and National standards 

• Incineration of the sample (precision) final soak temperature (precision and 

accuracy) 

• Concurrent ashing coals of significantly different rank (precision) 

• Cooling and weighing of samples (precision and accuracy) 

Sulfur 

• International, Regional and National standards 

• Verification of the operating conditions (precision and accuracy) 

11
• Analyzer calibration (Precision and Accuracy) 

• Premature Termination of sulfur Analysis Cycle (Precision and Accuracy) 

Chlorine 

• International, Regional and National standards 

• Situation and handling of instrument components and samples (precision and 

accuracy) 

• Preparation of the apparatus (precision and accuracy) 

• Analyzer calibration (precision and accuracy) determination chlorine content 

(precision and accuracy) 

• Limits of application of standard methods (precision and accuracy) 

• Bomb decomposition as a reparation technique (precision and accuracy) 

Mercury 

• International, Regional and National standards 

• Acid extraction/wet oxidation as a preparation technique (precision and accuracy) 

• Sample Digestion 

• Analyzer calibration (precision and accuracy) 

• Limit of application of standard methods (precision and accuracy) 

• Bomb decomposition as a preparation technique (precision and accuracy) 

• Direct combustion for the analysis of mercury (precision and accuracy) 

Major and Minor Elements 

• International, Regional and National standards for major an minor oxides 

• Analyzer calibration (precision and accuracy) 

Trace Elements 

• International, Regional and National standards for trace constituents 

• Analyzer calibration (precision and accuracy)

Many of the quality control measures discussed in Appendix B.3 are already in place. 

Perhaps the biggest challenge highlighted in the on-site report is the issue of sampling, handling, 

and preparation. The most fundamental principle of sampling is to try to ensure that each sample 

collected is representative of the intended purpose. Other sample issues include the concept of 

minimum sample size (dependent on size consist of the material being sampled) and improper 

sample packaging leading to loss of moisture or sample oxidation. 

No amount of analytical competence and/or quality control can rectify and overcome 

samples that were improperly collected, handled, or prepared. While these problems are largely 

outside the IGL’s direct scope of responsibility, it was recommended that there needs to be close 

coordination between the sample collectors/submitters and the IGL personnel. Practices 

employed to collect samples should be compared with the procedures cited in Appendix B.3. If it 

is not possible to implement comparable procedures, the IGL should implement procedures that 

can identify sources and causes of sample variability that could detract from the reliability of 

analytical results.

Measurable Benefits of the Performance Audit 

Even though the Phase 3 reassessment program documented significant improvements as 

a result of specific recommendations, it seemed appropriate to ascertain if improvement in the 

overall performance of the IGL was being sustained following the laboratory audit. To 

accomplish this, a trend analysis that compared pre-and post-audit analytical performance was 

conducted. 

12
A relatively straightforward analysis was devised whereby performance ratios were 

calculated for individual parameters for each CANSPEXTM sample during the period prior to the 

audit and all CANSPEXTM samples analyzed following the audit. Parameter results were 

classified either “acceptable” or “suspect”. Acceptable results are those performance ratios with 

a precision and accuracy that fall within CANSPEXTM three standard deviation limits. Suspect 

results are those with a precision or accuracy or both that fall outside CANSPEXTM three 

standard deviation limits. A tally of all individual ratio results was made. Table 1 contains the 

pre- and post-audit results for each individual parameter. Table 2 provides a summary both 

numerically and as percentages. 

Table 1. Compilation of IGL CANSPEXTM results before and after the performance audit. 

Acceptable results are those with a precision and accuracy that fall within the CANSPEX 3 

standard deviation limits. Suspect results are those with a precision or accuracy or both that fall 

outside the CANSPEX 3 standard deviation limits. [BA = Before Audit; AA = After Audit] 

Parameter Coal Ash S Cl Hg 

Rating BA total AA total BA AA BA AA BA AA BA AA

Acceptable 19 21 6 6 5 6 3 4 5 5 

Suspect 5 1 3 0 1 0 0 0 1 1 

Parameter Mineral Oxides SiO2 Al2O3 Fe2O3 CaO MgO Na2O K2O P2O5 TiO2 BaO SrO 

Rating BA total AA total BA AA BA AA BA AA BA AA BA AA BA AA BA AA BA AA BA AA BA AA BA AA

Acceptable 45 51 0 3 5 4 4 5 2 5 6 4 2 4 4 4 7 6 4 4 6 6 5 6 

Suspect 24 7 5 2 2 1 2 0 3 0 1 1 4 1 2 1 0 0 2 1 1 0 2 0 

Parameter Trace Components As Be Cd Co Cr Cu Mn Ni Pb Sb V Zn 

Rating BA total AA total BA AA BA AA BA AA BA AA BA AA BA AA BA AA BA AA BA AA BA AA BA AA BA AA

Acceptable 73 57 6 5 7 5 6 4 7 4 7 5 6 5 6 5 7 5 4 5 7 5 6 5 4 4 

Suspect 5 2 0 0 0 0 0 0 0 1 0 0 0 0 1 0 0 0 1 0 0 0 1 0 2 1 

On a parameter-by-parameter basis, the approach used to develop tables 1 and 2 is not 

considered statistically rigorous as the sample populations were limited for the post audit 

samples and not all of the recommended changes were implemented precisely at the same time. 

However, this relatively simple analysis shows significant collective trends in performance 

improvement, especially in those problem areas identified in the preliminary assessment in Phase 

1 of the audit. The results expressed as percentages (table 2) are especially helpful for 

demonstrating the post-audit performance gains. Performance on both the coal parameters 

including sulfur and chlorine as well as major and minor oxides analyses improved significantly 

showing a dramatic decrease in the percentage of suspect results from 21 to 5 percent and from 

35 to 12 percent respectively (table 2). Most importantly, excellent performance on the analysis 

of trace elements was not only maintained through the effected changes, but modest performance 

improvements were also realized with percentage of acceptable results before and after rising 

from 94 percent to 97 percentage respectively. 

13
Table 2. Summary of IGL CANSPEXTM results before and after the performance audit analyses 

from table 1 expressed both numerically and as percentages. Acceptable results are those with 

a precision and accuracy that fall within the CANSPEX 3 standard deviation limits. Suspect 

results are those with a precision or accuracy or both that fall outside the CANSPEX 3 standard 

deviation limits. 

Parameter Coal (Ash, Sulfur, Chlorine, Mercury) 

Number of Results Percentages 

Rating Before 

Audit 

After 

Audit 

Before 

Audit 

After 

Audit 

Acceptable 19 21 79% 95% 

Suspect 5 1 21% 5% 

Parameter Major/Minor Oxides 

Number of Results Percentages 

Rating Before 

Audit 

After 

Audit 

Before 

Audit 

After 

Audit 

Acceptable 45 51 65% 88% 

Suspect 24 7 35% 12% 

Parameter Trace Elements 

Number of Results Percentages 

Rating Before 

Audit 

After 

Audit 

Before 

Audit 

After 

Audit 

Acceptable 73 57 94% 97% 

Suspect 5 2 6% 3% 

Future Work 

While the recently completed performance audit of the IGL represents attainment of an 

important benchmark, it is not a final goal by itself, but simply a significant step in the process of 

continuous improvement in quality assurance. Furthermore, this performance audit is not a onetime process. As part of a best practices philosophy of management, additional external 

performance audits will be performed at appropriate intervals per ISO 17025 regardless of 

perceived analytical performance. 

A major additional step towards enabling the IGL to become recognized as a competent 

practitioner of analyses based on a performance based testing was the implementation of a 

“double blind” testing program in fiscal year 2006. A double-blind check sample is one that 

laboratory personnel do not know is an external check sample. Blind samples have the same 

characteristics of routine samples and are delivered along with normal samples batches without 

special notice. The current double-blind audit program consists of the submittal of at least two 

samples per month of coal and coal ash to the IGL and a monthly, real-time summary evaluation 

14
report of the analytical results by QAI. Any discrepancies are immediately identified and timely 

remedial action is taken. Thus, a double-blind program, conducted by a third party, provides realtime, objective assessment of laboratory competency through traceability to recognized reference 

materials and certified reference materials. As a result, double-blind results are the ultimate test 

of analytical design performance., 

Conclusions 

The format and results of the external performance audit of the IGL by Quality 

Associates International® LDT proved very successful. The phased approach and constructive 

nature of the process with tools to measure performance should be considered as a blueprint for 

subsequent external laboratory reviews. The significant results and findings of this audit are: 

1) Participation in an external, proficiency testing program is a valuable component in the 

development of a successful quality assurance system. 

2) The USGS IGL was one of the two top laboratories included in this performance assessment 

for the determination of trace analytes in coal derived ash. 

3) Inconsistent results for some major and minor parameters were identified. Several 

recommendations were made to correct deficiencies including expanding the use of certified 

reference materials, purchasing new preparation and analytical equipment, and modifying the 

sample digestion procedures. The adoption of the audit recommendations resulted in not only 

improvements in analytical reliability, increased productivity, and lowered consumable costs, 

but also a safer working environment. 

4) The USGS contract laboratory (Geochemical Testing) achieved one of the highest levels of 

performance in this assessment for contract parameters. 

5) Performance comparisons on CANSPEXTM sample performance both pre- and post-audit 

confirmed significant performance gains, especially for major and minor oxides and elemental 

parameters while sustaining proficiency on trace element analyses. 

6) A working environment that optimizes staff involvement in quality assurance was enhanced. 

7) A double-blind-testing program was recently implemented. This program will provide an 

additional level of analytical competence verification by providing frequent monitoring and 

documentation of performance to help sustain gains made by the audit. 

8) A commitment to continuous improvement of quality assurance and performance as an 

ongoing practice was reconfirmed. 

A laboratory that is committed to an operating environment founded on the principles of 

a performance based testing approach should not view audits with apprehension, but look at the 

process as additional opportunities for verification of analytical proficiency. 

Acknowledgments 

The authors wish to thank Curtis Palmer, USGS, Reston, VA and Margaret Ellis, USGS, 

Denver, Colo., for their helpful reviews of this work. 

15
References Cited 

ASTM International, 2006, Annual Book of ASTM Standards, Section 5, Petroleum Products, 

Lubricants and Fossil Fuels: v. 05.05 Gaseous fuels; coal and coke: ASTM International, West 

Conshohocken, Pennsylvania, 705 p. 

ASTM International, 2006b, E2165-01 Standard Practice for Establishing an Uncertainty Budget 

for the Chemical Analysis of Metals, Ores, and Related Materials: ASTM International

Document Summary, http://www.astm.org/cgibin/SoftCart.exe/DATABASE.CART/REDLINE_PAGES/E2165.htm?L+mystore+qhid4467.

Chemistry International, 2000, William Horwitz receives Robert Boyle Medal from Royal 

Society of Chemistry: Chemistry International, Vol. 22, No. 6, November 2000,

http://www.iupac.org/publications/ci/2000/november/awards_horwitz.html

Horwitz, W., Kamps, L.R., and Boyer, K.W., 1980, Quality assurance in the analysis of foods for 

trace constituents: Journal of Association of Analytical Chemistry, 1980, v. 63, no. 6, p. 1344-

1354. 

International Association of Geoanalysts, 2001, Ninth International proficiency test of analytical 

geochemistry laboratories: International Association of Geoanalysts, GEOPT9/OU-6; 

http://geoanalyst.org/geopt9.html

ISO, 2005, 17025:2005(E), General Requirements for the competence of testing and calibration 

laboratories: ISO (the International Organization for Standardization) and IEC (the 

International Electrotechnical Commission), Geneva, Switzerland, 36 p.,

http://www.iso.org/iso/en/ISOOnline.frontpage 

Pocklington, W. D., 1990, Harmonized protocols for the adoption of standardized analytical 

methods and for the presentation of their performance characteristics: International Union of 

Pure and Applied Chemists, Journal of Pure & Applied Chemistry, v. 62, no.1, pp. 149-162, 

http://www.iupac.org/publications/pac/1990/pdf/6201x0149.pdf.

16
 

Appendix A. 

Phase 1: Preliminary Evaluations of Quality System and 

Recommendations 

Appendix A.1: Preliminary Evaluation of Quality System and Recommendations; Initial 

Report, June 01, 2004 

Appendix A.2: Preliminary Evaluation of Quality System and Recommendations, Final 

Report, 2 September 10, 2004 

The following appendices do not conform to USGS form and style. They also contain multiple 

reference citations to standard methods and other contacts. To facilitate review of the documents 

the reference was not provided every time a standard test method or organizational contacts were 

cited. Information regarding these citations is provided Appendix B.4. 

17
Appendix A.1 

 

 Phase 1: Preliminary Evaluation of Quality System and 

Recommendations; Initial Report 

 

 

Performance Audit of U.S. Geological Survey Inorganic Geochemistry and 

Contract Laboratories 

 

 

Requisition #3-2920-1052 

 

 

 

June 01, 2004 

 

 

 

 

Louis Janke, President 

Quality Associates International®

, LDT. 

P.O. Box 117 

Douglas, ON K0J 1S0 

Canada 

 

18
Introduction 

The data generated and the expertise of Inorganic Geochemistry Laboratory (IGL) personnel 

remains a critical support component of the Energy Resources Program’s (ERP’s) programs. 

Increased emphasis throughout the coal industry on understanding the impacts of production and 

usage of coal including the effects of mercury, arsenic, and other toxic elements will ensure that 

the major, minor and trace element results generated by the IGL will have increased visibility 

and importance. 

Since that sample suite analyzed is literally worldwide, the primary goal of the Quality 

Management System (QMS) should be to ensure the USGS continues to maintain a high level of 

confidence that the Denver laboratory continues to produce data that are of the requisite accuracy 

for not only the US but also the global coal community. 

To meet this goal the objectives of this USGS quality system review can be summarized as 

follows: 

• Produce high quality data 

• Lower operational costs 

• Create a working environment that optimizes staff involvement in quality improvement 

• Positions the laboratory to become a recognized competent practitioner of performance 

based testing an approach to the assessment and maintenance of laboratory competency that 

is being adopted by major standards writing organizations worldwide including ASTM 

International and ISO. 

Executive Summary 

To provide an initial assessment of the IGL analytical capabilities, a comparison of the 

performance of USGS with Australian and Canadian Government test facilities for sulfur (S), 

chlorine (Cl), mercury (Hg), silica (SiO2) and vanadium (V) is summarized in table A.1.1. The 

coal indicators were selected as they dictate opportunities and limitations for the utilization of 

coal. The major, minor, and trace elements were selected because they are benchmark indicators 

of the ability to achieve complete recovery and acceptable consistency of results. Hg, Cl, and S 

are all important environmental parameters. SiO2 is the single-most dominant constituent in both 

in coal ash and fly ash and V provides good gauge of a laboratory’s ability to perform trace 

element analyses. This preliminary comparison includes 9 laboratories from the USA and around 

the world that regularly perform analysis of coal and coal-derived ash. Results employed for the 

comparison were obtained from the Quality Associates International Ltd. (QAI) CANSPEXTM 

proficiency improvement program. 

CANSPEXTM is proficiency test service that assists a laboratory at becoming more competent in 

performing measurements. Participation in proficiency testing programs (PTP) is a key element 

of good laboratory practice cited in ISO 17025, General Requirements for the Competence of 

Testing and Calibration Laboratories. PTPs should be employed by a testing laboratory to 

determine the “health” of their quality system. Most PTPs assimilate results from their 

participants and return nothing more than a statistical analysis of the data. In the testing 

19
environment of today, this approach is no longer adequate. CANSPEXTM provides the laboratory 

specific information on those factors that are affecting both short and long-term quality control. 

Currently 95 laboratories from 18 countries take part in the CANSPEXTM program. 

For the sake of objectivity, this comparison (table A.1.1.) covered the period of time for which 

the IGL facility has been reporting results to CANSPEXTM. A rank of 1 indicates the laboratory 

is the most proficient of the 9 laboratories, a rank of 9 indicates the laboratory is the least 

proficient. The proficiency graphs (figs. A.1.X1.1-5) appear in Appendix X1 of this report.

Geochemical Testing, which performs contract analysis for the USGS, is also included in this 

comparison. An evaluation of the performance of Geochemical Testing for the contract 

parameters Proximate-Ultimate-Btu, Forms of sulfur, Ash Fusion Temperatures along with any 

recommendations shall be provided to the USGS by the end of July, 2004. In addition, a 

complete set of graphs shall be supplied for the full suite of measurements conducted by the 

USGS. 

Table A.1.1. Relative proficiency ranking for a nine laboratory comparison. A rank of 1 

indicates the laboratory is the most proficient of the 9 laboratories, a rank of 9 indicates the 

laboratory is the least proficient. 

Relative Proficiency Ranking 9 Laboratory Comparison 

Parameter Australia Canada USGS U.S. Commercial Lab 

Silica 6 4 9 5 

Vanadium 5 8 6 1 

Sulfur 5 1 8 4 

Chlorine 4 3 9 7 

Rank Sum 20 16 32 17 

Mercury 3 4 8 

Rank Sum 23 36 25 

The results from table A.1.1 clearly indicates that there are performance issues at the IGL 

that need to be addressed. Based on this comparison, QAI has developed recommendations to 

be implemented by the Denver laboratory that will promote achievement of the objectives cited 

in the introduction. Once the recommendations have been instituted, a final assessment shall be 

conducted to identify and quantify improvements. This approach will allow the Denver 

laboratory to reach the primary goal of consistently producing data that are of the requisite 

accuracy for not only the US, but also for the global coal community at a level of proficiency 

commensurate with that demonstrated by peer agencies worldwide. 

Recommendations 

The recommendations provided in this report require a total capital investment of approximately 

$43,000. In addition to significantly increasing the reliability of results, it is anticipated that the 

USGS will recover the capital investment within 1 year and realize an increased man-hour and 

consumable margin equivalent to $85,000 over a period of 4 years. These estimates are 

20
summarized in the Table A.1.2. Each recommendation appears in a separate section of this 

report. 

Table A.1.2. Estimation of cost savings from recommendations. 

Recommendation Description Year 1 Year 2 Year 3 Year 4 Totals 

1, 2, 3 CRM/RM $1,185 $645 $645 $645 $3,120 

2 TOX Cl Analyzer ($26,850) $13,150 $13,150 $13,150 $12,600 

3, 4 Test Hot Block $15,250 $18,250 $18,250 $18,250 $70,000 

Resource Net (Expense) Savings ($10,415) $32,045 $32,045 $32,045 $85,720 

CRM Certified Reference Material 

RM Reference Material 

Net Negative yearly costs shown in parentheses 

Recommendation 1: Sulfur 

1) The USGS can increase the proficiency of sulfur analysis by obtaining the Certified 

Reference Material (CRM) and Reference Material (RM) coals listed in blue in table A.1.3. 

Table A.1.3. Recommended purchases of certified reference and reference materials. 

Sample 

Available 

From 

Weight (g) Per 

Bottle 

S wt 

% Cl 

Hg 

ng/g Cost

Current 

Use 

Current 

Cost 

Forecast 

Use 

Forecast 

Cost 

SARM 

20 SABS 250 0.51 NTV 250 $350 0 $0 0.5 $175 

1632c NIST 50 1.46 1139 94 $380 2 $760 1 $380 

2684b NIST 50 3.08 NTV 97 $160 0 $0 1 $160 

ES-2 QAI 90 4.45 465 116 $120 0 $0 1.5 $180 

ES-6 QAI 90 0.51 90 24 $120 0 $0 1.5 $180 

2002-3 QAI 90 1.90 4935 131 $120 0 $0 1.5 $180 

CLB-1 USGS 60 1.49 1082 151 $75 2 $150 2 $150 

1633b NIST 75 0.2075 NTV 141 $300 1 $300 1 $300 

2774 Alpha 60 NTV NTV NTV $120 2 $240 0 $0 

2780 Alpha 60 NTV NTV NTV $120 2 $240 0 $0 

2782 Alpha 100 NTV NTV NTV $120 2 $240 0 $0 

1635 NIST 50 NTV NTV NTV $180 1 $180 0 $0 

0.93 Leco 60 0.93 NTV NTV $120 2 $240 0 $0 

Per Year Consumable, Man-Hour Savings $645 

Certified Values are in blue bold. 

Reference values in blue normal. 

NTV no traceable value. 

SARM 20 is available from Brammer Standards in Texas. 

21
2) In addition to the cost savings specified in table A.1.3, the CRM/ RM suite of samples offers 

the following technical advantages. 

The use of CRMs from different sources National Institute of Standards and Technology (NIST), 

South African Bureau of Standards (SABS), and USGS) will minimize certifying agency specific 

biases in USGS standardization and calibrations. The suite of CRM and RM samples selected 

includes values for critical emission species S, Cl, and Hg over a wide range of concentrations. 

The SABS SARM 20 is certified for an extensive range of trace elements (23) including U and 

Th, as well as several rare earths. SARM 20 provides approximate values for an additional 13 

trace. The NIST, SARM, ES, and 2002-3 samples have a very high degree of inter-traceability. 

They been analyzed simultaneously in a minimum of 3 different interlaboratory studies each 

involving a different group of laboratories. The CLB-1 sample was run through one of the same 

interlaboratory studies as the NIST, ES and 2002-3 samples. 

3) Use SARM 20, NIST 2684b, ES-2 2002-3 and CLB-1 for calibration of the sulfur analyzer. 

Use NIST 1632c and ES-6 to determine whether the analyzer remains in a state of control. 

4) To achieve a high level of proficiency, use the acceptance values listed in table A.1.4 for 

calibration and control samples. 

Table A.1.4. Acceptance values of certified reference and reference materials. 

CRM/RM 

Samples 

Reference 

Value 

Acceptance 

Limits 

SARM 20 0.5100 0.038 

NIST 2684b 3.0760 0.076 

ES-2 4.4500 0.097 

2002-3 1.9000 0.059 

CLB-1 1.4900 0.052 

NIST 1632c 1.4620 0.052 

ES-6 0.5100 0.038 

5) The USGS should require that the same materials be employed for all contracted out sulfur 

analysis. 

Recommendation 2: Chlorine 

1) To increase the proficiency of chlorine analysis the USGS needs to convert from the Eschka 

ignition method to ASTM method D 6721. This entails the purchase of a direct combustion 

analyzer at` a cost of approximately $40,000. A direct combustion analyzer that meets the 

requirements of ASTM D 6721 is available from COSA instruments located in Norwood, 

New Jersey. Purchase of a demo or used analyzer could significantly reduce capital outlay. 

A summary of the expected recovery of this capital investment and extended cost savings is 

summarized in table 5. 

22
Table A.1.5. The expected yearly net cost savings realized by purchase of a direct combustion 

instrument for chlorine analyses per ASTM D6721 versus current Eshka method. 

Method Consumables

Analyst Time 

(Min.) Samples 

Man 

hours Man $$ 

Total 

Costs 

ASTM 6721 $500 5 1500 125 $3,750 $4,250 

Eshka $2,400 20 1500 500 $15,000 $17,400 

Net Per Yearly Consumable and Man-Hour Savings $13,150 

In addition to the cost savings specified in table A.1.5, ASTM D 6721 offers the following 

technical advantages. 

• Method D 6721 is based on microcoulometry, which is considered a primary analytical 

method. Standardization is carried out with a pure chemical compound and does not 

require the use of CRM or RM coals. 

• Analysis and repeat analysis simply involves weighing a portion of sample and introducing 

it in the analyzer without pretreatment. As a result, the number of steps required to carry 

out the analysis of chlorine is significantly reduced in comparison to other techniques. This 

immediately reduces the number of sources of error with a subsequent improvement in the 

reliability of results. 

• Unlike bomb combustion and low temperature ignition, the method operates at 

temperatures that achieve complete recovery of chlorine from non-combustible as well as 

combustible materials. 

• Much smaller quantities of sample (20 mg to 40 mg) in comparison to other techniques 

(150 mg to 500 mg) are required to obtain reliable results. 

2) To ensure a high degree of precision employ a 5-place analytical balance to weigh all 

standardization and analysis samples. 

3) Conduct analysis of NIST 1632c, ES-2, ES-6, and CLB-1 with each batch of chlorine 

samples and keep a record of the results obtained vs. the values listed in table A.1.4 in an 

Excel spreadsheet. 

Recommendation 3: Mercury 

1) The USGS can increase and ensure continued proficiency of mercury analysis by employing 

the certified Reference material (CRM) and reference material (RM) coals selected for 

sulfur as recovery control samples. 

2) At the very least, analyze SARM 20 and one other CRM sample (NIST 1632c, 2684b, 

1633b) with each batch of mercury samples. In addition, it is good practice to include one of 

the RM samples ES-2, ES-6, or 2002-3 in each analysis batch, preferably with a mercury 

value near the expected value of the test samples. Carry out analysis of all CRM and RM 

samples in duplicate. Calculate the recovery for each sample tested. Do not normalize test 

sample values to CRM or RM values. 

23
3) Should there be a need for the USGS to contract out mercury analysis, use a laboratory with 

the capability to conduct measurements in compliance with ASTM D 6722 for coals of the 

following rank, medium volatile bituminous, low volatile bituminous, semi-anthracite, and 

anthracite. The USGS should require that the same materials employed as CRMs and RMS 

by the USGS be used for all contracted out mercury analysis. NIST 2692b should not be 

employed as a calibration or control sample as several studies have shown that this CRM is 

biased high. 

Recommendation 4: Majors, Minors and Trace Elements 

To increase the proficiency of major, minor and trace element results the USGS needs to convert 

to a preparation technique based on fusion or hot block acid digestion. The most effective 

approach for the USGS would appear to be hot block acid digestion. This entails the purchase of 

a hot block with a cost of approximately $3,000. A hot block that has proven suitable for coal ash 

is available from Environmental Express, Mt. Pleasant, South Carolina. A summary of the 

expected recovery of this capital investment and extended cost savings is summarized in table 

A.1.6. 

Table A.1.6. Net per year consumable and man-hour savings using recommended digestion. 

 

Sample Preparation Consumables

Analyst 

Time 

(Min.) 

Total 

Samples 

per Year

Total 

Man 

hours 

Total Man 

Hour Costs Total Costs

Recommended Hot Block $750 15 1500 375 $11,250 $12,000 

Peroxide Fusion: Graphite Crucibles $1,500 15 1500 375 $11,250 $12,750 

Teflon Acid Digest $2,500 20 1500 500 $15,000 $17,500 

Net Per Year Consumable and Man-Hour Savings Using Hot Block Digestion $18,250 

In addition to the cost savings specified the hot block digestion offers the following technical 

advantages. 

• The hot block digestion replaces two separate digestions graphite sinter and Teflon acid 

digestion currently employed by the USGS to carry out major, minor and trace analysis. 

• The hot block digestion eliminates the need for perchloric acid, which requires extreme 

safety precautions and can only be used in a specialized fume hood. 

• The hot block can also be employed for the acid extraction of mercury by ASTM D 6414. 

• Since a fluxing agent is not required the solids loading on the ICP-MS and ICP AES 

systems is significantly reduced. 

Hot block digestion of the ash 

The use of Teflon tubes and a heating block improves the efficiency and precision of ash 

dissolution when compared with heating the sample in a Teflon beaker on a hot plate. A 

recommended procedure employing a heating block is described below. 

Transfer 200 mg to 500 mg of ignited ash to a 60 mL Teflon tube. Add 20 mL aqua regia and 20 

mL of HF to the tube. Place the tube in a room temperature hot block. Ramp the hot block to 

24
100° C and hold at this temperature for 30 minutes. Ramp the hot block to 150° C. Maintain this 

temperature while the mixture evaporates to dryness. Do not bake the sample. 

After the solution has evaporated to dryness, rinse the tube walls with deionized water. Heat this 

solution at 150° C to dryness. Do not bake the sample. Remove the tube from the hot block. Cool 

to room temperature. Add 1 mL of HNO3 and 40 mL of deionized water to the tube. Heat the 

contents in the hot block at 110° C for one hour. Transfer to a 100 mL polypropylene volumetric 

flask. Dilute to volume with water and mix. Examine the final test solution and record the 

presence and color of any undissolved residue. Prepare a blank by using the above procedure but 

omitting the ash. 

Residue left after dissolution indicates the presence of undissolved mineral or organic matter. In 

the case of a fly ash ignited at 500 oC prior to dissolution, the undissolved material can be made 

up of refractory carbon compounds that are not readily decomposed in the ignition step or 

digested by the acids. These carbon compounds can retain trace elements. Ignition of the fly ash 

at a higher temperature can decompose these refractory compounds but can also lead to loss of 

trace elements that are volatile above 500 oC. 

To demonstrate the digestion process is remaining in an acceptable state of control, digest a 

sample prepared from an ash containing little or no organic carbon with each batch of samples. 

Once the USGS has commissioned this preparation method, Quality Associates International 

Ltd. shall provide a minimum of 6 blind ash samples for a proficiency test. 

Appendix A.1.X1. Proficiency Graphs 

An Uncertainty Primer 

Because human beings are fallible, all devices from something as simple as a tape measure to 

something as complex as a mass spectrometer designed and employed to conduct measurements 

can, and do produce, variable results. This variation in the results is called uncertainty. The 

smaller the uncertainty, the more reliable are the conclusions that can be extracted from the 

measurement system. The following example should help to clarify this point. 

A polling agency conducts a poll of voters in a randomly selected state on the outcome of an 

upcoming election. From this poll, they establish that 54 % of the voters intend to vote YES. 

They then compare this state’s results with the remaining states for the past 4 elections and 

conclude that this result could vary from 47 % to 61 % or an uncertainty of ± 7 %. The key point 

is that this poll indicates the YES’s could lose the election. 

Another agency conducts a more extensive poll of voters in all 50 states. They establish that 56 

% of voters intend to vote YES. By comparing the variation between the individual states the 

agency concludes the result could vary from 53 % to 59 % or an uncertainty of ± 3 %. The clear 

indication is that YES’s are going to win the election. The poll also provides current state-bystate results, which would allow the YES’s to focus their efforts to push the outcome closer to 

the 59 % value. 

25
In the end, the poll with the lower uncertainty not only increases confidence in the outcome of 

the election, but also optimizes use of party resources. Now suppose we wait a month and ask the 

agencies to conduct the exercise again. Most individuals would recognize that it is very unlikely 

the poll results are going to be exactly the same. In the case of the first agency, the randomly 

selected state changes and the result is 56 % expect to vote YES with an uncertainty of ± 11 %. 

In the case of the second agency, the result is 57 % expect to vote YES with an uncertainty of ± 4 

%. 

Not only are the conclusions from the two polls the same, but also it is evident that the 

measurement system employed by the second agency with a range of uncertainty (± 3 % to ± 4 

%) is more stable than the measurement system employed by the first with a range of uncertainty 

(± 7 % to ± 11 %). 

The graphs in this appendix display the uncertainty of measurements conducted for different test 

parameters by different laboratories covering periods of up to 4 years. The uncertainties are 

displayed as box plots that illustrate the average uncertainty as well as the maximum and 

minimum expected uncertainties as defined by the ends of the boxes. 

The proficiency box-plots are highlighted as follows. 

USGS Blue Lab 685 

Geochemical Green Lab 588 

Canada Red Lab 551 

Australia Orange Lab 620 

Lab classification 

Com Commercial lab 

Edu University lab 

Gen Utility lab 

Gov Government lab 

Prd Coal producer 

Country code 

AUS: Australia 

CAN: Canada 

GER: Germany 

ISR: Israel 

USA: United States of America 

Analytical Instruments: ICPAES: Inductively Coupled Plasma Argon Emission Spectroscopy; 

ICPMS: Inductively Coupled Plasma Mass Spectroscopy; ICPOES: Inductively Coupled Plasma 

Optical Emission Spectroscopy; XRF: X-Ray Fluorescence; IC: Ion Chromatography; ISE: Ion 

Selective Electrode

Figures A.1.X1.1-5 present proficiency graphs for sulfur, chlorine, mercury, silica, and 

vanadium. There are two box-plots for each laboratory. One for the entire period covered by the 

26
graph indicated as (Lab-3 or Lab-4) and one for the past year (indicated as Lab-1). The primary 

method employed by the laboratory over the period of the graph and during the past year appears 

under the country code. 

27
Sulfur Expanded Uncertainty 2001-2004

0.035 0.033

0.044

0.051

0.017 0.016

0.059

0.103

0.051

0.041

0.084

0.041

0.045

0.050

0.037

0.051

0.022

0.032

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

551-3 551-1 694-3 694-1 724-3 724-1 588-3 588-1 620-3 620-1 709-3 709-1 669-3 669-1 685-3 685-1 701-3 701-1

Gov Gov Prd Prd Com Com Com Com Gov Gov Gen Gen Gen Gen Gov Gov Com Com

CAN CAN USA USA USA USA USA USA AUS AUS USA USA GER GER USA USA USA USA

D 4239 D 4239 D 4239 D 4239 D 4239 D 4239 D 4239 D 4239 ICPAES ICPAES D 4239 D 4239 D 4239 D 4239 D 4239 D 4239 D 4239 D 4239

Uncertainty wt %

USGS Blue Lab 685 

Geochemical Green Lab 588 

Canada Red Lab 551 

Australia Orange Lab 620 

Lab classification 

Com Commercial lab 

Edu University lab 

Gen Utility lab 

Gov Government lab 

Prd Coal producer 

Country code 

AUS Australia 

CAN Canada 

GER Germany 

ISR Israel 

USA United States of America 

Analytical Instruments: ICPAES: Inductively Coupled Plasma Argon Emission Spectroscopy; 

ICPMS: Inductively Coupled Plasma Mass Spectroscopy; ICPOES: Inductively Coupled Plasma 

Optical Emission Spectroscopy; XRF: X-Ray Fluorescence; IC: Ion Chromatography; ISE: Ion 

Selective Electrode

Figure A.1.X1.1. Sulfur expanded uncertainty (2001 – 2004) 

28
Chlorine Expanded Uncertainty 1999-2004

77

48

118

140

51

136

163

197

335

355

84 93

113 104

201

112

199

169

50

100

150

200

250

300

350

400

450

500

701-4 701-1 724-4 724-1 551-4 551-1 620-4 620-1 709-4 709-1 694-4 694-1 588-4 588-1 669-4 669-1 685-4 685-1

Com Com Com Com Gov Gov Gov Gov Gen Gen Prd Prd Com Com Gen Gen Gov Gov

USA USA USA USA CAN CAN AUS AUS USA USA USA USA USA USA GER GER USA USA

D 6721 D 6721 D 2361

Pot

D 2361

Pot

D 4208

IC

D 4208

IC

XRF XRF D 4208

ISE

D 4208

ISE

D 4208

ISE

D 6721 D 4208

ISE

D 4208

ISE

DIN DIN D 2361

IC

D 2361

IC

0

Uncertainty ug/g

USGS Blue Lab 685 

Geochemical Green Lab 588 

Canada Red Lab 551 

Australia Orange Lab 620 

Lab classification 

Com Commercial lab 

Edu University lab 

Gen Utility lab 

Gov Government lab 

Prd Coal producer 

Country code 

AUS Australia 

CAN Canada 

GER Germany (DIN) 

ISR Israel 

USA United States of America 

Analytical Instruments: ICPAES: Inductively Coupled Plasma Argon Emission Spectroscopy; 

ICPMS: Inductively Coupled Plasma Mass Spectroscopy; ICPOES: Inductively Coupled Plasma 

Optical Emission Spectroscopy; XRF: X-Ray Fluorescence; IC: Ion Chromatography; ISE: Ion 

Selective Electrode

Figure A.1.X1.2. Chlorine expanded uncertainty (2001 – 2004) 

29
Mercury Expanded Uncertainty 1999-2004

11

8

21 20

24 23

36

41

11 12

29

26 27

20 19

21

1111

0

10

20

30

40

50

60

709-4 709-1 672-4 672-1 620-4 620-1 685-4 685-1 694-4 694-1 724-4 724-1 667-4 667-1 588-4 588-1 675-4 675-1

Com Com Edu Edu Gov Gov Gov Gov Prd Prd Com Com Edu Edu Com Com Gen Gen

USA USA USA USA AUS AUS USA USA USA USA USA USA USA USA USA USA USA USA

D 6722 D 6722 D 6722 D 6722 D 6414 D 6414 D 6414 D 6414 D 6414 D 6414 D 3684 D 3684 D 6414 D 6414 D 3684 D 3684 InhouseInhouse

Uncertainty ng/g

USGS Blue Lab 685 

Geochemical Green Lab 588 

Canada Red Lab 551 

Australia Orange Lab 620 

Lab classification 

Com Commercial lab 

Edu University lab 

Gen Utility lab 

Gov Government lab 

Prd Coal producer 

Country code 

AUS Australia 

CAN Canada 

GER Germany 

ISR Israel 

USA United States of America 

Analytical Instruments: ICPAES: Inductively Coupled Plasma Argon Emission Spectroscopy; 

ICPMS: Inductively Coupled Plasma Mass Spectroscopy; ICPOES: Inductively Coupled Plasma 

Optical Emission Spectroscopy; XRF: X-Ray Fluorescence; IC: Ion Chromatography; ISE: Ion 

Selective Electrode

Figure A.1.X1.3. Mercury expanded uncertainty (2001 – 2004) 

30
Silica Expanded Uncertainty 1999-2004

0.97

0.54

1.10

0.87

1.54 1.55

3.36

2.85

0.96

1.41

1.63

1.50

1.07

1.49

0.88

1.37

0.86 0.92

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

669-4 669-1 712-4 712-1 724-4 724-1 551-4 551-1 588-4 588-1 620-4 620-1 673-4 673-1 655-4 655-1 685-4 685-1

Gen Gen Com Com Com Com Gov Gov Com Com Gov Gov Gen Gen Gen Gen Gov Gov

GER GER USA USA USA USA CAN CAN USA USA AUS AUS USA USA ISR ISR USA USA

DIN DIN D 4326 D 4326 D 6357 D 6357 D 4326 D 4326 ICPAES ICPAES ICPAES ICPAES D 3682 D 3682 ICPAES ICPAES ICPAES ICPAES

0

0

0

0

0

0

0

0

0

0

0

Uncertainty wt %

USGS Blue Lab 685 

Geochemical Green Lab 588 

Canada Red Lab 551 

Australia Orange Lab 620 

Lab classification 

Com Commercial lab 

Edu University lab 

Gen Utility lab 

Gov Government lab 

Prd Coal producer 

Country code 

AUS Australia 

CAN Canada 

GER Germany (DIN) 

ISR Israel 

USA United States of America 

Analytical Instruments: ICPAES: Inductively Coupled Plasma Argon Emission Spectroscopy; 

ICPMS: Inductively Coupled Plasma Mass Spectroscopy; ICPOES: Inductively Coupled Plasma 

Optical Emission Spectroscopy; XRF: X-Ray Fluorescence; IC: Ion Chromatography; ISE: Ion 

Selective Electrode

Figure A.1.X1.4. Silica expanded uncertainty (2001 – 2004) 

31
Vanadium Expanded Uncertainty 1999-2004

13 15

26 25

95

88

9

22

4 6

14

9

13

17 19 20

33 36

0

20

40

60

80

100

120

140

588-4 588-1 669-4 669-1 673-4 673-1 724-4 724-1 620-4 620-1 685-4 685-1 655-4 655-1 551-4 551-1 712-4 712-1

Com Com Gen Gen Gen Gen Com Com Gov Gov Gov Gov Gen Gen Gov Gov Com Com

USA USA GER GER USA USA USA USA AUS AUS USA USA ISR ISR CAN CAN USA USA

ICPAES ICPAES ICPOESICPOES D 3683 D 6357 D 6357 D 6357 ICPMS ICPMS ICPAES ICPAES ICPAES ICPAES XRF XRF ICPAES ICPAES

Uncertainty ug/g

USGS Blue Lab 685 

Geochemical Green Lab 588 

Canada Red Lab 551 

Australia Orange Lab 620 

Lab classification 

Com Commercial lab 

Edu University lab 

Gen Utility lab 

Gov Government lab 

Prd Coal producer 

Country code 

AUS Australia 

CAN Canada 

GER Germany 

ISR Israel 

USA United States of America 

Analytical Instruments: ICPAES: Inductively Coupled Plasma Argon Emission Spectroscopy; 

ICPMS: Inductively Coupled Plasma Mass Spectroscopy; ICPOES: Inductively Coupled Plasma 

Optical Emission Spectroscopy; XRF: X-Ray Fluorescence; IC: Ion Chromatography; ISE: Ion 

Selective Electrode

Figure A.1.X1.5. Vanadium expanded uncertainty (2001 – 2004) 

32
Appendix A.2

Phase 1: Preliminary Evaluation of Quality System and 

Recommendations, Final Report 

 

 

Performance Audit of U.S. Geological Survey Inorganic Geochemistry and 

Contract Laboratories 

Requisition #3-2920-1052 

 

 

 

 

 

September 10, 2004 

 

 

 

 

Louis Janke, President 

Quality Associates International®

, LDT. 

P.O. Box 117 

Douglas, ON K0J 1S0 

Canada 

33
Executive Summary 

Periodic external audits to verify that operations comply with the requirements of a QMS are a 

basic principle for sound laboratory management. The ultimate goal is to maintain a high level of 

confidence that the U.S. Geological Survey, Energy Resources Program, Inorganic Geochemical 

Laboratory (IGL) continues to produce data that are of the requisite accuracy. To that end, a 

performance audit of the IGL and its contract laboratory was conducted by Quality Associates 

International® Ltd. (QAI). This audit compared USGS results with laboratories representing 

government agencies, coal producers, utilities and third part testing laboratories worldwide each of 

which analyzes at least 2000 coal and coal derived samples a year. 

The recommendations in this report, which require only a modest investment in equipment and 

materials will improve analytical reliability, increase productivity, lower consumable costs 

(Appendix X2), and improve safety conditions. Specific recommendations are emphasized in the 

body of the report. 

The IGL facility is one of the two top included in this assessment for the determination of trace 

analytes in coal-derived ash. Through minor changes to in-house preparation procedures, this level 

of performance can be maintained and conducted in a more cost effective and safe manner while at 

the same time significantly improving performance for the determination of major and minor 

components in coal derived ash. 

The recommendations made in the preliminary audit for the IGL to expand the panel of Certified 

Reference Materials (CRMs) and Reference Materials (RMs) for sulfur and mercury analysis as 

well as to convert to ASTM D 6721 for chlorine analysis, including the purchase of a direct 

combustion instrument for chlorine are confirmed in this assessment. 

The USGS contract laboratory Geochemical Testing achieved the highest level of performance in 

this assessment for all contract parameters. 

A reassessment of the performance of the Denver laboratory shall be conducted by December 31 

2004 with a view to documenting the recommendations of the preliminary audit. This assessment 

should not only improve the overall efficiency of in-house capabilities, but also the reliability of 

analytical results. 

Introduction 

As part of a continuing effort to demonstrate government accountability the U.S. Geological 

Survey, Geologic Discipline, Energy Resources Team (ERT), is conducting an operating audit of 

the U.S. Geological Survey (USGS), Energy Resources Program, Inorganic Geochemistry 

Laboratory (IGL). Per ISO/IEC Guide 17025 General Requirements for the Competence of Testing 

and Calibration Laboratories, a basic tenet of sound laboratory management is a formal audit by 

an external examiner at appropriate intervals to verify that its operations comply with the 

requirements of the quality management system (QMS). 

34
In recognition of the need of the USGS to maintain a high degree of credibility both domestically 

and internationally, Quality Associates International® Ltd. (QAI) was contracted to conduct a 

performance-based audit that complies with the requirements of ISO Guide 17025. Properly 

structured, this approach permits an objective assessment of laboratory performance on a 

continuing basis as well as confirmation of any improvement in the reliability of analytical results. 

To ensure a comprehensive assessment of all analytical values reported by the U.S. Geological 

Survey (USGS), Inorganic Geochemistry Laboratory (IGL), the audit includes the IGL as well as 

the contract analytical laboratory, Geochemical Testing, Somerset PA. 

Approach 

ISO Guide 17025 General Requirements for the Competence of Testing and Calibration 

Laboratories, clause 5.4 accepts data from the analysis of Certified Reference Materials (CRMs), 

Reference Materials (RMs) and proficiency testing programs (PTP) as a basis for validating the 

capability of a laboratory to generate technically credible results. This performance based 

assessment approach for evaluating laboratory competence is continuing to gain prominence with 

regulatory (Environmental Protection Agency) as well as voluntary consensus standards writing 

organizations (SWOs) worldwide (ASTM International, ISO). The performance audit was 

conducted in two phases, preliminary recommendations and this final report. 

The preliminary audit of the IGL provided recommendations to increase both the reliability and 

efficiency of procedures related to the use of CRMs and RMs for performance based assessment. 

The next phase, addressed in this report, involves a detailed assessment of proficiency test data 

submitted to CANSPEXTM by the USGS and its contract laboratory covering 15 samples over the 

period of December 2000 to July 2004. CANSPEXTM is proficiency service designed and 

administered by QAI that promotes competency in the coal-testing laboratory. Most PTPs 

assimilate results from their participants and return nothing more than a statistical analysis of the 

data. In the testing environment of today this approach is no longer adequate. CANSPEXTM 

provides much more than just basic statistics by notifying the laboratory on factors that affect both 

short and long-term quality control. This is accomplished through publication of the CANSPEXTM 

Method Manual, which is updated on a yearly basis. The manual draws upon reports from 

participants as well as interlaboratory studies (ILS) that have been specifically designed to identify 

factors, which have a critical impact on the reliability of analytical results. ILS programs usually 

involve a minimum of 8 different laboratories and include samples that cover sample composition 

and physical characteristics that would normally be encountered in the laboratory. This approach 

guards against excessively sanitized data by subjecting a method to a variety of sample types, 

operators, equipment, and environmental conditions. Currently 95 laboratories from 18 countries 

take part in the CANSPEXTM program. 

The performance of the IGL and its contract laboratory is compared with laboratories representing 

government agencies, coal producers, utilities and third party testing laboratories worldwide, each 

of which analyzes at least 2,000 coal and coal derived samples a year. To provide an objective 

assessment of the CANSPEXTM PTP results, QAI employed the Horwitz function, which expresses 

an empirical relationship between sample concentration and multiple-laboratory standard deviation. 

This function, which applies over a wide range of test materials and analytes, as well as, physical 

principles underlying an analytical procedure, was developed from over 6,000 independent studies 

35
conducted worldwide. The Horwitz function is recognized by the International Union of Pure and 

Applied Chemists (IUPAC, Pure & Appl. Chem., Vol. 62, No.1, pp. 149-162, 1990) and employed 

by the International Association of Geoanalysts in their GeoPT proficiency testing scheme as a 

fundamental fitness for purpose performance benchmark. 

The Horwitz function can be employed to evaluate either the fitness for purpose of a method using 

interlaboratory study (ILS) data as prescribed by IUPAC or of a laboratory by examining 

proficiency test results over a series of samples. Dividing the standard deviation of a method ILS or 

of laboratory PTP results over a series of samples, by that predicted by the function, yields a 

Horwitz performance ratio. A low Horwitz performance ratio is an indicator of highly reliable 

analytical results. QAI recognizes several levels of performance. Class 1, which is appropriate for 

certified analysis, constitutes a performance ratio of 1 or less. Class 2, which is appropriate for 

referee (reference) analysis, constitutes a performance ratio of less than or equal to 2 but greater 

than 1. Class 3, which is appropriate for routine analysis, constitutes a performance ratio of less 

than or equal to 3 but greater than 2. Ratios greater than 3 indicate either that the laboratory or that 

the method employed by the laboratory is not capable of consistently producing suitable results. 

For this reason the evaluations in this document include the evaluation of the “best” current state of 

the art ASTM (reference) standard for a given measurement. 

Performance Tables 

This report includes a series of performance tables designed to provide the ability to determine the 

capability of a laboratory “at a glance”. The Horwitz PTP performance ratio for each laboratory as 

well as the Horwitz method ILS performance ratio for the best state of the art ASTM standard is 

listed. A blue performance ratio indicates the laboratory or method is capable of producing certified 

results (maximum relative analytical error of 1% at 100% concentration). A green performance 

ratio indicates the laboratory or method is capable of producing reference results (maximum 

relative analytical error of 2% at 100% concentration). An orange performance ratio indicates the 

laboratory or method is capable of producing routine results (maximum relative analytical error of 

3% at 100% concentration). 

ASTM Standards 

The objective of ASTM International is to produce standards that are suitable for routine analysis 

in the global coal testing community. ASTM conducts an ILS to establish the agreement of results 

can that expected within a laboratory (repeatability) and between laboratories (reproducibility). 

Both of these figures of merit appear in the precision statement of the respective ASTM standard 

and can be compared with the Horwitz function to determine the performance ratio of the standard.

Laboratory Performance 

The goal of a laboratory should be to achieve a performance ratio at least equivalent to the

reference standard. It is possible for a laboratory to achieve a lower performance ratio than the 

reference standard by establishing more rigorous control over environmental, sample preparation 

and instrumental conditions than specified in the standard. The following discussion provides 

examples of how an improved performance ratio (lower ratio) can be attained. 

36
The ASTM method for the determination of sulfur in coal D 4239 requires the measurement device 

to be calibrated with certified reference material (CRM) coals. Because the standard is employed 

worldwide for the determination of sulfur in coal, no restriction is placed on the source or 

composition of the CRMs. Prior to use for calibration, the certified values of the sulfur in the CRM 

coals, which is expressed on a dry basis, must be converted to the as determined basis by 

determining the moisture content of the CRM coal. The standard specifies, “CRM’s must be stable 

with respect to moisture”. Some laboratories control the relative humidity of the laboratory 

environment to remain in the range of 45 % to % 55 year round. Others do not control this 

environmental factor. In this case the relative humidity can range from as low as 25 % in the winter 

months to as much as 80 % in the summer months. The moisture content of CRM samples tracks 

the relative humidity of the laboratory environment. In the case where the humidity is controlled as 

described above, there will be negligible change in the as determined values of the CRM samples. 

In the case where humidity is not controlled, the change in relative humidity can create significant 

and undetected calibration shifts that adversely affect the reliability of results. As a result, a 

laboratory that controls relative humidity can be expected to achieve a lower (better) performance 

ratio for sulfur than one that does not. 

ASTM D 4239 specifies “the CRM’s must be must be mixed thoroughly before each use”, but does 

not explicitly state the same requirement for test samples. The amount of coal sample normally 

employed for the determination of sulfur in coal is 150 mg to 200 mg. Since coal is by its very 

nature a heterogeneous material that tends to segregate on sitting, to ensure a representative and 

homogeneous test portion is taken for analysis mixing is a critical step in the preparation not only 

of calibration but also of test samples. Laboratories that have a uniform procedure for mixing all 

samples prior to taking a test portion for analysis can be expected to achieve a better performance 

ratio than those that do not. In fact, performance can be further improved by mixing all calibration 

samples after a test portion has been extracted for analysis to ensure the coal remaining equilibrates 

with the atmosphere in the bottle. 

ASTM D 4239 states “follow the calibration procedure recommended by the manufacturer”. 

Instruments that comply with ASTM D 4239 produce a peak that resembles a bell shape. This peak 

has two fundamental properties, height and area. Instrument manufacturers provide the option of 

calibrating by peak height or peak area. In the majority of cases, instrument peak height can, and 

does vary more from measurement to measurement than does instrument peak area. This is because 

as peak height increases the peak base decreases and as peak height decreases the peak base 

increases. As a result, peak area tends to remain more stable. The time required to measure 

maximum peak height is less than that required to measure total peak area. Many laboratories 

calibrate and measure according to peak height to increase sample throughput. However, 

laboratories that set the instrument condition to accumulate peak area can be expected to achieve a 

better performance ratio. 

The USGS IGL is laboratory 135 and the USGS contract laboratory Geochemical Testing is 

laboratory 38 in the following tables and discussion. 

Trace Analysis in Coal Derived Ash

37
A comparison of the trace element results from the IGL (135) and 7 other laboratories is presented 

in table A.2.1. 

Table A.2.1. Trace element performance summary table 

Laboratory ASTM D 6357 135 300 70 105 119 123 146 174

Country International USA USA AUS ISR GER USA CHN USA

Class Reference Gov Com Gov Gen Gen Gen Gov Com

Arsenic 2.6 1.9 2.6 1.8 2.8 2.8 2.7 2.2 1.8 

Beryllium 2.0 2.2 2.6 1.1 1.9 2.5 2.1 1.8 

Cadmium 2.4 1.8 9.7 4.1 4.6 4.1 2.4 9.7 1.7 

Cobalt 2.0 2.2 5.2 7.2 4.1 4.8 2.4 4.1 4.9 

Chromium 2.1 2.0 0.9 3.9 2.2 1.6 1.8 6.3 2.2 

Copper 2.5 2.1 1.5 4.7 1.9 1.3 2.3 1.4 2.1 

Manganese 2.3 1.4 1.3 0.9 3.5 1.5 5.2 1.8 1.4 

Nickel 2.3 1.6 1.9 3.0 2.5 4.8 2.5 2.9 2.1 

Lead 2.8 3.6 10.2 3.6 3.9 5.8 2.4 5.0 3.7 

Antimony 3.1 2.1 3.7 7.6 10.5 14.8 2.0 

Vanadium 2.7 2.7 0.7 1.5 2.8 1.2 2.9 2.7 1.9 

Zinc 2.2 15.8 18.0 1.5 2.3 1.7 3.1 2.3 1.0 

Australia (AUS), China (CHN), Germany (GER), Israel (ISR), United States of America (USA) 

Commercial Laboratory (Com), Utility (Gen), Government (Gov), Producer (Prd) 

Green: Certified; Orange: Reference; Blue: Routine; Black: >3% analytical error; 

BLANK: Not analyzed. 

ASTM Standard 

In the case of trace element analysis ASTM has met the goal of producing a standard (ASTM D 

6357) that is suitable for routine analysis. Most experts would recognize that the single exception 

antimony, which approaches the routine benchmark, presents substantial challenges to the analyst 

in a matrix as complex as coal ash. 

Inorganic Geochemistry Laboratory Trace Analysis 

The two laboratories that achieve the highest level of performance overall for trace element 

parameters with respect to the reference standard are laboratory 174 and laboratory 135, the IGL 

(table A.2.1). This can easily be discerned from the table as these two laboratories have more trace 

parameters that qualify as certified, reference and routine than do the other labs. The numerical 

procedure involves discarding the best and worst scores (something like Olympic gymnastics) and 

adding the remaining scores. When this is done Laboratories 135 and 174 achieve the best scores. 

In fact, if the two best and two worst scores are discarded laboratories 135 and 174 still 

achieve the best performance overall. Both laboratories employ acid digest procedures. The 

difference between the two procedures is that the laboratory 174 digest, based on ASTM D 6357, 

uses nitric, hydrochloric, hydrofluoric acids, and a hot block, while the IGL procedure resorts to 

38
nitric, hydrochloric, sulfuric, perchloric acids and a Teflon digestion vessel. Use of perchloric acid 

can pose additional safety hazards. It is an analytical fact that each step or chemical employed in a 

test increases the overall variability of the results obtained. 

Recommendation 1: Equivalency Test for Sample Digestion Procedures

Taking into account the above observations along with the difficulties of maintaining and designing 

a system for the safe use of perchloric acid, the IGL should conduct an equivalency test employing 

the 6357 acid mix with a hot block digest. The test would be performed by conducting duplicate 

analysis of CANSPEXTM ash samples 2000-4 to 2004-2 on two separate days. 

A notable exception to the performance of laboratory 135 is zinc. The performance for zinc is so 

out of line with the other parameters that ambient contamination is suspected. This can be 

confirmed by running samples on the both the ICP-AES and ICP-MS. If both instruments produce 

erratic results, contamination is the most likely cause. 

Major and Minor Analysis in Coal derived Ash

A comparison of the major and minor element results from the IGL (135) and 7 other laboratories 

is presented in table A.2.2. 

Table A.2.2. Major and minor element performance summary table. 

Laboratory ASTM D 4326 135 300 1 70 105 119 144 174

Country International USA USA CAN AUS ISR GER USA USA

Class Reference Gov Com Gov Gov Gen Gen Prd Com

Na2O 2.7 3.2 24.8 3.8 1.8 1.5 2.0 1.9 2.7 

MgO 3.4 2.0 1.9 2.0 1.3 1.5 1.0 0.8 1.1 

Al2O3 3.4 2.8 2.6 2.2 1.2 1.5 0.9 1.6 1.6 

SiO2 2.9 3.6 1.7 1.6 1.3 1.2 0.8 0.9 1.2 

P2O5 2.7 5.7 4.1 2.6 3.9 7.0 3.8 1.9 4.3 

SO3 8.3 8.7 11.3 14.2 11.6 4.9 5.6 6.0 5.1 

K2O 2.7 5.2 2.4 1.9 2.2 3.0 2.5 2.4 1.2 

CaO 2.3 2.4 3.2 6.4 1.2 1.4 1.2 1.1 1.4 

TiO2 2.6 1.8 1.3 1.6 1.0 1.6 1.2 1.7 1.0 

Fe2O3 2.2 4.8 2.1 1.5 1.5 1.0 0.8 1.4 1.0 

Australia (AUS), Canada (CAN), Germany (GER), Israel (ISR), United States of America (USA) 

Commercial Laboratory (Com), Utility (Gen), Government (Gov), Producer (Prd) 

Green: Certified; Orange: Reference; Blue: Routine; Black: >3% analytical error. 

ASTM Standard 

In the case of major and minor analysis ASTM has met or approaches the goal of producing a 

standard (ASTM D 4326) that is suitable for routine analysis. ASTM D 4326 employs a fluxing 

39
agent to fuse the sample followed by an X-Ray Fluorescence (XRF) finish. The most notable 

exception to an acceptable performance rating of 3 or less for D 4326 is SO3. This rating actually 

reflects the impact of the fusion preparation technique on the recovery of sulfur. A certain amount 

of SO3 is always lost in the fusion step. Because different laboratories use different fluxing agents 

and sample weights, the amount of SO3 lost varies significantly from laboratory to laboratory 

resulting in the poor performance ratio. This variable loss of SO3 does not affect the other analytes 

as loss on fusion is taken into account in the X-Ray corrections. 

Examining the performance ratios of D 4326 for the remaining major and minor analytes suggests a 

trend to better performance with increasing atomic number as would be expected for XRF. 

It is also notable that Laboratory 1, which employs XRF, does not perform as well as laboratories 

70, 105, 119, 144 and 174, all of which use an ICP finish. ICP would be expected to perform better 

than XRF for low atomic number analytes. It is also interesting that laboratories employing ICP, 

which can be notorious for producing variable K2O, do not perform as well as laboratory 1 for 

K2O. 

Essentially, the major and minor element results from table A.2.2 shows the various finish 

techniques perform exactly the way they would be expected to perform with respect to their 

underlying physical and chemical principles. 

Inorganic Geochemistry Laboratory Major and Minor Analysis 

Excluding sulfur for the reasons stated above and Na2O, which is determined from another 

preparation step, the IGL (135) does not meet the performance goal for 5 of the eight remaining 

major and minor elements in coal derived ash. This trend was initially identified for SiO2 weight 

percent in the preliminary audit (Appendix A.1). 

The laboratories achieving the highest level of performance are 144, 119, 174 and 70. All of these 

laboratories use an ICP finish similar to that employed by the USGS. Of these four labs, laboratory 

144 and laboratory 174 use the nitric, hydrochloric and hydrofluoric acid mix described in ASTM 

D 6357 followed by a hot block digestion. 

Using the same acid hot block digestion procedure Laboratory 174 achieved the highest level of 

performance for trace element analysis along with the IGL 135, which also employs an acid digest 

for trace elements. 

 

This supports the observation in the preliminary audit that the IGL sinter preparation procedure 

produces inconsistent recovery of certain major and minor constituents from coal derived ash, most 

likely due to the very low temperature (450 oC) at which the sinter is conducted. 

 

Recommendation 2: Modification of Sample Digestion Procedure 

The IGL should convert to the acid mix prescribed in ASTM D 6357, followed by hot block 

digestion for dissolution of coal-derived ash. This would create a single digestion procedure 

adequate for major, minor and trace elements significantly reducing operator time and consumables 

while, at the same time, improving the safety of the preparation step. During commissioning of this 

40
method, the IGL should conduct duplicate analysis of CANSPEXTM ash samples 2000-4 to 2004-2 

on two separate days. These results can be used to reevaluate the performance of the IGL for major 

and minor element analysis. 

 

Coal Analysis 

A comparison of the major and minor element results from the IGL (135), Geochemical Testing 

(38), and 7 other laboratories is presented in table A.2.3. 

 

Table A.2.3. Coal analysis performance ratios. 

Laboratory ASTM 135 38 1 70 117 119 122 144 146 151 159 174 176

Country International USA USA CAN AUS USA GER USA USA CHN USA USA USA NLD

Class Reference Gov Com Gov Gov Edu Gen Edu Prd Gov Com Gen Com Com

Ash 1.1 0.6 0.4 0.4 0.3 0.8 0.8 0.5 0.5

Volatile 1.5 0.7 0.9 0.6 1.5 1.0 9.1 1.3 1.9

Btu/lb 2.2 0.9 1.6 1.6 2.5 1.7 3.2 1.2 2.4

Carbon 1.3 0.5 0.4 0.4 0.6 0.5 1.4 1.1 1.0

Hydrogen 2.8 1.1 1.1 0.7 1.5 1.4 2.4 2.1 1.6

Nitrogen 3.6 1.8 1.4 1.2 4.1 1.8 4.6 2.5 1.3

Sulfur 2.3 1.9 1.6 0.8 1.1 1.0 2.1 2.2 1.1 2.2

Chlorine 1.3 22.6 8.2 4.8 1.9 3.7 6.2 1.9 1.9

Mercury 0.7 1.8 1.7 0.9 1.3 0.9 1.5 0.6 1.8

Australia (AUS), Canada (CAN), Germany (GER), Israel (ISR), United States of America (USA) 

Commercial Laboratory (Com), Utility (Gen), Government (Gov), Producer (Prd), University 

Research (Edu) 

Green: Certified; Orange: Reference; Blue: Routine; Black: >3% analytical error; 

BLANK: Not analyzed. 

ASTM Standards

With the exception of nitrogen, it is evident the ASTM reference standards meet the requirement of 

being suitable for routine analysis. A cooperative study between ASTM and ISO is to be 

undertaken in 2005 to further improve the reliability of methods for carbon, hydrogen, and nitrogen 

analysis. 

Inorganic Geochemistry Laboratory Coal Analysis 

Sulfur in Coal

The IGL (135) achieved a reference quality level of performance for sulfur well within the 

performance rating of the ASTM reference standard. The Canadian lab, which achieved by far the 

highest level of performance for sulfur employs certified reference materials (CRMs) and reference 

materials (RMs) from at least two independent sources for calibration of the sulfur analyzer. This 

laboratory also exercises all of the precautions cited in the section on Laboratory Performance that 

41
describes how to control environmental, sample preparation, and instrument conditions to achieve a 

low performance ratio for sulfur. A recommendation to further improve the reliability of sulfur 

analysis through the use of calibrants from independent sources was made to the USGS in the 

preliminary audit report (Appendix A.1). This recommendation, which has been implemented, 

should result in the IGL approaching or performing at the certified level. 

Chlorine in Coal

Studies conducted by The Electric Power Institute (EPRI) and the International Organization for 

Standardization (ISO) have demonstrated the Eschka ignition method employed by the IGL for 

preparation of coal samples for chlorine analysis yields highly erratic and inconsistent recovery. 

This is reflected in the extremely high performance ratio of 22.6 (table A.2.3). 

ASTM D 6721 is the benchmark method for chlorine. ASTM D 6721, published for use in late 

2001, consistently produces chlorine results of reference quality. Standards that predate D 6721 (D 

2361 and D 4208) are not capable of producing results of even routine quality. The performance 

table A.2.3 covers a period during which laboratories were constrained to use standards similar to 

D 2361 and D 4208. Laboratories 1, 38 and 144 employ ASTM D 4208. Laboratories 151 and 

laboratory 174 have converted to, or are employing methods similar to D 6721. Both of these 

laboratories are approaching the desired performance goal. The Australian laboratory 70 employs 

XRF. 

Recommendation 3: Conversion to ASTM D 6721 for Chlorine Analysis 

The preliminary audit (Appendix A.1) recommended that IGL convert to ASTM D 6721. During 

commissioning of this method, the IGL should conduct duplicate analysis of CANSPEXTM coal 

samples 2000-4 to 2004-2 on two separate days. These results can be used to reevaluate the 

performance of the IGL for chlorine analysis. 

Mercury in Coal:

The IGL consistently produces reference quality mercury results. Laboratory 122 and laboratory 

159, which employ the ASTM reference method for mercury, D 6722 produce certified quality 

data, which meets or approaches that of the ASTM reference standard. The preliminary IGL audit 

(Appendix A.1) and this more extensive assessment are based on IGL results from a procedure 

based on wet oxidation of the test sample that complies with ASTM D 6414. Laboratories 117 and 

144 employ an acid extraction method that complies with ASTM D 6414. The Australian 

laboratory 70 employs a variation of method D 6414 that promotes uniform and continuous 

refluxing of the sample to ensure complete extraction of mercury. The IGL has recently purchased 

a digestion apparatus that promotes uniform continuous acid reflux of the test sample. The 

purchase of this digestion apparatus along with implementation of recommendations with respect to 

selection and use of CRM coals should allow the IGL to produce certified quality results similar to 

the reference ASTM standard. 

Recommendation 4: Conversion to the acid extraction procedure per ASTM D 6414 for 

Mercury Analysis

42
The IGL should convert to the acid extraction procedure described in ASTM D 6414 employing a 

hot block digestion for mercury analysis. 

Contract Coal Analysis: USGS Contract Laboratory Performance

The contract laboratory (38) performs ash, volatile matter, Btu/lb, carbon, hydrogen, nitrogen, and 

sulfur analysis for the USGS (table A.2.3). 

Recommendation 5: The USGS Contract Laboratory Achieved the Highest Level of 

Performance for the Contract Parameters 

 

Table A.2.3 shows the USGS contract laboratory (38) easily meets the performance goal for all 

contract parameters. In fact, laboratory 38 achieved the highest level of performance for the 

contract parameters overall along with laboratory 1 from Canada and Laboratory 119 from 

Germany. The USGS should continue to monitor all contract laboratory analyses. 

APPENDIX A.2.X1: Cost Analysis Summary 

Recommendations 

The recommendations provided in this report require a total capital investment of approximately 

$30,000. In addition to significantly increasing the reliability of results, it is anticipated the USGS 

will recover the capital investment within 1 year and will realize an increased man-hour and 

consumable margin equivalent to $100,000 over a period of 4 years, as well as achieving a safer 

operating environment. This was revised upward from the original total estimate of $85,720 in 

table A.1.2 after final capital costs were finalized. 

These estimates are summarized in the table A.2.X1.1. 

Table A.2.X1.1. Estimated cost savings over a four year period for all recommendations. 

Recommendation Description Year 1 Year 2 Year 3 Year 4 Totals 

3,4 CRM/RM $1,185 $645 $645 $645 $3,120 

3 Analyzer (per ASTM D6721) ($11,850) $13,150 $13,150 $13,150 $27,600 

1, 2 Hot Block $15,250 $18,250 $18,250 $18,250 $70,000 

Net Savings $4,585 $32,045 $32,045 $32,045 $100,720 

CRM: Certified Reference Material. 

RM: Reference Material. 

Negative values in parentheses. 

Note: Year 1 for recommendations 1 and 2, and 3 include the purchase of an analyzer (per 

ASTM D6721) for chlorine and Hot Block for $25,000 and $3,000 respectively. 

43
Appendix B 

 

Phase 3: Reassessment Analyses, and On-site Audit Final Report 

Appendix B.1: Evaluation of Reassessment Results from Chlorine 

Determinations, March 19, 2005 

 

Appendix B.2: Evaluation of Reassessment Results of IGL Digestion Procedures 

for Major Oxides, April 04, 2005 

 

 

Appendix B.3: On-Site Evaluation of USGS IGL September 12- 14, 2005: October 

10, 2005 

 

Appendix B.4: References for Cited Standards and Organizations 

The following appendices do not conform to USGS form and style. They also contain multiple reference 

citations to standard methods and other contacts. To facilitate review of the documents the reference 

was not provided every time a standard test method or organizational contacts were cited. Information 

regarding these citations is provided Appendix B.4. 

44
Appendix B.1 

Phase 3: Evaluation of Reassessment Results from Chlorine 

Determinations 

 

 

 

 

Performance Audit of U.S. Geological Survey Inorganic Geochemistry and 

Contract Laboratories 

 

Requisition #3-2920-1052 

 

 

 

 

 

March 19, 2005 

 

 

 

 

 

Louis Janke, President 

Quality Associates International®

, LDT. 

P.O. Box 117 

Douglas, ON K0J 1S0 

Canada 

45
Quality Associates International (QAI) Findings: (Lou Janke) 

The U.S. Geological Survey (USGS), Inorganic Geochemistry Laboratory (IGL produced chlorine 

(Cl) results employing ASTM D 6721 for 20 samples distributed through CANSPEXTM from 2000 

to 2004 that exhibit a marked improvement in accuracy without any degradation in precision 

particularly, for samples with less than 500 μg/g Cl. The CANSPEXTM samples cover a wide range 

of coal rank and grade and represent coals from 9 different countries. No other CANSPEXTM 

laboratory achieved as high a level of performance for these 20 CANSPEXTM samples. The results 

of this assessment are summarized in tables B.1.1 and B.1.2. 

USGS Inorganic Geochemistry Laboratory (IGL) Findings: (John Bullock) 

To obtain an initial Cl estimate use a 10 mg test portion of coal. 

Employ 100 mg of tungsten promoter for low weight, high Cl samples and 200 mg tungsten 

promoter for high weight low Cl samples. Intimate mixing of the promoter with the coal is 

recommended. 

The method blank is carried out on 200 mg of tungsten. The blank can be adjusted for lower 

weights of tungsten based on the 200 mg blank. 

For low Cl samples, take care in mixing the tungsten promoter with the coal sample as loss of 

material can occur. If this occurs, then the sample must be reweighed. 

The current instrument plumbing results in the buildup of latent moisture, which appears to 

generate a residual signal that adds as much as 5 minutes to the total analysis time. The IGL is 

reconfiguring instrument plumbing to minimize this problem. The same 20 CANSPEXTM samples 

shall be rerun with the new configuration to confirm that the accuracy and precision are not 

adversely affected. 

Data evaluation: 

Duplicate results were reported by the IGL for the 20 samples (Table B.1.1). 

The precision and accuracy of the IGL results were evaluated using the CANSPEXTM most likely 

value standard deviation (MLV 1S) derived from all Cl results reported to CANSPEXTM. The MLV 

1S takes into account sample inhomogeneity as well as the diverse methods and control materials 

employed by CANSPEXTM laboratories for the determination of chlorine. 

A result that agrees with the CANSPEXTM value within the MLV 1S is green and is considered to 

be certified quality. A result that agrees with the CANSPEXTM value within 2 times the MLV 1S is 

blue and is considered to be reference quality. A result that agrees with the CANSPEXTM value 

within 3 times the MLV 1S is orange and is considered to be routine quality. A value greater than 3 

times the MLV 1S estimate is red and is considered suspect. 

46
Similarly, precision that is less than or equal to the CANSPEXTM MLV 1S is green and is 

considered to be certified quality. Precision that is less than or equal to 2 times the CANSPEXTM 

MLV is blue and is considered to be reference quality. Precision that is less than or equal to 3 

``times the CANSPEXTM MLV 1S is orange and is considered to be routine quality. Precision 

greater than 3 times the MLV 1S is red and is considered suspect. 

Table B.1.1. USGS IGL raw chlorine data. 

CANSPEXTM

CANSPEX

Ash Value 

 CANSPEX

S Value 

 CANSPEX 

Cl Value MLV 1S

USGS 

D6721 

Accuracy

USGS D 

6721 

Precision 

USGS 

Eschka/IC 

Accuracy

USGS 

Eschka/IC 

Precision

2004-4 Australia mvb 13.50 0.31 100 20 86 4 

2004-3 Indonesia hvCb 7.34 0.37 37 12 17 1 

2004-2 Australia hvAb 10.71 0.52 213 21 230 2 295 17 

2004-1 ISGS hvBb 9.54 4.31 135 17 116 4 

2003-4 Venezuela hvAb 5.44 0.67 214 24 200 4 341 14 

2003-3 USA hvAb 8.51 0.92 1483 53 1568 40 1480 28 

2003-2 Canada subA 24.32 0.25 67 22 12 1 

2003-1 Canada ligA 21.17 0.92 92 30 16 1 292 13 

2002-4 NIST 2693 mvb 9.43 0.46 384 30 373 5 898 17 

2002-3 UK hvAb 19.18 1.90 4854 156 5444 80 4662 263 

2002-2 UK hvAb 18.38 2.67 2317 71 2357 34 2321 205 

2002-1 USGS mvb 6.28 1.54 1093 68 1045 30 1255 82 

2001-4 USA hvAb 8.10 0.74 1900 114 1928 8 1838 64 

2001-3 USA hvAb 9.66 0.77 2000 79 2054 6 2132 38 

2001-2 USA hvAb 8.28 1.30 1963 78 2044 4 2090 5 

2001-1 Spain hvCb 6.82 3.58 66 16 22 1 <150 

2000-4 Germany mvb 7.00 0.70 1172 59 1117 8 1126 9 

2000-3 China an 13.04 0.12 569 33 568 9 

2000-2 NIST 2692b hvAb 7.89 1.17 1601 80 1575 33 

2000-1 ISGS IBC 105 17.96 4.27 877 39 811 23 

Green: Less than or equal to the CANSPEXTM MLV 1S 

Blue: Less than or equal to 2 times the CANSPEXTM MLV 1S

Orange: Less than or equal to 3 times the CANSPEXTM MLV 1S 

Red: Precision greater than 3 times the MLV 1S 

BLANK: Not analyzed 

The IGL precision for all 20 samples is green and can be considered of certified quality. Of the 20 

samples reported by the IGL, 11 exhibit certified accuracy(green), 5 reference accuracy (orange), 3 

routine accuracy (blue) and 1 sample 2002-3 is suspect (red). No other CANSPEXTM laboratory 

achieved this high a level of performance for these 20 CANSPEXTM samples. The results submitted 

by the IGL using the former Eschka ignition Ion Chromatography (IC) finish are provided for 

comparison purposes. 

The ash and sulfur content of each CANSPEXTM sample is listed. These two characteristics are 

known to have a critical impact on the precision and accuracy of chlorine results from other 

47
commonly employed methods including XRF, bomb decomposition with an ISE, or IC finish, and 

Eschka ignition with an ISE, or IC finish. There does not appear to be any relationship between 

these parameters and the determination of chlorine by D 6721. 

Method D 6721 is calibrated and controlled employing an aromatic organochlorine compound. 

Many laboratories reporting Cl results to CANSPEXTM employ a variety of certified reference 

material (CRM) coals from different certifying agencies for calibration and control. Different 

calibration and control materials can introduce a bias into laboratory results. 

Most likely value estimation was applied to the raw chlorine data submitted by the IGL to estimate 

and apply a correction for calibration and control bias. This correction has no effect on laboratory 

precision. The results are summarized in table B.1.2. 

Table B.1.2. USGS IGL Chlorine results corrected for calibration and control bias. 

CANSPEXTM

CANSPEX 

Ash Value 

CANSPEX 

S Value 

CANSPEX 

Cl Value 

MLV 

1S 

USGS D 

6721 

Accuracy

USGS D 

6721 

Precision 

USGS 

Eschka/IC 

Accuracy 

USGS 

Eschka/IC 

Precision

2004-4 Australia mvb 13.50 0.31 100 20 99 4 

2004-3 Indonesia hvCb 7.34 0.37 37 12 25 1 

2004-2 Australia hvAb 10.71 0.52 213 21 244 2 295 17 

2004-1 ISGS hvBb 9.54 4.31 135 17 128 4 

2003-4 Venezuela hvAb 5.44 0.67 214 24 216 4 341 14 

2003-3 USA hvAb 8.51 0.92 1483 53 1603 40 1480 28 

2003-2 Canada subA 24.32 0.25 67 22 26 1 

2003-1 Canada ligA 21.17 0.92 92 30 36 1 292 13 

2002-4 NIST 2693 mvb 9.43 0.46 384 30 393 5 898 17 

2002-3 UK hvAb 19.18 1.90 4854 156 5547 80 4662 263 

2002-2 UK hvAb 18.38 2.67 2317 71 2404 34 2321 205 

2002-1 USGS mvb 6.28 1.54 1093 68 1091 30 1255 82 

2001-4 USA hvAb 8.10 0.74 1900 114 2003 8 1838 64 

2001-3 USA hvAb 9.66 0.77 2000 79 2106 6 2132 38 

2001-2 USA hvAb 8.28 1.30 1963 78 2095 4 2090 5 

2001-1 Spain hvCb 6.82 3.58 66 16 33 1 <150 

2000-4 Germany mvb 7.00 0.70 1172 59 1156 8 1126 9 

2000-3 China an 13.04 0.12 569 33 590 9 

2000-2 NIST 2692b hvAb 7.89 1.17 1601 80 1628 33 

2000-1 ISGS IBC 105 17.96 4.27 877 39 837 23 

Green: Less than or equal to the CANSPEXTM MLV 1S 

Blue: Less than or equal to 2 times the CANSPEXTM MLV 1S

Orange: Less than or equal to 3 times the CANSPEXTM MLV 1S 

Red: Precision greater than 3 times the MLV 1S 

BLANK: Not analyzed 

Of the 20 samples reported by the IGL 9, exhibit certified accuracy (green), 8 reference accuracy 

(blue), 2 routine accuracy (orange) and 1 sample (2002-3) remains suspect (red). 

48
At first glance there does not appear to be a significant change in the performance of the IGL with 

respect to accuracy. However, closer examination reveals that there is better agreement of the IGL 

value for samples with less than 500 μg/g chlorine. This suggests a discrepancy between D 6721 

calibrated and controlled with the organochlorine compound and other methods calibrated and 

controlled with CRM coals. It is notable that the majority of CRM coals employed to calibrate and 

control chlorine measurements are in the order of 1,000 μg/g – 2,000 μg/g chlorine (Cl). 

49
Appendix B.2

Phase 3: Evaluation of Reassessment Results of USGS Digestion 

Procedures for Major Oxides 

 

 

 

 

Performance Audit of U.S. Geological Survey Inorganic Geochemistry and 

Contract Laboratories 

 

Requisition #3-2920-1052 

 

 

 

 

 

April 04, 2005 

 

 

 

 

 

Louis Janke, President 

Quality Associates International®

, LDT. 

P.O. Box 117 

Douglas, ON K0J 1S0 

Canada 

50
Introduction 

Evaluation of CANSPEXTM data resulted in a recommendation that the U.S. Geological Survey 

(USGS), Inorganic Geochemistry Laboratory (IGL convert from a sinter-acid digestion procedure 

for decomposition and dissolution of coal derived ash to the mixed-acid decomposition and 

dissolution recommended in ASTM D 6349 with modifications recommended by CONSOL 

Research and Development during the development of ASTM D 6349. 

The IGL performed the mixed-acid digestion on four separate test portions of 21 CANSPEXTM 

samples covering the period of 1999 to 2004. 

Evaluation of major oxide results from the mixed-acid digestion suggests significant solution-tosolution instability in the inductively coupled plasma (ICP) emission intensities is affecting the 

precision and accuracy of the major oxide results. The evaluation is summarized in this report. 

Summary of Approach 

Of the 21 samples subjected to the recommended mixed-acid digestion procedure, 18 are samples 

prepared by Quality Associates International® Ltd. (QAI). The remaining 3 are certified reference 

materials (CRMs) from three independent certifying bodies, the Canadian Certified Reference 

Materials Program (CCRMP), the National Institute of Standards and Technology (NIST) USA, 

and the USGS. These CRMs are employed world wide for the calibration and control of procedures 

employed for the determination of major oxides. The homogeneity of all three CRMs has been 

verified by the respective certifying agencies. To eliminate any objections concerning the 

homogeneity of the QAI samples, this evaluation is limited to results from the 3 CRMs. 

Data Evaluation 

This evaluation compares the results from the sinter-acid digestion procedure employed to produce 

the original CANSPEXTM results with results from the mixed-acid digestion procedure. The 

original CANSPEXTM samples were not ignited by the IGL prior to digestion. The samples 

subjected to mixed-acid digestion were subjected to a uniform ignition procedure by the IGL prior 

to digestion. 

Values provided on the certificates issued by the respective certifying bodies were employed to 

calculate expected major oxide totals for the unignited and ignited CRM samples. These totals are 

summarized in Table B.2.1. 

Table B.2.1. Expected major oxide totals (weight percent) for the unignited and ignited CRM 

samples.

Source Sample Expected Unignited 

Total 

Expected Ignited 

Total 

CCRMP SY-4 94.75 99.27 

NIST 1633b 96.39 99.79 

USGS GSP-2 98.75 98.75 

51
 

The IGL confirmed all samples subjected to the mixed-acid digestion did not contain any visible 

residue. This suggests the entire sample is taken into solution by the mixed-acid digestion 

procedure. The IGL ran the 4 separate test portions of the each sample employing the following 

protocol. 

Day 1 

Sample 1 Portion 1, .....Sample 21, Portion 1. 

Sample 1 Portion 2,......Sample 21, Portion 2. 

Day 2 

Sample 1 Portion 1, Sample 1 Portion 2, .....Sample 21, Portion 1, Sample 21, Portion 2. 

The major oxide total was calculated for each sample test portion. These totals are summarized for 

the three CRMs in Table B.2.2 below. 

Table B.2.2. The major oxide totals (weight percent basis). 

Source CRM Digestion 

Method Ignited Total 1 Total 2 Total 3 Total 4 Expected 

Total 

CCRMP SY-4 MixedAcid Yes 100.75 101.66 96.72 92.10 99.27 

CCMRP SY-4 SinterAcid No 102.02 100.16 104.04 100.70 94.75 

NIST 1633b MixedAcid Yes 99.45 113.37 102.38 93.22 99.79 

NIST 1633b SinterAcid No 93.75 96.52 97.29 86.13 96.39 

USGS GSP-2 MixedAcid Yes 99.87 102.29 100.37 97.90 98.75 

USGS GSP-2 SinterAcid Yes 104.59 103.03 95.34 103.86 98.75 

The notable feature of this summary is that several totals in the table significantly exceed the 

expected total. This suggests sample-to-sample instrument drift in the measuring device (ICP) 

employed to determine the oxide values. 

To assess whether instrument drift has an impact on the reliability of results, a correction was 

applied to each reported oxide value. The correction is applied as follows. 

Corrected Oxide Value = (Reported Oxide Value) x [(Total)/(Expected Total)] 

52
If instrument drift is a contributing factor, the corrected oxide values should exhibit significantly 

improved precision (reduced spread in the test portion results) and acceptable accuracy (agreement 

with the certified value) for each test portion result. 

The comparisons of reported and corrected oxide values (SiO2, Al2O3, Fe2O3, CaO, MgO, Na2O,

K2O and TiO2) for the 3 CRMs are presented in figs. B.2.1-8. the x-axis of the graph specifies the 

oxide, the digestion method Acid (mixed-acid) or Sinter (sinter-acid). The results displayed are Rep 

(reported oxide value) or Corr (corrected oxide value), the CRM source and designation, and the 

year sequence the CRM was originally distributed through CANSPEXTM. A green circle on the 

graph with a value listed in green to the left represents the certified oxide value. Vertical green bars 

accompany each green circle. These green bars are the acceptable accuracy limits that should been 

obtained under in-control routine analysis conditions. The horizontal blue bars are the day 1 (test 

portion 1 and test portion 2) results. The horizontal orange bars are the day 2 (test portion 3 and test 

portion 4) results. 

Observations: 

The conclusions below are based on the combined assessment of all of the graphs in figs. B.2.1-8. 

Table B.2.3 below summarizes whether the correction procedure described above yields improved 

precision and acceptable accuracy for the three CRM samples. 

Table B.2.3. Comparison of precision and accuracy of corrected oxide vs. reported oxide values. 

Parameter Mixed-Acid Sinter-Acid Acid-Old 

Improved 

Precision 

Acceptable 

Accuracy 

Improved 

Precision 

Acceptable 

Accuracy 

Improved 

Precision 

Acceptable 

Accuracy 

SiO2 Yes All Yes All Yes All Yes All 

Al2O3 Yes All Yes All No 1633b No 1633b 

Fe2O3 Yes All Yes All Yes All No 1633b 

CaO Yes All Yes All No 

1633b, SY-4 

No 

1633b, SY-4 

MgO Yes All Yes All No 1633b Yes All 

Na2O Yes All Yes All No 

SY-4, GSP-2 

No 

SY-4, GSP-2 

K2O Yes All Yes All No 1633b No SY-4 

TiO2 Yes All No GSP-2 Yes All Yes All 

 

It is evident from this table that there are significantly more quality exceptions for the sinter-acid 

and acid-old procedure than for the recommended mixed-acid digestion procedure. In particular, 

there are a significant number of exceptions for the NIST 1633b sample. The following 

explanations are offered for the trends observed in table B.2.3. 

Of the three CRM samples NIST 1633b is the only sample that contains combustible carbon. The 

amount is in the order of 3.4 weight percent. The NIST1633b test portions treated by the sinteracid digestion procedure were not preignited at a temperature sufficient to remove this combustible 

carbon. The IGL confirmed that the sinter-acid digestion solutions contained a visible gray residue. 

53
This residue not only has the potential to absorb soluble oxides but also to create erratic flow of the 

sample through the ICP nebulizer. 

On the other hand, all three CRM samples were preignited at a temperature that not only eliminates 

combustible carbon, but also decomposes mineral carbonates, sulfides and hydrates prior to 

treatment by the recommended mixed-acid digestion procedure. Based on the above observation, 

all samples should be preignited as recommended in the section on preparation of ash in ASTM D 

6349. 

The original Na2O values reported to CANSPEXTM could not be obtained from the sinter-acid 

digestion as sodium peroxide (Na2O) is used in the sintering step. The Na2O values were obtained 

from an acid digestion procedure similar to the ASTM D 6349 mixed-acid digestion procedure with 

the exception the USGS acid digestion procedure which employs perchloric acid. This procedure is 

referred to as Acid-Old in this report. The Acid-Old Na2O values were determined on an entirely 

separate solution from all other oxides. However, the correction factor applied to the Acid-Old 

Na2O values is dominated by the total of oxides from the sinter-acid procedure. This amounts to 

extrapolation of a total from one sample to another and this can be dangerous. 

On the other hand, all oxides are determined on the same solution prepared by the mixed-acid 

digestion procedure. As a result, it can be expected that the correction factor should be equally 

suitable for all oxides. This observation reveals a distinct advantage of a single mixed-acid 

digestion procedure over separate digestion procedures. 

Finally, table B.2.3 above and the graphs in figs. B.2.1-8 that follow provide strong evidence that a 

significant shift in nebulization is occurring from sample to sample during the ICP analysis. This 

effect can be monitored and reconciled through the use of one or more internal standards added to 

each analysis solution. 

Follow up 

It is recommended that the IGL prepare two separate test portions of each ignited CRM material for 

ICP analysis using the recommended mixed-acid digestion procedure as well as the sinter-acid 

digestion procedure. The same internal standard should be added to each test solution. The test 

solutions should be run on two separate days in the following sequence. 

Mixed-Acid Portion 1, Mixed-Acid Portion 2, Sinter-Acid Portion 1, Sinter-Acid Portion 2 

 

The same analytical lines are to be used for all test solutions and oxide values, oxide intensities, 

and internal standard intensities should be reported for all test solutions. 

54
Figure B.2.1. The comparison of reported and corrected silica oxide values for the three certified 

reference materials. The Y-axis is the weight percent concentration of the analyte. The x-axis of the 

graph specifies the oxide, the digestion method Acid (mixed-acid) or Sinter (sinter-acid), the results 

displayed Rep (reported oxide value) or Corr (corrected oxide value), the CRM source and 

designation and the year sequence the CRM was originally distributed. 

55
Figure B.2.2. The comparison of reported and corrected Aluminum oxide values for the three 

certified reference materials. The Y-axis is the weight percent concentration of the analyte. The xaxis of the graph specifies the oxide, the digestion method Acid (mixed-acid) or Sinter (sinteracid), the results displayed Rep (reported oxide value) or Corr (corrected oxide value), the CRM 

source and designation and the year sequence the CRM was originally distributed. 

56
Figure B.2.3. The comparison of reported and corrected Iron oxide values for the three certified 

reference materials. The Y-axis is the weight percent concentration of the analyte. The x-axis of the 

graph specifies the oxide, the digestion method Acid (mixed-acid) or Sinter (sinter-acid), the results 

displayed Rep (reported oxide value) or Corr (corrected oxide value), the CRM source and 

designation and the year sequence the CRM was originally distributed. 

57
Figure B.2.4. The comparison of reported and corrected Calcium oxide values for the three 

certified reference materials. The Y-axis is the weight percent concentration of the analyte. The xaxis of the graph specifies the oxide, the digestion method Acid (mixed-acid) or Sinter (sinteracid), the results displayed Rep (reported oxide value) or Corr (corrected oxide value), the CRM 

source and designation and the year sequence the CRM was originally distributed. 

58
Figure B.2.5. The comparison of reported and corrected Magnesium oxide values for the three 

certified reference materials. The Y-axis is the weight percent concentration of the analyte. The xaxis of the graph specifies the oxide, the digestion method Acid (mixed-acid) or Sinter (sinteracid), the results displayed Rep (reported oxide value) or Corr (corrected oxide value), the CRM 

source and designation and the year sequence the CRM was originally distributed. 

59
Figure B.2.6. The comparison of reported and corrected Sodium oxide values for the three 

certified reference materials. The Y-axis is the weight percent concentration of the analyte. The xaxis of the graph specifies the oxide, the digestion method Acid (mixed-acid) or Sinter (sinteracid), the results displayed Rep (reported oxide value) or Corr (corrected oxide value), the CRM 

source and designation and the year sequence the CRM was originally distributed. 

60
Figure B.2.7. The comparison of reported and corrected Potassium oxide values for the three 

certified reference materials. The Y-axis is the weight percent concentration of the analyte. The xaxis of the graph specifies the oxide, the digestion method Acid (mixed-acid) or Sinter (sinteracid), the results displayed Rep (reported oxide value) or Corr (corrected oxide value), the CRM 

source and designation and the year sequence the CRM was originally distributed. 

61
Figure B.2.8. The comparison of reported and corrected Titanium oxide values for the three 

certified reference materials. The Y-axis is the weight percent concentration of the analyte. The xaxis of the graph specifies the oxide, the digestion method Acid (mixed-acid) or Sinter (sinteracid), the results displayed Rep (reported oxide value) or Corr (corrected oxide value), the CRM 

source and designation and the year sequence the CRM was originally distributed. 

62
Appendix B.3

Phase 3: On-Site Evaluation of USGS IGL 

 September 12- 14, 2005 

 

 

 

Performance Audit of U.S. Geological Survey Inorganic Geochemistry and 

Contract Laboratories 

 

Requisition #3-2920-1052 

 

 

 

 

 

October 11, 2005 

 

 

 

 

 

Louis Janke, President 

Quality Associates International®

, LDT. 

P.O. Box 117 

Douglas, ON K0J 1S0 

Canada 

63
Introduction

An on-site of the USGS Inorganic Laboratory (IGL) was conducted September 11-14, 2005. This 

task had two primary goals. The main purpose was to verify that the recommendations made in 

Phase 1 for improving the analytical performance had been successfully implemented. Secondly, 

assistance in developing a standard operating procedure (SOP) for each analytical methodology 

employed by the IGL as part of developing a total quality management system was requested 

General Findings

The on-site audit confirmed recommendations for analytical practices intended to improve the 

efficiency and reliability of test results have been implemented and are being monitored on an ongoing basis to substantiate the effectiveness of the recommendations. The recent implementation of 

a blinds testing program should provide the recommended ongoing, real time monitoring of 

laboratory performance. 

There was not sufficient time to perform a detailed analysis of each analytical process so the 

remainder of this report contains a summary of best practices. Recommendations and examples 

included in this report do not constitute current or future practices or procedures employed at the 

U.S. Geological Survey (USGS), Inorganic Geochemistry Laboratory (IGL. It is the responsibility 

of USGS management and staff to review the recommendations and examples to decide whether 

they can be in whole or in part incorporated into current SOPs without adversely impacting the 

quality of results produced by the IGL. 

One critical aspect of coal analysis that is fundamental to obtaining credible analytical results 

especially needs to be addressed. This is the concept of taking the proper steps to ensure that every 

sample taken is representative of the intended purpose. While this is ultimately outside the IGL’s 

direct scope of responsibility, there needs to be close coordination between the sample 

collectors/submitters and the IGL personnel. Practices employed to collect samples should be 

compared with the procedures cited in this document. If it is not possible to implement comparable 

procedures, the IGL should implement procedures that can identify sources and causes of sample 

variability that could detract from the reliability of analytical results. 

Collection of Coal Samples

According to ASTM D 2013 “Standard Practice for Preparing Coal Samples for Analysis”, there 

are two groups into which coals fall: 

Group A: Coals that have been cleaned in all sizes. 

Group B: All other coals. Unknown coals are to be considered in group B. 

Unless the USGS has information to the contrary, all coals submitted for analysis should be 

considered as being in group B. Table 1 of ASTM D 2013 stipulates a minimum mass of 4 kg of 4 

mesh (4.75 mm). Group B coal is required for subdivision to produce a representative and 

homogeneous 60 mesh (250 μm) analysis sample. The mass of the analysis sample shall not be less 

64
than 50 g. To obtain the 4 kg of 4 mesh coal, a gross sample must be taken. Gross samples can be 

collected as mine samples or as commercial samples. Table B.3.1 lists the relevant ASTM 

standards for collection of mine samples and commercial samples. 

Table B.3.1. The relevant ASTM standards for collection of mine samples and commercial 

samples. 

Minimum Increment 

Mass 

ASTM 

Standard 

Type of 

Sample 

Source of 

Sample Minimum Increments

16mm 

(5/8 

inch) 

50 mm 

(2 inch)

150 mm

(6 inch)

D 4596 Mine Channel Specification A 3 kg 3 kg 3 kg 

D 2234 Commercial Stopped belt Specification B 1 kg 3 kg 7 kg 

D 2234 Commercial Full Stream Specification B 1 kg 3 kg 7 kg 

D 2234 Commercial Part Stream Specification B 1 kg 3 kg 7 kg 

D 6609 Commercial Part Stream Specification B 1 kg 3 kg 7 kg 

D 6883 Commercial 

Railroad Cars 

Barges 

Trucks 

Stockpiles Specification B 1 kg 3 kg 7 kg 

D 4916 Commercial Auger Specification B 1 kg 3 kg 7 kg 

Specification A: One increment 29 cm high by 10 cm wide by 8 cm deep for each 30 cm of seam 

thickness. For seams of less than 40 cm thickness multiple channel samples are required to produce 

the minimum 4 kg of 4 mesh (4.75 mm) 

Specification B: N= × Mg 908/35 , where Mg is mega-grams of coal. The minimum amount of 

coal to be sampled is 908 mega-grams. Each sampling standard provide guidance on geometrical 

and temporal spacing of increments. 

Examples: 

Six barges contain 1362 Mg (1500 tons) of raw coal each. The entire lot comprises 8292 Mg. 

According to ASTM D 6883 the total number of increments is calculated according to specification 

B, 

N = × 908/829235 = 105 increments. This is 17.5 increments per barge or 18 rounded off. 

The total gross sample would be top size 16mm 108 kg, top size 50 mm 324 kg, and top size 150 

mm 756 kg. 

A coal seam is 174 cm thick. According to ASTM D 4596, the total sample taken would be 174 

cm. thick by 10 cm wide by 8 cm deep. This gives a total volume of coal of 13,920 cm3

. At a 

density of approximately 1.3 g/cm3

 this yields approximately 18 kg of coal. 

65
Collection of Ash Samples 

Coal-derived ash falls into two groups, laboratory ash and solid combustion residues (utility ash). 

Utility ash can consist of, but is not limited to, bottom ash, bed ash, super heater tube ash, fly ash, 

bag house ash, and scrubber sludge. Collection of a representative and homogeneous sample of 

utility ash requires specialized probes that can be inserted in the ash stream. It is recommended that 

not less than 3 kg of utility ash is collected for analysis. Prepare laboratory ash according to the 

section on preparation of ash samples for analysis. 

Sample Preparation, Storage and Handling

Preparation of coal samples for analysis 

While awaiting preparation, store gross samples in containers that prevent a change in the moisture 

condition of the gross sample. 

Gross samples normally require air-drying to properly feed through size reduction (crushing) and 

dividing equipment. Air dry gross samples in accordance with ASTM D 3302. Do not air-dry coal 

samples at temperatures in excess of 30 oC, as all coals are subject to some oxidation at 

temperatures in excess of 30 oC. 

Employ equipment for size reduction that minimizes either moisture loss or gain during the 

reduction stage. 

After each stage of reduction, employ an enclosed riffle to split the coal sample. The chutes and 

riffle slots shall have a slope of at least 60o. The sample shall be fed into the riffle employing a 

scoop with straight sides and a width equal to the effective width of the riffle. To generate splits as 

close to equal mass as possible, ensure sufficient sample is produced after each stage of reduction 

to fill the riffle scoop. Table B.3.2 lists the recommended riffle slot sizes for particle sizes at each 

stage of reduction. 

Table B.3.2. The recommended riffle slot sizes for particle sizes at each stage of sample reduction 

Particle size Mesh Riffle slots (inches) Riffle slots (mm) 

4.75 mm 4 0.75-1.00 18-25 

2.36 mm 8 0.75-1.00 18-25 

0.250 mm 60 0.25-0.375 6-10 

Employ figure 3 of ASTM D 2013 to plan and carry out the preparation of the 60 mesh (250 μm) 

analysis sample. Transfer a minimum of 50 g of coal (Note 1) to a closed container. Do not fill the 

container to more than 2/3 of total capacity. Take an equivalent quantity reserve at the same time. 

Verify once a month that an internally prepared sample passes 100% through a 60 mesh (250 μm) 

sieve and post as internal sample verified and the date of verification prominently in the sample 

preparation area. 

66
Verify once a month that an externally prepared sample passes 100% through a 60 mesh (250 μm) 

sieve and post the source of the sample and the date of verification prominently in the sample 

preparation area. 

Note 1 - Since all test portions for analysis are to be taken from the same bottle of coal, it is 

necessary to calculate the amount of coal required for all tests. In the case of the IGL, the 

amount required allowing for duplicates, repeats and blinds is 30 g for a coal of 10% ash 

content. 

Preparation of ash samples for analysis 

The procedures described below are suitable for the preparation of laboratory ash from coal or the 

ignition of utility ash. Ashes prepared according to the procedure below should be immediately 

treated for analysis. Since ash can absorb moisture or carbon dioxide from the atmosphere, reignite 

ash that is stored for subsequent analysis or ash that has been received from an outside source 

according to the conditions specified below. 

Equipment 

Muffle furnace, with unexposed elements and a sheathed thermocouple. The furnace shall be 

equipped to allow for 2 to 4 air changes a minute. The furnace shall be capable of being 

programmed to heat from approximately 3 oC per minute to 8 oC per minute. The final soak 

temperature of the working surface of the furnace shall be maintained within 450-500 oC for 

preparation of ash for trace analysis and within 700-750 oC for preparation for major and minor 

analysis. 

Ignition crucible, quartz, porcelain or fused silica crucibles. The crucible shall be of sufficient 

capacity to produce 2 g of ignited sample. The sample to be ignited is not to exceed 6 mm (1/4 

inch) in depth. Do not employ crucibles with a pitted or flaked interior surface. 

Procedure 

Clean the muffle furnace with a vacuum or air hose prior to use. 

At no time during the preparation of laboratory ash from coal should the sample be allowed to 

ignite. Should ignition occur, the temperature in the sample is likely to be significantly higher than 

the one to which the muffle is controlled, resulting in the loss of volatile trace elements. 

Remove ignited samples while the furnace is still at the final soak temperature. Do not allow 

ignited samples to cool down in the furnace. The interior surfaces of muffle furnaces are subject to 

spalling (flaking or crumbling) during cool down. This can result in contamination of the ash 

sample and is one of the primary reasons for cleaning the muffle prior to use. 

An ash sample prepared according to the conditions specified for Ignition of Samples for Trace 

Analysis can be treated starting at Stage 2 of Ignition for Samples Major and Minor analysis. 

67
Ignition of Samples for Trace Analysis 

Stage 1 - Weigh a quantity of sample that will yield not less than 2 g of ash, into an ignition 

crucible. Place the ignition crucible in the working surface of a muffle at ambient temperature. 

Program the furnace so that it reaches a temperature of 300 oC in 1 hour (~ 4 oC/min). Hold at this 

temperature until all evidence of smoking has ceased. 

Stage 2 - Program the furnace so that it reaches a temperature of 500 oC (~ 3 oC/min) in another 

hour. Hold at the final soak temperature for not less than 2 hours. Remove the sample and cool to 

ambient at conditions that minimize absorption of water or carbon dioxide. Stir the sample. If 

carbonaceous material is present (Note 2), place the sample back in the muffle at the final soak 

temperature and ignite for an additional of 4 hours. Remove the sample and cool to ambient at 

conditions that minimize absorption of water or carbon dioxide (Note 3). Immediately weigh test 

portions for subsequent treatment for analysis. Store and retain unused ash in sealed containers for 

repeat, blind or major and minor analysis. The containers shall minimize the opportunity for 

contamination or loss of trace analytes as well as the absorption of water or carbon dioxide. 

Note 2-In the case of laboratory ash prepared from coal, no carbonaceous material should 

remain after a total ignition time of 6 hours at the final soak temperature. In the case of solid 

combustion residues from utility source, is it is possible that some carbonaceous material can 

persist. This indicates the presence of “graphitic” carbon that is unlikely to decompose at a 

temperature of 500 oC. 

 

Note-3- Some samples can have a composition that promotes the formation of a low melting 

eutectic, causing the ash sample to partially fuse at the final soak temperature. If this occurs, 

grind the ignited sample in a non-contaminating (alundum) mortar and pestle and screen 

through a 200 mesh (75 μm) kevlar sieve. 

Ignition of Samples for Major and Minor Analysis 

Stage 1-Weigh a quantity of sample that will yield not less than 2 g of ash, into an ignition crucible. 

Place the ignition crucible in the working surface of a muffle at ambient temperature. Program the 

furnace so that it reaches a temperature of 500 oC in 1 hour (~ 8 oC/min). Hold at this temperature 

until all evidence of smoking has ceased. 

Stage 2-Program the furnace so that it reaches a temperature of 750 oC (~ 4 oC/min) in another 

hour. Hold at the final soak temperature for not less than 2 hours. Remove the sample and cool to 

ambient at conditions that minimize absorption of water or carbon dioxide. Stir the sample. If 

carbonaceous material is present, place the sample back in the muffle at the final soak temperature 

and ignite for an additional 4 hours (Note 2). Remove the sample and cool to ambient temperature 

at conditions that minimize absorption of water or carbon dioxide (Note 3). Immediately weigh test 

portions of the sample for subsequent treatment for analysis. Store and retain unused ash in sealed 

containers for repeat or blind analysis. The sealed containers will minimize the opportunity for 

contamination, as well as the absorption of water or carbon dioxide. 

68
Sample Storage 

Establish a common area for the storage of all reserve samples, quality control samples, and blind 

samples not currently in use. 

Quality control materials can be categorized as conditioning samples, calibration samples, or 

control samples. These samples can be pure substances, certified reference materials, external 

reference materials, or internal reference materials. Do not use a quality control material that is 

removed from the laboratory for internal control purposes. 

Keep a copy of all certificates provided by the suppliers of pure substances, certified reference 

materials, and external reference materials. Mark the date of receipt on the certificate. Mark the 

date of receipt and, if appropriate, the date of expiry on the control material container. 

Mark all internal reference materials with the date of preparation. 

Mark each control material container with a replacement line 1⁄4 of the height of the sample in the 

container. 

When the level of an active quality control material reaches the replacement line bring a substitute 

container of the same or an alternative quality control material into the laboratory for verification. 

Run the substitute quality control material as an unknown to verify the material meets acceptance 

limits. Mark the date of verification on the control material. 

Blind samples can be provided by external or internal sources. Analyze blind samples with a 

routine batch of samples within 2 weeks of receipt. Run duplicate test portions of the blind sample, 

unless otherwise specified by the submitter. Report blind results to the submitter within 24 hours of 

completion of the analysis. Verify and report all relevant quality control data (in control and out of 

control) with the blind results. 

Quality Control

Instrument Maintenance 

Instrument maintenance sheets shall be posted on or immediately adjacent to each instrument. 

Specific maintenance criteria are specified in each method SOP. 

Validated Operators 

The IGL shall only report results produced by validated operators. Each validated operator shall be 

capable of conducting all instrument set up, conditioning, and quality control checks. 

The IGL shall initially verify individual analysts as validated operators by having the analyst 

conduct blind analysis of selected control materials that cover the normal expected range of 

materials analyzed in the laboratory. The results and date of initial verification of each analyst shall 

be recorded in the instrument operating manual kept at the instrument station. 

69
On-going verification of validated operators shall occur through the analysis of external and 

internal blind samples. 

Instrument Conditioning 

Each method SOP shall specify requirements for instrument conditioning. At a minimum, the 

instrument conditioning runs shall produce results that do not exceed the maximum expected 

repeatability standard deviation specified for the test parameter in the relevant SOP. Conditioning 

runs shall be identified as conditioning. 

Acceptance Limits for Calibration and Control Samples 

Establish acceptance limits for each conditioning, calibration, and control material (CM). Label 

each CM with these limits. 

According to the ISO “Guide for Uncertainty Measurement” (GUM), the total uncertainty of a 

measurement is made up of the components of uncertainty that can impact the measurement result. 

The uncertainty of a measurement conducted on a CM can be expressed in equation 1 below. 

Equation 1: 

2 2 2 2 2 TCM = μμ homogeneityCM + μ MstabilityC biasCM ++ μμ precisionCM + μ precisionLabMethod 

Where; 

μhomogeneityCM is the uncertainty contributed by the inhomogeneity of the CM 

μstabilityCM is the uncertainty contributed by the stability of the CM coal 

μbiasCM is the uncertainty contributed by bias of the CM measurement process 

μprecisionCM is the uncertainty contributed by the precision of the CM 

measurement process 

μprecisionLabMethod is the uncertainty contributed by the precision of the laboratory method 

In the case of a CM μbiasCM is assumed to be 0 and μhomogeneityCM, μstabilityCM, μprecisionCM can be

combined into μCM.

So for a CM the GUM (equation 2) becomes: 

Equation 2 

2 2 T CM += μμμ precisionLabMethod 

In a laboratory operating in a state of control under repeatability conditions, the precision of the 

laboratory method should not exceed the repeatability standard deviation of the method (equation 

3). 

70
Equation 3: 

precisionLabMethod r / n

2

μ = μ 

Where: 

μr is the repeatability standard deviation of the method 

n is the number of measurements made on the standard coal 

The total uncertainty is shown in equation 4. 

Equation 4: 

T RM r / n

22

+= μμμ 

This equation indicates that the limits employed to accept or reject a calibration or control point are 

a function of two factors: 1.) the uncertainty of the CM material; and 2.) the uncertainty of the 

laboratory method. Three values are required to make use of equation 4, the value of the CM 

(CMvalue), the limits of the CM (CMlimits) and the repeatability of the laboratory method (Ir). 

Assume the following National Institute of Standard Testing (NIST) sulfur standards are employed 

for calibration of method D 4239c.The values below are from NIST certificates. 

NIST 1632c sulfur 1.462 % ± 0.051 % 

NIST 2684b sulfur 3.076 % ± 0.031 % 

NIST 2685b sulfur 4.730 % ± 0.068 %

Calculate μ CM for each standard employing equation 5 below. 

Equation 5: 

CMlimits 2/ μ CM = 

For each standard μ RM is as follows. 

NIST 1632c = 0.026 

NIST 2684b = 0.016 

NIST 2685b = 0.034 

Calculate the repeatability standard deviation for sulfur from ASTM D 4239c 

This is equivalent to the repeatability interval (Ir) divided by 2.8. 

Sr = [0.02+ 0.03(CMvalue)]/2.8 

NIST 1632c = 0.023 

NIST 2684b = 0.040 

NIST 2685b = 0.058 

71
Multiply by the ISO 5725-1 factor (1.25) to obtain the maximum expected repeatability standard 

deviation. 

NIST 1632c = 0.029 

NIST 2684b = 0.050 

NIST 2685b = 0.072 

 

The total uncertainty for each calibration standard using μT (equation 4) is: 

NIST 1632c = 0.038 

NIST 2684b = 0.053 

NIST 2685b = 0.080 

The 95% expanded uncertainties are 2 times these values. 

NIST 1632c = 0.076 

NIST 2684b = 0.106 

NIST 2685b = 0.160 

The following are limits for accepting or rejecting a calibration point for each standard. 

NIST 1632c sulfur 1.462% ± 0.076% 

NIST 2684b sulfur 3.076% ± 0.106% 

NIST 2685b sulfur 4.730% ± 0.160% 

Compare this with the NIST certificate values only. 

NIST 1632c sulfur 1.462% ± 0.051% 

NIST 2684b sulfur 3.076% ± 0.031% 

NIST 2685b sulfur 4.730% ± 0.068% 

A calibration or control point cannot be “not accepted” or rejected on the basis of the limits of the 

CM only. The precision of the laboratory method must also be included in these limits. If this is not 

done, a laboratory will have a tendency to reject acceptable conditioning, calibration or control 

runs. A laboratory could establish a calibration, run a material as a check, and find that it appears to 

be out of control, and needlessly recalibrate an instrument or reject results. This cycle can go on 

repeatedly. As a result, a great deal of expense associated with operator time and supplies could be 

unnecessarily expended. This is a case where applying fundamental quality principles can save an 

enormous amount of expenditure. 

Calibration and calibration verification 

72
The number of standards used for calibration shall not be less than the degree of the calibration 

curve plus 2 and according to the AOAC International (AOAC) should not be less than the degree 

of calibration curve plus 5. Table B.3.3 summarizes these requirements: 

Table B.3.3. The number of standards required by the type of calibration curve. 

CURVE

TYPE

DEGREE

MINIMUM NUMBER 

OF STANDARDS

AOAC RECOMMENDED 

NUMBER OF STANDARDS

LINEAR 1 3 6 

QUADRATIC 2 4 7 

CUBIC 3 5 8 

EXPONENTIAL 2 4 7 

Calculate the range of the standards as follows. 

Cu ~ 2 x CM

Where: Cu is the upper concentration standard 

CM is the highest concentration control material employed for calibration verification 

and, 

Cl = Cu/10 

Where: Cl is the lower concentration standard 

The highest concentration control material for sulfur analysis is 1.03 wt %. 

The upper calibration standard should be approximately 2.0%. 

The lower calibration standard should be approximately 0.2%. 

Space standards as equally as possible over the calibration range. 

If 6 (n=6) standards are to be used then a suitable distribution for the standards can be calculated 

from: 

D ~ (Cu)/ (n-1) 

D ~ (2)/5 ~ 0.4 

Cn+1 ~ Cn + D 

A reasonable selection of standard concentrations would be: 

C1 0.2 

C2 0.6 

C3 1.0 

C4 1.4 

C5 1.8 

C6 2.0 

73
Unless otherwise specified in the method SOP, verify the calibration a minimum of every ten 

samples after acceptance of the initial calibration and at the end of each batch of test samples. It is 

preferable that the calibration verification sample be a control material not used during calibration 

and has a value near the mid point of the calibration range. 

Many instruments have built-in calibration software. It is advisable to conduct an independent 

verification of instrument generated calibration coefficients. This can be accomplished by 

employing Excel functions to plot instrument response versus mass of calibrant. 

Establishment and Use of Control Charts

Establish control charts for each control material. 

Establish three sets of control lines on each control chart. 

The first set corresponds to the acceptance limits calculated according to equation 4 in the section 

on acceptance limits for calibration and control samples of this report. These limits should be 

shown in green. The second set corresponds to twice the acceptance limits calculated according to 

equation 4. These limits should be shown in yellow. The third set corresponds to three times the 

acceptance limits calculated according to equation 4. These limits should be shown in red. 

Plot control results on the control charts as the control results are generated. 

Values on or inside the green limits indicate the measurement system is in an optimum state of 

control, values on or inside the yellow limits indicate the system is in an acceptable state of control, 

and values outside the yellow limits require corrective action. 

If a value falls on or below the red limits, but above the yellow limits, run the control material in 

duplicate. If both duplicate runs fall below the yellow limits, analysis can proceed. The operator 

shall make note of any possible assignable cause for the quality excursion. 

Otherwise, reject all values back to the last acceptable control point. The operator shall take and 

make note of appropriate corrective action with respect to instrument maintenance, conditioning, 

and/or calibration. 

If a value falls above the red limits, run the control material in duplicate. If both duplicate runs fall 

below the green limits, analysis can proceed. The operator shall make note of any possible 

assignable cause for the quality excursion. 

Otherwise, reject all values back to the last acceptable control point. The operator shall take and 

make note of appropriate corrective action with respect to instrument maintenance, conditioning, 

and/or calibration. 

74
Within one year of implementation of each control chart, summarize the number of points inside 

the green limits, inside the yellow limits, and inside the red limits. Use the information to 

determine whether the control limits can be adjusted. 

Method Specific Standard Operating Procedures

Moisture 

International, Regional and National standards for Moisture are: 

AS 1038 

ASTM D3173 

ASTM D 5142 

BS 1016 

DIN 51718 

GB/T212 

ISO 589 

ISO 11722 

ISO 5068 

SABS 925 

The USGS IGL procedure for the determination of residual moisture content is based on ASTM D 

3173 “Standard Test Method for Moisture in the Analysis Sample of Coal and Coke”. This SOP 

describes factors that are known to affect the measurement of moisture in the analysis sample. 

Critical maintenance requirements are prefaced with an [M]. The measurement characteristic(s) 

precision and/or accuracy affected by the factor appear in brackets. 

Condition of test sample (Accuracy) 

Standards normally specify two alternatives for extracting a test portion for analysis. Procedure A 

involves mixing the sample in the bottle and extracting a test portion from the bottle for analysis. 

Procedure B involves mixing the sample in the bottle, extracting sufficient material for the test, 

allowing the material to equilibrate with the laboratory atmosphere, and then conducting analysis 

on test portions from the equilibrated material. Samples treated by procedure B can lose or pick up 

moisture depending on the ambient humidity of the laboratory. As a result, laboratories employing 

procedure B can produce residual moisture results that are either lower or higher than that produced 

by procedure A. For this reason, as well as the obvious practical limitations of ensuring the 

moisture condition of test samples exchanged by laboratories does not change, comparing residual 

moisture results determined on the analysis sample from different laboratories has absolutely no 

technical validity. 

Type of Purging Atmosphere (Accuracy) 

Studies have shown nitrogen will produce higher moisture results than air conditioned to the same 

requirements. Since the residual moisture value is employed to calculate other parameters to a dry 

basis, nitrogen as a purging atmosphere produces higher dry basis estimates for other parameters 

than air. 

75
Dryness of Purging Atmosphere (Precision & Accuracy) 

[M-Monthly or after any repair] Control the dryness of the purging atmosphere to the 

requirement specified in the standard. Verify this dryness requirement is met by passing the drying 

atmosphere through a suitable desiccant and then through a tube containing magnesium perchlorate 

for a fixed period of time. Remove the tube after a fixed period of time and weigh. By knowing the 

flow rate, the amount of moisture in the dried purging atmosphere in mg/L can be calculated. 

Insufficient Drying Time (Precision & Accuracy) 

Low rank coals have the capacity to hold significantly more moisture than higher rank coals. A low 

rank coal may not lose all of this moisture by the end of a one-hour drying period. Place low rank 

coal samples in the drying apparatus for additional half hour periods until a minimum change in 

mass is reached. The term “minimum change in mass” is used because excessive drying can result 

in oxidation of low rank coals. Studies have shown that most low rank coals will achieve a 

minimum change in mass after 1.5 to 2 hours. The example below lists the weight of 1g of low 

rank coal after an initial one hour drying period and then after each additional half hour drying 

period. The minimum mass is indicated in bold. 

1 hour.: 0.8256g, 1.5 hour: 0.8149g, 2 hour: 0.8156g, 2.5 hour: 0.8270g 

This low rank coal has residual moisture content of 18.51 wt %.

Concurrent Drying Coals of Significantly Different Rank (Precision) 

If a low rank coal is dried in a batch with higher rank coals, the coals can exchange moisture in an 

unpredictable way. Do not dry coals of significantly different rank together. 

Cooling and Weighing of Samples (Precision & Accuracy) 

[M-daily] On the same day as test samples are to be analyzed, heat empty capsules or crucibles and 

lids under the conditions at which the sample is to be dried. Cool the capsules and lids in a 

desiccator. 

Some laboratories process a large number of samples at a time in one batch. Before the latter 

samples are weighed, they can pick up moisture from the desiccator environment, particularly if the 

samples are not covered with a suitable lid. This occurs because coal can act as a better desiccant 

than certain chemical agents. Cover the sample with a lid to minimize the pick up of moisture from 

the desiccator environment as well as from other coal samples in the desiccator. Dry samples in 

batches of 6 to 8 to further minimize these effects. Once the initial batch is put in the drying 

apparatus, another batch can be weighed out no less than 15 minutes later and placed in the drying 

apparatus. Remove samples in each batch sequence from the drying apparatus at the required time 

interval, cool, and weigh. 

Ash Content 

76
International, Regional and National standards for Ash are: 

AS 1038 

ASTM D3174 

ASTM D 5142 

BS 1016 

DIN 51719 

GB/T212 

ISO 1171 

The USGS IGL procedure for the determination of ash content is based on ASTM D 3174 

“Standard Test Method for Ash in the Analysis Sample of Coal and Coke from Coal”. This SOP 

describes factors that are known to affect the measurement of ash in the analysis sample. Critical 

maintenance requirements are prefaced with an [M-frequency]. The measurement characteristic(s) 

precision and/or accuracy affected by the factor appear in brackets. 

Incineration of the sample (Precision) 

[M-Monthly or after any repair] Verify the airflow calibration of the muffle furnace is 2 to 4 air 

exchanges per minute according to figure 2 of ASTM D 3174. Verify the muffle furnace 

temperature calibration according to the section on Temperature Calibration in the standard. If 

there is no section on Temperature Calibration, the section on Temperature Calibration in ASTM D 

3174 is recommended. 

Do not place ignition crucibles closer than 1 inch to the muffle furnace door. Standards prescribe 

heating a specified weight of coal sample in a muffle furnace with a specified number of air 

changes per minute to an initial transition point within a period of 1 hour and then to a final soak 

temperature within the next hour. The sample is held at the soak temperature for a specified period 

of time. 

Interpreting the heating periods for each stage of ignition to mean the specified temperatures can be 

set to reach either 1 hour limit within any time up to and including the 1 hour, although literally 

correct, can produce erratic ash results. This is particularly true if the sample ignites during either 

ignition stage. Should this occur, the temperature in the sample will not be anything remotely 

similar to the one displayed on the temperature control display of the furnace. 

Program the muffle to rise uniformly from ambient to the initial transition point (500 oC ASTM D 

3174) in 1 hour (~ 8 oC/min.) and then uniformly to the final soak point (750 oC ASTM D 3174) in 

the second hour (~ 5 oC/min.). Programming the furnace to hold at the initial transition point until 

all evidence of smoking has ceased can further improve the precision of results. This hold period is 

normally about 1 hour. 

Final Soak Temperature (Precision & Accuracy) 

Standards specify final soak temperatures that range from 700 °C to as high as 825 °C. Ash results 

determined at the higher temperatures can be significantly less than those determined at lower 

temperatures. Studies have shown that the removal of the water of crystallization from clay 

77
minerals and the decomposition of carbonate minerals approach or reaches completion at 

temperatures in excess of 800 °C. For this reason, tighter precision can also be obtained for coals 

containing minerals with high water of crystallization content or carbonate minerals by determining 

the ash content at higher temperatures. 

Concurrent Ashing Coals of Significantly Different Rank (Precision) 

If a low rank coal is ashed with higher rank coals, sulfur can transpose from the higher rank coals 

to the low rank coal in an unpredictable way. This occurs for two reasons. As much as 80% of the 

sulfur in high rank coals can be present as pyrites (FexSy) and organic sulfur. These compounds 

readily decompose to form sulfur oxides. Most low rank coals contain appreciable quantities of 

alkali (Na2O, K2O) and alkaline (CaO, MgO) earth compounds. These compounds readily react 

with sulfur oxides to form alkali and alkaline sulfates. The extent to which these reactions occur 

can be dictated by the proximity of the low rank coal to a high rank coal. Avoid ashing low rank 

coals together with other coals. 

Cooling and weighing of Samples (Precision & Accuracy) 

Ash programs set to 4 to 6 hours often finish late at night or in the early morning hours. The 

furnace cools down and the ash samples are ready to weigh. Although this may be convenient, it 

can produce high or erratic ash values as some coal ash can pick up moisture and or carbon dioxide 

on cooling. In addition, the interior surfaces of muffle furnaces are subject to spalling (flaking or 

crumbling) during cool down. This can result in contamination of the ash sample with vagrant 

material. To minimize these affects, set the ash furnace to complete the final soak temperature 

phase just before the ash samples are to be weighed. This has the added benefit of identifying 

whether a power failure has occurred. Do not allow an ash furnace to reset after a power failure.

Even if a furnace is designed to “recover” the reactions that occur during the recovery are likely to 

be entirely different from those that would have occurred if initial ignition sequence had not been 

interrupted. 

 

Remove the sample and cool to ambient temperatures at conditions that minimize absorption of 

water or carbon dioxide. If upon cooling and weighing results appear to be erratic, immediately stir 

the ash sample to check for carbonaceous residue or fused ash. [M-As required] If the majority of 

samples exhibit one or both of these characteristics check the furnace for a burned out element or 

an open thermocouple. 

If repeat results for a single sample are erratic, stir the ash sample to check for carbonaceous 

residue. If carbonaceous residue is detected, place the samples in a muffle heated to the final soak 

temperature and reignite for an additional 2 hours [M- As required] If the results are still erratic, 

screen the original coal sample for oversize (plus 60 mesh material). If plus 60 mesh material is 

detected, report the finding to the laboratory supervisor and the submitter of the sample. 

Ash Sequence for Thermo Gravimetric Analysis (Accuracy) 

Conventional standards specify heating a coal sample in a furnace in the presence of air. Some 

standards allow the use of semi-automated or automated instruments that can be programmed to 

78
heat the sample in nitrogen at 105 o

C-110 oC to determine moisture, then in nitrogen to 900 oC-950 o

C to determine volatile, and finally in air at 700 oC-815 oC to determine ash. Heating a coal in this 

fashion can affect the decomposition of the mineral matter in such a way that less sulfur is retained 

in the ash than the coal heated in air. As a result, the ash content measured employing this approach 

in many cases is less than that obtained for samples ignited in air. 

Assuming the results obtained using the thermogravimetric analysis (TGA) ash sequence described 

above can be made equivalent to that obtained by heating in air by calibrating a TGA with coals 

whose ash content has been determined in air is completely erroneous. Reactions that occur in the 

TGA can be significantly different from those that occur in muffle purged with air. 

Consider the hypothetical case of two coals ignited in a muffle in the presence of air. The mineral 

composition of Coal A is 50 % FeS2 and 50% CaCO3. The mineral composition of Coal B is 50 % 

Fe2O3 and 50 % CaCO3. Under the muffle conditions Coal A will have a tendency to form an ash 

that contains significant amounts of Fe2O3 and CaSO4. Coal B will likely form an ash that contains 

Fe2O3 and CaO. If these two coals are ashed according to the TGA sequence above they will both 

very likely react to form an ash that consists primarily of Fe2O3 and CaO. Under the TGA ashing 

conditions specified above, Coal A ash will not be similar to that obtained in the muffle, while Coal 

B ash will, rendering the calibration meaningless. 

Ash values of coal determined in muffle in air should be used to calibrate a TGA only if the TGA is 

run under conditions that closely approximate those specified for ignition in the muffle. 

Sulfur 

International, Regional and National standards for Sulfur are: 

AS 1038 

ASTM D 3177 

ASTM D 4239 

BS 1016 

GB/T214 

ISO 351 

The USGS IGL procedure for the determination of sulfur content is based on ASTM D 4239 

‘Standard Test Method for Sulfur in the Analysis Sample of Coal and Coke Using High 

temperature Tube Furnace Combustion Methods”. This SOP describes factors that are known to 

affect the measurement of sulfur in the analysis sample. Critical maintenance requirements are 

prefaced with an [M]. The measurement characteristic(s) precision and/or accuracy affected by the 

factor appear in brackets. 

Verification of the Operating Conditions (Precision & Accuracy) 

[M-daily] The minimum temperature required to convert all sulfur present in coal sample to oxides 

of sulfur is 1350°C. Verify that the instrument meets this minimum temperature requirement. 

Although most analyzers have provisions for internal temperature verification, it is a good practice 

to verify the temperature with a separate device that has been certified (NIST traceable) for the 

79
desired temperature range. The frequency with which this is done would depend on the number of 

samples analyzed but should not be less than once a month and whenever furnace maintenance 

occurs. 

Analyzer Calibration (Precision & Accuracy) 

The instrument shall be calibrated to the AOAC requirements in the section on Calibration and 

Calibration Verification. There are two protocols that can be used for calibration of the analyzer. 

These are: 

Protocol 1: 

The dry basis values of the CMs employed for calibration are adjusted to an as analyzed value 

employing the residual moisture value (Note 4) of each CM. The results produced by the analyzer 

represent the as analyzed results. 

Protocol 2: 

The dry basis values of the Control Materials (CMs) employed for calibration remain fixed in the 

instrument. The residual moisture value (Note 4) of each CM is entered into the instrument at the 

time of calibration. The residual moisture value of each test sample must also be entered. The 

results produced by the analyzer represent the dry basis results. 

Note-4 Although determination of the residual moisture content of a CM each time the 

analyzer calibrated ensures results of the highest quality, it can result in rapid depletion of 

the CM. This requirement can be avoided by maintaining the laboratory environment at a 

constant 45 % to 55 % humidity and storing each sulfur CM without the opportunity for 

contamination in this humidity range in a exposed container in a layer not more than 6 mm 

thick. Measure residual moisture content of the CM after two days of exposure to the 

constant humidity condition. A less desirable approach is to place a relative humidity meter 

in the area where sulfur analysis is conducted. If the meter indicates a sustained change of 

20 % in relative humidity over a period of two or more days, it is necessary to verify the 

residual moisture content of each CM. 

Some standards allow coals used for calibration during a normal production period to be predried. 

This practice can be badly abused, as normal production period can be subjectively interpreted. 

Either the quantity of CM coal to be used in the production period or even entire bottles of CM coal 

are predried. The assumption that storing the CM coal in a desiccator ensures the coal remains dry 

until the entire quantity of CM is used is erroneous. To verify this practice, it is not advisable to 

weigh a coal immediately after it is dried. Store the coal in a desiccator for 2 hours and then weigh 

it again. It is very likely that the weight will have changed. When a coal is dried and allowed to 

cool to room temperature, it can pick up moisture not only from the ambient laboratory 

environment, but also from the desiccator environment after a relatively short period of time. In the 

case of low rank coals, this can occur very quickly. Assuming that dried CM samples used for 

calibration remain dry will consistently produce sulfur results that trend high. 

 

80
Despite the fact some standards allow coals to be pre-dried, the practice can be unacceptable for 

another reason. It could invalidate the CM. The user should check the CM certificate or with the 

CM provider to determine whether the CM was pre-dried to determine the certified S value. If not, 

then pre-drying for purposes of calibration is not acceptable. 

A sulfur analyzer calibrated with a CM from one source will not necessarily produce an unbiased 

result for a CM from another source. To minimize biases caused by calibrating with a single CM 

from one source, or even by multiple CMs from one source, it is good practice, if possible, to 

employ CMs from at least two sources such as NIST and SABS. 

Premature Termination of Sulfur Analysis Cycle (Precision & Accuracy) 

An instrument set to accumulate the sulfur response for 90 to 120 seconds can obtain low sulfur 

recovery particularly with coal high in components that readily react with sulfur. These 

components can react to form compounds or liquid slag that delays release of sulfur. The 

mechanisms by which these reactions take place can be extremely complex. Addition of a 

combustion aid or a mediator can minimize or prevent these reactions. Another alternative is to 

extend the analysis time to 300 seconds. Lignite and subbituminous coals tend to contain mineral 

components that can delay sulfur release. 

Chlorine 

International, Regional and National standards for Chlorine are: 

ASTM D 2361 

ASTM D 4208 

ASTM D 6721 

BS 1016 

DIN 51727-B 

EPA 9076 

ISO 587 

The USGS IGL procedure for the determination of chlorine content is based on ASTM D 6721 

“Standard Test Method for Determination of Chlorine in Coal by Oxidative Hydrolysis 

Microcoulometry”. This SOP describes factors that are known to affect the measurement of 

chlorine in the analysis sample. Critical maintenance requirements are prefaced with an [M]. The 

measurement characteristic(s) precision and/or accuracy affected by the factor appear in brackets. 

Situation and Handling of Instrument Components and Samples (Precision & Accuracy) 

Chlorine can be a prevalent contaminant in the environment. Do not locate the analyzer in an area 

where chlorine contamination is likely to occur, such as an area where hydrochloric acid is stored 

or in regular use. Wear chlorine free gloves to handle all instrument components and use platinum 

tipped tongs to handle the boats into which samples are to be weighed. 

Preparation of the Apparatus (Precision & Accuracy) 

81
[M-daily] Clean the chlorine titration cell and electrodes. Add fresh electrolyte. Fill the hydration 

tower with chlorine free distilled water. Fill the dehydration tower with fresh sulfuric acid. 

Analyzer calibration (Precision & Accuracy) 

The conditions specified in the section on recovery factor of ASTM D 6721 meet the AOAC 

requirements in the section on Calibration and Calibration Verification.

Determination Chlorine Content (Precision & Accuracy) 

Samples high in chlorine content (> 2000 μg/g) can result in an over titration condition, indicated 

by a negative instrument response. This scenario results in an underestimation of chlorine content. 

The chlorine content of samples exhibiting this characteristic shall be corrected for the over 

titration. 

Limits of Application of Standard Methods (Precision & Accuracy) 

A standard method calibrated, employing primary chemical substances, can be expected to produce 

results with minimal bias. In this case, compliance with the provisions of the standard method 

without modification should produce results with a precision at least equivalent to the repeatability 

of the method. 

The repeatability of a standard method can be used to calculate the expected ± 2s (2 standard 

deviation) uncertainty of a chlorine value at different levels of chlorine in coal. Assume a method 

should not be used to report a value with a ± 2s uncertainty that exceeds 20 % of the measured 

value. The point at which the ± 2s uncertainty of each standard method reaches 20 % of the 

measured chlorine value is highlighted in bold in table B.3.4. 

From table B.3.4, these standards as written and without modification can be used down to the 

following chlorine concentrations in coal: 

ASTM D 2361, BS 1016, ISO 587: 1000 μg/g Cl 

ASTM D 4208: 300 μg/g Cl 

 ASTM D 6721: 10 μg/g Cl

Table B.3.4. The point at which the ± 2s uncertainty of each standard method reaches 20% (in 

bold) of the measured chlorine value. 

Cl μg/g ± 2s Uncertainty ASTM 

D2361, BS 1016, ISO 587 

± 2s Uncertainty 

ASTM D 4208 

± 2s Uncertainty 

ASTM D 6721 

2000 10% 10% 5% 

1000 20% 15% 5% 

300 70% 20% 5% 

50 430% 80% 5% 

20 1070% 180% 10% 

10 2145% 355% 20% 

82
The limit of application of the ASTM D 2361, BS 1016 and ISO 587 titration method appears to be 

unreasonably high. Examination of the three methods reveals the equation for the calculation of 

chlorine content is: 

(V2N3.545Cl −××= V1)/m 

Where: 

Cl is the chlorine content in wt % 

N is the normality of the titration solution 

V2 is the volume of titrant required to titrate the test solution 

V1 is the volume of titrant require for the blank 

m is the mass of the coal sample in grams 

All three standards allow for a 0.025 normal titration solution. In this case, the equation above 

reduces to 

(V2886Cl −×= V1)/m

Where: Cl is the chlorine content in μg/g 

In other words, for a 1 gram sample of coal, a 1 mL difference between the volume required to 

titrate the test solution (V2), and the volume required to titrate the blank (V1) is equivalent to a 

concentration of 886 μg/g chlorine. A 0.1 mL difference is equivalent to equivalent to a 

concentration of 88.6 μg/g chlorine. 

Clearly, to determine chlorine, the titration device must dispense titrant with very small volume 

errors. In addition, it is essential to keep the final volume of the solution to be titrated to 100 mL 

and preferably to 50 mL as the solubility product of silver chloride can restrict the lower 

quantitative limit. Add to this the increase in the solubility of silver chloride created by the diverse 

ion effect as a result of the presence of other salts that are most certainly generated during Eschka 

and ignition or bomb combustion and the determination of chlorine by ASTM D 2361, BS1016 and 

ISO 587, and this becomes a rather complex exercise in chemistry. 

Bomb Decomposition as a Preparation Technique (Precision & Accuracy) 

Certain standards include a preparation method that involves igniting coal in a stainless steel bomb 

in an oxygen atmosphere. A solution is added to the bomb to absorb the chlorine compounds. The 

absorbing solution is treated to convert chlorine compounds to chloride in solution. Careful rinsing 

of all internal bomb surfaces, the crucible, electrodes, and valves is necessary to ensure complete 

recovery of chlorine and to prevent run-to-run memory effects. Chlorine can also be trapped in the 

bomb or crucible alloy, contributing to low recovery and run-to-run memory affects. Halide 

resistant bombs, platinum electrodes, and a platinum combustion crucible can minimize these 

effects. 

83
This method is generally unsuitable for samples that do not burn well, such as ashes and fuels of 

low reactivity. Although combustion aids can be used for ashes and low reactivity fuels, these 

materials must be free of chlorine. 

Mercury 

International, Regional and National standards For Mercury are: 

ASTM D 3684 

ASTM D 6414 

ASTM D 6722 

EPA 7473 

GB/T16659 

ISO 15237 

The USGS IGL procedure for the determination of mercury content is based on ASTM D 6414 

“Standard Test Method for Total Mercury in Coal and Coal Combustion Residues by Acid 

Extraction or Wet Oxidation/ Cold Vapor Atomic Absorption”. This SOP describes factors that are 

known to affect the measurement of mercury in the analysis sample. Critical maintenance 

requirements are prefaced with an [M]. The measurement characteristic(s) precision and/or 

accuracy affected by the factor appear in brackets. 

Acid Extraction/Wet Oxidation as a Preparation Technique (Precision & Accuracy) 

ASTM D 6414 involves extracting up to 2 g of coal in a sealed container. The method can be 

adapted for samples of very high or very low mercury content by adjusting the weight of sample. 

The method is suitable for ash materials. The method may not be suitable for extraction of mercury 

from anthracitic coals and furnace or foundry coke. In the case of these materials, it is speculated 

mercury may be included in refractory carbon structures that do not readily decompose in the 

digestion process. 

Sample Digestion 

The USGS IGL employs a hot block for sample digestion. Significant deformation of the digestion 

tubes has been noted for certain coal samples. This can be attributed in part to the oxidation of 

organic coal structures by the nitric acid employed in the digestion step. The depletion of nitric acid 

associated with the reaction with coal could result in incomplete extraction of mercury from the 

coal matrix. In addition, the soluble organic compounds produced by oxidation of the coal could 

react with potassium permanganate added to the digestion to promote complete oxidation of 

mercury. 

Analyzer Calibration (Precision & Accuracy) 

The instrument shall be calibrated to with the AOAC requirements in the section on Calibration 

and Calibration Verification. 

Limit of Application of Standard Methods (Precision & Accuracy) 

84
A standard method calibrated employing primary chemical substances can be expected to produce 

results with minimal bias. Compliance with the provisions of the standard method without 

modification should produce results with a precision at least equivalent to the repeatability of the 

method. 

The repeatability of a standard method can be used to calculate the expected ± 2s (2 standard 

deviation) uncertainty of a mercury value at different levels of mercury in coal. Assume a method 

should not be used to report a value with a ± 2s uncertainty that exceeds 20 % of the measured 

value. The point at which the ± 2s uncertainty of each standard method reaches 20 % of the 

measured mercury value is highlighted in bold in Table B.3.5. 

Table B.3.5. The point at which the ± 2s uncertainty of each standard method reaches 20% (bold) 

of the measured mercury value. 

Hg ng/g ± 2s Uncertainty

ASTM D 3684 

± 2s Uncertainty 

ISO 15237 

± 2s Uncertainty 

ASTM D 6414 

± 2s Uncertainty 

ASTM D 6722 

250 10% 15% 10% 5% 

200 15% 15% 10% 5% 

140 20% 15% 15% 10% 

100 25% 20% 15% 10% 

70 35% 20% 20% 10% 

40 65% 25% 30% 20% 

20 130% 40% 50% 35% 

From this table the standard as written and without modification can be used down to the following 

mercury concentrations in coal: 

ASTM D 3684 140 ng/g 

ISO 15237 70 ng/g 

ASTM D 6414 70 ng/g 

ASTM D 6722 40 ng/g 

Bomb Decomposition as a Preparation Technique (Precision & Accuracy) 

ASTM D 3684 and ISO 15237 involve igniting approximately 1 g of coal in a stainless steel bomb 

in an oxygen atmosphere. The lower limit of the method is constrained by the maximum weight of 

coal that can be burned. The method is generally unsuitable for samples that do not burn well such 

as ashes and fuels of low reactivity. Although combustion aids can be used for ashes and low 

reactivity fuels, these materials must be mercury free. 

Careful rinsing of all internal bomb surfaces, the crucible, electrodes, and valves is necessary to 

ensure complete recovery of mercury and to prevent run-to-run memory effects. Mercury reacts 

readily with chlorine and can be trapped in the bomb or crucible alloy, contributing to low recovery 

and run-to-run memory affects. Halide resistant bombs, platinum electrodes and a platinum 

combustion crucible can minimize these effects. 

85
ISO 15237 requires the bomb washings and residues to be collected in a 100 mL volumetric flask. 

Prior to dilution to 100mL, 0.5 mL of a (50 g/L) potassium permanganate solution is added. The 

final solution is transferred to a mercury free vessel and heated at 90 oC for 60 minutes in a suitable 

digestion block. These additional precautions have been found to improve the recovery of mercury 

as well as the precision of analysis (see ± 2s mercury, table B.3.5). 

Direct Combustion for the Analysis of Mercury (Precision & Accuracy) 

ASTM D 6722 involves igniting a milligram quantity of coal in a combustion train and capturing 

the mercury in its elemental state on gold amalgam. The method can be adapted for samples of very 

high or very low mercury content by adjusting the weight of sample. The method is suitable for ash 

materials. Some samples can cause problems with uniform combustion depending on their moisture 

content or mineral composition. These samples may explode or “spark” in the combustion train, 

carrying material out of the combustion region before mercury is completely released. 

Some evidence suggests high concentrations of selenium (> 4 μg/g) in coal may cause incomplete 

and erratic recovery of mercury during direct combustion analysis. It has not been determined if the 

form of selenium in coal leads to this problem or, for that matter, how the selenium “interferes” 

with the collection and detection of a uniform species of mercury. If erratic results for a test sample 

are obtained, blanks should be run until the instrument stabilizes. Run a CRM or RM mercury 

standard that is known to produce results for acceptable precision to verify accuracy and stability. 

If the CRM and/or RM standard(s) are within acceptable limits, check the selenium value of the 

suspect test sample. 

Majors and Minor Elements 

International, Regional and National standards for Major and Minor Oxides are listed in table 

B.3.6. 

Based on the law of propagation of errors, the expected total for the major and minor oxides listed 

in the table B.3.6 for an in control measurement system should be from 97.5 weight percent to 

102.5 weight percent on an ignited basis. An oxide total outside these limits indicates the 

measurement system may not be in control, or the presence of an analyte in an amount not 

normally encountered in coal-derived ash. 

Table B.3.6. The major and minor oxides normally determined in coal ash and the relevant 

applicable standards. 

Oxide Relevant Standards 

Na2O AS 1038, ASTM D 3682, ASTM D 6349, DIN 51729, GB/T4634 

MgO AS 1038, ASTM D 3682, ASTM D 6349, DIN 51729, GB/T4634 

Al2O3 AS 1038, ASTM D 3682, ASTM D 6349, DIN 51729, GB/T1574 

SiO2 AS 1038, ASTM D 3682, ASTM D 6349, DIN 51729, GB/T1574 

P2O5 AS 1038, ASTM D 2795, ASTM D 6349, DIN 51729, GB/T1574 

SO3 ASTM D 5016, DIN 51729, GB/T1574 

86
K2O AS 1038, ASTM D 3682, ASTM D 6349, DIN 51729, GB/T4634 

CaO AS 1038, ASTM D 3682, ASTM D 6349, DIN 51729, GB/T4634 

TiO2 AS 1038, ASTM D 3682, ASTM D 6349, DIN 51729, GB/T1574 

Fe2O3 AS 1038, ASTM D 3682, ASTM D 6349, DIN 51729, GB/T4634 

SrO AS 1038, ASTM D 3682, ASTM D 6349, DIN 51729 

BaO AS 1038, ASTM D 3682, ASTM D 6349, DIN 51729 

The USGS IGL procedure for the determination of major and minors is based on ASTM D 6349 

“Standard Test Method for Determination of Major and Minor Elements in Coal, Coke and Solid 

Combustion Residues from Coal and Coke by Inductively Coupled Plasma-Atomic Emission 

Spectroscopy”. This SOP describes factors that are known to affect the measurement of majors and 

minors in the prepared ash sample. Critical maintenance requirements are prefaced with an [M]. 

The measurement characteristic(s) precision and/or accuracy affected by the factor appear in 

brackets. 

Analyzer calibration (Precision & Accuracy) 

The instrument shall be calibrated to the AOAC requirements in the section on Calibration and 

Calibration Verification. 

Trace Elements 

 

Table B.3.7 lists the trace constituents normally determined in coal ash and the relevant applicable 

standards. A standard method calibrated employing primary chemical substances can be expected 

to produce results with minimal bias. Compliance with the provisions of the standard method 

without modification should produce results with a precision at least equivalent to the repeatability 

of the method. The repeatability of a standard method can be used to calculate the expected ± 2s (2 

standard deviation) uncertainty of a trace element at different levels of the trace element. The 

expected percent uncertainty of the measured value over the normally expected range of each trace 

element in ash is listed in table B.3.7. 

Table B.3.7. The relevant applicable standards and expected percent uncertainty of the measured 

value over the normally expected range of each trace element normally determined in coal ash. 

Values with a ± 2s uncertainty that exceeds 20 % of the measured value are shown in bold. 

Trace 

Analyte Relevant Standards 

± 2s μg/g 

AS 1038 

± 2s μg/g 

ASTM D 

3683 

± 2s μg/g 

ASTM D 

6357 

Be AS 1038 ASTM D 3683 ASTM D 6357 10 % 35 % 5 % 

V AS 1038 ASTM D 3683 ASTM D 6357 5 % 20 % 10 % 

Cr AS 1038 ASTM D 3683 ASTM D 6357 10 % 15 % 5 % 

Mn AS 1038 ASTM D 3683 ASTM D 6357 5 % 10 % 5 % 

Co ASTM D 6357 10 % 

Ni AS 1038 ASTM D 3683 ASTM D 6357 10 % 70 % 10 % 

Cu AS 1038 ASTM D 3683 ASTM D 6357 5 % 10 % 10 % 

Zn AS 1038 ASTM D 3683 ASTM D 6357 5 % 20 % 5 % 

87
As ASTM D 6357 10 % 

Mo ASTM D 6357 10 % 

Cd ASTM D 6357 20 % 

Sb ASTM D 6357 20 % 

Pb AS 1038 ASTM D 3683 ASTM D 6357 15 % 70 % 10% 

The USGS IGL procedure for the determination of trace is based on ASTM D 6357 "Standard 

Methods for Determination of Trace Elements in Coal, Coke and Combustion Residues from Coal 

Utilization Processes by Inductively Coupled Plasma Atomic Emission Spectrometry, and Graphite 

Furnace Atomic Absorption Spectrometry”. This SOP describes factors that are known to affect the 

measurement of trace in the prepared ash sample. Critical maintenance requirements are prefaced 

with an [M]. The measurement characteristic(s) precision and/or accuracy affected by the factor 

appear in brackets. 

Assume a method should not be used to report a value with a ± 2s uncertainty that exceeds 20 % of 

the measured value. Although the table B.3.7 is only a guide, it suggests ASTM D 3683 should not 

be used for Be, Ni, or Pb. On the other hand both AS 1038 and ASTM D 6357 appear to be 

adequate for the entire suite of trace elements for which they are cited in the table. The uncertainty 

for Be and V by AA should be greater than ICP-AES, ICP-MS, while the uncertainty for analytes 

such as Cr, Mn, Cu should be similar for all finishes. Table B.3.7 tends to support this notion. 

The standard AS 1038, which specifies conditions for preparation and selection of calibration 

standards that more rigorously comply with the fundamentals of calibration cited in the section 

Calibration and Calibration Verification, appears to be suitable for measuring significantly lower 

limits of trace elements than ASTM D3683. 

Analyzer calibration (Precision & Accuracy) 

The instrument shall be calibrated to the AOAC requirements in the section on Calibration and 

Calibration Verification. 

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Appendix B.4 

References for Cited Standards and Organizations 

The reports comprising Appendices A and B contain multiple reference citations to standard 

methods and other contacts. To facilitate review of the documents the reference was not provided 

every time a standard test method or organizational contacts was cited. Information regarding these 

citations is provided below: 

Standard Test Methods

ASTM D XXXX 

ASTM International, 2006, Annual book of ASTM Standards, Section 5, Petroleum products, 

lubricants and fossil fuels, vol. 05.05 Gaseous fuels; coal and coke: ASTM International, West 

Conshohocken, Pennsylvania, 705 p.; http://www.astm.org/

AS XXXX 

Standards Australia Limited; Sydney, NSW, 2000; http://www.standards.org.au/

BS XXXX 

BSI Group (British Standards); London, United Kingdom; http://www.bsi-global.com/en/

DIN XXXX 

DIN Detaches Institute fur Norman e. V (German Institute for Standardization); Berlin 

Germany; http://www2.din.de/index.php?lang=en 

GB XXXX 

Standardization Administration of the People's Republic of China; Beijing, China, 

Bulletin of Chinese Standards; http://www.sac.gov.cn/english/home.asp

ISO XXXXX 

International Organization for Standardization); Geneva, Switzerland; 

http://www.iso.org/iso/en/ISOOnline.frontpage

SABS XXXX 

South African Bureau of Standards, Pretoria, South Africa, https://www.sabs.co.za/index.aspx 

Organizational Contacts

AOAC International; Gaithersburg, Maryland 20877-2417 USA; http://www.aoac.org/ 

CANSPEXTM; Quality Associates International®; Douglas ON K0J 1S0CANADA; 

http://www.qai-online.com/canspex.pdf

National Institute of Standards and Technology (NIST); Gaithersburg, MD USA; 

http://www.nist.gov/ 

Canadian Certified Reference Materials Project (CCRMP), Ottawa, Ontario K1A 0G1, 

http://www.nrcan.gc.ca/mms/canmet-mtb/mmsl-lmsm/ccrmp/ccrmp-e.htm

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