NBS

PUBLICATIONS

ri_ INST. OF STAND & TECH 1!

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NBS SPECIAL PUBLICATION 260-94

S, T /

U.S. DEPARTMENT OF COMMERCE/National Bureau of Standards

Standard Reference Materials:

Methods and Procedures Used

at the National Bureau of Standards

To Certify Sulfur in Coal SRM's

for Sulfur Content, Calorific Value,

Ash Content

-QC

100

.1157

No. 20-94

1934

c, 2
Tm he National Bureau of Standards' was established by an act of Congress on March 3, 1901. The M Bureau's overall goal is to strengthen and advance the nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a

basis for the nation's physical measurement system, (2) scientific and technological services for industry and

government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau's technical work is performed by the National Measurement Laboratory, the National Engineering Laboratory, the Institute for Computer Sciences and Technology, and the Center for Materials

Science.

The National Measurement Laboratory

Provides the national system of physical and chemical measurement;

coordinates the system with measurement systems of other nations and

furnishes essential services leading to accurate and uniform physical and

chemical measurement throughout the Nation's scientific community, in- dustry, and commerce; provides advisory and research services to other Government agencies; conducts physical and chemical research; develops, produces, and distributes Standard Reference "Materials; and provides

calibration services. The Laboratory consists of the following centers:

Basic Standards2 Radiation Research Chemical Physics

Analytical Chemistry

The National Engineering Laboratory

Provides technology and technical services to the public and private sectors to address national needs and to solve national problems; conducts research in engineering and applied science in support of these efforts; builds and maintains competence in the necessary disciplines required to carry out this research and technical service; develops engineering data and measurement

capabilities; provides engineering measurement traceability services; develops

test methods and proposes engineering standards and code changes; develops and proposes new engineering practices; and develops and improves mechanisms to transfer results of its research to the ultimate user. The

Laboratory consists of the following centers:

Applied Mathematics

Electronics and Electrical Engineering2 Manufacturing Engineering

Building Technology

Fire Research Chemical Engineering2

The Institute for Computer Sciences and Technology

Conducts research and provides scientific and technical services to aid Federal agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and economy in Government

operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives; carries out this mission by managing

the Federal Information Processing Standards Program, developing Federal ADP standards guidelines, and managing Federal participation in ADP

voluntary standardization activities; provides scientific and technological advisory services and assistance to Federal agencies; and provides the technical foundation for computer-related policies of the Federal Government. The Institute consists of the following centers:

Programming Science and

Technology Computer Systems

Engineering

The Center for Materials Science

Conducts research and provides measurements, data, standards, reference

materials, quantitative understanding and other technical information funda- mental to the processing, structure, properties and performance of materials; addresses the scientific basis for new advanced materials technologies; plans

research around cross-country scientific themes such as nondestructive

evaluation and phase diagram development; oversees Bureau-wide technical programs in nuclear reactor radiation research and nondestructive evaluation; and broadly disseminates generic technical information resulting from

its programs. The Center consists of the following Divisions:

Inorganic Materials Fracture and Deformation3 Polymers

Metallurgy Reactor Radiation

'Headquarters and Laboratories at Gaithersburg, MD, unless otherwise noted; mailing address

^Gaithersburg, MD 20899.

2 Some divisions within the center are located at Boulder, CO 80303. 'Located at Boulder, CO, with some elements at Gaithersburg, MD.
Standard Reference Materials: SFSSSST

LIBRARY Methods and Procedures Used at the

National Bureau of Standards To Certify Sulfur

in Coal SRM's for Sulfur Content, Calorific Value,

Ash Content

Thomas E. Gills, Editor

Office of Standard Reference Materials National Measurement Laboratory

National Bureau of Standards

Gaithersburg, MD 20899

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director Issued December 1984
Library of Congress Catalog Card Number: 84-601148

National Bureau of Standards Special Publication 260-94

Natl. Bur. Stand. (U.S.), Spec. Publ. 260-94, 51 pages (Dec. 1984) CODEN: XNBSAV

U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1984

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402
PREFACE

As part of its congressional mandate, the National Bureau of Standards (NBS) is charged with the essential function of preparing and distributing reference materials for use in chemical analysis

and the development of methods for chemical analysis. At NBS, the Office of Standard Reference Materials brings together "state-of-the-art" measurement methods and homogeneous, stable materials

to produce Standard Reference Materials (SRM's). These SRM's' are used by laboratories around the world to calibrate instruments, to test the accuracy of new methods, and in routine programs of measurement quality assurance.

One of the most important facets of NBS SRM's is that certification is given at a stated level of accuracy. This is generally accomplished using one or more of three modes: reference methods, two or more independent methods, or interlaboratory comparison.

The Sulf ur-in-Coal SRM's are certified through measurements performed in the NBS National Measurement Laboratory. Systematic and random errors of the methods used were sufficiently well known to provide an uncertainty level for each property certified. We hope this publication of methods and procedures will help other analysts to perform measurements with accuracy comparable to those obtained during certification.

Stanley D. Rasberry, Chief Office of Standard Reference Materials
OTHER NBS PUBLICATIONS IN THIS SERIES

Catalog of NBS Standard Reference Materials

(1984-85 edition), Catherine H. Hudson, ed., NBS

Spec. Publ. 260 (February 1984). Michaelis, R. E., and Wyman, L. L. Standard

Reference Materials: Preparation of White Cast

Iron Spectrochemical Standards. NBS Misc. Publ. 260-1 (June 1964). COM74-1 1061**

Michaelis, R. E., Wyman, L. L., and Flitsch, R., Standard Reference Materials: Preparation of NBS Copper-Base Spectrochemical Standards. NBS Misc. Publ. 260-2 (October 1964). COM74-

11063**

Michaelis, R. E., Yakowitz, H., and Moore, G. A., Standard Reference Materials: Metallographic

Characterization of an NBS Spectrometric LowAlloy Steel Standard. NBS Misc. Publ. 260-3 (October 1964). COM74-1 1060** Hague, J. L. Mears, T. W., and Michaelis, R. E., Standard Reference Materials: Sources of

Information, NBS Misc. Publ. 260-4 (February

1965). COM74-1I059

Alvarez, R., and Flitsch R., Standard Reference

Materials: Accuracy of Solution X-Ray Spectrometric Analysis of Copper-Base Alloys. NBS

Misc. Publ. 260-5 (March 1965). PB168068**

Shultz, J. I., Standard Reference Materials: Methods for the Chemical Analysis of White

Cast Iron Standards, NBS Misc. Publ. 260-6

(July 1965). COM74-11068**

Bell, R. K., Standard Reference Materials: Methods for the Chemical Analysis of NBS

Copper-Base Spectrochemical Standards. NBS

Misc. Publ. 260-7 (October 1965). COM74-

11067** Richmond, M.S., Standard Reference Materials: Analysis of Uranium Concentrates at the

National Bureau of Standards. NBS Misc. Publ. 260-8 (December 1965). COM74-1 1066** Anspach, S. C, Cavallo, L. M. Garfinkel, S. B. Hutchinson, J. M. R., and Smith, C. N., Standard Reference Materials: Half Lives of Materials Used in the Preparation of Standard Reference Materials of Nineteen Radioactive Nuclides

Issued by the National Bureau of Standards NBS Misc. Publ. 260-9 (November 1965). COM74-11065**

Yakowitz, H., Vieth, D. L., Heinrich, K. F. J., and

Michaelis, R. E., Standard Reference Materials: Homogeneity Characterization of NBS Spectrometric Standards II: Cartridge Brass and LowAlloy Steel, NBS Misc. Publ. 260-10 (December

1965). COM74-11064**

Napolitano, A., and Hawkins, E. G., Standard Reference Materials: Viscosity of Standard

Lead-Silica Glass, NBS Misc. Publ. 260-11 (November 1966). NBS Misc. Publ. 260-11** Yakowitz, H., Vieth, D. L., and Michaelis, R. E., Standard Reference Materials: Homogeneity

Characterization of NBS Spectrometric Standards III: White Cast Iron and Stainless Steel Powder Compact, NBS Misc. Publ. 260-12

(September 1966). NBS Misc. Publ. 260-12**

Spijkerman, J. L., Snediker, D. K., Ruegg, F. C,

and DeVoe, J. R., Standard Reference Materials: Mossbauer Spectroscopy Standard for the Chemical Shift of Iron Compounds, NBS Misc. Publ. 260-13 (July 1967). NBS Misc. Publ.

260-13**

Menis, O., and Sterling, J. T., Standard Reference

Materials: Determination of Oxygen in Ferrous

Materials - SRM 1090, 1091, and- 1092, NBS

Misc. Publ. 260-14 (September 1966). NBS Misc.

Publ. 260-14**

Passaglia, E., and Shouse, P. J., Standard Refer- ence Materials: Recommended Method of Use

of Standard Light-Sensitive Paper for Calibrat- ing Carbon Arcs Used in Testing Textiles for Colorfastness to Light, NBS Misc. Publ. 260-15 (June 1967). (Replaced by NBS Spec. Publ.

260-41.) Yakowitz, H., Michaelis, R. E., and Vieth, D. L.,- Standard Reference Materials: Homogeneity

Characterization of NBS Spectrometric Standards IV: Preparation and Microprobe Characterization of W-20% MO Alloy Fabricated by Powder Metallurgical Methods, NBS Spec.

Publ. 260-16 (January 1969). COM74-1 1062** Catanzaro, E. J., Champion, C. E., Garner, E. L., Marinenko, G., Sappenfield, K. M., and Shields, W. R., Standard Reference Materials: Boric

Acid; Isotopic and Assay Standard Reference

Materials, NBS Spec. Publ. 260-17 (February

1970). Out of Print. Geller, S. B., Mantek, P.A., and Cleveland, N.

G., Standard Reference Materials: Calibration of NBS Secondary Standard Magnetic Tape (Computer Amplitude Reference) Using the Reference Tape Amplitude Measurement

"Process A," NBS Spec. Publ. 260-18 (November

1969). (See NBS Spec. Publ. 260-29.) Paule, R. C, and Mandel, J., Standard Reference

Materials: Analysis of Interlaboratory Measurements on the Vapor Pressure of Gold (Certifica- tion of Standard Reference Material 745). NBS

Spec. Publ. 260-19 (January 1970). PB190071**

Paule, R. C, and Mandel. J., Standard Reference

Materials: Analysis of Interlaboratory Measurements on the Vapor Pressures of Cadmium and

Silver, NBS Spec. Publ. 260-21 (January 1971). COM74-11359**

Yakowitz, H., Fiori, C. E., and Michaelis, R. E., Standard Reference Materials: Homogeneity

Characterization of Fe-3 Si Alloy, NBS Spec. Publ. 260-22 (February 1971). COM74-1 1357**

Napolitano, A., and Hawkins, E. G., Standard

Reference Materials: Viscosity of a Standard

Borosilicate Glass, NBS Spec. Publ. 260-23 (December 1970). COM71-00157**

Sappenfield, K. M., Marineko, G., and Hague, J. L., Standard Reference Materials: Comparison

of Redox Standards, NBS Spec. Publ. 260-24 (January 1972). COM72-50058**

i V
Hicho, G. E., Yakowitz, H., Rasberry, S. D., and

Michaelis, R. E., Standard Reference Materials: A Standard Reference Material Containing

Nominally Four Percent Austenite, NBS Spec.

Publ. 260-25 (February 1971). COM74-1 1356** Martin, J. F., Standard Reference Materials:

National Bureau of Standards-US Steel Corporation Joint Program for Determining Oxygen and Nitrogen in Steel, NBS Spec. Publ. 260-26

(February 1971). 85 cents* PB 81176620

Garner, E. L., Machlan, L. A., and Shields, W. R., Standard Reference Materials: Uranium

Isotopic Standard Reference Materials, NBS

Spec. Publ. 260-27 (April 1971). COM74-

11358**

Heinrich, K. F. J., Myklebust, R. L., Rasberry, S. D., and Michaelis, R. E., Standard Reference Materials: Preparation and Evaluation of SRM's 481 and 482 Gold-Silver and GoldCopper Alloys for Microanalysis, NBS Spec.

Publ. 260-28 (August 1971). COM71-50365**

Geller, S. B., Standard Reference Materials: Cali- bration of NBS Secondary Standard Magnetic Tape (Computer Amplitude Reference) Using

the Reference Tape Amplitude Measurement

"Process A-Model 2," NBS Spec. Publ. 260-29 (June 1971). COM71-50282

Gorozhanina, R. S., Freedman, A. Y., and

Shaievitch, A. B. (translated by M. C. Selby), Standard Reference Materials: Standard

Samples Issued in the USSR (A Translation from the Russian). NBS Spec. Publ. 260-30 (June

1971). COM71-50283**

Hust, J. G., and Sparks, L. L., Standard Reference

Materials: Thermal Conductivity of Electrolytic Iron SRM 734 from 4 to 300 K, NBS Spec. Publ. 260-31 (November 1971). COM71-50563**

Mavrodineanu, R., and Lazar, J. W., Standard

Reference Materials: Standard Quartz Cuvettes, for High Accuracy Spectrophotometry, NBS

Spec. Publ. 260-32 (December 1973). 55 cents* SNO03-O03-O1213-1 Wagner, H. L., Standard Reference Materials: Comparison of Original and Supplemental SRM 705, Narrow Molecular Weight Distri- bution Polystyrene, NBS Spec. Publ. 260-33 (May 1972). COM72-50526**

Sparks, L. L., and Hust, J. G., Standard Reference

Materials: Thermoelectric Voltage, NBS Spec.

Publ. 260-34, (April 1972). COM72-50371**

Sparks, L. L., and Hust, J. G., Standard Refer- ence Materials: Thermal Conductivity of

Austenitic Stainless Steel, SRM 735 from 5 to 280 K, NBS Spec. Publ. 260-35 (April 1972.) 35 cents* COM72-50368**

Cali, J. P., Mandel, J., Moore, L. J., and Young, D.

S., Standard Reference Materials: A Referee Method for the Determination of Calcium in Serum, NBS SRM 915, NBS Spec. Publ. 260-36 (May 1972). COM72-50527**

Shultz, J. I. Bell., R. K. Rains, T. C, and Menis,

O., Standard Reference Materials: Methods of Analysis of NBS Clay Standards, NBS Spec.

Publ. 260-37 (June 1972). COM72-50692**

Richmond, J. C, and Hsia, J. J., Standard Refer- ence Materials: Preparation and Calibration of Standards of Spectral Specular Reflectance, NBS Spec. Publ. 260-38 (May 1972). COM72-

50528**

Clark, A. F., Denson, V.A., Hust, J. G., and

Powell, R. L., Standard Reference Materials: The Eddy Current Decay Method for Resistivity Characterization of High-Purity Metals, NBS

Spec. Publ. 260-39 (May 1972). COM72-50529**

McAdie, H. G., Garn, P.D., and Menis, O., Standard Reference Materials: Selection of Thermal

Analysis Temperature Standards Through a Cooperative Study (SRM 758, 759, 760), NBS

Spec. Publ. 260-40 (August 1972.) COM72-

50776** Wood, L. A., and Shouse, P. J., Standard

Reference Materials: Use of Standard LightSensitive Paper for Calibrating Carbon Arcs Used in Testing Textiles for Colorfastness to Light, NBS Spec. Publ. 260^1 (August 1972) COM72-50775**

Wagner, H. L. and Verdier, P. H., eds., Standard

Reference Materials: The Characterization of Linear Polyethylene, SRM 1475, NBS Spec. Publ. 260-42 (September 1972). COM72-

50944**

Yakowitz, H., Ruff, A. W., and Michaelis, R. E., Standard Reference Materials: Preparation and Homogeneity Characterization of an Austenitic Iron-Chromium-Nicke! Alloy, NBS Spec. Publ. 260-43 (November 1972). COM73-50760**

Schooley, J. F., Soulen, R. J., Jr., and Evans, G. A.,

Jr., Standard Reference Materials: Preparation and Use of Superconductive Fixed Point

Devices, SRM 767, NBS Spec. Publ. 260-44 (December 1972). COM73-50037**

Greifer, B., Maienthal, E. J., Rains, T. C, and

Rasberry, S. D., Standard Reference Materials: Powdered Lead-Based Paint, SRM 1579, NBS

Spec. Publ. 260-45 (March 1973). COM73-

50226**

Hust, J. G., and Giarratano, P. J., Standard Refer- ence Materials: Thermal Conductivity and

Electrical Resistivity Standard Reference Materials: Austenitic Stainless Steel, SRM's 735 and

798, from 4 to 1200 K, NBS Spec. Publ. 260-46 (March 1975). SN003-003-01278-5*

Hust, J. G., Standard Reference Materials: Electrical Resistivity of Electrolytic Iron, SRM 797, and Austenitic Stainless Steel, SRM 798, from 5

to 280 K, NBS Spec. Publ. 260^7 (February

1974). COM74-50176** Mangum, B. W., and Wise, J. A., Standard Refer- ence Materials: Description and Use of Precision Thermometers for the Clinical Laboratory, SRM 933 and SRM 934, NBS Spec. Publ. 260-48 (May 1974). 60 cents* SN003-003-0 1278-5 Carpenter, B. S., and Reimer, G. M., Standard

Reference Materials: Calibrated Glass Standards for Fission Track Use, NBS Spec. Publ. 260^9 (November 1974). COM74-51185

V
Hust, J. G., and Giarratano, P. J., Standard Refer- ence Materials: Thermal Conductivity and Electrical Resistivity Standard Reference Materials:

Electrolytic Iron, SRM's 734 and 797 from 4 to 1000 K, NBS Spec. Publ. 260-50 (June 1975). $1.00* SN003-O03-0 1425-7 Mavrodineanu, R., and Baldwin, J. R., Standard

Reference Materials: Glass Filters As a Standard Reference Material for Spectrophotometry;

Selection; Preparation; Certification; Use-SRM

930, NBS Spec. Publ. 260-51 (November 1975). $1.90* SN003-003-01481-8

Hust, J. G., and Giarratano, P. J., Standard Refer- ence Materials: Thermal Conductivity and Electrical Resistivity Standard Reference Materials 730 and 799, from 4 to 3000 K, NBS Spec. Publ. 260-52 (September 1975). $1.05* SN003-003-

01464-8 Durst, R. A., Standard Reference Materials: Standardization of pH Measurements, NBS

Spec. Publ. 260-53 (December 1975, Revised). $1.05 SN003-003-01551-2

Burke, R. W., and Mavrodineanu, R., Standard

Reference Materials: Certification and Use of Acidic Potassium Dichromate Solutions as an

Ultraviolet Absorbance Standard, NBS Spec.

Publ. 260-54 (August 1977). $3.00* SN003-003-

01828-7

Ditmars, D. A., Cezairliyan, A., Ishihara, S., and

Douglas, T. B., Standard Reference Materials: Enthalpy and Heat Capacity; Molybdenum SRM 781, from 273 to 2800 K, NBS Spec. Publ. 260-55 (September 1977). $2.20* SN003-003-

01836-8

Powell, R. L., Sparks, L. L., and Hust, J. G., Standard Reference Materials: Standard

Thermocouple Materials, Pt.67: SRM 1967, NBS

Spec. Publ. 260-56 (February 1978). $2.20* SNO03-O03-0 18864

Cali, J. P. and Plebanski, T., Guide to United

States Reference Materials, NBS Spec. Publ. 260-57 (February 1978). $2.20* PB 277173

Barnes, J. D., and Martin, G. M., Standard Refer- ence Materials: Polyester Film for Oxygen Gas

Transmission Measurements SRM 1470, NBS

Spec. Publ. 260-58 (June 1979) $2.00* SN003-

003-02077 Chang, T., and Kahn, A. H. Standard Reference

Materials: Electron Paramagnetic Resonance

Intensity Standard; SRM 2601, NBS Spec.

Publ. 260-59 (August 1978) $2.30* SN003-

003-01975-5 Velapoldi, R. A., Paule, R. C, Schaffer, R., Mandel, J., and Moody, J. R., Standard Refer- ence Materials: A Reference Method for the Determination of Sodium in Serum, NBS Spec.

Publ. 260-60 (August 1978). $3.00* SN003-O03

01978-0

Verdier, P. H., and Wagner. H. L., Standard Refer- ence Materials: The Characterization of Linear Polyethylene (SRM 1482, 1483, 1484), NBS

Spec. Publ. 260-61 (December 1978). $1.70* SN003-003-02006-1

Soulen, R. J., and Dove, R. B., Standard Reference

Materials: Temperature Reference Standard

for Use Below 0.5 K (SRM 768). NBS Spec.

Publ. 260-62 (April 1979). $2.30* SN003-O03-

02047-8 Velapoldi, R. A., Paule, R. C, Schaffer, R. Mandel, J., Machlan, L. A., and Gramlich, J. W., Standard Reference Materials: A Reference Method for the Determination of Potassium in Serum. NBS Spec. Publ. 260-63 (May 1979). $3.75* SN003-O03-O2068

Velapoldi, R. A., and Mielenz, K. D., Standard

Reference Materials: A Fluorescence Standard

Reference Material Quinine Sulfate Dihydrate (SRM 936), NBS Spec. Publ. 260-64 (January

1980). $4.25* SN003-003-02 148-2 Marinenko, R. B., Heinrich, K. F. J., and Ruegg,

F. C, Standard Reference Materials: Micro- Homogeneity Studies of NBS Standard Reference

Materials, NBS Research Materials, and Other Related Samples. NBS Spec. Publ. 260-65

(September 1979). $3.50* SN003-003-021 14-1 Venable, W. H., Jr., and Eckerle, K. L., Standard

Reference Materials: Didymium Glass Filters for Calibrating the Wavelength Scale of Spectro- photometers (SRM 2009, 2010, 2013). NBS Spec.

Publ. 260-66 (October 1979). $3.50* SN003-003-

02127-0

Velapoldi, R. A., Paule, R. C, Schaffer, R., Mandel,

J., Murphy, T. J., and Gramlich, J. W., Standard

Reference Materials: A Reference Method for the Determination of Chloride in Serum, NBS Spec. Publ. 260-67 (November 1979). $3.75* SN003-

003-02136-9 Mavrodineanu, R. and Baldwin, J. R., Standard

Reference Materials: Metal-On-Quartz Filters as a Standard Reference Material for Spectrophoto- metry-SRM 2031, NBS Spec. Publ. 260-68

(April 1980). $4.25* SNO03-O03-O2 167-9 Velapoldi, R. A., Paule, R. C, Schaffer, R., Mandel, J., Machlan, L. A., Garner, E. L., and

Rains, T. C, Standard Reference Materials: A

Reference Method for the Determination of Lithium in Serum, NBS Spec. Publ. 260-69 (July)

1980). $4.25* SN003-003-02214-4 Marinenko, R. B., Biancaniello, F., Boyer, P. A., Ruff, A. W., DeRobertis, L., Standard Reference

Materials: Preparation and Characterization of an Iron-Chromium-Nickel Alloy for Microanalysis, NBS Spec. Publ. 260-70 (May 1981). $2.50* SN003-003-02328-1 Seward, R. W., and Mavrodineanu, R., Standard

Reference Materials: Summary of the Clinical Laboratory Standards Issued by the National Bureau of Standards, NBS Spec. Publ. 260-71 (November 1981). $6.50* SN003-003-02381-7

Reeder, D.J., Coxon, B., Enagonio, D., Christensen, R. G., Schaffer, R., Howell, B. F., Paule, R. C,

Mandel, J., Standard Reference Materials: SRM

900, Antiepilepsy Drug Level Assay Standard, NBS Spec. Publ. 260-72 (June 1981). $4.25* SN003-003-02329-9

vi
Interrante, C. G., and Hicho, G. E., Standard Refer- ence Materials: A Standard Reference Material Containing Nominally Fifteen Percent Austenite (SRM 486), NBS Spec. Publ. 260-73 (January

1982). $2.75* SN003-003-02386-8 Marinenko, R. B., Standard Reference Materials: Preparation and Characterization of K-411 and

K-414 Mineral Glasses for Microanalysis: SRM

470. NBS Spec. Publ. 260-74 (April 1982). $3.50 SN003-003-023-95-7

Weidner, V. R., and Hsia, J. J., Standard Reference

Materials: Preparation and Calibration of First Surface Aluminum Mirror Specular Reflectance Standards (SRM 2003a), NBS Spec. Publ. 260-75 (May 1982). $3.75 SN003-003-023-99-0

Hicho, G. E. and Eaton, E. E., Standard Reference Materials: A Standard Reference Material

Containing Nominally Five Percent Austenite (SRM 485a), NBS Spec. Publ. 260-76 (August

1982). $3.50 SN003-003-024-33-3 Furukawa, G. T., Riddle, J. L., Bigge, W. G., and

Pfieffer, E. R., Standard Reference Materials: Application of Some Metal SRM's as Thermometric Fixed Points, NBS Spec. Publ. 260-77 (August 1982). $6.00 SN003-003-024-34-1

Hicho, G. E. and Eaton, E. E., Standard Reference

Materials: Standard Reference Material Containing Nominally Thirty Percent Austenite (SRM

487), NBS Spec. Publ. 260-78 (September 1982). $3.75* SN003-003-024-35-0 Richmond, J. C, Hsia, J. J. Weidner, V. R., and

Wilmering, D. B., Standard Reference Materials: Second Surface Mirror Standards of Specular

Spectral Reflectance (SRM's 2023, 2024, 2025), NBS Spec. Publ. 260-79 (October 1982). $4.50* SN003-003-024-47-3

Schaffer, R., Mandel, J., Sun, T., Cohen, A., and

Hertz, H. S., Standard Reference Materials: Evaluation by an ID/ MS Method of the AACC

Reference Method for Serum Glucose, NBS

Spec. Publ. 260-80 (October 1982). $4.75* SN003-

003-024-43-1 Burke, R. W., and Mavrodineanu, R. (NBS retired), Standard Reference Materials: Accuracy in Analytical Spectrophotometry, NBS Spec. Publ. 260-81 (April 1983). $6.00* SN003-003-024-8

Weidner, V. R., Standard Reference Materials: White Opal Glass Diffuse Spectral Reflectance Standards for the Visible Spectrum (SRM's 2015 and 2016). NBS Spec. Publ. 260-82 (April 1983). $3.75* SN003-003-024-89-9**

Bowers, G. N., Jr., Alvarez, R., Cali, J. P. (NBS

retired), Eberhardt, K. R., Reeder, D. J., Schaffer, R., Uriano, G. A., Standard Reference

Materials: The Measurement of the Catalytic

(Activity) Concentration of Seven Enzymes in NBS Human Serum SRM 909, NBS Spec.

Publ. 260-83 (June 1983). $4.50* SN003-003-024-

99-6

Gills, T. E., Seward, R. W., Collins, R. J., and

Webster, W. C, Standard Reference Materials: Sampling, Materials Handling, Processing, and Packaging of NBS Sulfur in Coal Standard

Reference Materials, 2682, 2683, 2684, and 2685, NBS Spec. Publ. 260-84 (August 1983). $4.50* SN003-003-025-20-8

Swyt, D. A., Standard Reference Materials: A Look

at Techniques for the Dimensional Calibration of Standard Microscopic Particles, NBS Spec. Publ. 260-85 (September 1983). $5.50* SN003-003-

025-21-6 Hicho, G. E. and Eaton, E. E., Standard Reference Materials: A Standard Reference Material

Containing Two and One-Half Percent Austenite, SRM 488, NBS Spec. Publ. 260-86 (December

1983). $1.75* SN003-003-025-41-I Mangum, B. W., Standard Reference Materials: SRM 1969: Rubidium Triple-Point - A Temperature Reference Standard Near 39.30 °C, NBS

Spec. Publ. 260-87 (December 1983). $2.25* SN003-003-025-44-5 Gladney, E. S., Burns, C. E., Perrin, D. R., Roelandts, I., and Gills, T. E., Standard Reference Materials: 1982 Compilation of Elemental

Concentration Data for NBS Biological, Geological, and Evironmental Standard Reference

Materials. Spec. Publ. 260-88 (March 1984). SN003-003-02565-8

Hust, J. G., Standard Reference Materials: A Fine- Grained, Isotropic Graphite for Use as NBS

Thermophysical Property RM's from 5 to 2500 K, NBS Spec. Publ. 260-89 (September 1984). Hust, J. G., and Lankford, A. B., Standard Reference Materials: Update of Thermal

Conductivity and Electrical Resistivity of

Electrolytic Iron, Tungsten, and Stainless Steel, NBS Spec. Publ. 260-90 (September 1984) Goodrich, L. F., Vecchia, D. F., Pittman, E. S., Ekin, J. W., and Clark, A. F., Standard Reference

Materials: Critical Current Measurements on an NbTi Superconducting Wire Standard Reference

Material, NBS Spec. Publ. 260-91 (September

1984). Carpenter, B. S., Standard Reference Materials: Calibrated Glass Standards for Fission Track Use (Supplement to NBS Spec. Publ. 260-49). NBS

Spec. Publ. 260-92 (September 1984). Ehrstein, J., Preparation and Certification of Standard Reference Materials for Calibration of Spreading Resistance Probes, NBS Spec. Publ. 260-93 (In Press).

Gills, T. E., Koch, W. F., Stolz, J. W., Kelly, W. R., Paulsen, P. J., Colbert, J. C, Kirklin, D. R., Pei, P.T.S., Weeks, S., Lindstrom, R. M., Fleming, R. F., Greenberg, R. R., and

Paule, R. C, Methods and Procedures Used at the National Bureau of Standards to Certify Sulfur

in Coal SRM's for Sulfur Content, Calorific Value, Ash Content, NBS Spec. Publ. 260-94

(In Press).

* Send order with remittance to Superintendent

of Documents, US Government Printing Office Washington, DC 20402. Remittance from

foreign countries should include an additional one-fourth of the purchase price for postage. ** May be ordered from: National Technical Information Services (NTIS). Springfield

Virginia 22161.

vi i
TABLE OF CONTENTS

Page Certificate SRM's 2682, 2683, 2684, 2685 - Sulfur in Coal ix Abstract xiii

Introduction by T. E. Gills xiv

I. Determination of Sulfur in NBS Coals by Ion Chromatography

W. F. Koch and J. W. Stolz 1

II. Determination of Sulfur in NBS Coals by Isotope Dilution Thermal Ionization

Mass Spectrometry

W. R. Kelly and P J. Paulsen 7 III. Determination of Sulfur, Calorific Value, and Ash Content in NBS Coals Using ASTM Procedures D2015, D3180, D3177, D3173, and D3174

J. C. Colbert and D. R. Kirklin 14

IV. Determination of Sulfur in NBS Coals by a Modified High Temperature Method

(D1552)

P. T. S. Pei and S. Weeks 20

V. Determination of Sulfur and Major Inorganic Constituents by Neutron-Capture

Prompt - Activation Analysis - H, B, C, N, Al and S R. M. Lindstrom 22

VI. Determination of Minor Inorganic Constituents by Neutron Activation Analysis

- Ca, CI, K, Mg, Mn, Na, Ti , and V

R. F. Fleming 26 VII. Multielement Analysis of NBS Coals by Instrumental Neutron Activation

Analysis

R. R. Greenberg 32 VIII. Statistical Analysis and Certification of NBS Sulfur in Coal SRM's

R. C. Paule 35

viii
S. Department of Commerce

Malcolm Baldnge

Secretary

National B.h«* of Standards

Ernest Ambler. Director Rational ^ntmn of js»iandardg

Certificate af (Analysis

Standard Reference Materials

2682, 2683, 2684 and 2685

Sulfur in Coal

These Standard Reference Materials (SRM's) are intended primarily for use as analytical standards for the determination of sulfur in coal. In addition to sulfur they are certified for their calorific value (MJ Kg ) and ash content. SRM's

2682-2685 each consists of a 50-g bottle of a different coal composition. Each material was ground to pass a 60-mesh

sieve and homogenized. The certification of the materials for sulfur is based on at least a 250-mg sample of the dried

material, the minimum amount that should be used for analysis (see drying instructions). The calorific values were

determined by procedures recommended in standard ASTM methods (see references in Table 1). The certification data

for the lour different coals are given in Table 1 along with methods used for certification. Noncertified values for major

and minor elements are given in Table 2. These values are provided for information only. Notice to Users : These SRM's are sold individually rather than in sets; however, only one Certificate of Analysis is provided. Therefore, the user must be careful to use the data specific to the SRM being used. The uncertainty of a certified value is expressed as two times the standard error and includes observed variability within and between measurement methods and any observed material heterogeneity. For the certified heating values the uncertainty also includes additional allowances for possible limited sample degradation due to aging or normal

oxidation.

Certification analyses were performed by W.R. Kelly, W.F. Koch, P.J. Paulsen, and J.W. Stolz of the Inorganic

Analytical Research Division and J.C. Colbert and D.R. Kirklin of the Chemical Thermodynamics Division. Analyses for supplemental information were performed in the Inorganic Analytical Research Division by R. Fleming,

R. Greenberg, and R.M Lindstrom. The statistical analysis of the certification data was performed by R.C. Paule of the National Measurement Laboratory. The overall direction and coordination of the technical measurements leading to certification were performed under the chairmanship ol E L. Garner, Chief of the Inorganic Analytical Research Division. The technical and support aspects involved in the preparation, certification, and issuance of these Standard Reference

Materials were coordinated through the Office of Standard Reference Materials by T.E. Gills.

I ehi uai} 7. |9K3 George A. Uriano, Chief

(ReNision ol Ccrtilicute (over) Office of Standard Reference Materials ihued 12-14-82)

ix
Table 1 Certified Values for SRM's 2682, 2683, 2684, and 2685 SRM Coal Sulfur''

2,3 Furnace HHV25 '- No. Type Wt. % Ash Wt. % MJ-Kg ' (BTU Ib ')

2682 Sub-bituminous 0.47 ±0.03 6.37 ±0.18 27.45 ±0.56(1 f800± 240) 2683 Bituminous 1.85 ±0.06 6.85 ±0.02 32.70 ± 0. 14 ( 14060 ± 60) 2684 Bituminous 3.00 ±0.1

1 1.09 ±0. 18 29.68 ±0.47 (12760 ± 200) 2685 Bituminous 4.62 ±0.18 16.53 ±0.15 28.15 ±0.42(12100± 180)

'ASTM D3 177 Standard Test Method for Tot al Sulfur in the Analysi:i Sample of Coal and Coke

"Ion Chromatography with Bomb Combustion

Thermal Ionization Mass Spectrometry. Sealed Glass Tube Digestion

4 AS I M D3I74, Standard lest Method for Ash in the Analysis Sample of Coal and Coke AS I M D2UI5 Standard lest Method lor Gross Calorific Value of Solid Fuel by the Adiabatic Bomb Calorimeter

''AS I M 1)3 1 80 Standard lest Method lor Calculating Coal and Coke Analyses from As-Determined to Different Bases HHV2-(Higher Heating Value - Moisture Free) Note I he calorific values ( MJ- Kg ' ) may decrease upon the aging or normal oxidation of the coals. NBS will continue to monitor these calorific values and report an> substantive change to the purchaser. The uncertainty of the healing value includes an additional allowance of 0. 12 MJ Kg for possible sample degradation. I he reference date for the calorific data is October 1982.

PREPARATION AND TESTING

Approximately one ton of coal was obtained from each of four different coal mine locations. All coals were oven dried

prior to processing in accordance with procedures outlined in ASTM D2013. At least 1000 pounds of each of the four

coals were reduced in size to -60 mesh and screened prior to blending. Each of the -60 mesh coals was blended in a stainless steel cone blender (approximate capacity 0.85 cubic meter). The coals were then packaged into individual 50-g

bottled units. Homogeneity testing was done on the bulk materials and 50-g bottled units. The homogeneity analyses were performed using x-ray fluorescence analysis. Replicate analyses indicated the material variability for sulfur to be

within ± 2% (relative) for all four SRM's. The homogeneity studies were performed by T.E. Gills and M. Watson of the Office of Standard Reference Materials and P. A. Pella of the Gas and Particulate Science Division.

X
ANALYSIS

Sulfur: The certified sulfur content is based upon the results of 3 independent methods of analysis: ion chromatography,

gravimetry, and thermal ionization mass spectrometry. Agreement with the certified values was found using 2 additional independent techniques, prompt-gamma activation analysis and a combustion 1R technique.

Calorific Value (MJ Kg ')and Ash Content: The certified values for the calorific values and ash contents were

determined using measurements made in an adiabatic bomb calorimeter of the type used in commercial laboratories. This calorimeter is capable of reproducing determinations on benzoic acid to a precision of 0.07% (relative). This state- ment of precision was arrived at by averaging 5 calibrations made on the calorimeter using a benzoic acid standard that

is traceable to the NBS SRM 39i, Benzoic Acid. Major and Minor Elements: Analyses for major and minor elements were performed by thermal neutron activation

analysis and neutron capture gamma-ray activation analysis. These values are not certified but are to be used for information only. STABILITY

The long-term physical and chemical stability of these SRM's has not been rigorously established. However, NBS

recommends that the material be stored in the tightly sealed bottle away from sunlight and intense sources of radiation. NBS will continue to monitor these materials and any substantive change in their certification will be reported to the

purchaser. INSTRUCTIONS FOR DRYING

The certification of sulfur in these SRM's is based upon a properly dried sample. The recommended procedures for drying are vacuum drying at ambient temperature for 24 hours or oven drying for 24 hours at 105 °C. Typical moisture

loss using the recommended methods for drying are the following: SRM 2682, 18%; SRM 2683, 1.4%; SRM 2684, 3.6%; and SRM 2685, 1.8%. SUPPLEMENTAL INFORMATION

The values listed below are based on measurements made using a single method or technique and are given for information only. While no reason exists to suspect systematic bias in these numbers, no attempt was made to determine if such

bias attributable to the methods exists. The analyses of SRM's 2682-2685 for major and minor elements were made using NBS SRM's 1632a and 1635, Trace Elements in Coal, as controls.

xi
Table 2 Inorganic Constituents in SRM's 2682, 2683, 2684, and 2685 Mean Concentrations (/ug/g) Unless Noted

Element/SRM 2682 2683 2684 2685 Al % 0.46 0.86 1.1 1.7 As 1.0 3.6 3.9 12 B 39 67 114 109 Ba 382 71 41 105 Br 3.7 17 11 5.6 C % 75 79 68 66 Ca % 1.1 0.20 0.44 0.52 Ce 10 9 12 18 Co 1.7 2.2 3.9 4.6 Cr 15 11 17 22 Cs <0.1 0.4 1.2 1.3 Eu 0.17 0.18 0.23 0.36 Fe % 0.24 0.76 1.5 2.9 H % 4.7 5.0 4.8 4.6 HI 0.60 0.42 0.57 0.91 K % 0.01 0.08 0.20 0.26 La 5.2 5.! 6.7 10 Mg % 0.2 0.05 0.08 0.1 Mn 26 13 36 41 N % 0.8 1.6 1.6 1.1 Na % 0.10 0.05 0.03 0.08 Rb <2 5.3 15 17 Sb 0.19 0.28 0.35 0.36 Sc 1.5 1.9 2.7 3.7 Se 0.91 1.2 1.9 1.9 Sm 0.78 0.86 1.1 1.7 Th 1.5 1.4 2.0 2.7

1 1 % 0.05 0.04 0.06 0.09 U 0.52 0.42 0.90 0.95 V 15 14 22 31 w 1.8 0.48 0.56 1.2 Zn 8.6 9.5 110 17
METHODS AND PROCEDURES USED AT THE NATIONAL BUREAU OF STANDARDS TO CERTIFY SULFUR IN COAL SRM'S FOR SULFUR

CONTENT, CALORIFIC VALUE, ASH CONTENT

Thomas E. Gills, Editor National Bureau of Standards Gaithersburg, MD 20899

ABSTRACT

This Special Publication consists of a collection of analytical methods used at NBS for the determination of total sulfur, calorific value, and ash content in four different coals, SRM's 2682,

2683, 2684, and 2685, with nominal sulfur contents of 0.5, 2.0, 3.0, and 4.5 percent, respectively.

Also, included are descriptions of methods and procedures used for providing noncertified values for approximately 30 elements including carbon, hydrogen, and nitrogen. These procedures were selected

and often specifically developed, by the scientific staff members of NBS, to provide measurements

with the best obtainable accuracy and precision.

The materials for these SRM's were obtained and processed by Valley Forge Laboratories under a grant from the National Bureau of Standards. Material preparation of the four coal SRM's is described in NBS Special Publication 260-84, "Sampling, Materials Handling, Processing, and Packaging of Standard Reference Coal Materials."

Key Words: analytical procedures; coal analysis; gravimetry; ion chromatography; isotope dilution

thermal ionization mass spectrometry; prompt gamma activation analysis; sample preparation; thermal neutron activation analysis.

DISCLAIMER

In order to describe adequately materials and experimental procedures discussed in this work, it was occasionally necessary to identify commercial products by manufacturer's name or label. In no instance does such identification imply endorsement by NBS of the particular product or equipment as being best available for that purpose.

xiii
INTRODUCTION

Recently, there have been some important developments in coal utilization technology in the areas of coal liquefaction, coal gasification, and advanced methods of coal combustion to generate electric

power. Equally important, the combustion of coal produces an ash which may offer an economical raw material for resource recovery. The problems associated with these activities, i.e., environmental

pollution, have mandated new approaches to produce more efficient and cleaner coal combustion

technologies. In response to these newer technologies, new techniques and methods have emerged to serve as moniters of the coal composition, combustion processes, and coal combustion by-products.

As part of its environmental and energy standards program, NBS has produced a series of four new coal SRM's, 2682, 2683, 2684, and 2685, certified for sulfur content, heating value and ash content. Additionally, noncertified values, for information only, were determined for approximately 30 elements and/or constituents. These materials are intended primarily for use as analytical

standards to evaluate methods and procedures used in routine coal analyses.

This Special Publication is a collection of the analytical methods used at NBS to certify and analyze these SRM's. These methods include: ion chromatography, isotope dilution thermal ionization mass spectrometry, neutron capture prompt-gamma activation analysis, thermal neutron activation analysis and ASTM methods for coal analyses, D2015, D3180, D3177, D3173, D3174, and D1552. The certified values are based on the use of two or more of these independent methods of analysis or an ASTM reference method. The noncertified values are based on a single method of analysis and are provided for information only. The materials for these SRM's were procured and processed as part of a grant to Valley Forge Laboratories and Webster and Associates. The details of the collection processing and preparation

of the base materials for these SRM's are documented in NBS Special Publication 260-84 "Sampling, Materials Handling, Processing, and Packaging of NBS Sulfur in Coal Standard Reference Materials."

The analytical methods described in this publication are believed to provide the best measuring

capabilities available at this time. However, they will be reviewed periodically and the certified values updated as a part of the NBS update certification program.

xiv
SECTION I Determination of Sulfur in NBS Coals by Ion Chromatography

W. F. Koch and J. W. Stolz

Six bottles of each of four levels of coal (SRM's 2682-5) were analyzed for sulfur content by ion chromatography. Single analyses were done on two bottles and duplicate analyses were carried out on the remaining four bottles. The sequence of analysis was randomized; however, each level used the identical sequence. The order of analysis is indicated in Tables 1-4. SRM's 1635 and 1632a, Trace Elements in Coal, were run as controls. In addition, an alternate drying procedure was investigated

on four bottles at each level. Drying: Samples were dried for 24 hours in a vacuum drying oven at 23 °C, final pressure 15 microns. A liquid nitrogen cold trap was between the pump and the oven. The alternate procedure

was to dry at 105 °C at atmospheric pressure. Combustion : Samples of 250 mg were combusted in a high-pressure oxygen calorimetric "bomb (30 atm.

0„, 20 mL H„0 scrubber) and then diluted with a carbonate buffer solution. Quantitative transfer of the sample from the bomb was not required.

Ion Chromatography : After dilution, the samples were injected into the ion chromatograph through a 0.2 micron syringe filter. SRM's 2682-4 were analyzed using standard anion separator columns; SRM 2685 was analyzed on new fast-run columns. The following conditions were employed: eluent, 3 mmol/L NaHCO and 2 mmol/L ^200^5 flow rate 2.5-3 mL/min.; suppressor column regenerated with

H^SO^. Calibrant-solutions were prepared from coulometrically standardized sulfuric acid. For each level, three calibrants were prepared which bracketed the concentration of sulfate in the combusted

and diluted samples. Quantitation was by interpolation of the calibration curve, peak height versus concentration. Calibration sets were run before every second sample. Each sample was injected twice in alternate calibration sets. Results : The results are detailed in Tables 1-5 and summarized in Table 6. Vacuum drying and drying at 105 °C can be used without changing the value of the sulfur content.

1
Table 1 Sulfur in Coal, SRM 2682 by Ion Chromatography

A

C

Sample # Weight Loss

% Sulfur

Wt. %

1227-1 18.9 0.466

410-1 15.3 0.465 1227-2 19.0 0.468

1500 19.0 0.474

398 19.1 0.457 410-2 14.5 0.472

241-1 18.8 0.450

809-1 19.1 0.470

241-2 19.1 0.478 809-2 19.2 0.469 Mean = 18.2 0.467

Std. Dev.* = 1.8 0.008

1635-1 10.6 0.326 1635-2 20.3 0.349

1227-3 18.8 0.473 1227-4 18.9 0.466 410-3 14.8 0.468 809-3 18.8 0.456 Mean = 17.8 0.466

Std. Dev.* = 2.0 0.007

A - Dried in vacuum oven, 23 °C

B - Controls, SRM 1635

C - Dried at 105 °C *Standard Deviation for a single measurement
Table 2 Sulfur in Coal, SRM 2683 by Ion Chromatography

Sample # Weight Loss% Sulfur

Wt. %

1227-1 410-1 1227-2

1500 398 410-2

241-1 809-1

241-2 809-2

1.82

1.84 1.90

1.90

1.85

1.90

1.85 1.82

1.89 1.86 Mean

Std. Dev.*

1.86 0.03

1632a-l 1632a-2

1632a-3

1632a-4

1.56

1.59 1.58

1.59

1227-3 1227-4 410-3

809-3

1.874

1.873

1.870

1.872 Mean = 1.24 Std. Dev.* = 0.29 1.872 0.002

A - Dried in vacuum oven, 23 C

B - Controls, SRM 1632a

C - Dried at 105 °C *Standard Deviation for a single measurement

3
Table 3 Sulfur in Coal, SRM 2684

by Ion Chromatography

Sample // Weight Loss

% Sulfur

Wt. %

1227-1 410-1 1227-2

1500

398 410-2

241-1 809-1 241-2

809-2

4.20

3.77 4.06

3.98 3.40

3.82

2.93 3.64 3.00

3.59

3.05

3.06

3.03

3.10

3.05

3.03 3.03

3.04 3.02

3.03 Mean = 3.64

Std. Dev.* = 0.43

3.04 0.02

1632a-5

1632a-6

1.91 2.001.58

1.56

1227-3

1227-4 410-3

809-3

2.98 3.03

3.06 3.05 Mean = 3.35 Dev.* = 0.22

3.03

0.04

A - Dried in vacuum oven, 23 C

B - Controls, SRM 1632a

C - Dried at 105 °C *Standard Deviation for a single measurement

4
Table 4 Sulfur in Coal, SRM 2685 by Ion Chromatography

Weight Loss Sulfur

% Wt. %

1227-1 410-1 1227-2

1500 398 410-2

241-1 809-1

241-2 809-2 Mean = 1.82 Std. Dev.* = 0.10

1632a-7 2.06 1632a-8 2.00

C 1227-3 1227-4 1.31 410-3 1.17 809-3 1.1 1 Mean = 1.20

Std. Dev* = 0.10

A - Dried in vacuum oven, 23 °C

B - Controls, SRM 1632a

C - Dried at 105 °C *Standard Deviation for a single measurement

5
Table 5 Sulfur in Coal, Control Standards Sulfur

SRM # Wt. %

1635-1 0.326

1635-2 0.349 Mean = 0.338 Certified Value = 0.33 + 0.03

1632a-l 1.56 1632a-2 1.59 1632a-3** 1.58 1632a-4** 1.58 1632a-5 1.58 1632a-6 1.56 1632a-7 1.57 1632a-8 1.57 Mean = 1.57 Std. Dev.* = 0.01 Certified Value = 1.58 + 0.04

^Standard Deviation for a single measurement

** - Dried at 105 °C for 2 hours. All others were dried at 23 C in a vacuum oven (P < 50 microns )

.

Table 6 Summary of Sulfur in Coal by Ion Chromatography

SRM # Sulfur Vacuum

, Wt. % Drying n Sulfur, Wt. % 105 °C Drying n

2682 0.467 + 0.008* 10 0.466 + 0.007* 4 2683 1.86 + 0.03* 10 1.872 + 0.002* 4 2684 3.04 + 0.02* 10 3.03 + 0.04* 4 2685 4.65 + 0.06* 10 4.62 + 0.01* 4

* Standard deviation of a single measurement

6
SECTION II Determination of Sulfur in NBS Coals by Isotope Dilution Thermal Ionization Mass Spectrometry

W. R. Kelly and P. J. Paulsen

Sulfur was determined in four different NBS coal SRM's by isotope dilution thermal ionization mass spectrometry. In this+

procedure the relative sulfur isotopic abundances were measured as the thermally produced AsS molecular ion. This technique is capable of measuring sulfur over a wide concentration range in a variety of matrices with relative measurement precisions of 0.1 percent

(Is). The application of this technique to the determination of Sulfur in Coal SRM's is presented. Additional information is given in papers by Paulsen and Kelly [1] and Kelly and Paulsen [2]. Experimental Procedure

Sample Preparation and Dissolution

For each SRM approximately 0.7 g of coal from six different bottles were placed in weighing bottles

for drying. In the case of SRM 2682, which has a high moisture content, the material in the weighing bottles was pre-dried in a desiccator over MgCClO^^ for 46 hours at room temperature. The weight losses ranged from 14.9-16.3 percent. All samples were then dried in two groups at room temperature: (1) SRM's 2682, 2683, and (2) SRM's 2684, 2685. After 24 hours of pumping, the pressure in the vacuum oven, as measured by a thermocouple, was 14 microns Hg for the first group

and 10 microns Hg for the second group. The weight losses for each sample are given in Tables 2-6. Weighed samples of about 0.1-0.2 g of dried

<j£ al were transferred to modified Carius tubes using a glass transfer boat. Approximately 1 yg of S enriched tracer per 3 yg natural S was added by weight to each sample followed by 10 g of HNO^ and 4g HC1. The acids and water used in these procedures were produced at NBS by subboiling distillation [3] unless otherwise noted. The tubes were cooled immediately to -78 °C in a C0

2-CC1^-CHC1

3 slush and sealed with a gas-oxygen torch. Each sealed tube along with 25 g of solid CO^ was placed in a steel shell equipped with a threaded

cap. The shells were sealed and placed in an oven at 240 °C for 24 hours. This process completely

dissolved the organic fraction of the coal and oxidized all S to sulfate which insures equilibration

of tracer and natural sulfur isotopes. After the steel shells were cooled to room temperature, the Carius tubes were removed and placed behind an explosion shield. The Carius tubes were cooled again

to -78 C and the neck heated with a torch until a small vent blew open and released the internal pressure. Each tube was scored 5 cm below the shoulder and fire opened. The samples were

transferred to 50 mL beakers, covered with watch glasses, placed on a hotplate under a glass dome (3 L volume), which was continuously purged with dry N^ (2 L/min), and evaporated to dryness. Two mL

of HC1 were added to rinse the side of each beaker and the samples were heated to dryness. The last

step was repeated twice using 1 mL HC1 each time. The repeated additions of HC1 destroy all nitrates which would interfere with the reduction step. The dried sample was dissolved in 5 mL HC1.

Reduction of Sulfate to H S and Precipitation as As,,S

3 The sulfur in each sample was reduced to H^S using hypophosphorous acid as the reducing agent. A master reducing solution was made from a mixture of ACS Reagent Grade H„P0„ (61 mL), HC1 (205 mL)

,

and HI (125 mL) [1]. Twenty-five mL of the master solution was added to each reduction flask and refluxed at 120 °C for 45 min. After the solution cooled to room temperature, the dissolved samples were added and refluxed for 45 min. The ^S formed was flushed from the flask and passed through a 5 mL distilled water trap and+

was then trapped in a 15 mL centrifuge tub_^ containing 1 mL aqueous ammonia solution

and 1000 yg As . During the collection step the NH -As solution was cooled in an ice bath to retard the loss of NH^. The trapped S was precipitated as As^S^ by the dropwise addition of HC1 to the solution. The precipitate was centrifuged for 10 min to insure that all particles of As,^ were

removed from the solution. The supernate, which contained a large amount of dissolved NH^Cl, was removed with a pipet. The As

2 S 3 was washed 5 times with 5 mL portions of distilled water. The washed -A^S^ was dissolved in an As-NH^ solution to a S concentration of 100 yg S/mL and an As/S atom ratio of 2. This solution was used for the ratio measurement by mass spectrometry.

7
Mass Spectrometry

Sample loading was performed in a plastic box flushed with to prevent sulfur contamination from ambient air. About 1.5 y g S and about 100 u g silica gel were added to a rhenium flat filament and AsS ions were thermally ionized at 950 C. The zone refined rhenium filaments were outgassed at 1500 °C at 10 ^ torr for 1/2 hour and stored overnight before use. The silica gel was prepared from high purity quartz that was fused with

Na

2 C°3 an<* wasneci repeatedly with quartz distilled water. A mixture of silica gel and H^PO^ was prepared, which contained 20 mg silica gel/mL of 0.4M HoPO^. This mixture was neutralized with high

purity NH^. The H^PO^ was prepared from high purity ?2 5 anc* (

l uartz distilled water.

A detailed description of the sample loading and mass spect rometric measurement procedure is given

below. The silica gel-tLPO^ solution is shaken vigorously to disperse the silica gel and 1 cm (5H

L) is drawn into a 5 cm length of intermedic tubing and placed in the center of the filament. A current of 0.9 A is passed through the filament until the silica gel is dry and then heated an additional 15 sec. A 3 cm length (equivalent to 1.5 yg S) of the sample solution is drawn into the tubing and added as single drops to the dried silica gel. After the first drop is added the filament current is adjusted to 1.5 A. The silica gel will break, up and disperse' within the sample

drop. The remainder of the sample is added without allowing the solution on the filament to evaporate to dryness between additions. After the sample is dry^ it is heated for 15 sec. The current is increased and the sample dried at approximately 700 C for 5 sec. No fumes are observed during this final heating step. If excess H^PO^ is present and fumes of ?2®$ are observed, it causes decomposition of As2S^ and the loss or sulfur as H^S. For this reason the silica gel and H PO, were preraixed (neutralized with NH^) in a ratio designed to maximize both signal intensity and stability while avoiding excess amounts of H^PO^. The sample is loaded into the mass spectrometer with a total exposure to room atmosphere of two minutes or less. Heating of the filament is started when the pressure drops below 2 x 10 torr. A liquid N~ cold finger is used to reduce the^ pressure in the source. The filament is initially heated to 800 °C which typically gives a AsS beam of 2 to 5 volts with a 10"'fl feedback resistor.

At this temperature the signal is decaying rapidly. The filament temperature is increased to 950 °C in 50 °C increments at 5 min. intervals. The source is focused for maximum intensity after each temperature adjustment. The ion current at 950 °C is stable and normally in the 10V range. Larger

ion currents can be obtained above 950 °C but they are unstable. The signal increases and then decays after each temperature increase. Data collection commences at 30 min. The major isotope is either on the 10V or 3V scale and decaying at a moderate rate (5%/min.). Three data sets are collected. Each data set consists of 6 integrations of the mass 107 current and 5 integrations of the mass 109 current using an integration time of 15 sec. Delay times of 14 sec and 10 sec are used for ratios of 20/1 and 1/1, respectively. Background signals and electronic offsets are read before

each set. Typical precision for a single set is 0.05 percent (Is). During the 21 minutes of data collection, the observed decrease in the 107/109 ratio as a result of isotopic fractionation is less than 0.1 percent. Results and Discussion

Isotope dilution is based upon the equilibration of a known amount of enriched isotope with the isotopes of the element being determined and the measurement of the isotopic, ratio of the resulting mixture. Sulfur has four stable isotopes with the following abundances: S 95 percent, S 0.75 percent, S 4.2 percent, and S 0.02 percent, ^sing^ sulfur enriched in S as the tracer, the most precise data are obtained by measuring the S/ S ratio. The measured ratio in the mixture is given by the following equation:

(1)

Equation (1) can be rearranged

(32

s) =(

34

s) \ /sample \ /tracer
It is obvious from equation (2) that to determine the moles of S in the sample, only ratios need

be measured and, therefore, the accuracy of an isotope dilution determination is independent of chemical yields provided blanks are relatively small. The concentration of sulfur in a sample is given by the following relation:

ug of S/j ( 32

S) (at.wt)

( 32A) (wt). x 10 (3)

where the numerator equals the moles of S times the atomic weight of sulfur and the denominator

equals the fractional abundance of S ( A) in the sample times the sample weight in grams. For the vast majority of elements the isotopic composition is invariant in nature. However, sulfur

is one of the few elements which exhibits variability in nature as a result of isotopic fractionation during biological processing by certain types of bacteria [4]. Therefore, the isotopic composition of the sulfur in all samples was measured on unspiked samples to preclude bias from this effect which could be 1 percent or larger if average isotopic abundance values were

assumed. Calibration of 34

S Enriched Tracer

The accuracy of an isotope dilution determination can be no better than the^accuracy of the tracer concentration. Therefore, considerable effort was made to insure that the S enriched tracer solution was accurately calibrated. The S tracer used in this study was obtained from Oak Ridge National Laboratory in the form of elemental sulfur. It was converted to sulfate in HNO^-H^l and diluted to an approximate concentration of 300 yg total sulfur per gram of solution. The S tracer

was calibrated against gravimetrically prepared solutions of high purity ^SO^ and Na2S0. plus three different lots of coulometrically assayed sulfuric acid solutions. All five of these solutions

showed measurable differences in their sulfur isotopic compositions. An accurately weighed portion

of a natural solution and S enriched tracer solution were added to a Teflon beaker, mixed thoroughly, and added directly to the reduction flask. Blanks were determined concurrently with the calibration mixtures and resulted in corrections of less than 0.02 percent relative in all cases. The results of ten calibration mixes are given in Table 1. There is good agreement between the six sulfuric acid mixes and the four salt mixes. The high precision of the mean of all ten mixes reflected in the 0.14 percent relative standard deviation demonstrates the high precision

capabilities of this technique. Results

The sulfur concentrations in the five SRM coals, as determined by isotope dilution thermal ionization mass spectrometry, are given in Tables 2-6. The sulfur concentrations listed in the tables are a single determination from one bottle of the SRM. The standard deviation was computed from the individual determinations. The blank uncertainty was negligible for all samples.

References

1. Paulsen, P. J., and Kelly, W. R. , Determination of Sulfur by Isotope Dilution Thermal Ionization

Mass Spectrometry as AsS+

Ions, Anal. Chem. 56, 708-713 (1984).

2. Kelly, W. R. and Paulsen, P. J., Precise Determination of Sulfur at High Concentrations by Isotope Dilution Thermal Ionization Mass Spectrometry, submitted to Talanta.

3. Kuehner, E. C. ; Alvarez, R. ; Paulsen, P. J.; and Murphy, T. J.; Production and Analysis of High

Purity Acids Purified by Sub-boiling Distillation. Anal. Chem. _44; 2050-2056 (1972).

4. Krouse, H. R. , Sulfur Isotopes in our Environment, in Handbook of Environmental Isotope Geochemistry, P. Fritz and J. Ch. Fontes, eds., Elsevier, 435-471 (1980).

9
Table 1 34 Calibration of S Enriched Spike Solution

Concentration Determined

Natural Sulfur in Tracer ug S/g a

H

2 S0

4-135b Mix #1 313.47 Mix #2 313.63

H

2 S0

4 -137 b Mix #1 313.60

Mix #2 313.39

H o S0.-139b

2 4Mix #1 314.30 Mix #2 314.26 Mean of 6 acids 313.78 + 0.40 (Is)

Mix #1 313.98

Mix #2 312.88

Mix #1 313.27 Mix #2 313.73 Mean of 4 salts 313.47 + 0.49 (Is) Grand mean of 10 measurements 313.65 + 0.44 (Is)

a Total yg of S per gram of solution.

b The three h So^ acid natural solutions were prepared from three different lots of acids.

10
Table 2 Sulfur Concentration in SRM 2682, Coal, as Determined by Thermal Ionization Mass Spectrometry

OSRM Weight Loss Dry Sample Bottle // (%) Weight (g) S% 1453 18.85 0.15805 0.4908

156 18.88 0.16186 0.4897

394 18.40 0.22883 0.4924

510 18.61 0.21871 0.4952

899 17.71 0.20537 0.4934

1178 18.77 0.15608 0.4992 Mean = 0.4935

St. Dev* = 0.0034 Standard Deviation of single measurement

Table 3 Sulfur Concentration in SRM 2683, Coal,

as Determined by Thermal Ionization Mass Spectrometry

OSRM

Bottle # Weight Loss

(%) Dry Sample Weight (g) S% 121 1.29 0.13593 1.877 133 1.56 0.13511 1.907

529 1.58 0.16290 1.895 900 1.37 0.11518 1.897 1033 0.943 0.11492 1.889 1178 1.52 0.12194 1.911 Mean = 1.896

Std. Dev* = 0.012 Standard Deviation of single measurement

11
Table 4 Sulfur Concentration in SRM 2684, Coal, as Determined by Thermal Ionization Mass Spectrometry

Bottle # Weight Loss

(%) Dry Sample Weight (g) S% 481 3.29 0.10161 3.109 492 3.70 0.10821 3.074 816 3.75 0.10555 3.108

1178 3.72 0.10903 3.076

1260 3.13 0.10321 3.062

1475 3.50 0.13460 3.026 Mean = 3.076

Std. Dev* = 0.031

* Standard Deviation of single measurement

Table 5 Sulfur Concentration in SRM 2685, Coal, as Determined by Thermal Ionization Mass Spectrometry

OSRM

Bottle # Weight loss

(%) Dry Sample Weight (g) S% 498 1.79 0.11576 4.853

504 1.78 0.09934 4.811

505 1.75 0.11391 4.762

848 1.70 0.11119 4.670

1178 1.79 0.12793 4.764

1452 1.64 0.11427 4.703 Mean = 4.761

Std. Dev. = 0.067

* Standard Deviation of single measurement

12
Sulfur Concentration in SRM 1635, Coal,

as Determined by Thermal Ionization Mass Spectrometry

Weight Loss Dry Sample Sample » (%) Weight (g) S%

1 18.80 0.16489 0.3576

2 18.80 0.10232 0.3525

3 18.80 0.17319 0.3530 Mean = 0.3544

Std. Dev.* = 0.0028 Standard Deviation of single measurement

Certified Value = 0.33 + 0.03

13
SECTION III

Determination of Sulfur, Calorific Value and Ash Content in NBS Coals Using ASTM Procedures

D2015, D3180, D3177, D3173, and D3174

J. C. Colbert and D. R. Kirklin

Twenty-four bottled samples of the NBS coal SRM's (2682, 2683, 2684, and 2685) were analyzed for sulfur content by the gravimetric method, gross calorific value by bomb calorimetry, furnace ash and moisture content.

In addition, one bottle each of the SRM's 1632a and 1635, certified for trace elements in coal, was used as a control sample for purposes of establishing a point of reference for the sulfur content. The coal SRM's are primarily certified for sulfur content with the additional measurements made to certify the gross calorific value and furnace ash content. Sample Preparation

The coal samples for analysis were taken directly from the bottles as issued. No special sample preparation was made. Procedure

Standard bomb calorimetric techniques were used; however, procedures used at NBS contain some modifications that are essentially covered in the ASTM Standards listed below. ASTM D2015 Standard Test Method for Gross Calorific Value of Solid Fuel by the Adiabatic Bomb Calorimeter ASTM D3180 Standard Method for Calculating Coal and Coke Analyses from As-Determined

to Different Bases HHV1 as determined

HHV2 moisture-free

HHV3 moisture-ash-free ASTM D3177 Standard Test Methods for Total Sulfur in the Analysis Sample of Coal and Coke ASTM D3173 Test for Moisture in the Analysis Sample of Coal and Coke ASTM D3174 Test for Ash in the Analysis Sample of Coal and Coke For each coal sample submitted for testing three one-gram samples were weighed in analysis crucibles. Each measurement for moisture ash and gross calorific value required a separate one-gram

sample. The three samples were weighed in the same time period to ensure that effects due to ambient room conditions of relative humidity and temperature were the same. For moisture determination, the weighed analysis sample together with the analysis crucible were dried for 2 hours in a circulating air oven held at 107 +3 C. The loss in weight on drying was calculated as the moisture in the analysis sample and that value is used to convert the calorific value to a moisture free basis. For the ash determination, the weighed analysis sample and crucible were placed in a muffle furnace capable of maintaining a temperature of 725 + 25 °C. The sample was ignited, cooled in a desiccator

and weighed. The calculated amount of ash is used to convert the calorific value to an ash-free

basis. The procedure is detailed in ASTM standard D3174.

The weighed analysis sample and combustion crucible for calorific value were burned in an adiabatic

bomb calorimeter with the procedure being followed as described in ASTM D2015. After combustion,

the interior of the bomb was washed and the washings collected for HNO^ titration and sulfur determination as described in ASTM D2015 and D3177, respectively. A weighed aliquot of the total washings was taken for each determination. The ratio of the aliquot and total washings was used in the individual calculations for HNO, and sulfur.

14
Benzoic Acid Calibrations

All measurements were made in a Parr adiabatic bomb calorimeter of the type used in many commercial laboratories. A series of 5 calibrations was made on the Parr calorimeter using benzoic acid supplied by the Parr Company (which is traceable to NBS SRM 39i). The calibrations were done with a precision of 0.07 percent. Results

The results .of the measurements made on the four coal SRM's, 2682, 2683, 2684, and 2685 are

tabulated in Tables la through Id. The tables include data on residual moisture, dry furnace ash

(as weight percent), higher heating value-1 (HHV1 as determined), HHV2-(moisture free), HHV3 (moisture-ash-free) in BTU.lb , and dry sulfur content in weight percent. Table 2 contains the data summary for the coals, including mean value, standard deviation of a single measurement and

percent, standard deviation for moisture, ash, sulfur content, HHV1, HHV2, and HHV3j A conversion to MJ.kg ^is given for each mean calorific value. The conversion factor of 1 MJ.kg = 429.9226 BTU.lb was used to calculate the values presented in parenthesis. Table 3 lists the mean value (+1 standard deviation for a single measurement) for the dry sulfur content in weight percent for SRM's 2682 through 2685. Each is a mean of ten determinations.

Three determinations each were made on the control coals 1632a and 1635. There were no moisture

corrections made on these controls due to their being pre-dried before testing; therefore, the as- determined data (HHV1) and the moisture-free data (HHV2) are the same. Table 4 gives the individual experimental results on the control coals. The data included are SRM number, dry furnace ash (as a fraction), dry sulfur in weight percent HHV1, HHV2, and HHV3. Table

5 gives the data summary for the control coals, including mean, standard deviation and percent standard deviation of a single measurement for furnace ash, sulfur content and the calorific values calculated to the three basis. Table 6 compares the experimental sulfur data to the certified values given for sulfur on the SRM certificate for 1632a and 1635. The experimental data is a mean of three determinations (+1 standard deviation of a single measurement).

Table la

SRM

No Bottle

No Moist Wt.%

Fur Ash Wt.%

HHV1 HHV2

(BTU/LB) HHV3 Sulfur

Wt.%

2682 609 18.667 6.465 9677.69 11898.85 12721.25 0.35261

2682 432 17.264 6.501 9643.94 11656.28 12466.80 0.50822

2682 911 18.647 6.656 9519.59 11701.58 12536.00 0.39365

2682 1086 18.938 6.500 9603.42 11847.01 12670.59 0.39590

2682 1086 19.262 6.226 9583.86 11870.32 12658.48 0.46726

2682 1293 19.280 6.150 9547.86 11828.37 12603.44 0.45976

2682 432 17.335 6.130 9656.31 11681.26 12444.02 0.40597

2682 1293 19.148 6.078 9531.19 11788.44 12551.27 0.46002

2682 156 19.041 6.292 9634.09 11899.96 12698.99 0.43877

2682 156 18.990 6.647 9568.13 11811.05 12652.07 0.44926

Ave 18.657 6.365 9596.61 11798.31 12600.29 0.433

S.D. +0.7 47* +0.216 +55.17 +89.69 +96.71 +0.046

HHV1 - as received HHV2 - moisture free HHV3 - moisture-•ash-free

* Standard deviation of a single measurement

15
Table lb SRM No Bottle No Moist Fur Ash Wt.% HHV1 HHV2 HHV3 Sulfur Wt.% (BTU/LB)

2683 609 1.443 6.829

2683 432 1.547 6.832

2683 156 1.200 6.842

2683 911 1.516 6.856

2683 1086 1.451 6.828

2683 1086 1.381 6.899

2683 1293 1.446 6.894

2683 432 1.497 6.858

2683 1293 1.436 6.813

2683 156 1.258 6.846

Ave S.D.* 1.418 6.850 + 0.110 + 0.028

13854.40 14057.25 15087.50 1.68397 13852.01 14069.67 15101.34 1.86585 13886.76 14055.43 15087.75 1.93237 13855.27 14068.55 15104.08 1.77527 13864.12 14068.25 15099.23 1.77964 13855.50 14049.52 15090.67 1.80972 13844.65 14047.78 15087.89 1.78642 13851.97 14062.49 15097.85 1.76395 13848.76 14050.53 15077.75 1.80421 13902.17 14079.29 15114.02 1.73143 13861.56 14060.88 15094.81 1.793 + 18.41 + 10.49 + 10.47 + 0.068

HHV1 - as received HHV2 - moisture free HHV3 - moisture-ash-free

* Standard deviation of a single measurement

Table lc Bottle No Moist Fur Ash Wt.% HHV1 HHV2 HHV3 Sulfur Wt.% (BTU/LB)

2684 609 3.199 1.074 12277.15 12682.88 14262.33 2.87425

2684 911 3.246 1.244 12474.89 12893.41 14526.80 2.91589

2684 1086 3.283 1.191 12334.97 12753.67 14360.85 2.89642

2684 156 3.962 1.029 12371.54 12749.17 14329.53 2.85126

2684 432 3.135 1.064 12321.74 12720.53 14302.99 2.86697

2684 1086 3.364 1.107 12317.79 12746.59 14339.19 2.89740

2684 1293 3.485 1.050 12318.19 12762.98 14348.51 2.81185

2684 432 3.217 1.059 12341.56 12751.79 14337.32 2.88786

2684 1293 3.423 1.098 12303.86 12739.95 14330.31 2.87180

2684 156 3.048 1.898 12352.95 12741.31 14299.72 2.86248

Ave S.D.* 3.236 11.081 12341.46 12754.23 14343.76 2.874 + 0.163 + 0.093 + 53.67 + 53.89 + 70.31 + 0.029 HHV1 - as received HHV2 - moisture free HHV3 - moisture-ash-free

16
Table Id Moisture, Furnace Ash, Heating Values and Sulfur Content

in Individual SRM Coal 685

SRM No Bottle No Moist Wt.% Fur Ash Wt.% HHV2

( BTU/LB)

HHV3 Sulfur Wt.%

2685

2685

2685 2685 2685

2685

2685

2685

2685 2685

609 432

911 1086

156 1086

1293 432

1293

156

1.466 1.523

1.469

1.469 1.469

1.418

1.349 1.645 1.464

1.467

6.592 6.576

6.648 6.555

6.573 6.485

6.429

6.535 6.386

6.451

11870.27 12012.07

11964.77 11876.49

11891.28

11868.29 11927.49 11986.45 11908.50

11872.76

12046.88

12197.84

12143.15 12053.56 12039.00

12039.00

12090.59 12186.92 12085.43

12049.53

14443.36

14621.58

14568.44 14444.95

14415.34

14415.34

14467.38 14601.24

14453.82

14422.17

4.36829 4.44933

4.45855

4.48801 4.43629

4.43629

4.48301 4.33383

4.51483

4.54138

Ave

.

S.D. 1.474 + 0.075

16.523

- 0.082 11917.84 + 52.85 12096.15 + 59.04 14490.44 + 76.46

4.448 + 0.064

Table 2 Summary of Data on SRM Coals 2682, 2683, 2684, and 2685 (Calorific Values in Btu'lb" 1 (MJ'kg

-1

)

SRM No Residual Moisture

Wt.%

Furnace Sulfur HHVl 3 Ash Wt.%

Wt.%

HHV2 HHV3

2682Mean 18.657

Std. Dev.*

% S.D.

.747 4.004

6.365 0.433 9596.61 (22.3217) 11798.31 (27.4429)

.216 0.046 55.17 (.1283) 89.685 (.0286)

3.394 0.11 .5749 (.0013) .7601 (.0018)

12600.29 (29.3083) 96.706 (.2249)

.7675 (.0018) 2683Mean

Std. Dev.*

% S.D.*

1.418 6.850 1.793 13861.56 (32.2420) 14060.88 (32.7056)

.110 .028 0.068 18.41 (.0428) 10.4488 (.0243) 7.757 .409 0.04 .1328 (.0003) .0743 (.0002)

15094.81 (35.1105)

10.4654 (.0243)

.0693 (.0002) 2684Mean

Std. Dev.*

%S.D.

3.236 11.081 2.874 12341.46 (28.7062) 12754.23 (29.6663) 14343.76 (33.3636)

.163 .093 0.029 53.67 (.1248) 53.8880 (.1253) 70.3141 (.1636)

5.037 .839 0.01 .4349 (.0010) .4225 (.0010) .4902 (.0011) 2685Mean

Std. Dev.*

% S.D.

1.474 16.523 4.448 11917.84 (27.7209) 12096.15 (28.1357) 14490.44 (33.7048)

.075 .082 0.064 52.85 (.1229) 59.0447 (.1373) 76.4561 (.1778) 5.088 .496 0.01 .4435 (.0010) .4881 (.0011) .5276 (.0012)

Additional decimal places were added to eliminate rounding errors when making conversions between BTU'lb and MJ'kg . Standard deviation of single measurement.

17
Table 3 Sulfur Content - SRM's 2682, 2683, 2684, 2685

SRM No. Mean + 1 S.D.*

2682 0.433 + .046 2683 1.793 + .068 2684 2.874 + .029 2685 4.448 + .064 *Standard Deviation of a single measurement

Table 4 Furnance Ash, Sulfur Content and Heating Values of SRM Coals 1632a and 1635 Fur Ash

(FRAC) Sulfur Wt.% HHV2 (BTU/LB)

1632a 632a

1632a

1635 1635

1635

0.21846

0.21846

0.21816

0.04009 0.03945

0.03908

1.56282 1.54388

1.48872 0.31641 0.31830

0.30779

11156.59

11229.92

11233.67 11613.23

11813.07 11862.46

11156.59

11229.92

11233.67 11613.23

11813.07 11862.46

14275.13

14368.96

14368.25 12098.25 12298.24

12344.90

HHVl = HHV2, sample dried before combustion.

18
Table 5

Summary of Data on Controls 1632a and_1635 (Calorific Value in Btu'lb (Mj'kg )

SRM No Furnace Sulfur HHV1* HHV3 Ash Wt.% Wt.%

1632a Mean 21.836 1.532 11207.73 (26.06685) 14337.45 (33.34891)

Std. Dev.* .017 0.039 43.460 (.10109) 53.969 (.12553)

% S.D.* .078 .38780 (.0009) .37642 (.00088)

1635Mean 3.954 0.314 11762.92 (27.36055) 12257.13 (28.48683)

Std. Dev.* .051 0.006 131.967 (.30696) 131.028 (.30477)

% S.D.* 1.290 1.12189 (.00261) 1.06987 (.00249)

* HHV1 = HHV2, sample dried before combustion. HHV3 = Moisture-ash-free.

* Standard deviation of single measurement. Certified Sulfur Values

1632a 1.58 + 0.04

1635 0.33 + 0.03

Table 6 Sulfur Content - SRM 1632a, 1635

(wt. percent)

This Report

SRM No. (Mean ± 1 S.D.*) Certificate

1632a 1.532 + .039 1.58+0.04

1635 0.314 + .006 0.33 + .03 *Standard Deviation of a single measurement

19
SECTION IV Determination of Sulfur in NBS Coals by a Modified High Temperature Method (D1552)

P. T. S. Pei and S. Weeks

The method used in the analyses was the modified ASTM D1552, Standard Test Method for Sulfur in Petroleum Products (High Temperature Method.) This method involves the burning of a coal sample in

a stream of oxygen at a sufficiently high temperature to convert the sulfur to sulfur dioxide. A standardization factor was employed for obtaining accurate analysis results. For this work, SRM fuel oil standards were used for the standardization factor as required in Section 7-2 of the ASTM Method D1552. The combustion products are passed onto an absorber containing an acid solution of potassium iodide and starch indicator. A slight blue color is developed in the absorber solution by the addition of standard potassium iodate solution. As combustion proceeds, bleaching the blue color, more iodate is added. The amount of standard iodate consumed during combustion is a measure

of the sulfur content of the sample. The sample preparation procedures, apparatus and fuel oil standards used for the analyses of the coal SRM's are given below.

1 . . Apparatus

An induction furnace was used for the combustion of the samples. An automatic titrator was used for the titration of the sulfur dioxide evolved during the combustion of the sample.

2 . Preparation of Samples

Coal samples were dried in a vacuum oven at room temperature for 24 hours before analysis. The sample preparation procedure for the induction - type furnace is followed with the following modification. During the preparation of the sample, a drop of high viscosity and sulfur free mineral oil ( 20 mg) is added onto the coal sample and also a light layer of magnesium oxide ( 50 mg) is added to cover the coal sample before the addition of the iron powder and tin.

3. Determination of Standardization Factor

SRM fuel oil standards have been used for the standardization factor stated in Section 7-2 of the method.

SRM 1623a (0.21%) for 0.5% Sulfur coal SRM 1622b (1.98%) for 2.0% Sulfur coal SRM 1634a (2.85%) for 3.0% Sulfur coal SRM 1620a (4.5 %) for 4.5% Sulfur coal

4. Sample Size and Titrant Cone.

Sample it Sample Wt. Cone, of K10

3 2682 50 mg 0.0006238N

2683 40 mg 0.006238N

2684 25 mg 0.006238N

2685 20 mg 0.006238N

5. Results

The individual results for total sulfur in SRM's 2682-4 are given in Table 1 along with the mean and standard deviation of a single measurement. The moisture content determined by drying the coals for

24 hours under vacuum at 24 C are shown in Table 2.

20
Table 1 % Sulfur in SRM Coal Samples of Different Concentrations

as Determined by Modified ASTM D1552

Sample 2682 2683 2684 2685

767 0.464 1.77 2.91 4.59

1-1 0.489 1.79 2.71 4.65 544-1 0.468 1.79 2.97 4.70

491-1 0.456 1 .82 3.15 4.69

1176 0.476 1 .82 3.17 4.51

128 0.464 1.81 2.91 4.67 876-1 0.461 1.88 3.09 4.78 491-2 0.461 1.81 3.08 4.51 968 0.470 1.78 2.97 4.73 1370-1 0.490 1.86 2.82 4.60

716 0.493 1.86 3.03 4.62 544-2 0.471 1.77 2.94 4.75 876-2 0.506 1.83 3.11 4.60

1022 0.489 1.77 2.99 4.66

1-2 0.474 1.87 3.05 4.78

71 0.462 1.74 2.99 4.68

370 0.501 1.76 3.11 4.47 1370-2 0.494 1.84 3.02 4.68

1486 0.474 1.81 2.94 4.43 Mean 0.477 1.81 3.00 4.64

Std. Dev.* 0.015 0.04 0.11 0.10

Note: Sample #1178 was not available at the analys *Standard Deviation of a single measurement

Table 2 Moisture Content in SRM Coal Samples

Sample # 2682 2683 2683 2684 767 19.3 1.4 3.6 1.6

1-1 1.6 3.7 1.6 544-1 18.7 1.6 3.5 1.5 491-1 18.3 1.5 1.8 1176 18.4 1.4 3.6 1.7 128 18.7 1.4 3.5 1.6 876 18.2 1.5 3.3 1.7 491-2 18.7 1.3 3.6 1.7 968 18.8 1.7 3.6 1.6 1370 18.3 1.7 3.5 1.6 716 19.5 1.6 3.5 1.6 544-2 19.0 1.7 3.6 1.7 876-2 19.1 1.8 3.4 1.5 1022 19.0 1.8 2.8 1.6 1-2 19.3 1.7 3.8 1.6 71 18.8 1.7 3.6 1.8 370 19.3 1.7 3.6 1.6 1370-2 19.2 1.8 3.6 1.5 1486 19.3 1.7 3.5 1.7 Mean 18.9 1.6 3.5 1.6 Std. Dev.* +0.4* +0.2 +0.2 +0.1 *Standard Deviation of a single measurement

21
SECTION V Determination of Sulfur and Major Inorganic Constituents by Neutron-Capture Prompt- Activation Analysis - H, B, C, N, Al, and S R. M. Lindstrom

Procedure Vacuum-dried samples of coal (0.5-1.0 g) were pressed into 13-mm pellets, heat-sealed into cleaned Mylar bags, and irradiated in the prompt-facility of the National Bureau of Standards Reactor (NBSR) for 7-40 hours. Compton-suppressed y -ray spectra were collected in the memory of a data acquisition system and stored on disk and the spectral peaks integrated. Corrections for background and for interfering peaks were carried out by hand calculation. The apparatus and procedures have been

described elsewhere [1]. Results and Discussion

The high hydrogen content of coals required that account be taken of enhanced signal (due to neutron thermalization in the sample) and increased background (due to scattering into the surrounding apparatus) over that of standards containing low hydrogen. Allowance has been made for these effects by using hydrogeneous standards and backgrounds to calibrate the system. The individual values obtained in these analyses are given in Tables 1, 2, 3, and 4. The error estimates in these tables are computed from counting statistics alone and therefore are lower limits

to the true uncertainty, particularly for H and B where the analytical signal is strong. For these elements, the intersample reproducibility is a more realistic estimate of accuracy. The weighted mean values for each SRM and recommended values are summarized in Table 5, together with estimated standard deviations computed from both sources of inaccuracy.

Two samples of SRM 1632a, Trace Elements in Coal, were analyzed in parallel as controls. The concentrations found are compared with previous values in Table 6.

[1] M. P. Failey, et al .

, Anal. Chem. , 51, 22 09 (1979).

22
Table 1 Data for Major Constituents in NBS Coal Samples, SRM 2682

Sample No. 1 2 3 4 Bottle No. 516 1465 893 893 Weight, g 1.0727 1.0007 0.6471 0.5807

% H (2223) 4.74 + 0.01 4.56 + 0.01 4.59 + 0.01 4.87 + 0.01

PI3m B (478) 38.5 + 0.4 37.7 + 0.4 39.5 + 0.4 41.0 + 0.4

% C (3684) 68.6 + 2.0 68.5 + 1.9 74.1 + 2.5 81.6 + 4.3

% N (1884) 1.13 + 0.30 1.03 + 0.27 0.68 + 0.35 1.26 + 0.68 (3678) 1.46 + 0.20 1.12 + 0.21 0.85 + 0.28 1.88 + 0.47

% Al (1779) 0.51 + 0.05 0.48 + 0.04 0.56 + 0.06 0.54 + 0.07

% S (840) 0.451 + .016 0.435 + .015 0.437 + .020 0.486 + .034 (2379) 0.456 + .024 0.454 + .023 0.444 + .028 0.437 + .052 (3220) 0.420 + .038 0.446 + .037 0.471 + .048 0.483 + .094

The number in parentheses is the energy KeV of the gamma ray used for quantitation. Uncertainties are given as the standard deviation based on counting statistics alone, and thus are lower limits to the true uncertainty.

Table 2

Data for Major Constituents in NBS Coal Samples, SRM 2683

Sample No. 1 2 3 4 Bottle No. 1021 1451 127 122 Weight, g 0.9886 1.0023 0.7199 0.8342

% H (2223) 4.99 + 0.01 4.85 + 0.01 5.21 + 0.02 5.05 + 0.01 ppm B (478) 66.9 + 0.4 64.1 + 0.4 69.8 + 0.6 67.6 + 0.5

% C (3684) 78.9 + 1.7 75.4 + 2.1 83.4 + 2.9 74.6 + 4.3

% N (1884) 1.72 + 0.47 1.99 + 0.58 1.38 + 0.67 2.03 + 0.89 (3678) 2.80 + 0.28 0.85 + 0.26 0.73 + 0.39 1.56 + 0.53

% Al (1779) 0.91 + 0.04 0.91 + 0.04 0.54 + 0.07 0.88 + 0.08

% S (840) 1.82 + 0.02 1.77 + 0.03 1.90 + 0.03 1.84 + 0.04

(2379) 1.82 + 0.04 1.74 + 0.05 1.89 + 0.06 1.93 + 0.07 (3220) 1.76 + 0.07 1.77 + 0.07 1.71 + 0.08 1.81 + 0.11

The number in parentheses is the energy KeV of the gamma ray used for quantitation. Uncertainties are given as the standard deviation based on counting statistics alone, and thus are lower limits to the true uncertainty.

23
Table 3

Data for Major Constituents in NBS Coal Samples, SRM 2684

Sample No. 1 2 3 4 Bottle No. 1204 482 864 1209 Weight, g 1.0106 1.0191 0.9433 0.8098

% H (2223) 4.62 + 0.01 4.82 + 0.01 4.74 + 0.01 4.87 + 0.01 ppm B (478) 111.0 + 0.4 113.2 + 0.4 115.0 + 0.4 118.4 + 0.5

% C (3684) 66.5 + 1.9 69.2 + 1.3 69.4 + 3.6 64.8 + 5.0

% N (1884) 1.75 + 0.48 1.95 + 0.44 1.81 + 0.89 0.8 + 0.9 (3678) 1.64 + 0.29 1.79 + 0.33 1.79 + 0.46 0.7 + 0.6

% Al (1779) 1.13 + 0.04 1.18 + 0.03 1.12 + 0.07 1.11 + 0.10

% S (840) 2.88 + 0.03 2.95 + 0.03 3.00 + 0.04 3.01 + 0.06

(2379) 2.87 + 0.07 3.02 + 0.06 2.99 + 0.08 2.86 + 0.10

(3220) 2.85 + 0.10 3.04 + 0.11 3.02 + 0.13 2.60 + 0.15

The number in parentheses is the energy KeV of the gamma ray used for quantitation. Uncertainties are given as the standard deviation based on counting statistics

alone, and thus are lower limits to the true uncertainty.

Table 4

Data for Major Constituents in NBS Coal Samples, SRM 2685

Sample No. 1 2 3 4 Bottle No. 1474 481 487 847 Weight, g 0.9824 0.5326 0.7870 0.8934

% H (2223) 4.39 + 0.01 4.95 + 0.02 4.75 + 0.01 4.70 + 0.01 ppm B (478) 103.9 + 0.4 114.1 + 0.8 113.9 + 0.5 111.4 + 0.5

% C (3684) 63.5 + 1.8 66.2 + 2.5 71.9 + 3.3 65.2 + 3.2

% N (1884) 1.6 + 0.5 1.2 + 0.8 1.7 + 0.7 0.9 + 0.7 (3678) 1.0 + 0.3 1.2 + 0.5 0.9 + 0.4 1.0 + 0.4

% Al (1779) 1.69 + 0.04 1.74 + 0.06 1.85 + 0.06 1.84 + 0.06

% S (840) 4.39 + 0.05 4.80 + 0.06 4.73 + 0.06 4.71 + 0.06 (2379) 4.35 + 0.09 4.91 + 0.11 4.81 + 0.11 4.76 + 0.11 (3220) 4.54 + 0.15 4.87 + 0.17 4.60 + 0.16 4.58 + 0.17

The number in parenthesis is the energy KeV of the gamma ray used for quantitation. Uncertainties are given as the standard deviation based on counting statistics alone, and thus are lower limits to the true uncertainty.

24
Table 5

Summary of Concentrations for Major Constituents

in NBS Coal Samples

Element SRM 2682 SRM 2683 SRM 2684 SRM 2685

% H 4.7 + 0.1 5.0 + 0.1 4.8 + 0.1 4.6 + 0.2

g/ g B 39 + 1 67 + 2 114 + 3 109 +5

% C 76 + 4 79 + 4 68 + 2 66 +3

% N 0.8 + 0.3 1.6 + 0.9 1.6 + 0.4 1.1 + 0.3

% Al 0.51 +0.03 0.86+0.14 1.15+0.03 1.76+0.08

% s 0.447 + 0.013 1.82 + 0.05 2.94 + 0.07 4.64 + 0.19

The uncertainties quoted are an estimate of the standard deviation of individual single measurements including both counting statistics and intersample precision.

Table 6 Analysis of SRM 1632a, Coal Element

Peak Energy Previous

Kev Sample A Sample B Analysis Reference

% H (2223) 4.3 + 0.1 4.3 + 0.1 4.17 + 0.01 2 g/g B (478) 59+5 60+5 53+2 2 % C (3684) 61 +2 59 +4 62.70 + 0.06 2

% N (1884) 1.5 +0.5 0.7 +0.7 1.26 +0.03 2 (3678) 1.4 + 0.2 1.6 + 0.5

% Al (1779) 3.14+0.05 3.05+0.09 (3.07) 1

% S (840) 1.57 + 0.02 1.57 + 0.04 (1.64) 1 (2379) 1.54+0.04 1.54+0.07

(3219) 1.46 + 0.06 1.63 + 0.11

1 - NBS Certificate of Analysis, October 1983. Values in parentheses are not certified.

2 - E.S. Gladney, Anal. Chim Acta, 18, 385 (1980) and references therein. Note: The number in parenthesis is the energy KeV of the gamma ray used for quantitation. The uncertainties are given as the standard deviation of a single measurement based on country statistics alone and thus are lower limits to the true uncertainty.

25
SECTION VI Determination of Minor Inorganic Constituents

by Neutron Activation Analysis - Ca, CI, K, Mg, Mn, Na, Ti, and V

R. F. Fleming

Samples for Analysis : One sample was taken from each of six bottles for each of the four SRM coals. Vacuum-dried samples of the powdered coal (0.35-0.67 g) were pressed into 0.5 inch diameter pellets

and heat-sealed into cleaned 1 mil polyethylene bags. Procedure : Each sample was irradiated for 60 seconds in the NBS^Research Reactor (NBSR) irradiation

facility,' RT-4, and counted three times at 28 cm from the 104 cm Ge (Li) detector. The counts were begun typically at 15, 30, and 180 minutes after the irradiation. The photopeak data from the first

two counts were used to quantify Ca, CI, Mg, Ti, and V, while the third count gave the best results

for K, Mn, and Na. The use of two gamma lines gave redundant results for CI, Mn, and Na. The pure metals were used as standards for Mg, Mn, Ti, and V, while NBS certified SRMs were used for Ca (SRM

915), CI and K (SRM 999), and Na (SRM 40h)

.

Results : The data for the eight elements are summarized in Table 1. No bottle-to-bottle variability was observed outside the indicated uncertainty except for the CI result for SRM 2682. Here the range of results (-37% to +125%) was too great for any mean value or range to be estimated.

The CI data for the other three coals shows no variability at the +3 percent level, and the other eight elements measured for SRM 2682 are all consistent.

26
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30
Table 5 Summary of Elemental Concentrations in SRM Coals (yg/g + 2s)

SRM 2682 SRM 2683 SRM 2684 SRM 2685

Ca 11430 + 560 2047 + 200 4355 + 200 5234 + 500 CI 1294 + 40 1292 + 36 647 + 14 K 235 + 140 756 + 240 1969 + 250 2705 + 200 Mg 1713 + 185 465 + 265 775 + 150 1061 + 150 Mn 26.2+ 0.6 13.0+ 1.2 35.6+ 0.6 40.7+ 1.0 Na 1030 + 20 502 + 20 261 + 8 764 + 15 Ti 505 + 85 438 + 120 577 + 150 890 + 65 V 14.6 + 0.7 14.0 + 1.1 21.9 + 1.2 30.5 + 1.3

The uncertainties are given as two times the standard deviation of single measurements

31
SECTION VII Multielement Analysis of NBS Coals by Instrumental Neutron Activation Analysis

R. R. Greenberg

Procedure : One 250 mg sample of vacuum-dried coal from each of six or seven bottles of ^ach coal, yas doubly sealed in polyethylene bags and irradiated for two hours in the RT-3 (5 x 10 n.cm. s

) pneumatic tube facility of the NBS Research Reactor along with multielemental standards, blank

bags, and two samples of SRM 1632a. Mid-way through the irradiation, the rabbit was removed from

the reactor, flipped end-over-end, and reinserted into the reactor, to provide a uniform neutron fluence within the rabbit. Beginning three days after irradiation, the outer bag of each sample was removed and discarded, and the samples were counted three times at a distance of 10 cm from a GammaX detector. Two different peak integration routines were used for all elements. Results and Discussions : The results of the coal analyses are listed in Tables 1-4. The observed sample-to-sample variations for all elements in SRM 2682, except Br, appeared to be consistent with

the counting statistics. The observed standard deviation of a single measurement for Br was approximately 4-5 times greater than expected from the counting statistics, indicating some inhomogeneity for this element. The observed standard deviation of a single measurement for As, Co, and Fe in SRM 2683 were more than twice as great as expected from the counting statistics indicating a degree of inhomogeneity

for these elements. The possibility of problems during analysis such as geometry errors, counting

errors, weighing errors, etc., can be eliminated since the observed standard deviation for Sc was only 0.4 percent (Is - relative), and these errors would affect Sc in the same manner as the other elements

.

The observed standard deviation of a single measurement for As, Br, Cr, Fe, La, Sc, Sm, and Zn in SRM 2684 were more than twice as great as expected from the counting statistics indicating a degree

of inhomogeneity for these elements. Although Br and Zn varied independently, the other elements,

Cr, Fe, La, Sc, and Sm, exhibited similar behavior, in that bottles 858, 864, and 1024 had relatively higher concentrations of these elements than did bottles 482, 1209, and 1469. This variability could not be due to analytical problems arising from different geometries, moisture

content, weighing errors, dead time effects, etc., since these would affect the concentrations of each element within a sample to the same degree. The Fe concentration in bottle 858, for example,

was considerably higher than in bottle 864, 1.490 + 0.005 percent (Is) vs. 1.465 + 0.005 percent, while the reverse was observed for Sm, 1.114 + 0.002 Pg/g (Is) compared to 1.124 + 0.002 Pg/g. The observed standard deviation of a single measurement for As, La, and Fe in SRM 2685 were more than three times as great as expected from the counting statistics indicating a degree of inhomogeneity for these elements. The observed standard deviations for single measurements Sc and

Sm, 0.5 percent and 0.4 percent (Is relative) although small, are approximately twice as great as expected from the counting statistics, and perhaps indicate some small inhomogeneity for these elements

.

32
Table 1 Summary of Concentrations Observed in Coal, SRM 2682 Mean Concentration (yg/g) + 2s*

As 1.00 + 0.04 La 5.17 + 0.05

Ba 382 + 10 Sb 0.189 + 0.018

Br 3.74 + 0.35** Sc 1.524 + 0.010

Ce 9.87 + 0.16 Se 0.91 + 0.19

Co 1.66 + 0.06 Sm 0.776 + 0.008

Cr 15.4 + 0.5 Th 1.532 + 0.027 Eu 0.172 + 0.010 U 0.519 + 0.030

Fe 2420 + 30 W 1,81 + 0.05

Hf 0.60 + 0.03 Zn 8.6 + 1.8 K 117 +28

*Two times the standard deviation of a single measurement **Variability more than twice as great as counting statistics.

Table 2 Summary of Concentrations Observed in Coal, SRM 2683 Mean Concentration (yg/g) + 2s*

As 3.64 + 0.26** La 5.05 + 0.07 Ba 71 + 6 Sb 0.279 + 0.015

Br 16.85 + 0.07 Sc 1.941 + 0.016

Ce 9.18 + 0.15 Se 1.23 + 0.17 Co 2.22 + 0.18** Sm 0.859 + 0.010

Cr 11.02 + 0.36 Th 1.363 + 0.022

Cs 0.44 + 0.04 U 0.418 + 0.021 Eu 0.177 + 0.012 w 0.48 + 0.05

Fe 7620 + 380** Zn 9.5 + 1.1 Hf 0.418 + 0.008 K 750 + 20

*Two times the standard deviation of a single measurement **Variability more than twice as great as counting statistics.

33
Table 3 Summary of Concentrations Observed in Coal, SRM 2684 Mean Concentration (^g/g unless % indicated) + 2s*

As 3.867 + 0.269** La 6.650 + 0.202** Ba 41.4 + 5.5 Rb 14.6 + 2.2 Br 10.57 + 0.87** Sb 0.354 + 0.016

Ce 11.51 + 0.36 Sc 2.665 0.041**

Co 3.85 + 0.10 Se 1.87 + 0.31 Cr 16.81 + 0.66** Sm 1.109 + 0.023**

Cs 1.15 + 0.09 Th 1.955 + 0.032 Eu 0.226 + 0.018 U 0.901 + 0.020

Fe (%) 1.454 + 0.051** W 0.562 + 0.043

Hf 0.565 + 0.025 Zn 110.0 + 23.6** K 1969 + 31

*Two times the standard deviation of a single measurement **Variability more than twice as great as counting statistics.

Table 4 Summary of Concentrations Observed in Coal, SRM 2685 Mean Concentration (Vg/g unless % indicated) + 2s*

As 12.28 + 0.76** La 10.19 + 0.22**

Ba 105 + 11 Rb 16.8 + 2.6 Br 5.57 + 0.14** Sb 0.357 + 0.023

Ce 17.88 + 0.35 Sc 3.700 + 0.038**

Co 4.57 + 0.11 Se 1.91 + 0.31 Cr 22.3 + 0.8 Sm 1.729 + 0.014**

Cs 1.31 + 0.13 Th 2.66 + 0.05 Eu 0.357 + 0.007 U 0.948 + 0.025

Fe (%) 2.396 + 0.130** w 1.18 + 0.11 Hf 0.913 + 0.022 Zn 17.1 + 2.1 K 2592 + 89

*Two times the standard deviation of a single measurement **Variability at least twice as great as counting statistics.

34
SECTION VIII Statistical Analysis and Certification

of NBS Sulfur in Coal SRM's

R. C. Paule

Statistical analyses have been made on a variety of data obtained from the proposed coal SRM's 2682-

2685. The properties to be certified are sulfur content, ash content, and HHV2 heating value. A stratified random sampling plan was used to inspect the bottles of each coal for the above three properties. The data have been tabulated in Sections I-III. Sulfur

The percent sulfur was certified based on three analytical methods: ion chromatography, gravimetry,

and thermal ionization mass spectrometry. Two additional techniques, prompt-gamma activitation

analysis and a combustion technique, were used for confirmation and a test of the utility of the SRM's. The between-bottle variability for sulfur was not statistically significant for any of the four coals. The general approach for the statistical analyses of the SRM certificate has been

reported in references (1) and (2). All three analytical methods for sulfur analysis had relatively high internal precisions. The observed differences of results from the three methods, however, were appreciably greater than that expected from the internal precisions. Gravimetry gave the lowest results, ion chromatography gave intermediate results, and thermal ionization mass spectrometry gave the highest results. The uncertainty of the weighted average for each SRM is primarily determined by the variabilities between the three methods of analysis (1). For percent sulfur, the SRM weighted averages and associated two standard error values are as follows:

SRM Number 2682 2683 2684 2685

Wt. % Sulfur + .47+.03 1.85+.06 3.00+.13 4.62+.18

2 Std. Errors

Cal orific Value and Ash Content

The ash content and the HHV2 heating values for the four coals were each determined by a single method of analysis. Three of the four SRM's had moderate (but not statistically significant) between-bottle variabilities for ash content. These observed variabilities have been included in the overall SRM uncertainty statements. Since the between-bottle variability is not moderated by an averaging of results, this variability contributes appreciably to the overall uncertainty of the ash content for SRM's 2682, 2684, and 2685. For weight percent ash, the SRM weighted averages and associated two standard error values are as follows:

SRM Number 268 2 2683 2684 2685

Wt. % Ash + 6.37+.18 6.85+.02 11.09+. 18 16.53+. 15

2 std. errors

For the HHV2 heating values, we observed statistically significant between-bottle variabilities for SRM's 2682, 2684, and 2685. These variabilities are included in the overall SRM statements of uncertainty. In addition, an allowance of 50 BTU/LB for possible sample degradation has been

included in the overall uncertainty statements. The total uncertainty intervals given below are the sums of two standard errors plus the 50 BTU/LB degradation allowance. For HHV2 heating value, the SRM weighted averages and associated uncertainty intervals are as follows: SRM Numbe r 268 2 268 3 2684 2685

HHV2 in BTU/LB + 11800 + 240 14060 + 60 12760 + 200 12100 + 180 Uncertainty Interval

Majo r and Minor Elements

The information values for major and minor elements are based on measurements made by a single

method or technique and were not carried through the statistical calculations. While no reason

35
exists to suspect systematic bias in these numbers, no attempt was made to determine if such bias attributable to the methods exist. Those values are not certified and are to be used for information only.

(1) Paule, R. C. and Mandel, J., Consensus Values and Weighting

Factors, J. of Res. NBS, 8_7, 377 (1982).

(2) Mandel, J., and Paule, R. C. , Interlaboratory Evaluation of a Material with Unequal Numbers of Replicates, Anal. Chem. , 42 , 1194 (1970) and Correction, Anal. Chem., 43, 1287 (1971).

36
NBS-114A (REV. 2-BC) U.S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publication Date BIBLIOGRAPHIC DATA REPORT NO. SHEET (See instructions) NBS/SP-260/94 December 1984

4. title and SUBTITLE Standard Reference Materials:

Methods and Procedures Used at the National Bureau of Standards To Certify Sulfur

in Coal SRM's for Sulfur Content, Calorific Value, Ash Content

5. AUTHOR(S) Thomas E. Gills, Editor

6. PERFORMING ORGANIZATION (If joint or other than NBS, see instructions) NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE GAITHERSBURG , MD 20899

7. Contract/Grant No.

8. Type of Report & Period Covered Final

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP) Same as in item 6 above.

10. SUPPLEMENTARY NOTES Library of Congress Catalog Card Number: 84-601148

fj -

J Document describes a computer program; SF-185, FlPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant Information. If document includes a si gnificant bibliography or literature survey, mention it here) This Special Publication consists of a collection of analytical methods used at NBS for the determination of total sulfur, calorific value, and ash content in four different coals, SRM's 2682, 2683, 2684, and 2685, with nominal sulfur con- tents of 0.5, 2.0, 3.0, and 4.5 percent, respectively. Also, included are descriptions of methods and procedures used for providing noncertified values for approximately 30 elements including carbon, hydrogen, and nitrogen. These procedures were selected and often specifically developed, by the scientific staff members of NBS, to provide measurements with the best obtainable accuracy and precision,

The materials for these SRM's were obtained and processed by Valley Forge

Laboratories under a grant from the National Bureau of Standards. Material

preparation of the four coal SRM's is described in NBS Special Publication 260-84,

"Sampling, Materials Handling, Processing, and Packaging of Standard Reference

Coal Materials."

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons) analytical procedures; coal analysis; gravimetry; ion chromatography; isotope

dilution thermal ionization mass spectrometry; prompt gamma activation analysis;

sample preparation; thermal neutron activation analysis.

13. AVAILABILITY

\KJ Unlimited

F_7J For Official Distribution. Do Not Release to NTIS

(X7J Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

fJTJ Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

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15. Price

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special publications appropriate to this grouping such as wall charts, pocket cards, and bibliographies. Applied Mathematics Series—Mathematical tables, manuals, and studies of special interest to physicists, engineers, chemists, biologists, mathematicians, computer programmers, and others engaged in scientific and

technical work.

National Standard Reference Data Series—Provides quantitative data on the physical and chemical properties of materials, compiled from the world's literature and critically evaluated. Developed under a worldwide pro- gram coordinated by NBS under the authority of the National Standard Data Act (Public Law 90-396). NOTE: The Journal of Physical and Chemical Reference Data (JPCRD) is published quarterly for NBS by

the American Chemical Society (ACS) and the American Institute of Physics (AIP). Subscriptions, reprints, and supplements are available from ACS, 1155 Sixteenth St., NW, Washington, DC 20056.

Building Science Series—Disseminates technical information developed at the Bureau on building materials, components, systems, and whole structures. The series presents research results, test methods, and perfor- mance criteria related to the structural and environmental functions and the durability and safety

characteristics of building elements and systems. Technical Notes—Studies or reports which are complete in themselves but restrictive in their treatment of a

subject. Analogous to monographs but not so comprehensive in scope or definitive in treatment of the subject

area. Often serve as a vehicle for final reports of work performed at NBS under the sponsorship of other government agencies. Voluntary Product Standards—Developed under procedures published by the Department of Commerce in Part 10, Title 15, of the Code of Federal Regulations. The standards establish nationally recognized re- quirements for products, and provide all concerned interests with a basis for common understanding of the

characteristics of the products. NBS administers this program as a supplement to the activities of the private

sector standardizing organizations. Consumer Information Series—Practical information, based on NBS research and experience, covering areas of interest to the consumer. Easily understandable language and illustrations provide useful background

knowledge for shopping in today's technological marketplace. Order the above NBS publications from: Superintendent of Documents, Government Printing Office, Washington, DC 20402. Order the following NBS publications—FIPS and NBSIR 's—from the National Technical Information Service, Springfield, VA 22161.

Federal Information Processing Standards Publications (FTPS PUB)—Publications in this series collectively constitute the Federal Information Processing Standards Register. The Register serves as the official source of

information in the Federal Government regarding standards issued by NBS pursuant to the Federal Property and Administrative Services Act of 1949 as amended, Public Law 89-306 (79 Stat. 1 127), and as implemented by Executive Order 1 1717 (38 FR 12315, dated May 11, 1973) and Part 6 of Title 15 CFR (Code of Federal

Regulations). NBS Interagency Reports (NBSIR)—A special series of interim or final reports on work performed by NBS

for outside sponsors (both government and non-government). In general, initial distribution is handled by the sponsor; public distribution is by the National Technical Information Service, Springfield, VA 22161, in paper copy or microfiche form.

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