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IVI PUBLICATIONS

NBS SPECIAL PUBLICATION 260-1 02

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

QC

100

U57

#260-102

1986

Standard Reference Materials:

Holmium Oxide Solution

Wavelength Standard

From 240 to 640 nm —

SRM 2034

V. R. Weidner, R. Mavrodineanu

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

K. L. Eckerle, and B. Adams
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 Institute for Materials Science and Engineering

The National Measurement Laboratory

Provides the national system of physical and chemical measurement; • Basic Standards2 coordinates the system with measurement systems of other nations and • Radiation Research

furnishes essential services leading to accurate and uniform physical and • Chemical Physics chemical measurement throughout the Nation's scientific community, in- • Analytical Chemistry

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: 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 Institute for Materials Science and Engineering

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 Institute consists of the following Divisions:

Ceramics

Fracture and Deformation Polymers

Metallurgy

Reactor Radiation

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

Gaithersburg, MD 20899.

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

Holmium Oxide Solution

Wavelength Standard From 240

to 640 nm — SRM 2034

V. R. Weidner*, R. Mavrodineanu**, K. D. Mielenz*, R.A. Velapoldi**, K. L. Eckerle*, and B. Adams*

* Radiometric Physics Division

* "Center for Analytical Chemistry

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 July 1986

% TO i
Library of Congress Catalog Card Number: 86-600560

National Bureau of Standards Special Publication 260-102

Natl. Bur. Stand. (U.S.), Spec. Publ. 260-102, 67 pages (July 1986)

CODEN: XNBSAV

U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1986

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

Standard Reference Materials (SRM's) as defined by the National Bureau of Standards (NBS) are well-characterized materials, produced in quantity and certified for one or more physical or chemical properties. They are used to assure the accuracy and compatibility of measurements

throughout the Nation. SRM's are widely used as primary standards in many diverse fields in science, industry, and technology, both within the United States and throughout the world. They are also used extensively in the fields of environmental and clinical analysis. In many applications,

traceability of quality control and measurement processes to the national measurement system is carried out through the mechanism and use of SRM's. For many of the Nation's scientists and technologists it is therefore of more than passing interest to know the details of the measurements

made at NBS in arriving at the certified values of the SRM's produced. An NBS series of papers, of which this publication is a member, called the NBS Special Publication - 260 Series , is reserved for this purpose.

The 260 Series is dedicated to the dissemination of information on different phases of the preparation, measurement, certification and use of NBS SRM's. In general, much more detail will be found in these papers than is generally allowed, or desirable, in scientific journal articles. This enables the user to assess the validity and accuracy of the measurement processes employed, to judge

the statistical analysis, and to learn details of techniques and methods utilized for work entailing

the greatest care and accuracy. These papers also should provide sufficient additional information

not found on the certificate so that new applications in diverse fields not foreseen at the time the SRM was originally issued will be sought and found. Inquiries concerning the technical content of this paper should be directed to the author(s). Other questions concerned with the availability, delivery, price, and so forth, will receive prompt attention from: Office of Standard Reference Materials National Bureau of Standards Gaithersburg, MD 20899

(301) 921-2045

Stanley D. Rasberry, Chief Office of Standard Reference Materials

iii
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). $5.50* SN003-

003-02558-5.

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). COM74-11059

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). COM74-1 1064** 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 Measure- ments 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**

iv
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* SN003-003-01213-1 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. 260-41 (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-Nickel 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). SN003-003-0 1278-5* 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. 260-47 (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-O03-0 1278-5 Carpenter, B. S., and Reimer, G. M., Standard

Reference Materials: Calibrated Glass Standards for Fission Track Use, NBS Spec. Publ. 260-49 (November 1974). COM74-51I85

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* SN003-003-0 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* SNO03-O03-O1481-8

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 SNO03-OO3-O1551-2

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* SN0O3-O03-

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* SN003-003-0 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* SN003-003

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-O03-O2006-1

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* SN0O3-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* SN003-003-02068

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-O03-021 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* SN003-003-02 167-9 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* SNO03-OO3-O238 1-7 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-O03-O2329-9

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* SNO03-OO3-O2386-8 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-O03-O23-99-O

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* SN003-003-02435-0 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* SN003-003-02447-3

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-

003-02443-1 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* SN003-003-02489-9**

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-O03-02520-8

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-

02521-6

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* SN003-003-02541-1 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* SN0O3-O03-O2544-5 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 Environmental Standard Reference

Materials, Spec. Publ. 260-88 (March 1984). $7.00* SN003-003-02565-8

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

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Hust, J. G., and Langford, A. B., Standard Reference Materials: Update of Thermal

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Goodrich, L. F., Vecchia, D. F., Pittman, E. S., Ekin, J. W., and Clark, A. F., Standard Reference

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

1984). $2.75* SN003-003-02614-0

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

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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

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vii
Mulholland, G. W., Hartman, A. W., Hembree,

G. G., Marx, E., and Lettieri, T. R., Standard

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02665-4

Carpenter, B. S., Gramlich, J. W., Greenberg, R. R., and Machlan, L. A., Standard Reference

Materials: Uranium-235 Isotopic Abundance Standard Reference Materials for Gamma

Spectrometry Measurements, NBS Spec. Publ. 260-96 (In Preparation). Mavrodineanu, R. and Gills, T. E., Standard

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Taylor, J. K., Standard Reference Materials: Handbook for SRM Users, NBS Spec. Publ. 260-100 (September 1985). Mangum, B. W., Standard Reference Materials: SRM 1970, Succinonitrile Triple-Point Standard: A Temperature Reference Standard Near

58.08 °C, NBS Spec. Publ. 260-101 (March 1986).

Weidner, V. R., Mavrodineanu, R., Mielenz, K. D., Velapoldi, R. A., Eckerle, K. L., and Adams, B., Standard Reference Materials: Holmium Oxide

Solution Wavelength Standard from 240- 650 nm, SRM 2034, NBS Spec. Publ. 260-102 (In Press). Hust, J. G., Standard Reference Materials: Glass Fiberblanket SRM for Thermal Resistance, NBS

Spec. Publ. 260-103 (September 1985). SN003-

003-02687-5 Mavrodineanu, R. and Alvarez, R., Standard

Reference Materials: Summary of the Biological and Botanical Standards Issued by the National Bureau of Standards, NBS Spec. Publ. 260-104 (November 1985). Mavrodineanu, R. and Rasberry, S.D., Standard

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Standards Issued by the National Bureau of Standards, NBS Spec. Publ. 260-105 (March

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viii
TABLE OF CONTENTS

Preface iii

1. Introduction 1

2 . Experimental

2.1 Instrumentation 1 2.2 Materials

2.2.1 Holmium Oxide 2 2.2.2 Cells 2 2.3 Measurement Techniques

2.3.1 Calibration of the Spectrophotometer Wavelength Scale 2 2.3.2 Confirmation of Spectral Bandwidths 3 2.3.3 Determination of the Wavelengths of Minimum Transmittance 3 2.3.4 Accuracy of the Wavelengths of Minimum Transmittance 5 3. Measurements

3.1 Influence of the Blank Cuvette, Solvent and Water . 5 3.2 Influence of Temperature 6 3.3 Influence of Purity 6 3.4 Influence of Concentration 6 3.5 Influence of Spectral Bandwidth 7 4. Results

4.1 Transmittance of Holmium Oxide Solution 7 4.2 Selection of Useful Wavelengths of Minimum Transmittance 7 4.3 Numerical Data 7 4.4 Uncertainty of Measured Wavelengths 7 4.5 Comparison of Results with Measurements Made on NBS Reference

Spectrof luorimeter 7 4.6 Other Measurements Outside NBS

.

10 5. Conclusions 11 6. References 11

ix
APPENDICES

Page

A-l Standard Reference Materials for Spectrophotometry Provided

by the National Bureau of Standards 12 A-2 Certificates of Standard Reference Materials for Spectrophotometry

A-2.1 SRM 930D, Glass Filters for Spectrophotometry 18 A-2. 2 SRM 931c, Liquid Absorbance Standards for Ultraviolet and Visible Spectrophotometry 21 A-2. 3 SRM 932, Quartz Cuvette for Spectrophotometry 24 A-2. 4 SRM 935, Crystalline Potassium Dichromate for Use as an Ultraviolet Absorbance Standard 26 A-2. 5 SRM 936, Quinine Sulfate Dihydrate 30 A-2. 6 SRM 2010a, Didymium Glass Filter for Checking the Wavelength

Scale of Spectrophotometers 34 A-2. 7 SRM 2031 , Metal-on-Quartz Filters for Spectrophotometry 42 A-2 .8 SRM 2032, Crystalline Potassium Iodide: Heterochromatic

Stray Radiant Energy Standard for Ultraviolet Absorption

Spectrophotometry 46 A-2. 9 SRM 2033, Crystalline Potassium Iodide with Attenuator: Heterochromatic and Isochromatic Stray Radiant Energy Standard

for Ultraviolet Absorption Spectrophotometry 50 A-2. 10 SRM 2034, Holmium Oxide Solution Wavelength Standard From

240 to 640 nm 54

x
List of Tables Table No. Page

1. Ten cycles repetitive measurements of three holmium oxide transmittance minima 5 2. Influence of holmium oxide concentration on the wavelengths of minimum

transmittance 7 3. Results of holmium oxide solution analysis for transmittance minima 1 through 7 for spectral bandwidths of 0.1, 0.25, 0.5, 1, 2, and 3 nm 9 4. Results of holmium oxide solution analysis for transmittance minima 8 through 14 for spectral bandwidths of 0.1, 0.25, 0.5, 1, 2, and 3 nm 10 5. Comparison of values for holmium oxide transmittance minima with values obtained with the NBS Reference Spectrof luorimeter 10 6. Comparison of values for holmium oxide transmittance minima with values obtained by other workers 11 A-l. Standard Reference Materials for Spectrophotometry Provided by the National ' Bureau of Standards 12

List of Figures

Figure No. Page

1 . Wavelength scale calibration of the spectrophotometer 2 2. Spectral transmittance of a 4% solution of holmium oxide in 10% perchloric

acid in water 4 3. Graphical technique used to determine the transmittance minima from digital spectral transmittance data 5 4. Spectral transmittances of an empty fused silica cuvette, a cuvette filled with water, and a cuvette filled with a solution of 10% perchloric acid 6 5. Spectral differences of solutions prepared from holmium oxide specimens of 99.99% purity and 99.999% purity 6 6-19. Fourteen holmium oxide transmittance minima as a function of spectral bandwidth 8

xi

Holmium Oxide Solution

Wavelength Standard From 240

to 640 nm - SRM 2034

Victor R. Weidner, Radu Mavrodineanu, Klaus D. Mielenz, Ranee A. Velapoldi, Kenneth L. Eckerle, and Bradley Adams

National Bureau of Standards, Gaithersburg, MD 20899

Accepted: November 28, 1984 The work describes the methods and procedures used to determine the wavelengths of minimum trans- mittance of holmium oxide in perchloric acid solution. Measurements of specjral transmittance of the solutions were made by means of a high precision spectrophotometer over the wavelength range 200 nm to 680 nm. The

wavelength scale accuracy of this instrument was verified by extensive measurements of mercury and deuterium

emission lines. The measurements of spectral transmittance of the holmium oxide solutions were made as a function of temperature, purity, concentration, and spectral bandwidth. Analysis of the uncertainties associated with these parameters and the uncertainties associated with the calibration of the instrument wavelength scale and the data analysis have resulted in an estimated uncertainty of ±0.1 nm for the determination cf the wavelengths of minimum transmittance of the holmium oxide solution. Key words: holmium oxide; spectral bandwidth; spectrophotometer calibration; spectral transmittance; wavelength calibration; wavelength standard.

1. Introduction

This work describes the methods and procedures used

to determine the wavelengths of minimum spectral transmittance of holmium oxide (Ho2 0,) in perchloric

acid (HC104) solution in the spectral region 200 to 680 nm. The object of this activity was to develop a standard

for verifying the wavelength scale of uv/visible spec- trophotometers, and to provide assistance toward im- proving the accuracy of measurements in the fields of

About the Authors: Victor R. Weidner is with NBS' Radiometric Physics Division, headed by

Klaus D. Mielenz and served also by Kenneth L. Eckerle; Radu Mavrodineanu is associated with the Bureau's Inorganic Analytical Research Division as a reemployed annuitant; Ranee A. Velapoldi is deputy

director of the NBS Center for Analytical Chemistry; and Bradley Adams served the Bureau as a student worker.

molecular absorption spectrometry or spectrophoto- metry [l]

1 . Holmium oxide in a glass matrix has been issued by

the National Bureau of Standards (NBS) as a wavelength standard for the ultraviolet and visible spectrum

since 1961 [2]. Didymium glass wavelength standards have been issued since 1945. The didymium glass wavelength standards are available from NBS as Standard Reference Material 2009; 2010; 2013; and 2014 [3],

2. Experimental

2.1 Instrumentation Measurements of spectral transmittance of the hol- mium oxide solutions were made by means of a Varian Cary Model 2390 recording spectrophotometer2

.

'Numbers in brackets indicate literature references.

2 Certain commercial equipment or products are mentioned in this paper in order to adequately document the work. In no case does this imply that the equipment or product is being endorsed by NBS or that

it is necessarily the best equipment or product for the application.

1
The optical system of this double beam instrument

consists of a filter predisperser and a double-pass

double-sided grating monochromator. A deuterium lamp is used over the wavelength range 185 to 340 nm

and a tungsten-halogen lamp is used over the wavelength range 340 to 3150 nm as a source. The spectral bandwidths are selectable from 0.07 nm to 3.6 nm. Data

can be recorded by a digital readout system with ther- mal printer and an analog chart display.

water was produced by thermal distillation. The aque- ous solutions of holmium oxide in 10% perchloric acid were prepared by weighing 2, 4, or 6 g of the oxide and

adding 10 mL of distilled water and 10 mL of perchloric

acid. The holmium oxide was dissolved by heating at about 80 °C for one hour. The clear solution was trans- ferred quantitatively to a 100 mL volumetric flask and was brought to volume with distilled water at room

temperature.

2.2 Materials

2.2.1 Holmium Oxide The holmium oxide solutions were prepared by dis- solving the powder in a 10% perchloric acid in distilled water. The purity of the holmium oxide specimens used

in the preparation of these solutions was indicated by the manufacturer [4] to be 99.99% (Lot No. Ho-0-4-007) and 99.999% (Lot No. Ho-O-5-007). Solutions were pre- pared with 2%, 4%, and 6% holmium oxide. These

solutions were placed in 10 mm pathlength nonfluorescent fused silica cuvettes. The actual form in which Ho is formed when Ho2 03 is dissolved in HC104 is that of an aquo ion of the general formula Ho(H2 0)n + . The term "holmium oxide" and

the spectral transmittances reported in the manuscript

refer to this chemical species. Aqueous solutions of

perchloric acid are used in this study to dissolve Ho2 03 since the resulting aquo ion is least likely to form complexes when subjected to changes in temperature and

concentration [5]. The holmium oxide powder is stated by the manufacturer to have an average particle size of about 2 mi- crometers. The perchloric acid was a nominal 70-72%

reagent grade (considered here as 100%). The distilled

2.2.2 Cells The cells used for the transmission measurements of

the holmium oxide solutions were conventional nonfluorescent, fused silica, cuvettes with a nominal path- length of 10 mm. These cuvettes were provided with graded quartz-to-pyrex tubes with rubber caps.

2.3 Measurement Techniques

2.3.1 Calibration of the Spectrophotometer Wavelength Scale The spectophotometer wavelength scale error was

evaluated by measuring the emission spectrum of the instrument's deuterium lamp and the emission spectrum

of a mercury pen lamp [6,7,8]. The wavelength calibration was performed at the be- ginning of the holmium oxide solution measurements

and again at the completion of the measurements. A

number of emission lines of mercury and two emission

lines of deuterium were used over the wavelength range 230 nm to 690 nm (see fig. 1). The wavelength scale errors were determined for spectral bandwidths of 0.

1

nm, 1 nm, 2 nm, and 3 nm. Each emission line was scanned at a rate of 0.01 nm

per second and recorded on a scale of 0.2 nm per centi200

WAVELENGTH SCALE CALIBRATION O MERCURY EMISSION LINES X DEUTERIUM EMISSION LINES

jg So.

Figure 1-Wavelength scale cali- bration of the spec- trophotometer.

300 400 500 WAVELENGTH (nm) 600 700

2
meter. The recorded emission peaks were bisected, us- ing a proportional divider, to determine the wavelengths at the center of the recorded triangular lines. Using this technique, the wavelength scale was read to the nearest 0.01 nm with a precision of ±0.005 nm. The

differences between the measured wavelengths of mer- cury emission lines and the true wavelengths are plotted

in figure 1. A linear least squares fit of these wavelength

differences for the two dates July 18 and August 9 (also shown in fig. 1) was used to correct the measured values of the holmium oxide transmission minima for errors in the wavelength scale of the instrument. The wavelength error of the instrument was essentially the same for spectral bandwidths less than 1 nm. However, at spectral bandwidths of 2 nm and 3 nm, the wavelength error was slightly different and a different correction was required. The deuterium lamp emission lines were measured at two wavelengths each day during the holmium oxide

solution characterization to verify the accuracy of the wavelength scale. These measurements showed that the

calibration of the wavelength scale is constant to ±0.02 nm after a nominal warm-up of one hour. These results, as well as the repeatability of the calibration with the mercury line source, indicate that the overall stability of

the instrument wavelength scale was better than ±0.05 nm during the period of time required to complete the wavelength characterization of the holmium oxide solution. The mercury pen lamp is mounted in the lamp posi- tioning device that ordinarily holds the deuterium lamp

of the spectrophotometer. The arc tube of the mercury

pen was aligned parallel to the entrance slit of the monochromator. The lamp holder is equipped with screw

adjustments for vertical and horizontal alignment of the source. The entrance slit cannot be directly observed. Therefore, the source was adjusted with instrument

operating in the single-beam mode until a maximum sig- nal is observed. To test the effect of the positioning of

the mercury line source on the observed emission line maxima, the pen lamp was moved horizontally across

the field of view of the entrance slit to the monochromator in approximately 0.22 mm steps for a total of

12 steps or a 2.64 mm distance. The results of this experi- ment showed that the recorded emission maxima varied by less than ±0.01 nm for lamp positions within ± 1 mm

of the center position. The center position corresponded

to the position of maximum signal.

2.3.2 Confirmation of Spectral Bandwidths The mercury line source was used to confirm the

spectral bandwidth settings of the spectrophotometer. The mercury emission line at 435.8 nm was scanned for spectral bandwidths of 0.1 nm, 0.25 nm, 0.5 nm, 1 nm, 2

nm and 3 nm. The emission peak was normalized to 100% on the chart recorder by adjusting the instrument

gain. The bandwidth at half peak height is approxi- mately equal to the spectral bandwidth. The natural bandwidth of the emission line is much less than the instrument bandwidth. The recorded curve has a trian- gular symmetry for all settings of the monochromator

slitwidths. For the above-mentioned nominal spectral bandwidth settings of the spectrophotometer, the measured spectral bandwidths were 0.092 nm, 0.228 nm,

0.468 nm, 1.04 nm, 2.18 nm, and 3.20 nm, respectively. This technique for determining spectral bandwidths has some uncertainties due to assumptions made. However,

it serves to confirm that the desired spectral bandwidths

are closely approximated when the instrument is pro- grammed to provide those settings; hence the effect on

the transmittance minima is negligible.

2.3.3 Determination of the Wavelengths

of Minimum Transmittance The spectral transmittance of holmium oxide in an aqueous solution of perchloric acid exhibits many ab- sorption bands in the ultraviolet and visible spectrum. The spectrum is shown in figure 2 for a 0. 1 nm spectral bandwidth scan. The total number of observed absorption bands varies as a function of the spectral bandwidth

used during the recording of the spectrum. There are approximately 14 major absorption features or bands between 200 and 650 nm that can be observed clearly for a wide range of spectral bandwidth settings. Most of the major absorption bands have lesser bands between them

or in close association. These smaller bands are better resolved at bandwidths less than 1 nm. Only the major

absorption bands that could be of use as possible wavelength standards were selected for detailed study. The

various parameters affecting the measured wavelengths

of minimum transmittance of the holmium oxide solu- tion are discussed in section 3. These include such pa- rameters as temperature, purity, concentration, and

spectral bandwidth. The spectral transmittance of the holmium oxide solu- tion was digitally recorded on a thermal printer at 0.1 nm intervals with the monochromator scanning at a rate of 0.05 nm/s. The transmittance was simultaneously recorded on a chart with a wavelength display of 0.5 nm/cm. The holmium oxide solution was contained in a 10 mm pathlength fused silica cuvette. The transmittance of the solution in this cuvette was measured relative to an air-only path in the reference beam. The determination of the wavelengths of the trans- mittance minimum of the holmium oxide solution was

derived from an analysis of the recorded digital output. The 0.1 nm interval transmittance data were plotted on

3
(%) aoNviiiwsNvai

4
graph paper on a scale of 0.1 nm per cm with subdivisions of 0.01 nm per mm so that the wavelength

interval of this plotted digital data could be read to the

nearest 0.01 nm between the measured data points. The

location of the wavelength of minimum transmittance

for a given holmium oxide band was determined graphically (fig. 3) by drawing a curve through the data

points and bisecting the horizontal grid lines between

the two slopes of the curve representing the absorption

feature. Several of these bisection points locate the line between the two slopes that intersects the minimum

transmittance point, (usually at the lowest point of the

curve). The wavelength at this point of intersection was

taken as the measured wavelength of minimum trans- mittance for the absorption feature. The true wavelength of the minimum was determined by applying a wavelength correction to the instrumental wavelength

scale, as determined in section 2.3.1.

2.3.4 Accuracy of the Wavelengths of Minimum Transmittance The overall uncertainty in the location of the wavelengths of minimum transmittance is believed to be no

greater than ±0.1 nm at the 95% confidence limit. This

conclusion is based on the reproducibility of the following calibration procedures:

}i Bl SEC riON OF C JRVE t

\ --1

\

PL0 r of

D

(0.1 GITAL nm IN DAT/ TERV/ L) I, VWAVE

MININ LENGIUM m oc

TRAN SMIT "ANCE

WAVELENGTH (nm)

Figure 3-Graphical technique used to determine the transmittance minima from digital spectral transmittance data.

• The uncertainty of the calibration of the instru- ment wavelength scale using the mercury and deu- terium lamps, and the long-term and day-to-day in- stabilities of the instrument wavelength scale ( l ess than ±0.05 nm).

• The imprecision of the graphical technique for deriving the measured wavelengths of min- imum transmittance. (±0.02 nm).

• The dependence of the measured wavelengths

of minimum transmittance on variations in temperature or concentration of the solution. (±0.02 nm). These uncertainties have been discussed in section 2.3.1. The imprecision of the graphical technique is illustrated

in table 1, where data are shown for three absorption

features. Ten sets of digital results were produced by the instrument for each of these features. The digital data were plotted and the wavelengths of minimum trans- mittance for each absorption feature were determined

for the 10 sets of data by the graphical technique. The

standard deviation and standard error for the 10 deter- minations is also given in table 1.

3. Measurements

3.1 Influence of the Blank Cuvette, Solvent, and Water The spectral transmittances of an empty fused silica cuvette, a cuvette filled with distilled water, and a

Table 1. Ten cycle repetitive measurements of three holmium

oxide transmittance minima. Listed minima are obtained by graphical techniques, using the digitally recorded

0.1 nm interval transmittance measurement.

(spectral bandwidth = 0.1 nm) Minima Minima Minima

Cycle No. 1 No. 12 No. 14

1 240.88 nm 485.08 nm 640.28 nm

2 240.87 485.10 640.30

3 240.86 485.11 640.30

4 240.84 485.11 640.30

5 240.85 485.10 640.29

6 240.84 485.11 640.30

7 240.85 485.11 640.29

8 240.85 485.11 640.30

9 240.84 485.10 640.30

10 240.85 485.11 640.29

Average: 240.853 485.104 640.295 Standard

Deviation: 0.0134 0.0097 0.0071 Standard

Error: .0042 .0031 .0022

Note: The d ata shown in this table have not been corrected for the wavelength scale error of the spectrophotometer.

5
cuvette filled with the diluted perchloric acid (without holmium oxide) are illustrated in figure 4. These measurements are relative to an air path in the reference beam. Measurements of the wavelength of minimum trans- mittance for the band at 241 nm were made with the holmium oxide in perchloric acid solution versus a cuvette containing only the perchloric acid in the refer- ence beam. The wavelength of minimum transmittance of this band was found to be the same when the holmium

oxide solution was measured relative to air in the refer- ence beam and when it was measured relative to a cuvette containing the perchloric acid solution. Since

the 241 nm band is within the spectral range showing a slope in the transmittance of the cuvette-perchloric acid

spectra, (see fig. 4) it was considered to be the band most

likely to be influenced by this slope. However, no measurable influence was detected in the location of the wavelength of minimum transmittance of this band due

to these spectral features associated with the solvent or

cuvette.

3.2 Influence of Temperature The wavelengths of minimum transmittance of the holmium oxide solution were determined at 20 °C, 25 °C, and 30 °C for spectral bandwidths of 0.1 nm and

1 nm. If there is a temperature-related influence on the

location of the wavelengths of minimum transmittance,

it was not detected within these temperature ranges. The measured differences were attributed to random

uncertainties.

100

l40r

<

a.

X

Water filled quartz cuvette

Empty quartz cuvette

/ 10% perchloric acid

/' in quartz cuvette

200 300 400 500 600 WAVELENGTH (nm)

Figure 4-Spectral transmittances of an empty fused silica cuvette, a cuvette filled with water, and a cuvette filled with a solution of 10%

perchloric acid in water.

3.3 Influence of Purity Complete spectral scans of solutions made with the 99.99% and 99.999% purity holmium oxides showed no

spectral differences except in the extreme ultraviolet cut-off at wavelengths less than 230 nm. The differences are illustrated in figure 5 for the wavelength range 200

to 300 nm. The wavelengths of the minimum trans- mittances for the 14 selected absorption bands were

found to be the same for solutions prepared from these two lots of holmium oxide. 100

Holmium Oxide Purity 99.999 r \ I W

A i

' ./

200 250 WAVELENGTH (nm] 300

Figure 5-Spectral differences of solutions prepared from holmium

oxide specimens of 99.99% purity and 99.999% purity.

3.4 Influence of Concentration The location of the wavelengths of minimum trans- mittance of the holmium oxide solution as a function of concentration was tested with concentrations of 2%,

4%, and 6% in the perchloric acid solution. The general

spectral scan indicated that the changes in concentration

affected the measured transmittance as would be ex- pected but did not influence the location of the trans- mittance minima. To verify this further, three of the bands were evaluated by the graphical technique de- scribed in section 2.3.1. The results of these concentration measurements for these bands are shown in table 2.

6
Table 2. Influence of holmium oxide concentration on the wavelengths of minimum transmittance.

(spectra 1 bandwidth = 0.1 nm) Holmium oxide Minima Minima Minima

concentration No. 1 No. 12 No. 14

2 % 240.84 nm 485.11 nm 640.30 nm

4 % 240.86 485.11 640.32

6 % 240.84 485.12 640.31

Note: The data shown in this table have not been corrected for the wavelength scale error of the spectrophotometer.

3.5 Influence of Spectral Bandwidth The wavelengths of minimum transmittance of the holmium oxide solution were determined for spectral bandwidths of 0.1 nm, 0.25 nm, 0.5 nm, 1 nm, 2 nm, and

3 nm. Measurement of the instrumental spectral band- widths is discussed in section 2.3.2. The influence of

spectral bandwidth was by far the most important pa- rameter affecting the location of the measured wavelengths of minimum transmittance. The results of this study are shown in figures 6 through 19 for the 14 min- ima identified in figures 2-1, 2-2, and 2-3. The data for bandwidth effects are also listed in tables 3 and 4. The

measurements indicate that for most of the holmium

oxide bands, the location of the wavelengths of min- imum transmittance does not change significantly for spectral bandwidths of less than 1 nm. From these data

it can be seen that a 0.1 nm spectral bandwidth is ade- quate to define the wavelengths of minimum trans- mittance within the stated uncertainties. For some bands

the location of the minimum transmittance shifts only

slightly for spectral bandwidths greater than 1 nm. However, many do show large shifts for larger band- width settings. These results indicate that for instru- ments with spectral bandwidth settings of less than

1 nm, the holmium oxide solution can serve as an excellent wavelength standard. For instruments having band- width settings between 1 nm and 3 nm the standard can

still be of use if the instrument bandwidth is known.

manuscript as a key to associate the data in the tables with the spectral features illustrated in the figures.

4.2 Selection of Useful Wavelengths

of Minimum Transmittance The selection of holmium oxide bands that are consid- ered useful for calibration purposes was based on the

influence of spectral bandwidth on the location of these minima. The transmittance minima of small side bands

associated with major absorption features usually shift in wavelength with bandwidth setting or are not re- solved over the normal instrumental bandwidth range. The 14 major absorption bands are listed in tables 3 and

4. The absorption bands not listed in the tables are not considered useful for wavelength calibration purposes.

4.3 Numerical Data The wavelengths of minimum transmittance of the 4% holmium oxide solution are listed in tables 3 and 4

for six spectral bandwidths. The results of the measurements as a function of temperature are also listed for

0.1 nm and 1 nm spectral bandwidths at temperature

settings of 20 °C, 25 °C, and 30 °C. The shift in wavelengths of minimum transmittance as a function of spectral bandwidth is shown in figures 6 through 19 for the 14 selected minima. The recommended values of minimum transmittance are listed in table

3 and 4 for the measurements made at 25 °C.

4.4 Uncertainty of Measured Wavelengths The uncertainties associated with the data listed in tables 3 and 4 have been discussed in section 2.3.4. The

uncertainty in the determination of the wavelengths of minimum transmittance for the holmium oxide solution

is believed to be no greater than ±0.1 nm at the 95%

confidence limit using the instrumentation and tech- niques described in this paper.

4. Results

4.1 Transmittance of Holmium Oxide Solution The general spectral signature of the holmium oxide

solution is illustrated in figures 2-1, 2-2, and 2-3 for a

spectral bandwidth of 0. 1 nm. Some of the finer spectral features shown in these figures will be absent when the spectrum is recorded at bandwidths greater than 1 nm. The major transmittance minima selected for this study

are indicated by numbers 1 through 14 as shown in these

figures. These band numbers are used throughout the

4.5 Comparison of Results with Measurements Made on the NBS Reference Spectrofluorimeter The wavelengths of minimum transmittance of

several absorption bands of holmium oxide solution were determined by analysis of spectral data obtained with the NBS Reference Spectrofluorimeter [9]. This

reference instrument is primarily designed to be used as a research tool for high accuracy spectral analysis of

fluorescent materials and in the development of stan- dards for use in this area of research. The versatile design of the instrument allows for its use as a high accu7
Figures 6-19—Fourteen holmium oxide transmittance minima

function of spectral bandwidth.

3339

333.8 333.7 - A

333-6

, 333.5 nm)

333.4 - 3333 - 333,2

333.1

HOLMIUM OXIDE MINIMA NO. 5

SPECTRAL BANDWIDTH (nm)

.25 .5 lp 2.0 SPECTRAL BANDWIDTH (nm) SPECTRAL BANDWIDTH (nm)

8
Minimum

No. Temp.(°C)

Spectral Bandwidths

0.1 nm 0.25 nm 0.5 nm 1 nm 2 nm 3 nm

20 240.99 nm 241.13 nm

1 25 240.99 240.97 nm 241.01 nm 241.13 241.08 nm 240.90 nm

1 30 240.99 241.15

2 20 249.79 249.88

2 25 249.83 249.78 249.79 249.87 249.98 249.92

2 30 249.79 249.86

3 20 278.14 278.09

3 25 278.15 278.14 278.13 278.10 278.03 278.03

3 30 278.14 278.09

4 20 286.99 287.17

4 25 287.01 287.00 287.01 287.18 287.47 287.47 4 30 287.01 287.18

5 20 333.48 333.45

5 25 333.47 333.44 333.43 333.44 333.40 333.32

5 30 333.48 333.45

6 20 345.57 345.47

6 25 345.55 345.55 345.52 345.47 345.49 345.49

6 30 345.62 345.49

7 20 361.38 361.33

7 25 361.36 361.35 361.33 361.31 361.16 361.04

7 30 361.38 361.31

Note: The uncertainty in the wavelengths of minimum transmittance is ±0.1 nm. An extra decimal place is given for rounding purposes.

9
Table 4. Results of holmium oxide solution analysis for transmittance minima 8 through 14 for spectral bandwidths of 0.1, 0.25, 0.5, 1, 2, and 3 nm. 4% holmium oxide in a 10% perchloric acid solution. Minimum Temp. Spectral Bandwidths

No. (°C) 0. 1 nm 0 25 nm 0.5 nm 1 nm 2 nm 3 nm

8 20 385.45 nm 385.66 nm

8 25 385.45 385.42 nm 385.50 nm 385.66 385.86 nm 386.01 nm

8 30 385.44 385.68

9 20 416.10 416.27

9 25 416.07 416.07 416.09 416.28 416.62 416.84

9 30 416.13 416.30

10 20 451.30

10 25 * 451.30 451.30 451.24

10 30 451.34

11 20 467.83 467.84

11 25 467.82 467.82 467.80 467.83 467.94 468.07

11 30 467.84 467.84

12 20 485.30 485.29

12 25 485.28 485.28 485.27 485.29 485.33 485.21

12 30 485.31 485.30

13 20 536.53 536.65

13 25 536.54 536.53 536.54 536.64 536.97 537.19

13 30 536.45 536.63

14 20 640.48 640.52

14 25 640.51 640.49 640.49 640.52 640.84 641.05

14 30 640.52 640.49

* Split ; into 2 minima for spectral bandwidths less than Note: The uncertainty in the weivelengths of minimum transmittance is ±0.1 nm. An extra decimal place is given for rounding purposes.

racy spectrophotometer in some applications. The

wavelength scale of the spectrofluorimeter has been

carefully calibrated by extensive measurements of emission line sources and is known to have an uncertainty of ±0.1 nm for spectral bandwidth of 0.1 nm.

This reference instrument was used to confirm the

results obtained with the calibrated high-precision commercial spectrophotometer used for the holmium oxide measurements. A comparison was made to confirm the

results for three of the transmittance minima at one spectral bandwidth setting. The results of this comparison

are shown in table 5. The two instruments provided data

for these three transmittance minima that agree to within 0.1 nm. The wavelength scale uncertainty for both instruments is ±0.1 nm.

4.6 Other Measurements Outside NBS

A list of the wavelengths of minimum transmittance of the holmium oxide solution reported by other workers is given in table 6. (Ref. 10 offers details of these measurements.)

Table 5. Comparison of values for holmium oxide

transmittance minima with values obtained with

the NBS Reference Spectrofluorimeter.

(spectral bandwidth = 0.;1 nm) Minima Minima Minima

Instrument No. 1 No. 7 No. 14 Varian (Cary) 240.995 nm 361.361 nm 640.507 nm

Model 2390 NBS Reference 240.970 nm 361.313 nm 640.469 nm

Spectrofluorimeter

The data shown in table 6 indicate that workers in other laboratories are in generally good agreement with one another and that the NBS data also agree well with

these workers' previously published data. These workers also found that the wavelengths of minimum trans- mittance of holmium oxide in similar solution in perchloric acid are not sensitive to variations in temperature and concentration. They also concluded that the wavelengths of minimum transmittance were least affected by changes in spectral bandwidth for band10
Table 6. Comparison of values for holmium oxide

transmittance minima with values obtained by other workers (see Reference 10). NBS

Min. Transmittance —— Minima (1) (2) (3) (4)

1 240.99 nm* 241.15 nm 241.0 nm 241.1 nm 241.1 nm

2 249.83 * 249.75 250.0 249.7 249.7

3 278.15 * 278.2 277.8 278.7 278.2 4 287.01 * 287.15 287.5 287.1 287.2

5 333.47 * 333.5 333.3 333.4 333.3

6 345.55 * 345.6 345.5 345.5 345.0

7 361.36 * 361.5 361.0 361.5 361.2

8 385.45 * 385.6 385.6 385.5 385.6

9 416.07 * 416.2 416.0 416.3 416.6

10 451.30 # 450.7 450.4 450.8 451.0

11 467.82 467.75 468.0

12 485.28 485.25 485.2 485.8 485.2

13 536.54 536.3 536.8

14 640.51 640.5

* Spectral bandwidth = 0.1 nm

# Spectral bandwidth = 1 nm widths less than 1 nm, but that large shifts can be en- countered at bandwidths in excess of 1 nm.

5. Conclusions The reported wavelengths of minimum transmittance of the holmium oxide solution appearing in tables 3 and

4 are estimated to be uncertain by no more than ±0.1 nm at the 95% confidence limit. These wavelengths of minimum transmittance were found to be essentially unaffected by changes in temperature at 25 °C ±5 °C. They were also unaffected by variations in the concentration for solutions containing 2%, 4%, and 6% hol- mium oxide. The critical parameter affecting the measured values of minimum transmittance was found to be

the spectral bandwidth setting of the spec- trophotometer. For spectral bandwidths less than 1 nm

the wavelength shift is generally less than 0.2 nm. Users can most effectively determine the wavelength error

associated with their instrument by using the NBS data

listed in tables 3 and 4 that are representive of the spec

tral bandwidth setting ordinarily used with the instru ment. The wavelengths of minimum transmittance of

the holmium oxide solution for spectral bandwidths

greater than 3 nm have not been evaluated.

The authors gratefully acknowledge the assistance of Chenq-Tsong Chang, guest worker from Taiwan, for

his contribution in measuring the transmittance minima

of the holmium oxide solution on the NBS Reference

Spectrofluorimeter; Jack J. Hsia, for constructive dis- cussions; Robert W. Burke, for assistance in the preparation of various Ho2 0, solutions; and the NBS Optical Shop for preparation of the fused silica cuvettes.

6. References

[1] The terminology used in this work was defined earlier by K. D.

Mielenz in Anal. Chem. 48, 1093 (1976).

[2] Keegan, H. J.; J. C. Schleter and V. R. Weidner, Ultraviolet Wavelength Standard for Spectrophotometry, J. Opt. Soc. Am. 51, 1470 (1961), (abstract).

[3] Venable, W. H., Jr., and K. L. Eckerle, Standard Reference

Material: Didymium Glass Filters for Calibrating the Wavelength Scale of Spectrophotometers (SRM 2009,

2010, 2013,2014).

[4] The holmium oxide was obtained from Research Chemicals, a Division of Nucor Corp., Phoenix, Arizona.

[5] Gschneider, K. A., Jr., and L. E. Yring, Handbook of the Physics and Chemistry of Rare Earths, Vol. 3 North-Holland

(1979).

[6] Harrison, G. R., MIT Wavelength Tables, MIT Press, Cambridge, MA (1960).

[7] ASTM Manual on Recommended Practices in Spectrophotometry, Published by American Society for Testing and

Materials, 1916 Race St., Philadelphia, PA 19103 (1969).

[8] CRC Handbook of Chemistry and Physics, 63d Edition, CRC

Press, Inc., (1982-1983).

[9] Mielenz, K. D., in "Measurement of Photoluminescence" (K. D.

Mielenz, Editor), pp 17-19, Academic Press (1982).

[10] Burgess, C, and A. Knowles, Eds. Standards in Absorption

Spectrometry, Chapter 7, Wavelength Calibration, Chapman and Hall, London (1981).

11
Appendix A-l . Standard Reference Materials for Spectrophotometry Provided by the National Bureau of Standards.

Material Composition

Solid Filters

930 Glass Filters for Spectrophotometry

Solid filters made of Schott

NG-4 and NG-5 optically

neutral glass. Obtained from

the Schott-Jenaer Glaswerk,

Mainz, Germany.

Three filters with nominal transmittances of 10, 20, 30%. Each filter is mounted in a black anodized aluminum holder

provided with front and rear shutters. The filters are stored in a cylindrical aluminum container.

2031 Metal-on-Quartz

Filters for Spectrophotometry

Solid filters made of semi- transparent evaporated chromium-on-fused silica (non-fluorescent) plates.

Three filters with nominal transmittances of 10, 30, 90%. Each filter is made from two fused silica plates assembled

by optical contact. The 90% filter is made by assembling 2 clear plates. The 10% and 30% filters are made by assembling

a fused silica plate which

carries a film of semitrans- parent chromium to produce the desired transmittance, and a clear plate. Each filter assembly is placed in a metal holder provided with shutters.

Liquids and Cuvettes

931b Liquid Absorbance

Standards for Ultraviolet

and Visible Spectrophotometry

Liquid filters made from a solution of Co and Ni metals dissolved in a mixture of nitric-perchloric acids. The

pH of the solution is about 1

.

Prepared in the NBS Center for Analytical Chemistry.

Three solutions and a blank were delivered in sealed ampoules and have nominal absorbances of 0.1 to 0.9.

935 Crystalline Potassium

Dichromate for Use as an Ultraviolet Absorbance

Standard

Crystalline potassium

dichromate of established

purity obtained from the

J. T. Baker Chemical Co., Phillipsburg , New Jersey.

The crystalline material of reagent grade purity is offered in glass bottles provided with plastic screw

caps.

12
Certification Use Remarks

The transmittance of each filter is measured with the high-accuracy spectrophotometer at X 440, 465, 546.1,

590, 635 nm, using spectral handpasses of 2.2, 2.7, 6.5,

5.4, 6.0 nm respectively.

This SRM is intended as a reference source for the verification of the trans- mittance and absorbance

scales of conventional spectrophotometers

The use of this SRM is limited

to the visible spectrum and requires narrow spectral bandpasses. For further

details, consult the Certificate included in the Appendix; see also NBS Special Publication 260-51 .

The transmittance of each filter is measured with the high-accuracy spectropho- tometer at A 250, 280, 340, 360, 400, 465, 500, 546.1,

590, 635 nm.

This SRM is intended as a reference source for the verification of the trans- mittance and absorbance

scales of conventional spectrophotometers in the ultraviolet and visible

spectral region.

SRM 2031 has 'good optical

neutrality and can be used to calibrate spectrophotometers with wide spectral bandpasses

from about 200 to 800 nm (with possible extension to A =3 ym).

For further details, consult

the Certificate in the Appendix; see, also NBS Special Publication 260-68.

The absorbance of each solu- tion was measured at A 302, 395, 512, 678 nm using

spectral bandpasses of 1.0

1.7, 2.0, 6.5 nm respectively. The certification is made with an uncertainty of about +1.0%.

This SRM is primarily

intended for the verification

of the accuracy of transmittance or absorbance scales

of spectrophotometers.

Requires the use of SRM 932

and of narrow spectral bandpasses. Provides only one certified value in the ultraviolet. For further details

consult the Certificate

included in the Appendix.

The apparent specific absorbance is certified for five concentrations at A 235, 257, 313, 345, 350 nm using

spectral bandpasses of 1.2, 0.8, 0.8, 0.8, 0.8 nm

respectively, using SRM 932. further details, consult the Certificate included in the Appendix; see also NBS Special Publication 260-54.

This SRM is intended to be used as a reference standard

for the verification of the accuracy and linearity of the absorbance scale of spectrophotometers.

Requires accurate preparation

of solutions of potassium

dichromate in 0.001N perchloric acid. Requires the use of SRM 932 and of narrow spectral

bandpasses. Can be used only

in the ultraviolet. For

13
Appendix A-l. Continued.

Composition

932 Quartz Cuvette for SpectrophotometryAll-quartz cuvette made of non-fluorescent fused silica

of optical quality.

Each cuvette is made of fused silica and is provided with a Teflon stopper. The trans- parent windows are attached

to the body of the cuvette by direct fusion. The cuvettes are stress-relieved by proper annealing. The cuvette is stored in a transparent plastic container.

Stray Light

2032 Potassium Iodide for Use

as a Stray Light Standard

Crystalline potassium

iodide of established

purity, obtained from the

J. T. Baker Chemical Co., Phillipsburg , New Jersey.

The reagent-grade, crystalline

KI is 99.8% pure as indicated

by the manufacturer. Moisture

is 0.007%. Homogeneity was determined by absorbance measurements at 265, 267, and 270 nm, and was found adequate

,

2033 Potassium Iodide for Use

as a Stray Light Standard with Radiation Attenuator

Crystalline potassium iodide

of established purity, and two semi-transparent evaporated metal-on-fused silica filters contained in a metal holder provided with shutters. The

KI was obtained from the

J. T. Baker Chemical Co., Phillipsburg, New Jersey. The filters and the holder were

made by the NBS Instrument Shop.

Potassium iodide as for SRM 2032. Two semi- transparent evaporated chromium-on-fused silica (non-fluorescent) filters of optical quality.

Wavelength

2009 Didymium Glass Filter for Checking the Wavelength

Scale of Spectrophotometers

The didymium glass was prepared by Corning Glass

Works, Corning, New York,

as Corning 5120 Filter

Glass

.

Rare earth oxides in a glass matrix. This filter is 1 cm wide, 3 cm high, and 3 mm

thick. Each filter is placed

in a metal holder which fits into the cuvette holder of the spectrophotometer.

2010 Didymium Glass Filter for Checking the Wavelength

Scale of Spectrophotometers

Same as SRM 2009. Rare earth oxides in a glass

matrix. This filter is placed

5.1 cm square and 3 mm thick.

14
Certification Use Remarks

The nominal inner pathlength

is 10 mm and it is certified

at 10 points along the height

of the transparent windows with an uncertainty of +0.0005 mm. The cuvettes are

12.5 mm square and 48 mm high.

To be used when accurate transmittance or absorbance measurements are made on liquid samples. Should be used in conjuntion with

SRM's 931, 935, 2032, and 2033.

For further details, consult

the Certificate included in

the Appendix; see also NBS Special Publication 260-32.

The specific absorbances were measured with the high- accuracy spectrophotometer at 240, 245, 250, 255, 265, 270, and 275 nm at 23.5 °C using a spectral bandpass of 0.2 nm. The measurements were performed

using SRM 932 quartz cuvettes.

SRM 2032 is to be used to assess heterochromatic stray

light in the ultraviolet

region below 260 nm, in absorption spectrophotometers. It is recommended

that SRM 932 be used in

the measurements.

SRM 2032 should be stored in

the original, low-actinic

glass bottle and cardboard

container, protected from exposure to light and humidity. The estimated

stability is 3 years.

Same as for SRM 2032. The transmittance of the evaporated metal-on- fused silica filters was measured

at 255 nm with the high- accuracy spectrophotometer.

The nominal value is 10% for each filter, and a combined value of 1%.

SRM 2033 is to be used to assess heterochromatic and isochromatic stray light in absorption spectrophotometers.

Same as for SRM 2032. The

two semi-transparent

evaporated metal-on-fused

silica filters in the metal holder should be stored in the plastic container

provided with SRM 2033.

The wavelengths of maximum

absorption were determined with a high-precision spec- trophotometer for bandwidths in the range 1.5 to 10.5 nm

and for 14 to 24 wavelengths

in the range 400 to 760 nm. The instrument has a wave- length accuracy of 0.04 nm.

The filters are to be used

in calibrating the wavelength

scale in the visible spectral region for spectrophotometers

having nominal bandwidths in

the range 1.5 to 10.5 nm.

SRM 2009 was not measured

individually. It is recommended for most applications. For further

details, consult NBS Special Publication 260-66.

Same as SRM 2009. Same as SRM 2009. Same as SRM 2009.

15
Appendix A-l . Continued.

Composition

2013 Same as SRM 2009. Same as SRM 2009. Didymium Glass Filter for Checking the Wavelength

Scale of Spectrophotometers

2014 Same as SRM 2009. Same as SRM 2009. Didymium Glass Filter for Checking the Wavelength

Scale of Spectrophotometers

2034 Holmium Oxide for Use as Wavelength Standard for Spectrophotometry

Holmium oxide of established purity dissolved in perchloric

acid.

Holmium oxide is offered

in solutions in sealed

10 mm quartz cuvettes.

Fluorescence

936 Quinine Sulfate Dihydrate

The quinine sulfate dihydrate

was a special lot of material

obtained from J. T. Baker

Chemical Co., Phillipsburg

,

New Jersey.

SRM 936 contains 1 .7% impurities determined by liquid chromatography and believed to be dihydroquinine

sulfate dihydrate. The water

content is 4.74 _+ 0.05% determined by the Karl Fisher method and 4.57 + 0.04% by weight loss. Theoretical

value is 4.60%.

NOTE : For further scientific information concerning the following Standard Reference Materials, write or call at the National Bureau of Standards, Gaithersburg , MD 20899: SRM's 930 , 931 , 932 , 935 , 936 , 2030 , 2031 , 2032 , and 2033 : Dr. R. W. Burke, Inorganic Analytical Research Division, Chemistry Building, Room B222. Phone: 301-921-2141. SRM's 2009 , 2010 , 2013 , and 2014 : Mr. K. L. Eckerle, SRM 2034 : Mr. V. R. Weidner, Radiometric Physics

Division, Center for Radiation Research, Metrology Building, Room A321. Phone: 301-921-2791;

for scientific information concerning physical parameters involved in spectrophotometry and luminescence measurements: Dr. K. D. Mielenz, Chief, Radiometric Physics Division, Center

for Radiation Research, Metrology Building, Room B304. Phone: 301-921-3864. For information concerning the availability and purchase of the SRM's discussed in this paper contact: Office of Standard Reference Materials, Chemistry Building, Room B311. Phone: 301-921-2045. The NBS Publications discussed in this paper can be purchased from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20034. Please write for information concerning availability, delivery, and price.

16
Certification Rema rks

Each filter was measured separately; hence the data provide a more accurate representation of the optical properties of the individual filter.

Same as SRM 2009. SRM 2013 was measured individ- ually and should be used when

assurance in the evaluation of an instrument's wavelength

scale is highly critical . For further details, consult NBS Special Publication 260-66.

Same as SRM 2013. Same as SRM 2009. Same as SRM 2013.

The wavelengths of maximum absorption of holmium oxide solutions in perchloric

acid is determined for various spectral bandpasses

at the nominal wavelengths

241, 250, 278, 287, 333,

345, 361, 385, 416, 451, 467, 485, 536, 640 nm.

This SRM is to be used as a reference standard for the verification of the accuracy

of the wavelength scale of absorption spectrometers, in

the ultraviolet and visible

spectral regions.

Holmium oxide solutions in perchloric acid were selected

as a wavelength standard

because the absorption bands are narrower than those of the holmium oxide glass.

The material is certified for the relative molecular emis- sion spectrum E(A), in radio- metric units for a solution of

1 .28 x

10" 6 mol/L in 0.105 mol/L perchloric acid, using an excitation wavelength of 347.5 nm. The certified values of the molecular emis- sion spectrum at 5 nm

intervals from 375 to 675 nm

are given. This certification

was made with the NBS reference fluorescence spectrometer.

For evaluation of methods and

the calibration of fluores- cence spectrometers. A

solution of 0.1 mg/mL in 1000 mL 0.105 mol/L perchloric

acid is recommended. It should be stored in the dark

in a well-stoppered glass

bottle. This solution is stable for three months.

SRM 936 is for "in vitro" diagnostic use only.

The material should be kept in its original bottle and stored

in the dark at 30 °C or less. Under these conditions SRM 936

is stable for three years.

See NBS Special Publication

260-64.

17
Appendix A-2.1

(Eerttficate

Standard Reference Material 930D

Glass Filters for Spectrophotometry

This Standard Reference Material (SRM) is intended as a reference source for the verification of the transmittance and

absorbance scales of spectrophotometers. SRM 930D consists of three individual glass filters in separate metal holders and one empty filter holder. The filter holders are provided with shutters that protect the glass filters when not in use. These shutters must be removed at the time of measurement and be replaced after the measurements have been

completed. Each metal holder bears a filter number ( 1 0, 20, or 30) and a set identification number. The upper left corner

of each filter has been removed to indicate correct orientation in the metal holder. The certified transmittance values are given below.

Filter & Set

Ident. Number

TRANSMITTANCE (T) TRANSMITTANCE DENSITY (-log 10 T) Wavelength and (Bandpass) nm

Wavelength and (Bandpass) nm

440.0

(2.2) 465.0

(2.7) 546.1(6.5) 590.0(5.4) 635.0

(6.0) 440.0(2.2) 465.0(2.7) 546.1(6.5) 590.0(5.4) 635.0(6.0)

Date of Certification: The uncertainty of the certified transmittance value is ±0.5 percent at the time of certification. This uncertainty includes

the effects of the random and systematic errors of the calibration procedure, as well as possible transmittance changes of

the filters during the period of calibration. The transmittance values (T) can be converted to percent transmittance (%T) by multiplying by 100. The transmittance

densities are calculated from the measured transmittance (T). These values should be indicated by the absorbance scale of the spectrophotometer if the filters are measured against air. The transmittance values given were measured against

air at an ambient temperature of 22.5 °C. Aging of the glass may cause some filters to change transmittance by about ±1 percent over a period of approximately one year from the date of calibration. Improper storage or handling of the filters may also cause changes [5]. It is recommended that the filters in the holders be handled only by the edges with soft plastic (polyethylene) gloves and

optical lens tissue. When not in use they should be stored in their holders and in the container provided for this purpose. Extended exposure to laboratory atmosphere and dusty surroundings should be avoided. In cases where verification is desirable, the filters should be returned to the National Bureau of Standards for cleaning and recalibration. The research, development, and initial production of this SRM were conducted by R. Mavrodineanuand J.R. Baldwin, NBS Inorganic Analytical Research Division. The transmittance measurements were performed by R.W. Burke, M.V. Smith, and R. Mavrodineanu, NBS Inorganic

Analytical Research Division. Technical leadership for the preparation and measurements leading to certification was

provided by R.W. Burke. The overall direction and coordination of the technical measurements leading to certification were performed under the chairmanship of J.R. DeVoe, NBS Inorganic Analytical Research Division. The technical and support aspects involved in the preparation, certification, and issuance of this Standard Reference

Material were coordinated through the Office of Standard Reference Materials by L.J. Powell. Gaithersburg, MD 20899 Stanley D. Rasberry, Chief August 15, 1984 office of Standard Reference Materials (Revision of Certificate dated 8-1-77) 18

S. Department of Cot'm.erce Malcolm Baldrige Secretary

National Bureau orSiandards

Ernest Ambler. Director
The transmittance measurements were made using the high-accuracy spectrophotometer designed and built at the NBS

Center for Analytical Chemistry [1]. This instrument represents the primary transmittance standard; its transmittance accuracy was established using the double-aperture method of linearity testing [1,3,5,6]. The estimated standard

deviation obtained from a set of 20 measurements of the high-accuracy spectrophotometer used for transmittance measurements on glass filters of the SRM 930 type is 5 x 10 transmittance units for transmittance between 0.1 and 0.3. The bounds of the systematic error of the instrument are estimated to be ±10 transmittance units. The neutral glasses for the filters were provided by Schott of Mainz, Germany, and are designated as "Jena Color and

Filter Glass." The glass material was selected for best homogeneity and minimum of inclusions and striae. The glass

filters were aged at NBS for about one year prior to certification. They are of the type NG-4 and NG-5, and their nominal

transmittances are 10, 20, and 30 percent [2,5]. The glasses were selected to provide a means to verify the transmittance

scale of conventional spectrophotometers at three levels. The exposed surface of the glass is approximately 29 x 8 mm,

measuring from a point 1.5 mm above the base of the filter holder (see figure). The empty filterholder is provided to be used in the reference beam of the spectrophotometer so that approximately equivalent conditions of stray radiation are achieved for both beams. The transmittance of the filters depends upon the intrinsic properties of the material, wavelength, spectral bandpass, geometry of the optical beam, stray light, temperature, and positioning of the filter. A change of ambient temperature of

1 or 2 °C from 22.5 °C will not significantly affect the calibration [5]. Changes in the transmittance may be caused by

surface conditions, aging of the glass, exposure to a harmful atmosphere, or careless handling as indicated on the face of

this certificate [2,3,4,5]. The effective spectral bandpass used to determine the certified values was 0.8 nm. The spectral bandpass values indicated in parentheses in this certificate are maximum values that should not be exceeded when

accurate measurements are contemplated. The transmittance measurements were made by producing the vertical image

of the slit (about 8 mm by 0.5 mm), using a convergent beam geometry with an aperture ratio f: 10, in the middle of the entrance face of the glass filter. The filters were measured in the spectrophotometer in a position perpendicular to the

incident light beam as shown in the attached figure. Measurements performed outside these specified conditions will produce transmittance values that might differ from the certified data. SRM 930D is stored in a black anodized aluminum container provided with a threaded cap made of the same metal. Each filter is placed in a cylindrical cavity to prevent any contact between the filter face and the walls of the storage

container. Contamination of the glass filter surface with particulate matter due to static charge is minimized through

the metallic nature of the container. Each filter holder is provided with a flat leaf spring which is inserted into the

cylindrical cavity to minimize damage during transportation. These springs can be removed during normal use in the laboratory. Prior to certification measurements, each filter was examined for surface defects and thoroughly cleaned [5]. Should the surface of the glass filter become contaminated, no attempt should be made to clean it unless the user has the facilities to demonstrate that the cleaning treatment has not altered the glass surface or degraded the accuracy of the certified values. As the Standard Reference Material is a transfer standard, the only means available to verify its integrity is remeasuring

its transmittance with a primary standard instrument similar to that used in this certification [ 1 ,4,7]. In most cases where

verification, or recertification, of the transmittance values is desirable, it will be most expeditious to return the filters to the National Bureau of Standards for measurement. Prior to shipment, the NBS Office of Standard Reference Materials should be contacted regarding the conditions and cost of verification and /or recertification. We wish to acknowledge the cooperation of George N. Bowers, Jr., M.D., of Hartford Hospital, Hartford, Connecticut; Royden N. Rand, Ph.D., of the Eastman Kodak Co. Research Laboratories, Rochester, New York; and Donald S. Young, M.D., and Ph.D., of the Mayo Clinic, Rochester, Minnesota.

SRM 930D

Page 2

19
REFERENCES

1. R. Mavrodineanu, An Accurate Spectrophotometer for Measuring the Transmittance of Solid and Liquid

Materials, NBS Journal of Research 76A, No. 5, 405-425 (1972).

2. R. Mavrodineanu, Solid Materials to Check the Photometric Scale of Spectrophotometers, NBS Tech. Note

544, O. Menis and J.I. Shultz, Eds., pp. 6-17, U.S. Government Printing Office, Washington, DC 20402 (Sept. 1970); ibid, NBS Tech. Note 584, pp. 2-21 (December 1971).

3. K.S. Gibson, Spectrophotometry, NBS Circ. 484 (Sept. 1949).

4. Collected Papers from NBS Conference on Accuracy in Spectrophotometry and Luminescence Measurements, NBS Journal of Research 76A, No. 5, 375-510 (1972).

5. R. Mavrodineanu and J.R. Baldwin, Glass Filters as a Standard Reference Material for SpectrophotometrySelection, Preparation, Certification, Use, SRM 930, NBS Special Publication 260-51, U.S. Government

Printing Office, Washington, DC 20402, (1975).

6. K.D. Mielenz and K.L. Eckerle, Spectrophotometer Linearity Testing Using the Double-Aperture Method,

Appl. Optics 11, 2294-2303 (1972).

7. R.W. Burke and R. Mavrodineanu, Accuracy in Analytical*Spectrophotometry, NBS Special Publication 260-81, U.S. Government Printing Office, Washington, DC 20402, (1983.) METAL HOLDER FOR THE COLORED GLASS FILTERS*

FRONT TOP METAL HOLDER

57 x 13 X 13

EXPOSED FILTER SURFACE

29 X 8

COLORED GLASS FILTER

1.5

30.5 x II x 2.0 (Of 1.5)

Nominal Dimensions in mm

Shutters not illustrated.

SRM 930D

Page 3 20
Appendix A-2.2 Rational ^uram af j&antlartb

Standard Reference Material 931c

Liquid Absorbance Standards for

Ultraviolet and Visible Spectrophotometry

This Standard Reference Material is certified as solutions of known net absorbances at specific spectral wavelengths. It is intended primarily for use in the calibration and checking of accuracy of the photometric scale of narrow bandpass

spectrophotometers and for routine critical evaluation of daily working standards used in spectrophotometry. This Standard Reference Material is applicable for calibrating those instruments that provide an effective spectral bandpass

of 1.5 nm or less at 320 nm, 2.0 nm or less at 395 nm, 3.3 nm or less at 512 nm.and 8.5 nm or less at 678 nm [1].

Net Absorbance

3 Wavelength and (Bandpass), nm

Filter 302(0.8) 395 (0.8) 512(0.8) 678(0.8)

"1" -"Blank" 0.305 ± 0.001 0.309 ±0.001 0.307 ± 0.001 0.116 ± 0.001

"11" -"Blank" .608 ± .002 .612 ± .002 .609 ± .002 .232 ± .001 "IH"-"Blank" .938 ± .002 .912 ± .002 .904 ± .002 .346 ± .001

"Net absorbances ("I" - "Blank", "II" - "Blank", and "111" - "Blank") were determined using 10.00-mm cuvettes (SRM 932) at 25 °C. See Instructions

for Use. The transmittance measurements leading to the certification of this SRM were performed on the high accuracy spectrophotometer located in the NBS Center for Analytical Chemistry. The design and construction of this instrument have been described previously [2]. This instrument is the primary transmittance standard; its accuracy has been verified using the double aperature radiation-addition principle. The bounds of systematic error of this instrument are estimated

to be ± 10 transmittance units. These liquid absorbance filters were calibrated at the wavelengths and conditions indicated by measuring the transmittance, T, of the "Blank" and solutions "1", "11", and "111" against air as a reference. The values of T were used to calculate the corresponding apparent absorbances, Aa , using the relationship Aa =-logioT. The certified net absorbances were obtained by subtracting the apparent absorbances of the "Blank" solution from the apparent absorbances calculated for solutions "I", "11", and "III". The uncertainties of the certified values include all known

sources of possible systematic error and the 95 percent confidence level for the mean.

While no long-term stability studies have been made on this lot (93 lc), studies on previous lots (93 1, 93 la, and 93 1 b) over

three-year periods showed no degradation of the material when stored in the original sealed ampoules. Therefore, this material is certified only for use within three years following the date of purchase. The preparation of the filters was performed by E.R. Deardorff, Inorganic Analytical Research Division, and the transmittance measurements were performed by M. V. Smith, Office of Standard Reference Materials. Technical leader- ship for the preparation and measurements leading to certification was provided by R.W. Burke, Inorganic Analytical Research Division. The overall direction and coordination of technical measurements leading to certification were performed under the chairmanship of E.L. Garner. The technical and support aspects involved in the preparation, certification, and issuance of this Standard Reference

Material were coordinated through the Office of Standard Reference Materials by R.W. Seward. Washington, D.C. 20234 George A. Uriano, Chief February 12, 1982 Office of Standard Reference Materials

U. S. Department of Commerce

Malcolm Baldrige ^secretary

National guroau of Standard

Ernest ^mbler, QSreclor

21
Temperature Dependence

Absorbances at various temperatures (17 to 35 °C) may be calculated using the equation At = A25[l+CA(t-25)] where: At = Absorbance at temperature t (°C) A25 = Absorbance certified at 25.0 °C Ca = Fractional change in absorbance per °C

The values of Ca, at the four wavelengths, are given below. [NOTE: At wavelength 302 nm, absorbance decreases with

increasing temperature; at the other wavelengths, absorbance increases with increasing temperature.]

Preparation of Filters The filters were prepared by dissolving high-purity cobalt and nickel in a mixture of nitric and perchloric acids. The

absorbance spectrum of the resulting solution is shown in the following figure. The maxima at 302 and 5 1 2 nm are due to absorbance by NO" and Co(H20)6?respectively. The maximum at 395 nm and the plateau at 650-700 nm are due to Ni(H:0)6** The pH of these solutions is about 1.

Instructions for Use

This material is for use as a spectrophotometric absorbance standard.

1. Select two clean 10.00 mm cuvettes free of scratches. At least one should be fitted with a ground glass or Teflon

stopper to minimize evaportation. Reserve it for all sample measurements.

2. Mark each of the cuvettes to assure the same orientation in the spectrophotometer.

3. Place the cuvettes in their respective holders and fill with distilled water. (Borosilicate Pasteur-type pipettes fitted with rubber bulbs are recommended for transferring all solutions to and from the cuvettes. Soft glass pipettes, which

are available commercially, contain residual amounts of ultraviolet absorbing material, but may be used after proper

cleaning. Several rinses, first with isopropyl alcohol and then with distilled water, are generally adequate.

4. Obtain the optical mismatch of the cuvettes at 302, 395, 512, and 678 nm, using the spectral bandpass limitations given on the face of the certificate.

5. Empty the cuvettes by suction without removing them from their holders, refill with distilled water and measure the absorbances again at each of the above wavelengths.

Wavelength, nm

302

395 512 678

-0.0014

+0.0014

+0.0018 +0.0014

22
6. Repeat the emptying and refilling operation until constant absorbance readings are obtained.

7. Using the liquid filters provided, measure, in turn, the absorbance of the "Blank", "1", "11", and "III" against distilled water. Shake each ampoule before opening to remix any condensate which may have been collected in the neck. (The ampoules, have been prescored directly below the gold band to facilitate opening.)

8. Subtract the appropriate "Blank" reading from the absorbances obtained for "1", "II", and "III". These net absorbances should agree with the certified values within the uncertainties specified. Consult the manufacturer of the instrument if they do not. The above instructions are for use with the standard 10-mm rectangular cuvette. For calibration of the several spectrophotometric systems used in various automated instruments, the user is referred to the instruction manual for the

particular instrument. The absorbances of these liquid absorbance standards will depend not only on the accuracy of the photometric scale, but

also on the wavelength accuracy and the spectral bandpass. A mercury lamp is recommended for checking the wavelength scale. In addition, for those spectrophotometers having a hydrogen (H) or deuterium (D) source, the two emission

lines at 486.1 and 656.3 nm (H) or 486.0 and 656.1 nm (D) may provide a convenient check at these wavelengths. To ensure that the measured absorbances are not significantly different from the certified values, the following

restrictions are placed on the size of the spectral bandbass selected: To obtain ±0. 1 percent of the true value, the effective spectral bandpass should not exceed 1.5, 2.0, 3.3, and 8.5 nm at 302, 395, 512, and 678 nm, respectively. For ±0.2 percent, the respective bandpasses should not exceed 2.2, 2.9, 4.8, and 12.3 nm. Additional information on the

effect of spectral bandpass on the absorbances of these filters is given in the figure below. These curves are not to be used, however, to correct the measured absorbances. + 2.00

,o +1.00 S o.oo §

-'-oo

usv -2.00 <

00oc -3.00 o

</> 3 -4.00

-5.00 0 2 4 6 8 10 12 14 16 18 EFFECTIVE SPECTRAL BANDPASS, nm

This Standard Reference Material should be kept in the original sealed ampoules. Once opened, the material should be used immediately. No attempt should be made to reseal the ampoule. In addition, it is recommended that this Standard

Reference Material not be used after three years from the purchase date.

References

[1] R. W. Burke, E. R. Deardorff, and O. Menis, J. Research, Nat. Bur. Stand. 76A, 469-482 (1972).

[2] R. Mavrodineanu, J. Research, Nat. Bur. Stand. 76A, 405-425 (1972).

Note: The above papers are also published in NBS Special Publication 378, Accuracy in Spectrophotometry and

Luminescence Measurements, R. Mavrodineanu, J. I. Shultz, and O. Menis, Editors, U.S. Government Printing Office, Washington, D.C. 20402, 1973.

23
U. S. Department of Commerce

Philip M. Klutznick Appendix A-2 .

3

National Bureau of Standards

Ernest Ambler, pireclor Rational ^mtrnx of j^tandartte

(tterttfttate

Standard Reference Material 932

Quartz Cuvette for Spectrophotometry

R. Mavrodineanu and J. W. Lazar

This Standard Reference Material consists of a single, accurately calibrated cuvette that is issued for use in the production of accurate spectrophotometric data on liquids. The design and nominal dimensions of the all-quartz cuvette are shown in Figure 1. The pathlength of the cuvette is defined by the distances between the two optically transparent windows measured at several heights within the cuvette. Cuvettes issued as Standard Reference Material 932 have a nominal pathlength of 10 mm. The pathlength and parallelism are certified, at the time of measurements, with an

uncertainty of ±0.0005 mm as determined by measurements (at 20 °C) taken at the positions indicated below. Cuvette number is issued with this certificate. For this cuvette the following measurements were obtained:

Date of Certification: The overall direction and coordination of the technical measurements leading to certification were performed under the chairmanship of O. Menis and J. A. Simpson. The technical and support aspects involved in the preparation, certification, and issuance of this Standard Reference

Material were coordinated through the Office of Standard Reference Materials by T. W. Mears.

Washington, D.C. 20234 George A. Uriano, Chief December 2, 1980 Office of Standard Reference Materials

Height Pathlength mm mm

(Revision of certificates dated 11-5-73, 6-16-77, and 8-2-78)

24
The original cuvettes were designed and produced at the National Bureau of Standards (NBS) using special techniques and non-fluorescent optical-quality fused quartz as described in NBS SP 260-32[l]. The transparent windows are attached to the body of the cuvette by direct fusion, and the unit was stress-relived by annealing. The radiation pathlength measurements of the cuvette were performed using electronic feeler-gauge type instruments capable of a

resolution of 5 parts in 10

6

. To preserve the integrity of the certified values, the cuvette must be handled with great care and should be held only by the frosted-quartz side windows. When not in use, it should be stored in the container provided for this purpose. Extended exposure to laboratory atmosphere and dusty surroundings is to be avoided. Improper handling of the cuvette and the use of solutions that can corrode or errode the quartz could degrade the

certified pathlength values. In cases where verification of the pathlength is desirable, the cuvette should be returned to NBS for examination and, if needed, recalibration. Prior to shipment the NBS Office of Standard Reference Materials should be contacted regarding the conditions and cost of the verification and /or recertification. The development and production of SRM 932 is a result of the combined efforts of the Center for Analytical Chemistry,

the Center for Mechanical Engineering and Process Technology, and the Instrument Shops Division. The radiation pathlength measurements of all of these cuvettes have been performed, at NBS, by E. G. Erber of the Mechanical

Processes Division. Reference:

[1] Mavrodineanu, R., and Lazar, J. W., Standard Reference Materials; Standard Quartz Cuvettes for High Accuracy

Spectrophotometry, Nat. Bur. Stand. (U.S.), Spec. Publ. 260-32 (December 1973). Superintendent of Documents,

U.S. Government Printing Office, Washington, D.C. 20402, 55 cents.

L_h__i

RADIATION PATHLENGTH"

1.25"

6

.4 TOP

SIDE 48

(FROSTED)

FRONT

(TRANSPARENT)

BOTTOM

1.25

12.5

I

I All dimensions in millimeters.

I H— 10 HI 12.5 U

II II T12.5

TOP MEASUREMENT

LEVEL

BOTTOM MEASURMENT

LEVEL

INCIDENT RADIATION BEAM

25
U.S. Department of Commerce Appendix A-2 . 4

Juanita M Krep9

Secretary

National Bureau of Standards

Ernest Ambler, Acting Director^National ££itram of j&tandartte

(fUritftcate

Standard Reference Material 935

Crystalline Potassium Dichrom ate

for Use as an Ultraviolet Absorbance Standard

R. W. Burke and R. Mavrodineanu

This Standard Reference Material consists of crystalline potassium dichromate of established purity. Solutions

of known concentrations of this SRM in 0.001 N perchloric acid are certified for their apparent* specific absorbances**, 6a , at 23.5 °C.

This SRM is intended to be used as a reference standard for the verification of the accuracy and linearity of the absorbance scale of absorption spectrometers that can provide an effective spectral bandpass of 1.2 nm or less at 235 nm, and 0.8 nm or less at 257, 313, 345, and 350 nm. Such verification is accomplished by comparing the measured apparent absorbances, Aa , to the Aa calculated from the certified €a values as described under

"Instructions for Use." Table 1 gives the certified values of 6a in kg g

' cm

1 for five concentrations of the SRM 935 potassium dichromate in 0.001 N perchloric acid at 23.5 °C and the indicated wavelengths and spectral bandpasses for a 1-cm internal pathlength.Table 1. €a , Apparent Specific Absorbance,

3 kg-g -cm Nominal Wavelength and (Bandpass) nm

Concentration

g'kg" Uncertaii

1 235.0(1.2) 257.0(0.8) 313.0(0.8) 345.0(0.8)

b 350.0(0.8) 0.020 12.260 14.262 4.805 10.604 10.672 ± 0.034

.040 12.304 14.318 4.811 10.603 10.682 ± .020

d .060 12.347 14.374 4.816 10.602 10.692 ± .020

d .080 12.390 14.430 4.821 10.601 10.701 ± .020

d .100 12.434 14.486 4.827 10.600 10.711 ± .020

d

Ca values are given to the third decimal place to preserve the smooth variation of the data with concentration, although the

uncertainties are in the second decimal place. Wavelength 345.0 nm is near one of the two isosbestic points in HCrOT/C^O? spectra. Because it is on the slope of the composite

spectrum, reproduction of the Ca values is dependent on wavelength accuracy. Measurements at this wavelength should be made only for

verification of the linearity of the absorbance scale. €a values are not corrected for the effects of internal multiple reflections within the cuvette, nor have the weights been corrected to vacuum. With these two exceptions, the uncertainties given include all known systematic errors and the 95 percent confidence

interval of the mean. At wavelength 313.0 nm, the uncertainty is reduced to ±0.010. •The term "apparent" is used because no corrections have been applied to the data for the effects of internal multiple reflections within the cuvette or for buoyancy, i.e., the weights used to express concentrations have not been corrected to vacuum. These combined corrections do not exceed 0.2 percent. The specific absorbances are given in reference 1. The nomenclature used in this certificate is that recommended by K. D. Mielenz, Anal. Chem. 48, 1 093-1 094 ( 1976), which is reproduced

in the Appendix of NBS Special Publication 260-54.

Washington, D.C. 20234 J. Paul Cali, Chief June 1 , 1 977 Office of Standard Reference Materials

26
The overall direction and coordination of the technical measurements leading to this certificate were per- formed under the joint chairmanship of I. L. Barnes and J. R. DeVoe. The technical and support aspects involved in the preparation, certification, and issuance of this Standard

Reference Material were coordinated through the Office of Standard Reference Materials by R. W. Seward. We wish to acknowledge: The contributions of K. D. Mielenz, NBS Analytical Chemistry Division, for his many

valuable discussions and suggestions, and H. H. Ku, NBS Applied Mathematics Division, for his statistical treatment of the data; the cooperation and early support of the National Institute of General Medical Sciences in the research leading to this SRM; and the encouragement of George N. Bowers, Jr., M.D., Hartford Hospital, Hartford, Conn., and Royden N. Rand, Ph.D., Eastman Kodak Co., Research Laboratories, Rochester, N.Y.

The details of the preparation and certification of SRM 935 are provided in NBS Special Publication 260-54,

Certification and Use of Acidic Potassium Dichromate Solutions as an Ultraviolet Absorbance Standard [2]. This publication should be referred to every time SRM 935 is to be used. Briefly, the transmittances, T, of the

solutions prepared from the undried, as received, material were measured with the NBS Institute for Materials Research high-accuracy transmission spectrometer [3]. The 6a values were calculated for each wavelength using the relation:

€a = apparent specific absorbance Aa = apparent absorbance Ds = transmittance density of the sample solution, -logioTs Db= transmittance density of the blank solution, -logioTb b = internal cuvette pathlength, cm

c = concentration, by weight, of K2Cr207 solution, g kg The crystalline potassium dichromate used for SRM 935 is a special lot of analytical reagent grade material obtained from the J. T. Baker Chemical Co., Phillipsburg, N.J. Assay: A coulometric assay of the purity of the undried material was performed by G. Marinenko of the NBS

Analytical Chemistry Division. The purity of SRM 935, expressed as an oxidant, was found to be 99.972 ±0.005

percent where the uncertainty figure represents the 95 percent confidence interval for the mean based on 1

degrees of freedon. In addition, the material was examind by optical emission spectrometry for trace elemental

impurities by J. A. Norris of the NBS Analytical Chemistry Division. The only significant impurities detected were sodium and rubidium. Their concentrations were estimated to be in the range of 0.02 and 0.03 percent,

respectively. Drying at 105 °C for 12 hours showed that the surface moisture of this material was less than

0.01 percent.

Stability: Solutions prepared from SRM 935 in the concentration range indicated in table 1 and made according

to the instructions given in NBS SP 260-54 have been found to be stable within the uncertainties given in table 1 for at least six months when stored at room temperature and protected from evaporation and exposure to light.

The use of SRM 935 as an absorbance standard requires the careful preparation of a series of solutions of known concentrations, c, of the potassium dichromate in 0.001 N perchloric acid. These solutions are trans- ferred to a quartz cuvette of known pathlength, b, and their apparent absorbances measured at wavelengths

235, 257, 313, and 350 nm, using the spectral bandpass requirements given in table 1. The preparation and measurement of these solutions are described in detail in Section 5 of NBS SP 260-54.

PREPARATION AND CERTIFICATION

Ds - Db _ Aa (1) where:

INSTRUCTIONS FOR USE

27
The accuracy of the absorbance scale of the spectrometer being tested is ascertained by comparing the measured

apparent absorbances, Aa , of a series of 0.001 N perchloric acid solutions containing 0.020 to 0.100 gram

K.2Cr2C>7/kg to the Aa values calculated from the certified 6a values. Although the €a data in table 1 are given for nominal concentrations of 0.020, 0.040, 0.060, 0.080, and 0. 100 g K2Cr207 /kg, the €a values for concentrations between these nominal concentrations can be determined by linear interpolation. Using the appropriate 6a values, the calculated Aa values at 23.5 °C are obtained from the expression: Aa = €a x b x c (2)

Calculations: An example of the calculation of Aa for one concentration of K2CT2O7 under a specified set of conditions is shown below. Calculations of Aa for other concentrations and wavelengths are performed in a similar manner.

Conditions: Wavelength = 350 nm, spectral bandpass 0.8 nm or less b = 0.9982 cm

c = 0.04375 g-kg"

1

t = 23.5 °C From column 6, table 1, the 6a for concentrations of 0.040 and 0.060 g kg"

1 are 10.682 and 10.692, respectively. The corresponding 6a for c = 0.04375 g-kg is: C-='ft682 + ^-^°

(ia692 -ia6g2)

6a = 10.682 + 0.0019 6a = 10.684 The calculated apparent absorbance, Aa , from equation 2, is: Aa = 10.684 x 0.9982 x 0.04375 Aa = 0.4666 The uncertainty, AAa , in the calculated Aa is determined from the combined uncertainties in 6a , b, and c in equation 2, provided no other systematic errors are present. Thus: AAa = be

I A6aI + eacI Ab I + 6a b I Ac I (3) To evaluate AAa , A6a is taken from column 7 of table 1 and the Ab and Ac values must be determined experi- mentally.

I n the experiments performed to obtain the 6a values in table 1 , the uncertainties for b and c did not exceed 1 part

in 10 and 2 parts in 10 , respectively. The solution of equation 3 gives: AAa = 1(0.044) (0.020) + 10.7(0.044) (0.0001) + 10.7(1) (0.0000088) = 0.0010 Thus, the uncertainty of Aa , for the above set of conditions, is ±0.0010. The correction of the absorbance scale of the absorption spectrometer under test is determined by plotting the

differences between Aa measured and Aa calculated as a function of absorbance. A typical plot of such a graph

is shown in figure 1 . The apparent absorbances measured on this instrument at 350 nm are accurate when the indicated correction is subtracted from the corresponding absorbance scale reading, provided that the conditions of wavelength accuracy, spectral bandpass, and absence of stray light are fulfilled as specified in NBS SP 260-54. Correction curves for wavelengths 235, 257, and 313 nm are obtained in a similar manner.

28
8 1-

Figure 1. Correction curve for the absorbance

scale of a precision spectrometer. The error bars

are the sum of the errors arising from the uncertainties in the certified apparent specific absorbances, €a , cuvette pathlength, b, and concentration, c.

o ® 1 1 i < _I_JL

0.6 Absorbance Temperature Correction: Although €a values in table 1 are certified at 23.5 °C, SRM 935 can be used as an absorbance standard at other temperatures in the range 20 to 30 °C provided corrections are made to the Ca values. Over this range the apparent specific absorbances decrease linearly with increasing temperature for all the wavelengths given in table 1 . The corresponding temperature coefficients, k, for these wavelengths are given in table 2.

Table 2. Variation of ea with Temperature Over the Range 20 to 30 °C.

X, nm Temperature Coefficient, k

The value of €a at any temperature in the range 20 to 30 °C can be calculated from the certified value and the appropriate temperature coefficient using the relation:

k = temperature coefficient, percent per ° C. REFERENCES

1. Burke, R. W., and Mavrodineanu, R., Acidic Potassium Dichromate Solutions as Ultraviolet Absorbance

Standards, J. Res. Nat. Bur. Stand. (U.S.), 80A (Phys. and Chem.), No. 4, 631-636 (July-Aug. 1976).

2. Burke, R. W., and Mavrodineanu, R., Certification and Use of Acidic Potassium Dichromate Solutions as an Ultraviolet Absorbance Standard, NBS Spec. Publ. 260-54 (1977). Copies may be obtained from the

Office of Standard Reference Materials, National Bureau of Standards, Washington, D.C. 20234.

3. Mavrodineanu, R., An Accurate Spectrophotometer for Measuring the Transmittance of Solid and Liquid

Materials, J. Res. Nat. Bur. Stand. (U.S.), 76A (Phys. and Chem.), No. 5, 405^25 (1972).

Percent per degree Celsius 235 257

313

345 350

-0.05

-0.05 -0.02

-0.08

-0.05

where: €a = apparent specific absorbance at temperature t (°C) €a

3 ' 5 = apparent specific absorbance certified at 23.5 °C.

29
U.S. Department of Commerce

Juanita J4. Kreps

Secretary/ Appendix A-2.5

National Bureau of Standards

Ernest Ambler. Director Rational ^mmn of j^tandartte

(Eertifttate

Standard Reference Material 936

Quinine Sulfate Dihydrate

R. A. Velapoldi and K. D. Mielenz

This Standard Reference Material is intended for use in the evaluation of methods and the calibration of

fluorescence spectrometers. It is certified for the relative molecular emission spectrum, E(X), in radiometric

units for a solution of 1.28 x 10 mol/L quinine sulfate dihydrate in 0.105 mol/L perchloric acid using an

excitation wavelength of 347.5 nm. The certified values of the molecular emission spectrum at 5 nm wavelength intervals from 375 to 675 nm are given in table 1. These values have been corrected for instrument and

sample parameters, including the spectral responsivity of the detection system, monochromator bandwidth,

photomultiplier tube nonlinearity, monochromator wavelength error, solvent refractive index, and cell window

transmittance. The relative standard error in E(X), RSE [E(X)], is given in table 1. The estimate of the

relative systematic error limits in the molecular emission spectrum, RSEL [E(X)J, is also given in table 1 and was determined by the addition of the absolute values of the estimated systematic errors. These relative error

limits include uncertainties in the calibration values for the spectral responsivity, the wavelength position of the emission peak maximum, and in the corrections applied for instrument and sample parameters. From the certified values of E(X), values may be calculated for the molecular emission spectrum in the various photon, radiometric, wavelength, and wavenumber units using the following equation: [1,2]

These values have been calculated and are given in NBS Special Publication 260-64. The technical emission spectrum, E

T

(X), i.e., the emission spectrum corrected for instrument parameters only,

is also given in SP 260-64. The quinine sulfate dihydrate used for SRM 936 was a special lot of material obtained from the J. T. Baker Chemical Co., Phillipsburg, N.J. The technical and support aspects concerning the preparation, certification, and issuance of this Standard

Reference Material were coordinated through the Office of Standard Reference Materials by T. W. Mears and

R. W. Seward. Washington, D.C. 20234 George A. Uriano, Chief

April 1, 1979 Office of Standard Reference Materials

E(X) =

EP(X) =

E(ff) =

Ep(y) X X

2 X

3

30
Table 1. The Molecular Emission Spectrum, E(A), of Quinine Sulfate Dihydrate in 0.105 mol/L HCIO4, the

Relative Standard Error, RSE, and the Estimated Relative Systematic Error Limits, RSEL, in the E(X) Values. A,nm E(X) RSE [E(\)] RSEL [E(X)] 375.0 0.005 0.019 0.087

380.0 .012 .006 .078 385.0 .028 .003 .071 390.0 .057 .003 .064 395.0 .103 .002 .059 400.0 .170 .002 .054 405.0 .257 .003 .049 410.0 .359 .003 .045 415.0 .471 .003 .041 420.0 .586 .003 .037 425.0 .694 .003 .034 430.0 .792 .002 .031 435.0 .874 .002 .028 440.0 .940 .001 .026 445.0 .984 .001 .024 450.0 .999 .001 .023 455.0 .997 .001 .023 460.0 .982 .001 .024 465.0 .947 .001 .024 470.0 .897 .001 .025 475.0 .838 .002 .026 480.0 .782 .002 .027 485.0 .719 .002 .027 490.0 .657 .002 .027 495.0 .595 .003 .027 500.0 .541 .002 .027 505.0 .486 .001 .028 510.0 .434 .003 .028 515.0 .386 .003 .028 520.0 .342 .002 .028

SRM 936 Page 2

A,nm E(X) RSE [E(A)] RSEL [E(\)] jIj.v A 1AO A AA1 CIA A .zo4 AA1 .K)J.y mo

C1C A .2.51 AA1

C/4A A iai .ZIM AAO .\)ly CA C A 1 "JC

. 1 fj AAT .UUZ .VZy mo

CCA A . 1 JJ AA1 .Uly Ail AA 1 .UU1 AOQ

560.0 .110 .001 A'JA 565.0 iai

. I VI .002 .029 570.0 .088 .002 .029 575.0 .076 .003 .029 580.0 .065 .003 .029 585.0 .057 .001 .029 590.0 .050 .003 .030 595.0 .043 .004 .030 600.0 .037 .006 .030 605.0 .032 .002 .030 610.0 .028 .006 .030 615.0 .024 .003 .030 620.0 .021 .011 .030 625.0 .018 .003 .030 630.0 .016 .015 .030 635.0 .014 .014 .030 640.0 .011 .037 .030 645.0 .010 .015 .030 650.0 .009 .027 .030 655.0 .008 .035 .031 660.0 .007 .073 .031 665.0 .006 .046 .032 670.0 .005 .053 .032 675.0 .004 .065 .033

31
SUPPLEMENTARY DATA

The following data for the specific molar absorbances, water content, photon yields, and fluorescence lifetimes are considered to be supplementary and are not to be considered certified values. The quinine sulfate dihydrate (QSD) used for SRM 936 was found to be homogeneous to better than 0.5% by

thin-layer chromatography with development by two solvent systems and the determination of specific molar

absorbances, e, at three different wavelengths. The SRM contains approximately 1.7% of an impurity as determined by high performance liquid chromatography using absorbance and fluorescence detection. This impurity is believed to be dihydroquinine sulfate dihydrate, which has optical characteristics that are similar to those of the quinine sulfate dihydrate. The ultraviolet absorption spectrum of SRM 936 in 0. 105 mol/L HC IO4

exhibits the following absorption maxima:

250.0 nm, Cmax = 56,990 ± 90 L mof' cm"

1 347.5 nm, emax = 10,810 ± 20 Lmof'cm"1 and, on the side of a peak:

365.0 nm, e0bs = 6,920 ± 10 Lmof'cm-1 The water content of this material was measured by two methods. The average of six determinations by the Karl-Fischer method gave a value of (4.74 ± 0.05%), while the average of four determinations by a weight loss procedure gave a value of (4.57 ± 0.04%). The theoretical value for water in quinine sulfate dihydrate is 4.60%. The photon yield, Q, and the fluorescence lifetime, r, of SRM 936 were compared to values obtained for a sample of purified quinine sulfate dihydrate and are summarized below: Q r, ns

0.5 mol/L H2SO4 0.5 mol/L H2SO4 SRM 936, QSD 0.544 ± 0.03 19. 1 ± 0.

1

Purified QSD 0.546* 19.2 ±0.1

a Melhuish, W. H., J. Phys. Chem. 65, 229 (1961); ibid, New Zealand J. Sci. Tech. 37, 142

(1955).

SRM 936 Page 3

32
PREPARATION AND USE OF SRM 936

This Standard Reference Material is for "in vitro" diagnostic use as a clinical laboratory standard. A "stock" standard solution containing 0. 1 mg/mL of quinine sulfate may be prepared as follows: Weigh O.IOOgofSRM

936 to the nearest one-tenth milligram and quantitatively transfer it to a 1000-mL volumetric flask. Dilute to the

calibrated volume with 0.105 mol/L HC104,to give a solution that is 1.28 x

10~4 mol/L (0.1 mg/mL) in quinine

sulfate. Store this solution in the dark in a well-stoppered, glass bottle. A "working" standard solution containing 1 ng/mL may be prepared by transferring 10 mL of the above "stock" standard solution to a 1000-mL volumetric flask and diluting to the calibrated volume with 0. 105 mol/L HCIO4 to give a solution that

is 1.28 x 10 mol/L (1 /xg/mL) in quinine sulfate. Store this solution in the same manner as the above "stock" standard solution. Several opinions regarding the stability of quinine sulfate solutions have appeared in the literature [3]. NBS

considers the 0.1 mg/mL "stock" standard solution prepared from SRM 936 to be stable for 3 months when

stored as specified; and the 1 ng/mL "working" standard solution to be stable for 1 month when so stored. SRM 936 should be kept in its original bottle and stored in the dark at room temperature (30 °C or less). It should not be subjected to heat or direct sunlight during storage. Experience at NBS indicates that under proper

storage this material is stable for at least 3 years. If this material degrades beyond the limits certified, purchasers

will be notified by NBS. It is recommended that the material not be used after 3 years from the date of purchase.

References:

[1] Ejder, E. J., J. Opt. Soc. Amer. 59, 223 (1969).

[2] Melhuish, W. H., J. Res. Nat. Bur. Stand. (U.S.) 76A, No. 6, 547 (1972).

[3] Melhuish, W. H., J. Phys. Chem. 65, 229(1961); Gill, J. E., Photochem. and Photobiol. 9, 313(1969); Birks,

J. B., J. Res. Nat. Bur. Stand. (U.S.) 80A, 389 (1976); Heller, C. A., Henry, R. A., McLaughlin, B. A., and

Bless, D. E., J. Chem. Eng. Data 19, 2 14 (1974); West, M. A., and Kemp, D. R., Int'l. Lab., p. 27 (May/ June

1976); and White, J. U., Pittsburgh Conf. Abstracts, Paper 488 (1977). This Standard Reference Material has been measured and certified at the laboratories of the National Bureau

of Standards, Gaithersburg, Maryland. All inquiries should be addressed to: Office of Standard Reference Materials Room B311, Chemistry Building National Bureau of Standards Washington, D.C. 20234 The date of issuance and certification of SRM 936 was April 1, 1979

SRM 936 Page 4

33
V . VI U. S. DepartrfWrWfof Commerce MalcolrMaldrige Appendix A-2.6

National JumWi^oTsiandards

Ernest Krnbkr, Director Rational ^mtnn of j&tandartte

Certificate

Standard Reference Material 2010a

Didymium Glass Filter for Checking the

Wavelength Scale of Spectrophotometers

SERIAL NO.

Kenneth L. Eckerle

This Standard Reference Material (SRM) is a 51 x 51 x 3 mm didymium glass filter. SRM 2010a is intended for use in calibrating the wavelength scale in the visible wavelength region of scanning spectrophotometers having nominal bandwidths in the range 1.5 to 10.5 nm. Depending upon the bandwidth of the spectrophotometer, 12 to 22 wavelength

corrections can be determined from 389 to 760 nm. Detailed instructions on the use of this SRM and examples of its use

are given in the accompanying NBS Special Publication 260-66. Each didymium glass filter is identified by serial number.

All measurements on these filters were made at 25 °C with a high-accuracy reference spectrophotometer that has a wavelength accuracy of 0.04 nm.

Table 1 gives the wavelengths of the transmittance minima as obtained from measurements on two filters representative of this melt of didymium glass. These values are given for seven equally spaced values of the half-height width of

triangular pass bands. The minima numbers are shown on Figure 1, which illustrates the spectral transmittance as a

function of wavelength. Table 2 gives the wavelength values of nine points of inflection on the spectral transmittance curve as obtained on two

filters. These inflection points are representative of this glass melt and are also shown on Figure 1. These inflection points should only be used with the transmittance minima as described in Sections 2.2 and 2.3 in SP 260-66. Table 2 also indicates the range of the measured wavelengths of the inflection points. Table 3 gives the estimated random and systematic errors of the transmittance minima given in Table 1 (as obtained from

4 sets of measurements on a single filter). Table 4 gives the spectral transmittance as a function of wavelength for a filter representative of this melt. These values

are not certified but are provided for use as specified in SP 260-66. They should not be used to check the photometric

scale of a spectrophotometer.

Trial calibrations made on several instruments, using both minima and inflection points, indicate that wavelength

corrections made with these SRM's can be accurate to 0.2 nm. The uncertainty of a calibration, however, will depend upon the stability and other characteristics of a particular instrument. This filter should be handled only by its edges; when not in use it should be stored in the box provided. If cleaning is necessary, wet the filter with water and rub gently with optical lens tissue soaked with a mild soap solution, rinse with

distilled water, rinse with isopropyl alcohol, and rinse again with distilled water. Dry after each rinsing by wiping lightly with optical lens tissue.

July 25, 1984 Stanley D. Rasberry, Chief

Gaithersburg, MD 20899 Office of Standard Reference Material 34
Figure 1. Spectral transmittance as a function of wavelength. The numbers indentify minima, and the letters identify selected inflection points.

- 10.5 nm BANDWIDTH

LUU

<

<

t—i—i—i—

|—i—i—i—i—|—i—i—i—

1.5 nm BANDWIDTH

t—i—

i i i i i i L 400 500 600 700

WAVELENGTH [nm]

Page 2 SRM 2010a

35
TABLE 1 Certified Wavelengths (nm) of the Transmittance Minima for the Indicated Bandwidths

Bandwidth Minimum No.

1.5 nm 3.0 nm 4.5 nm 6.0 nm 7.5 nm 9.0 nm 10.5 nm

12 431 58 " ' 34 440 78 440 98 441 41 44 1 .94 442. 1

9

442. 1

7

44 1 .87

5 472.67 472.43 472.31 --

6 481.20 480.68 480 37 479 67 A7Q If.

*t /O.JO ATf. 1 c

7 513.66 513 76 5 1 3 94 KtA C"7 8 529.37 529.47 529 26 529 1

1

SOQ OC SOB Ofi SOfi 1A

9 573.12 573.88 574.75 575.72

10 585.50 585.68 585.86 586.03 585.91 585.29 584.39

11 623.85 624.42

12 629.51 629.26 628.17 627.17 627.17

13 684.71 684.74 684.78 684.80 684.77 684.73 684.65

14 739.61 740.20 740.58 741.33 742.55 743.50 744.16

15 748.64 748.48

TABLE 2 Wavelengths and Transmittances at Nine Selected Points of Inflection

Point

Identification Wavelength

(nm) Range*(nm)

Transmittance* A 388.68 +.02

-.02

0.3027

B 429.67 +.06 -.10

.6268 C 450.21 +.03

-.03

.5569 D 485.75 +.08 -.12

.6210 E 536.39 +.04

-.06

.5597 F 568.40 +.06

-.03

.3969 G 599.57 +.02

-.02

.3375 H 733.55 +.05

-.03

.4493

757.22 +.01 -.02

.3959

*The range of wavelengths within which the wavelength for the given trans- mittance will fall for symmetric triangular passbands with half-height bandwidths from 1.5 to 10.5 nm.

+These values of transmittance are not certified. Page 3 SRM 2010a 36
TABLE 3 Estimated Random and Systematic Errors of the Transmittance Minima

Nominal Standard Deviation for Indicated Bandwidth

Wavelength Band of Minimum 1.5 nm 3.0 nm 4.5 nm 6.0 nm 7.5 nm 9.0 nm 10.5 nm

Number Transmittance

i 402 nm -- -- -- -- -- --

2 431

0.013 nm

(0.06)* 0.010 nm -- -- -- --

3 440

0.021

(0.05) 0.013 0.050 nm 0.028 nm 0.009 nm 0.005 nm

0.007 nm

(0.25) 4 446

5 473

0.011

(0.08) 0.012 0.032 -- --

6 481

0.015

(0.15) 0.013 0.009 0.009 0.009 0.014

0.017

(0.25)

7 513

0.022

(0.08) 0.016 0.014 0.013 0.010

8 530

0.012

(0.21) 0.010 0.010 0.011 0.010 0.011 0.010

(0.25)

9 573

0.004

(0.05) 0.010 0.010 0.012 0.014

10

II

585

624

0.007

(0.06) 0.058

(0.06)

0.004

0.061

0.007 0.008 0.008 0.007

0.007

(0.25)

12 630

0.210

(0.02) 0.120 0.171 0.133 0.091

13 685

0.019

(0.05) 0.029 0.024 0.017 0.014 0.014

0.012

(0.25)

14 740

0.009

(0.25) 0.013 0.011 0.010 0.009 0.009 0.010

(0.25)

IS 748

0.020

(0.04) 0.016 * Values in parentheses are estimates of the systematic error. The estimates for the 1.5 nm bandwidth were obtained from the data taken at

1 . 5 nm intervals as compared to data taken at 0. 1 5 nm intervals. The method of estimating the systematic errors for the 1 0.5 nm bandwidth

is described in Section 3.4 in SP 260-66.

Page 4 SRM 2010a

37
TABLE 4 Transmittancc (T) as a function of wavelength from 380 to 780.5 nm for a bandwidth of 1 .5 nm. The estimates of random and systematic errors are also provided. These data are not certified.

Wavelength At AT Wavelength At At

(nm) T Standard Error Systematic (nm) T Standard Error Systematic 3 80 .0 0 • 14580 •000027 •000 10 38 1 . 5 0 •17003 •000030 •00010

3 83.00 • 195 54 • 000013 •00010 384* 50 • 22249 • TOO 01

5

• 000 10

3 86 .0 0 • 251 40 • 000030 • 000 10 387. 50 • 28 04 8 • 00003 6 • 000 10

3 89 .0 0 •30929 • 0000 54 •00010 390 • 50 •33718 • 000059 A A 4 A

• 00010

392.00 •36465 A r< A A "9 a • CC00 36 • 000 1

0

393 .50 • 391 59 • 000027 • 00010

3 95.00 •41903 •000065 •00010 396 .50 •44370 •000034 e 00010

3 9b .00 • 466 33 AA A Ai *% • 000062 •000 10 399. 50 •48705 9\ f\ f\ £** 3P •C0G055 • 000 10

4 01 .00 • 50766 • 000057 •00010 40 2. 50 • 52624 • 00006 8 • 000 10

4 C4 .0 0 •54799 • 000057 •000 10 405 • 50 •56861 .000032 •00010

4 C7 .0 C .58745 •000094 •00010 408 .50 • 60604 •000060 • 00010

4 10.00 •622 34 •0C00 38 •GOO 1

0

411 .50 •63656 •000068 •00010

4 1i .0 0 .64951 • CC0059 •000 10 414.50 .66131 c 000065 • 000 10

4 16.00 • 671 52 •000046 • 000 10 417. 50 •67987 • 00005 7 10

4 19.00 .68701 •000067 •00010 420* 50 .69555 .000103 .00010

4 22 .00 .701 51 •000030 •00010 423.50 .70430 • 00004 t •00010

4 25.00 .70965 •000033 •00010 4 26 .50 .71287 •000023 •00010

4 2o .00 .702 £5 •000049 •00010 429 .5 0 .63752 •000022 .00010

4 31.00 • 549 47 • 000024 • 000 10 432. 50 • 55 494 .00001 3 • 000 10

4 ?4 .00 • 55895 •0G0046 •000 10 435. 50 • 54368 •000026 .00010

4 17 .00 •52045 •000033 •00010 438 • 50 .49497 • 000054 •00010

4 41.00 •47901 •000032 .00010 441.50 .47848 .000021 •00010

4 43.CC • 48766 .C00036 •0001G 444 .50 •49576 •000022 •00010

4 46 .0 0 • 499 20 •C00C24 • 000 10 447.50 •50825 •000046 •000 10

4 49 .0 0 .53230 • 000030 .000 10 450. 50 • 56323 • 000034 .000 10

4 52 .00 •58958 •000041 .000 10 453. 50 • 60902 • 000039 •00010

4 55.0 0 •62269 •000032 •00010 456*50 •62779 • 000015 eOOOlO

4 56 .0 0 •622 18 •000031 •00010 459 .50 • 60829 •000019 •00010

4 61.00 •59143 • 000041 •00010 462*50 •57854 •000026 • 00010

4 64 .0 0 • 5 73 27 • C00014 • 000 10 465 • 5 0 • 5691

3

•000036 e Qui) 10

4 67.00 .55998 .000018 .00010 468. 50 .54595 •C00016 .00010

4 7C.C0 .53141 •000028 •00010 471*50 .51638 .000030 .00010

473.00 .50873 •000021 .00010 474.50 .53083 .000021 •00010

476.00 .55022 •C00031 .00010 477.50 .52368 .000028 ,00010

4 79.00 .50331 .000028 •00010 480,50 .49395 .C00037 ,00010

4 82.00 .49597 .C00022 •00010 483.50 .53422 .C00031 • 000 10

4 85.30 .59664 •000041 •00010 486.50 •65144 .000060 •00010

4 88.0 0 .693^8 .000055 .00010 489.50 .72897 .000037 .00010

491.00 .754 62 •000024 •00010 492.50 .76958 .000047 *00010

4 94 .00 .77582 .000044 .00010 495.50 .77650 .000051 •00010

497.00 .77208 •G00054 •00010 498.50 .76286 .000 025 •00010

Page 5 SRM 2010a

38
TABLE 4 (Continued) Transmittance (T) as a function of wavelength from 380 to 780.5 ntn for a bandwidth of 1.5 nm. The estimate* of random and systematic errors are also provided. These data are not certified.

Wavelength AT At

(nm) T Standard Error Systematic

5 00.0 0 .75007 • 000038 •00010

503.00 .71949 •000049 •00010

5C6.00 • 68654 •000029 •00010

5 09.0 0 •62231 •000040 •00010

512.00 .51720 •000029 •00010

515.00 •50708 •000031 •00010

518.00 •56851 •000043 •00010

521. CO .57231 •000036 •00010

524.00 •43269 •000017 •00010

527.00 .37679 .000020 •00010

530.00 .35279 •000016 •00010

533.00 •39916 • 000017 •00010

5 36 .GO •54124 •000035 •00010

5 39.0 0 •6810S •000047 •00010

5 42.0 0 .76653 • 000033 .00010

545.00 .81171 • OG0029 • 000 10 546.00 .83233 • 000043 •00010

5 51 .00 .83719 •000045 •00010

5 54. CO .83571 •000022 •00010

5 57.00 .83133 •000029 .00010

56U.Q0 •81679 • 000044 •000 10

5 63.00 .78036 •000034 •00010

5 66.00 •67208 •000029 •00010

569.00 .31171 .000019 •00010

572.00 •04466 •0000 20 •00010

5 75.0 0 •04138 •000008 •00010

5 76.0 0 •05465 • 000013 •00010

5 f 1 .00 .06696 .000015 •00010

584.00 .01915 .000006 •00010

587.00 .01731 •000007 •00010

590.00 •04605 .000019 •00010

5 93.00 .08229 •000008 •00010

5 96.00 •18771 •000025 .00010

599.00 •31676 •000014 •00010

6C2.00 .43501 •000046 .00010

6 05.0 0 .55363 •C00037 .00010

60S. 00 .63107 .000066 •00010

611 .00 •68896 •C00030 •00010

614.00 •78043 .000024 •00010

617.00 •84419 •000022 •00010

Page 6 SRM 2010a

Wavelength At At

(nm) T Standard Error Systematic 501 .50 .73534 •000045 •00010

504.50 •70383 •000045 •00010

507.50 •66262 .000024 •00010

510.50 .56707 •C00031 •00010

513.50 .49346 •000056 • 000 10 516.50 • 53946 •C00027 • 000 10 519.50 •58209 •000030 •00010

522.50 .51543 •000052 »00310

525.50 .39072 •000015 •00010

528.50 .35483 • 000018 • 00010

531.50 .37015 • 000025 •00010

534.50 •45853 • 00004 2 •00010

537.50 .61975 •000031 •00010

540.50 .72896 •G00044 •00010

543.50 .7932 5 •C00059 •00010

546.50 •82444 •000040 • 00010

549.50 .§3615 •000081 •000 10 552.50 •83660 • 00 0 048 •00010

555.50 •83426 •000029 •00010

558.50 •82586 •000025 •00010

561*50 •80277 • 000038 •00010

564.50 .74242 .000038 •00010

567.50 •53386 •000026 •00010

570.50 .11909 •000013 •00010

573.50 •03514 •000016 •00010

576.50 • 04 4 91 •000012 •00010

579.50 .06821 •000009 .00010

582.50 • 04148 •000013 •00010

585.50 .01262 • 000006 •00010

588.50 •03031 .000012 •00010

591.50 •06187 .000007 •00010

594.50 .12409 .00002 5 .00010

597.50 .25829 •000G21 .00010

600.50 .37306 .000031 .00010

603.50 •49640 .000049 .00010

606.50 .5992 5 •000042 .00010

609.50 .65692 .000042 .00010

612.50 .73245 .r>00043 ,00010

615.50 .82013 .00002 7 .00010

618.50 .85409 .000056 .00010

39
TABLE 4 (Continued) Transmittancc (T) as a function of wavelength from 380 to 780.S nm for a bandwidth of 1.5 nrn. The estimates of random and systematic errors are also provided. These data are not certified.

Wavelength At At Wavelength At At

(nm) T Standard Error Systematic (nm) T Standard Error Systematic 620.00 •854 00 •0000 56 .00010 621.50 .84757 .000045 .00010

6 23.0 0 •84081 .000045 •00010 624.50 .84027 •000029 •00010

626.00 •64212 •000048 •00010 627.50 •84185 • 000048 .00010

629.00 •83965 •000035 •00010 630.50 •84039 .00004 7 •00010

63*. 00 .84500 •000046 •00010 633.50 •85109 .000062 •00010

635.00 .85677 •000038 •00010 636.50 •86029 •000032 •00010

6 3E.C0 •86270 •000045 •00010 639.50 .86501 •000022 •00010

641.00 •86684 •000035 •00010 642.50 •86847 .000026 .00010

644.00 •86991 .000050 .00010 645.50 •87114 .000069 •00010

647.00 87189 •000053 •00010 648.50 .87232 .000097 •00010

65C.00 •87268 •000030 •00010 651.50 .87294 •000108 •00010

653.00 .87322 •000052 .00010 654.50 .87322 .000064 .00010

6 56.0 0 .87320 .000078 .000 1U 657.50 •87276 .C00059 •00010

6 59.00 .87216 .000017 •00010 660.50 •87106 .000029 .00010

6 62 .0 0 .86924 .000035 •00010 663.50 •86636 .000018 •00010

665.00 .86192 •000120 •00010 666.50 •85616 •000054 .00010

668.00 .84947 .000030 •00010 669.50 .84 2 7 3 •000043 •00010

671.00 .83688 •000020 .00010 672.50 .83157 .000038 •00010

6 74.0 0 •82668 .000032 .00010 675. 50 .820fc8 .000031 • 00010

677.00 .81184 •000039 •00010 678.50 .79967 •00005 8 • 00010

680.00 •78648 •000047 .00010 681.50 .77033 .000071 •00010

683.00 .75090 .000047 .00010 684.50 .73735 •000031 •00010

686.00 .74509 .0000 39 •00010 687.50 .76335 •000040 •00010

689.00 .77874 •000044 .00010 690.50 .79470 .000040 .00010

6?2 .00 .81070 •000036 .00010 693.50 .82509 • 000060 •00010

695.00 •83668 •000063 •00010 696.50 •84584 .000038 .00010

698.00 • 85296 •0C0065 .00010 699.50 •85807 .000074 •00010

7C1.00 •86156 .000057 .00010 702.50 •86388 .000070 •00010

704.00 .86559 •ooooso .00010 7C5.50 •86695 .000087 •00010

7C7.00 •86777 •000188 .00010 708.50 .86848 • 00006 9 • 00010

710.00 •86848 •000063 •00010 711.50 •86809 .000113 .00010

713.00 .86701 •000069 •00010 714.50 .86522 .000073 •00010

7 16.00 .86278 .000142 .00010 717.50 •85960 •000047 •00010

7 19.00 .85552 .000123 •00010 720.50 •85002 .000116 •00010

7 22.0 C •84260 •000084 •00010 723.50 .83304 .000031 •00010

7 2 5.00 .81990 .000114 .00010 726.50 .80031 .000070 •00010

726.00 .77176 .000077 .00010 729.50 .72617 .000057 .00010

7 31.0 0 .655 63 •000101 .00010 732 .50 •54 906 .000059 .00010

7 34.CC .41047 .000065 .00010 735.50 .27146 .000070 .00010

7 37.00 .17783 •000032 .00010 738.50 .14350 .000025 •00010

Page 7 SRM 2010a

AO
TABLE 4 (Continued) Transmittancc (T) as a function of wavelength from 380 to 780.5 nm for a bandwidth of 1.5 nm. The estimates of random and systematic errors are also provided. These data are not certified.

Wavelength AT At

(nm) T Standard Error Systematic 7*0.00 .14029 •000039 •00010

743 .00 •15422 •000013 •000 10

7 46 .00 •17950 •000044 •00010

7 49,00 •15817 •000026 •00010

7 52 #0 0 • 21 278 •000036 •00010

7 55 .00 • 30634 .000047 •00010

7 58 .0C •42896 .000027 •00010

761.00 •53598 •000089 •00010

764.00 •61508 •00006S .00010

767.00 .68350 •C00108 .00010

77u.0O .73432 .000079 .00010

7 73 .00 .76019 •000081 •0001C?

776. CO .764 38 •000145 •00010

779. CO .74102 .000081 .00010

Wavelength At At

(nm) T Standard Error Systematic 741 .50 • 14205 • 00002 7 •000 10 744.50 •17506 AAA All

• 000027 •00010

747.50 •16393 .000038 •00010

750.50 • 17714 nnnntn • POLIO 30 • 0001

u

753.50 •75589 •000065 •00010

756. 50 . 3659 0 .000050 •00010

759.50 •48660 •000056 .00010

762.50 .57747 .000099 •00010

765.50 ,65041 .000071 •00010

768.50 .71193 •000061 •00010

771.50 .75005 •000086 •00010

774.50 .76505 .000141 • 00010

777.50 .75658 • 000066 •00010

780.50 .71767 .000142 •00010

Page 8 SRM 2010a

41
Appendix A- 2 .

7

Rational ^mtm of ji»tandartte

(Eertifitate of Calibration

Standard Reference Material 2031

Metal-on-Quartz Filters for Spectrophotometry

This Standard Reference Material (SRM) is intended for use in the verification of the transmittance and absorbance scales of conventional spectrophotometers in the ultraviolet and visible regions of the electromagnetic spectrum. SRM 2031 consists of three individual filters in their metal holders and one empty filter holder. Two filters, having nominal transmittances of 10 and 30 percent, were produced by evaporating different thicknesses of chromium metal on 1.5-mm thick fused silica plates that had been precision ground and polished. These metal films are protected by 1.5-mm clear fused silica cover plates optically contacted to the base plates. The third filter is a single fused silica plate 3-mm thick, having a nominal transmittance

of 90 percent. The metal holders for these filters are provided with shutters to protect the filters when not in use. The shutters must be removed at the time of measurement and be replaced after the measurements have been completed. Each filter holder

bears a filter number (10, 30, or 90) and a set identification number.

Set and

Filter Ident. Number

TRANSMITTANCE (T)

Wavelength, nm

250.0 280.0 340.0 360.0 400.0 465.0 500.0 546.1 590.0 635.0

Set and

Filter Indent. Number

TRANSMITTANCE DENSITY (-logioT)

Wavelength, nm

250.0 280.0 340.0 360.0 400.0 465.0 500.0 546.1 590.0 635.0

Date of Certification:

Gaithersburg, MD 20899 October 22, 1984 (Revision of Certificates dated 6-1-79 and 9-20-82)

U. S. bepartrrierii of Commerce Malcolnt -Baldrige "Sectei^ry7 b»£ r I National Burwii ol*$tandards

Ernest Umblpr, Cjirector

Stanley D. Rasberry, Chief

Office of Standard Reference Materials

42
The transmittance values (T) can be converted to percent transmittance (%T) by multiplying by 100. The transmittance

densities were calculated from the measured transmittance (T). These transmittance densities should be indicated by the absorbance scale of the spectrophotometer when the filters are measured against air. All of the certified transmittance values were obtained by measuring against air at an ambient temperature of 23.5 °C. The uncertainty of the certified transmittance values of the two metal film filters is ± 1.0 percent. This uncertainty includes

0.5 percent for random and systematic errors of the calibration procedure, as well as 0.5 percent for possible changes in the transmittance with time. The total uncertainty of the certified transmittance values for the clear quartz plate is 0.5 percent

(see note below). The long-term stability of the filters with the chromium film has not been rigorously established. Measurements to date, however, suggest that the transmittance of the chromium-coated filters could change by as much as 0.5 percent in the first year after calibration. Therefore, this SRM should be returned to the National Bureau of Standards for

free verification of the transmittance values on the first anniversary of the certification date. Information regarding sub- sequent verifications or recalibrations, including costs for such service, will be included with this first verification report. Before returning this SRM to NBS, information regarding such shipment should be obtained from the Service Analysis Coordinator, Center for Analytical Chemistry, Room B222, Chemistry Building, National Bureau of Standards, Gaithers- burg, MD 20899. Telephone: (301) 921-2141. When not in use, the filters should be stored in their holders with the shutters in place and in the metal container provided for

this purpose. Extended exposure to laboratory atmosphere and dirty surroundings should be avoided. The transmittance measurements were made using the high-accuracy spectrophotometer designed and built in the NBS

Center for Analytical Chemistry [1]. This instrument is a primary transmittance standard; its transmittance accuracy was

established using the double-aperture method of linearity testing [1,3,5,6]. Transmittance measurements for SRM 2031 were made by producing the vertical image of the slit (about 8 mm by 1.5 mm),

using a convergent beam geometry with an aperture ratio f: 10, in the middle of the entrance face of the filter. The filters were measured in the spectrophotometer in a position perpendicular to the incident light beam. A spectral bandpass of 1 .6 nm was

used for measurements at all wavelengths. Because the transmittances of these filters exhibit an appreciable optical

neutrality, the dependence of transmittance on bandpass is not critical and wider bandpasses may be used in routine measurements. For a quantitative discussion of this subject, the user should consult reference 5, pp. 32 and 33. The transmittance, T, was measured against air in the reference beam; hence it includes the reflection losses that occur at the

air-filter interface. Under these circumstances the measured transmittance, T, has a corresponding transmittance density, defined as -logio T. The internal transmittance, Ti, of a material is defined as the transmittance of the material corrected for

reflection losses. This is obtained experimentally when the measurements are made against a blank sample in the reference beam. The absorbance, A, of a material is related to this internal transmittance, Ti, by the expression, A = -logioTj. The exposed surface of each filter is approximately 29 x 8 mm, measuring from a point 1.5 mm above the base of the filter holder (see figure). The empty filter holder provided is to be used in the reference beam of the spectrophotometer so that approximately equivalent conditions of stray radiation are achieved for both beams. The transmittance of the filters depends upon the intrinsic properties of the material, wavelength, spectral bandpass, geometry of the optical beam, temperature, and

positioning of the filter. While changes in ambient temperature of 1 or 2 °C from 23.5 °C have not significantly affected the

calibration, the effect of temperature variations exceeding 2 °C have not been investigated. Changes in the transmittance may be caused by surface conditions, aging of the material, exposure to a harmful atmosphere, or careless handling

[2,3,4,5,7]. SRM 2031 is stored in a black-anodized aluminum container provided with a threaded cap made of the same metal. Each

filter is placed in a cylindrical cavity to prevent any contact between the filter face and the walls of the storage container. Contamination of t^e filter surface with particulate matter due to static charges is minimized through the metallic nature of

the container. A fiat >af spring is inserted into the cylindrical cavity with each filter holder to minimize damage during

transportation. These springs can be removed during normal use in the laboratory. NOTE: In some commercial instruments, the metal-on-quartz filters can generate reflection effects in the sample compart- ment that can degrade the accuracy of the measured transmittances. During the development of SRM 2031, the presence and magnitude of reflection effects were studied and were found negligible, within the uncertainty specified,

in all spectrophotometers tested (see Ref. 5 page 4, pp. 16-30 for additional details of this study). However for certain instruments, these effects could become significant. If such effects are detected or suspected, the user should contact R.W. Burke, NBS Inorganic Analytical Research Division, for assistance and instructions.

Page 2 SRM 2031

43
The Alter is shown in the assembled unit with its front surface facing up. The filter, in its filter holder, should be placed in the cuvette compartment of the spectrophotometer with its front surface facing the incident light beam and the rear surface facing the photodetector.

Top: Cylindrical container with its screw cap, both made of black-anodized aluminum alloy. Four filter holders can be

stored in the cylindrical container. Bottom (from left to right): Aluminum alloy filter holder, 12.5 mm square and 58 mm

high; Metal-on-quartz filter; Retaining spring of beryllium-copper with nylon screw and washer; Assembled unit; and two

Delrin shutters. All metal and plastic parts are flat black.

Page 3 SRM 2031

44
Prior to certification measurements, each filter was examined for surface defects and the condition of the optical contact [5]. S hould the surface of the filter become contaminated, no attempt should be made to clean it unless the user has the facilities to demonstrate that the cleaning treatment will not alter the surface or degrade the accuracy of the certified values. As SRM

2031 is a transfer standard, the only means available to verify its integrity is to remeasure its transmittance with a primary

standard instrument similar to that used in this certification [1,5]. In most cases, where verification or recertification of the transmittance values is desirable, it will be most expeditious to return the filters to the National Bureau of Standards for measurement.

Further information concerning the selection, preparation, and properties of SRM 2031 will be found in reference 5. The research, development, and initial production of this SRM were conducted by R. Mavrodineanu and J.R. Baldwin, NBS

Inorganic Analytical Research Division. The transmittance measurements were performed by R.W. Burke and M.V. Smith, NBS Inorganic Analytical Research

Division. Technical leadership for the preparation and measurements leading to certification was provided by R.W. Burke. The overall direction and coordination of technical measurements leading to certification were performed under the chair- manship of J.R. DeVoe, NBS Inorganic Analytical Research Division. The technical and support aspects involved in the preparation, certification, and issuance of this Standard Reference

Material were coordinated through the Office of Standard Reference Materials by L.J. Powell. We wish to acknowledge the cooperation of George N. Bowers, Jr., M.D., of Hartford Hospital, Hartford, Connecticut; Royden N. Rand, Ph.D., of the Eastman Kodak Co. Research Laboratories, Rochester, New York; and Donald S. Young,

M.D., Ph.D., of the Mayo Clinic, Rochester, Minnesota. The contributions of H.E. Bennett and J.M. Bennett of the Michelson Laboratory, Physical Optics Branch, Naval Weapons

Center, China Lake, California, who helped in the initial production of SRM 2031 are also gratefully acknowledged.

References

1. R. Mavrodineanu, An Accurate Spectrophotometer for Measuring the Transmittance of Solid and Liquid Materials, NBS Journal of Research 76a, No. 5, 405-425 (1972).

2. R. Mavrodineanu, Solid Materials to Check the Photometric Scale of Spectrophotometers, NBS Tech. Note 544, O. Menis, and J.I. Shultz, Eds., pp. 6-17, U.S. Government Printing Office, Washington, D.C. 20402 (Sept. 1970); ibid, NBS Tech. Note 584, pp. 2-21 (December 1971).

3. K.S. Gibson, Spectrophotometry, NBS Circ. 484 (Sept. 1949).

4. R. Mavrodineanu, Considerations for the Use of Semi-Transparent Metallic Thin Films as Potential Transmittance Standards in Spectrophotometry. NBS Journal of Research 80A, No. 4, 637-641 (1976).

5. R. Mavrodineanu and J.R. Baldwin, Metal-on-Quartz Filters as a Standard Reference Material for Spectrophotometry, SRM 2031. NBS Special Publication 260-68, U.S. Government Printing Office, Washington, D.C. 20402 (1979).

6. K. D. Mielenz and K. L. Eckerle, Spectrophotometer Linearity Testing Using the Double-Aperture Method, Appl. Optics U, 2294-2303 (1972).

7. R.W. Burke and R. Mavrodineanu, Accuracy in Analytical Spectrophotometry NBS Special Publication 260-81, U.S. Government Printing Office, Washington, DC 20402 (1983).

Page 4 SRM 2031

45
Appendix A-2.8

U.S. Department of Commerce

luanita M. Kreps

Secretary

^National ^nunn of j^tantlartfe

(Eerttftcate

Standard Reference Material 2032

Crystalline Potassium Iodide

Heterochromatic Stray Radiant Energy Standard for

Ultraviolet Absorption Spectrophotometry

K. D. Mielenz and R. Mavrodineanu

This Standard Reference Material consists of reagent-grade, crystalline potassium iodide (KI) to be used to

assess heterochromatic stray radiant energy (stray light) in ultraviolet absorption spectrophotometers in the

spectral region below 260 nm. Stray light is assessed by measuring the spectral absorbance of aqueous solutions of S RM 2032 of known pathlengths and concentrations, and comparing the result with the certified values of the

specific absorbance, e. Specific Absorbance

8

e (L g" 1 cm"

1 ), vs Wavelength, A (nm), at 23.5 °C

A 240 245 250 255 260 265 270 275

e 25.6 10.67 3.66 1.05 0.260 0.0560 0.0121 0.0031

a "Specific absorbance" is defined here as absorbance per unit pathlength and unit concentration. The term "absorptivity" has been avoided

since it is ambiguously defined. See K. D. Mielenz, Anal. Chem. & 1093-1094 (1976). The estimated uncertainty of these values is ± 5%, which includes the random and systematic errors of the

calibration procedure, as well as variations due to possible instability of the KI. (See, Certification Procedure.) The material used to produce SRM 2032 was obtained from the J. T. Baker Chemical Co., Phillipsburg, N.J., in two bottles, as reagent-grade (99.8% purity) potassium iodide. SRM 2032 was issued with the technical assistance of J. R. Baldwin, R. W. Burke, A. L. Cummings, B. I. Diamondstone, and G. A. Sleater, and under the overall direction of I. L. Barnes. The technical and support aspects concerning preparation, certification, and issuance of this SRM were

coordinated through the Office of Standard Reference Materials by R. W. Seward.

Washington, D.C. 20234 George A. Uriano, Chief October 31, 1 979 Office of Standard Reference Materials

46
Supplementary Information

Material Testing: Material homogeneity was tested by measuring the absorbance of 1% aqueous solutions ofthe KI sampled from

the top, middle, and bottom of each bottle. These measurements, at 265, 267, and 270 nm, showed no evidence of

inhomogeneity. Tests for moisture content (Karl Fischer method) gave an average of 0.007%. This value was

sufficiently small that all certified data are based on weighed samples of the undried, as received, material.

Stability of the material to UV and visible light was tested by exposing the KI salt in a low-actinic glass bottle to radiation from a 3 kW xenon-arc lamp at a distance of 25 cm for four days at room temperature. The average absorbances at five wavelengths between 240 and 270 nm of aqueous solutions of the exposed material were

1.1% lower than those of solutions of the unexposed material. In view ofthe severity of this test, this change was

considered minor. Nonetheless, the 1.1% was included in the overall uncertainty of the certified values.

Certification Procedure: The certified specific absorbances were measured in the NBS Center for Analytical Chemistry high-accuracy spectrophotometer [1,2], equipped with a deuterium lamp and UV averaging sphere [3, 4]. Thirteen aqueous

solutions of KI with concentrations ranging from 0.03 to 30 g L

1 were prepared and measured against distilled water, using standard fused-silica cuvettes with pathlengths between 10.001 and 10.009 mm . The absorbance measurements were performed at the temperature, t = 23.5 ± 0.5 °C. A 0.2 nm bandpass was used, and

wavelength settings were made with an accuracy of 0.05 nm. The measurements were made on at least three concentrations at each wavelength. These concentrations were chosen so that most absorbance readings fell between 0.1 and 1.0 to minimize stray light and bandwidth errors. The data were found to obey Beer's law. Thus, the equation,

e = A/cC (1) was used to calculate the specific absorbances, e, from the measured absorbances, A, and the known values of

concentration, c, and pathlength, 9. . Limits to random error (two standard deviations) of these measurements (including the photometric

imprecision of the spectrophotometer, errors in the repositioning of cuvettes, concentration errors, pathlength

uncertainties, temperature errors, Beer's law uncertainties, and bandwidth errors) were determined to be ±

2.4%. The error due to the 0.05 nm uncertainty of the wavelength calibration of the spectrophotometer is ± 1.1%, The uncertainty of 5% stated on the face of this certificate represents the sum of these errors and the above

mentioned 1.1% uncertainty due to instability of the KI. No corrections were applied for the effects of internal

reflections inside the sample and reference cuvettes, nor were the weights corrected to vacuum. These and all other sources of error were considered negligible. The temperature coefficient at 260 nm was determined to be

-j- £ =0.03.°C-'.

(2)

For precision measurements, it is recommended that SRM 2032 be used in thermostated cuvettes at 23.5 °C, or

that a temperature correction according to Eq. (2) be applied.

b Issued by NBS as SRM 932, Quartz Cuvettes for Spectrophotometry.

47
Instructions for Use

Storage and Preparation: SRM 2032 should be stored in the original, low-actinic glass bottle and the cardboard container in which it was

issued to protect it from unnecessary exposure to light and humidity. When so stored, the expected stability of

this material is at least three years. Thus, until additional stability data are obtained, this material should be used

within three years of the date of purchase.

All solutions prepared from SRM 2032should be made in borosilicate glass containers using distilled water and

transfer pipettes (Pasteur type) of the same glass and fitted with rubber bulbs

c

. Use clean spectrophotometer

cuvettes, free of scratches, made of non-fluorescent fused silica, and fitted with ground-glass or Teflon stoppers

to minimize evaporation; or preferably use NBS SRM 932. Mark all cuvettes to assure the same orientation in the spectrophotometer, and place them into their respective holders. Using transfer pipettes of the type mentioned, rinse each cuvette several times with distilled water. Prepare a solution of KI in distilled water (e.g., 1%), fill the sample cuvette with the KI solution and the reference cuvette with distilled water. Measure the absorbance, leaving the cuvettes in their holders, empty them (using the pipettes), and repeat the rinsing and

filling operations until constant absorbance readings are obtained. Fresh solutions should be made before every

test. Measurements: A 1 % KI solution (c = 1 0 g L ') with a 1 cm pathlength exhibits a sharp cutoff in transmittance near 260 nm; i.e.,

it transmits more than 90% above 273 nm, but less than 0.01% below 258 nm. Therefore, with the monochromator set for a wavelength below 260 nm, any appreciable amount of light detected is heterochromatic stray light, which consists of wavelengths above the cutoff. The amount of stray light in the spectrophotometer at wavelength X may be determined from the equations:

T'fX) =

x(X) =

where:

T(X) + x(X)

(3)

1 + x(X) TTA)-T(A) (4) l-T'(X)

x(X) is the stray light ratio, T'(X) is the apparent transmittance * T(X) is the true transmittance. The stray light ratio, x(X), is the proportion of heterochromatic stray radiant energy in the spectrophotometer

for the wavelength setting X. Equation (4) forms the theoretical basis for the determination of the stray light ratio by comparing apparent transmittance to true transmittance. For SRM 2032, the true transmittance, T(X), of KI

solutions may be calculated as: T(X)=10-tWCS

where e(X) is the certified specific absorbance given on the face of this certificate.

c Soft glass containers and pipettes contain residual amounts of UV absorbing material, but can be used after proper cleaning. Several rinses,

first with isopropyl alcohol and then with distilled water, are generally adequate.

48
The apparent transmittances of KI solutions depend not only on the stray light ratio of the spectrophotometer,

but also on the wavelength accuracy and the spectral bandwidth, which can significantly affect the results obtained because of the steep slope of the absorbance cutoff of KI. A low-pressure mercury discharge lamp is suggested for verifying the wavelength scale, and a bandwidth as narrow as compatible with adequate signal-to- noise ratios should be used. Many instruments do not permit the direct measurement of transmittances below certain limits, e.g., 1% or

0. 1.. For such instruments, the use of SRM 2032 will only measure stray light ratios above these limits. To

measure stray light ratios below these limits, the reference beam of the spectrophotometer must be attenuated to extend the transmittance scale into the low-transmittance region.

References

1. R. Mavrodineanu, J. Res. NBS 76A, 405^25 (1972).

2. J.F. Barkley, F. C. Ruegg, and R. Mavrodineanu, 29th Pittsburgh Conf., Abstract 452, Cleveland, Ohio,

(1978).

3. K. D. Mielenz, R. Mavrodineanu, and E. D. Cehelnik, J. Res. NBS 78A, 631-635 (1974).

4. K. D. Mielenz, R. Mavrodineanu, and E. D. Cehelnik, Appl. Optics 14, 1940-1947 (1975).

49
U. S. Department of Commerce

Philip M. Klutznick

Secretary Appendix A-2 .

9

National Bureau of Standards

Ernest Ambler, Director ^National ^mmn of j^tandartb

(Eerttfttate

Standard Reference Material 2033

Crystalline Potassium Iodide with Attenuator

Heterochromatic and Isochromatic Stray Radiant Energy

Standard for Ultraviolet Absorption Spectrophotometry

K. D. Mielenz and R. Mavrodineanu

This Standard Reference Material consists of reagent-grade crystalline potassium iodide (KI) and a radiation attenuator

to be used to assess the heterochromatic stray radiant energy (stray light) in ultraviolet absorption spectrophotometers in the spectral region below 260 nm.. The radiation attenuator consists of two semitransparent evaporated metal-on-fused

silica (non-fluorescent) filters, each having a nominal transmittance of 10%. One filter is mounted in a cuvette-style holder that can be inserted into the sample compartment of the spectrophotometer. The other is mounted in one of the two shutters of the holder. The use of this attenuator permits the expansion of the transmittance scale into the lowtransmittance region by providing a two-step attenuation of the reference beam of the spectrophotometer to about 1%. The attenuator can also be used to assess isochromatic stray light by following the instructions given in this certificate. The heterochromatic stray light is assessed by measuring the spectral absorbance of aqueous solutions of S R M 2033 of known pathlengths and concentrations, and comparing the results with the certified values of the specific absorbance, e. Specific Absorbance

3

e (Lg ' cm '), vs Wavelength, A (nm), at 23.5 °C

A 240 245 250 255 260 265 270 275

e 25.6 10.67 3.66 1.05 0.260 0.0560 0.0121 0.0031

"Specific Absorbance" is defined here as absorbance per unit pathlength and unit concentration. The term "absorptivity" has been avoided since it is ambiguously defined. See K. D. Mielenz, Anal. Chem. 48, 1093-1094 (1976). The estimated uncertainty of these values is ± 5%, which includes the random and systematic errors of the calibration procedure, as well as variations due to possible instability of the KI. (See Certification Procedure.) The material used to produce SRM 2033 was obtained from the J.T. Baker Chemical Co., Phillipsburg, N.J., in two

bottles, as reagent-grade (99.8% purity) potassium iodide. The transmittance of the filter mounted in the holder at A255 nm is .

;

the transmittance of both filters at A255 is . SRM 2033 was issued with the technical assistance of J. R. Baldwin, R. W. Burke, A. L. Cummings, B. I. Diamondstone, and G. A. Sleater, and under the overall direction of E. L. Garner, NBS Inorganic Analytical Research Division. The technical and support aspects concerning preparation, certification, and issuance of this SRM were coordinated through the Office of Standard Reference Materials by R. W. Seward. Washington, D.C. 20234 George A. Uriano, Chief May 9, 1980 Office of Standard Reference Materials

50
Potassium Iodide Material Testing: Material homogeneity was tested by measuring the absorbance of 1% aqueous solutions of the KI sampled from the

top, middle, and bottom of each bottle. These measurements, at 265, 267, and 270 nm, showed no evidence of inhomogeneity. Tests for moisture content (Karl Fischer method) gave an average of 0.007%. This value was sufficiently small that all certified data are based on weighed samples of the undried, as received, material.

Stability of the material to UV and visible light was tested by exposing the KI salt in a low-actinic glass bottle to radiation from a 3 kW xenon-arc lamp at a distance of 25 cm for four days at room temperature. The average absorbances at five wavelengths between 240 and 270 nm of aqueous solutions of the exposed material were 1.1% lower than those of

solutions of the unexposed material. In view of the severity of this test, this change was considered minor. Nonetheless,

the 1.1% was included in the overall uncertainty of the certified values. Potassium Iodide Certification Procedure: The certified specific absorbances were measured in the NBS Center for Analytical Chemistry high-accuracy spectro- photometer [1,2], equipped with a deuterium lamp and UV averaging sphere [3,4]. Thirteen aqueous solutions of KI

with concentrations ranging from 0.03 to 30 g L were prepared and measured against distilled water, using standard

fused-silica cuvettes with pathlengths between 10.001 and 10.009 mm . The absorbance measurements were performed

at the temperature, t = 23.5 ± 0.5 °C. A 0.2 nm bandpass was used, and wavelength settings were made with an accuracy

of 0.05 nm. The measurements were made on at least three concentrations at each wavelength. These concentrations were

chosen so that most absorbance readings fell between 0. 1 and 1 .0 to minimize stray light and bandwidth errors. The data were found to obey Beer's law. Thus, the equation,

e = A/cl (1) was used to calculate the specific absorbances, e, from the measured absorbances, A, and the known values of concentration, c, and pathlength, I . Limits to random error (two standard deviations) of these measurements (including the photometric imprecision of the spectrophotometer, errors in the repositioning of cuvettes, concentration errors, pathlength uncertainties, temperature

errors, Beer's law uncertainties, and bandwidth errors) were determined to be ± 2.4%. The error due to the 0.05 nm

uncertainty of the wavelength calibration of the spectrophotometer is ± 1.1%. The uncertainty of 5% stated on the face of this certificate represents the sum of these errors and the above mentioned

1. 1% uncertainty due to instability of the KI. No corrections were applied for the effects of internal reflections inside the sample and reference cuvettes, nor were the weights corrected to vacuum. These and all other sources of error were

considered negligible. The temperature coefficient at 260 nm was determined to be 7

"

jjj = 0031 ° c"'- (2) For precision measurements, it is recommended that SRM 2033 be used in thermostated cuvettes at 23.5 °C, or that a temperature correction according to Eq. (2) be applied.

b Issued by NBS as SRM 932, Quartz Cuvette for Spectrophotometry. SRM 2033 Page 2

51
Instructions for Use of Potassium Iodide Storage and Preparation: SRM 2033 should be stored in the original, low-actinic glass bottle and the cardboard container in which it was issued

to protect it from unnecessary exposure to light and humidity. When so stored, the expected stability of this material is at

least three years. Thus, until additional stability data are obtained, this material should be used within three years of the date of purchase.

All solutions prepared from SRM 2033 should be made in borosilicate glass containers using distilled water and transfer

pipettes (Pasteur type) of the same glass and fitted with rubber bulbs

0

. Use clean spectrophotometer cuvettes, free of

scratches, made of non-fluorescent fused silica, and fitted with ground-glass or Teflon stoppers to minimize evaporation;

or preferably use NBS SRM 932. Mark all cuvettes to assure the same orientation in the spectrophotometer, and place them into their respective holders. Using transfer pipettes of the type mentiond, rinse each cuvette several times with

distilled water. Prepare a solution of KI in distilled water (e.g., 1%), fill the sample cuvette with the KI solution and the reference cuvette with distilled water. Measure the absorbance, leaving the cuvettes in their holders, empty them (using

the pipettes), and repeat the rinsing and filling operations until constant absorbance readings are obtained. Fresh

solutions should be made before every test. Measurements: A 1% KI solution (c = 10 g L ') with a 1 cm pathlength exhibits a sharp cutoff in transmittance near 260 nm; i.e., it transmits more than 90% above 273 nm, but less than 0.0 1 % below 258 nm. Therefore, with the monochromator set for a wavelength below 260 nm, any appreciable amount of light detected is heterochromatic stray light, which consists of wavelengths above the cutoff. The amount of stray light in the spectrophotometer at wavelength X may be determined from the equations: T(X) + x(X)

T'(X) = —— — 1 + x(X)

(3)

x(X) = T'(A)-T(A) (4)

1 - T'(X) where:

x(X) is the stray light ratio, T'(A) is the apparent transmittance, T(A) is the true transmittance. The stray light ratio, x(A), is the proportion of heterochromatic stray radiant energy in the spectrophotometer for the wavelength setting A. Equation (4) forms the theoretical basis fo>- the determination of the stray light ratio by comparing

apparent transmittance to true transmittance. For SRM 2033, the true transmittance, T(A), of KI solutions may be

calculated as: T(X)= 10~

e(X)c£ where e(X) is the certified specific absorbance given on the face of this certificate.

"Soft glass containers and pipettes contain residual amounts of UV absorbing material, but can be used after proper cleaning. Several rinses, first with

isopropyl alcohol and then with distilled water, are generally adequate. SRM 2033 Page 3

52
The apparent transmittances of KI solutions depend not only on the stray light ratio of the spectrophotometer, but also on the wavelength accuracy and the spectral bandwidth, which can significantly affect the results obtained because of

the steep slope of the absorbance cutoff of KI. A low-pressure mercury discharge lamp is suggested for verifying the wavelength scale, and a bandwidth as narrow as compatible with adequate signal-to-noise ratios should be used.

Optical Attenuator: Many instruments do not permit the direct measurement of transmittances below certain limits, e.g., 1% or 0.1%. To

measure stray light ratios below these limits, the reference beam of the spectrophotometer must be attenuated to extend

the transmittance scale into the low-transmittance region. As mentioned on the face of this Certificate, the optical attenuator consists of two filters, each of which has a nominal

transmittance of 10 percent. One filter is mounted in a metal holder that can be inserted in the sample compartment of

the spectrophotometer (5). This holder is provided with a front and rear shutter, one of which has a window in which the second filter is mounted. The holder and shutters are flat black. This unit was produced in the NBS Instrument Shops.

Instructions for Use of the Attenuator

This unit can be used to attenuate the incident radiation in the reference beam of the spectrophotometer in two steps by a total factor of about 100, corresponding to about 1 percent transmittance (6). To attenuate by a factor of 10, the attenuator is inserted in the sample compartment of the spectrophotometer facing the incident beam, with both shutters removed. A further attenuation by a factor of about 10 is obtained when the shutter carrying the second filter is inserted

in the holder, in front of the first filter. Under these conditions, and with an instrument that cannot measure trans- mittances lower than 1 percent, the use of the attenuator will permit heterochromatic stray light to be measured down to about 0.01 percent. This attenuation procedure can be used with spectrophotometers capable of scale expansion. Isochromatic Stray Light: The radiation attenuator can be used to assess the isochromatic stray light that results from reflection of the incident radiation at the surface of the sample and various optical components, and reaches the photodetector without passing through the sample. It is implicitly assumed that the sample compartment of the spectrophotometer is light-tight. The measurement is performed by placing the attenuator in the sample beam of the spectrophotometer, with the opaque shutter placed at the rear of the filter holder. Under these conditions, if a signal is detected, it is caused by

reflection at the surface of the filter exposed to the incident radiation. This radiation is scattered from the walls and other components of the sample compartment and reaches the photodetector without passing through the sample (5). This

signal is the isochromatic stray light. Isochromatic stray light, which passes through the sample, is generally caused by interreflections between lenses and/ or

other sample compartment elements. Tests for this stray light component, which is not detected by the methods described above, are discussed in references 7 and 8.

References:

1. R. Mavrodineanu, J. Res. NBS 76A, 405-425 (1972).

2. J. F. Barkley, F. C. Ruegg, and R. Mavrodineanu, 29th Pittsburgh Conf, Abstract 452, Cleveland, Ohio, (1978).

3. K. D. Mielenz, R. Mavrodineanu, and E. D. Cehelnik, J. Res. NBS 78A, 631-635 (1974).

4. K. D. Mielenz, R. Mavrodineanu, and E. D. Cehelnik, Appl. Optics 14, 1940-1947 (1975).

5. R. Mavrodineanu, J. Res. NBS 80A, 637-641 (1976).

6. Estimating Stray Radiant Energy, ASTM Manual on Recommended Practices in Spectrophotometry, pp. 94-105,

3rd. Edition, 1969, 1916 Race St., Philadelphia, Pa. 19103.

7. K. D. Mielenz, J. Res. NBS 76A, 455-467 (1972).

8. K. D. Mielenz and R. Mavrodineanu, J. Res. NBS 77A, 699-703 (1973). SRM 2033 Page 4

53
U. S. Department of Commerce

Malcolm Baldnge

Secretary Appendix A-2.10

National Bureau of Standards

Ernest Ambler. Director Rational ^mmn of jiiattdartte

Certificate

Standard Reference Material 2034

Holmium Oxide Solution Wavelength Standard

From 240 to 650 nm

This Standard Reference Material (SRM) is intended as a reference material for establishing the accuracy of the wavelength scale of conventional spectrophotometers in the spectral range 240 to 650 nm. It consists of a solution of 4 percent holmium oxide in 10 percent perchloric acid in water, sealed in a nonfluorescent fused silica cuvette of nominal 10 mm

light path. (The cuvette fits most conventional spectrophotometers; see note 1.) The cuvette should be handled only by

the tubular end, and, while not in use it should be stored in the container provided. The certified wavelengths of minimum transmittance, expressed in nanometers, are given in Table 1 for six spectral bandwidths from 0. 1 to 3.0 nm

for 14 bands. They are illustrated in Figure 1. The estimated uncertainty of the measured minimum transmittance wavelengths is believed to be no greater than ±0.1 nm at the measurement temperature of 25 °C ±5 °C, and includes

the random and systematic errors of the measuring procedure. For details concerning the materials, instrumentation, and method used in the certification of SRM 2034 the user is referred to NBS Special Publication 260-102. This Special Publication also describes the influence of purity and concentration of the holmium oxide solution and temperature, and describes the procedure used for assessment of the wavelengths of minimum transmittance and the establishment

of the accuracy of the wavelength scale of the spectrometer used. The initial research at NBS concerning the potential use of the H02O3 - HCIO4 solution as a wavelength standard was

performed by K.D. Mielenz and R.A. Velapoldi. The transmittance measurements given in this certificate and investigations on the various chemical and physical para- meters that might influence the results were performed by V. R. Weidner and R. Mavrodineanu. The overall direction and coordination of the technical measurements leading to certification were performed under the chairmanship of K.D. Mielenz, NBS Radiometric Physics Division, Center for Radiation Research. The technical and support aspects involved in the issuance of this Standard Reference Material were coordinated through the Office of Standard Reference Materials by R.L. McKenzie and L.J. Powell.

Gaithersburg, MD 20899 Stanley D. Rasberry, Chief June 20, 1985 Office of Standard Reference Materials

54
CAUTION:

If the cuvette of SRM 2034, which contains holmium oxide as well as perchloric acid, is accidentally broken, the following action should be taken: "Perchloric acid spills should be diluted immediately with water, taken up with swabs (preferably wool) and then washed

with generous amounts of water. The swabs should also be washed with water before discarding. Swabs of cotton or other cellulose material contaminated with perchloric acid should be regarded as fire or explosion hazards if not washed

thoroughly with large amounts of water" (1,2).

References:

(1) Schilt, Alfred A., Perchloric Acid and Perchlorates, the G. Frederick Smith Chemical Co., Publisher, 867 McKinley

Ave., Columbus, Ohio 43223, pg. 157 (1979).

(2) Schumacher, Joseph C, Perchlorates, Their Properties, Manufacture and Use, Reinhold Publishing Corp., NY; Chapman & Hall, LTD, London, pg. 187 (1960). NOTES:

(1) If the cuvette is too tall for the sample compartment of the spectrophotometer, a piece of black opaque cloth can be used to provide a temporary lightproof enclosure.

(2) The cuvettes have been individually tested for leaks. Should a leak subsequently develop, follow the procedure recommended above (under "CAUTION").

Table 1 Wavelengths of Minimum Transmittance at Six Spectral Bandwidths for a 4 Percent Holmium Oxide Solution in 10 Percent Perchloric Acid in Water. Minimum Spectral Bandwidths (nm)

Transmittance Band No. 0.1 0.25 0.5 1 2 3

1 240.99 240.97 241.01 241.13 241.08 240.90

2 249.83 249.78 249.79 249.87 249.98 249.92

3 278.15 278.14 278.13 278.10 278.03 278.03

4 287.01 287.00 287.01 287.18 287.47 287.47

5 333.47 333.44 333.43 333.44 333.40 333.32

6 345.55 345.55 345.52 345.47 345.49 345.49

7 361.36 361.35 361.33 361.31 361.16 361.04

8 385.45 385.42 385.50 385.66 385.86 386.01

9 416.07 416.07 416.09 416.28 416.62 416.84

10 451.30 451.30 451.24

11 467.82 467.82 467.80 467.83 467.94 468.07

12 485.28 485.28 485.27 485.29 485.33 485.21

13 536.54 536.53 536.54 536.64 536.97 537.19

14 640.51 640.49 640.49 640.52 640.84 641.05

55
56
NBS-114A (rev. 2-8C) 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-26 0/102 July 1986

4. TITLE AND SUBTITLE Holmium Oxide Solution Wavelength Standard From 240 to 640 nm - SRM 2034

Victor R. Weidner, Radu Mavrodineanu, Klaus D. Mielenz,

Ranee A. Velapoldi, Kenneth L. Eckerle, Bradley Adams

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions) 7. Contract/Grant No. NATIONAL BUREAU OF STANDARDS DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered GAITHERSBURG, MD 20899

Final

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State, ZIP)

Same as item #6.

10. SUPPLEMENTARY NOTES

Library of Congress Catalog Card Number; 86-600560

| | Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most si gnificant information. If document includes a significant bibliography or literature survey, mention it here) The work describes the methods and procedures used to determine the

wavelengths of minimum transmittance of holmium oxide in perchloric

acid solution. Measurements of spectral transmittance of the solutions

were made by means of a high precision spectrophotometer over the

wavelength range 200 nm to 680 nm. The wavelength scale accuracy of

this instrument was verified by extensive measurements of mercury and

deuterium emission lines. The measurements of spectral transmittance

of the holmium oxide solutions were made as a function of temperature,

purity, concentration, and spectral bandwidth. Analysis of the

uncertainties associated with these parameters and the uncertainties

associated with the calibration of the instrument wavelength scale

and the data analysis have resulted in an estimated uncertainty of

tO.l nm for the determination of the wavelengths of minimum

transmittance of the holmium oxide solution.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons) holmium oxide; spectral bandwidth; spectrophotometer calibration;

spectral transmittance; wavelength calibration; wavelength standard

13. AVAILABILITY

fX] Unlimited

| | For Official Distribution. Do Not Release to NTIS

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

20402. Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

67

15. Price

1SCOMM-DC 6043-P80

* U.S. Government Printing Office: 1986 0-491-070 (40127)



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