A UNITED STATES DEPARTMENT OF COMMERCE

PUBLICATION

A

l

Rational Bureau of Standaras

Library, E-01 Admin. Bldg.

DEC 2 2 1969

NBS TECHNICAL NOTE 502

H^SlBB

Activities of the

NBS Spectrochemical

Analysis Section

July 1968 to June 1969

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANOAF
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards ' was established by an act of Congress March 3, 1901 . Today,

in addition to serving as the Nation's central measurement laboratory, the Bureau is a principal

focal point in the Federal Government for assuring maximum application of the physical and

engineering sciences to the advancement of technology in industry and commerce. To this end

the Bureau conducts research and provides central national services in four broad program

areas. These are: (1) basic measurements and standards, (2) materials measurements and

standards, (3) technological measurements and standards, and (4) transfer of technology.

The Bureau comprises the Institute for Basic Standards, the Institute for Materials Research, the

Institute for Applied Technology, the Center for Radiation Research, the Center for Computer

Sciences and Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United

States of a complete and consistent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and

uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of an Office of Measurement Services and the following technical

divisions:Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic and Molecular Physics—Radio Physics -—Radio Engineering -—Time and Frequency -—Astrophysics - —Cryogenics.

THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to im- proved methods of measurement standards, and data on the properties of well-characterized materials needed by industry, commerce, educational institutions, and Government; develops,

produces, and distributes standard reference materials; relates the physical and chemical properties of materials to their behavior and their interaction with their environments; and provides

advisory and research services to other Government agencies. The Institute consists of an Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote

the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations in the development of technological standards, and test methodologies; and provides advisory and research services for Federal, state, and local government agencies. The Institute consists of the following technical divisions and

offices: Engineering Standards—Weights and Measures — Invention and Innovation — Vehicle Systems Research—Product Evaluation—Building Research—Instrument Shops—Measurement Engineering—Electronic Technology—Technical Analysis.

THE CENTER FOR RADIATION RESEARCH engages in research, measurement, and application of radiation tlo the solution of Bureau mission problems and the problems of other agencies and institutions. The Center consists of the following divisions: Reactor Radiation—Linac Radiation—Nuclear Radiation—Applied Radiation. THE CENTER FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and

provides technical services designed to aid Government agencies in the selection, acquisition, and effective use of automatic data processing equipment; and serves as the principal focus

for the development of Federal standards for automatic data processing equipment, techniques,

and computer languages. The Center consists of the following offices and divisions: Information Processing Standards—Computer Information — Computer Services — Sys- tems Development—Information Processing Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and

accessibility of scientific information generated within NBS and other agencies of the Federal government; promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader aspects of the National Measure- ment System, and provides appropriate services to ensure that the NBS staff has optimum accessibility to the scientific information of the world. The Office consists of the following

organizational units:

Office of Standard Reference Data—Clearinghouse for Federal Scientific and Technical Information : ' —Office of Technical Information and Publications—Library—Office of Public Information—Office of International Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

- Located at Boulder. Colorado 80302.

:l Located at 5285 Port Royal Road. Springfield, Virginia 22161.
UNITED STATES DEPARTMENT OF COMMERCE

Maurice H. Stans, Secretary

NATIONAL BUREAU OF STANDARDS • Lewis M. Branscomb, Director

NBS TECHNICAL NOTE 502

ISSUED DECEMBER 1969

Nat. Bur. Stand. (U.S.), Tech. Note 502,108pages (Dec. 1969)

CODEN: NBTNA

Activities of the

NBS Spectrochemical Analysis Section

July 1968 to June 1969

Edited by Bourdon F. Scribner

Spectrochemical Analysis Section

Analytical Chemistry Division

Institute for Materials Research

National Bureau of Standards

Washington, D.C. 20234

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

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

(Order by SD Catalog No. CI 3.46:502), Price $1 .00
FOREWORD

The Analytical Chemistry Division was established as a separate division at the National Bureau of Standards on

September 1, 1963* and became part of the Institute for

Materials Research in the February 1, 1964, reorganization.

It consists at present of nine Sections and about 100 technical personnel encompassing some 45 different analytical

competences from activation analysis and atomic absorption to

vacuum fusion and x-ray spectroscopy. These competences, and

in turn the Sections which they comprise, are charged with

research at the forefront of analysis as well as awareness of

the practical sample, be it standard reference material or

service analysis. In addition it is their responsibility to

inform others of their efforts

Formal publication in scientific periodicals is a highly

important output of our laboratories. In addition, however,

it has been our experience that informal, annual summaries of

progress describing efforts of the past year can be very valuable in disseminating information about our programs. A word

is perhaps in order about the philosophy of these yearly

progress reports. In any research program a large amount of

information is obtained and techniques developed which never

find their way into the literature. This includes the

"negative results" which are so disappointing and unspectacular but which can often save others considerable work. Of

importance also are the numerous small items which are often

explored in a few days and which are not important enough to

warrant publication — yet can be of great interest and use to

specialists in a given area. Finally there are the experimental techniques and procedures, the designs and modifications

of equipment, etc., which often require months to perfect and

yet all too often must be covered in only a line or two of a journal article.

li
Thus our progress reports endeavor to present this information which we have struggled to obtain and which we

feel might be of some help to others . Certain areas which

it appears will not be treated fully in regular publications

are considered in some detail here. Other results which are

being written up for publication in the journal literature

are covered in a much more abbreviated form.

At the National Bureau of Standards publications such

as these fit logically into the category of a Technical

Note. In 1969 we plan to issue these summaries for all of

our Sections. The following is the fifth annual report

on progress of the Spectrochemical Analysis Section.

W. Wayne Meinke, Chief

Analytical Chemistry Division

111
PREFACE

This is the fifth in a series of annual progress reports of the Spectrochemical Analysis Section of the Analytical Chemistry Division. The Section is concerned with

instrumental elemental analysis, especially for those

spectroscopic techniques that are capable of multi-element

determinations. These include optical, x-ray, and mass

spectroscopy

.

Chemical elements are uniquely identified by the

characteristic frequency of emitted spectra, and amounts

present can be determined by measurement of the intensity of

emitted radiation. However, many factors enter into

successful spectral analysis and must be carefully controlled

These include, in optical and x-ray spectrometry, the

production of radiant energy by excitation, the dispersion of

radiant energy into a spectrum, and the measurement of

spectral wavelengths and intensities. In a similar way,

spark source mass spectrometry involves ion formation,

dispersion into a mass spectrum, and measurement of

intensities for recorded masses. In general these are

methods of comparative analysis in which calibration by

synthesized or analyzed standards is required.

The research program of the Section is directed largely

toward a better understanding of the phenomena involved in

producing and measuring optical and x-ray emitted energy and

mass spectra, and the improvement of spectrochemical methods,

instruments, and calibration procedures. Included in the

work of the Section are the development of appropriate

standard reference materials, analyses of materials to assist

other research projects, and literature surveys such as

bibliographies and critical reviews.

IV
The purpose of this report is to review the program,

facilities, and accomplishments of the Section for the

past year.

In order to specify procedures adequately, it has been

necessary occasionally to identify commercial materials and

equipment in this report. In no case does such identification imply recommendation or endorsement by the National

Bureau of Standards, nor does it imply that the material

or equipment identified is necessarily the best available

for the purpose.

Bourdon F. Scribner, ' Chief

Spectrochemical Analysis Section

v
TABLE OF CONTENTS

PAGE

1. INTRODUCTION 1

A. Facilities 1

B. Activities 2

2. OPTICAL SPECTROMETRY 7

A. High-aperture Spectrograph 8

B. Microanalysis in the DC Arc 14

CComputer Programs 16

D. Future Computer Applications 18

E. Applications to Analysis 23

1. Standard Reference Materials 23

2. Other Analyses 26

3. ELECTRON PROBE MICROANALYSIS 30

A. Quantitative Analysis 30

B. Standard Reference Materials 31

C. Non-diffractive Techniques of Qualitative and

Semi-quantitative Analysis 34

D. New Technique and Instrumentation for Target

Current Scanning 38

E. Further Improvements in Target Current

Scanning 40

F. Color Composite X-ray Scans 44

G. Applications to Analysis 45

H. Literature Research 46

4. X-RAY FLUORESCENCE SPECTROMETRY 47

A. Research Activities 47

B. Applications 49

C. Contributions of NBS Personnel 51

5. SPARK SOURCE MASS SPECTROMETRY 52

A. Instrument Modifications 52

1. Source Pump 52

2. New Pump for Plate Prepump Section .... 53

VI
PAGE

B. Use of 100-mesh Grids to Remove Matrix

Line Broadening 54

C. Plate Development ..... 56

D. Homogeneity Testing of Iron in High Purity

Gold SRM 685 59

E. Analysis of High Purity Materials 60

F. Survey Analysis of a Steel Sample °1

G. Trace Characterization of Spark Source Ion

Samples of SRM Platinum 68l 64

1. Introduction 64

2. Results 64

3- Discussion 68

6. PRE CONCENTRATION TECHNIQUES 70

A. High Purity Metals 70

B. Ingot Iron and Steels 71

C. Simulated Lunar Glasses 72

D. Ultra-Pure Liquid Reagents 73

7. PERSONNEL AND ACTIVITIES 74

A. Personnel Listing 74

B. Publications 75

C. Talks Given 77

D. Committee Activities 80

8. ACKNOWLEDGMENTS 82

9. LIST OF REFERENCES 83

APPENDIX: Typical certificates for NBS Standard

Reference Materials "5

A. SRM 682 High-Purity Zinc 85

B. SRM 683 Zinc Metal 87

C. SRM 685 High-Purity Gold 89

D. SRM 481 Gold-Silver Wires for Microprobe

Analysis 91

E. SRM 1051b Barium Cy clohexanebutyrate 95

F. SRM 1159, 1160 Electronic and Magnetic Alloy

Standards . 97

G. SRM 1800 Microstandard Ion-Exchange Beads . . 99

Vll
LIST OP FIGURES

FIGURE NO. PAGE

1. Microphotometer tracings of 3100 A region of

spectra of NBS SRM 1161 9

2. Diagram of circuit for observation of timeresolved and time-integrated spectral

intensities 11

3. Emission intensity vs time for the Cu 3247 A

line with laser-plus-spark excitation .... 13

4. Emission intensity vs time for the Cu 3247 A

line excited by the laser without spark ... 13

5. Analytical functions fitted by two operators

using the program CFIT2 17

6. Drop of anomalous water, approximately 1 yg . . 28

7. Same sample of anomalous water after sampling

with the laser probe 28

8. Integral measurements of intensities of Ca Ka

and S Ka from ion exchange resin beads loaded

with Ca 35

9. Non-diffractive spectra obtained at 20 keV and

2 x 10~° A, in 4 minutes 3d

10. Spectrum of a Cu-Au alloy obtained with the

silicon detector, and reconstructed on the

Curve Resolver 37

11. Schematic diagram of the target current amplifier with linear and derivative component . . 39

12. Target current signal ^0

13. Target current scans of titanium boride contaminated with iron ^1

14Scanning target current image of human

tooth . . . .' ^ 2

15. Target current of metal grids 43

16. Scanning electron micrograph of a partially

recrystallized lamp filament ^4

viii
PAGE

17« Determination of Ni in Ni-Fe-Cr-Co alloy by

x-ray fluorescence 50

18. Rebuilt source pumping system 54

19. New pumping system for photographic plates . . 55

20. Exposures of Pt SRM 681 with and without a 100-mesh Au grid 56

21. Mass spectrum of Pt SRM 681 without grid, using

Cavard's developer 57

22. Mass spectrum of Pt SRM 68l with grid, using

D-19 developer 58

23. Mass spectrum of Pt SRM 68l with grid, using

Cavard's developer 58

24

.

Normalized ion beam measurements of trace

elements in spark source ion sample Pt

SRM 65

LIST OP TABLES

TABLE NO.

1. Standard reference materials of interest for

spectrometric applications 5

2. Detection limits by the semi-micro arc method

(0.5 nig sample) and the copper spark .... 15

3. Proposed low alloy steel SRM 24

4. Analyses of copper-gold alloys by nondispersive

detection and pulse height analysis 38

5. X-ray absorptiometric analysis of metal foil

synthetic standards 48

6. Homogeneity tests for iron in gold SRM 685 • • 59

7. Analysis of high-purity tin SRM 74l 61

8. Mass spectrometric survey analysis of steel

using a standard 62

IX
PAGE

9. Mass spectrometric survey analysis of steel

using estimated sensitivity factors 63

10

Interdependence of trace element fluctuations

in spark source ion sample of Platinum SRM

681 67

11. Analysis of spark source ion samples Platinum

SRM 681 69
ACTIVITIES OF THE NBS SPECTROCHEMICAL

ANALYSIS SECTION

July 1968 through June 1969

Edited by Bourdon P. Scribner

ABSTRACT

Spectrochemical research activities, improvements in

equipment j and applications are summarized. In optical

emission spectrometry micro methods were investigated and

computer programs were completed for fitting analytical

curves. In electron probe microanalysis studies of corrections for quantitative analysis and new gains in non-diffractive analysis and target current scanning were made. X-ray

absorptiometry was applied to the analysis of thin metal

foils and computer programs were improved for correction of

x-ray fluorescence analysis . Chemical pre-concentration of

impurities combined with isotope dilution spark source mass

spectrometry found increased application in accurate trace

analysis. Resolution of the mass spectrometer was improved

and the behavior of ion samples was studied. Extensive involvement in the standard reference materials program contributed to certification of several SRM's including high

purity Zn and Au, two sets of wires, Au-Ag and Au-Cu, for

microprobe analysis, and electronic and magnetic alloys.

Listings are given of 21 publications and 29 talks by members

of the Section during the year.

Key words

:

Analytical curve functions, color composite, computer

programs, electron probe, gold analysis, isotope dilution

method, laser probe, metal foil analysis, microanalysis, nondiffractive x-ray spectra, optical spectrometry, platinum

analysis, preconcentration techniques, spark source mass

XI
spectrometry, spectrochemical analysis, spectrograph, standard

reference materials, steel analysis, target current scanning,

trace analysis, x-ray absorptiometry, x-ray fluorescence

analysis, x-ray scans.

xii
1. INTRODUCTION

In the four preceding annual reports in this series

[1,2,3 9 A] we have described the facilities and program of

the Section in some detail and references to the past reports will be found in several places in the current report.

Copies of the earlier reports are available on request. In

each report, the research activities and the output in terms

of publications, talks given, and analytical work have been

recorded. This report follows the same format to present

a description of our efforts and accomplishments for the past

year. In the introduction we will summarize the major activities of the Section.

A. Facilities

The major equipment of the Section includes the following.

3-meter Eagle mounting grating spectrograph

3.4-meter Ebert mounting grating spectrograph

21-foot Wadsworth mounting grating spectrograph

2-meter multi-channel optical spectrometer

3-meter multi-channel optical spectrometer

1.5-meter multi-channel vacuum optical spectrometer

0.75-meter Ebert mounting, scanning spectrometer

0.75-meter Czerny-Turner mounting spectrograph/spectrometer

Mult i- channel x-ray fluorescence spectrometer

Single-channel vacuum x-ray fluorescence spectrometer

Electron probe microanalyzer with 3 x-ray spectrometers

Spark source mass spectrograph

Accessory equipment includes microphotometers , sample

preparation devices, microscopes, teletypewriter readout

devices, etc. One facility that we continue to find highly

useful to our work is a teletypewriter terminal located in

our laboratory and connected by wire to a remote time-sharing

computer service. The NBS computer facility is available for

1
large batch-loading jobs such as calculations on studies of

homogeneity of standard reference materials

During the past year no major equipment accessions were

made although certain spectrometric equipment, such as the

multi-channel x-ray spectrometer, should be considered for

replacement in the near future. Improvements in existing

equipment were made to obtain better speed, resolution, or

new applications. These include an efficient illuminating

system for the high-speed Czerny-Turner mounting spectrograph,

use of non-diffract ive detector system and improved target

current scanning in electron microprobe analysis, and

improved pumping systems for the spark source mass spectrometer .

B. Activities

The laboratory is organized into four major groups with

the personnel listed in section 7 of this report. The groups

are optical spectrometry, x-ray spectrometry, spark source

mass spectrometry, and enrichment techniques. In addition

to 15 full-time employees, there are usually 3 to 4 summer

assistants who have contributed effectively to the program.

Two persons were supported by outside agencies: Dr. Jean

Henoc, guest worker, from the Centre National d'Etudes des

Telecommunications, France, and Barry L. Hammond, research

associate, from the Naval Ship Research and Development Center,

Annapolis, Md

This year a research contract on Counterpart Funds was

monitored by our Section. The contract work, located at the

Atomic Energy Commission, Soreq, Israel, under Mrs. Sima Held,

was applied to trace analysis problems relating to standard

reference materials

The activity of the Section is divided approximately

equally between (1) general research and development and

(2) service activities involving spectrometric analyses for

2
certification of standard reference materials, analyses

for other projects at NBS , and development and analyses for

other Government laboratories. Research activities are

directed toward improvements in spectrometric instrumentation

and methods of analysis leading to increased sensitivity,

precision, and accuracy. This involves the study of sources

of error and the development of models and devices for correction of measurements to arrive at more accurate results

Because of complexities in calibration and corrections, considerable reliance is placed on high speed computer operations.

In optical spectrometry a high-aperture spectrograph

was applied to microanalysis by laser initiated spark discharges, and microanalysis in the dc arc was improved by a

special technique for handling small samples, less than 1 mg.

Because of the importance of automated operations in emission

spectroscopy, considerable attention was given to completing

work on two computer programs, one for computations in calibration of photographic emulsions and the other for computations for fitting analytical functions, the mathematical

equivalent of analytical curves . Following this work a critical survey of future computer applications was made and is

discussed in this report

The effort in electron probe microanalysis continued with

strong emphasis on the study of corrections for quantitative

analysis; this resulted in an extensive FORTRAN sub-program

for determining the effect of fluorescent radiation excited

by the continuum. Another program was developed for computations involved in multi-point homogeneity tests on a micro

scale. The latter was applied in the characterization of

two sets of wires for microprobe standard reference materials.

Other studies included non-diffractive techniques for rapid

qualitative and semi-quantitative analysis by the microprobe

and a new technique for target current scanning. Finally,

improvements were made in color composite x-ray scanning

images by including topographic information.

3
X-ray spectrometry was extended to the area of x-ray

absorptiometry which proved to be applicable to simultaneous

determination of the composition and mass per unit area of

thin metal foils. Improvement was made in the program for

calibration and correction for interelement interferences in

x-ray fluorescence analysis.

The resolution and sensitivity of spark source mass

spectrometry were improved for cases where weak lines appear

close to strong lines of the major constituent. The gain in

resolution is well illustrated in a series of tracings.

Analyses of high-purity materials with respect to the performance of the mass spectrograph were studied, especially

for the analysis of platinum, gold, and tin.

Methods for the preconcentration of impurities combined

with isotope dilution and spark source mass spectrometry have

proved highly effective for the analysis of high-purity

materials. These methods involve deposition of the concentrated impurities on gold wires which serve as electrodes in

the mass spectrograph. The methods were applied to the

analysis of platinum, zinc, and gold. The methods were

extended to the determination of trace elements in ingot iron

and are being investigated for application to the analysis

of glass and chemical reagents

The effort in standard reference material characterization has been especially effective this year. The analysis

of standards often poses severe problems which generate research and development in the Section. It will be of Interest

to summarize the status of work on numerous standards on which

we are engaged.

The Section contributed a major effort to the certification of 21 standard reference materials issued during the

year. These standards, of special utility in spectrometric

analysis, are listed in Table 1.
Table 1. Standard reference materials of interest for

spectrometric applications

SRM No. Title

High puri ty metals

:

682* High Purity Zinc

683* Zinc Metal

728 Intermediate Purity

685* High Purity Gold

Zinc

Date Issued

July 1968

July 1968

July 1968

September 196I

Microprobe standards:

480 Tungsten-20# Mo alloy

481* Gold-Silver Wires

482 Gold-Copper Wires

Organo-metallic for oil analysis

1051b* Barium Cyclohexanebutyrate

1055b Cobalt Cyclohexanebutyrate

1057b Dibutyltin Bis ( 2-ethylhexanonate)

1069b Sodium Cyclohexanebutyrate

1079b Tris (1-phenyl-l, 3-butanediono) iron (III)

1080a Bis (1-phenyl-l, 3-butanediono) copper (II)

10 66a Oct apheny ley clot etrasiloxane

November 1968

February 1969

June 1969

July 1968

July 1968

August 1968

February 1969

February 1969

February 1969

April 1969

Biomedical standards:

912 Urea

913 Uric acid

914 Creatinine

915 Calcium Carbonate

September 196!

September 196I

September 196I

March 1969

Metal alloys

1159,1160* Electronic and Magnetic Alloy

Standards February 1969

Micros tandard:

1800* Ion-Exchange Beads

Calcium Loaded March 1969

*Certificate reproduced in Appendix
Selected typical certificates have been reproduced in

the Appendix to this report, as indicated in the footnote

to Table 1. The contributions of analysts to the certification work are acknowledged on the certificates.

Other SRM's of interest for calibration in spectrometric

analysis are in course of preparation and certification.

Included are a set of five special steels to replace the

earlier NBS low-alloy steels, two soda lime glasses in plate

form, glasses for impurity elements, three high temperature

alloys, and several biomedical and metallo-organic standards.

Analyses made by the groups in the Section during the

12-month period June 1, 1968 through May 31 , 1969 are as follows .

Method

Optical emission

Electron microprobe

X-ray fluorescence

Spark source mass

Total 851 19,209 172

These analyses include both service work and characterization of standard reference materials. Descriptions of some

especially interesting analyses are given at appropriate

places in the report.

B. F. Scribner

Samples Det erminations Reports

691 11,607 117

42 6,202 21

91 601 22

27 799 12
2. OPTICAL SPECTROMETRY

During this year, work has been completed on the testing

of computer programs for calibrating photographic emulsions

and for fitting analytical curves. The development and testing of these programs has given new insight into the problems.

As a result of this work, two manuscripts have been prepared

which describe both the methods of computation and other

scientific results of the study.

Looking ahead to future developments, a study has been

made of potential benefits of more elaborate computations in

spectrochemical analysis, since modern computers make it

possible to carry out such computations in a short time and

at a very reasonable cost. It was concluded that it will be

desirable to develop instrumentation which will permit the

scientist to obtain very much more data from an emission spectrum than is possible with existing equipment. A reasonable

extrapolation of earlier work here and in other laboratories

indicates that further automation can greatly improve the

speed and accuracy of spectrochemical analysis while reducing

the human effort

.

Installation of a new spectrometer/spectrograph for use

with the laser probe source, and also with other weak light

sources, is essentially complete, and studies of its capabilities are underway. The new instrumentation has already made

it possible to detect seven elements in a speck of dust, about

20 ym on a side and estimated to weigh about 0.1 ug.

A dc arc method has been developed for samples weighing

a few tenths of a milligram. This method is needed for

samples which are too small for normal arc analysis, requiring

several milligrams, yet are larger than the microgram samples

normally analyzed by the electron microprobe or the laser

probe. The semi-micro method has detection limits comparable

to those obtained with copper spark excitation, but has the

advantage that solid samples can be analyzed conveniently.

7
Determination of the accuracy and precision of the semi-micro

method are not complete, but preliminary results are encouraging.

Approximately 50 percent of the effort in optical spectrometry has been devoted to the characterization of standard

reference materials and to service analyses for other projects

at NBS.

A . High-aperture Spectrograph

The last publication in this series [4] showed an f/6 .

3

spectrograph which had just been installed, primarily for

use with the laser probe but also for work with other lowintensity light sources. The auxiliary components of this

spectrograph have now been received, except for an achromatic

lens, and installed. The achromatic lens, which is being

fabricated in the NBS optical shop, will be needed when uniform

slit illumination is required for quantitative analysis

The auxiliary components which have been installed include

the Cassegrain collimator for efficient illumination of the

spectrograph and electronic circuitry permitting time-resolved

spectroscopy of the laser plume and/or the spark. An arc/spark

stand has also been purchased for use with other light sources.

It has been specially modified so that it can be used with the

Cassegrain collimator.

Figure 1 gives a direct comparison of spectra recorded

on the f/6.3 Czerny-Turner spectrograph (lower trace) and the

21-ft. Wadsworth spectrograph previously used with the laser

probe. The spectra were taken nearly five years apart, but

every effort was made to duplicate the excitation conditions

The sample was NBS Standard Reference Material 46l, a low-alloy

steel containing 1.73$ nickel. The spectral region scanned

on the plates includes the 3100 A iron triplet, which was a weak feature in these spectra because the spark was operated

at maximum capacitance and voltage and minimum inductance and
%T

Figure 1. Microphotometer tracings of 3100 A region of

spectra of NBS SRM Il6l. Spectra were photographed on a 21-ft. Wadsworth-mount spectrograph (upper curve) and a 0.75-m CzernyTurner-mount spectrograph (lower curve).
resistance, thus favoring lines of the ionized atoms. The

scanning speed of the microphotometer was twice as fast for

the Wadsworth spectrograph as for the Czerny-Turner spectrograph, in order to compensate for the difference in linear

reciprocal dispersions of the two instruments (5 vs 10 A/mm).

The triplet could just barely be seen by eye on the plate

taken on the Wadsworth spectrograph. This is confirmed by

the upper tracing in Figure 1, where the peak heights are

only two to three times the noise level of the photographic

plate (103-0). The background in the exposure is not detectably different from the clear, unexposed portion of the plate

In contrast, the lower trace, of the plate taken on the new

spectrograph, shows the triplet as a prominent group of lines

on a background having a transmittance near 50%, which is

approximately the optimum background level for detection of

a weak line [5 ] • Two nickel lines appear on the lower trace, while on the

upper trace one of these lines is absent and the other appears

only slightly above the noise level. To the right of the

3101 A nickel line on the upper trace, there appears another

apparent line of equal intensity. This line does not show

up on the lower trace, and no line could be found in the standard wavelength tables which would be expected to show up in

this position under the exposure conditions used. In fact,

this apparent line is probably noise.

Figure 1 also shows the loss in resolution that can be

expected with the spectrograph of lower dispersion. Because

of the high light-gathering power of the new spectrograph,

the exposures could have been made with a narrower slit, thus

improving the resolution. In this case, the use of a narrower

slit would not have helped very much, since the resolution is

largely controlled by the granularity of the fast emulsion

used to photograph the spectra (103-0 plate). With a stable

light source and photoelectric recording, or with a finegrained emulsion such as SA-1, the spectrograph is capable

10
of clearly resolving the iron triplet.

The electronic circuitry for time-resolved spectroscopy

was designed and built by Mr. Walter Brenner of the Electronic

Instrument Section of NBS . Figure 2 shows a schematic diagram of the circuit. The low-level signal from the photomultiplier goes first to a preamplifier which is contained

within the photomultiplier housing; this avoids problems

which might have been encountered if the low-level signal were

carried out to an amplifier, due to pickup of noise from the

flashlamp or the spark. The signal from the preamplifier is

amplified further and sent to both the Y-axis input of the

oscilloscope and to an integrator.

Y-AXIS

DELAYED

•TRIGGER

VARIABLE

DELAY

800-1100 yS

30-SECOND

HOLD

GENERATOR

METER

PULSE FROM

LASER HEAD

Figure 2. Diagram of circuit for observation of

time-resolved and time-integrated spectral

intensities

11
The oscilloscope sweep and the integrator are both

controlled by an electrical pulse from the laser head. This

pulse triggers the flashlamp, and it thus comes at a fixed

time before lasing. The pulse from the laser head goes directly to the sweep trigger of the oscilloscope; the oscilloscope has an adjustable delayed sweep. The pulse also

goes through a 800- to 1100-ys delay and to a 30-s hold generator. This results in a signal to the integrator which is

delayed relative to the pulse from the laser head and lasts

for 1/2 minute.

In the absence of this control signal, the integrator

operates. However, the small dark-current signal from the

photomultiplier bleeds off as fast as it arrives, and no net

integrated signal is indicated. The arrival of a larger signal from the photomultiplier causes the meter to show the

accumulated signal. On arrival of the control pulse, the

meter locks on the signal and holds it until the control

signal ends 30 s later.

Figures 3 and 4 illustrate the performance of the circuit in time-resolved spectroscopy. They are tracings of

the course of intensity with time for the Cu 3247 A line with

a sample of copper metal in the laser probe source. Because

of the high intensity of this line, much of the light signal

was deliberately wasted (by removing the Cassegrain collimator)

and the amplifier was operated at a low gain. Figure 3 shows

a tracing, at a sweep rate of 10 ys/large division, of the

intensity when the laser is operated with spark cross-excitation. Figure 4 shows the course of intensity with time, at

the same sweep rate, for the laser plume without cross excitation.

The time resolution achieved with this circuit is about

0.3 ys, as gauged by viewing the dark-current noise pulses

on the oscilloscope. Even at the most sensitive amplifier

settings, no pickup of noise could be seen on the oscilloscope trace or the integrator when the laser and spark were

12
Figure 3- Emission intensity vs time for the Cu 3247 A

line with laser-plus-spark excitation. Sweep

rate was 10 ms for the trace width.

Figure 4. Emission intensity vs time for the Cu 3247

line excited by the laser without spark.

Sweep rate same as in Figure 3-

13
fired but the slit of the spectrograph was closed.

Successful operation of this circuitry will allow us to

study in detail the course of events in the laser plume , with

and without spark cross-excitation. The information thus

obtained should be helpful in improving the efficiency of excitation. Data published by Piepmeier and Malmstadt [6]

suggest that the spark may be triggered by arrival at the

electrodes of a cloud of electrons moving ahead of the atoms

and ions from the sample. If this tentative finding is confirmed by further studies, it appears that it will be necessary to arrange for a new way of triggering the spark so that

the discharge is held off until the arrival of the sample

cloud

B . Microanalysis in the DC I\rc

Frequent need arises in this laboratory for the semiquantitative analysis of microscopic samples, weighing considerably less than the 5 to 25 mg normally needed for a spectroscopic analysis. Some are materials which are inherently

difficult to prepare, such as an isotopically-enriched lead

which we have recently analyzed. Another type of sample

recently analyzed was the very small amount of ash obtained

by dry ashing a 40-g sample of pure polymer.

We have for some time been using a semi-quantitative

method of analysis based on dilution of the sample with gallium

oxide. This has been successful with larger samples, but with

smaller samples the detection limits were not always satisfactory . Modification of the method has allowed us to obtain

improved detection limits for these small samples

The material to be analyzed, up to 1 mg, is placed in a polytetraf luorethy lene (Teflon) capillary tube, 2 mm long,

with the bottom sealed by a small piece of wax film. Up to

1.5 mg of gallium oxide, depending on the sample weight,

is added, and the tube is placed in the crater of a 1/8-in.

14
electrode. The sample Is arced at 5 A for 5 s and 15 A for

15 s In an atmosphere of 70% - 30% Ar. The spectra are

recorded photographically on a 3-^-ni Ebert-mount spectrograph.

Typical detection limits for a 0.5 mg sample with this

method are listed in Table 2. They are given in nanograms of

the elements, for direct comparison with the data of Nachtrieb

[7] for the copper spark method. The copper spark method

is more sensitive for some elements and less sensitive for

others, but the dc arc method has the advantage that the sample

does not have to be dissolved.

Table 2. Detection limits by the semi-micro arc method

(0.5 mg sample) and the copper spark.

Element L imit of De t ec t ion (nanograms

)

DC arc Copp er spark

Cu 0,.5

Fe 25 50

Mg 20 1

Mn 10 2

Ni 10 10

Zn 50 200

The good sensitivity of the dc arc method probably arises

from a combination of factors . It is likely that fluorine

from the capillary tube assists in the vaporization of some

of the elements through the formation of volatile fluorides

.

The gallium oxide may also act as a carrier, although its

primary purpose is to provide a common matrix. The use of a

small electrode reduces the time for total sample evaporation,

thus keeping background to a minimum. The controlled atmosphere also helps to reduce background.

15
The detection limits can sometimes be improved by appropriate modification of the method. For example, with the use

of an undercut electrode and a lower arc current, the detection

limits for cadmium and zinc can be reduced by about a factor

of four. However, this gives poorer detection limits for

some of the other elements.

It may also be possible to further reduce the amount of

sample required by the use of a high-aperture spectrograph.

It is for this reason, among others, that the f/6 . 3 spectrograph purchased for use with the laser probe has been

equipped with an arc/spark stand.

C . Computer Programs

Previous Annual Reports [2, 3 5 4] have mentioned some of

the computer programs that have been developed for spectrochemical analysis. NBS Technical Note 407 [8] describes some

of the applications, and the Supplement to this Technical Note

lists several of the programs together with detailed descriptions of the computation procedures and instructions for use.

Two manuscripts have been prepared which describe in

detail the computations and evaluate the results obtained.

One paper [9] is concerned with the program KAISER for the

computations in calibration of photographic emulsions. Extensive tests have shown that the procedure will give good results

with most emulsions employed in spectrochemical analysis,

provided that the microphotometer is in good adjustment.

A second paper [10] is concerned with procedures for

fitting analytical functions, the mathematical equivalent of

analytical curves. The programs used for this purpose by us

are of two types. In one group of programs, which differ

primarily in the form of output, the computations are carried

out on a computer permitting conversational-mode operation,

and decisions on the form of the equation and whether or not

to reject any of the standards are made by the user. The

16
BASIC program DRFIT and the FORTRAN program PRESTO include

algorithms for making these decisions, and can be used with

a batch-operated computer.

Neither procedure for fitting analytical functions is

flawless. In this laboratory we must frequently develop new

methods of analysis, and it occasionally happens that the

calibration data are poorly correlated. When this happens,

the functions selected are not always acceptable. This can

also happen in other laboratories; the calibration data

plotted in Figure 5 are taken from ref. [11]. The two curves

drawn in the figure are those selected by two users of the

program CFIT2, one of the programs employing conversationalmode operation and decisions by the user. In this case,

neither user noted that the standard of lowest silicon content gave a point which did not fit on the same curve as the

points for the other standards. The objection to the functions

-j 0.1 -

0.01 I L

"1 1 1

1 1' 1

1 1

' 1

1 1 1

1

1 11

1

1 1 r

J i I i I i I i I i I i_ J i I I I L

400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 SPECTROMETER READING

Figure 5. Analytical functions fitted by two operators

using the program CFIT2. third-degree

polynomial; fourth-degree polynomial.

Data from ref. 11.

17
is that the sign of the slope changes within the calibration

range. The program PRESTO rejected the lowest standard and

selected a straight-line equation through the remaining points.

The new program CFIT3 is a modification of CFIT2 to

assist in recognition of unacceptable functions. The relatively

slow printing rate of the teletypewriter makes it prohibitive

to plot each of the equations which are fitted in the first

part of the program. The program has been modified to give

an optional plot of the function finally selected. However,

all equations are checked for either a region of zero slope

or a change in the sign of the slope within the calibration

range. If either condition is found, a warning is printed

to alert the user.

Both CFIT3 and PRESTO are being used routinely in this

laboratory, and have proved to be extremely helpful. The

choice of program depends on the amount of data to be processed.

When there is little data, the program CFIT3 on the time-sharing

computer gives the results within a few minutes . When there

is much data, the printing rate of the teletypewriter becomes

a serious limitation, and the program PRESTO is then used on

a batch-loading computer.

One advantage of the use of the computer for this purpose

is that it allows a quantitative estimate to be made of the

accuracy of the analysis, which may often be poorer than the

precision. This estimate of accuracy is based on the assumption

that the samples behave like the standards. Thus, the scatter

of the standards around the function is a measure of the

accuracy of the analyses

D. Future Computer Applications

Currently, digital computers have been used in spectrochemical analysis principally to automate existing methods of

measurement and computation. These applications have been

highly rewarding, particularly when there are many samples to

18
be analyzed or the results must be obtained In a very short

time. However, the full power of the modern computer Is not

being used, and considerable advances in this direction are

likely

.

The Analytical Chemistry Division of NBS has been giving

attention to the role of computers in chemical instrumentation

in order to plan for the future. As a part of this effort,

we have been giving consideration to probable computer applications in spectrochemical analysis. An invited talk at the

recent Pittsburgh Conference [12] gave an opportunity to present the results of these considerations. The talk has been

written up for publication in Part B of Spectrochimica Acta.

The following is a summary presentation.

An emission spectrum has a large information content.

It is possible to resolve several thousand lines on a single

photographic plate. Little of this information is now being

used in spectrochemical analysis. Typically, intensities are

measured for one line of each analyte plus one, or sometimes

a second, internal standard line. In photographic methods,

the background may be measured next to each line, to allow a correction to be made. In photoelectric spectrometry, it has

become common to measure the background intensity at one wavelength and to use this meager information to correct for

background at wavelengths up to several hundreds of angstroms

away . Only a minimum of computation is normally done with these

minimum data. A calibration curve or calibration function is

constructed and used to convert the measured intensities to

element concentrations. Computer methods generally follow

the graphical techniques, although the computer is sometimes

used to make some corrections for interelement effects.

Present techniques make it possible to record much more

data than the minimum normally measured. Automated microphotometers have been built in several laboratories and they

are now available commercially. With these instruments it is

19
feasible to record the entire spectrum in digital format,

thus making the complete information content available for

use. The amount of digital data is very large, ranging from

50,000 to 1,000,000 words of data to digitize 10 in. of

spectrum, depending on the resolution required. The microphotometer can be made to record the data in a reasonable time,

and it should be possible to build the microphotometer so that

data are recorded only in the significant portions of the spectrum in order to reduce the amount of data to be carried forward

to the next step in the chain.

In the long run, the automated microphotometer will not

be satisfactory for all applications. The time needed to

develop and read the plate is much too long for many qualitycontrol laboratories. Photoelectric recording of spectra is

faster and more precise. The present photoelectric spectrometers, which either have multiple exit slits or scan through

the spectrum, are not capable of recording data at hundreds to

thousands of wavelengths in a reasonable time. The use of

television cameras to record emission spectra appears to be

feasible, and television techniques have been used in a few

specialized applications, largely for low-resolution spectra

of weak light sources [13, 1^]. Eventually, a television

detector will be wanted for spectrochemical analysis, but

such an instrument does not now exist, while the automated

microphotometer is a reality.

It is not inexpensive to record large amounts of data,

and before instruments to do this are built or purchased it

is necessary to decide how the large amounts of data will be

used and whether or not the extra cost is justified. A few

possible applications are fairly obvious. One is to record

many lines for each analyte, rather than one. It will then

be possible to average these semi-Independent determinations

to gain improved precision. The individual determinations

may be compared before being averaged, so that aberrent data

20
can be recognized and rejected, thus improving accuracy.

Intensity data may be recorded over a wavelength range, not

merely at the line center, so that a check can be made for

interfering lines even when these are so close that they

only change the shape or width of the analytical line.

If the cost of programming can be justified, it should

be possible to automate the process of examining the spectral

plate for a qualitative analysis. The computer program would

have to incorporate many decisions, locating the sensitive

lines of the elements, finding confirming lines, and checking

for possible interferences. The cost of writing such a program

will be high, but it would eliminate human error from a now

very tedious job.

Further programming may make the automated analyses at

least semi-quantitative. A skilled spectroscopist is now

able to estimate concentrations from the line intensities,

taking into account past experience with similar materials to

the one being analyzed. A paper by L. de Galan [15] has

explored the possibility of estimating element concentrations

from line intensities without comparison standards by using

more of the information that is in the spectrum. Briefly, he

used this information to determine the temperature and electron

density in an arc plasma, and combined these data with physical

constants in a set of equations which were established according

to a particular physical model of the process by which the

sample is evaporated and excited in the arc. The method was

tested with only a few samples, but the agreement between the

element concentrations estimated and the true values was about

as good - + 35% - as for other semi-quantitative methods

de Galan' s method of carrying out an analysis without

standards may never be more than semi-quantitative, but a combination of a few standards and corrections based on the

measured temperature and electron concentration in the discharge plasma may give quantitative analyses which are more

accurate than is now possible.

21
Attention should be given, also, to the application of

more extensive computations to the reduction of the small

quantities of data now being taken on spectrographs and

spectrometers. An early study in this direction has been

made by Aslund and Cronhjort [16]. Rather than estimating

the concentration of each element from the intensity at one

wavelength, they used a set of simultaneous equations, each

containing terms relating the intensity at one wavelength to

the concentrations of all of the elements in the sample.

They showed that a significant improvement in the accuracy of

analysis could be achieved in this way, and further study of

such techniques is clearly warranted. Similar techniques have

proved to be useful in x-ray fluorescence spectroscopy [17]

and should be in emission spectroscopy as well.

Digital computers have already transformed some scientific

subjects. The determination of a crystal structure by x-ray

diffraction once required two to three years, but the time for

the same task has now been reduced to as little as one week

through the use of computers in data acquisition and computation. In emission spectroscopy, the advantage to be sought

is not primarily speed, though savings in time have already

been achieved with computers, but in improving the precision

and accuracy of analysis. Also, automation of the more

tedious jobs, such as qualitative analysis, will free skilled

spectroscopists for other work.

The advantages that can be expected from increased automation are important enough that it appears inevitable that

efforts along these lines will be a major part of our research

in the next several years . The Spectrochemical Analysis

Section will be involved in this work, but the effort is

large and a cooperative program may be indicated. For this

reason, the general direction of proposed research is being

publicized, in the hope that comments and counter-proposals

will be received from interested readers.

22
E . Applications to Analysis

In addition to the research activities described in this

report, the Section provides analytical assistance to other

research groups at NBS and to other Government agencies.

These activities include homogeneity testing and analyses of

Standard Reference Materials, and service analyses for a wide

variety of materials from other groups . For the period July

1968 through June 1969, analyses were performed by optical

emission spectroscopy involving 691 samples, 11,607 determinations, and 117 reports.

1. Standard Reference Materials

The program of Standard Reference Materials has been and

will continue to be an important activity of the Section.

This activity consists of three phases; first, an analysis

for acceptance of composition, second, a study of homogeneity

of the material, and third, a participation in the program

of analysis for certification.

Nearly all of the materials, including tnose not intended

for use as composition standards, are submitted for semiquantitative analysis for 50 or more elements. This screening

process will give information regarding purity and approximate

composition, and is often sufficient for acceptance or rejection of a material. Typical materials inspected in the past

year include metallo-organic compounds, organic compounds for

metallic impurities (urea, creatinine, bilirubin), clay, tin,

gold-copper binary wire, calcium carbonate, tungsten, and

various ferrous alloys

.

In other cases however, a more accurate quantitative

analysis for acceptance of a material is necessary. An

illustration of this would be the five new low-alloy steel

standards now being produced as replacements for the nearly

depleted 1161-1168 set. The chemical composition of each of

the five materials has been chosen to provide adequate ranges

23
for each of 36 elements to be certified. Since these standards

will be used as a group, it is important that the aim compositions be achieved in the material finally accepted. The

material of each was cast from a vacuum induction furnace

melt of 7 1/2 tons into a 2 1/2-ton ingot and a 5-ton ingot.

The smaller ingot will provede for the chemical chip standard

and the larger for 1 1/4-in. diameter x 3/4-in. thick spectrochemical standards. Ladle samples taken during the casting

of the ingots were carefully analyzed by two or more independent methods to provide a basis for acceptance or rejection

of the melt. The preliminary analysis of one of the proposed

standards and the individual results of the complementary

methods used are shown in Table 3-

Table 3- P roposed low alloy steel SRM

Aim Optical X-ray Other

Element Composition Emission Fluorescence Chemical

Wt . Percent

C 0.40 0.37 — 0.38 a

Mn .60 .67 0.66 .656

b

P .015 .017 -- .016°

S .015 .013 -- .012 d

Si .20 .22 .20 —

Cu .05 .048 — .044b

Ni 2.00 2.00 1.99 —

Cr 0.70 0.69 0.68 —

Mo .20 .21 .192 —

W .02 .02 — .015

b

Co .02 .023 — .025

b

a - Combustion-gravimetric; b - Neutron activation analysis;

c - Spectrophotometries d - Combustion-iodometric . Other elements determined but not shown include V, Ti , As, Sn, Al , Nb

,

Ta, B, Pb, Zr, Sb, Bi , Ag, Ca, Mg, Se, Te , Zn, , N , H , Ce,

La, Pr, Ge.

24
Following the acceptance of composition we are next involved in the homogeneity testing of the material. The 2 1/2-

ton ingot is press forged and rolled into 5-in. diameter by

30-in. long bars. Slices from both ends of all the bars are

obtained and analyses are made on these slices to determine

the homogeneity of the individual bars and of the entire lot.

Subsequent chipping and blending of the material is made on

those bars which are shown to be acceptable to provide for the

chemical Standard Reference Material. The 5-ton ingot is

press forged and rolled into a slab 17 in. wide by 5 in. thick

and by approximately 30 ft. long. Cross section slices are

sawed from the slab at specific locations and the homogeneity

of the entire slab is determined by an analysis of variance

program. After discarding the unwanted portion of the slab,

i.e., material corresponding to the top center of the cast

ingot, the remainder is rolled into 1 1/4-in. diameter bars

to provide for the spectrochemical Standard Reference Material

Finally, the Section is involved, along with the entire

Analytical Chemistry Division, in the program for chemical

analyses of the finished material. Analyses by at least two

independent methods within our Section, along with other

analyses made at NBS, and by cooperators in industry provide

for the provisional and final certification.

Materials intended as standards for spectrochemical

analysis which have been analyzed in the above described

manner during the past year include the special low alloy

steels, stainless steel, high silicon steel, high temperature

alloys, and electronic and magnetic alloys. A copy of the

provisional certificate for the electronic and magnetic alloys

is included in the Appendix to this report .

25
2 . Other Analyses

Spectro chemical analyses are made of a wide variety of

materials to assist other NBS groups and other Government

agencies when their facilities are not capable of doing the

work. Many of the analyses are qualitative or semi-quantitative

surveys in which 50 to 70 elements are sought. Quite often,

these analyses provide sufficient information for the problem.

Typical samples analyzed in the past year by these methods

were dust, ash, resins, corrosion products, metallic alloys,

and chemical reagents. In one case, a 40-g sample of a pure

polymer was ashed with care to avoid contamination or losses,

and the small residue was analyzed by the semi-micro dc arc

method, yielding detection limits for many elements as low

as 10 pg/g.

A particular application of semi-quantitative analysis

involved the determination of sub-microgram amounts of beryllium in dust collected on filter paper, as part of a safety

surveillance program. The samples were ashed in a cupped

electrode, excited in a dc arc, and the intensity of the Be

3130.4 A line was recorded photoelectrically . Standards were

prepared by adding solutions of beryllium sulfate to filter

paper. The range of concentrations covered was 0.01 to 1.0 ug.

The method was rapid enough to permit handling of several

hundred samples, and at the same time gave adequate accuracy

and precision, particularly since even an approach to the

hazard level for beryllium would have been the signal for

work to be stopped and the contaminated area to be cleaned up.

Quantitative analyses are frequently performed to determine

whether or not a part of a machine or structure is the alloy

specified by the designer. Such analyses are usually part of

a detailed failure study made at NBS. An example of this is

the investigation of the causes of collapse of the bridge on

the Ohio River at Point Pleasant, West Virginia on December 15,

1967. A section of an eyebar in which the initial fracture

26
apparently occured was analyzed, along with several other

pieces of the bridge, to verify alloy composition. Another

example is the analysis of an aluminum propellor hub which

failed, causing the loss of an aircraft . Other examples

include the analysis of a magnesium anode and a steel guard

rail for the District of Columbia Department of Highways and

Traffic, analyses of aluminum sheet used in mail handling

equipment, and analyses of three steel files for the General

Services Administration. In this last example, the files

were submitted with the information that one of them had been

found to have a useful life about ten times greater than the

other two. Spectrochemical analysis revealed that the superior

file was a different alloy. Large quantities of these files

are being used in power-driven filing machinery, and the specification of a particular alloy can result in considerable

savings to the government.

Among the unusual materials resulting from research

activities at NBS this year, which we have been called upon

to analyze, was one called "anomalous water." This material,

which is prepared by a simple procedure discovered by B. V.

Deragin [18], has highly unusual properties. It is about 15

times as viscous as water, has a density 20 to 30 percent

higner, and does not boil until the temperature reaches 200°C.

It forms a glassy solid at -50°. The problem of analyzing

this material for possible metal content is complicated by

the fact that it can be prepared at present only in very small

amounts, with a typical sample weight of about lug.

Samples were analyzed with the laser probe and the electron probe microanaly zer . Figure 6 shows a drop of the sample,

at 200X magnification. For laser probe analysis, the drop had

been placed on a sheet of acrylic polymer. The many small

ripples seen in this photograph testify to the high viscosity

of the material. Figure 7 shows the same sample after it was

exposed to the laser probe. These are apparently the first

analyses of "anomalous water" for metallic elements, and the

27
Figure 6. Drop of anomalous water, approximately 1 yg

0.*

Figure J. Same sample of anomalous water after sampling

with the laser probe. Bits of polymer substrate and graphite from the electrodes are

scattered around the sample.

28
results indicate that the unusual properties are not related

to such impurities. This work is included in a recent summary

of properties and structure of the anomalous water by Lippincott, et al. [19]

Many other similar applications of analyses were made

during the past year, principally through the able work of

Mrs. M. M. Darr, Mrs. V. C. Stewart, and Mr. D. M. Bouchette.

M. Margoshes , J. L. Weber, Jr.

29
3. ELECTRON PROBE MICROANALYSIS

As in previous years, the impact of electron probe microanalysis on science and technology has further increased. In

addition, scanning electron microscopes are now commercially

available, and the use of electron beam scanning techniques

for topographic investigation is becoming commonplace in many

laboratories. Consequently, progress in both the spectroscopic and microscopic aspects of electron probe instruments

is of great practical importance

The research effort of the Spectrochemical Analysis Section, is oriented towards contributing to the progress in

areas of general interest in microprobe analysis, as well as in other fields of spectrometry. In this report, the progress

achieved during the last fiscal year will be described.

A . Quantitative Analysis

In a recent publication [20] we analyzed the sources of

error which can contribute to inaccuracy in electron probe

microanalysis. The method is based on the determination of

the ratio of x-ray intensities emitted from the specimen and

those emitted, under identical experimental conditions, from

an appropriate standard. For practical reasons it is impossible in many cases to prepare and characterize a standard of

composition matching that of the specimen area under investigation. The alternative Is to use as the standard an element

or a simple compound. Since in this event the physical events

in the target (electron deceleration, electron backscattering,

and production of secondary x-rays) differ from standard to

specimen, correction calculations must be performed to obtain

the mass-fraction of the element in question from the observed

intensity ratio.

The accuracy of this procedure is limited by imperfect

knowledge of the theory, and of physical parameters - such

as mass absorption coefficients - which are used in the

30
calculation. Furthermore, the complete calculation is tedious and, in the past, simplifications of doubtful validity

were introduced in the computation. In the last year, we

began the preparation of an extensive computer program which

includes all physical factors known at present. J. Henoc, a guest worker, has finished the writing of a FORTRAN sub-program

which permits determining the effect of fluorescent radiation

excited by the continuum. This program is based on previous

work of Henoc [21], with modifications derived from our work

on the calculation of mass absorption coefficients [22]. This

sub-program permits for the first time the inclusion of this

complex correction in automatic computer iteration programs

.

The other stages of the main program, which will include correction for fluorescence by characteristic lines, the atomic

number correction, and the absorption correction, are near

completion. This program will be issued with full documentation and commentary, in order to allow modification by prospective users. S. D. Rasberry and R. L. Myklebust have been

most helpful in giving their assistance in various aspects

of programming.

B. Standard Reference Materials

Since the calculation methods which are presently available are of a semi-empirical nature, and since adjustments

must be made for the imperfect knowledge of the physical

parameters involved, it is of utmost importance to possess

standard reference materials on which the proposed correction

procedures can be tested. Such standards must be homogeneous

on a microscopic scale, and their composition must be accurately known. It is very difficult to prepare adequate standard

reference materials for electron probe microanalysis, and, as shown in the aforementioned publication [20], lack of such

standards has in the past contributed significantly to uncertainties in quantitative electron probe microanalysis

.

31
The issuance of the NBS Standard Reference Materials

481 and 482 will greatly improve this situation. SRM 48l

is a set of gold-silver alloys, of nominally 20$, 40$, 60$,

and 80% gold. The pure metals are also included in the series

of standards which are in wire form. Homogeneity of the

alloys on a u m scale was achieved through lengthy and tedious

thermal treatment, and more than a thousand microprobe measurements were performed on each alloy, to establish whether

sufficient homogeneity for the purpose of the standard was

achieved. The chemical composition was determined independently by three laboratories, with satisfactory agreement.

The results of analyses and homogeneity tests are described

in the Certificate of Analysis which is reproduced in the

Appendix to this report.

The NBS Standard Reference Material 482 is a series of

gold-copper alloys, analogous in all aspects of preparation,

.composition, and characterization to SRM 48l.

The homogeneity measurements were performed in three

groups: on several cross-sections of the wire in order to

confirm homogeneity along the entire wire; two series of

points along orthogonal diagonals were performed on each crosssection, in order to obtain information concerning compositional

changes as a function of distance from the center of the wire;

and homogeneity on a micron scale was tested by means of the

matrix generator device described in last year's report.

The large number of data obtained in the last procedure

(100 points/matrix) required the development of computational

methods which provide statistical information (standard deviation, range, frequency distributions), as well as topographical

information. Great effort was expended in order to overcome

effects of instrumental drift. The effects of defocusing of

the x-ray spectrometers could not be entirely eliminated.

The cooperation of S. D. Rasberry, who developed the computer

programs necessary for the matrix tests, is gratefully acknowledged. 32
Our experience with the matrix generator indicates that

this method will lend itself to many useful applications, particularly in the analysis of multiphase materials . There are

intriguing possibilities of applying stereometric methods to

the results. On the other hand, the differentiation of random

patterns from topographic features poses problems of pattern

recognition which unfortunately have not been fully resolved

and put to test, due to lack of time. It is proposed that

such problems and hence the exhaustive analysis of complex

structures in solid materials, should be handled by interfacing the instrument with a small computer for data collection and evaluation. We have studied the desirable features

and limitations of such a system, and we hope to be able to

further explore these possibilities in the future.

Additional standard reference materials will be needed

for full exploration of the proposed correction procedures

for quantitative analysis. We plan to extend our studies to

systems containing elements of low atomic number. A system

which seems eminently suitable is that of binary and ternary

borides . We propose to study these compounds, which are good

electric conductors, in cooperation with the NBS Metallurgy

Division

.

Another area which requires clarification is that of

nonconductors, such as oxides and silicates. The prospect of

the recovery of lunar specimens dramatizes this situation.

At present, a host of standards is used in the analysis of

geological specimens, and it is not known if a general technique of standardization and data correction, such as used in

the analysis of alloys, will be successful with materials of

low electric and thermal conductivity. We plan to investigate

the possibility of such a procedure in cooperation with several

laboratories involved in the analysis of such materials.

Further efforts in the production of standards for ferrous alloys, and in the microscopic standardization of existing NBS standards, are probably warranted.

33
We will appreciate receiving any comments with respect to

efforts in this direction.

Once the necessary number of standard reference materials

is obtained, the proposed analytical methods and parameters

will be extensively tested with the aid of the computation program that is being developed.

The group also performed measurements on microbeads of

cation-loaded ion exchange resins (prepared elsewhere in our

Division), in order to determine their suitability as microstandards for chemical elements . Measurements of the Ca and

S K-alpha lines on Ca-loaded beads showed that the ratio of

the respective x-ray intensities is constant over a wide

range of bead sizes (Figure 8). Since the sulfur is contained

in the radicals to which the cations are attached, this is a promising method for checking uniformity of loading of the

resin beads. Measurements on Na-loaded beads gave erratic

results, probably due to the high absorption of the soft Na

K-alpha line. Further experiments will be performed to

define the range of applicability of this technique.

C . Non-diffractive Techniques of Qualitative and Semiquantitative Analysis

Since microprobe analysis is usually employed for topographic exploration on a microscale, it is frequently desirable to provide qualitative information at several points on

a specimen. The slowness of the wavelength scanning procedure

used for this purpose limits the number of points which can

be explored in a reasonable time span. The non-diffractive

detectors described in a previous report [4, p. 29] s in combination with pulse-height analysis, allow us to perform a complete qualitative analysis in three to four minutes . A

flow-proportional detector is used to cover the range from

0.2 keV to 2 keV, and a lithium-drifted silicon detector

covers the range from 1 keV to the maximum energy levels

34
180 -

160 —

140 -

120 -

SULFUR INTENSITY

Figure 8. Integral measurements of intensities of Ca

Ka and S Ka from ion exchange resin beads

loaded with Ca. Range of bead diameter:

4-30 urn.

35
emitted from the specimen, which depend upon the operating

voltage employed. Figure 9 shows examples of applying the

pair of detectors . The spectra were sorted by a range of 800

Figure 9 . Non-diffractive spectra obtained at 20 keV

and 2 x 10 - 8 a, in 4 minutes. Left: flowproportional detector. Right: Li-drifted

silicon detector.

channels of the multi-channel analyzer, and recorded on an

x-y recorder. Although the resolution and line-to-background

ratios are considerably poorer than those obtainable with

crystal spectrometers, they are sufficient to identify the

major and sub-major components (concentrations above 1%) of

the specimen. The resolution is further improved by the use

of an analog device (DuPont Curve Resolver) which enables us

to perform a rapid analog-deconvolution in a few minutes

(Figure 10 )

36
ENERGY

Figure 10

.

Spectrum of a Cu-Au alloy obtained with the

silicon detector, and reconstructed on the

Curve Resolver. Upper curve: unresolved

spectrum, background-corrected. Lower curve

peak components

.

Preliminary investigations indicate that the spectrum

recordings can be evaluated semi quantitatively , and even

close to quantitatively, particularly if correction procedures

are used on the basis of the intensity ratios derived from

the graphs. Such a procedure will frequently suffice to

indicate the nature of an inclusion or phase of unknown

composition. Some preliminary results are shown in Table 4.

By using a single-channel analyzer locked on a characteristic line in an energy spectrum, a signal usable in

matrix-techniques can be derived. This signal offers the

advantage of eliminating the defocasing effects which are

observed with crystal spectrometers when the electron beam

is deflected in the matrix procedure. Further studies in

this area are planned.

37
Table 4. Analyses of copper-gold alloys by

nondispersive detection and pulse height analysis

Legend C

k

chem

peak

int

Observed Calculated

Element chem

Copper

(K)

0.7985

• 5992

.3964

.1983

Gold

(M)

.8015

.6036

.4008

.2016

k k c c peak int peak int

0.83 0.83 0.79 0.79

.67 .65 .61 .59

.46 .43 .40 .37

.26 .22 .21 .18

.70 .71 • 78 • 79

.48 .49 • 59 .60

.30 • 30 .40 .40

.14 .15 .20 .21

mass fraction

intensity ratio

from chemical analysis

measured from peak height

measured from integrated area below peak

These measurements were performed at 20 keV, using the Lidrifted silicon detector, and evaluating the graphic record

of pulse-height analysis.

D . New Technique and Instrumentation for Target Current

Scanning .

While secondary electrons provide essentially topographic

information, the target current signal, which depends upon

the backscattering of electrons, varies with both composition

and topographic changes of the specimen surface. In microprobe

analysis, it is frequently desirable to start with a purely

topographic exploration. However, in inhomogeneous specimens

the topographic information is often obscured by large differences in atomic number. We have developed a concept of

handling the target current signal in a way that permits

separating and emphasizing the topographic aspects at will.
This may render unnecessary in many cases the installation

of secondary detectors and associated electronics. We have

constructed an amplifier (Figure 11) in which the target

current signal and its first derivative are amplified independently and recombined in any desirable proportion. If

TO

OSCILLOSCOPE

SPECIMEN BIAS t HIGH VOLTAGE

AMPLIFIER

DERIVATIVE AMPLIFIER

Figure 11. Schematic diagram of the target current

amplifier with linear and derivative component. (Detailed circuit diagram is available

on request .

)

the purely derivative signal is used for modulating the

brightness of the oscilloscope, the topographic details of

all phases appear clearly on a gray background. Passage from

one intensity level to another (when passing from low to

high atomic number or vice versa) is merely indicated by a bright or dark boundary line. By using the combined signal

we can obtain a proper balance of the change of brightness

due to atomic-number variations, and of the topographic features (Figures 12 and 13)

39
j~irx

in tl_

a

^Hr^tr-V-

^h r~h-VFigure 12. Target current signal, a. linear, b. first

derivative, and c. combined signals. Vertical intensity scales are arbitrary.

E . Further Improvements in Target Current Scanning

1. In the construction of the new target current amplifier, low-noise integrated operational amplifiers were used.

Ground-loops in the target current circuitry were carefully

eliminated. This results in a considerable reduction of noise

and hum. At the present state of development, we can obtain

-9 images of good quality at a target current of 10 A or lower.

This is very useful in the investigation of specimens which

are susceptible to damage by the electron beam.

40
Figure 13. Target current scans of titanium boride contaminated with iron. The iron is present in the bright phase of

the upper image. Upper image: linear target current, showing atomic number differences. Middle image: derivative

image, showing topography. Lower image: combination of

both signals.

41
2. In order to obtain scanning images at low magnification for a preliminary orientation, we have modified the specimen stage connections in such a way that target current scans

can be performed with the specimen at several cm below the

normal position. Thus, we obtain images of satisfactory quality at magnifications as low as 12X at 20 keV, and even lower

at lower voltages (Figure 14 ) .

Figure 14. Scanning target current image of human tooth

2 keV, 1 x 10" y A. Magnification: 4.5X

3. Replacement of electrostatic beam deflection by

electro-magnetic scanning coils has resulted in considerable

improvement in the quality of the scanning images, which have

full resolution at the edges of the scanning field. We have

also increased the stability of the power supplies for beam

formation and for the scan generator, and have improved

our beam alignment procedures, so that uniformly sharp beam

focusing is obtained in routine operation (Figure 15).

42
»a«

IBB*

b b|| J*«;' j a bo

^*-^f MB i!"3

So ioaaf ro»^

Q

Figure 15-

_o

Target current of metal grids, 20 keV, 10 A

The width of the bars of the small grid is

3.5 urn. Notice full resolution at corners.

43
The improved capabilities of our electron probe as a scanning microscope are illustrated in Figure 16. The image

shows the end of a filament of a light bulb after failure.

The admixture of derivative signal enhances the topography

of the wire surface showing recrystallization, except for

the cooler part of the filament attached to the post. The

great depth of focus of the technique can also be noted.

Figure 16. Scanning electron micrograph of a partially

recrystallized lamp filament. 20 keV,

10~°A. Mixed target signal. Magnification:

200X.

For the extensive and skillful work in developing the

new electronic equipment and in upgrading previously existing

devices we are greatly indebted to C. Fiori , of our Section,

and to Mr. L. A. Marzetta, (Measurement and Engineering Division, NBS).

F . Color Composite X-ray Scans

The advantages of a simple technique for preparing

composite color images of several x-ray scans has been discussed previously [4, p. 31]- A detailed description of our

44
method, with appropriate illustration, has appeared in the

Journal of Research, NBS [23].

This method has been further refined by including also

topographic information. The target current scan obtained

with the new amplifier is represented on the gray scale, and

up to three x-ray scans are added in the primary colors red,

green, and blue. The resulting images show clearly the topography of the specimen surface which resembles the image obtainable with a light microscope, while the colors add information

concerning the distribution of up to three elements . The

usefulness of this technique has been proven in several applications to service work. The color composites can be prepared

routinely, in a procedure similar to that described in reference

[23]. The new technique will be published shortly.

G. Applications to Analysis

We have continued to devote a large part of our effort

to service work of a diverse nature, with 21 reports issued

during this fiscal year. Some of them - such as the characterization of the standard reference materials - report the

results of extensive and complex investigations.

Considerable work was performed on binary diffusion

couples of the Ag/Ag-Cd system. The silver and cadmium concentrations were determined at approximately 200 points in a line across the diffusion zone. Adjacent points could neither

differ in composition by more than 1% nor be more than 200 ym

apart. The results were calculated and plotted using an

OMNITAB procedure.

Many of the specimens examined required only qualitative

analyses. The lithium-drifted silicon detector and thin

window flow-proportional detector enabled rapid identifications

of inclusions in steel, metal inclusions in sapphire, and of

different phases in iron-titanium-borides . Several specimens

of anomalous water were also examined by this technique and

45
all of these were shown to contain sodium as a contaminant.

Color composite photographs were used to locate various

elements in corroded aluminum specimens, iron-titanium-borides

and a steel specimen from a broken eyebar of a collapsed bridge.

Quantitative analyses were performed on many of the specimens. The different phases in alloys, such as platinumvanadium, platinum-chromium, and tungsten-rhenium, were

examined as well as a microscopic sphere of a complex phosphate-silicate. The relative x-ray intensities obtained from

these analyses were converted to concentrations using a time-shared computer. Corrections were made for pulsecoincidence losses, beam intensity drift, background, x-ray

absorption, secondary fluorescence, and atomic number effects.

In addition to the specimens already described, the

examination of other materials was performed employing one or

more of the techniques mentioned.

H. Literature Research

Work on the bibliography of electron probe microanalysis

has continued, although at a slow pace. We hope to issue an

updated bibliography during the coming fiscal year.

K. F. J. Heinrich, R. L. Myklebust

46
4. X-RAY FLUORESCENCE SPECTROMETRY

The program and instrumentation for x-ray fluorescence

spectrometry have been reviewed in prior technical notes

of this series [1, 2, 3, 4], The research on improved

methods of calibration and correction techniques for interelement interferences has yielded a successful new technique.

The use of this technique has been essential in the analysis

of high-temperature alloys and nickel-base electronic alloys

proposed for use as NBS Standard Reference Materials (SRM)

.

Stimulated by the request to analyze several thin metal

foils, we have extended our research into the area of x-ray

absorptiometry. Adding some novel twists to some very old

x-ray methods, we have been able to present an improved way

to simultaneously determine the entire composition and the

mass per unit area (px) of thin metal foils.

Approximately one-half of the effort expended in the

x-ray fluorescence project has been directed toward the analysis of chemical compositions and the determination of plating

thickness for certification of SRM's. Support to the Office

of Standard Reference Materials also has included homogeneity

testing, specimen sorting, and rapid verification of composition of labeled specimens

.

A. Research Activities

The manuscript "Applications of Digital Computers in

Spectrochemical Analysis - Fitting of Analytical Functions"

[10] has been accepted for publication by Analytical Chemistry

A manuscript is currently being prepared to present our

technique for the analysis of thin, multi-component metal

foils by x-ray absorptiometry. This method does not require

standards for analysis; however, for purposes of testing the

method, a variety of "synthetic standards" have been made by

47
stacking pure metal foils. Determinations have been made

with accuracies between 1% and 4$, relative, for foils in

the thickness range of 2 x 10 cm to 2 x 10 cm. Elements

studied include copper, nickel, iron, vanadium, and titanium.

A FORTRAN V computing program, called EDGE2, has been written

to perform the calculations necessary in these analyses.

A comparison of given composition and the composition

found by x-ray absorptiometry in the analysis of synthetic

standards is given in Table 5. The Ti-V results, example 1,

are representative of the best obtained, while those obtained

for Ni-Cu, example 2, are typical of the less accurate analyses

In the third example the possible presence of cobalt was allowed for in the EDGE2 computation for the same Ni-Cu sample,

even though Co was known to be absent. This caused a change

of approximately 1% , relative, in the estimate of the Cu

and less for the Ni

Table 5- X-ray absorptiometric analysis of

metal foil synthetic standards.

Concentration (in %)

Thickness

Example Ti V Ni Cu Co (in urn)

1. Given 68.22 31-78 22.02

Found 68.15 31.85 22.40

2. Given — — 59.3 40 .7 — 11.63

Found 61.2 38.8 11.68

3 . Given — — 59-3 40 .7 0.0 11.63

Found 61.0 39.2 -0.2 11.75

48
The FORTRAN V program IEMAT, mentioned in last year's

report [4] 3 has been completed and renamed EXCELS (Empirical

X-ray Correction Employing Least Squares). This program employs a new technique for matrix size reduction (matrix is

used here in the mathematical sense) which allows calibration

and correction for interelement interferences in cases where

the usual empirical correction approach fails due to insufficiencies in the standards. Thus far, tests of this program

have centered around the high-temperature-alloy, nickel-basealloy, and stainless steel systems. In these systems, iron,

nickel, and chromium are the principal constituents and

give rise to extreme absorption and enhancement effects . As

an example, Figure 17-A illustrates the serious calibration

problem for Ni in Ni-Fe-Cr-Co systems. Figure 17-B shows data

for the same standards and relative intensities after correction in EXCELS.

B . Applications

The application of x-ray fluorescence and the EXCELS

program to the analysis of eight high-temperature alloys, and

electronic and magnetic alloys has already been mentioned.

Further support has been given to the SRM program through

rapid preliminary analysis and homogeneity tests of incoming

material for a new set of low alloy (special steel) SRM's.

This program of quick testing of each incoming heat of steel

has been beneficial in two ways. First, the acceptability

of the material could be evaluated; and second, adjustments

to the aim composition of future heats could be specified in

order to maintain the over-all balance of the set.

The computations program for homogeneity analysis, CODEAV,

has been partially rewritten during the past year to overcome

difficulties arising from the adoption by the NBS Computation

Center of a new FORTRAN compiler for the UNIVAC 1108 computer.

At the time of this revision, substantial improvements also

49
ou '

1 I I i

I

•

70 - A

•

•

-

1 • • z

TIVE

INTENSITY

o

o

•

•

•

-

<

_l

UJ

ac

-

•

-

40

i i •

i i

i l i I

1

'

Figure 17

30 40 50 60 70

GIVEN CONCENTRATION Ni ( IN %

)

80

40 50 60 70

GIVEN CONCENTRATION Ni ( IN % )

80

Determination of Ni in Ni-Fe-Cr-Co alloy by

x-ray fluorescence. A - no correction; B - corrected by EXCELS program.

50
were made to the output format of CODEAV. One of the features

added is the automatic scaling of concentrations to be printed

so that the programmed round-off can be accomplished at the

proper level of significance.

In the determination of vanadium at the k% level in

titanium an interesting application arose for the use of a

technique for line interference correction presented earlier

[24] . The overlap of V Ka and Ti KB (the major constituent)

precluded measurement of V Ka, so V K3 was selected as the

analytical line. At first, the potential problem of V Kg

and Cr Ka line interference was underestimated, because Cr

was present only at 0.0% to 0.2%. However, an x-ray estimate

of 4.24%V compared to a value of 4.07%V by wet chemical analysis of the same specimen stimulated us to try the correction

mentioned. The corrected result for x-ray fluorescence analysis was 4.08%V.

Typical materials analyzed in the past year, other than

those already discussed, include f errosilicon, copper foils,

failed steel components, dental gold alloy, and dental silver

alloy. Approximately 600 discrete elemental determinations

were listed in 20 separate reports.

C . Contributions of NBS Personnel

Doward M. Bouchette has performed quantitative analyses

and test of homogeneity, and James L. Izlar assisted in specimen identification and label checking by x-ray methods . We

gratefully acknowledge the assistance of the late Clarence

W. Gifford in the successful completion of the homogeneity

testing of incoming f errosilicon material.

Fielding Ogburn, Jacob Smit, and Virginia Pennington

(from the Metallurgy Division) have been part-time guest

workers carrying out a project of thickness measurements on

electroplated metal coatings

.

S. D. Rasberry

51
5. SPARK SOURCE MASS SPECTROMETRY

Analysis by stable isotopic dilution with spark source

mass spectrometry has been applied to the determination of

trace impurities in high purity gold (SRM 685) and a NBS

iron standard reference material. An investigation on the

determination of impurities in various grades of acids is

now in progress and exploratory work has been performed for

the determination of trace elements in glasses using isotopic

dilution methods. A discussion of this phase of our work is

given in Section 6 of this report. Two papers were written

(see Section 7B) reporting the use of stable isotopic dilution with the spark source for the determination of trace

elements in platinum SRM 68l and for trace elements in zinc

SRM 728, 683. The trace characterization of Platinum SRM 68l

by the spark source ion samples was examined in detail.

Referring to the mass spectrometer (CEC 21-110), modifications were made to the ion source pumping system, and the

photographic plate pumping system was replaced with a larger

pump to provide faster pump down and lower base pressures.

A new development procedure for reducing plate background was

adopted and the use of a fine mesh grid over the first aperture, to reduce charge broadening of matrix lines, was investigated. Support for the Standard Reference Materials program

was provided through quantitative isotopic dilution analysis

and spark source survey analysis of materials for trace elements .

A. Instrument Modifications

1 . Source pump

The original source pumping system, using an oil diffusion

pump, was replaced two years ago with a higher speed system

[3 j p. 52] based on titanium sublimation pumping combined with

52
ion pumping. Compared to the original system lower base pressures were obtained, pump down was faster, and, most important

in terms of improved instrument performance, 10 to 20 times

lower pressures were maintained during sample sparking. A

proportional improvement was found in instrument gas background

In this system a 6-in. gate valve sealed off the ion pump;

however, the sublimation area was vented with the source each

time a sample was loaded. With extended use the start-up time

with the pump increased, although the ultimate vacuum was not

adversely affected. This problem was apparently caused by

the build up of a porous layer of titanium and titanium compounds. Because of this problem the system was redesigned

and rebuilt. The new system, shown in Figure 18, was constructed from the components of the old system.

In the new system the 6-in. gate valve (item A) prevents

the venting of the sublimation area. This positioning of the

valve also decreases the volume of the system being vented,

which in itself speeds pump-down time. Sublimation filaments

(item B) are inserted into the 6-in. diameter stainless steel

tubing leading to the 200 liter-per-second ion pump (item C)

.

The area in the tubing where titanium is sublimed is cooled

with an external water jacket. Roughing of the system is

done through a trap-valve situated behind the 90° elbow at

the top of the gate valve.

2 . New Pump for Plate Prepump Section

The original photoplate pumping system provided with the

instrument, which had an estimated conductance of 10 to 20

liters/s, has been replaced by a high speed system with a speed of approximately 400 liters/s. The pump, Figure 19,

was purchased as a complete system of assembled matching components consisting of gate valve, liquid nitrogen cold trap,

oil diffusion pump, vent valve, etc. With the original system,

overnight pumping was required to prevent the plates from

53
Figure 18 . Rebuilt source pumping system. A. - 6-in. gate valve. B. - sublimation filaments

C. - 200 1/s ion pump.

causing a significant rise in pressure when they were inserted

into the magnetic analyzer. The new system provides faster

pump-down speeds and a lower ultimate vacuum. A set of four

new plates can be pumped to pressures in the high 10 torr

range in two hours . Overnight pumping is presently providing

_7

a base pressure of 1 x 10 torr in the plate prepump section.

B. Use of 100-mesh Grids to Remove Matrix Line Broadening

We have investigated the use of a grid over the first

aperture to reduce charge broadening of major lines, as described by Franzen [25]. During the past year Ni , Mo 3 W, and

Au 100-mesh grids with about 80% open space were tested.

54
Figure 19. New pumping system for photographic plates.

Figure 20 shows the dramatic decrease in matrix line broadening brought about by the use of one such grid. Four sets

of equal exposures were made on doped Pt (NBS SRM 681),

(top tcbottom 1 x 10

-11

, 1 x 10~ 10, 1 x 10" 9

, 1 x 10

coulombs), the top exposure of each pair being made using

a 100-mesh Au grid. The grids tested so far have two drawbacks: (1) the grid material shows up in the spectrum (the

gold lines come from the grid and not the Pt) and (2) the

100-mesh grid decreases the ion beam current by a factor of

approximately three, which for all practical purposes results

55
Ill I .._

I III I

Figure 20. Exposures of Pt SRM 68l with and without a

100-mesh Au grid. The collected charge

(coulombs) is given for each set of exposures

in a 3-times poorer detection limit for elements in general.

Charge broadened lines normally cause us trouble only when

they overlap nearby elements such as in the case for Ir in

Pt . Our measurement of integrated peak-intensity areas [2]

compensates for any line width variation.

C . Plate Development

Cavard [26] has recently published a processing procedure using a bleach followed by development with an ''internal

image developer" (MK-7) . This development procedure is now

used routinely for all plates. Figures 21, 22, and 23 illustrate how the use of a grid over the first aperture and MK-7

developer can improve the detection of impurities near matrix

56
0^

1 Ir

1 1 1 193

1 1 1 196 Au

1 1. 199

Ir PtH

Figure 21. Mass spectrum of Pt SRM 68l without

grid, using Cavard's developer (MK-7)

lines. All absorption traces were made on 1 x 10 coulomb

exposures of the same platinum sample (SRM 681) . Figure 21

shows a spectrum obtained without a grid (using MK-7) — the

10 ppm Ir in the sample is just detectable but not measurable

at the 191 isotope; the spectrum in Figure 22 was made using

a grid and developed with D-19 -- both Ir isotopes are now

detected, all lines are sharper, the 194 , 5 , 6 Pt isotopes are

resolved, and lines for Au and Pt are now visible; the

spectrum in Figure 23 was obtained using a grid and MK-7

developer and shows a marked decrease in background as compared to Figure 22.

57
100-

50-

J Figure 22.

i i ill i ii ii 190 lr 193 19 6 Au 199

lr PtH Mass spectrum of Pt SRM 68l with grid,

using D-19 developer.

100i

50-

n n

IW«aJ JL

n n

, n

J

I I I I I

I I I I I 190 | r 193 196 Au 199

lr PtH

Figure 23- Mass spectrum of Pt SRM 68l with grid,

using Cavard's developer (MK-7)

58
D. Homogeneity Testing of Iron in High Purity Gold SRM 685

Spark source mass spectrometry was used to perform extensive testing for all impurities by direct sparking of the

gold SRM 685 produced this year. In addition, isotopic dilution analysis was attempted on Cu, In, Pe, and Ag in the

gold (see Section 6). Composition information on these elements plus oxygen is given on the certificate using a number

of different techniques of analysis . Homogeneity tests were

performed by direct sparking for iron but not for Cu, In, and

Ag which did not give adequate signals. Samples from four

portions of the gold wire were all compared to the same sample

of commercially pure gold (iron content unknown). A test

sample of SRM 685 and the commercial gold were exposed on

the same plate using alternate positions on the photoplate.

Alternation of exposures allows an averaging of any variation

in plate sensitivity from one side of the plate to the other.

Table 6 shows the ratio of the iron content in high purity

gold to that in the commercially pure gold for four selected

portions of the high purity gold wire. The + value is the

95% confidence interval on the limiting mean (t qc- s/Zn-) .

Table 6. Homogeneity tests for iron in gold SRM 685

Sample Ratio Fe content in Au 685/Fe in commercial gold

1-1 0.178 + 0.014

1-2 .192 + .020

13-1 .184 + .021

13-3 .180 + .013

59
There is no significant difference in the iron content of the

four portions of iron wire within these precision limitations.

When all the data from the four portions of wire are combined,

the ratio is 0.183 + 0.007 (with a coefficient of variation

of 11$ for a single determination)

E . Analysis of High Purity Materials

A number of analyses were performed on high purity metals

for the Standard Reference Materials Program. An analysis of

high purity tin SRM 7^1 is an example of this work. This tin

is to serve as a freezing point standard on the International

Practical Temperature Scale. Extensive testing of this material had been performed by measurement of its residual resistivity ratio (RRR) . Based on the variations in the RRR, two

samples were selected to represent portions that RRR predicted

to contain the most and the least amount of the electrically

active impurities. These were the samples submitted for

analysis by the spark source in order to determine which

elements were responsible for the differences in RRR values

for the material. Antimony and possibly iron were suspected

as the offending elements. The samples were run twice, the

first time with a normal first aperture in order to obtain

the maximum sensitivity for all elements and a second time

using a grid on the first aperture in order to improve the

detection of Sb . Charge broadening of the Sn matrix lines

can cause considerable trouble for Sb unless a grid is used.

The samples were compared to an NBS tin standard SRM 435.

Table 7 gives the results of this analysis.

The sulfur values found were considerably higher than

expected in these samples. An additional comparison was then

made to a tin sample run previously. Melting point and RRR

data on the older sample indicated it was less pure than the

SRM 7^1 under investigation. This "old" sample was found to

contain at least 50 times less sulfur than SRM 7^1, however

60
Table 7. Analysis of high-purity tin SRM 74l

ppm by weight

Bar A Bar B

S*

Cu

Fe

As

Sb

Pb

28 13

0.11 0.07

<.l <.l

.06 .04

<.5 <-5

• 3 .5

*The sulfur content of SRM 435 is not certified, therefore sulfur values were computed from an estimated sensitivity

whose absolute value is good only to a factor of 3 to 10.

the "old" sample did contain more Cu, Zn, Pb 3 and As. TheSSMS analysis does not contradict the freezing point and RRR

information on these samples since the sulfur content of tin

does not appreciably affect either of these parameters. The

sample is designed to serve as a freezing point reference and

not as a composition standard.

F . Survey Analysis of a Steel Sample

A series of special low-alloy steel SRM's is now in preparation. Acceptance tests are being performed by a number of

techniques in order to ensure that the aim composition has been

obtained before these materials are processed into samples

and analyzed for certification. Tables 8 and 9 give the results

of the spark source analysis of one such sample in comparison

to results from other techniques . The SSMS measurements were

referenced to NBS steel sample SRM 46l which served as a standard. The second column in Table 8 lists the concentrations

determined with the spark source, based on three line measurements each for standard and sample. The third column reports

61
Table 8. Mass spectrometric survey analysis of steel

using a standard.

ppm by wt

Spark Source Percent

Element vs. 461 Other Methods

<1

Difference

Pb 0.09

W 270 150 45$

Sn 130 100 23

Ag 3 4 33*

Mo 2,400 2 ,000 17

Nb 200 200

As 370 200 46

Cu 570 450 21

Ni 23,000 20 ,000 13

Co 360 240 33

Mn 7,200 6 ,600 8

Cr 6,900 7 ,100 3

V 74 120 62

Ti 66 190 120*

S 390 130 67*

23 12 48*

C 3,200 3 ,700 16

Average 24

*Since determinations for these elements listed on the

certificate were not certified, these differences were omitted

in computing the average

the average values by the other methods of analysis, and the

last column the percentage difference between the spark

source results and those of the other techniques. The average

difference- is shown to be 24%.

62
Table 9 lists the spark source results for elements

which were not certified in SRM 461 and therefore the values

are based on estimated sensitivity factors. Common practice

is to claim that the accuracy of the estimation method is

Table 9. Mass spectrometric survey analysis of steel

using estimated sensitivity factors.

Spark Source

Element vs. Matrix Sens. Other Methods Error Factor

Bi 2.9 6 2.1

La 19 8 2.4

Te 40 4 10

Zr 70 100 1.4

Zn 5-0 7 1.4

Ca 9.2 1 9.2

Mg 47 1.5 31

Average 8.2

no better than a factor of 3 to 10. The last column lists

an "error factor", a ratio of the results of spark source

to other techniques . The average error factor for this set

of elements is 8.2. The estimation is based on all elements

having equal atomic sensitivity and then correcting for

changes in plate sensitivity with mass. As is the case here,

the estimation method usually gives high results for the

alkalies and alkaline earths

P. J. Paulsen, C. W. Mueller

63
G . Trace Characterization of Spark Source Ion Samples of

SRM Platinum 68l

1

Introduction

The precision and accuracy with which materials (solids)

can be trace characterized by Spark Source Mass Spectrometry

continue to be a problem of concern to all using this analytical technique. In the annual report last year [4] methods

for measuring the homogeneity of ion sensitive plates were

described and results for Q-2 plates were presented. In

that work advantage was taken of the wide spread in relative

abundances of the isotopes of platinum. Using SRM platinum

681, replicate exposures of 5 x 10 coulombs to the monitor

were made. These adequately recorded the platinum 192 isotope,

the concentration of which is about 7800 ppma.

In the experiments reported herein, replicate exposures

-9 of 5 x 10 coulombs are made. This adequately records the

platinum 190 isotope whose concentration is 123 ppma. It also

records most of the trace elements certified in SRM Pt 68l

that are present in the 1 to 100 ppma range. Data from such

replicate exposures characterize the trace ions in the recorded

ion samples and yield information on the precision achieved

under the prevailing experimental conditions

2

Results

Data for platinum and for trace elements copper, lead,

and palladium are presented in Figure 24. The integrated

value of the ion beam profile of the mass line in question is

plotted on the vertical axis and the succession of 21 replicate

exposures is delineated on the horizontal axis. The above

integrated values are normalized by dividing by the average

of the specific trace values from the 21 exposures recorded.

During the six exposures indicated by triangular points, the

64
INTENSITY OF

ION BEAM/EXPOSURE

PALLADIUM

2 4 6 8 10 12 14 16 18 20 22

REPLICATE EXPOSURE NO.

Figure 24. Normalized ion beam measurements of trace

elements in spark source ion sample Pt SRM.

*. - satisfactory run. • - spark stopped,

restarted.

spark stopped and was restarted by decreasing the electrode

separation. For all three trace elements shown in Figure 24

and for the seven trace elements measured but not shown here,

the integrated beam value for exposure 20 was significantly

greater than for exposures 19 and 21. For the other exposures,

during which the spark stopped, smaller differences between

this integrated beam value and its adjacent values were observed. A substantial number of them gave lower beam values.

65
Nevertheless , for these six exposures extensive changes

in one spark parameter were occurring. Due to electrode

consumption, the separation increases to the point where it

is too large to sustain the spark. When the spark is restarted, this gap is substantially less than the maximum at

which the spark is sustained. Because of these major gap

changes, all data for these six exposures were deleted in

compiling results presented in Tables 10 and 11.

Table 10 presents relative standard deviations for the

integrated beam values of each of the 10 trace elements and

platinum. Corresponding to the elements listed in the first

column, the second column lists the relative standard deviation for the data remaining after the deletions indicated

above. Note that it varies from 15.7$ for phosphorus to 6.8%

for iron and rhodium.

The ratio of the reading for a particular trace element

to the corresponding value for lead at each exposure was then

calculated. The relative standard deviation of these ratios

is given in the third column. The relative standard deviations of the various trace element/lead ratios to be expected, if the trace element readings varied independently of

one another, are given in the fourth column of Table 10.

The difference between the observed values in column 3 and

those in column 4, expected on the basis of independent fluctuations, clearly shows that the integrated beam values for

the trace elements do not in general fluctuate independently.

The data of Table 10 also show that the fluctuations in

the integrated beam values of the trace elements are greater -

in many cases substantially greater — than those due to

instrumental factors alone as revealed by the 4.6% value for

the major component platinum.

Two alternative interpretations of the data of Table 10

are

a. The number of trace element ions in the recorded

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67
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b. This number may fluctuate in successive exposures

because the platinum sample itself is inhomogeneous

In any event, it seems clear from Table 10 that the trace

elements in this platinum do not fluctuate independently.

Table 11 presents the trace element composition of ion

samples from SRM platinum 68l. Results are given from two

different plates, one of which (plate 105D) furnished the

1/2 data of Figure 24 and Table 10. The ts/n values give the

95% confidence interval. The concentrations listed are the

ratio of the integrated ion beam of the trace element to that

of the platinum 190 ion corrected for isotope effects, mass

effect, and ionization pattern. The NBS certified values for

a number of the trace elements are included in Table 11. Relative Sensitivity Factors (the average of the two SSMS values

divided by the NBS certified value) are also listed.

3 . Pis cussion

a. In these replicate tests, the relative standard

deviation for a trace element in the recorded ion samples

is greater in general than for the major component platinum.

b. This probably indicates that there are fluctuations (1) in the relative production of trace element ions in

the spark source and/or (2) in the transmission of these ions

from this source to the detector.

c. The fluctuations in the concentrations of the

several trace elements in the ion sample recorded are not

independent of each other.

d. An alternative interpretation of Item a in terms

of sample inhomogeneity must not be overlooked. On this basis

item c would indicate that the trace elements in the sample

tend to have the same topographical distribution.

Further study will be made to ascertain the causes of

the observed variability.

A. J. Ahearn

68
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69
6 . PRECONCENTRATION TECHNIQUES

A. High Purity Metals

In last year's annual report [4], we outlined stable

isotope dilution - spark source mass spectrometric (ID-SSMS)

methods developed for simultaneously determining several

trace elements in zinc and platinum. The platinum procedure

has been published in the June 1969 issue of Analytical

Chemistry; the zinc method is scheduled for publication in

Volume 24B of Spectrochimica Acta. In the zinc procedure,

the isotopically altered trace elements were electrodeposited

onto gold wires from the zinc solution in one operation.

The gold wires were then sparked in the spectrograph. In

the platinum method, the spiked trace elements were separated

from the platinum solution by ion-exchange and then were

electrodeposited onto gold wires for sparking. The electrodeposition step, which is common to both methods, provides

the trace elements in an adherent form relatively free of

anions. In the platinum method, the analytes are also relatively free of hydrocarbons from the ion exchange resin.

The presence of these species during sparking can complicate

the spectrum. Moreover, because electrodeposition requires

fewer manipulations than the alternative of evaporating a solution of the analytes onto gold wires, it Is less subject

to contamination.

To determine Ag, Cu, Pe, and In in a high purity gold

material, subsequently issued by NBS as Standard Reference

Material 685, an ID-SSMS method was developed. In the procedure, aqua regia and known amounts of the enriched isotopes

were added to a weighed sample. The resulting solution was

then evaporated to dryness to remove the excess acid. Water

was added to the residue and the solution passed through a

cation exchange column. After elution from the column, the

acid eluate containing the spiked analytes was neutralized

with ammonia and the trace elements were electrodeposited onto

70
gold wires for sparking in the spectrograph. The concentrations determined ranged from 0.2 ppm for Fe to 0.004 ppm for

In. Indium, at this concentration of 4 ppb , was at the

threshold of detectability by a direct SSMS examination of

the gold wire material, SRM 685W. The preconcentration step

of the ID-SSMS procedure provided sufficient intensity for

the isotope mass lines to yield these individual results:

0.0040, 0.0039:, 0.0036 ppm In. For In and Ag, the method

blanks were an order of magnitude lower than the concentrations

being determined. The spiked blanks were run at the same time

and under the same environmental conditions as the samples.

For the more common elements, Cu and Fe , the blanks were

higher. This was to be expected considering the relatively

large number of manipulations that the method required. Fe

,

corrected for blank, was found to be 0.20 ppm compared to the

NBS Certificate value of 0.3 ppm, which includes polarographic and spectrophotometric results . For Cu, a value of

<_ 0.1 ppm was reported, because of the magnitude and large

variations in the blank. The certificate value is 0.1 ppm.

B . Ingot Iron and Steels

In 1955 3 a set of ingot iron and steels was prepared

primarily to serve as standards for spectrochemical analysis.

Designated as NBS Il6l-ll68, their compositions Include trace

elements appearing in ferrous-base materials either as tramp

elements or as additions . Many of these elements were not

certified because of their seemingly innocuous effect on the

properties of steel. Since then some of these elements have

been found to be significant and there has been an increasing

interest in accurate determinations. A renewal set of iron

and steel SRM's is in preparation and reliable results for

these trace elements are desirable.

71
Although the ID-SSMS methods that have been developed

have been applied only for trace element determinations in

high-purity metals, the methods have a broader scope. Consequently an ID-SSMS method has been applied to the simultaneous determination of Ag, Cu, Mo, and Ni in ingot iron

ranging from 0.0005$ for Ag to 0.026$ for Ni . Moreover, in

the analysis of NBS II65, a relatively constant ratio of the

mass lines produced by the Co nuclide and a Ni isotope has

been observed because of the chemical similarity of the two

elements. This enables the determination of Co, which is

mononuclidic in nature, at the same time. In the analytical

procedure developed, known amounts of enriched isotope solutions are added to the samples being dissolved. The iron is

extracted and the trace elements are electrodeposited onto

gold wires for sparking. In addition to the altered isotope

ratios, the Co to Ni isotope ratios are also determined.

The procedure will be detailed in a manuscript being prepared for publication.

C. Simulated Lunar Glasses

These proposed standard reference materials contain

additions of 0.02, 1, 50 and 500 ppm of 61 elements in a soda

lime glass. This base material was selected because it dissolves a great number of elements over a wide concentration

range. It is anticipated that reliable determinations made

on these samples, thus providing certified values, would

assist analysts to detect possible systematic errors in

their analytical procedures

Very preliminary experimentation on the 50-ppm addition

SRM indicates that at least ten elements are determinable

simultaneously using one separation scheme. Particularly

for the 1 and 0.02 ppm SRM's, an experimental design is being

investigated to enable all operations of sample dissolution,

72
enriched isotope spiking, and separation of the equilibrated

trace elements to be performed in the same vessel.

D. Ultra-Pure Liquid Reagents

Reagent purity often limits the minimum concentration of

a trace element that can be determined by an analytical method

The acids employed are particularly important because of the

relatively large volumes required for sample dissolution.

Before undertaking a complex analytical problem, such as the

previously described method for determining ultra-trace

impurities in high-purity gold, it would obviously be advantageous to select the purest acid with respect to the trace

elements of interest. An ID-SSMS method for analyzing ultrapure reagents is being investigated. Enriched isotope solutions of approximately ten different elements are added to

100-ml samples, and 20-ml aliquots are evaporated to about

200 pi in a clean environment. The liquid residue is pipetted

onto gold wires and evaporated to dryness. The wires are

sparked in the mass spectrograph. A qualitative examination

of the spectra often suffices for selection of the acid that

is to be used in the analytical procedure. However, by

measuring the appropriate isotope ratios, a precise determination of impurities can be made.

R. Alvarez, P. J. Paulsen, C. W. Mueller

73
7. PERSONNEL AND ACTIVITIES

A . Personnel Listing

Spectrochemical Analysis Section

Bourdon F. Scribner, Section Chief

Arthur J. Ahearn, Research Physicist

Karen L. Loraski, Section Secretary

Brenda J. Brown (Summer Assistant, 1968)

Group I . Optical Spectrometry

Marvin Margoshes, Chemist (Resigned, June 1969)

Joseph L. Weber, Jr., Physicist

Martha M. Darr, Chemist

Virginia C. Stewart, Chemist

Doward M. Bouchette, Physical Science Technician

Kimberly V. Koppe (Summer Assistant, 1969)

Group II. X-Ray Spectrometry and Electron Probe

Microanalysis

Kurt F. J. Heinrich, Chemist

Donald L. Vieth, Physical Metallurgist (On extended

leave)

Robert L. Myklebust, Chemist

Stanley D. Rasberry, Physicist

Jean R. Henoc, Physicist (Guest Worker)

Barry L. Hammond, Chemist (Research Associate)

Charles E. Fiori, Electronic Technician

Marcia D. Mayfield (Summer Assistant, 1968)

Jerome S. McKay, Jr. (Temporary)

Jeremy R. Winick (Summer Assistant, 1969)

Katherine C. Burress (Summer Assistant, 1969)

Part Time Guest Workers

Harvey Yakowitz, NBS Metallurgy Division

Fielding Ogburn, NBS Metallurgy Division

Group III. Spark Source Mass Spectrometry

Paul J. Paulsen, Chemist

Charles W. Mueller, Chemist

Daniel E. Kelleher (Transferred, Sept. 1968)

Larry L. Shank (Summer Assistant, 19 69)

Group IV. Enrichment Techniques

Robert Alvarez, Chemist

74
B

1

Section: Summary of Activities

Sept. 1968.

Publications

Yakowitz, H . , and Heinrich, K. F. J.

Inclusion Identification by Means of Electron Probe

Microanalysis, Metallography 1, 55-79 (1968).

Scribner, B. F. (Editor)

Spectrochemical Analysis Section: Summary 1 July 1967 to June 1968, NBS Tech. Note 452,

Heinrich, K. F. J. (Editor)

Quantitative Electron Probe Microanalysis, NBS Spec.

Publ. 298 Oct. 1968, 299 PP.

Heinrich, K. F. J., and Yakowitz, H.

Quantitative Electron Probe Microanalysis: Fluorescence

Correction Uncertainty, Mikrochim. Acta 1968 , 905-916.

Heinrich, K. F. J.

Common Sources of Error in Electron Probe Microanalysis,

Advances in X-ray Analysis, Vol. 11, 40-55, (1968),

Plenum Press, N. Y.

Veillon, C., and Margoshes , M.

An Evaluation of the Induction-coupled, Radio-frequency

Plasma Torch for Atomic Emission and Atomic Absorption

Spectrometry, Spectrochim. Acta, 2_3B, 503-12 (1968).

Veillon, C, and Margoshes, M.

A Pneumatic Solution Nebulization System Producing

Dry Sample Vapor for Atomic Spectroscopy, Spectrochim.

Acta, 23B, 553-5 (1968).

Heinrich, K. F. J.

Electron Probe Microanalysis

troscopy 22, 395-403 (1968).

A Review, Appl . Spec10

Ampian, S . G .

,

Intermediate

Na„ZrSiCy, J

2 5

and Myklebust, R. L.

Phases in the Solid State Syntnesis of

, Am. Ceramic Soc. 51, 605-7 (1968).

Ah earn, A. J.

Homogeneity of Ion Sensitive Emulsions and Precision

of Ion Beam Measurements in Spark Source Mass Spectrometry (A Summary), Sixteenth Annual Conference on

Mass Spectrometry and Allied Topics, Pittsburgh, Pa.,

May 1968, pp. 271-3.

75
11. Ahearn, A. J., and Paulsen, P. J.

Workshop on Mass Spectrometric Analysis of Solids,

Anal. Chem. 4l, Feb., 79A-81A (1969).

12. Alvarez, R., Paulsen, P. J., and Kelleher, D. E.

Simultaneous Determination of Trace Elements in Platinum

by Isotope Dilution and Spark Source Mass Spectrometry,

Anal. Chem. 4l_, No. 7, pp. 955-8 (1969).

13. Yakowitz, H., and Heinrich, K. F. J.

Color Representation of Electron Microprobe Area-Scan

Images by a Color Separation Process, J. Res. NBS

,

73A , No. 2, pp. 113-23 (1969).

14. Heinrich, K. F. J.

Review: 3rd National Conference on Electron Microprobe Analysis and the 1st Annual Meeting of the

Electron Probe Analysis Society of America, Chicago,

31 July - 2 August 1968, Appl. Optics 8, No. 4, 862-3

(1969)

15. Heinrich, K. F. J.

Advances in the Metallurgical Applications of Electron

Probe Microanalysis, Proceedings V International Congress on X-ray Optics and Microanalysis, Tuebingen,

West Germany, Sept. 1968 (In press).

16. Heinrich, K. F. J., and Yakowitz, H.

Propagation of Errors In Correction Models for Quantitative Electron Probe Microanalysis, Ibid. (In press).

17. Margoshes, M.

Linearization of Characteristic Curves in Photographic

Photometry, Appl. Optics (In press).

18. Margoshes, M., and Rasberry, S. D.

Application of Digital Computers in Spectrochemical

Analysis. 1. Computational Methods in Photographic

Microphotometry , Spectrochim. Acta, Part B, (In press).

19. Paulsen, P. J., Alvarez, R. , and Kelleher, D. E.

Determination of Trace Elements In Zinc by Isotope

Dilution Spark Source Mass Spectrometry, Spectrochim.

Acta, Part B (In press).

20. Margoshes, M., and Rasberry, S. D.

Fitting of Analytical Functions with Digital Computers

in Spectrochemical Analysis, Anal. Chem. (In press).

76
21. Margoshes, M.

The Future of Data Acquisition and Computation in Spectrochemical Analysis, Spectrochim. Acta, Part B (In

press )

.

C. Talks Given

1. Heinrich, K. F. J., "Propagation of Errors in Correction

Models for Quantitative Electron Probe Microanalysis,"

5th International Conference on X-ray Optics and

Microanalysis, Tttbingen, Germany, September 10, 1968.

2. Heinrich, K. F. J., "Metallurgical Applications of

Electron Probe Microanalysis," 5th International

Conference on X-ray Optics and Microanalysis, Tubingen,

Germany, September 12, 1968.

3. Margoshes, M., "Laser Probe Spectrochemical Analysis,"

Scientific Apparatus Manufacturers Association, NBS

,

Gaithersburg, Md. } September 17, 1968.

k. Margoshes, M., "Use of the Computer Where Flexibility

is Needed," Eastern Analytical Symposium, New York,

N. Y.j November 14 , 1968.

5. Heinrich, K. F. J., "Energy Dispersion with Electron

Excitation," Eastern Analytical Symposium, New York,

N. Y., November 15, 1968.

6. Paulsen, P. J., "Isotopic Dilution Analysis with the

Spark Source Mass Spectrograph," Eastern Analytical

Symposium, New York, N. Y., November 15, 1968.

7. Heinrich, K. F. J., "Data Collection and Evaluation in

Microprobe Analysis," Midwest Probe Users' Group,

St. Louis, Mo., December 5, 1968.

8. Scribner, B. F., "Modern Developments in Spectrometric

Analysis," Clarion State College, Clarion, Penn.,

December 11, 1968.

9. Alvarez, R., "Simultaneous Trace Element Determinations

by Isotope Dilution Techniques and Spark Source Mass

Spectrometry," Society for Applied Spectroscopy,

Clarksville, Md., January 28, 1969

.

10. Rasberry, Stanley D., "Automatic Collecting and Processing of Microprobe Data," Society for Applied Spectroscopy, Clarksville, Md., January 28, 1969.

77
11. Ahearn, A. J., "Trace Characterization of Materials by

Spark Source Mass Spectrometry," 4th Middle Atlantic

Regional Meeting of the American Chemical Society,

Washington, D. C, February 14, 1969.

12. Alvarez, R., "Multi-element Trace Determinations by

Isotope Dilution Techniques," 4th Middle Atlantic Regional Meeting of the American Chemical Society,

Washington, D. C, February 14, 1969.

13. Heinrich, K. F. J., "New Instrumentation for Electron

Microprobe Analysis and Scanning Electron Microscopy,"

American Institute of Mining, Metallurgical and

Petroleum Engineers, Washington, D. C., February 17,

1969.

14. Ahearn, A. J., "The Role of New Instruments for Mass

Analysis in Metallurgy," American Institute of Mining,

Metallurgical and Petroleum Engineers, Washington,

D. C, February 17, 19 69.

15. Rasberry, Stanley D., "Analysis of Thin Metal Foils by

X-ray Absorptiometry," The Pittsburgh Conference on

Analytical Chemistry and Applied Spectroscopy, Cleveland, Ohio, March 3, 1969-

16. Ahearn, A. J., "Trace Characterization of Solids by

Spark Source Mass Spectrometry," Pittsburgh Conference

on Analytical Chemistry and Applied Spectroscopy,

Cleveland, Ohio, March 4, 1969.

17. Alvarez, R., "Simultaneous Trace Element Determinations

in a New NBS High-Purity Gold (SRM 685) by Isotope

Dilution, Spark Source Mass Spectrometry," Pittsburgh

Conference on Analytical Chemistry and Applied Spectroscopy, Cleveland, Ohio, March 4, 1969

18. Margoshes, M. , "A Spectrograph/Spectrometer System for

Use with the Laser Probe," Pittsburgh Conference on

Analytical Chemistry and Applied Spectroscopy, Cleveland, Ohio, March 4, 1969

19. Margoshes, M. , "Approach to Automation in Spectrochemical

Measurement and Computation," Pittsburgh Conference on

Analytical Chemistry and Applied Spectroscopy, Cleveland, Ohio, March 5, 1969-

20. Rasberry, S. D., "Computers in Spectroscopy: Introduction to Computer Usage," Society for Applied Spectroscopy, Clarksville, Md . , March 11, 1969

78
21. Margoshes, M. 3 "Computer Applications - Emission Spectrochemical Analysis," Professional Development Program, Society for Applied Spectroscopy, Clarksville,

Md., May 20, 1969-

22. Heinrich, K. F. J., "Measurement Techniques Used and

Problems Encountered in Certification of NBS Standard

Reference Materials — Microprobe," Symposium on an

International Standard Reference Materials Program —

Workshop, NBS, Gaithersburg, Md., May 22, 1969 .

23. Weber, J. L., Jr., "Measurement Techniques Used and

Problems Encountered in Certification of NBS Standard

Reference Materials -- Complex Steels," Symposium on an

International Standard Reference Materials Program -- Workshop, NBS, Gaithersburg, Md., May 22, 1969

.

24. Heinrich, K. F. J., "Electron and Ion Microprobe Analysis,"

10th Symposium on Electron, Ion, and Laser Beam Technology, NBS, Gaithersburg, Md., May 23, 1969-

25. Scribner, B. F., "New Types of Spectrometric Standard

Reference Materials and Their Accurate Characterization," XV Colloquium Spectroscopicum Internationale,

Madrid, Spain, May 27, 1969

.

26. Alvarez, R. , "The Determination of Trace Elements, Simultaneously and with High Precision by Isotope Dilution

and Spark Source Mass Spectrometry," XV Colloquium

Spectroscopicum Internationale, Madrid, Spain, May 29,

1969.

27. Margoshes, M., "Two Programs for Fitting Spectrochemical

Analytical Curves on Digital Computers, XV Colloquium

Spectroscopicum Internationale, Madrid, Spain, May 30,

1969.

28. Margoshes, M., "Use of Computers in Spectrochemical

Analysis," Chemistry Department, Imperial College of

Science and Technology, London, England, June 6, 1969

.

29. Heinrich, K. F. J., "Electron Probe Microanalysis,"

American Chemical Society, Analytical Chemistry Symposium, Athens, Ga., June 12, 19 69.

79
D. Committee Activities

F. Scribner

Member, ASTM Committee E-2 on Emission Spectroscopy

Member, ASTM Committee E-13 on Absorption Spectroscopy

Chairman, Student Awards Committee, Eastern Analytical

Symposium, 1969

Delegate to Governing Board, EAS , 1968

Titular member, Commission on Spectrochemical and Other

Optical Methods of Analysis, International Union of

Pure and Applied Chemistry

Member, Advisory Board, Spectrochimica Acta, Atomic

Section

Member, International Advisory Board, XV Colloquium

Spectroscopicum Internationale, Madrid, 1969

Chairman, Nominating Committee, Society for Applied

Spectroscopy, 1968

Member, Committee on Honorary Members, SAS, 1969

Past-Chairman, Baltimore-Washington Section, SAS, 1968-69

Member, Nominating Committee, National Capital Section,

Optical Society of America, 1969

Member, Analytical Standards Committee, NBS Analytical

Chemistry Division

Member, Analytical Services Committee, NBS Analytical

Chemistry Division

M. Margoshes

Editor, Spectrochimica Acta, Atomic Section

Member, Publications Committee, Society for Applied

Spectroscopy, 1968

Member, Professional Development Committee

Baltimore-Washington Section, SAS, 1968-69

K. F. J. Heinrich

President, Electron Probe Analysis Society of America,

1969

Assistant Editor, Mikrochimica Acta

Secretary, Organizing Committee, 10th Symposium on

Electron, Ion, and Laser Beam Technology, NBS,

Gaithersburg, Md. 1969

A. J. Ahearn

Chairman, Subcommittee VII, ASTM Committee E-14 on

Mass Spectrometry and Allied Subjects

Co-Chairman, Workshop on Spark Source Mass Spectrometry,

NBS, Nov. 1968

80
P. J. Paulsen

Member, Subcommittee VII, ASTM Committee E-14 on Mass

Spectrometry and Allied Subjects

Co-Chairman, Workshop on Spark Source Mass Spectrometry,

NBS, Nov. 1968

R. Alvarez

Member, ASTM Committee E-2 on Emission Spectroscopy

J. L. Weber, Jr.

Member, ASTM Committee E-2 on Emission Spectroscopy,

Subcommittees IV, VII, and IX

Member, ASTM Committee B-7 on Light Metals and Alloys,

Cast and Wrought

Secretary, Baltimore-Washington Section, SAS , 1969-70

S. D. Rasberry

Member, Laser Task Group, ASTM Committee E-2

Technical Coordinator, Spring Session, SAS, BaltimoreWashington Section, Professional Development Program

for Scientists: Computers in Spectroscopy

81
8 . ACKNOWLEDGMENTS

The operations of our laboratory have been assisted by

persons in other groups and by the supporting services of

NBS including library, plant, and shops; we gratefully

acknowledge our dependence on these services. Some individuals who were especially helpful are named below.

Dr. Robert J. Arms and Clayton L. Albright of the Computer

Services Division have provided very useful advice on computer

programming problems.

Mr. Louis Marzetta and others of the Electronic Instrumentation group contributed valued assistance on electronics

problems

Mr. Harvey Yakowitz of the Metallurgy Division continued

his close collaboration with our microprobe group which has

resulted in several papers co-authored with members of our

group

Dr. Jean Henoc, guest worker, and Mr. Barry Hammond,

research associate, contributed much to the efforts in quantitative electron probe microanalysis. These cooperative

programs with outside agencies supporting good research men

have proved highly successful in our laboratory.

Mrs. Rosemary Maddock and her group have continued most

helpful assistance to us in the area of publications including

the planning and preparation of illustrations and slides.

Miss Karen Loraski, our Section Secretary, has provided

invaluable assistance to members of the Section in a variety

of activities, including typing of complex manuscripts and

reports .

82
9. LIST OF REFERENCES

[1] Scribner, B. F., ed., "Spectrochemical Analysis:

Optical Spectrometry , X-Ray Fluorescence Spectrometry , and Electron Probe Microanalysis Techniques,

July 1964 to June 1965," NBS Technical Note 272,

Oct., 1965.

[2] Scribner, B. F., ed., "Activities of the NBS Spectrochemical Analysis Section, July 1965 through June

1966," NBS Technical Note 401, Sept., 1966 .

[3] Scribner, B. F., ed., "Activities of the NBS Spectrochemical Analysis Section, July 1966 through June

1967," NBS Technical Note 422, Jan. 1968

[4] Scribner, B. F., ed . , "Spectrochemical Analysis Section:

Summary of Activities July 1967 to June 1968," NBS

Technical Note 452, Sept., 1968.

[5] Svoboda, V., Appl. Spectry . 20_, 219 (1966).

[6] Piepmeier, E. H., and Malmstadt, H. V., Anal. Chem. 4l_,

700 (1969)

[7] Nachtrieb , N. H., "Principles and Practice of Spectrochemical Analysis," McGraw-Hill, New York, 1950,

p. 272.

[8] Rasberry, S. D., Margoshes , M., and Scribner, B. F.,

"Applications of a Time-Sharing Computer in a Spectrochemistry Laboratory: Optical Emission and

X-ray Fluorescence," NBS Technical Note 407, Feb.,

1968.

[9] Margoshes, M. , and Rasberry, S. D., Spectrochim. Acta

24B , in press

[10]' Margoshes, M., and Rasberry, S. D., Ana± . Chem., in

press

[11] LeRoy, J. R., Annu. ISA (Instrum. Soc. Amer.) Conf.

Proc. 21 (3), 6.1-1-66 9 pp. (1966).

[12] Margoshes, M., "Approach to Automation in Spectrochemical

Measurement and Computation," Paper No. 172, Pittsburgh Conference on Analytical Chemistry and Applied

Spectroscopy, Cleveland, Ohio, March 5> 1969-
[13] Gloersen, P., J. Opt. Soc. Amer . 4_8, 712 (1958).

[14] Anderson, J. E., Rev. Sci. Instrum. 37_, 12 l4 (1966).

[15] Galan, L. de, Anal. Chim. Acta 34_, 2 (1966).

[16] ftslund, N. R. D., and Cronhjort, B. T., IBM F. Res.

Devel. 8, 160 (1964)

[17] Eick, J. D.j Caul, H. J., Smith, D. L. 3 and Rasberry,

S. D., Appl. Spectry. 21, 324 (1967).

[18] Deragin, B. V., Churaev, N. V., Fedyakin, N. N., Talaev,

M. V., and Ershova, I. G., Izv. Akad. Nauk SSSR,

Sep. Khim. 2178 (1967); English translation, Bull.

Acad. Sci. USSR, Div. Chem. Sci. 2095 (1967).

[19] Lippincott, E. R., Stromberg, R. R., Grant, W. H., and

Cessac, G. L., Science 164, 1482-7 (1969).

[20] Heinrich, K. F. J., Advances in X-ray Analysis, Vol. 11,

1968, p. 40, Plenum Press, N. Y.

[21] Henoc, J., Quantitative Electron Probe Microanalysis , NBS Spec. Publ. 298, p. 197 (1968).

[22] Heinrich, K. F. J., The Electron Microprobe , J. Wiley,

N. Y. , 19 66, p. 296.

[23] Yakowitz, H., and Heinrich, K. F. J., J. Res. NBS 73A,

No. 2, 113-23 (1969).

[24] Rasberry, S. D. , Caul, H. J., and Yezer, A., Spectrochim

Acta 2_3B, No. 5, 345-51 (1968).

[25] Franzen, J., and Schuy, K. D., Z. Anal. Chem. 222 , 295

(1967).

[26] Cavard, A., "Improvements in Ion Detection by Photographic Development Process," in Advances in Mass

S pectrometry Vol. 4 , London, Institute of Petroleum,

19 68, pp. 419-20.

84
u. S. DepartWnf of Commerce

KTiSmi

APPENDIX A

C. K.Smith

"tSep^etar^

National f5uf A. V,

cnj Standards

rector Certificate of ^nalpgte

Standard Reference Material 682

High—Purity Zinc1

This standard of very high-purity zinc metal is issued as a special research material to further both chemical and physical methods of characterization. Two other zinc metal

standards of a lesser degree of purity are also available: SRM 683 in the form of semicircular

bar segments and SRM 728 in shot form. The same starting material was used for all three

standards; however, this high-purity zinc material was further purified by vapor distillation,

zone-refining, and degasification.

Element 2

Copper

Cadmium

Iron Silver

Tin

Recommended

Value

(ppm by wt.)

0.042

(0.1)

5

(0.1)

(0.02)

(0.02)

Range of Values

Reported 3 (ppm by wt.)

(0.038 - 0.050)

Method of

Analysis 4

AAS, SPPH

SSMS-ID

SSMS-ID

SSMS-ID

SSMS-ID

The material is In the form of semicircular bar segments about 2 1/4 inches in diamete^ 1 inch deep at mid-diameter, and 3/4 inch long.

Spark-source mass spectrographic results inhomogeneity for the elements Bi, techniques and polarography using

resisitivity ratio measuremen

electrically active elements s/ich inconsistent with any No other elei spectrographic

element. Slight

level.

2. In the course of analyses by spark-source mass spectroscopy and by neutron

being present. These are listed below with an estimated conservative i parts per million by weight: Al <0.03 Cr <0.06 B < .01 Ca < .2 F <

Be < .03 CI < .5 K j£Xl\\ \V W < .03

ents were detected as

; all values are given in

06 O <0.5

2 Si < .5

1 Ti < .2

>mV32inple\£Jzes of 20 to 50 mg showed definite evidence of gross

This wa« partially confirmed for Pb as determined by isotopic dilution

lies, Vbiclrtjoth showed Pb heterogeneity to a much lesser degree. Residual pout iV to 15 g samples also indicated some limited variability for the id Tl; however, the minimum ratio of 33,000 (R-273K/R4K) would be

lements exceeding 0.1 ppm (by weight) on a 10-15 g sample size.

with most elements having an estimated limit of detection by spark source mass

0.05 ppm. Direct interference by Zn on S precluded any reasonable estimate for this occurred for Ba, Cs, Hg, and Pt, but each was not detected at about the 0.2 to 1 ppm

By neutron activation analysis4, the elements As, Ga, Sc, and W were not detected at about the 0.005 ppm level and Au

was not detected at about the 0.02 ppb level.

3. The range of values reported is that of the eight individual determinations made by the two analytical methods used. The recommended value is based on considerations of the estimated systematic bias of each of the methods. Six of the

eight values reported were in the range from 0.040 to 0.044 ppm.

4. AAS — Atomic Absorption Spectrometry (T. C. Rains) SPPH - Spectrophotometry (R. W. Burke) SSMS-ID - Spark-Source Mass Spectrometry - Isotope Dilution (R. Alvarez and P. Paulsen) NAA — Neutron Activation Analysis (B. A. Thompson and D. A. Becker)

5. Values in parentheses are not certified for accuracy since only one method of analysis was used, but are provided for

additional information on the composition.

Washington, D. C. 20234

July 9, 1968

W. Wayne Meinke, Chief

Office of Standard Reference Materials

(over) 85
This standard is intended as research material which should be of interest to the chemist,

physicist, and materials engineer. Its very high purity makes it ideal as a starting material for

the preparation of phosphors and as a solid-state matrix, where a knowledge of the purity of

the material is important. It will also meet the urgent needs of analysts working at trace

level concentrations of elements in High -purity zinc. The material should serve for the

development of new or improved methods and techniques in extending the sensitivity of

defection in the determination of trace constituents by chemical, optical emission and spark source mass spectrochemical, activation, and resistivity methods. The material was prepared

by Cominco American, Inc. from a special lot of high-grade electrolytic zinc which was

"..--_"-• ;._-"-"-: ; i ;•_"—" ili~'—a~i.-. : . " - - '-. ".."_._: i is. : --.i\zrsz'~. : \~ .

~. z.i- a: • s-_ and sealed in a polyethylene pouch to minimize contamination.

Homogeneity testing was performed by NBS Washington and NBS Boulder with samples

selected for the testing carefully chosen to represent the extreme variations that might be

expected as a result of the preparation procedures. Although the spark-source mass

.-.orographic results indicated gross inhomogeneity for lead, thallium, and bismuth, the

residual resistivity measurements indicate that this segregation should be minimized

provided the sample size is increased to ten grams or more and is representative of the full cross section. Activation results revealed some relatively minor inhomogeneity for sodium

antimony. Residual resistivity ratio (B.273k/R-4k) results varied from 33,000 to

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. E. Michaelis.

. v.TION

Before use, it is recommended that possible surface contamination be removed by placing

the sample in high-purity dilute nitric acid for about one minute, followed by rinsing in

distilled water.
U. S. Departm^Wof Commerce

C. RS^mith

^ejar^tarjyNational JJi A. V.

APPENDIX B

Certificate of &nalp*t£

Standard Reference Material 683

Zinc Metal

1

This standard of zinc metal is issued as a special research material to further both

chemical and physical methods of characterization. Two other zinc metal standards are also

available: SRM 682, High-Purity Zinc, and SRM 782, Intermediate-Purity Zinc. All three

standards were prepared from the same starting material.

Element 2

Recommended

Value

(ppm by wt.)

Range of Values

Reported 3 (ppm by wt.)

Method of

Analysis 4

Lead 11.1 (9.6 - 11.3) SSMS-ID,POL

Copper 5.9 (5.3 - 6.1) SSMS-ID, POL

Iron 2.2 (1.7 - 3.1) POL,SPPH

Silver 1.3 (1.0 - 1.4) SSMS-ID, NAA

Cadmium 1.1 (1.0 - 1.2) . SSMS-ID, POL

Thallium (0.2)

5 (0.17 - 0.18) K \iSSMS-ID

Tin (0.02) (0.013 - ^^

SSMS-ID

1. The zinc is in the form of semicircular bar segments about 2 1/4 3/4 inch long.

, 1 inch deep at mid-diameter, and

In the course of analysis by neutron activation, detected and are reported with an estimated upper

Potassium was not

Aluminum, antimon

these elements present

vere sought. The following elements were not

it oTBtyjceMration in parts per million by weight:

Sc <<0.003)

V «0.005)

W «0.0001>

ie emission spectroscopy or by neutron activation at the 0.2 ppm level.

id sodium were detected by several techniques. The results were variable, but in no case are

i greater concentration than 3 ppm. Gold appears to be < 0.02 ppm.

3. The range of values reported is the extreme variation of the individual results reported by the methods of analysis used. The recommended value is based on considerations of the estimated systematic bias of each of the methods employed. From 7 to 13 individual determinations were made for each element certified.

4. SSMS—ID — Spark-Source Mass Spectrometry — Isotopic Dilution (R. Alvarez and P. Paulsen) POL — Polarography (E. J. Maienthal) SPPH - Spectrophotometry (E. R. Deardorff) NAA — Neutron Activation Analysis (B. A. Thompson and D. A. Becker)

5. Values in parentheses are not certified since only one method of analysis was used, but are provided for additional information on the composition.

Washington, D. C. 20234

July 9, 1968

W. Wayne Meinke, Chief

Office of Standard Reference Materials

(over)

87
This standard has been established to provide a homogeneous reference material for the

analysis of pure zinc and analogous metals. It should also serve a useful function for the

physicist and materials engineer involved in the preparation and characterization of

phosphors and other solid-state compounds, where a knowledge of the purity of the starting

material is important. The material was prepared by Cominco American, Inc. from a special

lot of high-grade electrolytic zinc which was homogenized and cast in the form of

semicircular bars. Each bar was etched, dried, and sealed in a polyethylene pouch to minimize contamination.

Extensive homogeneity testing was performed by NBS Washington and Boulder and the

material was found to be satisfactory for the elements certified. The samples selected for

testing were carefully chosen to represent the extreme variations that might be expected as a

result of the preparation procedures. However, practical limitations precluded the testing of

the number of samples from each bar that would have been required to guarantee absolute

limits of homogeneity. Therefore, some inhomogeneity in the untested material is possible

but not probable. The testing was performed using combinations of the following methods:

optical emission and spark-source mass spectrographic analysis, polarographic analysis, flame

emission and atomic absorption analysis, neutron activation analysis, and electrical measurements for residual resistivity ratios.

Although the spark-source mass spectrographic measurements indicated homogeneity

with respect to microsamples, it is recommended that samples as large as possible be

utilized, preferably representative of the full cross-section.

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. E. Michaelis.

CAUTION

Before use, it is recommended that possible surface contamination be removed by placing

the sample in dilute high-purity nitric acid for about one minute, followed by rinsing in

distilled water.

88
U. S. Depa

C

National A. V

of Commerce

ith

Standards

rectoT

APPENDIX C

Certificate of &nalpgte

Standard Reference Material 685

High-Purity Gold

This standard is provided as a reference source of gold of high purity. It is issued in two

forms, wire and rod. 1 The wire form is intended for applications such as spark—source mass

spectrometry where the low level of impurities in the standard should make it useful for evaluating instrument and system blanks. The rod form is intended for use in other methods

of characterization and in other scientific applications.

INFORMATION ON THE COMPOSITION

Element

Copper

Indium

Iron Oxygen

Silver

SRM No. 685-W

Best Indicated Range of Values

Value Reported 2

(Concentration in Parts per Million by Wei

0.1 (<0.1 -0.26)

0.00 7

( 0.002-0.0

0.3 ( 0.16 -CtD.^0

[2]

4

( 1 [0.1] 1T(W)!.-"-

SRM No. 685-R

Best Indicated Methods of

Vake

[<21

[0.1]

Analysis 3

a, b, c, d

a, d

b, c, d

ed

1. SRM No. 685—W is in the form of wiinl.4 rrnn (0.055 inch) in diameter and 10.2 cm (4 inches) long. SRM No. 685—R is irudSSfornrof rodf/5.9 mm (0.23 inch) in diameter and 2.5 cm (1 inch) long.

2. The range of vaU)crxe|M«^dJ^,tteE^xtreme variation of the individual results from the methods of analysis used. The

"best indicateJWuay lA^aseM^n consideration of the estimated systematic bias of each of the methods employed.

3. Methods of Anal

a. Neutron Activa^n Analysis (W. D. Kinard, D. A. Becker, P. D. LaFleur)

b. Polarography (E. J. Maienthal)

c. Spectrophotometry (T. A. Rush, D. H. Christopher, R. W. Burke)

d. Spark—Source Mass Spectrometry — Isotopic Dilution (P. J. Paulsen, D. E. Kelleher, R. Alvarez)

e. Vacuum Fusion (J . T. Sterling)

4. Values in brackets are possibly subject to greater error since only one method of analysis was employed.

The overall direction and coordination of the technical measurements leading to

certification were performed under the chairmanship of B. F. Scribner.

The technical and support aspects involved in the preparation, certification and issuance

of these Standard Reference Materials were coordinated through the Office of Standard

Reference Materials by R. E. Michaelis.

Washington, D. C. 20234

September 26, 1968

W. Wayne Meinke, Chief

Office of Standard Reference Materials

(over)

89
This standard has been established to provide a homogeneous reference material of

high-purity gold primarily for application in spark—source mass spectrometry. It should also be of interest to the chemist, physicist, and materials engineer since gold has numerous

scientific and industrial applications, especially in the electronics industry. The material

should serve for the development of new or improved methods and techniques in extending

the sensitivity of detection in the determination of trace constituents by chemical, optical

emission, spark—source spectrochemical, activation, and resistivity methods. The material was prepared by Cominco American, Inc. from a special lot of highly purified gold which was homogenized and processed into the wire and rod forms.

In the course of analysis by spark—source mass spectrometry (P. J. Paulsen, D. E. Kelleher), other elements were found to be present. These are listed below with an

estimated upper limit of concentration in parts per million by weight. Because of possible

contamination at these extremely low levels of concentration, some of the elements listed may not arise from the gold itself. The concentrations were estimated from relative sensitivity coefficients computed by assigning all elements the same atomic sensitivity as gold and correcting for the variation of photographic plate sensitivity with mass.

Al <0.3

Ba < .03 C < .1 Ca <1 (est 0.1)

CI <0.1

Cr < .05 F < .02

K <0.2

Mg < .2 Mn < .01 N < .03 Na < .2 Nb < .1 Ni < .05

S <0.07

Sc < .01

Si < .3 Sn < .07 Sr < .03 V < .05 Zn < .04

No other elements were detected with most having estimated limits of detection in the range

of 0.01 to 0.05 ppm.

Extensive homogeneity testing was performed at the NBS laboratories in Gaithersburg,

Md., and in Boulder, Colo., and the material was found to be satisfactory within the limits of precision of the analytical methods used. The samples selected for testing were chosen to represent the extreme variations that might be expected as a result of the preparation

procedures. However, practical limitations precluded testing the number of samples of the

wire and rod material that would have been required to guarantee absolute limits of

homogeneity. The testing was performed by using combinations of the methods of analysis

indicated under footnote 3 (see over), but also including optical emission spectrochemical

analysis (R. Alvarez), and electrical measurements for residual resistivity ratios

(J. C. Moulder, V. A. Deason, R. L. Powell).

CAUTION

Before use, it is recommended that possible surface contamination be removed by placing

the sample in warm aqua regia (3 HC1 + 1 HNO3) for approximately five minutes, and then

followed by rinsing in distilled water.

90
U. S. Depart

Mauric

Sen

National A. V

of Commerce

Stans

^)f Standards

irector

APPENDIX D

(Eerttftcate of Analyst*

Standard Reference Material 481

Gold-Silver Wires for Microprobe Analysis

These standard reference materials are designed for use in quantitative elemental

microprobe analysis. Although the selection of this particular system was circumscribed by

the requirements of standard reference materials for electron probe microanalysis, the

materials will be equally useful for other micro techniques. Accurate chemical characterization and the achievement of homogeneity on a microscopic scale was given special emphasis.

SRM 481

wire

A

B

C

D

E

F

Color

code

Nominal

comp

Cominco U.S. Bureau

American 3 of the Mintb Au Au Ag

Percent by weight

NBSC Au Ag

Average

Value d Au Ag

Gold AulOO

Gray Au80-Ag20

Yellow Au60-Ag40

Blue Au40-Ag60

Red Au20-Ag80

Silver AglOO

lOO.On

80.00

60.01

39.99

22.42

80.02

60.11

40.03

22.42

20.00

39.85

59.90

77.59

85.13

60.04

40.06

22.46

J

i) 19.93

39.98

59.96

77.56

80.0,

60.0,

40.0c

22.4,

19.96 39.92 59.9,

77.5

100.0

8

o

a The fire assay method was employed for the determination of Au by Cominco American.

b At the U.S. Bureau of the Mint, Au was determined by fire assay and Ag was determined

by titration as AgCl.

c At NBS, Au was determined from the residue after treatment of the alloys with HN03

. The Au residue was dissolved in aqua regia, filtered, the Au precipitated by sulfurous acid,

and weighed. Ag was determined gravimetrically as AgCl in all four alloys, and also coulometrically in the 80 percent Ag alloy.

d The results of individual laboratories agree within a range of ± 0.1 percent absolute from

the average values. The agreement between results by the different methods and analysts,

and the summation of results close to 100 percent for each binary alloy, indicate that the

averages are free from significant bias.

The set of standard reference materials, SRM 481, consists of six wires each having a diameter of approximately 0.5 mm and a length of approximately 5 cm. For identification,

the four alloy wires were covered with an easily removable colored coating.

The overall direction and coordination of technical measurements leading to certifica- tion were performed under the chairmanship of B. F. Scribner.

The technical and support aspects involved in the preparation, certification, and

issuance of these standards were coordinated through the Office of Standard Reference

Materials by R. E. Michaelis.

Washington, D. C. 20234

February 14, 1969 (over) W. Wayne Meinke, Chief

Office of Standard Reference Materials

91
PREPARATION AND PURITY: The standards were prepared by Cominco American Inc. in the

form of wires approximately 150 meters long. The end members of the series, as well as the

starting materials for the alloys, were of the highest purity grade and precautions were taken

to minimize contamination. Two of the alloy standards were heat-treated at NBS to improve

microhomogeneity. The pure metal standards were examined by the residual resistivity ratio technique and the total of electrically active impurities in each was estimated to be about

0.001 percent. The gold-silver wires were examined spectrographically for metallic

impurities; no significant impurities were found at detection limits ranging from 0.0001 to 0.010 percent.

LONGITUDINAL HOMOGENEITY: Variation in composition along the full length of each alloy

wire was investigated by electron probe microanalysis for areas 25 /xm diameter on cross sections at three to five positions along the wire including the two ends. The observed

differences in composition for the positions, expressed as the range between the highest and

lowest values for each alloy, were as follows:

Nominal Composition Au80 Au60 Au40 Au20

Observed range! 0.3% 0.6% 0.3% 0.5%

Homogeneity along the wires was also tested by measurement of the residual resistivity

ratio. These measurements indicated that the variation (macroscopic) of composition along

all standard wires was less than 0.1 percent absolute. Further information on longitudinal

homogeneity of the wires was obtained by determinations of Au at the extreme ends of the

alloy wires by the Bureau of the Mint; the data also indicate that the extreme variation

along the wires is less than 0.1 percent absolute.

Transverse and Micro Homogeneity: Variation in composition within the above mentioned cross sections of the wires was investigated by electron probe microanalysis. For each

cross section, measurements were made along two diagonals at right angles. On each

diagonal, determinations were made at 25 points, 1 jum or less in diameter, starting and

ending at approximately 25 jum from the edge. For each alloy, the element which could be

determined with the better precision was used in the evaluation. The variation was

calculated in terms of the standard deviation for an individual determination for each

traverse. In the table below, the variation is presented as the range between the lowest and

highest observed standard deviations for the six to eight traverses performed on each alloy.

Range of Standard

Nominal Composition Element Determined Deviation for Traverses2 Au80 Ag 0.08-0.11%

Au60 Au .08- .16 Au40 Au .08- .13 Au20 Au .12- .37

92
The homogeneity on a microscopic scale was further investigated by performing

quantitative measurements in two arrays of 10 x 10 points (1 jum diameter) on each of the

cross sections. The distance between adjacent points was 3.5 /im. This was repeated on

several cross sections so that 6 to 8 arrays were obtained on each alloy. For the element

which could be measured with better precision, the range is given between the lowest and

highest observed standard deviation for an individual determination for the 6 to 8 arrays for each alloy.

Range of Standard

Nominal Composition Element Evaluated Deviations for Arrays3 Au80 Ag 0.09-0.15%

Au60 Au .18- .57 Au40 Au .19 - .25 , Au20 Au .11 - .66

(Note: This range and the two ranges in the following tables are close to the precision of

the method and should be considered upper limits of estimates of inhomogeneity.)

Extensive homogeneity studies were performed with the electron probe microanalyzer

at NBS by M. A. Giles, R. L. Myklebust, C. E. Fiori, and K. F. J. Heinrich. Measurements of

residual resistivity ratio were made at NBS, Boulder, Colorado, by R. L. Rutter, J. G. Hust,

and R. L. Powell. Heat treatment of the alloys at NBS was performed by G. E. Hicho and

M. R. Meyerson. Spectrographs survey analyses were made at NBS by V. C. Stewart. Determinations of composition were made at Cominco American, Inc., Spokane, Washington, by T. A. Rice; at the U.S. Bureau of the Mint, Washington, D. C, by

H. G. Hanson, Jr.; and at NBS by R. A. Durst, G. Marinenko, and C. E. Champion.

93

U. S. Depart&ri^of Commerce APPENDIX C.

A. v. National '. WS&iiSm Standardsirector Certificate of &nalps(fe

Standard Reference Material 1051b

Barium Cyclohexanebutyrate

(Standard for Determination of Barium in Petroleum Products)

This compound was prepared to insure material that is essentially free from other metals and has suitable

solubility, compatibility, and uniformity for use in the preparation of a standard of barium in lubricating

oils. The compound is certified to one part per hundred of barium, and every effort should be made to maintain a uniform procedure by following the directions in this certificate. CHEMICAL AND SPECTROGRAPHIC ANALYSES

Barium, percent 28.7±0.1

The uncertainty shown represents the 95 percent confidence limit of the mean based on fifteen determinations and allows for the effects of possible sources of known error.

Barium was determined by wet-ashing a 0.5 g sample (dried for 72 hours over phosphorus pentoxide) and

the resulting insoluble material removed by filtration, ignited at 900 °C and weighed as barium sulfate.

The compound was examined spectrographically for metallic impurities. A 5 mg sample of the compound was excited in a direct-current arc and the photographed spectrum was examined for the

characteristic lines of 51 elements. No significant impurities, other than strontium, were found. The strontium content of this material was the only impurity element present that would interfere with

the barium determination. Samples, 0.5 g, were wet-ashed, diluted and analyzed by both flame-emission and atomic-absorption spectrometry. A strontium content of 0.05 percent was found. The barium

determination given above has been corrected to account for this interference.

STABILITY. Tests show that standard lubricating-oil solutions of this compound with concentrations of barium up to 500 ppm are stable for several weeks when prepared by the directions given on the reverse of

this certificate.

COMPATIBILITY.—Lubricating-oil solutions of this compound have been found to be compatible with

lubricating-oil solutions of the other compounds in this series. Blends of several different compounds have been prepared by the procedures given in the certificates for the other compounds. (Tests have not been

carried out to insure compatibility with the various additives that may be in the oils to be analyzed.)

The barium cyclohexanebutyrate was prepared by Distillation Products Industries of Rochester, N.Y.

Chemical analysis was conducted by B. B. Bendigo, spectrochemical analysis by V. C. Stewart, and

flame-emission and atomic-absorption analysis by T. C. Rains. The overall direction and coordination of the technical measurements leading to certification were performed under the chairmanship of J. K. Taylor.

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 W. Wayne Meinke, Chief

July 15, 1968 Office of Standard Reference Materials

(over)

95
DIRECTIONS FOR PREPARING LUBRICATING-OIL SOLUTIONS OF BARIUM

CYCLOHEXANEBUTYRATE

Transfer approximately 0.2 g of this compound to a small beaker and dry at 110 °C for 2 hours

(alternatively, the sample may be dried over phosphorus pentoxide for 72 hours.) (Tightly close the bottle containing the remainder of the compound.) Quickly and accurately transfer 0.174 g of this dried salt to a weighed 200-ml flask. (This weight of salt is equivalent to 50 mg of barium.) Add 3 ml of xylene and 5 ml

of 2-ethylhexanoic acid and heat the flask on a hot plate, with swirling and without charring, until a clear solution forms. Add to the hot solution 80 to 90 ml of lubricating oil and gently shake the flask to mix the

contents. Allow the flask to cool to room temperature and add enough lubricating oil to bring the total weight of the contents of the flask to 100 ±0.5 g. Stopper the flask and shake gently to insure a homogeneous solution. The concentration of barium in this solution is 500 ppm.

96
U. S. Departi^en^ of Commerce

Maurice^lf. Stans

Secretary

APPENDIX F

National Bjure^ft of Standards

Mrector Certificate of &nalp£t$(

Standard Reference Materials 1159, 1160

Electronic and Magnetic Alloy Standards

Element

Carbon

Manganese

Phosphorus

Sulfur

Silicon

Copper

Nickel

Chromium

Molybdenum

Cobalt

Iron

SRM 1159 SRM 1160

Percent (by weight)

0.007 0.019

•305 .55 .003 .003

.003 .001

.32 .37 .038 .021 48.2 80.3

0.06 0.05

.01* 4.35 .022 0.054<t 51.0 14v3 V

Samples are 1% m (3.1 cm) in diameter ands%\f^Tl'^c&") thick, and are issued

in the annealed condition. ^< (( The provisional value listed for an e^meVt l^vtb^present best estimate of the true

value based on the results of the coc>^feratrsz». airalytlcal program. The provisional value

is not expected to deviate from thaitriMt vaUje by more than ± 1 in the last significant

figure reported ; for subscrjjjt^m^rjk, th)p-deviation is not expected to be more than ± 5

in the subscript figure, ff "\\ >1 The material fe^^eVs^andArds was prepared in a vacuum induction furnace at The

Carpenter SteataBSmpasx^teaaing, Pennsylvania, and supplied to NBS in the final form

following a senate ©^fabrication designed to produce material of the highest possible

homogeneity. ^.

Homogeneity testing was performed at NBS by D. M. Bouchette, S. D. Rasberry,

and J. L. Weber, Jr., and was found to be satisfactory for the elements certified. Cooperating with NBS in the analytical program were the following: Armco Steel Corporation, Research and Technology, Middletown, Ohio; Falconbridge Nickel Mines,

Limited, Metallurgical Laboratories, Thornhill, Ontario, Canada; The Carpenter Steel Company, Metallurgical Department, Reading, Pennsylvania; and Westinghouse Electric

Corporation, Research and Development Center, Pittsburgh, Pennsylvania.

The overall direction and coordination of the technical measurements leading to

certification were performed under the chairmanship of B. F. Scribner.

The technical and support aspects involved in the preparation, certification, and

issuance of these Standard Reference Materials were coordinated through the Office of

Standard Reference Materials by R. E. Michaelis.

February 18, 1969 W. Wayne Meinke, Chief

Washington, D.C. 20234 Office of Standard Reference Materials

97

U. S. DepartA^arttf of Commerce

Maurice||i. Stans

Sectary

APPENDIX G

National Bpre

A. V.

j3: Standards

director Glerttftrai?

Standard Reference Material 1800

Microstandard Ion-Exchange Beads

Calcium Loaded

(10-" to 10-'J grams)

This Standard Reference Material is intended as a source of minute, known

quantities of calcium. The calcium is attached to ion-exchange beads that are 5 to 25 microns (jim) in diameter. The matrix is composed of a homogeneously sul- fonated network of a cross-linked copolymer of styrene with 8 mole percent

m-divinylbenzene. The calcium is electrostatically attached to the sulfonate groups. The calcium ions can be displaced by addition of an aqueous electrolyte solution. Any single bead contains an amount, w, of calcium, sulfur, carbon, hydrogen,

oxygen (and some water) according to the equation: mCa = PaV, where V =

wdyQ is the volume of the bead, and mc» and pca are the mass and partial density, respectively, for calcium. The partial density of calcium in a typical dry

bead is certified as: Pca = 0.135 ,± 0.010 g/cm3

. The superscript (°) is used to denote reference to a dry resin bead. The value of p° and its error (standard

deviation) is computed from neutron activation analysis and from electron microprobe analysis of forty individual beads. The microprohe measurements also agree with the expected constancy in the calcium to s#lfui\re&tioN

Analysis of gross quantities of this material

subscripted matrix elements p§ = 0.21 5 , p£

of the dry material ranges from l.4£L(1wrni

rtial densities of the

.06. The bulk density

(maximum) g/cm3

.

material after vacuum drying at

/weeks or more to ordinary atmospheres

range 20 to 40 percent, the partial densities will

The preceding measuremeirtsrafe

120 °C for 16 hours. If exposed foXyt1 with relative humidit^s^QMN!

be reduced accopiinmto tna amount of sorbed water. Then, the partial density of

each of the^l^&^sjs^i^e bead must be adjusted by multiplying by the factor

0.87. In tM^mseoofTj&lcium, the corrected partial density is: p Ca (20-40% RH) = 0.117 ± (M09 g/cm:\

Washington, D. C. March 17, 1969

20234 W. Wayne Meinke, Chief

Office of Standard Reference Materials

Caution : Inadvertent contamination by water, i.e., condensation, is sufficient to cause the loss of calcium by ion exchange hydrolysis. It is therefore essential that

this microstandard be kept at less than 50 percent relative humidity.

(over)

99
Measurements leading to the certification of this Standard Reference Material were carried out by D. A. Becker, L. A. Currie, H. D. Dixon, R. A. Durst, K. F. J. Heinrich, E. C. Kuehner, R. L. Myklebust, R. A. Paulson, T. C. Rains,

and G. Schmuckler of the Analytical Chemistry Division.

The overall direction and coordination of the preparation and technical

measurements leading to the certification of this material were performed under

the chairmanship of D. H. Freeman.

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.

USE OF MICROSTANDARD

The present microstandard was prepared by casting a dispersion of dry, cal- cium-form, ion-exchange beads onto a clean glass slide. The beads are naturally

attracted to the glass surface. The same attraction occurs when the beads are touched gently with a probe, and this permits them to be moved from the slide to another place.

Diameter measurement : Under microscopic examination it will be observed

that the majority of the beads in this standard are spherical. The nonspherical

beads are readily identified and rejected on the basis of their appearance. Bead

diameter measurements are then practicable to an estimated total uncertainty of

± 0.1 micron (/*m). Such measurements are not difficult, but they do require

proper microscopic measuring apparatus and illumination technique (such as Kohler illumination with the use of an interference filter at «560-nm) . These

procedures are described in the literature (D. H. Freeman, "Advances in Ion Exchange," Volume 1, Marcel Dekker, Inc., New York, 1966, chapter 5).

Storage : The microstandard beads must be protected against exposure to excessively humid atmosphere and, for practical purposes, it should be assumed

that the standard is destroyed if exposed to humidities exceeding 50 percent

relative humidity. Storage over a mild desiccant is recommended. Alternatively, the beads may be vacuum dried at 120 °C for approximately 16 hr in order

to duplicate the dry state to which the composition measurements refer. After

drying, the beads can be kept in the dry state by storing them over fresh phosphorous pentoxide, or they can be immersed in a dry hydrocarbon fluid. There is some loss in accuracy (but a gain in convenience) by working in atmospheres of

controlled humidity. For example, isopiestic equilibration will occur after ap- proximately two to four weeks of storage over an aqueous calcium chloride

solution in the range from 0.2 to 0.4 water activity (approximately 7.2 moles

CaCl2 per kg of PLO for 30% relative humidity).

These standards can be used in a variety of ways. A single bead can be treated

with electrolyte to release the ion-bound calcium. Or, a bead can be observed

destructively as in the laser microprobe where the sample is vaporized and then

analyzed by emission spectroscopy. Single beads can be viewed by an instrument

such as the electron microprobe which is capable of identifying and measuring

relative amounts of the calcium or sulfur atoms contained by the beads or by

comparative samples.

100 <r U. S. GOVERNMENT PRINTING OFFICE : 1 969 —392-247/89
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