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452

Spectrochemical

Analysis Section:

Summary of Activities

July 1967 to June 1968
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 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 three broad program areas and provides central national services in a fourth. 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, and the Center for Radiation Research.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the

United States of a complete and consistent system of physical measurement, coor- dinates that system with the 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 Standard Reference Data and a group of divisions organized by the

following areas of science and engineering

Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic Physics—Cryogenics2—Radio Physics2—Radio Engineering2—Astrophysics2—Time

and Frequency.2 THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to methods, standards of measurement, and data needed by industry, commerce,

educational institutions, and government. The Institute also provides advisory and

research services to other government agencies. The Institute consists of an Office of

Standard Reference Materials and a group of divisions organized by the following

areas of materials research:

Analytical Chemistry—Polymers—Metallurgy — Inorganic Materials — Physical

Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides for the creation of appropriate opportunities for the use and application of technology within the Federal Government and within the civilian sector of American industry. The primary functions

of the Institute may be broadly classified as programs relating to technological meas- urements and standards and techniques for the transfer of technology. The Institute

consists of a Clearinghouse for Scientific and Technical Information,3 a Center for

Computer Sciences and Technology, and a group of technical divisions and offices organized by the following fields of technology

Building Research—Electronic Instrumentation — Technical Analysis — Product

Evaluation—Invention and Innovation— Weights and Measures —Engineering

Standards—Vehicle Systems Research.

THE CENTER FOR RADIATION RESEARCH engages in research, measurement,

and application of radiation to the solution of Bureau mission problems and the

problems of other agencies and institutions. The Center for Radiation Research consists of the following divisions:

Reactor Radiation—Linac Radiation—Applied Radiation—Nuclear Radiation.

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

2 Located at Boulder, Colorado 80302.

3 Located at 5286 Port Royal Road, Springfield, Virginia 22151.
UNITED STATES DEPARTMENT OF COMMERCE

C. R. Smith, Secretary

NATIONAL BUREAU OF STANDARDS • A. V. Astin, Director

NBS TECHNICAL NOTE 452

ISSUED SEPTEMBER 1968

Spectrochemical

Analysis Section:

Summary of Activities

July 1967 to June 1968

Edited by Bourdon F. Scribner

Spectrochemical Analysis Section

Analytical Chemistry Division

Institute for Materials Research

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 - Price $1
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 1968 we plan to issue these summaries for all of

our Sections. The following is the fourth annual report

on progress of the Spectrochemical Analysis Section.

W. Wayne Meinke, Chief

Analytical Chemistry Division

111
PREFACE

This is the fourth 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

C. Computer Programs for Processing of Data

Recorded on Paper Tape 5

2. OPTICAL SPECTROMETRY 8

A. New Equipment 8

1. Spectrometer Readout 8

2. High-aperture Spectrograph 12

B. Study of Plasma Torch 14

C. Test of Program for Calibration of Photographic Emulsions 18

D. Applications to Analysis 22

1. Standard Reference Materials . 22

2. Other Analyses 24

3. ELECTRON PROBE MICROANALYSIS 26

A. Basic Considerations 26

B. Techniques and Instrumentation 26

1. Matrix Scanner 26

a. Timer-sealers 26

b. Matrix Generator 26

c. Scan Control 27

d. Print-out Control 28

e. Paper Punch 28

2. Lithium-drifted Silicon Detector 29

3- Color Composites for Area Scanning .... 31

C. Quantitative Electron Probe Microanalysis . . 32

1. X-ray Mass Attenuation Coefficients ... 32

2. Study of Uncertainty in Corrections for

Quantitative Analysis 3^

3- Standard Reference Material Measurements . 35

4. Proceedings of a Seminar on Quantitative

Electron Probe Microanalysis 35

5. -Literature Research 37

4. X-RAY FLUORESCENCE SPECTROMETRY 38

A. Modification of Equipment 38

B. Research Activities 40

C. Examples of Applications 42

VI
PAGE

5. SPARK SOURCE MASS SPECTROMETRY 45

A. Instrument Improvements 45

B. Homogeneity of Ion Sensitive Emulsions and

Precision of Ion Beam Measurements 47

1. Introduction 47

2. Method 47

3. Results 48

4. Circumvention of Inhomogeneities in Ion

Sensitive Emulsions 51

5. Summary and Interpretation of Results . . 52

C. Stable Isotopic Dilution Analysis of Pure

Materials Using Preconcentration Techniques 52

1. Zinc 52

2. Platinum 53

D. Plate Calibration Functions 56

E. New Computer Programs 57

6. ANALYSIS OF HIGH PURITY MATERIALS 59

A. Zinc 59

B. Platinum 6l

C. Gold '.

. 62

7. PERSONNEL AND ACTIVITIES 64

A. Personnel Listing 64

B. Publications 65

C. Talks Given 67

D. Committee Activities 69

8. ACKNOWLEDGMENTS 71

9. LIST OF REFERENCES 72

APPENDIX: Certificates for NBS Standard Reference

Materials: Platinum, Cast Steel, and

Ductile Iron 75

LIST OF FIGURES

FIGURE NO.

1. Flow chart for processing data recorded on

paper tape 6

2. Digital readout for emission spectrometer 9

vii
PAGE

3. Readout format for data to be processed on

a time-sharing computer 10

4. Readout format for data to be processed in

the NBS computer center 11

5. High-aperture spectrograph for use with

low-intensity light sources 13

6. Effect of phosphate on calcium line emission

in the plasma torch 17

7. Effect of aluminum on calcium line emission

in the plasma torch 17

8. Computed slope as a function of relative

intensity of line pair. Data for an SA-1

plate at 3200 8 20

9- Computed slope as a function of relative

intensity of line pair for Q-2 plate at

3200 A 20

10. Effect of scattered light in microphotometer

on linearity of plate calibration with

Kaiser transform 21

11. Device for digital matrix scanning 27

12. Example of matrix scanner print-out .... 28

13. Section of computer output for homogeneity

testing 30

14 . Non-diffractive silicon detector mounted on

electron probe microanalyzer . (A) solid

state detector, and (B) preamplifier ... 31

15. Diffractive spectra of a 60 gold - 40 silver

alloy 32

16. Non-diffractive spectra of Ag, Au, and a

60 Au - 40 Ag alloy 33

17- X-ray fluorescence analog and digital signal

processing electronics 39

vi 11
PAGE

18. Teletypewriter print-out produced by

digital interface 40

19- Plate holders for mass spectrograph 46

20. Ion beam measurements on platinum mass

lines 50

21. Electrodeposition cell 60

LIST OP TABLES

TABLE NO.

1. Enhancement factors in emission and

absorption 15

2. Programs used in x-ray fluorescence

analysis 4l

3. X-ray fluorescence determinations of

manganese in ferrosilicon powder 42

4. X-ray fluorescence determinations of silicon

in cast steel 44

5. Ion beam measurements on 21 replicate mass

spectra of platinum 49

6. Isotope dilution determinations of silver

and tin in four samples of zinc

SRM 683 53

7- Average copper, silver, and tin concentrations in shot and bar samples of zinc ... 54

8. Comparison of results of three types of

mass spectrographic analyses to certified

values for Pt 68l 55

9- Concentrations determined by isotope dilution in Platinum SRM 681 63

IX

ACTIVITIES OF THE NBS SPECTROCHEMICAL

ANALYSIS SECTION

July 1967 through June 1968

Edited by Bourdon F. Scribner

ABSTRACT

A summary is given of activities of the NBS Spectrochemical Analysis Section for the year July 1967 through June 1968

This covers research activities, improvement in equipment,

and applications in analysis including the certification

of standard reference materials . In optical spectrometry

studies were completed on the plasma torch as a means of

excitation of solutions, and on computer programs for the

calibration of photographic emulsions. In electron probe

microanalysis a matrix scanner for automatic point-by -point

grid scans was tested and a lithium-drifted silicon detector

was installed for non-diffractive x-ray dispersion. A study

was made of color composites for combining the information of

three x-ray area scans. In quantitative probe analysis, measurements were made of x-ray mass attenuation coefficients,

and a study of atomic number corrections is underway. In

x-ray fluorescence considerable improvement was realized by

replacement of electronics by solid state circuitry, and

methods are being studied for corrections of interelement

effects, utilizing the digital computer. Spark source mass

spectrometry was applied, by means of chemical separations

and by isotope dilution techniques, to the accurate determination of impurities in zinc, platinum, and gold. A

critical study was made of the uniformity of response of

ion-sensitive emulsions over the area of the plates used in

the mass spectrometry. Improvements in the Section's equipment and further developments in computer applications are

also discussed. Listings are given of 23 publications and

19 talks by members of the Section during the year.

XI
Key words

Computing, digital readout, electron probe, emulsion calibration, emulsion sensitivity, gold analysis, isotope dilution

method, x-ray mass attenuation coefficients, microprobe grid

scanner, optical spectrometry, plasma torch, platinum analysis,

preconcentration , silicon detector, spark source mass spectrometry, spectrochemical analysis, standard reference materials, time-shared computer, x-ray absorption coefficients, x-ray

fluorescence analysis, zinc analysis.

XII
1. INTRODUCTION

In the three preceding annual reports in this series we

have described the program and facilities of the Section in

some detail. The first report [1] described the basic program in the areas of optical and x-ray spectrometry, enrichment techniques, and standard reference materials, and also

the equipment that was installed at the old NBS location. The

second report [2] described the new Section laboratories

at the Gaithersburg site with typical examples of laboratory

facilities. A description was also given of the program and

equipment of the spark source mass spectrometry group which

had been added to our Section during that year. Last year's

report [3] described some additions to equipment, especially

digital readout devices, and outlined extensive applications

of computer reduction of data. In each report, the research

activities and the output in terms of publications, talks

given, and analytical work have been recorded.

A. Facilities

The equipment of the Section will be briefly reviewed

as background for this report. The major equipment now

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 micro-photometers , sample

preparation devices, microscopes, teletypewriter readout

devices, etc.

Improvements in equipment this year consist largely of

newly available electronic components which have been added

to bring certain equipment up to high standards of stability

and precision. These include a new readout system for the

3-meter optical spectrometer, an automated grid scan and a

silicon detector for the microprobe, and new solid state components for the single-channel x-ray spectrometer. For observation of the spectra of weak light sources, such as laser

generated vapor plumes, a 0.75-meter f/6.3 optical spectrograph-spectrometer has been obtained. This equipment is

described in appropriate sections of this report.

B . Activities

The Section is organized into four major groups: optical

spectrometry, x-ray spectrometry, spark source mass spectrometry, and enrichment techniques. All of the groups are engaged

in research and in analysis, including the analysis of standard

reference materials. The research, which constitutes about

one-half of the effort of the Section, is often generated by

the analytical problems encountered but may involve basic

studies of considerable complexity.

In optical spectrometry major attention is directed to

the study and improvement of excitation sources. In recent

years the plasma jet, gas sheathed arcs and sparks, and the

laser probe have been studied. This year the activity has

been concerned with the plasma torch. Attention has also

been given to measurement and calibration problems such as

the calibration of photographic emulsions

.

In x-ray spectrometry the electron probe microanalyzer

has been developed to a tool with many important applications,

With the improvement in electronic control and measurement

devices as described in this report much tedious work with

2
this instrument can be automated. Quantitative electron probe

analysis is being systematically investigated with the purpose

of reducing the requirements for standards having compositions

closely resembling the samples.

In x-ray fluorescence analysis attention is being given

to the problem of correction for matrix affects, again in

an effort to improve quantitative measurement and to reduce

the number of standards required.

Spark source mass spectrometry provides a unique tool

for survey analysis, being capable of detecting all elements

in the periodic system at very low concentrations . The

problem of obtaining quantitative analysis is severe and

studies of the variables, such as uniformity of the ion

sensitive emulsion, are being made. To by-pass many of the

measurement problems the application of combined techniques

of chemical separations, isotope dilution, and the spark source

is proving highly effective in the determination of trace elements in standard reference materials.

The magnitude of the second major part of the activity

of the Section — analysis of materials -- is shown by the

following compilation for each of the areas of analysis.

S amp le s Determinations Reports

Optical emission 266 14,598 154

Microprobe 61 6,840 24

X-ray fluorescence 294 2,498 14

Spark source mass 34 1,186 13

These figures include analyses of standard reference

materials which constitute about two-thirds of the samples

analyzed. Examples of this activity are shown in the certificates of analysis for cast steel, ductile iron, and platinum

metal given in the Appendix to this report.

In addition to research and analysis, the Section is

involved in other activities of benefit to the spectroscopic

field. We may include here the preparation of reviews and
bibliographies, consulting on instrumental and analytical

problems, and the organization of discussion meetings on

analytical problems of critical importance.

The biennial review on Emission Spectrometry was published

this year; another review is forthcoming on the electron probe.

Bibliographies are in preparation in both of these fields.

Two meetings held recently at NBS demonstrate a productive type of group attention to analytical problems. A

meeting of a small group on quantitative microprobe analysis,

held June 1967 > has resulted in a 300-page book on this subject which is currently being released. The meeting was

arranged by Dr. Heinrich who has edited the papers constituting

the book. In October, 1967 a workshop on mass spectrometry

was held at NBS with Dr. Ahearn and Dr. Paulsen as co-chairmen.

It is expected that this workshop will be held periodically

as the need continues.

An area of considerable interest, in which the Section

has been of assistance to others, is the application of

computer techniques. A description of this work with outlines

of some 13 computer programs has been published in the past

year [4], This effort is continuing and programs of value

to our own work are proving useful to others

.

Two programs, recently developed by Mr. Rasberry of our

Section, apply generally to the processing of data recorded

on paper tapes. Because of the general utility of these programs, we include brief descriptions in the following section.

Other computer applications are described in the body of the

report

.

B. F. Scribner
C. Computer Programs for Processing of Data Recorded

on Paper Tape

Two FORTRAN programs, CPUNCH, and MTPRNT , and a FORTRAN

subroutine, PTLOAD, have been written to facilitate the reduction of data which is stored on paper tape when a computer

has no direct facility for paper tape processing. These

programs are for tapes containing integer numeric data in

tabular arrangement. Normally, paper tapes automatically

produced as output of scientific instruments are of this type.

Descriptions of these programs and illustrations of

application options are given in the following sections. One

of the important techniques described here is the use of

MTPRNT for one-pass processing of data recorded on paper tape

by OMNITAB, the NBS general purpose statistical and numerical

analysis program.

Listings of program decks, control cards, and example

data are available on request to this laboratory.

1. Program PTLOAD

PTLOAD is a FORTRAN subroutine (approximately 48 statements) which loads, into the calling program, data which

have been transcribed from paper tape to magnetic tape. It

may be called by any program and is required by both CPUNCH

and MTPRNT. As an example of the action of the subroutine,

let us consider a call made as follows

:

CALL PTLOAD (NUMBER, 10 0, 6)

This call causes characters to be read into core memory from

the magnetic tape until 600 numeric characters have been

found. These integers are packed into 100 six-digit numbers

which are transferred to the main program as the vector

NUMBER (1) through NUMBER (100).

Re-forming tables of data is left to the main program

and should be arranged to account for the order (either

row-order, or column-order) of the data on the original paper

tape

.

5
OFF-LINE

DIGI-DATA

ON-LINE

UNIVAC 1108

USER PROGRAM

PTLOAD

(printer)

i> \ / 2-FOR-l CONVERSION

USER PROGRAM

"7

CPUNCH

PTLOAD

MTPRNT

PTLOAD

USER PROGRAM OMNITAB

Figure 1. Flow chart for processing data recorded on

paper tape.
Three uses of PTLOAD are illustrated in Figure 1. Each

time PTLOAD is entered a direct listing of the vector NUMBER

is printed.

2. Program CPUNCH

CPUNCH is a FORTRAN program (approximately 35 statements)

which is used in the transcription of data from paper tape to

punched cards. After data have been loaded into this program

by PTLOAD they are ordered to the format of the original data

table or to specifications provided by the user. When formation of the table is complete, those columns specified by

the user for output are punched, in column order, onto cards.

This program is especially useful when data editing is required. See path B of Figure 1.

3. Program MTPRNT

MTPRNT is a FORTRAN program (approximately 35 statements)

which is used in the restructuring of data from an input magnetic tape with the new image written on a second magnetic

tape. After data have been loaded into this program by

PTLOAD, they are ordered to the format of the original data

table or to specifications provided by the user. When formation of the table is complete, those columns specified

by the user for output are recorded, by columns, on magnetic

tape in card images.

Columns of data stored in this fashion may be processed

by any appropriate program; however, one of the principal uses

for MTPRNT is one-pass OMNITAB processing of data recorded

on paper tape. These techniques are options 1 and 2 of

path C in Figure 1. Option 2 is also useful, via path D, to

extend the utility of OMNITAB to the user's FORTRAN programs.

S. D. Rasberry
2. OPTICAL SPECTROMETRY

During the past year, two research projects have been

completed. One was a study of a high-frequency, inductioncoupled, plasma torch; two papers describing the results of

this investigation are in press [5, 6]. In addition, a thorough study has been made of the computer program KAISER

for calibration of photographic emulsions

.

The facilities for optical spectrometry have been

improved by the installation of a new digital readout for

one spectrometer and by the purchase of a high-aperture

spectrograph/spectrometer, together with associated optical

and electronic equipment, for use with the laser probe

and other low-intensity light sources.

The vacuum spectrometer described in the last report

in this series [3] has been checked out and placed into

operation. However, much investigation is still needed to

establish proper operating conditions for some of the unusual samples that we are called upon to analyze.

Homogeneity testing and analysis of Standard Reference

Materials continue to be major efforts in optical spectrometry. The number of man-years devoted to this activity is

increasing rather steadily. This is due in part to the increasing number and variety of Standard Reference Materials

being prepared. The analytical problems become more complex

as new types of materials are encountered or as additional

elements are certified in replacement Standard Reference

Materials

.

A . New Equipment

1 . Spectrometer Readout

Figure 2 shows a new readout that has been installed

on one of the emission spectrometers. It replaces a unit

which was, as far as we know, the first digital readout

on any emission spectrometer. The new readout incorporates

8
Figure 2. Digital readout for emission spectrometer. (The large console contains the

integrating capacitors and electronics

for dark-current and background correction and digitizing. Data are printed

on the teletypewriter).

several features which were not in the unit it replaces,

and it assures improved reliability through the extensive

use of solid-state electronics

.

The primary data from the readout are four-digit numbers

which are inversely proportional to the logarithms of the intensity ratios being measured. Up to 18 four-digit numbers

of this type, together with auxiliary information, are printed

on a teletypewriter and simultaneously punched into the paper

tape. The auxiliary data include a serial number for each

run, the sample number, and a check voltage reading that provides a test of the readout electronics on each run.

9
The readout incorporates several optional features.

These include provisions for 'correction of the signal from

each photodetector for dark current, and for correction

of each line intensity for background. Also, optional

formats for the readout are provided.

The readout format used in a particular case depends

on how the data are to be handled subsequently. When a

relatively small amount of data is recorded, as when the

number of samples and the number of elements determined are

few, the format shown in Figure 3 is used and the data may

be processed on a time-sharing computer. In Figure 3 the

first number on each line is the serial number for the run,

042Q DATA 4190*1797*2561 '0782*3401*1653*2322*2975*1852*0605*2113

Figure 3. Readout format for data to be processed

on a time-sharing computer.

which also serves as the line number for the computer. This

is followed by the word DATA, as required by the time-sharing

computer we use. The following data points are separated

by commas, as the computer also requires. The first

four-digit number after the word DATA is the sample number,

which was entered by the operator on a dial switch on the

readout. This is followed (optionally) by the reading for

the background channel and a check voltage reading, and then

by the readings for the analytical channels.

For extensive data, it is more efficient to do the

calculations on the batch-loading computer in the NBS computer center. The same format shown is Figure 3 could be used

for that computer, but an alternate format, shown in Figure

4, is available. In this case, the data follow the same

sequence as in Figure 3, but the word DATA and the commas

are omitted. When the number of analytical channels read

10
is too large for the data to fit on one line, the numbers

continue on a second line. In the example shown in Figure 4,

18 analytical channels were recorded.

0421 4190 1797 2561 0782 3401 1653 2322 2975 1852 0605 2113 2022

1772 1615 0802 2386 2590 3213 0345 3090 2555

Figure 4. Readout format for data to be processed in

the NBS computer center.

The large NBS computer does not presently provide for

direct data input via the punched paper tape from this

readout. Therefore, when the data are to be entered into

that computer, they are first transferred to a magnetic tape,

as is described in Section 1C of this report.

Another digital readout, described in the last report

[3, p. 9] has been modified slightly to improve its performance. Previously, the signal was digitized during a onesecond period after stepping to each capacitor in the spectrometer console. A one-half second delay has been interspersed between the stepping signal and the start of digitizing to permit the electrometer amplifier which couples the

capacitor to the digitizer to come to balance. A second

modification provides a warning when the charge on any

capacitor exceeds 10 volts. In that case, the characters

"XXXX" are printed in place of the four-digit number normally

given.

Until recently, the computer processing of data from the

spectrometers had been restricted primarily to the statistical computations required in homogeneity testing. A program for fitting analytical curves, described in the last

annual report [3], has been tested extensively and appears

to give good results. This program is now being used on the

time-sharing computer to process analytical data, and it is

being translated into FORTRAN for the large computer in the

11
NBS computer center. We anticipate that in the near future

it will be possible to have analytical results for as much

as a whole day's work on the spectrometer processed in a few minutes

.

2 . High-aperture Spectrograph

Figure 5 shows the high-aperture spectrograph which

has been purchased for use with the laser probe and other

low-intensity sources. It is a Czerny -Turner mount, grating

spectrograph with a focal length of 0.75 m. With a grating

approximately 100 mm square, the optical aperture is about

f/6.3, depending on the grating angle. As a spectrograph,

the instrument can accommodate 4 x 10 in. plates or Polaroid

film; as a photoelectric spectrometer, one exit slit is now

installed and an attachment can be added later to provide

more exit slits if they are needed.

Experience with a large f/30 spectrograph and a few

exposures on an f/1.5 instrument indicated that an aperture

between f/5 and f/10 would be approximately optimum for the

laser probe when pit sizes are about 50 urn in diameter. An

instrument with a larger aperture might permit working with

considerably smaller samples, but it would, require the

acceptance of much poorer resolution and dispersion at the

present state of spectrograph design'. Nevertheless, the new

instrument should make it possible to obtain good spectra

with considerably smaller samples than we have been able

to analyze previously with the laser probe. Alternatively,

for quantitative analysis, it will be possible to employ

emulsions providing improved photometric precision at the

expense of poorer sensitivity.

The new spectrograph is equipped with a 1200 groove/mm

grating, giving a reciprocal linear dispersion of about

o 10 A/mm in the first order. The photographic resolution is

o 0.2 A or less over several hundred angstroms, and the reso olution is about 0.1 A at the exit slit for photoelectric

12
Figure 5. High- aperture spectrograph for use with

low-intensity light sources.

measurements. It is expected that this resolution will be

adequate for the relatively weak spectra obtained with the

laser probe.

When any spectrograph is used with a weak light source,

it is essential that the illuminating system transmit light

as efficiently as possible. For use with this spectrograph,

a Cassegrain illuminator is on order, which is designed

to provide considerably better illumination than would be

possible with a simple lens system. This illuminator will

have two modes of operation. For qualitative analysis, the

illuminator will form an image of the source on the entrance

slit of the spectrograph with a magnification near unity. For

quantitative analysis, the illuminator will form an enlarged

image, several centimeters in front of the entrance slit,

which will serve as a virtual source; the image may be

13
diaphragmed at this point if it is desired to select light

from a portion of the discharge. An achromatic lens will

form an enlarged image of the virtual source on the collimator, and the system is designed to give evenly-exposed line

images over several millimeters of the height of the slit, permitting the use of a step filter.

The electronics to go with this instrument are designed

to be used with stable light sources, such as flames and

hollow-cathode lamps, and with pulsed sources, such as the

laser probe. For stable sources, the electronics include

a regulated high-voltage power supply, a phase-sensitive

amplifier, and a strip-chart recorder. Electronics for

pulsed sources will include an amplifier providing for display of intensity vs. time on an oscilloscope, with a time

resolution of about 1 ysec, or, alternatively, displaying

on a meter the intensity integrated over the duration of

the light flash.

The instrumentation described here is now being installed. By the time of the next report in this series,

we hope to have information on the performance of the

equipment

.

B. Study of Plasma Torch

In the last report [3]> we described some preliminary

results of a study of the properties of an inductivelycoupled, radio-frequency, plasma torch. The study of this

source has now been completed, and two publications on this

work [5, 6] should appear shortly.

The detection limits found with this torch were encouraging, particularly the limits in emission for some

of the elements which are difficult to excite in the flame.

For example, the limit of detection in emission (defined

as the concentration in solution at which the signal-to-noise

ratio equals two) was between 0.4 and 1 yg/ml for aluminum,

14
boron, molybdenum, and titanium, as well as for some elements

easily determined in flames, such as silver and calcium.

However, the detection limits by atomic absorption were

considerably poorer in most cases, largely due to the

high background emission by the torch. Hollow-cathode lamps

were employed as the primary sources for the atomic absorption measurements, and it is possible that lower limits of

detection would be possible with brighter primary light

sources, such as electrodeless lamps.

Marked interelement effects were found with the plasma

source, affecting particularly the emission signals. With

one exception, the effects observed were enhancements.

Table 1 lists some of the enhancement factors found, defined

as the ratio of the emission or absorption signals in the

presence of the interfering element to the signals in the

absence of the interfering element. The Ca II line could

not be measured in absorption because of the low intensity

of this line from the hollow cathode lamp, and absorption

measurements with aluminum were obscured by noise.

Table 1. Enhancement factors in emission and absorption

Element, at Wavelength, Added species, Enhancement factor

100 yg/ml A at 100 yg

po

4

3 "

/ml Emi ssion

1.6

Ab sorption

Ca I 4227 1.3

Ca I 4227 Na

+ 2.7 1.0

Ca II 3968 po

4

3 " 7.5

Ag I 3281 Cu2 + 1.3 1.0

Cu I 3248 Ag 1.2 1.0

Al I 3093 Ca

2+

0.7

15
These observations were interpreted as indicating a lack of local thermal equilibrium in the discharge. If the

interelement effects were due to changes in element populations, they should affect emission and absorption signals

equally. Thus, chemical effects can apparently be ruled out.

If there is not local thermal equilibrium, and if most excitation occurs through electron-atom and electron-ion collisions,

the emission signals should increase when the electron concentration is raised by adding an additional element to the

sample. This interpretation explains all of the enhancements

observed, but cannot account for the suppression of aluminum

emission by calcium. It is, however, possible that some

chemical interferences do occur in the plasma torch and

that these are counterbalanced in most cases by the enhancement effect

.

o Figures 6 and 7 show how the Ca I line at 4227 A changes

in intensity with increasing amounts of phosphate and aluminum added. There is relatively little additional enhancement

by phosphate at concentrations above about 100 ug/ml . In

the case of phosphate, it would apparently be possible to

buffer the interference by adding phosphate to all samples,

but this approach would not work in the case of the influence of aluminum on calcium emission.

Although the absorption signals are relatively free

from the interelement effects, the detection limits were not

as good as in emission.

The study was ended when it was concluded that the good

emission sensitivities observed with the plasma torch do not

provide sufficient advantage to counterbalance the severe

interelement effects and the extra cost and difficulty of

operating a plasma torch as compared to a chemical flame.

For those elements which do not provide adequate emission

signals in flames, the plasma jet [7] appears to be a more

convenient light source than the plasma torch.

16
80 r

60 <

20 -

100 200 300 400

P0

4 CONCENTRATION, ppm

500

Figure 6. Effect of phosphate on calcium line

emission in the plasma torch.

240 r

100 200 300

Al CONCENTRATION, ppm

400

Figure "7. Effect of aluminum on calcium line

emission in the plasma torch.

17
C . Test of Program for Calibration of Photographic

Emulsions

The annual report of this Section for 1965-1966 [2, p. 10]

included a description of a computer program for calibration

of photographic emulsions. The program is based on the concept that a function of the transmittance readings could

be found for which a plot of the logarithm of the relative

exposure vs the function of the transmittance would be

linear and could be represented by the equation

log(ER

) = M-f(T) + c, (1)

where E

R is the relative exposure, M is the slope of the line,

f(T) is the linearizing transform of the transmittance, T,

and c is the intercept. Since only relative exposures are

being determined, c can be assigned any convenient value

and only the slope, M, need be determined. In principle, M

could be found from the transmittance values for one pair of

readings of lines of known relative exposure, such as a pair

of readings through a step sector, but in practice the value

of M should be determined by averaging slopes obtained from

several line pairs, thus reducing the influence of random

errors

.

Several transforms were tested for their ability to

give a fit to eq 1, and the Kaiser transform [8] was selected for a more detailed study. This transform has the

form

K = A log(l/T) + (1-A) log(l/T-l), (2)

where T is the transmittance. The constant A may be estimated from an equation given by Kaiser [8], but photometric

errors make a single estimate of A unreliable.

The program KAISER calculates up to 100 values of A,

determines the mean and standard deviation, and compares

each value of A with the mean. Any value of A differing

from the mean by more than three times the standard deviation

18
is rejected, and a new average and standard deviation is

found. Then, for each pair of readings through a step sector

or filter, a value of M is found. The average M and the

standard deviation are found, and again a test is made to

reject any value of M differing from the mean by more than

three times the standard deviation.

The test of the method is to determine whether, under

normal measurement conditions, the Kaiser transform gives

an acceptable fit to eq 1. The fit is not acceptable if

the values of M show a perceptible trend with increasing

blackening of the lines on the plate. The measurement conditions that can affect the fit include the type of emulsion,

the wavelength at which the calibration is made, the spectrograph, and the microphotometer , including possible influences

of scattered light or other optical defects in the microphotometer. We have made tests of the program with five

emulsions exposed on two spectrographs and measured on three

microphotometers ; in the case of one microphotometer, measurements were made with four slit widths, ranging from

about one-tenth to one-half of the width of the entrance

slit of the spectrograph. The data were inspected by plotting M as a function of the percent transmittance of the

light line of the pair used to determine each value of M.

Figure 8 shows a plot of this type for an SA-1 plate

exposed at 3200 A. It is seen that there is no perceptible

trend of the slope with increasing blackening of 'the line,

indicating that the emulsion can be calibrated by means of

the two parameters, A and M. Similar results were obtained

with this emulsion over its entire useful wavelength range,

as well as with type 33, 103-0, and II-P plates. On the

other hand, Figure 9 shows the results obtained with a Q-2

o plate at 3200 A. It is clear that, for this emulsion at

this wavelength, the fit to eq 1 is not satisfactory.

o However, at 2400 A, a good fit to eq 1 is obtained, indicating that the calibration method can be used with Q-2 plates

.19
0.5 1 1 1 1 1 1 1 1

'

1 1

0.4 _ ° -

-

o

O

o o O „ „° BAKER

uj 0.3

0.o

w 0.5

o O

" 00 g^o" SAMPS0N_

0.4 o °

o o o

o

o „ ^

o

° KAISER

0.3

C

6>

1 1

o

1 1

9 oo o

1 1

°o

1

° »V A-0.14

l 1 1

) 20 40 60 80 100 %T, LIGHT STEP

Figure 8. Computed slope as a function of relative intensity of line pair. Data for an SA-1

plate at 3200 S.

1.2

0.8

0.6

b °-4

BAKER- - SAMPSON

1.2 O -

1.0 8 o 0°

o

o

o KAISER A=0.66~

o

o„ 0) °o 0.8 o

o

1 1

Oo

1

o

o

o

o °o °

1

1 1 1 1

1 20 40 60 80 100 %T, LIGHT STEP

Figure 9. Computed slope as a function of relative

intensity of line pair for Q-2 plate at

3200 A.

20
at the short wavelengths where these plates are normally

advantageous

.

The effect of scattered light in the mlcrophotometer

is illustrated in Figure 10, which is a plot of data for an

SA-1 plate measured in another laboratory. The microphotometer had approximately 0.5% scattered light. As a result,

readings below about 10$ T are affected by enough to give

erroneous values for M. In this case, the emulsion calibration method is applicable only for lines having transmittance

values above about 10$. The program includes provision for

restricting the range of transmittance values for which the

calibration is made, as is needed in an individual case.

0.7

0.6

UJ

_iCO

r» a.

%T, DARK

1 5

STEP

10 15 20

Mill

o o°

°o

°o°

1 1

o

1

o °a> °o °_

1 1

6

°o

o

o

1 1 °°o°° *

1 1

° o o oo

° ° °9 oo

1 „ I8-?

20 40 60

%T. LIGHT STEP

80 100

Figure 10. Effect of scattered light in mlcrophotometer on linearity of plate calibration

with Kaiser transform.

These studies have demonstrated that the method of

plate calibration developed here is applicable for most

emulsions under the measurement conditions we employ. The

method is well adapted to a digital computer. In addition,

the output of the program provides information to indicate

why the method fails, if it does. Data such as are shown in

Figure 10 provide evidence for scattered light in the microphotometer. A plot similar to Figure 9 will be obtained if

the microphotometer is not in focus; thus, if such data are

obtained for an emulsion for which earlier measurements had

21
indicated a good fit to eq 1, attention is drawn to the

cause and steps may be taken to correct the cause of the

error

.

The use of a time-shared computer for emulsion calibration and conversion of transmittance readings to relative

intensities has been found to save considerable time. For

example, in a recent series of analyses, measurements were

made for line and background transmittance values for 15

lines and the emulsion was calibrated in 5 wavelength regions. There were 10 exposures on each plate, so that

measurements on the microphotometer included 150 readings

of line transmittance, 150 readings of background transmittance, plus calibration data for 5 wavelength regions. Typically, calibration of the emulsion and conversion of readings to 150 relative intensities, corrected for background

and step, required about one-half hour, considerably less

than would be needed by graphical luethods .

D. Applications to Analysis

In addition to the research activities described in

this report, the facilities of the Sjpectrochemical Analysis

Section are employed for a considerable number of other

analytical applications. For the period June 1967 through

May 1968 analyses were performed by emission spectroscopy

involving 266 samples, 14,598 determinations, and 15^

reports

.

1. Standard Reference Materials

A continuing important role of the Section is in the

testing for acceptance and analyses for certification of

Standard Reference Materials. Nearly all of the materials,

including those not directly applicable as spectrochemical

standards, are subjected to general qualitative or semiqualitative analysis. This procedure verifies the aim

composition of a given material as well as indicating unexpected elements introduced in the manufacturing process.

22
Typical samples analyzed in the past year were metallo-organic compounds, botanical material, steels, irons , highpurity zinc, glasses, and various ferrous alloys.

Following this general type of analysis, the intended

Standard Reference Materials are tested for homogeneity.

Every effort is made to secure samples of these materials

which can be analyzed directly on the photoelectric emission

or x-ray fluorescence spectrometers. For example, samples

from steels or irons intended as chemical SRM's are selected

prior to the chipping process. A typical steel as received

from the producer would generally be in the form of bars 8 in

in diameter by 30 in. long with up to fifteen bars per

heat. Slices from both ends of each bar are obtained, and

analyses are made on these slices to determine the homogeneity of the individual bars and of the entire heat. 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.

Materials intended as standards for spectrochemical

analysis are usually provided in either ingot form or chill

cast slab form. Ingots up to one ton are sampled at selected

points and tested for homogeneity prior to rolling to finished size. Preparation and testing of the chill cast standards have been described elsewhere [9]. Homogeneity data

are usually generated on either the emission or x-ray

fluorescence spectrometer, and the digitized readout provided

is applicable for direct input to computers. Depending on

the volume of data and speed required, the central computer

facilities at NBS or the time-sharing computer is used.

Applications of the time-sharing computer have been described

in previous progress reports [2,3]- Spectrochemical

Standard Reference Materials tested for homogeneity this

past year include Cast Steels, Ductile Iron, High Temperature

Alloys, Tin-lead Solders, Stainless Steel, and Electronic

Nickel Alloys

.

23
In addition to homogeneity testing, we also participate

in the quantitative analyses required for certification of

Standard Reference Materials. Analyses by at least two

independant methods within our Section along with other

analyses made at NBS and by cooperators in industry provide for the provisional and final certification.

An illustration of the overall planning, cooperative

homogeneity testing, and analysis for certification is given

for two cast steel Standard Reference Materials. At the

request of the Steel Pounders Society of America, two

compositions of cast steel were prepared and cast at the

American Cast Iron Pipe Co., Birmingham, Ala. with use of

the NBS chill cast mold assembly. Homogeneity testing was

performed by our Section, the Research Laboratories of General

Motors Corp., and ten member foundries of the Steel Founders

Society, and the material was found to be satisfactory.

Subsequent analyses for chemical certification were made by

our Section, other groups at NBS, and five member foundries

of the Steel Founders Society. As a result, two new Standard

Reference Materials useful for spectrochemical analysis of

cast steel are being issued. A similar program for ductile

iron has provided three needed standards for this material.

Copies of the provisional certificates for these standards

are included in the Appendix to this report.

2 . Other Analyse s The Analytical Chemistry Division performs numerous

analyses for other groups at NBS and for other government

agencies. Whenever possible, this work is done in the

Spectrochemical Analysis Section in order to take advantage

of the speed and efficiency of routine spectrochemical

analysis. This work ranges from qualitative to quantitative

analyses depending on the nature of the sample and the

specific requirements.

24
A typical application of quantitative analyses would

be the specification testing of failed aircraft parts.

Three parts of an aircraft landing structure were submitted for analyses with the information that two of the

parts were good and one had failed. Spectrochemical

analyses revealed that the good parts were medium alloy

steel and within specification, while the failed part was

plain carbon steel.

Another application involved the analyses of tin

liners in copper pipe used in a distilled water system at

NBS . The specifications required that the impurity content

of the tin could not exceed 0.10$. Several lots of the

fabricated pipe supplied by the contractor were rejected,

on the basis of the spectrochemical analysis, before acceptable material was finally installed.

Qualitative and semi-quantitative analyses of corrosion

products, dust, powders, liquids, and other miscellaneous

samples are often performed. Semi-quantitative analysis

by the gallium oxide powder dc-arc technique of metallic

impurities imbedded in plastic bottles revealed the source

of contamination of liquids stored within the bottles. A

qualitative analysis of dust fallout showed that the dust

in our own laboratories originated largely from a slotted

steel beam and insulating material in the ceilings.

Many other similar applications of analyses, too

numerous to mention here, were made during the past year,

principally through the able work of Mrs. V. C. Stewart,

Mrs. M. M. Darr, and Mr. D. M. Bouchette

.

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

25
3. ELECTRON PROBE MICROANALYSIS

A. Basic Considerations

This year's activities were intended to provide a balance among theory, technique of measurement, and applications.

In the area of theory, we investigated the sources of error

in quantitative procedures in order to establish priorities

for subjects of further research. Technique and instrumentation were improved mainly in three areas: (1) the use of

a matrix scanning device [3] for homogeneity studies and

other objectives, (2) non-diffractive analysis by means of a

lithium-drifted silicon detector, and (3) combining several

x-ray (or electron) area scans in a color composite for

better representation of spatial relations. The studies of

x-ray mass attenuation coefficients were continued, and the

construction of the alloy quenching device [3] was completed.

Studies of applications include the investigation of homogeneity of standards for microanalysis, and the preparation

and analysis of biological specimens.

B. Techniques and Instrumentation

1 . Matrix Scanner

The interfacing system for automatic grid scans [3» P-3^]

(henceforth called matrix scanner) was installed (Figure 11)

and fully tested. The system is composed of the following

parts : a. Timer-sealers . There are six of these

convertible to either time or scaler.

b. Matrix-generator . This device generates a

one or two dimensional matrix of variable dimensions, with a maximum size of 100 x 100 positions. This device advances

one position in one dimension (the line) after completion of

an x-ray signal counting interval. After the line is completed, the device advances to the first position of the next

26
• # t # #

Figure 11. Device for digital matrix scanning.

line. D-c outputs proportional to the number of line and the

position along the line are provided. By connecting these

voltages to the electron beam scanner, the electron beam

can be moved on the specimen surface forming a raster that

images the matrix. The distances between positions can be

varied over a very wide range.

c. Scan Control . This determines how many sealertimers are to be read, and how many times the matrix scan

is to be repeated in an automatic scan.

27
d. Print-Out Control. This determines if the

advance and print-out of the timer-sealers is automatic or

manual, and permits two forms of print-out.

e. Paper Punch . This permits fast punching of the

results into paper tape, in ASCII code. The tapes thus

generated can be printed by teletypewriter (Figure 12), or

directly processed by a computer.

APRIL 11, SCAN 4

BIOLOGICAL STANDARD EMB 31

FE S NA TARGET TIME TALLY

CURRENT

000002 000002 000006 000001 000200 000001

000507 000228 000135 028496 0002430 000002

000545 000215 000167 029935 000200 000003

000561 000244 000119 029870 000200 000004

000577 000249 000115 029826 000200 000005

000583 000235 000121 029787 000200 000006

000600 000253 000136 029750 000200 000007

Figure 12. Example of matrix scanner print-out.

The timer-sealers register time, pulse information from

x-ray channels, (diffractive or non-diffractive) , or digitized

currents (target or monitor current). They can also be used

as talliers, counting the position of a read-out within the

matrix, or for sampling. In this last mode, a short counting

period (e.g. 20 sec) is repeated after long periods (e.g.

every 400 sec) .

28
In a typical operation, the matrix positions correspond

to positions upon the specimen. A one-dimensional matrix

is used for a line scan, and a two-dimensional matrix for an

area scan. The length of a counting period can be constant

(fixed time mode), or it can be determined by a signal level

in a scaler; hence, ratios of x-ray counts can also be registered.

Instead of using the matrix output to shift the electron

beam, the device can also be used to register signal variations as a function of time, or of any variable connected

with time. For instance, fixed-time periods of counting can

be used, and the results punched onto tape, while the wavelength position of one or more spectrometers is advanced

slowly

.

This device can be used advantageously whenever a great

number of measurements must be made. In our laboratory, it

was employed for the analysis of diffusion couples, inclusions in alloys, and biological specimens. The main area of

application is in the determination of homogeneity of alloys

used as standard reference materials . A comprehensive computer program, which provides for drift compensation and

gives topographic information (Figure 13), as well as statistical evaluation is presently being tested. Mr. S.

Rasberry has provided great assistance on the computation

problems encountered in the course of our work.

2 . Lithium-drifted Silicon Detector

As mentioned in previous reports [2, p. 60; 3, p. 31],

non-diffractive (non-dispersive) spectrometry by pulse-height

analysis offers the advantages of (1) a very quick, although

low-resolution, spectral scan, and (2) of the absence of defocusing when the electron beam is deflected from its central

position. The advantages of a flow-proportional counter in

o the soft region (5-50 A) were illustrated in last year's report. A solid-state silicon detector, installed during the

29
TAPE H-5 10X10X2X2 20AU 8oA<S AT 20KV L^AD eMO

>

ABSOLUTE TOPOGRAPH

ELEMENT 1« AG LA ELEMENT 2* AU LA

• —

•

t

t -

• G

•

• G

iG

0000

• : : - -. •

•f - +

:

+ - -.

- -,

• + • + - • - - + + +

:--++•

-

• • •

• • •

KEY

go:, -2«0 -1,0 -,50 -,20 +,20 +#5Q +1,0 +2,0

BLANK - • m

Figure 13 • Section of computer output for homogeneity

testing.

current fiscal year, complements the flow-proportional

counter. The useful wavelength range of the silicon detector

(the photon energy must be above 1 keV) overlaps that of the

proportional counter. The resolution of the silicon detector

(in the order of 600 keV half-width) is far superior to that

of the gas detectors (except for the low energy extreme of

the observable range); the pulse-height is very stable, and

high counting rates (up to 5 x 10 counts/sec) can be observed.

A moderate disadvantage of this detector is the need for

constant cooling to liquid nitrogen temperature (Figure 14).

Since defocusing effects and count-rate limitations

limit the usefulness of the matrix scanner, it is expected

that combination of the latter with the silicon detector will

30
Figure 14. Non-diffractive silicon detector

mounted on electron probe microanalyzer. (A) solid state detector,

and (B) preamplifier.

be particularly useful. Examples of spectra obtained with

the detector are shown in Figures 15 and 16. A more complete study of the detector is presently under way.

3 • Color Composites for Area Scanning

Color photography has been used in several instances to

combine x-ray area scans of several elements in one image.

This simplifies the interpretation of area scans, since

the topographic interrelations of concentrations of the

elements involved appear more clearly.

This technique was studied in detail, in cooperation

with H. Yakowitz (Metallurgy Division), in order to compare

various techniques of color registration, and to establish

working rules for applying color mixing to x-ray area scans.

31
Figure 15- Diffractive spectra of a 60 gold - 40 silver alloy. (Upper spectrum,

ADP crystal; lower spectrum, LiP

crystal)

.

It was found that color composites combining the information for up to three x-ray area scans can be prepared

most efficiently by copying on color film the partial blackand-white exposures, and using a different color filter for

each exposure. A simple jig can be used to achieve satisfactory superposition of the partial images. The technique

and several applications will be published [10].

C . Quantitative Electron Probe Microanalysis

1 . X-ray Mass Attenuation Coefficients

Experimental measurements of the mass attenuation coefficients of 15 elements were performed in the region from

o 0.5 to 8.3 A, using a modified x-ray fluorescence spectrograph. The measurements were performed on foils. The characteristic, lines were obtained by inserting, in the specimen

position of the spectrograph, pure elements or in some cases

32
\ i i i i i i i i r

Au

J I I I I I I L

•Figure 16. Non-diffractive spectra of Ag, Au, and

a 60 Au - 40 Ag alloy.

33
simple compounds. The absorbers were inserted between the

first collimator and the analyzing crystal.

In most regions the values obtained check with the observations of previous investigators , as well as with our

previous interpolations [11] within 2-h%. Hence, in these

regions we can consider the mass absorption coefficients

sufficiently well known for the purposes of quantitative

electron probe microanalysis. However, towards longer

wavelengths, discrepancies among published values increase,

and the accuracy of measurements is limited by the availability of thin foils. Studies of preparation of thin foils are

presently under way. This work was ably performed by Dr.

P. K. Hon.

2 . Study of Uncertainty in Corrections for

Quantitative Analysis

The results of these studies of the absorption and

fluorescence corrections are now published [12, 13]. Similar

studies were extended to the atomic number correction; we

expect to publish the results during next fiscal year. The

main conclusions of these studies are:

1. In order to minimize serious errors due to the

absorption correction, it is advisable to work at relatively

low energies, and with high x-ray emergence angles. There

is no serious objection to this from the point of view of

the atomic number or fluorescence corrections . 2. Since the so-called atomic number correction

is affected by the atomic number-to-atomic mass ratio, this

correction is frequently not negligible for elements not too

far apart in the periodic table. The uncertainty in the

values of the mean excitation energy for low atomic number

elements causes serious uncertainties in the analysis of

oxides, carbides, and similar compounds, even when the

heavier element is determined.

34
3. Although the uncertainties discussed above may

be reduced by careful analysis of well-characterized standards, their effects, in conjunction with the absorption

correction uncertainties and the chemical effects on x-ray

emission seem to preclude the possibility of accurate quantitative determination of elements of atomic number below 10,

unless standards closely matching the specimen are available.

3. Standard Reference Material Measurements

An extensive search for well-characterized materials

which would be of use in testing the theory of quantitative

analysis resulted in the gathering of several dozens of

materials of unquestionable usefulness . Careful measurements

over a wide range of experimental conditions will be performed

within the next fiscal year, and they will be published together with complete documentation of the characterization.

Some of these materials (including a series of copper-gold

alloys and one of silver-gold alloys) will be available as

certified standard reference materials . Some others will be

available on loan to requesters . The results of these measurements will be used to test the efficiency of current

procedures for data reduction.

4

.

Proceedings of a Seminar on Quantitative

Electron Probe Microanalysis

On the o.ccasion of the Seminar on quantitative electron

probe microanalysis mentioned in the 1967 report [3], a

series of papers concerning diverse aspects of quantitative

microprobe analysis were obtained from various participants.

These papers have been issued in hard-cover book form under

the title: "Quantitative Electron Probe Microanalysis", NBS

Special Publication 298, August 1968. The volume contains the

following contributions:

Introduction

L. S. Birks , Naval Research Laboratory, Washington, D. C.

35
Quantitative Electron Probe Microanalysis. A Progress

Report

K. F. J. Heinrich, NBS , Washington, D. C.

Some Problems with Quantitative Electron Probe Microanalysis

J. Philibert and R. Tixier, Research Institute of the

French Ferrous Metallurgy (IRSID), St. Germain-en-Laye,

France

.

The Theory of Quantitative Electron Probe Microanalysis

I. B. Borovskii, and V. I. Rydnik, Institute of Metallurgy, USSR Academy of Sciences, Moscow.

On the Structure of Formulas for Quantitative Analysis

J. Criss, Naval Research Laboratory, Washington, D. C.

Computational Methods for X-ray Emission from Targets Excited by Electrons

D. B. Brown, University of Southern California, Los

Angeles, California. (Now with Naval Research Lab.)

The Choice of Models for Electron Scattering and Deceleration for Electron Probe Microanalysis

T. Mulvey, University of Aston in Birmingham, England.

Progress in the Correction for the Atomic Number Effect

D. M. Poole, Atomic Energy Research Establishment,

Harwell, Didcot, Berkshire, England.

The Calculation of Stopping Power and Backscatter Effects

in Electron Probe Microanalysis

P. Duncumb, Tube Investments Research Laboratories,

Saffron Walden, England, and S. J. B. Reed, Mineralogy

Department, British Museum, London.

Scattering of Electrons in Metallic Targets

K. Murata, R. Shimizu, and G. Shinoda, Osaka University,

Higashinoda, Miyakojima, Osaka, Japan.

36
Absorption Edge Effects in Electron Probe Analysis

D. Nagel and J. Criss, Naval Research Laboratory,

Washington, D. C.

Fluorescence Excited by the Continuum

J. Henoc, National Center for Studies of Telecommunication, Moulineaux, France.

Quantitative Evaluation Methods for Alloy Microstructures

by Microprobe Analysis

G. Dtirfler, Analytical Institute, University of Vienna,

Austria.

Some Aspects of the Microprobe Analysis of Biological

Specimens

T. Hall, Cavendish Laboratory, Cambridge, England.

5 . Literature Research

Work on the bibliography has continued but was slowed

down by changes in personnel and by the work connected with

the Seminar described above.

K. F. J. Heinrich

37
4. X-RAY FLUORESCENCE SPECTROMETRY

Improvements in instrumentation, methods, and computing

software have made possible more precise and accurate measurements, benefitting our research program as well as the

NBS Standard Reference Materials (SRM) programs . Research

into improved methods of calibration and correction techniques

for interelement interferences has continued and will soon be

applied to the analysis of high-temperature alloys and nickelbase electronic alloys.

Much of 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 has

been provided through homogeneity testing, specimen sorting,

and rapid verification of composition of labeled specimens.

A. Modification of Equipment

The Spectrochemical Analysis Section is equipped with

a single-channel x-ray fluorescence spectrometer (the

Norelco Four Specimen Vacuum Spectrometer) and a multichannel x-ray fluorescence spectrometer (the Applied Research

Laboratories, Inc., PXQ). These instruments were described

earlier [1, pp. 30-34].

The single-channel instrument is of modular design and

has been improved by replacement of the entire signal processing and counting electronics. The first phase of this

change-over, including installation of a new scaler, timer,

ratemeter, and detector high voltage power supply, (all

Hamner Electronics, of AEC-NIM compatible type), was completed one year ago [3 rf p. 46]. During the past year the

scintillation detector and preamplifier, flow detector preamplifier, linear amplifier, and pulse height analyzer were

replaced. See Figure 17- The purpose of this replacement,

using solid-state signal processing electronics, was to

38
y*

0-' 0-' 0-" 0-" & 0-"

- © mi

m <m m

m

-« <tt

s

%i

1 . . 1 Kir

ZF»« $L'«*»'$!i3>< m. v y x / * <0

, '¥L SI8NJIL C0*4TMff UUCIONWVt """"' oQ*-^- * -

O

DATA SCANNER

S-2328

COUNT PfOMf

IDENTIFICATION NUMBER

MfTOtMTIC

tttflUAL If

AUTOMATIC

MANUAL #

I

rTM^

SERIAL NUMBER

RESET ^ N»

«

Figure 17. X-ray fluorescence analog and digital

signal processing electronics. (The

lower panel interfaces the digital electronics to a teletypewriter and paper tape

perforator.

)

eliminate difficulties with noise and excessive dead-time

at the preamplifiers and to eliminate problems of noise and

drift at the linear amplifier and pulse height analyzer.

The performance of the new equipment has been very satisfactory and no malfunction has occurred since installation.

During more than 80$ of the past year the single-channel

spectrometer has been operated on a 40 hours per week basis.

An interface unit (the Hamner Data Scanner) was added

last July to link the scaler and timer of the single-channel

spectrometer to a teletype printer and tape punch. This

system permits automatic data logging in a form (paper tape)

which is computer- compatible . Figure 18 illustrates the

39
format of output of this device; data tapes such as this one

have been processed both on the GE-265 time-sharing computer

and on the UNIVAC 1108 computer.

2-16-68 DET OF MN KA IN CAST STEEL

AND DUCTILE IRON.

0001 1178 301990 010000

0002 1174 075850 010000

0003 1176 226139 010000

0004 1177 146695 010000

0005 1178 299408 010000

0006 1179 234217 010000

0007 1180 386691 010000

Figure 18. Teletypewriter print-out produced by

digital interface. (The columns, from

left to right, are: serial number,

specimen number, number of counts,

and time in hundredths of a second.)

Plans for future changes in the single-channel spectometer include a light element conversion for the flow

proportional detector. This conversion will consist of installation of a deburred collimator and polypropylene window

in order to improve our capability for determining sodium,

magnesium, aluminum, and silicon.

The valuable assistance of Mr. A. M. McDermott of the

NBS Electronic Instrumentation Section in the installation of

new electronics is gratefully acknowledged.

B. Research Activities

The manuscript "X-Ray Fluorescence Analysis of Silver

Dental Alloys with Correction for a Line Interference" was

published [14].

A brief description of our research into the interelement interference problems in x-ray fluorescence analysis was

given earlier [3, pp 45, 48]. This work is continuing and

will be applied to the analysis of five projected high40
temperature alloy and nickel-base electronic alloy SRM's.

As a part of this study the computing portion of a rather flexible computing program, IEMAT, has been completed and is now

ready for testing. This program will allow comparison of the

Lucas-Tooth technique with other similar empirical correction

techniques by application to common sets of data. Input-output

sections and documentation for IEMAT are yet to be developed.

Several programs used in x-ray fluorescence analysis

are listed in Table 2 according to the function of the

program. The programs which are written in the BASIC language for the GE-265 computer have been documented and were

recently issued in a Technical Note [4].

Table 2. Programs used in x-ray fluorescence analysis.

Function of program Program name

GE-265

(BASIC)

UNIVAC 1108

(FORTRAN V)

Homogeneity testing

including analysis of

variance

Analytical calibration

(No interelement effects

accounted for)

XRAY1 CODEAV

(Mofified for paper

tape data entry)

CFIT2 ORTHO

(Called through

OMNITAB)

Analytical calibration

(Interelement effects

accounted for)

IEMAT'

Frequency distribution

and time-trend analysis

Plating thickness calibration,

analysis and report

generation

Generally applicable data

loading, sorting, writing

and statistical programs

FREDIS

PLATE

1

PLATE2

STAT PTLOAD

SORT CPUNCH

COLS 8 MTPRNT

WRITE GRAFIC

PLOT

Still under development and testing

41
C . Examples of Applications

X-ray fluorescence spectrometry has been applied to the

analysis of a wide variety of materials this year. The range

of materials is illustrated by considering the types characterized for the SRM program; these have included white cast

iron, glass, transformer steel, ferrosilicon powder, cast

steel, ductile iron, high temperature alloys, and electronic

and magnetic alloys.

An example of effective analytical support to the production of an SRM is given by the data in Table 3« In this

example inhomogeneity was observed for Mn in a batch of ferrosilicon powder received at NBS and intended to be SRM 59aTable 3- X-ray fluorescence determinations of

manganese in ferrosilicon powder.

(Mn, in percent)

9/1/67

Date and treatment

2/7/68' 3/15/68 ; 3/22/68

Sieved at 100 No further

mesh and twice treatment

.

mixed in a Final homoCan shaken motorized mixer geneity

Position As received. for 8 hrs. for 1/2 hr. study

.

Top 0.62 0.6 0.79 0-79

5

Middle 0.73 0.8 0.80 0.79

5

Bottom 1.12 1.1 0.81 0.80,,

Error Q.01 0.005

These intermediate tests were made only to determine if a

full test of homogeneity was warranted as a result of the

treatment; because of the limited nature of the data, no

error analysis was made.

Two times the standard deviation of the mean of four determinations.

Two times the standard deviation of the mean of five determinations .

42
A series of treatments was set up by the SRM office to improve the homogeneity. Redetermination of homogeneity immediately following each treatment, provided systematic reports on the status of the material and indicated a point for

termination of the treatments

.

An interesting observation concerning specimen surface

preparation arose in the analysis of cast steel SRM 1138,

1138a, 1139, and 1139a and ductile iron SRM 1140, 1140a,

Il4l, ll4la, 1142, 1142a. In these specimens manganese,

silicon, copper, nickel, chromium, vanadium, molybdenum,

titanium, and arsenic were determine relative to previously

certified SRM's of similar type. The surfaces of the

specimens and standards were prepared by polishing on

successively finer silicon carbide paper, through 600-mesh

grit. Polishing was completed with a 6-um diamond finish.

Our initial assumption was that the material was hard enough

so that grinding with silicon carbide would not affect the

determination of silicon because of imbedding. Data from

independent analyses have supported this assumption in the

case of the ductile iron specimens; however, for the cast

steel specimens, x-ray fluorescence consistently yielded a

higher value than other methods (approximately 15$ higher in

the case of 1138 and 1138a). The specimens and standards were

repolished with aluminum oxide papers and aluminum oxide

slurry for finishing. Results for analyses following the

two preparation methods are given in Table 4. The values

obtained with the aluminum oxide method are in close agreement with independent determinations, lending support to the

conclusion that this method is more accurate. Reexamination

of the physical properties of these materials confirms that

1138 and 1138a is unusually soft (untypical of normal cast

steel hardness) and this may be the cause of the silicon

contamination

.

43
Table 4. X-ray fluorescence determinations of

silicon in cast steel.

(Si, in percent)

Preparation method

Specimen

1138

1138a

1139

1139a

2x(Std. Dev.)

2x(Std. Dev.)

Silicon

carbide A

Aluminum , oxide B

0.42

0.30

0.014

0.36

0.25

0.014

0.88

0.82

0.026

0.84

0.80

0.026

Method A, polishing with 600-mesh silicon carbide

paper followed by a 6-um diamond finish.

Method B, repolishing with aluminum oxide papers

followed by aluminum oxide slurry.

Valuable contributions to the analyses mentioned in this

section have been made by the following personnel: Martha M.

Darr assisted in the analyses of cast steel and ductile iron

SRM's, Doward M. Bouchette has performed quantitative analyses and tests of homogeneity, Chong K. Kim performed the

initial tests of glass homogeneity, Clarence W. Gifford

assisted in the homogeneity testing of ferrosilicon powder,

and James L. Izlar assisted in specimen identification and

label checking by x-ray methods

.

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 as discussed in an earlier report [3].

S. D. Rasberry

44
5. SPARK SOURCE MASS SPECTROMETRY

Efforts during the past year with the spark source

mass spectrometer have contributed to better understanding

of the factors affecting accuracy of analysis and means of

improving analytical techniques. Studies of the uniformity

of sensitivity of the photographic plate, used as detector,

have indicated that this is an area that can have significant

effect on the accuracy of analysis. In methods development,

stable isotopic dilution analysis has been extended to the

determination of elements at very low concentrations, for

example, tin at 20 ppb* in zinc. This sensitive technique

has been applied to the certification of impurities in two

zinc standards (SRM 728, 683) and a platinum standard (SRM

681), all three of which contain levels of impurities that

would make them useful standards for spark source work. Several computer programs have been written to improve the speed

and accuracy of analysis and to compare the usefulness of sev- eral different plate calibration functions and modifications

thereof. Emphasis has been placed on working with materials

that can serve as standards for the spark source mass spectrometer .

A . Instrument Improvements

Magnetic shim stocks 0.003 in. thick inserted behind

the ion sensitive plates have been used in the plate holders

in order to decrease certain types of plate background.

This shim has been quite effective in lowering background;

however, the attraction of the magnetic material to the pole

faces of the magnet results in a force that bows the plate

toward the magnet. This displacement, which occurs on the

two ends of the plate and in the center between the two hold

down tabs, apparently varies as the plate is racked

* In this report ppb indicates parts per billion by weight

(ng/g) and ppm indicates parts per million by weight (yg/g)

45
from exposure to exposure. This change in displacement results in variation of position of the plate with respect to

the magnet face. Line position and focus are dependent on

plate position and the effects are largest at the low mass

and smallest at the high mass ends of the plate. The combined effects have been to yield plates having lines at midposition and low position displaced with exposure position,

and with the low mass lines at somewhat less than optimum

focus . Modifications were made to the plate holders to

overcome these problems . Figure 19 shows at the top the

original plate holder design for our instrument (C.E.C. Model

21-110). The bottom plate holder shows the extra pair of tabs

Figure 19 . Plate holders for mass spectrograph.

(Top, original plate holder; bottom,

plate holder with magnetic shim and

t ab s . )

added to the center of the plate holder and the tab added to

the low mass end of the holder. These tabs prevent the plate

from uncontrolled bowing and with these modifications the

46
previously mentioned symptoms have disappeared. With four

hold-down tabs instead of the previous two we can now have

a controlled bend in the plates to obtain better focus

.

Previous focusing experiments have indicated that a bend in

the plate would be required to obtain optimum focus at the

low mass end of the plate.

P. J. Paulsen, D. E. Kelleher

B . Homogeneity of Ion Sensitive Emulsions and Precision

of Ion Beam Measurements

1

.

Introduction

The precision and accuracy with which the chemical analysis of materials can be made by mass spectrometry is determined by (1) the precision with which mass analyzed ion beams

can be measured, (2) the accuracy with which ion beam ratios

can be measured, and (3) the precision and accuracy of the

numerical information on the degree by which the ion sample,

presented to the mass spectrometer detector, represents the

composition of the solid sample.

In spark source mass spectrometric analysis of solids,

particularly for trace quantities, these precision and accuracy problems take the following form. In the ion beam

measurement, it is the precision with which this can be done

photographically. The ion beam ratio measurement is a combination electrical and photographic problem. The degree of

representation is determine by measurements with standard

samples

.

2. Method

To determine the precision achievable in the photographic measure of an ion beam, a series of replicate exposures was made in which the successive mass spectra covered

nearly the full 5-cm width and extended over a 15-cm length

of the Q-2 emulsion.

M7
The major component rather than a minor component of a

solid sample should be recorded in the replicate exposures.

This circumvents fluctuations that might be caused by sample

inhomogeneities and/or variations in degree of representation of the specimen composition by the ion sample.

Platinum is a very suitable material for these replicate

tests. By utilizing the low abundance isotopes of mass 190

and 192, the exposure -- an electrical measurement of charge

at the monitor electrode -- can be replicated with greater

precision than with an element that had no low abundance

isotopes. Other desirable properties of platinum will be

indicated in the section on results

.

The Q-2 emulsion measure of the platinum ions is made

by integrating [2, p. 62] the ion intensity profile of the

mass line in question.

3 . Results

Table 5 presents representative data from 21 replicate

exposures made at a given value of the magnetic field, by

racking the plate holder in the usual way. N derived from

the above integration represents the number of singly charged

+ 2 ions of the platinum isotope of mass 190. N represents

the number of doubly charged ions of the same platinum

+ 1 + 2 isotope. N + N is a good approximation of the total number of platinum ions to the Q-2 detector since the ions of

+1 +1 +2 charge greater than +2 are negligible. N /(N +N ) gives

the fraction of the total represented by N . The average

value for N has a relative standard deviation of 4.3% and

that for N

+1

+N is 4.6%. This indicates that the fluctuations

+2 +1 in N do not compensate those in N . Moreover, the fraction

of the total represented by N is a nearly constant one -- 0.90 with 1.3% relative standard deviation. Consequently,

N /0.90 is an adequate measure of the total ionization and

the precision in the N

' average is an adequate measure of

the precision with which the total ionization is known.

48
Table 5- Ion beam measurements on 21 replicate mass spectra

+ 1 + 2

of platinum. (N and N represent the

singly and doubly charged ions)

Exposure No. N

+1

1 1590

2 1482

3 1490

4 1515

5 1525

6 1460

7 1485

8 1425

9 1483

10 1409

11 1444

12 1442

13 1486

14 1375

15 1435

16 1366

17 1348

18 1417

19 1475

20 1490

21 1585

Average 1464

Std. Dev. 4.3$

N

+2

N

+1

+N

+2

N

+1/(N+1

+N

+2

)

205 1795 0.886

198 1680 .882

187 1677 .889

171 1686 .898

236 1761 .865

171 1631 .894

185 1670 .889

163 1588 .897

163 1646 .902

155 1564 .900

156 1600 .902

154 1596 .904

145 1631 .910

151 1526 .900

153 1588 .904

164 1530 .892

166 1514 .890

160 1577 .897

165 1640 .899

146 1636 • 911

142 1727 .918

168 1632 .896

13.6$ k.6% 1-.3*

49
Data like that of Table 5 reveal the widthwise homogeneity of the Q-2 emulsion but tell nothing about how the

emulsion sensitivity may vary lengthwise on the plate. This

was investigated with replicate exposures made at different

values of the magnetic field. Three typical plates are

represented in the three-dimensional drawing of Figure 20 in

which a 5- by 16-cm emulsion is portrayed. At each of the

12 magnetic field settings, 12 replicate spectra were recorded widthwise by racking the plate in the usual manner.

Each of these spectra is suggested by a single short line on

the emulsion in the XZ plane.

INTENSITY l92 Pt

+l/EXPOSURE

(NORMALIZED)

H INCREASING -

153 D

9 II 13 15 j i i i i i i i s s s s y s ssssssss

s/s/ssss/ssss SSS-SSSSSSS-S

/ S S SS/SSSSS

cm

Figure 20

.

Ion beam measurements on platinum mass

lines. (Replicate spectra extending

widthwise and lengthwise on Q-2 ion

sensitive emulsions.)

These curves delineate averages made as follows . In

the lengthwise ones all the data at each racking position

were averaged. In the widthwise curves, all the data at

each magnetic field were averaged. The individual curves

50
do not seriously disagree with the average curves for a

particular plate.

For plate 153D, the emulsion measure of the ion beam

is quite constant both lengthwise and widthwise. Plate l4E

shows a 20$ trend lengthwise and a 30$ trend widthwise.

Plate 15E shows a trend of about 10$ widthwise but a large

overall change of 60$ lengthwise.

The ZY curves clearly show the widthwise variation in

the emulsion sensitivity. The XY curves are not so easily

interpreted. When the magnetic field is increased, the

length of the trajectory of the platinum (+1) ions is decreased. Consequently, the Z axis spread — the ion spreading

by radial projection in the unfocused direction — decreases,

2 and the number of ions/cm producing the mass line increases.

Thus, the emulsion measure of the ion beam is determined by

two factors, the Z axis spread factor which increases with

magnetic field, and the emulsion sensitivity factor, for which

the lengthwise variation is not predictable.

The Z axis spread factor F can be experimentally measured by recording replicate spectra at several values of magnetic field, and then, after reversing the Q-2 plate in its

holder, recording a second set of replicates. Thus, in one

set of replicates, the factor F increases to the right of the

reference end of the plate whereas in the other set, F decreases . Tests of this sort indicate that, for the spark source

mass spectrograph being used (21-110), this Z axis spread

factor F amounts to about 20$ over a 20-cm length of ion

sensitive plate, the standard plate being 38 cm long in this

instrument

.

4 . Circumvention of Inhomogeneities in Ion Sensitive

Emulsions

When samples are being compared, their spectra can be

interspersed to neutralize widthwise variations in emulsion

51
sensitivity. When a conventional graded series of exposures

is being made, the exposures can be interspersed with replicate

spectra of platinum to determine the magnitude of the correction factor introduced by a widthwise inhomogeneity

.

Lengthwise inhomogeneities can be offset by measuring

the Z axis spread factor for the spark source mass spectrometer being used, and then recording appropriate replicate

spectra on the plate containing the spectra of the sample

under analysis.

5 . Summary and Interpretation of Results

a. The total number of platinum ions to the plate

and the precision of this quantity can be derived from measurements on the isotopic mass line of the singly charged ion

of mass 190.

b. Tests with Q-2 plates from different lots indicate that the sensitivity fluctuations about an average

may be <_ 5% standard deviation in a 5-cm length, or there may

be as much as a 30% change in sensitivity over this distance.

c. Techniques for circumventing emulsion inhomogeneities may be effective.

A. J. Ahearn

C . Stable Isotopic Dilution Analysis of Pure Materials

Using Preconcentration Techniques

1 . Zinc

The stable isotopic dilution analysis of NBS zinc composition standards SRM 683 and SRM 728 for Pb, Tl, and Cd

reported previously [3] has been extended to the determination of Sn, Ag, and Cu in the same material. The combined

use of preconcentration techniques and measurement of isotopic ratios by a spark source mass spectrograph has enabled us

to determine 20 ppb of tin in these samples. The relatively

constant detection sensitivity of all elements by spark

52
sources would predict a similar low detection level to any

element amenable to analysis by stable isotopic dilution.

The other elements determined in these zinc samples in fact

gave signal intensities that indicated that they too could

have been determined as low as 20 ppb . Table 6 gives the

results of analysis of the zinc bar for silver and tin.

The two sets of values listed come from completely independent runs starting with new spiking solutions.

Table 6. Isotopic dilution determinations of

silver and tin in four samples of zinc SRM 683

ppm by weight

Elements

and run S amples

1 A 1 B 2 A 2 B

Silver 1 1.18 1.06 1.13 1.02

2 1.14 1.18 1.33 1.25

Av. 1.16 1.12 1.23 1.14

Tin 1 0.019 0.018 0.013 0.016

2 .023 .019 .014 .016

Av. 0.021 0.019 0.014 0.016

Three lots of zinc shot SRM 728 and both ends of two

bars of zinc SRM 683 were run. The results are given in

Table 7. The close agreement between the two samples for

all the elements arises from the fact that both samples were

produced from a common batch of zinc.

2 . Platinum

Spark source stable isotopic dilution analysis has

also been applied to the determination of elements in a doped

platinum sample SRM 68l. The impurities were concentrated

53
Table J. Average copper, "silver, and tin concentrations in

shot and bar samples of zinc.

ppm by weight

Elements

Samples Copper Silver Tin

SRM 728 (Shot) 5-54 1.16 0.021

Precision8, +.49 +.05 +.009

SRM 683 (Bar) 5-59 1.16 0.017

Precision + .26 +.12 +.001

Precision values are 95$ confidence interval for the mean,

(t S)/iTn. For SRM 728, n is 6; for SRM 683, n is 8.

by use of cation exchange columns. The actual preconcentration and spiking procedures used on the platinum and zinc

samples are described by R. Alvarez in Section 6 of this

report. Table 8 lists the values found by isotopic dilution

along with the final certified values and spark source

values calculated by other means in order to contrast the

capabilities of these techniques. In the second column are

listed the impurity concentrations computed without the benefit of a standard. In this case the elements were all assumed

to have the same atomic sensitivity as platinum when determined by measurement of the Pt 190 isotope. Corrections were

made for line width variation, isotopic abundances, and the

variation of plate sensitivity with mass. The third column

lists values determined by comparison to a platinum sample

of known composition. The impurity levels in this "comparison standard" ranged from 0.06$ Cu (600 ppm) to 0.194$ Ir

(1940 ppm). Thus the standard sample contains roughly 100 times

the impurity concentration as the "unknown" Pt 681. The next

column gives the spark source isotopic dilution results and

54
the last column the final certified values. The certified

values represent results from a number of methods; however,

the only values from the spark source entering into the

certified values are those from the isotope dilution determinations . Table 8. Comparison of results of three types of

mass spectrographic analyses to

certified values for Pt 68l

ppm by weight

.ement No star

48

idard

1000 ppm

standard

8.6

Isotope

dilution

SSMS

Certified

by NBS

Mg 12

Ca 27 11 -- —

Fe 9. 7 — — 5

Ni — — .46 .5

Cu 20 3.0 5.04 5.1

Zr 12 -- — 11

Rh 18 8.4 -- 9

Pd 17 8.8 5.92 6

Ag 15 2.5 2.09 2.0

Ir -- 12 — 11

Au -- 20 — 9

Pb 94 14 13.6 12

A comparison of results indicates the isotope dilution values

are in good agreement with the certificate value and therefore with the other techniques. The comparison to the "standard" sample does quite well considering that the standard

used contained 100 times the impurity level; gold is the only

element that can be considered to be in significant error.

Without the comparison standard however, positive errors as

55
high as a factor of 8 (for 'lead) were obtained using the

matrix sensitivity factor as is shown in column two.

D. Plate Calibration Functions

Two computer programs have been written to calculate

calibration curves from data with background readings via

iterative computation. Both use the method of least squares

and are designed to use known isotope ratios of elements to

calculate plate response. The first program uses a fourth

power polynomial to fit the plate calibration curve "shape".

The second assumes a probability function response and two

modifications thereof. These are, where b and c are the modifications:

(a) log intensity = K-.X+C

2

(b) log intensity = K-,x+KoX + C

3 (c) log intensity = K^x+K x

+<^ where x is the probability value of the percent absorption

and Ki, K2 , and K3 are plate constants to be determined.

2 The polynomial equation and the addition of K Q x and

K^x terms to our normal plate function of K,x+C are attempts

to allow more leeway in the "shape" of the function used to

fit the calibration data. Although the four-term polynomial

can fit the calibration data as well as or better than the

probability function, it will fit the plate response only

over the range covered by the calibration data. It cannot

predict plate response outside of this tested range. The

probability function, Seidel equation, and the Hull equation

on the other hand predict reasonable response outside of

their tested range since in each case their "shape" is fixed.

For this reason polynomials have not been adopted to repre2 3 sent plate response curves. Use of K x or K~x terms must

result in a closer fit to the true calibration curve. However, a limited testing of the three versions of the probability equations has shown only a small improvement with the

additional terms. Indications are that the equation

56
[log(intensity ) = K., x+ C] fits the plate response well enough

so that any discrepancies in fit are obscured by variations

in plate uniformity.

The effects on the calibration curves of setting the

microphotometer zero per cent absorption at plate background

or at a portion of the plate cleared by fixing before development were studied. For the polynomial these two cases are

mathematically identical. The three forms of the probability

equation showed changes in K values with this shift in zero;

however, there was no significant difference in the precision

of fit to the calibration data with the zero shift. Since

adjustment of zero to the background level is so difficult

to duplicate on the same plate at two different times, the

use of the cleared plate zero has been adopted.

E . New Computer Programs

New programs have been written for the time-shared computer for use with the spark source. An outline of some of

the most frequently used programs is given here.

1. Program PPMCAL

Purpose - To calculate impurity concentration from

data obtained from a plate, based either on information from

a standard sample or on the plate sensitivity to the matrix

element

.

Input data - Unit mass of isotope used, abundance of

isotope, exposure levels used and line areas measured for

the "standard", "unknown", and matrix plus concentration of

standard if available.

Output data - Concentration of unknown in ppm by

weight and atomic, and + the 95% confidence interval on the

limiting mean.

The results are based on the geometric mean, with the

confidence interval calculated from the variation in the unknown and the standard (or the matrix) data. If a standard

is not available the results are calculated from sensitivity

57
factors based on matrix sensitivity corrected for isotopic

abundances and variation in plate sensitivity with mass.

2. Program PAIRS

Purpose - To test for homogeneity among n sets of

duplicate samples; to compute statistics on isotope dilution

analysis

.

Input - Computed concentrations on independently

analyzed duplicates of several samples.

Output - Statistics to indicate:

a. overall precision of analysis, and

b. if the differences among samples indicate

inhomogeneities

.

3- Program SENSAT

Related to PPMCAL in form and input data. Uses

sensitivity data from several elements in a standard sample

to calculate an average plate sensitivity factor to be used

for elements without a standard. This value is then fed

into PPMCAL to replace the matrix sensitivity value.

P. J. Paulsen, D. E. Kelleher

58
6 . ANALYSIS OF HIGH PURITY MATERIALS

Our initial experimentation in applying isotope dilutionpreconcentration techniques to the spark source mass spectrometric determination of trace elements was outlined in

last year's annual report [3]- This project is conducted

as a joint investigation with P. J. Paulsen who describes

the spark source mass spectrometer activity in Section 5

of this report

.

The principal features of these isotope dilutionpreconcentration methods are:

1. The results are unaffected by "sorption"

and mechanical losses once the isotopic additions

("spikes") have been made and equilibrium established.

2. A determination of the recovery or yield

of the trace elements is unnecessary.

3. Since the high voltage spark source ionizes all elements, multi-element trace determinations can be made simultaneously.

4. The preconcentration features of these

methods provide higher intensities for the isotopic mass lines.

Since contamination from reagents, vessels, chemical

operations, and environment constitutes the principal limitation of the method, our efforts are directed toward developing techniques which minimize this contamination. Our objectives are to make reliable trace determinations particularly

at concentrations of less than one ppm with the main area of

applications being the analysis of materials designed to

serve as NBS Standard Reference Materials for trace analysis

.

Examples of these methods are discussed below:

A. Zinc

The method developed for the determination of Pb , Cd,

59
and Tl in zinc [3] was extended to the determination of Ag,

Cu, and Sn in the same matrix. These six elements, determined simultaneously j in Zinc NBS Standard Reference Materials 683 and 728, ranged from 11 ppm for Pb to 20 ppb for Sn

.

The isotopically enriched trace elements were electrodeposited from a solution of the zinc onto high-purity gold wires

using the cell shown in Figure 21. The cell body, made of

polytetrafluoroethy lene polymer, had been used previously

[16] to electrodeposit Ag onto the surface of a spectroscopic graphite electrode from a zinc solution. This technique had been proposed as a preconcentration method for

STIRRER ^

_£

! di

PLATINUM ANODE

ANODE COMPARTMENT

I in

Figure 21. Electrodeposition cell.

optical emission 'spectroscopy . For the isotope dilution

work, the graphite electrode was replaced with a Teflon

plug of the same diameter through which two gold wires had

been inserted to serve as the cathode. The Pt-Ru tubing was

60
replaced with a separate anode compartment to avoid generating Clp from the HC1 electrolyte.

During a series of experiments, it was observed that

the first sample of zinc gave a higher result for Sn than

succeeding samples from the same source. An aliquot of this

first sample run twelve days later gave a result that was in

117 agreement with the other samples. The 'Sn, added as the

"spike", had been obtained from the Oak Ridge National Laboratory as SnO„ , dissolved in HC1, and diluted with 6M HCL to a

concentration of 0.04yg/ml. The possibility that, for the first

sample, equilibrium had not been attained between the Sn from

117 the sample and the Sn spike was indicated. Consequently,

the procedure was modified to add the isotope solutions at the

early stages of sample dissolution rather than at the end

117 of this step. Moreover, since the Sn solution was so

dilute, i.e. 0.04yg/ml, there was concern that "sorption"

losses could have reduced the actual amount of "spike"

added. Therefore, for a second set of samples which were

117

run, 1 part of Sn spike was added to 100 parts of high

purity zinc to increase the total ion concentration. At this

ratio, the impurities in the zinc were too low to interfere

with the elements being analyzed. In addition, the tin spike

was added from a solution of 0.4yg/ml, a ten-fold increase

in concentration, and the volume added was reduced proportionately. Good agreement was obtained between the two sets

117 of results. The 0.4yg/ml Sn solution was assayed by

spiking with a known amount of normal tin and found to be

93$ of its original concentration eleven days after it had

been used to spike the samples.

B. Platinum

A method was developed to determine Ag, Cu, Pb , Pd,

and Ni simultaneously in an NBS Standard Reference Material

of Platinum, No. 68l. Since a manuscript detailing the

method has been prepared for publication, only an outline

61
is presented here. A weighed sample is dissolved in aqua

regia and solutions of stable isotopes are added. The solution is then evaporated to dryness, the salts dissolved in

water and the solution passed through a cation exchange

column. The isotopically enriched trace elements are retained on the column and the platinum passes into the effluent as chloroplatinate anion. After washing the column, the

trace elements are eluted with 3M HC1 into an electrolysis

cell and NH-. added to neutralize the acid. The trace elements are then electrodeposited onto gold wires. This procedure has several advantages: (1) an adherent sample form

particularly suited to spark source mass spectrometry is

provided; (2) the sample form is attained with a minimum of

handling and possible contamination; and (3) the trace elements in elemental form provide a simpler spectrum thus reducing the possibility of interferences. The gold wires are

then sparked in the mass spectrometer and the mass spectrum

recorded photographically. The results are calculated from

the isotope ratio measurements, the sample weight, the

weight of the separated isotopes ("spikes") added, the

isotope abundances of the separated isotopes and the natural

abundances (except for lead). For lead, the abundance varies in nature and must be measured for each material.

The results, shown in Table 9, were in good agreement

with other analytical methods as indicated by the "estimated

accuracy" of the certificate values. For Ni , an "estimated

accuracy" of the results was not made since the determination

had not been made by another method with sufficient precision

Other elements listed on the certificate are not shown.

C. Gold

Work is in progress to determine Fe , Ag, Cu , and possibly In simultaneously in samples of high purity gold. Although employing essentially the techniques developed for

the analysis of platinum, the concentration levels of these

62
Table 9- Concentrations determined by

isotope dilution in Platinum SRM 681

ppm by weight

Element

Ag

Isotope

dilution

2.09

Certificate

valuea

2.0

Cu 5.04 5.1

Pd 5-92 6

Pb 13.6 12

Ni 0.46 0.5

Estimated accuracy of

certificate value

Within 0.5 ppm of actual value

TT OS" " ""

H -i It tl It It

It o " " " "

See copy of certificate reproduced in the Appendix to

this report.

elements (Fe 0.2 ppm, Ag 0.1 ppm, Cu 0.1 ppm and In <0.1 ppm)

has made their precise determination difficult because of

contamination problems. The blanks are evaluated by spiking

reagents with the stable isotope solutions and going through

all of the steps of the procedure.

R. Alvarez

63
7. PERSONNEL AND ACTIVITIES

A. Personnel Listing

Spectro chemical Analysis Section

Bourdon P. Scribner, Section Chief

Arthur J. Ahearn, Research Physicist

Karen L. Loraski, Section Secretary

Group I. Optical Spectrometry

Marvin Margoshes, Chemist

Claude Veillon, Post Doctoral Research Chemist

(Terminated)

Joseph L. Weber, Physicist

Martha M. Darr, Chemist

Virginia C. Stewart, Chemist

Doward M. Bouchette, Physical Science Technician

Group II. X-Ray Spectrometry and Electron Probe

Microanalysis

Kurt F. J. Heinrich, Chemist

Ping-Kay Hon, Chemist

Donald L. Vieth, Physical Metallurgist (On extended

leave

)

Stanley D. Rasberry, Physicist

Mary Ann Giles, Chemist (Terminated)

Chong K. Kim, Chemist (Summer 1967)

Charles E. Fiori, Electronic Technician

Part Time Guest Workers

Harvey Yakowitz, NBS Metallurgy Division

David Carpenter, National Institutes of Health

Fielding Ogburn, NBS Metallurgy Division

Jacob Smit , NBS Metallurgy Division

Virginia H. Pennington, NBS Metallurgy Division

Michael Duke, Geological Survey

Group III. Spark Source Mass Spectrometry

Paul J. Paulsen, Chemist

Daniel E. Kelleher, Chemist

Part Time Guest Worker

Clemente Noutary, Atomic Energy Commission

Argentina

Group IV. Enrichment Techniques

Robert Alvarez, Chemist

64
B . Publications

1. Ahearn, A. J.

Spark Source Mass Spectrometer Measurements of Dopants

of Known Concentrations in Gallium Phosphide, Anal.

Chem. 39_, No. 3, 350-352, (1967).

2. Ahearn, A. J.

Spark Source Mass Spectrometric Analysis of Solids,

in "Trace Characterization, Chemical and Physical",

National Bureau of Standards, Monograph 100, April

1967, p. 3^7.

3. Heinrich, K. P. J., and Giles, M. A. M.

X-Ray Wavelength Conversion Tables and Graphs for

Qualitative Electron Probe Microanalysis, NBS

Technical Note 406, Sept. 25, 1967-

4. Eick, J. D., Caul, H. J., Smith, D. L., and Rasberry,

S. D.

Analysis of Gold and Platinum Group Alloys by

X-Ray Emission with Corrections for Interelement

Effects, Appl. Spectry. 21, No. 5, 324-328 (1967).

5. Margoshes, M.

Selection of Wavelengths for Atomic Absorption

Spectrometry, Anal. Chem. 39., No. 10, 1093-1096

(1967).

6. Heinrich, K. P. J.

Electron Probe Microanalysis by Specimen Current

Measurement. X-Ray Optics and Microanalysis, Hermann

Eds., Paris, 1966, p. 159 (Appeared in fall of 1967).

7. Scribner, B. F. (Editor)

Activities of the NBS Spectrochemical Analysis

Section, July 1966 through June 1967, NBS Tech.

Note 422, Jan. 1968

.

8. Fitzgerald, R., Keil, K., and Heinrich, K. F. J.

Solid-state Energy-dispersion Spectrometer for

Electron Microprobe X-ray Analysis, Science 159

528-529 (1968).

9. Scribner, B. F.

The Impact of Computer Techniques, on Atomic Spectroscopy (A summary), XIII Colloquium Spectroscopicum

Internationale, Ottawa June 1967, (Published Jan.

1968) p. 97-

65
10. Margoshes, M. , Marcellus , D. A., and Rasberry, S. D.

Properties of the Laser Probe with Rotating Prism

and Liquid Q-Switches (A summary). Ibid p. 156 .

11. Veillon C, and Margoshes, M.

Atomic Absorption and Atomic Fluorescence Spectrometry with a Plasma Torch (A summary), Ibid p. 28l.

12. Heinrich, K. F. J.

Inhomogeneity Studies of Alloys with the Electron

Microprobe (A summary), Ibid p. 421.

13. Alvarez, R.

The Spectrochemical Determination of Ultra-Trace

Elements in High-Purity Metals by Preconcentration

Using Matrix Volatilization (A summary), Ibid p. 454.

14

.

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, 55 pp. Feb. 1968

.

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

Quantitative Electron Probe Microanalysis: Absorption Correction Uncertainty, Microchim. Acta 1968 , 182-200.

16. Rasberry, S. D., Caul, H. J., and Yezer, A.

X-Ray Fluorescence Analysis of Silver Dental Alloys

with Correction for a Line Interference, Spectrochimica Acta 23B, No. 5, March, 345-351 (1968).

17. Heinrich, K. F. J.

Scanning Electron Probe Microanalysis, ASTM Spec.

Tech. Publ. 430 (1968) p. 315.

18. Margoshes, M., and Scribner, B. F.

Emission Spectrometry (A review), Anal. Chem. 40 , No. 5, 223R-246R (1968)

.

19. Heinrich, K. F. J. (Editor)

Quantitative Electron Probe Microanalysis, NBS

Spec. Publ. 298 ( in press).

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

Quantitative Electron Probe Microanalysis

Fluorescence Correction Uncertainty, Microchim.

Acta (In press)

.

66
21. Heinrich, K. P. J.

Common Sources of Error in Electron Probe Microanalysis, Advances in X-ray Analysis, Vol. 11,

Plenum Press, N. Y. (In press).

22. Veillon, C, and Margoshes, M.

A Pneumatic Solution Nebulization System Producing

Dry Sample Vapor for Atomic Spectroscopy. Spectrochim. Acta, Part B (In press).

23. Veillon, C, and Margoshes, M.

An Evaluation of the Induction-coupled, Radio-frequency Plasma Torch for Atomic Emission and Atomic

Absorption Spectrometry, Spectrochim. Acta, Part B

(In press )

.

C. Talks Given

1. Heinrich, K. P. J., "Common Sources of Error in Microprobe Analysis", Proceedings of Annual Conference on

Applications of X-ray Analysis, Denver, Colorado,

August 10, 1967.

2. Scribner, B. F., "The Role of the Time-Sharing Computer

in the Spectrochemical Laboratory", XII International Congress of Pure and Applied Chemistry, Prague,

Czechoslovakia, September 5> 1967.

3. Rasberry, S. D., "New Methods of Data Acquisition and

Processing in Spectrochemical Analysis", Society for

Applied Spectroscopy, Birmingham, Alabama, September

30, 1967.

4. Heinrich, K. F. J., "Electron Probe Microanalysis of

Biological Specimens", National Institutes of Health

Bethesda, Maryland, October 4, 1967.

5. Margoshes, M., "Spectrochemical Analysis of Small Volumes with the Laser Probe", Eastern Analytical Symposium, New York, New York, November 8, 1967.

i. Scribner, B. F., "Dr. William F. Meggers - A Dedication"

Eastern Analytical Symposium, New York, New York,

November 10, 1967-

Margoshes, M., "Laser Probe Spectrochemical Microanalysis", Society for Applied Spectroscopy,

Clarksville, Maryland, February 27, 1968.

67
8. Scribner, B. P., "Future Standards for Instrumental

Analysis", Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Cleveland, Ohio,

March 6, 1968.

9- Paulsen, P. J., "Spark Source Mass Spectrographic

Analysis of High-Purity Zinc by Isotope Dilution and

Electrodeposition of Trace Elements", Pittsburgh

Conference on Analytical Chemistry and Applied

Spectroscopy, Cleveland, Ohio, March 7, 1968.

10. Margoshes, M., "An Algorithm for Computer Fitting of

Spectrometric Analytical Curves", Pittsburgh

Conference on Analytical Chemistry and Applied

Spectroscopy, Cleveland, Ohio, March 8, 1968.

11. Alvarez, R., "Determination of Trace Elements in HighPurity Platinum by Isotope Dilution, Spark Source

Mass Spectrometry", 155th American Chemical Society

National Meeting, San Francisco, California,

April 1, 1968.

12. Paulsen, P. J., "Spark Source Mass Spectrometry and Its

Application to the Analysis of PPM Level Impurities",

Mass Spectrometry Discussion Group of Metropolitan

Washington, Springfield, Virginia, April 15, 1968.

13- Alvarez, R. "Stable Isotope Dilution and Separation of

Trace Elements for Determination by Spark Source

Mass Spectrometry", 762nd Meeting of the Chemical

Society of Washington, College Park, Maryland,

May 3, 1968.

14. Paulsen, P. J., "Standard Reference Materials for Spark

Source Mass Spectrometry", 16th Annual Conference on

Mass Spectrometry and Allied Topics, Pittsburgh, Penn.,

May 15, 1968.

15. Ahearn, A. J., "Homogeneity of Ilford Q2 Emulsions and

Precision of Ion Beam Measurements in Spark Source

Mass Spectrometry", 16th Annual Conference on Mass

Spectrometry and Allied Topics, Pittsburgh, Penn.,

May 16, 1968.

16. Margoshes, M., "Calibration of Photographic Emulsion on

a Digital Computer — A Critical Test of the Method",

7th National Meeting, Society for Applied Spectroscopy, Chicago, 111., May 16, 1968.

17. Scribner, B. F., "Future Standards for Instrumental

Analysis", Seminar: NBS Meets with Pittsburgh Industry,

Dept. of Commerce, Pittsburgh, Penn., May 21, 1968.

68
18. Margoshes, M. 3 "Time-Sharing Computers", 12th Annual

May Conference, Cleveland Section of Society for

Applied Spectroscopy and American Chemical Society,

Cleveland, Ohio, May 22, 1968.

19. Margoshes, M., "Use of Computers in Emission Spectrochemical Analysis", ACS Summer Symposium, Pennsylvania State University, University Park, Pa., June

19, 1968.

D . Committee Activities

B. F. Scribner

Member, ASTM Committee E-2 on Emission Spectroscopy

Member, ASTM Committee E-13 on Absorption Spectroscopy

Member, Program Committee, Eastern Analytical

Symposium, 1967

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, Colloquium

Spectroscopicum Internationale, 1967

Chairman, Nominating Committee, Society for Applied

Spectroscopy, 1968

Chairman, Baltimore-Washington Section, SAS,

1967-68

Member, Wavelength Tables Committee, University of

Michigan

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, 1967-68

Program Chairman, Baltimore-Washington, Section,

SAS, 1967-68

K. F. J. Heinrich

President-Elect , Electron Probe Analysis Society of

America, 1968

Assistant Editor, Mikrochimica Acta

69
A. J. Ahearn

Vice-Chairman, Subcommittee VII, ASTM Committee E-l4

on Mass Spectrometry and Allied Subjects

Co-Chairman, Workshop on Spark Source Mass Spectrometry,

NBS, Nov. 1967

P* J. Paulsen i

Member, Subcommittee VII, ASTM Committee E-14 on

Mass Spectrometry and Allied Subjects

Co-Chairman, Workshop on Spark Source Mass

Spectrometry, NBS , Nov. 1967

R. Alvarez

Member, ASTM Committee E-2 on Emission Spectroscopy

J. L. Weber

Member, ASTM Committee E-2 on Emission Spectroscopy,

Subcommittees IV, VII, and IX

S. D. Ras berry

Member, Laser Task Group, ASTM Committee E-2

70
8 . ACKNOWLEDGMENTS

We have had the benefit of considerable assistance from

persons in other groups and of the supporting services of

NBS including library, plant, and shops; these have been

invaluable to the operation of a rather complex laboratory.

Some individuals who were especially helpful are named below.

Dr. Robert J. Arms of the computer Services Division

has provided very useful advice on computer programming problems. Mr. Brian Joiner of the Statistical Engineering Section assisted in problems involving applications of statistics . Mr. Harvey Yakowitz of the Metallurgy Division has again

worked closely with our microprobe group especially on problems of quantitative microprobe analysis.

Mr. John Hettenhouser of the Instrument Shop provided

excellent service on careful preparation of samples of standard

reference materials for analyses in our Section.

Mrs. Rosemary Maddock has continued to aid our group in

the area of publications including the planning and preparation of illustrations and slides.

Miss Karen Loraski, our Section Secretary, has been with

us almost a year. Her assistance in performing a variety of

duties to the Section, including typing of complex manuscripts and reports, is greatly appreciated.

71
9. LIST OF REFERENCES

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

Optical Spectrometry j 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 461, Sept., 19 66

.

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

1967," NBS Technical Note 422, Jan. 1968.

[4] 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.

[5] Veillon, C., and Margoshes, M., " A Pneumatic Solution

Nebulization System Producing Dry Aerosol for Atomic

Spectroscopy," Spectrochim. Acta, Part B, (in

press)

.

[6] Veillon, C., and Margoshes, M., "An Evaluation of the

Induction-Coupled, Radio-Frequency Plasma Torch for

Atomic Emission and Atomic Absorption Spectrometry,"

Spectrochim. Acta, Part B ( in press).

[7] Scribner, B. F., and Margoshes, M. , Actes du IX Colloquium Spectroscopicum Internationale, Vol. 2,

Groupement pour 1'Avancement des Methodes Spectrographiques, Paris (1962), pp. 309-24.

[8] Kaiser, H., Spectrochim. Acta 3, 159 (1948).

[9] Michaelis, R. E., and Wyman, L. L., "Preparation of

NBS White Cast Iron Spectrochemical Standards," NBS

Miscellaneous Publication 260-1, June, 1964.

[10] Yakowitz, H., and Heinrich, K. F. J., "Composite Microprobe Scanning Images in Color." To be presented at

the Third National Conference, Electron Probe

Analysis Society of America, Chicago, July 1968.

[11] Heinrich, K. F. J., "X-Ray Absorption Uncertainty"

The Electron Microprobe , 1964, J. Wiley & Sons,

N. Y., pp. 296-377.

72
[12] Yakowitz, H.-, and Heinrich, K. F. J., Mikrochim. Acta,

1968 (1) , 182-200.

[13] Heinrich, K. F. J . , and Yakowitz, H., Mikrochim. Acta,

1968 (5) (in press)

.

[14] Rasberry , S. D., Caul, H. J., and Yezer, A., Spectrochim. Acta. 22B, No. 5, 3^5-351 (1968).

[15] Stefani, R., Cornu, A., Bourguillot, R., Robin, A. M.

,

and Brun, J. C, Chim. Anal. (Paris) 48, 253 (1966)

[16] Alvarez, R., "Electrodeposition of Trace Constituents

as a Preconcentration Technique for Optical Emission Spectroscopy", contributed paper to Symposium

on Trace Characterization, NBS October 7, 1966,

copy available on request to author.

73

U. S. Depart^ttTof Commerce

Alexander ^STrowbridge,

Sec

National lu Standards

rector

APPENDIX

Certificate of &nalps;te

Standard Reference Materials 680 and 681

High-Purity and Doped Platinum 1

[NOTE: These materials are issued as interim standards to meet the needs of analysts

working at trace level concentrations in platinum. The range of values reported

represents the present state of the art in the cooperating laboratories.]

Element : SRM #680 High-Purity

Recommended

Value

Range of

Values Reported

SRM #681 Doped

Recommended

Value

Range of

Values Reported

Concentration in Parts per Million by Weight 5

Copper

Silver

Palladium

Lead

Iron Nickel

Gold

Magnesium

Zirconium

Rhodium

Iridium

Oxygen

Range laboratory only

1. The platinum materials are in the form of wire 0.020 inch (0.61 mm) in diameter and are available in two lengths, 4 inches

(10.2 cm) designated L-l and 39.4 inches (1.0 m) designated L-2.

2. Other elements are also contained in the standards ; some of them such as Al, Ca, Na, Si, and Sn may be certified at a

later date.

3. The values listed are based on a consideration of the analytical methods and results reported by cooperating laboratories. Elements are listed in order of decreasing estimated accuracy for SRM 681. Close agreement among results from laboratories using different, reliable methods increases the degree of confidence in the recommended values, making possible esti- mates of accuracy for the following elements.

a. For Cu and Ag in SRM 681, values are estimated to be within 0.6 ppm of the actual value.

b. For Pd in SRM 681, values are estimated to be within 1 ppm of the actual value.

c. For Pb in SRM 681, values are estimated to be within 2 ppm of the actual value. For other elements in SRM 681 and all elements in SRM 680, either because a single method was used or because of lack of agreement among methods, no estimate of accuracy can be made at this time. However, in about six months a revised certifi- cate will be issued in which an attempt will be made to give estimate of accuracy.

Washington, D. C. "20234

December 28, 1967

W. Wayne Meinke, Chief

Office of Standard Reference Materials

(over) 75
These standards have been established to provide homogeneous reference materials

for the analysis of high-purity platinum, a material with extensive scientific and industrial applications, but a material the properties of which are greatly affected by the kind

and amount of impurity elements. In cooperation with the National Bureau of Standards,

the planning, preparation, homogeneity testing and analyses programs were conducted

by the following organizations: Sigmund Cohn; Johnson, Matthey & Co., Ltd.; Engelhard Industries, Inc. ; and RCA Laboratories.

The material for SRM No. 680 was prepared at Sigmund Cohn by induction melting

of high-purity platinum sponge in a zirconium silicate crucible, and by casting into a

platinum-lined, water-cooled copper mold. The ingot was trimmed, swaged, and drawn

into wire using the utmost precautions to minimize contamination.

The material for SRM No. 681 was prepared at Engelhard Industries by induction

melting under helium of high-purity platinum and a specially prepared pilot alloy containing the desired dopant elements. The melt was cast into a graphite mold and the ingot

processed in a manner similar to SRM 680.

Extensive homogeneity testing was performed by NBS Washington and Boulder as

well as by the four cooperating laboratories listed above using a combination of the

following methods : optical emission and spark source mass spectrographic analyses ; and

electrical measurements including EMF, Temperature Coefficient of Resistivity (T.C.R.),

and Residual Resistivity Ratio (RRR) . Both lots of material were found to be homogeneous within the limits of precision of the analytical methods used at these trace levels. Elemental analyses were made at the National Bureau of Standards by one or more of the

following methods: optical emission spectrography, spark source mass spectrography

(isotopic dilution), polarography, spectrophotometry, activation analysis, and vacuum

fusion.

Cooperating in this elemental analysis program were the following organizations who

contributed emission spectrographic measurements:

J. Bishop & Co., Malvern, Pennsylvania

Engelhard Industries, Newark, New Jersey

Johnson, Matthey & Co., Ltd., London, England

CAUTION

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

placing the sample in warm aqua regia (3 HC1 + 1 HN03 ) for approximately five minutes, and then followed by rinsing in distilled water.

76
U. S. Departntemf of Commerce

C. BMmith

TSe»B^rfJr

APPENDIX

National A. V. ^q Standards

rector

Certificate of &nalpgtg

Standard Reference Material 1138, 1139

Cast Steel Standards

SRM No.

Element

Carbon

Manganese

Phosphorus

Sulfur

Silicon

Copper

Nickel

Chromium

Vanadium

Molybdenum

SIZE AND META

square and 1 technique.

1138

Cast Steel 1

0.12

.43 .053

.053 .34 .09

Percent

1139

Cast Steel 2

0.792 .98

.01,

.013

.85

.40

•9

3 1.96

0.24

.51

CONDITION: Samples are approximately 1 1/4 inches

"they were chill-cast by a rapid unidirectional solidification

CERTIFIED PORTION: The certified portion for each sample is that extending upward

5/16 inch from the chill-cast or test surface (the largest surface opposite the numbered

surface). This portion only was analyzed in the cooperative program for certification. PROVISIONAL CERTIFICATION: The provisional value listed for an element is the

present best estimate of the true value based on the results of the cooperative analytical

program. The provisional value is not expected to deviate from the true value by more than

± 1 in the last significant figure reported; for subscript figures, the deviation is not expected

to be more than ± 5 in the subscript figure.

Washington, D. C. 20234

April 30, 1968

W. Wayne Meinke, Chief

Office of Standard Reference Materials

(over)

77
PLANNING, PREPARATION, TESTING, ANALYSIS: The two cast steel standards are made available as a result of a cooperative program between the Steel Founders' Society of

America and the National Bureau of Standards.

The material for the standards was melted and cast at the American Cast Iron Pipe

Company, Birmingham, Ala. with use of the NBS chill-cast mold assembly. The preparation

and homogeneity testing was similar to that described in NBS Misc. Publ. 260-1, Standard

Reference Materials: Preparation of NBS White Cast Iron Spectrochemical Standards,

Robert E. Michaelis and LeRoy L. Wyman, June 19, 1964.

Homogeneity testing was performed and found to be satisfactory for the elements certified.

Chemical, optical emission, and x-ray analyses, or combinations thereof, were made at the

National Bureau of Standards, the Research Laboratories of the General Motors Corporation, and the following member foundries of the Steel Founders' Society of America:

General Metals Corporation, Calif.

The Massillon Steel Castings Company, Ohio

Lebanon Steel Foundry, Pa. The Duriron Company, Inc., Ohio

American Steel Foundries, Inc., Ind.

Esco Corporation, Oregon

Shenango-Penn, Ohio

Minneapolis Electric Steel Castings Company, Minn.

Ross-Meehan Foundries, Tenn.

Empire Steel Castings, Inc., Pa.

Chemical analyses for certification were made on representative samples for each standard at the National Bureau of Standards and the following member foundries of the American

Steel Founders' Society of America:

Minneapolis Electric Steel Castings Company, Minn.

Esco Corporation, Oregon

Electric Steel Castings, Inc., Texas

Symington Wayne Corporation, New York

American Steel Foundries, Inc., Ind.

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.

CAUTIONS:

1. Determinations made on other than the chill-cast or test surface are not recommended

because of the unidirectional solidification structure.

2. These chill-cast standards are designed for calibration in the analysis of samples prepared

in the same general manner; samples prepared by other casting techniques or having

different metallurgical condition may exhibit a bias in the results. 78
National A. VA

of Commerce

th

Standards

irector

APPENDIX

Certificate of &nalpsfe

Standard Reference Materials 1140, 1141, and 1142

Ductile Iron Standards

1140 1141 1142 SRM No. Ductile Iron 1 Ductile Iron 2 Ductile Iron 3

Element Percent

Carbon 3.18 3.64 2.94 Manganese 0.72 5 0.48 0.18 Phosphorus .007 .072 .20

Sulfur .010 .020 .015

Silicon 1.92 1.11 3.33 Copper 0.10 0.21 i.o 2 Nickel .028 .54 1.6S Chromium .030 .14s 0.05 3 Vanadium .030 .009 .006 Molybdenum •09 •°5 K \ .02 2 Titanium .10 ^ .008 Aluminum (.01) a ^ (.09)

Arsenic (.07) a!^1 (.015) Magnesium .019 ^v(( J}*1 .10 Cerium (.09) /f* \\^.05) (.015) Yttrium (<.002L< A

^

N

^ .04 .01

a Values in parentheses ^©""nht^fc^rtifieS but are provided for additional information on

the composition. ^^\

SIZE AND ri^SlD^ISSlCAL CONDITION: Samples are approximately 1 1/4 inches

square and 1/^mcrrthick; they were chill-cast by a rapid unidirectional solidification technique. *^

CERTIFIED PORTION: The certified portion for each sample is that extending

upward 5/16 inch from the chill-cast or test surface (the largest surface opposite the

numbered surface). This portion only was analyzed in the cooperative program for

certification. PROVISIONAL CERTIFICATION: The provisional value listed for an element is the

present best estimate of the true value based on the results of the cooperative analytical

program. The provisional value is not expected to deviate from the true value by more

than + 1 in the last significant figure reported; for subscript figures, the deviation is not expected to be more than ± 5 in the subscript figure.

Washington, D. C. 20234

May 22, 1968

W. Wayne Meinke, Chief

Office of Standard Reference Materials

(over) 79
PLANNING, PREPARATION, TESTING, ANALYSIS: The three ductile iron standards

are made available as a result of the cooperative program between the National Bureau of

Standards and the American Cast Iron Pipe Company. The standards were developed at the request of the Ductile Iron Society and the American Foundrymen's Society.

The material for the standards was melted and cast at the American Cast Iron Pipe

Company, Birmingham, Alabama, with use of the NBS chill-cast mold assembly. The

preparation and homogeneity testing was similar to that described in NBS Misc. Publ.

260-1, Standard Reference Materials: Preparation of NBS White Cast Iron Spectrochemical Standards, Robert E. Michaelis and LeRoy L. Wyman, June 19, 1964.

Homogeneity testing was performed at NBS by D. M. Bouchette and was found to be

satisfactory for the elements certified.

Analyses for certification were performed at NBS and included chemical (J. R. Baldwin),

optical emission (D. M. Bouchette, J. L. Weber, Jr., M. M. Darr, and M. Margoshes), x-ray

(S. D. Rasberry and M. M. Darr) and activation (P. D. LaFleur and G. J. Lutz). Analyses were performed at the American Cast Iron Pipe Company and included chemical (R. N.

Smith and J. B. Hobby) and optical emission (I. Glaze and W. R. Kennedy).

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.

CAUTIONS:

1. Determinations made on other than the chill-cast or test surface are not recommended

because of the unidirectional solidification structure.

2. These chill-cast standards are designed for calibration in the analysis of samples

prepared in the same manner; samples prepared by other casting techniques or having

other than a white structure may result in considerable bias.

3. Because the samples exhibit a change with respect to the columnar structure, both

among standards and from bottom to top of the certified portion of the samples, the

surface preparation for x-ray spectroscopic analysis may be critical. (A metallographic

polishing technique is recommended).

4. Because of the poor heat conductivity of the ductile irons, difference in volatility rates for certain elements in emission spectroscopic analysis may occur depending on the

location of the burn and the source parameters.

SUPPLEMENTAL INFORMATION

The elements boron, calcium, lead, and tin also are present in these standards. One or more may be certified at a later date.

80
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