Czichos H., Saito T., Smith L.E. (Eds.) Handbook of Metrology and Testing

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138 Part A Fundamentals of Metrology and Testing

3.12 Further Reading: Books and Guides

The following is a selection of sources and is nei-

ther comprehensive nor intended as a recommenda-

tion.

Statistics

•

NIST/SEMATECH e-Handbook of Statistical Meth-

ods, http://www.itl.nist.gov/div898/handbook/ (last

updated June 23, 2010, last accessed June 8,

2011)

•

G. W. Snedecor, W. G. Cochran: Statistical Methods

(Iowa State Univ. Press, Ames 1993)

•

R. Caulcott: Statistics in Research and Development

(Chapman Hall, New York 1983)

•

V. Barnett, T. Lewis: Outliers in Statistical Data,

3rd edn. (Wiley, New York 1994)

•

P. J. Huber: Robust Statistics (Wiley, New York

1981)

Experimental Design

•

G. M. Clarke: Statistics and Experimental Design

(Edward Arnold, London 1984)

•

S. N. Deming, S. L. Morgan: Experimental Design:

A Chemometric Approach (Elsevier, Amsterdam

1987)

Quality Control

•

J. W. Oakland: Statistical Process Control (Heine-

mann, Oxford 1989)

•

ISO 8258:1991: Shewhart Control Charts (ISO,

Geneva 1991)

Uncertainty Estimation

•

S. G. Rabinovich: Measurement Errors and Uncer-

tainties: Theory and Practice (Springer, New York

2000)

•

ISO: Guide to the Expression of Uncertainty in

Measurement, 2nd edn. (ISO, Geneva 1995)

•

ISO TS 21748:2005: Guide to the Use of Repeata-

bility, Reproducibility and Trueness Estimates in

Measurement Uncertainty Estimation (ISO,Geneva

2005)

Free and Open-Source Statistical Software

•

R: A Language and Environment for Statistical

Computing (R Foundation for Statistical Comput-

ing, Vienna 2005), http://www.r-project.org/ (last

accessed June 8, 2011)

•

NIST Dataplot: http://www.itl.nist.gov/div898/

software/dataplot/homepage.htm (date created June

5, 2001, last updated May 15, 2010, last accessed

June 8, 2011)

•

AMC Software Excel add-ins: http://www.rsc.org/

Membership/Networking/InterestGroups/

Analytical/AMC/Software/index.asp (Roy. Soc.

Chem., London 2011)

General Statistics

•

GenStat (VSN International Ltd.): Video Streaming

Network (2011) http://www.vsn-intl.com/?s=genstat

(last accessed June 3, 2011)

•

Minitab (Minitab Inc.): http://www.minitab.com/en-

DE/default.aspx (Minitab, State College 2011)

•

SAS/STAT (SAS Institute Inc.):

http://www.sas.com/ (SAS Institute Inc., Cary 2011)

•

TIBCO Spotﬁre S+: http://spotﬁre.tibco.com/

products/s-plus/statistical-analysis-software.aspx

(TIBCO, Somerville) (last accessed June 8, 2011)

•

SPSS (IBM SPSS Inc.): http://www.spss.com/ (last

accessed June 8, 2011)

•

Statistica (Statsoft Inc.): http://www.statsoft.com/

(last accessed June 8, 2011)

Experimental Design

•

Design-Ease (StatEase Inc.):

http://www.statease.com/ (Stat-Ease, Inc., Min-

neapolis 2011)

•

MODDE (Umetrics): http://www.umetrics.com/

(Umetrics, Andover 2011)

References

3.1 P.M. Gy: Sampling of Particulate Materials, The-

ory and Practice (Elsevier, Amsterdam 1979)

p. 431

3.2 M.H. Ramsey, S.L.R. Ellison (Eds.): Eurachem/EURO-

LAB/CITAC/Nordtest/AMC Guide: Measurement Uncer-

tainty Arising from Sampling: A Guide to Methods

and Approaches (Eurachem, Prague 2007)

3.3 ISO: Guide to the Expression of Uncertainty in Meas-

urement, 2nd edn. (ISO, Geneva 1995)

3.4 U. Kurfürst, A. Desaules, A. Rehnert, H. Muntau: Esti-

mation of measurement uncertainty by the budget

approach for heavy metal content in soil under dif-

ferent land use, Accredit. Qual. Assur. 9,64–75

(2004)

Part A 3

Quality in Measurement and Testing References 139

3.5 Analytical Methods Committee (AMC): Uncertainty of

Measurement: Implications of its Use in Analytical

Science, Analyst 120, 2303–2308 (1995)

3.6 M.H. Ramsey, A. Argyraki: Estimation of measure-

ment uncertainty from ﬁeld sampling: Implications

for the classiﬁcation of contaminated land, Sci. Total

Environ. 198, 243–257 (1997)

3.7 J.A. Lyn, M.H. Ramsey, S. Coad, A.P. Damant,

R. Wood, K.A. Boon: The duplicate method of uncer-

tainty estimation: Are eight targets enough?, Analyst

132, 1147–1152 (2007)

3.8 M.H. Ramsey: Sampling as a source of measure-

ment uncertainty: Techniques for quantiﬁcation and

comparison with analytical sources, J. Anal. At.

Spectrom. 13, 97–104 (1998)

3.9 S.L.R. Ellison, M. Roesslein, A. Williams (Eds.):

Eurachem/CITAC Guide: Quantifying Uncertainty in

Analytical Measurement (Eurachem, London 2000),

Available from the Eurachem secretariat, or from LGC

Limited

3.10 M.H. Ramsey, S. Squire, M.J. Gardner: Synthetic

reference sampling target for the estimation of

measurement uncertainty, Analyst 124(11), 1701–1706

(1999)

3.11 S. Squire, M.H. Ramsey, M.J. Gardner, D. Lis-

ter: Sampling proﬁciency test for the esti-

mation of uncertainty in the spatial delin-

eation of contamination, Analyst 125(11), 2026–2031

(2000)

3.12 M. Thompson, T. Fearn: What exactly is ﬁtness for

purpose in analytical measurement?, Analyst 121,

275–278 (1996)

3.13 M.H. Ramsey, P.D. Taylor, J.C. Lee: Optimized con-

taminated land investigation at minimum overall

cost to achieve ﬁtness-for-purpose, J. Environ.

Monit. 4(5), 809–814 (2002)

3.14 M.H. Ramsey, J.A. Lyn, R. Wood: Optimised un-

certainty at minimum overall cost to achieve

ﬁtness-for-purpose in food analysis, Analyst 126(10),

1777–1783 (2001)

3.15 B. Geelhoed, H.J. Glass: Comparison of theories for

the variance caused by the sampling of random mix-

tures of non-identical particles, Geostand. Geoanal.

Res. 28(2), 263–276 (2004)

3.16 C.C. Ferguson: The statistical basis for the spatial

sampling of contaminated land, Ground Eng. 25,34

(1992)

3.17 International vocabulary of metrology — Basic and

general concepts and associated terms (VIM), 3rd

edn., JCGM 200:2008 (including Corrigendum of Mai

2010)

3.18 BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML: Guide to the

Expression of Uncertainty in Measurement (GUM),1st

edn. (BIPM and IEC and IFCC and ISO and IUPAC and

IUPAP and OIML, Paris 1993), corrected and reprinted

in 1995

3.19 ISO: Guide to the Expression of Uncertainty in Meas-

urement, 1st edn. (ISO, Geneva 1995)

3.20 EUROLAB: Guide to the Evaluation of Measure-

ment – Uncertainty for Quantitative Test Re-

sults, Tech. Rep. 1/2006 (EUROLAB, Paris 2006),

http://www.eurolab.org/

3.21 EUROLAB: Measurement Uncertainty Revisited: Al-

ternative Approaches to Uncertainty Evalua-

tion, Tech. Rep. 1/2007 (EUROLAB, Paris 2007),

http://www.eurolab.org/

3.22 ISO: ISO 5725 (series of standards in 6 parts), Accuracy

(trueness and precision) of measurement methods

and results (ISO, Geneva 1998–2005)

3.23 ISO/TS 21748, Guide to the use of repeatability, repro-

ducibility and trueness estimates in measurement

uncertainty estimation (ISO, Geneva 2004)

3.24 EURACHEM/CITAC: Quantifying Uncertainty in Analyti-

cal Measurement, 2nd edn. (EURACHEM/CITAC, Prague

2000)

3.25 EUROLAB: Measurement Uncertainty in Testing,Tech.

Rep. 1/2002 (EUROLAB, Paris 2002)

3.26 EA: Expression of Uncertainty in Quantitative

Testing, Guideline EA-4/16 (EA, Rijswijk 2003),

www.european-accreditation.org/content/

publications/pub.htm (last accessed 14 April 2011)

3.27 B. Magnusson, T. Näykki, H. Hovind, M. Krysell:

Handbook for Calculation of Measurement Uncer-

tainty in Environmental Laboratories, Tech. Rep. 537

(Nordtest, Espoo 2003)

3.28 EA: Expression of the Uncertainty of Measurement in

Calibration, Guideline EA-4/02 (European Coopera-

tion for Accreditation, Paris 1999)

3.29 AFNOR FD X 07-021: Fundamental standards –

Metrology and statistical applications – Aid in

the procedure for estimating and using uncer-

tainty in measurements and test results (Euro-

pean Diagnostic Manufacturers Association, Brussels

2006)

3.30 Supplement No. 1 to the GUM: Propagation of distri-

butions using a Monte Carlo method (ISO/IEC Guide

98-3:2008/Suppl 1:2008) (BIPM, Paris 2008)

3.31 ISO 13528: Statistical methods for use in proﬁciency

testing by interlaboratory comparison (ISO, Geneva

2005)

3.32 ISO/TS 21749: Measurement uncertainty for metro-

logical applications (ISO, Geneva 2005)

3.33 ISO: ISO 9000, International Consensus on Good

Quality Management Practices (ISO, Geneva 2000)

3.34 CITAC/EURACHEM: Guide to Quality in Analytical

Chemistry – An Aid to Accreditation (CITAC/EURACHEM,

Prague 2002)

3.35 AOAC International: AOAC Peerveriﬁed Methods Poli-

cies and Procedures (AOAC International, Gaithers-

burg 1993)

3.36 S. Kromidas: Validierung in der Analytik (Wiley-VCH,

Weinheim 1999), (in German)

3.37 W. Wegscheider: Validation of analytical meth-

ods. In: Accreditation of Chemical Laboratories,

ed. by H. Günzler (Springer, Berlin, Heidelberg

1996)

Part A 3

140 Part A Fundamentals of Metrology and Testing

3.38 ISO: ISO Guide 30, Terms and Deﬁnitions Used in

Connection with Reference Materials (ISO, Geneva

1992)

3.39 B. King: 4E-RM-Guide, Selection and use of ref-

erence materials – A basic guide for laboratories

and accreditation bodies (EURACHEM, Prague 2002)

http://www.eurachem.

ut.pt/

3.40 IAGRM: Final Third Party Quality Assessment of Pro-

ducers of Reference Materials (IAGRM, Bristol 2004)

3.41 ISO: International Vocabulary of Basic and General

Terms in Metrology (ISO, Geneva 1999)

3.42 ISO: ISO Guide 34, General Requirements for the

Competence of Reference Materials Producers (ISO,

Geneva 2009)

3.43 United Nation: Glossary of Terms for Quality Assur-

ance and Good Laboratory Practices (United Nation,

New York 1995)

3.44 M.J.T. Milton, T.J. Quinn: Primary methods for the

measurement of amount of substance, Metrolo-

gia 38, 289–296 (2001), http://www.bipm.org/en/

metrologia/ (last accessed 14 April 2011)

3.45 BAM: COMAR database (Federal Institute for

Materials Research and Testing, Berlin 2011),

http://www.comar.bam.de

3.46 International Atomic Energy Agency (IAEA): Nu-

clear Sciences and Applications (IAEA, Vienna 2011),

http://www-naweb.iaea.org

3.47 Bureau International des Poids et Mesures (BIPM):

http://www.bipm.org/ (BIPM, Paris 2011)

3.48 ISO: ISO Guide 31, Contents of Certiﬁcates of Reference

Materials (ISO, Geneva 2000)

3.49 A. Zschunke (Ed.): Reference Materials in Analytical

Chemistry (Springer, Berlin, Heidelberg 2000)

3.50 J. Pauwels, A. Lamberty: CRMs for the 21st century

new demands and challenges, Fresenius J. Anal.

Chem. 370, 111–114 (2001)

3.51 M. Parkany, H. Klich, S.D. Rasberry: REMCO, the ISO

Council Committee on Reference Materials – its 1st

25 years, Accredit. Qual. Assur. 6, 226–235 (2001)

3.52 ISO: ISO 6506-1, Metallic Materials – Brinell Hard-

ness Test - Part 1: Test Method (ISO, Geneva

2005)

3.53 ISO: ISO 6507-1, Metallic Materials – Vickers Hard-

ness Test - Part 1: Test Method (ISO, Geneva

2005)

3.54 ISO: ISO 6508-1, Metallic Materials – Rockwell

Hardness Test - Part 1: Test Method (ISO, Geneva

2005)

3.55 ISO: ISO 6507-2, Metallic Materials – Vickers Hardness

Test - Part 2: Veriﬁcation and Calibration of Testing

Machines (ISO, Geneva 2005)

3.56 ISO: ISO 148-1, Metallic Materials – Charpy Pendulum

Impact Test – Part 1: Test Method (ISO, Geneva 2009)

3.57 ISO: ISO 148-2, Metallic Materials – Charpy Pendulum

Impact Test – Part 2: Veriﬁcation of Testing Machines

(ISO, Geneva 2008)

3.58 ISO: ISO 148-3, Metallic Materials – Charpy Pendulum

Impact Test – Part 3: Preparation and Character-

ization of Charpy V-Notch Test Pieces for Indirect

Veriﬁcation of Pendulum Impact Machines (ISO,

Geneva 2008)

3.59 ISO: ISO Guide 35, Reference Materials – General and

Statistical Principles for Certiﬁcation (ISO, Geneva

2006)

3.60 ISO: ISO 6892-1, Metallic Materials – Tensile Testing

– Part 1: Method of Test at Room Temperature (ISO,

Geneva 2009)

3.61 ISO: ISO 5725-6, Accuracy (Trueness and Precision)

of Measurement Methods and Results – Part 6: Use

in Practice of Accuracy Values (ISO 5725-6:1994 In-

cluding Technical Corrigendum 1:2001) (ISO, Geneva

2002)

3.62 ISO: ISO/IEC Guide 98-3, Uncertainty of Measurement

- Part 3: Guide to the Expression of Uncer-

tainty in Measurement (GUM:1995) (ISO, Geneva

2008)

3.63 JCGM 200: International Vocabulary of Metrology

– Basic and General Concepts and Associated

Terms (VIM) (JCGM, 2008), http://www.bipm.org/en/

publications/guides/vim.html (identical to ISO Guide

99:2007, VIM, 3rd edn.) (last accessed 14 April 2011)

3.64 EUROLAB Position Paper No. 1/2007: Reference lab-

oratories in the ﬁeld of testing (March 2007)

http://www.eurolab.org/pub/i_pub.html (last ac-

cessed 14 April 2011)

3.65 A. Ono, T. Baba, K. Fujii: Traceable measurements

and data of thermophysical properties for solid ma-

terials: A review, Meas. Sci. Technol. 12, 2023–2030

(2001), (last accessed 14 April 2011)

3.66 ISO: ISO 14192, Gas Analysis – Conversion of Gas

Mixture Composition Data (ISO, Geneva 1998), (last

accessed 14 April 2011)

3.67 EURAMET: EURAMET Guide, Metrology in Short,3rd

edn. (EURAMET, 2008), http://www.euramet.org/

index.php?id=mis (last accessed 14 April 2011)

3.68 ISO: ISO 15195, Clinical Laboratory Medicine – Re-

quirements for Reference Measurement Laboratories

(ISO, Geneva 2003)

3.69 JCGM 101: Evaluation of measurement data – Sup-

plement 1 to the “Guide to the expression of

uncertainty in measurement”, Propagation of dis-

tributions using a Monte Carlo method (JCGM, 2008)

http://www.bipm.org/en/publications/guides/gum.

html (last accessed 14 April 2011)

3.70 IUPAC: IUPAC Compendium of Chemical Termi-

nology (‘Gold Book’), 2nd edn. (IUPAC, 1997),

http://www.iupac.org/indexes/books (last accessed

14 April 2011)

3.71 JCGM 100: Evaluation of measurement data –

Guide to the expression of uncertainty in meas-

urement (JCGM, 2008) (identical to ISO/IEC Guide

98-3:2008 Uncertainty of measurement – Part

3: Guide to the expression of uncertainty in

Part A 3

Quality in Measurement and Testing References 141

measurement (GUM:1995)) http://www.bipm.org/

en/publications/guides/gum.html (last accessed 14

April 2011)

3.72 International Measurement Evaluation Programme

(IMEP) http://irmm.jrc.ec.europa.eu/html/

interlaboratory_comparisons/imep/index.htm (last

accessed 14 April 2011)

3.73 ISO: ISO 78-2 Chemistry – Layout for Standards

– Methods of Chemical Analysis (ISO, Geneva

1999)

3.74 BAM Federal Institute for Materials Research and

Testing (Berlin): Catalogue of Reference Procedures

http://www.bam.de/en/fachthemen/

referenzverfahren/index.htm (contact person: M.

Hedrich, BAM) (last accessed 14 April 2011)

3.75 BIPM: Key comparison database – Appendix B (Key

and supplementary comparisons) http://kcdb.bipm.

org/ (contact person: C. Thomas, BIPM) (last accessed

14 April 2011)

3.76 BIPM: Key comparison database – Appendix C (Cali-

bration and measurement capabilities)

http://kcdb.bipm.org/ (contact person: C. Thomas,

BIPM) (last accessed 14 April 2011)

3.77 Versailles Project on Advanced Materials and Stan-

dards (VAMAS): http://www.vamas.org/(chair per-

son: G. Sims, NPL)

3.78 CIPM: 97th Meeting 2008, Report of the CIPM

ad hoc Working Group on Materials Metrol-

ogy (WGMM), CIPM/08-WGMM “Evolving Need for

Metrology in Material Property Measurements”

http://www.bipm.org/en/committees/cipm/

3.79 S. Bennett, J. Valdés: Materials metrology, Metrolo-

gia 47(2), S1–S193 (2010), Special edition on Materials

metrology

Part A 3

143

Chemical

Part B

Part B Chemical and Microstructural Analysis

4 Analytical Chemistry

Willie E. May, Gaithersburg, USA

Richard R. Cavanagh, Gaithersburg, USA

Gregory C. Turk, Gaithersburg, USA

Michael Winchester, Gaithersburg, USA

John Travis, Gaithersburg, USA

Melody V. Smith, Gaithersburg, USA

Paul DeRose, Gaithersburg, USA

Steven J. Choquette, Gaithersburg, USA

Gary W. Kramer, Gaithersburg, USA

John R. Sieber, Gaithersburg, USA

Robert R. Greenberg, Gaithersburg, USA

Richard Lindstrom, Gaithersburg, USA

George Lamaze, Gaithersburg, USA

Rolf Zeisler, Gaithersburg, USA

Michele Schantz, Gaithersburg, USA

Lane Sander, Gaithersburg, USA

Karen W. Phinney, Gaithersburg, USA

Michael Welch, Gaithersburg, USA

Thomas Vetter, Gaithersburg, USA

Kenneth W. Pratt, Gaithersburg, USA

John H. J. Scott, Gaithersburg, USA

John Small, Gaithersburg, USA

Scott Wight, Gaithersburg, USA

Stephan J. Stranick, Gaithersburg, USA

Ralf Matschat, Berlin, Germany

Peter Reich, Berlin, Germany

5 Nanoscopic Architecture and Microstructure

Koji Maeda, Tokyo, Japan

Hiroshi Mizubayashi, Tsukuba, Japan

6 Surface and Interface Characterization

Martin Seah, Teddington, UK

Leonardo De Chiffre, Kgs. Lyngby, Denmark

145

Analytical Che

4. Analytical Chemistry

Measurements of the chemical compositions of

materials and the levels of certain substances

in them are vital when assessing and improv-

ing public health, safety and the environment,

are necessary to ensure trade equity, and are re-

quired when monitoring and improving industrial

products and services. Chemical measurements

play a crucial role in most areas of the economy,

including healthcare, food and nutrition, agricul-

ture, environmental technologies, chemicals and

materials, instrumentation, electronics, forensics,

energy, and transportation.

This chapter presents a broad overview of the

analytical techniques that can be used to per-

form the higher order chemical characterization

of materials. Techniques covered include mass

spectrometry, molecular spectrometry, atomic

spectrometry, nuclear analytical methods, chro-

matographic methods and classical chemical

methods.

For each technique, information is provided

on the principle(s) of operation, the scope of the

technique, the nature of the sample that can be

used, qualitative analysis, traceable quantitative

analysis, and key references. Examples of repre-

sentative data are provided for each technique,

where possible.

4.1 Bulk Chemical Characterization .............. 145

4.1.1 Mass Spectrometry ....................... 145

4.1.2 Molecular Spectrometry................. 147

4.1.3 Atomic Spectrometry..................... 156

4.1.4 Nuclear Analytical Methods ........... 161

4.1.5 Chromatographic Methods ............ 168

4.1.6 Classical Chemical Methods............ 173

4.2 Microanalytical Chemical

Characterization ................................... 179

4.2.1 Analytical Electron Microscopy

(AEM) .......................................... 179

4.2.2 Electron Probe X-ray Microanalysis. 180

4.2.3 Scanning Auger Electron Microscopy 183

4.2.4 Environmental Scanning Electron

Microscope .................................. 185

4.2.5 Infrared and Raman Microanalysis . 186

4.3 Inorganic Analytical Chemistry:

Short Surveys of Analytical

Bulk Methods ....................................... 189

4.3.1 Inorganic Mass Spectrometry ......... 190

4.3.2 Optical Atomic Spectrometry .......... 192

4.3.3 X-ray Fluorescence Spectrometry

(XRF)........................................... 192

4.3.4 Neutron Activation Analysis (NAA)

and Photon Activation Analysis

(PAA) .......................................... 194

4.4 Compound and Molecular Speciﬁc

Analysis: Short Surveys

of Analytical Methods ........................... 195

4.5 National Primary Standards –

An Example to Establish Metrological

Traceability in Elemental Analysis .......... 198

References .................................................. 199

4.1 Bulk Chemical Characterization

4.1.1 Mass Spectrometry

Inductively Coupled Plasma Mass Spectrometry

(ICP-MS)

Principles of the Technique. The inductively cou-

pled plasma (ICP) associated with this technique is

an atmospheric-pressure argon plasma that is produced

in a quartz torch connected to a radiofrequency (RF)

generator. Operating RF powers are typically between

1000 and 1500 W. The aqueous liquid sample solution

is injected as an aerosol into the axial channel of the

ICP, where temperatures on the order of 7000 K pre-

vail. Here the sample is decomposed into its constituent

elements, which are ionized. The ions are differentially

Part B 4

146 Part B Chemical and Microstructural Analysis

pumped into a mass spectrometer (MS) through a sam-

pling cone and skimmer. The relative ion count rates

are used to gauge the relative concentrations of the el-

ements in the sample. The most common instruments

use quadrupole mass spectrometers with unit mass res-

olution capabilities. Higher resolution magnetic sector

mass spectrometers are also available.

Scope. ICP-MS is used primarily for quantitative el-

emental analysis, in other words to determine the

concentrations of speciﬁc elements in a sample. It

is also used to measure elemental isotope ratios. It

is roughly 1000 times more sensitive than ICP-atomic

emission spectrometry (AES), making it very suitable

for trace metal analysis at ng/g and even pg/g solution

concentrations. It is widely used in the semiconductor

industry to test high-purity production chemicals. It is

also heavily used for the environmental monitoring of

water and soil samples. ICP-MS is used in geological

studies, including isotope ratio studies.

Nature of the Sample. In the most common situations,

samples are introduced into the ICP as solutions. If the

sample being analyzed is a solid, it must ﬁrst be dis-

solved. This typically involves dissolving a 0.1 g sample

in 100 mL of acidiﬁed aqueous solution. Dissolving

most samples will require hot concentrated mineral

acids.

An alternative sample introduction system uses laser

ablation of solid samples to generate an aerosol of sam-

ple particles, which can be injected directly into the

ICP.

Qualitative Analysis. Speciﬁc elements are identiﬁed

based on the known mass/charge ratios and isotopic

patterns of the elements.

Traceable Quantitative Analysis. For systems using

solution sample introduction, the ICP-MS instrumen-

tation must be calibrated using solutions containing

known concentrations of the analyte elements. Such cal-

ibration solutions are available from many commercial

suppliers. These solutions are often traceable to one of

asetofNIST single-element solution standard refer-

ence materials. The analysis of complex samples can

be susceptible to matrix effects (the combined effect

that all of the species present in the sample have on

the mass spectrometric signal of the analyte). This will

lead to measurement bias if the calibration solutions

are not matched to the matrix of the sample being an-

alyzed. The method of standard additions is an effective

strategy for dealing with matrix effects. Use of an in-

ternal standard will also reduce susceptibility to matrix

interferences.

For high-accuracy work, quantitation can also be ac-

complished through isotope dilution. In this procedure

the isotope ratio of a pair of analyte isotopes is per-

turbed by spiking the sample with a known amount of

a solution that is enriched in the concentration of an iso-

tope of the element that is naturally not very abundant.

The degree of perturbation of the isotope ratio depends

on the concentration of the analyte element present in

the sample before being spiked, and the concentration

can be calculated by measuring the perturbed isotope

ratio.

Isobaric interferences occur when two or more ionic

species with nominally the same mass-to-charge ratio

are present in the ICP. The argon plasma is the source

of the most severe of these interferences. For example,

Ar interferes with

Ca, and

O interferes with

Fe in quadrupole systems. The latter example can be

resolved with high-resolution systems.

Calibration of systems using sample introduction

based on laser ablation is more difﬁcult. The laser ab-

lation process is very matrix-dependent, and calibration

requires the use of solid standards that match the char-

acteristics of the sample quite closely.

Certiﬁed reference materials are available in a wide

variety of sample matrix types from NIST and other

sources. These CRMs should be used to validate ICP-

MS methods.

Glow Discharge Mass Spectrometry (GD-MS)

Principles of the Technique. A glow discharge is

a reduced-pressure, inert gas plasma maintained be-

tween two electrodes. Argon is typically used at

absolute pressures of a few hundred Pascals or less,

and the solid sample serves as the cathode in the cir-

cuit. When the discharge is ignited, Ar

ions formed in

the plasma are accelerated toward the sample surface by

means of electrical ﬁelds. A substantial fraction of these

ions strike the surface of the sample with enough

kinetic energy to eject sample atoms from the surface.

In this way, the solid sample is directly atomized. Once

in the plasma, sputtered atoms may be ionized through

collisions with metastable Ar atoms (Penning ioniza-

tion) or energetic electrons (electron impact ionization).

The ions generated are extracted from the plasma and

directed into a mass analyzer with one or more de-

tectors. The ions are separated and detected according

to the mass-to-charge (m/z) ratios, resulting in a glow

discharge mass spectrum.

Part B 4.1

Analytical Chemistry 4.1 Bulk Chemical Characterization 147

GD-MS instruments usually employ quadrupole or

double-focusing magnetic sector mass analyzers, al-

though other types have also been reported (such as

time-of-ﬂight (TOF), ion cyclotron resonance (ICR),

and ion traps). To date, there has only been one

commercial GD-MS instrument that can truly be said

to have been successful in the marketplace. This is

the VG-9000 double-focusing glow discharge mass

spectrometer (Thermo Elemental, Cambridge, United

Kingdom), costing more than $ 500 000 (To describe

experimental procedures adequately, it is occasionally

necessary to identify commercial products by manu-

facturer’s name or labels. In no instance does such

identiﬁcation imply endorsement by the National In-

stitute of Standards and Technology, nor does it imply

that the particular products or equipment are necessar-

ily the best available for that purpose). The number

of VG-9000 instruments in use around the world is

probably somewhere between 40 and 60. Some other

double-focusing instruments, as well as quadrupole in-

struments, often custom-built by the user, are also

employed.

Scope. Glow discharge devices used in GD-MS may

be powered by either a direct-current (DC) or radiofre-

quency (RF) power supply. In DC-GD-MS, the sample

must be electrically conductive, since current must pass

through it. Therefore, DC-GD-MS is applicable to con-

ductive bulk samples. In principle, the technique is also

applicable to samples consisting of conductive layered

materials (such as thin ﬁlms on surfaces). In such a case,

registration of ion intensities as surface layers are sput-

tered away results in a depth proﬁle of the sample.

However, very little work in this area has been reported

so far. RF-GD-MS overcomes the restriction to conduc-

tive sample types, because in this conﬁguration it is not

necessary for net current to ﬂow through the sample. As

a result, RF-GD-MS can be applied to electrically in-

sulating bulk solids and coated surfaces with insulating

substrates and/or layers.

The greatest strengths of GD-MS,whetherDC or

RF, are the high sensitivities and low limits of detection

available (sub- to low ng/g range directly in the solid

state). Owing to these characteristics, the technique

has been most widely applied for purity assessments

of highly-pure, solid materials, such as those used in

the semiconductor industry. The ability to detect H, O

and N is also advantageous for this application. Iso-

baric interferences are not generally problematic in

GD-MS, unless low-resolution mass analyzers (such as

quadrupoles, which have only unit resolution) are used.

Disadvantages of GD-MS include the fact that ma-

trix effects, while relatively mild compared to many

other direct solid techniques, are nonetheless present.

Matrix effects manifest themselves mainly as overall

sputtering rates that vary from matrix to matrix. For-

tunately, even though this is true, once sputtering has

reached steady state for a given sample, the relative

ﬂuxes of sputtered atoms accurately reﬂects the sto-

ichiometry of that sample. Another disadvantage of

GD-MS is that it is inherently a relative technique,

requiring reference materials for calibration. Unfortu-

nately, reference materials with certiﬁed values in the

mass fraction range of greatest interest (< 1mg/g) are

rare. As a result, GD-MS calibration can only be ac-

complished to the degree allowed by available reference

materials.

Nature of the Sample. As noted above, samples

amenable to GD-MS analysis include bulk solids and

layered surfaces. Bulk solids are often machined into

pins for analysis, although ﬂat samples can also be em-

ployed.

Qualitative Analysis. Calibration of a GD-MS instru-

ment consists of measuring relative sensitivity factors

(RSFs) for the analytes. RSFs are generated by mea-

suring the signal levels for suitable reference materials.

When suitable reference materials are lacking, GD-MS

cannot be calibrated, resulting in qualitative analysis.

Nonetheless, given the very low limits of detection, the

technique ﬁnds much use in this mode.

Traceable Quantitative Analysis. Quantitative GD-MS

analysis (with accuracies in the range of ±30% relative,

for example) is performed by employing RSFs gener-

ated from matrix-matched reference materials. If RSFs

must be developed from non-matrix-matched reference

materials, then GD-MS becomes a semiquantitative

technique (giving accuracies within a factor of 2 for

example). In either case, the calibrants constitute the

traceability link to the SI.

Several review articles [4.1–8] are available.

4.1.2 Molecular Spectrometry

Traceability in UV/Vis Molecular Absorption

Spectrometry

Principles of the Technique. Molecular absorption

spectrometry in the ultraviolet and visible spectral re-

gion, often simply known as UV/Vis, is one of the

oldest and most mature instrumental methods of chem-

Part B 4.1