Glossary of Analytical
Chemistry Terms (GAT)
Bernd Wenclawiak
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Glossary
 Remark: Teaching and Learning terms is
boring, but necessary!
 Why is it necessary to know the meaning of a
term?
Because a lot of expressions are not common
in everyday life or might be interpreted
differently
 In scientific and technical work it is necessary
that all people use the same “language”.
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Glossary
 Who defines a term?
 In chemistry there is IUPAC
IUPAC coordinates the international work of
harmonization
 In the field of metrology many different
organizations work together:
ISO, IEC , BIPM, OIML, IUPAC, IUPAP, IFCC
They jointly published the VIM
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Glossary - Vocabularies
 A Vocabulary contains general terms and definitions
 International Vocabulary of Basic and General Terms in
Metrology (VIM)
 International Vocabulary of Terms in Legal Metrology (VIML).
 Guide to the Expression of Uncertainty in Measurement
(GUM)
 ISO 3534-1:1993. “Statistics - Vocabulary and symbols - Part
1: Probability and general statistical terms”.
 ISO 3534-2:1993. “Statistics - Vocabulary and symbols - Part
2: Statistical quality control”.
 ISO 3534-3:1985. “Statistics - Vocabulary and symbols - Part
3: Design of experiments”.
 ISO 8402:1994, “Quality - Vocabulary”.
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Glossary
 The bibliography comprises four
different types of documents:
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Guides
Standards
Books
Articles (in scientific journals)
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Glossary - Standardization
Organizations
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International:
European:
German:
Great Britain:
United States:
ISO (www.iso.ch)
EN (www.cenorm.be)
DIN (www.din.de)
BS (www.bsi.org.uk)
ASTM (www.astm.org)
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Glossary – SI System
 The International System of Units (SI)
differentiates two classes of units:
Base Units and Derived Units.
 The Base Units are:
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Unit
metre
kilogram
second
ampere
kelvin
mole
Candela
Quantity
length
mass
time
electric current
thermodynamic temperature
amount of substance
luminous intensity
Symbol
m
kg
s
A
K
mol
cd
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Glossary - Important
Organisations
 European
 EURACHEM - Co-operation for Analytical Chemistry in
Europe
 EUROLAB - Organization for Testing in Europe
 EA - European Co-Operation for Accreditation
 EUROMET - A European Collaboration in Measurement
Standards IRMM Institute for Reference Materials and
Measurements
 International
 CITAC - Co-Operation on International Traceability in
Analytical Chemistry
 NIST – (US) National Institute of Standards and Technology
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Glossary - Terms Related to:
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General
Statistics
Validation
Measurement
Error
Uncertainty
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Glossary of General Terms
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Accreditation
Accuracy
Accuracy of measurement
Accuracy of a Measuring
Instrument
Audit
Bias
Certification
Fitness for Purpose
Influence quantity
Precision
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Quality
Quality Assurance
Quality Control
Internal Quality Control
Standard
Trueness
True Value
Conventional True
Value
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms - Accreditation
 Procedure by which an authoritative
body gives formal recognition that a
body or person is competent to carry
out specific tasks
(ISO/CASCO 193 (Rev. 2), & ISO Guide 2:1996)
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms - Accuracy
 The closeness of agreement between the
result of a measurement and the true
value of the measurand
 Accuracy is a measure which combines precision and
trueness (i.e. the effects of random and systematic
factors)
 Suppose the results produced by the application of a
method show zero or very low bias (i.e. are "true"),
their accuracy becomes equivalent to their precision
If the precision is poor, any particular result will be
inaccurate
 If a method shows a high bias, even results with a
high precision are inaccurate
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms –
Accuracy of Measurement
 The closeness of the agreement
between the result of a measurement
and a true value of the measurand
[VIM]
 "Accuracy" is a qualitative concept.
 The term "precision" should not be used for
"accuracy".
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms - Accuracy
(of a Measuring Instrument)
 Ability of a measuring instrument to
give responses close to a true value.
[IUPAC Orange Book]
 In this context accuracy is a qualitative
concept.
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms - Audit
 Quality Audit: ‘A systematic and independent
examination to determine whether quality
activities and related results comply with
planned arrangements and whether these
arrangements are implemented effectively
and are suitable to achieve objectives’
(ISO 8402 - 1994).
 External Audit also known as assessment
 Internal
 audit
 review
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms - Bias
 The difference between the expectation
of the test results and an accepted
reference value.
 Characterises the systematic error in a
given analytical procedure and is the
(positive or negative) deviation of the
mean analytical result from the (known
or assumed) true value.
[IUPAC Compendium of Chemical Technology, 1985]
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms - Certification
 Procedure by which a third party gives
written assurance that a product,
process or service conforms to specified
requirements
(ISO/CASCO 193 (Rev. 2), 4.1.2, & ISO
Guide2:1996, 15.1.2)
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms –
Fitness for Purpose
 Degree to which data produced by a
measurement process enables a user to
make technically and administratively
correct decisions for a stated purpose.
[IUPAC Orange Book]
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms –
Influence Quantity
 A quantity that is not the measurand but
that affects the result of the
measurement
[VIM].
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms - Precision
 The closeness of agreement between independent
test results obtained under stipulated conditions
 The precision statement can be made for any set of
measurements which have been performed under stated
experimental conditions which can be chosen freely
 The precision of a set of results of measurements can be
quantified as a standard deviation
 Precise results on the same analyte are characterized by
small statistical variability
 This would then result in a small standard deviation,
range or interquartile distance, all being measures of
precision
 Precision is a characteristic of a set of data
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms - Quality
 „ ...quality is the totality of features of a
unit as regards its suitability to fulfill
specified and expected requirements.“
(ISO 8402)
 A very important remark:
“No data is better than poor data”
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms –
Quality - What does that Mean?
 „Quality means that the customer
comes back, and not the product.“
 Quality and Liability are tightly
connected
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms –
Quality Assurance
 All those planned and systematic
activities implemented within the quality
system, and demonstrated as needed,
to provide adequate confidence that an
entity will fulfil requirements for quality.
[ISO 8402:1994]
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms – Quality Control
 The operational techniques and
activities that are used to fulfil
requirements of quality.
[ISO 8402:1994]
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms –
Internal Quality Control
 Set of procedures undertaken by
laboratory staff for the continuous
monitoring of operations and the results
of measurements in order to decide
whether results are reliable enough to
be released.
[IUPAC Orange Book]
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms – Standard
 was used for widely adopted
procedures, specifications, technical
recommandations etc.
 and also to chemical or physical
standards, which are used for
calibration purposes.
 standard is used here only in the sense
of writtenstandard
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms – Trueness
 The closeness of agreement between the average
value obtained from a large series of test results and
the conventional true value
 A true result is a result with little (or ideally no)
systematical error without respect to the statistics of the
series of results
 Perfect trueness cannot be achieved, so trueness in its
analytical meaning is always trueness within certain limits
 These limits may be narrow at a high concentration level
and wide at the trace level
 It is important to note the difference between accuracy
and trueness.
 The lack of trueness is called bias
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms – True Value
 Value which charcterizes a quantity
perfectly defined in the conditions which
exist when that quantity is considered.
 The true value is a theoretical concept and, in
general, cannot be known exactly
 It is a value that would be obtained by a
perfect measurement
 True values are by nature indeterminate
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
General Terms –
Conventional True Value
 Value attributed to a particular quantity and
accepted, sometimes by convention, as having an
uncertainty appropriate for a given purpose
 A result obtained by using several independent methods
in several expert laboratories on one measurand is
regarded as conventional true value of a quantity even if
it is not the "true" value
 A conventional true value is in general, regarded as
sufficiently close to the true value for the difference to be
insignificant for the given purpose.
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Glossary on Statistical Terms
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Arithmetic mean
Distribution functions
Normal distribution
Rectangular distribution
Triangular distribution
Poisson distribution
Binomial distribution
Estimate
 Probabilty
 Standard Deviation
 Sample Standard
Deviation
 Standard deviation of
the mean
 Relative Standard
Deviation (RSD)
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Statistical Terms –
Distribution Functions
 Normal distribution continuous distribution
 Rectangular distribution
 Triangular distribution
 Poisson distribution discrete function
 Binomial distribution discrete function
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Glossary on Validation Terms
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Calibration Curve
linear least squares calibration
Cross Reactivity
Discrimination
Discrimination Threshold
Limiting Mean
Limit of Detection
Minimum Detectable Net
Concentration
Limit of Decision
Limit of Determination
Limit of Quantitation
Limit of Reporting
Linearity
Proficiency Testing
Range - Measuring and working
Recovery
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Reference Material
Certified Reference Material
Repeatability
Repeatability of Results of Measurements
Repeatability of a Measuring Instrument
Repeatability Standard Deviation
Repeatability Limit r
Reproducibility
Reproducibility Standard Deviation
Reproducibility Limit R
Ruggedness Test
Selectivity
Selectivity in Analysis
Sensitivity
Specificity
Validation
Method Validation
Verification
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Validation Terms
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Validation
Method Validation
Instrument Validation
Verification
Proficiency Testing
 Limiting Mean
 Limit of Detection
 Minimum Detectable
Net Concentration
 Limit of Quantitation
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Validation Terms
 Calibration Curve
 Graphical representation of measuring
signal as a function of quantity of analyte.
[AOAC]
 Linear least squares calibration
 calibration with the method of minimizing
the least squares
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Validation Terms
 Linearity
 Defines the ability of the method to obtain
test results proportional to the
concentration of analyte.
 The Linear Range is by inference the
range of analyte concentrations over which
the method gives test results proportional
to the concentration of the analyte.
[AOAC]
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Measurement Terms
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Measurand
Measurement
Measurement Procedure
Method of Measurement
Response Time
Result of a Measurement
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Measurement Terms Measurement Standard
 measurement standard is used to
describe chemical or physical standards
used for calibration purposes such as:
chemicals of established purity and their
corresponding solutions of known
concentration, UV filter, weights, etc.
They are also called: reference material
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Error Terms
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Error of Measurement
Random Error
Systematic Error
False Negatives/Positives
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Error Terms - Error (of a Result)
 The test result minus the conventional
true value
 error is the sum of random and
systematic errors
 If a measurement is repeated, each
individual result will have its own
associated error
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Error Terms–
False Negatives / Positives
 For qualitative methods the false
positives/negatives rate may be determined.
 Data from a confirmatory method comparison
should be provided if such method(s) is
applicable to the same matrix(es) and
concentration range(s).
 In the absence of a method comparison,
populations of negative and positive fortified
samples must be analysed.
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Uncertainty Terms
 Uncertainty (of Measurement)
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Standard Uncertainty
Combined Standard Uncertainty
Expanded Uncertainty
Coverage Factor
Type A evaluation (of uncertainty)
Type B evaluation (of uncertainty)
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Uncertainty Terms Measurement Uncertainty
 Parameter, associated with the result of a measurement,
that characterizes the dispersion of the values that could
reasonably be attributed to the measurand
 Uncertainty sets the limits within which a result is
regarded accurate, I.e. precise and true
 Uncertainty of measurement comprises, in general, many
components. Some of these components may be
evaluated from the statistical distribution of the results of
series of measurements and can be characterized by
experimental standard deviations
 The other components, which can also be characterized
by standard deviations, are evaluated from assumed
probability distributions based on experience or other
information.
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Uncertainty Terms – Traceability
 Property of the result of a measurement
or the value of a standard whereby it
can be related with:
 a stated uncertainty,
 to stated references (usually national or
international standards)
Wenclawiak, B.: Glossary of Analytical Chemistry Terms
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching