Metrology in Chemistry and
Traceability of Analytical
Measurement Results
Ioannis Papadakis
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Index
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Needs for Metrology
Fundamentals of Metrology
International Measurement System
Traceability of analytical
measurements results
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Metrology –
Science of Measurement
 metrology includes all aspects both
theoretical and practical with reference
to measurements, whatever their
uncertainty, and in whatever fields of
science or technology they occur.
Source: International Vocabulary of Basic and General Terms in
Metrology, ISO, 1993
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
What is a Measurement ?
 measurement is a ratio of
an “unknown” to “known”
quantity
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Examples
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Mars Climate Orbiter
...confusion about units leads to crash...
 On 23 September 1999 the Mars Climate Orbiter,one
of the missions in a long-term program of Mars
exploration, burned out completely.
 The accident was not due to a technical problem, but
the result of the different measurement units used by
the NASA teams.
 One team used the metric system for spacecraft
operation, while the other used the English units. This
information was critical to the maneuvers required to
position the spacecraft in the proper Mars orbit and
led to the loss of the orbiter.
 The fate of the Mars Climate Orbiter clearly shows
the need for standardization.
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Difference $ 10 Million
 A subsidiary of an oil company in the Far East analysed a
batch of petrol. Their local lab established that the gum
content (components in the gasoline that polymerize during
combustion) was too much high.
 On the basis of this analysis the company sold the batch to a
trader for a much lower price.
 The trader asked a second lab to perform an analysis in
order to find out what he could do with the off-spec petrol.
 He was very pleasantly surprised to find that the gasoline
was actually on-spec and he was able to make a healthy
profit selling the batch for the normal price.
 The oil company only found out much later that the problem
was not the petrol, but an error at their own lab. By then this
error had already cost them $ 10 million.
Source: Footprint of the Meter, NMi Communicabus, 1999
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Alaska Pipeline
 The 800-mile trans-Alaska pipeline pumps oil from the northern
coast to the southern border of Alaska.
 Construction started in 1973 and was completed 4 years later.
 The pipeline was originally budgeted $ 900 million, but the cost
escalated to exceed $ billion.
 A steel manufacturer was awarded the multimillion dollar
contract to supply steel for the pipeline with S content of less
than 0.005%.
 When several of the joint welds in the pipeline began to fail, it
became clear that the S content was much higher than
specified.
 The poor quality of the steel, in part due to inadequate or lack of
measurements, set the project back several millions of dollars,
once again emphasizing the need for accurate measurements.
Source: Footprint of the Meter,NMi Communicabus, 1999
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Cholesterol Measurements
 A high measurements uncertainty for
cholesterol can lead to an unnecessary costly
treatment or a higher health risk.
 Reducing the measurement uncertainty from
23.7% in 1949 to 5% in 1995, saves to the
Unites States alone $ 100 million every year
in health care costs.
 Standard reference materials played an
important role in lowering the measurement
uncertainty.
Source: CITAC ‘99 Japan Symposium, Tsukuba, November 1999,
W. May (NIST-USA)
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Importance of Measurements
 economic
 political
 social
 environmental
 scientific
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Unreliable Measurements
Lead to:
 duplication of measurements
 use of extra resources
 lack of trust
 negative economic impact
 disasters/accidents
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Metrology Users
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industry (e.g. manufacturing)
commerce (e.g. disputes)
governments (e.g law implementation)
health and safety
environment protection
science / research
military services (e.g. navigation)
communications
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
… Lack of Standard …
King’s foot
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
… Lack of Standard …
Variations of One Unit of Length (Ell)
 The “ell”, a unit originating from the
custom of measuring cloth using one’s
forearms, existed in many countries.
 In order to make trade possible
at all in these days, conversion tables
were used.
Source: Footprint of the Meter, NMi Communicabus, 1999
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
… Lack of Standard …
country
England
Scotland
Germany
Russia
ell(m)
1.14
0.94
0.6
0.5
city
Vienna(A)
Bruges (B)
Amsterdam (NL)
ell(m)
0.78
0.70
0.69
Source: Footprint of the Meter, NMi Communicabus, 1999
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Meter Convention
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diplomatic treaty
20th May 1875, in Paris
SI system
51 signatory countries
6 associate members
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Meter Convention
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international uniformity in measurement
common system of units
equivalent measurement standards
harmonised laws and regulations
mutual recognition of measurements
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
SI
International System
of Units
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
SI Base Quantities
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quantity
length
mass
time
electric current
thermodynamic temperature
amount of substance
luminous intensity
unit
symbol
metre
m
kilogram
kg
second
s
ampere
A
kelvin
K
mole
mol
candela
cd
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
SI Derived Quantities
quantity
 speed, velocity
 density
 concentration
(of amount of
substance)
unit
symbol
metre per second
m/s
kilogram per cubic metre kg/m3
mole per cubic metre
mol/m3
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Chemistry in SI
 amount of substance (AoS)
 agreed on 1971
 Mole (mol)
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Traceability of Length
Measurements
Length corresponding to X number of
wavelengths of an I2 stabilized laser
value
value
value
calibration 2
calibration 1
tape measure
value
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
analytical measurements
need to be comparable
in time and space
traceability is the best
way to achieve this
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Traceability of
Chemical Measurements
SI unit for amount of substance
value
value
value
Reference Standard
Working Standard
amount content of X
compound in solution
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Problems...
 absence of reference standards
 absence of links to common basis
 appropriate use of standards
by laboratories
 appropriate use of uncertainty
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Traceability - Definition
Traceability is defined as the property of
the result of a measurement or the value
of a standard whereby it can be related to
stated references, usually national or
international standards, through an
unbroken chain of comparisons all having
stated uncertainties.
Source: International Vocabulary of Basic and General Terms in Metrology
(ISO, 1993)
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Stated References
 determination of amount of substance
requires measurements of different
properties
 sample mass
mass reference
 analyte identity
DB of known compounds
 analyte quantitation reference material
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Stated Uncertainty
 interval around the measurement
result
 uncertanty budget including:
 uncertainties carried by the
references
 uncertainties introduced by the
measurement process
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Questions ?
 Is the upper limit or lower limit of an
uncertainty statement close to a legal limit, or
does it reach beyond such a limit?
 How much overlap is there between the
uncertainty statement of similar
measurements on the same or similar
samples?
 Do the uncertainty statements of
measurements from different labs on the
same sample overlap?
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Stated Uncertainty
 it is less important to have
a particularly small uncertainty,
 but more pertinent to have a
good estimate of the uncertainty
for answering such questions
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Stated Uncertainty
usually the contribution of the
uncertainties carried by the
references to the total uncertainty is
small relative the contributions that
originate from the measurement
process
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
 in such cases results can be improved
(in terms of uncertainty) only if
measurement process is improved
 thus, chemists are urged to concentrate
on the measurement process they
operate, which involves a thorough
validation leading to valid results
including a realistic uncertainty
statement
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Reference Materials
 values carried by reference materials
should be traceable to other references
 the same features which are valid for
the analytical laboratories are also valid
for the reference materials producers
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
More Information
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www.bipm.org
www.euromet.ch
www.citac.ws
www.eurachem.org
www.eurolab.bam.de
www.irmm.jrc.be
www.nist.gov
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching
Things to Remember
 metrology in chemistry is still “young”
 there is a lot to learn
 traceability is not an aim by itself
but it helps achieving reliable results
 traceability can only be claimed if
uncertainty statement includes all
the uncertainties from references
and the measurement procedure
Papadakis, I.: Metrology in Chemistry and Traceability
© Springer-Verlag Berlin Heidelberg 2003
In: Wenclawiak, Koch, Hadjicostas (eds.)
Quality Assurance in Analytical Chemistry – Training and Teaching