papadakis, i.: metrology in chemistry and traceability © springer-verlag berlin heidelberg 2003 in:...
TRANSCRIPT
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
Metrology in Chemistry and Traceability of Analytical
Measurement Results
Ioannis Papadakis
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
Index
Needs for Metrology Fundamentals of Metrology International Measurement System Traceability of analytical
measurements results
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
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
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
What is a Measurement ?
measurement is a ratio of an “unknown” to “known” quantity
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
Examples
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
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.
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
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
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
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
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
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)
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
Importance of Measurements
economic political social environmental scientific
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
Unreliable Measurements Lead to:
duplication of measurements use of extra resources lack of trust negative economic impact disasters/accidents
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
Metrology Users
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
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
… Lack of Standard …
King’s foot
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
… Lack of Standard …Variations of One Unit of Length (Ell)
The “ell”, a unit originating from thecustom of measuring cloth using one’sforearms, existed in many countries.
In order to make trade possibleat all in these days, conversion tableswere used.
Source: Footprint of the Meter, NMi Communicabus, 1999
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
… Lack of Standard …
country ell(m)
England 1.14
Scotland 0.94
Germany 0.6
Russia 0.5
cityell(m)
Vienna(A) 0.78
Bruges (B) 0.70
Amsterdam (NL) 0.69
Source: Footprint of the Meter, NMi Communicabus, 1999
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
Meter Convention
diplomatic treaty 20th May 1875, in Paris SI system 51 signatory countries 6 associate members
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
Meter Convention
international uniformity in measurement common system of units equivalent measurement standards harmonised laws and regulations mutual recognition of measurements
aims
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
SI
International Systemof Units
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
SI Base Quantities
quantity unit symbol length metre m mass kilogram kg time second s electric current ampere A thermodynamic temperature kelvin K amount of substance mole mol luminous intensity candela cd
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
SI Derived Quantities
quantity unit symbol speed, velocity metre per second m/s density kilogram per cubic metre kg/m3
concentration mole per cubic metre mol/m3
(of amount ofsubstance)
examples
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
Chemistry in SI
amount of substance (AoS) agreed on 1971 Mole (mol)
it is
quite
new !
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
Length corresponding to X number of wavelengths of an I2 stabilized laser
tape measure
calibration 1
calibration 2
value
value
value
value
Traceability of Length Measurements
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
analytical measurementsneed to be comparable
in time and space
traceability is the bestway to achieve this
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
SI unit for amount of substance
value
value
value
amount content of Xcompound in solution
Working Standard
Reference Standard
Traceability ofChemical Measurements
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
Problems...
absence of reference standards absence of links to common basis appropriate use of standards
by laboratories appropriate use of uncertainty
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
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)
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
Papadakis, I.: Metrology in Chemistry and Traceability © Springer-Verlag Berlin Heidelberg 2003
Stated References
determination of amount of substancerequires measurements of different properties sample mass mass reference analyte identity DB of known
compounds analyte quantitation reference material
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
Stated Uncertainty
interval around the measurement result
uncertanty budget including: uncertainties carried by the
references uncertainties introduced by the
measurement process
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
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?
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
Stated Uncertainty
it is less important to havea particularly small uncertainty,
but more pertinent to have agood estimate of the uncertaintyfor answering such questions
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
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
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 such cases results can be improved (in terms of uncertainty) only if measurement process is improved
thus, chemists are urged to concentrateon the measurement process they operate, which involves a thorough validation leading to valid results including a realistic uncertainty statement
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
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
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
More Information
www.bipm.org www.euromet.ch www.citac.ws www.eurachem.org www.eurolab.bam.de www.irmm.jrc.be www.nist.gov
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
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 allthe uncertainties from referencesand the measurement procedure