Transcript ASSURANCE DE QUALITE POUR LA DETERMINATION DE …

METROLOGY IN
ENVIRONMENTAL CHEMISTRY
Philippe QUEVAUVILLER
Centre of Excellence on Environmental Analysis and Monitoring
Gdansk, 21st April 2005
Philippe Quevauviller - Metrology
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CONTENT OF THE COURSE
GENERALITIES
- Chemical Metrology - Quality assurance - Environment monitoring - Regulations -
SCIENTIFIC AND TECHNICAL FRAMEWORK
- Methods: selection and validation - Tools for quality: Reference materials - Interlaboratory studies - Examples of European projects -
PERSPECTIVES
- Monitoring - Data quality - Research - Training -
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METROLOGY
- Generalities The metrology is the science of measurements
System covering basic concepts such as traceability, uncertainty, calibration,
validation, etc. of measurements - It must guarantee that analytical data are:
(1) expressed according to recognised units, in principle units of the “Système
International” (SI)
(2) comparable between laboratories and over time
(3) provided to the user(s) with clear information regarding their significance
(uncertainty)
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METROLOGY
- Units of the “Système international (SI)”
• Metric system established in France during the French revolution (standard metre
conserved at BIPM in Sèvres since 1889)
• At the Conférence Générale des Poids et Mesures (CGPM) in 1901: the kilogramme is
declared mass unit, sorting out the the ambiguity between « weight » and « mass »
•Time: The SI unit is the atomic second (since 1968), corresponding to the radiation
between two levels of the basic state of the 133cesium atom
• Temperature: centigrade or Celsius scale (freezing or boiling points of pure water
established at 0 and 100 °C - Kelvin scale (absolute zero at approx. -273 °C)
• Mole: mass of substance, measured in reference to the kilogramme (mass of 12 g of
12carbon = one mole of carbon) - This unit links the atomic/molecular entity of the matter to
a macroscopic scale, through classical chemical reactions
• Derived units: for example, surface, density, pressure, viscosity, etc., the most used
being the volume (defining the litre as « a volume occupied by the mass of 1 kg pure water
at its maximal density, at a standard atmospheric pressured »)
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METROLOGY
- Some definitions (1) • Trueness: « closeness of agreement between the result of a measurement and the true value of the measured value.
The true value is the value that would be obtained by the measurement if the amount could be perfectly determined and
all the errors eliminated »
•Precision : « closeness of agreement between the results of a series of repetitions of analyses of a substance in a
single sample. This term is usually separated into repeatability (same instrument, analyst, location, conditions of
utilisation, and short-term period of time) and reproducibility (variations of conditions, methods, analyst, location).
The data related to precision are generally expressed in the form of standard deviations or, more often, of coefficients
of variation of the mean of results of the measurement series. This should be distinguished from the robustness, which
corresponds to the capacity of the method to remain unaffected by minor changes of the procedure (e.g. reagents or
environment) »
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METROLOGY
- Some definitions (2) • Specificity: « response of a single analyte, not affected by possible interferences »
• Sensitivity: « minimal significant variation of a measurement result »
•Linearity: « capacity of obtaining, in a given interval, results that are directly proportional to the analyte
concentration »
• Limit of detection : « smallest quantity of analyte that may be detected but not quantified (the detection limit is
closely linked to sensitivity and to the stability of the analytical system »
• Limit of determination : « expression of the smallest amount of analyte which may be quantified - This limit is
generally taken as being equivalent to 5 to 10 times the detection limit »
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METROLOGY
- Some definitions (3) -
Traceability : « property of a measurement result or the value of a standard to be linked to established references,
generally national or international standards, through an unbroken chain of comparisons, each having an established
uncertainty »
The comparabilitu of the results is the primary condition The traceability is a tool, which should permit to achieve this comparability.
The references may be SI units, calibrants, reference materials, (written) standards, reference methods - The unbroken
chain of comparisons implies that links are established between the various analytical steps of the method used - The
uncertainty should in principle be calculated at each step and combined (total uncertainty), which is not always
achievable in practice.
Possible « hierarchy » of links: SI Units (e.g. kg, mole) - international transfer standards (ex. kg) - atomic masses pure calibrants of chemical substances - primary methods - Primary (matrix) reference materials - Secondary reference
materials - Routine methods and Laboratory reference materials
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CHEMICAL METROLOGY
- Specific aspects  Influence of sample matrix
 Variety of analytical problems in relation to the millions of substances and thousands
of sample types
 Need of preliminary operations before the analysis (sampling, storage etc.) and
related problems (e.g. stability, homogeneity of samples)
 Needs of tools for the quality control of measurements (e.g. « matrix » reference
materials)
 Specific needs for the validation of methods including various steps
 Difficulties for demonstrating the traceability of results and calculating the total
uncertainty
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QUALITY ASSURANCE
- Chemical analyses DEFINITIONS
Quality: « Characteristics of a product or a service which confer
the aptitude to satisfy the implicit or expressed needs »
Quality assurance : « Preestablished and systematic actions necessary to provide the appropriate confidence
that a product or service will satisfy given requirements related to quality »
Quality Control : « Techniques and operational activities that are used to respond to respond to quality requirements.
It implies activities that both aim to follow a process and to eliminate the causes of failure
with the view of achieving the best economic efficiency »
Quality system: « Organisational structure, covering the responsibilities, procedures and
processes, to implement the quality activities (determining the quality policy of an enterprise) »
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QUALITY ASSURANCE
- User’s needs The results have to be fit to the purpose for the study, as well as the means that
are used (the highest level of accuracy is not systematically required)
Example: Considering the guide value of arsenic in contaminated soils = 40 mg.kg -1
A soil will be considered as contaminated is an analytical result exceeds this guide value.
If the As content is below 10 mg.kg-1, an absolute trueness is not necessary, and it is only necessary to define
the confidence level of the results. The problem will be different if the content is 39 mg.kg -1 or 41 mg.kg-1
A well informed customer will ask (1) if the method is appropriate, (2) if it has
been validated, (3) what are the sources of uncertainty and (4) what is the
confidence level that can be expected from the results. The quality/price ratio of
the analyses will also be considered.
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QUALITY ASSURANCE
- Implications FOOSTUFFS
- Detection of toxic risks - Nutrition -
ENVIRONMENT
- Evaluation of environmental risks - Detection of pollution - Biogeochemical studies -
BIOMEDICAL ANALYSES
- Diagnosis - Biochemical research - Forensic science -
INDUSTRY
- Product quality -
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CONSEQUENCES
OF ANALYTICAL ERRORS
DECISIONS
Food toxicity
(e.g.. dioxins)
Environmental
pollution
(e.g. drinking water)
Medical diagnosis,
forensic science
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Industrial products
(e.g. impact on trade)
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ANALYTICAL ERRORS
- Example -
Dioxins in fly ashes
« There is no democracy in science »
A statistical analysis enables one to study the distribution of a population
of data but it cannot explain the differences between results
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Dioxins in fly ashes
F130
Mean  standard deviation
F121
F119
F118
Lab. 5
45 : 00
50 : 00
55 : 00
Time
(a) Column used for the first time (lab. 5)
F121
F130
F118
(+F119)
( b) Other columns or old DB Dioxin
The majority of the laboratories (b) found a value for F118 (hexaclorodibenzofuran) which was 20 % too high.
Only the laboratory 5 was right.
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ANALYTICAL ERRORS
- Example Heavy metals in lichen
BCR (1992)
Element
Zn
Cu
Hg
Lowest value
(mg/kg)
[Method]
Highest value
(mg/kg)
[Method]
9.7 [AAS]
0.8 [AAS]
0.005 [CVAAS]
283 [ICP]
39 [ICP]
0.551 [CVAAS]
Ratio
29
48
110
Within the two years preceeding this study, around 2000 papers had been published in lichenology.
The results of these studies have been used to evaluate the atmospheric contamination
and to take “appropriate” decisions …...
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ENVIRONMENT MONITORING
- General principles PRINCIPLES
- Definition of the problem (regulations, research?) - Choice of a strategy - Chemical and/or biological analyses - Interpretation and decision -
PARAMETERS
- Media, types of samples analysed (e.g.. Contaminated soils, sediments, waters, biological samples, etc.)
- Substances (regulated or not) (e.g. heavy metals, nutrients, chemical species of element, organic compounds)
OPERATIONS
- Sampling - Treatment / Storage of samples - Analysis - Presentation of the data -
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ENVIRONMENT
MONITORING
- Matrix types (1) WATERS
groundwater, lake waters, rivers, estuaries, seawater, rainwater, wastewater - direct analyses,
pretreatment in some cases (e.g. for waters rich in organic matters)
SEDIMENTS
Contaminants « sinks » (contamination history). Matrices of variable compositions,
numerous interfering substances, difficulties to obtain a complete recovery of the analytes.
Analyses requiring pretreatment steps, followed by various steps (e.g. separation)
SOILS, SLUDGES, COMPOSTS
Agronomy studies, risk assessment, monitoring of treatment efficiencies, etc.
Similar difficulties in comparison to sediments, but more acute owing to a greater heterogeneity.
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ENVIRONMENT
MONITORING
- Matrix types (2) BIOLOGICAL SAMPLES
Plants, biological organisms (e.g. molluscs) analysed for bioaccumulation capacity
and used as « indicators » (trend studies, indicators of the quality of an ecosystem, nutritional
studies, etc.). Complex matrices that include various types of components (carbon, fat
mineral particles, dusts).
ATMOSPHERIC SAMPLES
Air, dusts, fly ashes, etc. Direct analyses using sensors (air) or indirect
(e.g. sampling on filters, leaching and « classical » analysis). Some bioindicators are used
for the indirect monitoring of atmospheric contamination (e.g. lichens)
VARIOUS WASTES
Of domestic or industrial origin. Analyses often based on leaching tests
to determine the « mobile » fraction of contaminants
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ENVIRONMENT
MONITORING
- Parameters (1) PHYSICO-CHEMICAL
pH, turbidity, conductivity, redox potential, etc.
MAJOR ELEMENTS
Matrix elements, contents above 0.1% in the environment
Examples: Si, Ca, K, P, Mg, Mn, N, Na, Fe
TRACE ELEMENTS
Contents at the mg/kg or µg/kg level - Ultratraces levels being less than µg/kg
Toxic and/or essential elements
Examples: As, Ba, B, Br, Cd, Cr, Co, Cu, F, I, Hg, Mo, Ni, Pb, Sb, Se, V, Zn
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ENVIRONMENT
MONITORING
- Parameters (2) CHEMICAL FORMS OF ELEMENTS
Specific forms of elements (e.g. different oxidation states, organometallic compounds,
oxides or hydroxides, complexed forms)
Examples: As(III), Cr(VI), methylmercury, tributyltin
« EXTRACTABLES » CHEMICAL FORMS
Chemical forms of elements that are operationally defined (single or sequential extraction)
They are qualified, e.g. as « mobile », « bioavailable », etc. forms
ORGANIC COMPOUNDS
Of anthropogenic origin or products of organic decompositions
Examples: chlorophenols, dioxins, hydrocarbons, pesticides, herbicides, polychlorobiphenyls
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ENVIRONMENT
MONITORING
- Types of methods (1) CALCULABLE METHODS
Result which may be foreseen from a calculation made on the basis of physical or chemical measurements
such as, e.g., sample weighing , volume of titrating reagent, etc. (e.g. titrimetry, gravimetry,etc.)
PRIMARY (OR DEFINITIVE) METHOD
Method with the highest metrological quality, having few random errors
(and no systematic errors), and for which a complete estimate of the
uncertainty may be obtained in terms of SI units (e.g. titrimetry, IDMS)
RELATIVE METHODS
Comparison of the analysed sample with calibrants of known concentrations. The result
is established through interpolation with the response curve of the calibrants (e.g. spectrometric techniques)
COMPARATIVE METHODS
Comparison of the analysed sample with calibrating samples which have not been subject to any
chemical treatment. The calibration is performed using certified reference materials with
a matrix similar to that of the sample (e.g. X-ray Fluorescence spectrometry)
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ENVIRONMENT
MONITORING
- Critical points (1) GENERAL FRAMEWORK
Selection of suitable method(s)
Quality assurance
Long-term storage
(sampling, analysis, storage)
(validation, quality control)
(specimen banking)
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ENVIRONMENT
MONITORING
- Critical points (2) SOME SELECTION CRITERIA
SAMPLING
Representativeness of the
environment, type of sample,
(selective, random of composed),
sampling strategy (site,
frequency, procedure, etc.)
CONSERVATION / STORAGE
Preservation of the integrity
(transport conditions and
conservation / storage,
types of containers,
temperature, etc.)
Philippe Quevauviller - Metrology
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ANALYTICAL METHODS
Equipment (e.g. glassware), and
consumables (e.g. reagents of
known purity), maintenance,
costs and adaptation to the aim
of the analyses
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SELECTION OF METHODS FOR
ENVIRONMENTAL MONITORING (1)
Criteria
- Selectivity, sensitivity, trueness - Repeatability, reproducibility - Detector linearity - Robustness - Costs (purchase, maintenance) -
- Facility and speed of utilisation “COUPLED” METHODS
• Extraction (acids, organic solvents)
• Derivatisation (hydride generation, Grignard reactions)
• Separation (GC, HPLC)
• Detection (AAS, ICP-MS, ECD, MS, etc.)
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SELECTION OF METHODS FOR
ENVIRONMENTAL MONITORING (2)
Sampling
« avoiding any risk of contamination or losses »
WATERS
- PTFE, polyethylene, polypropylene, borosilicate glass, etc. -
SEDIMENTS / SOILS, BIOTA
- Plastic tools or PTFE -
Pre-treatment
WATERS
- Acidification, filtration -
SEDIMENTS
- Sieving (wet, using water from the site) Philippe Quevauviller - Metrology
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SELECTION OF METHODS FOR
ENVIRONMENTAL MONITORING (3)
Stabilisation / Long-term storage (examples)
« Preserve the initial geo- and biochemical status »
STABILISATION
- Acidification (waters) - Lyophilisation (biota, sediments, etc.) - Oven-drying (sediments) - Pasteurisation (sediments) - Gamma irradiation (biota, sediments, waters) -
STORAGE
- Freezing for “sensitive” compounds (biota, sediments) - Storage at ambient temperature or at 4 °C (in the dark) -
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SELECTION OF METHODS FOR
ENVIRONMENTAL MONITORING (4)
Extraction / Digestion (examples)
ACIDS
Acetic acid, sulphuric acid, nitric acid (e.g. with microwave),
hydrofluoric acid (total digestion), etc.
MIXTURE ACID / ORGANIC SOLVENT
Hydrochloric acid/toluene, sulphuric acid/toluene, etc.
ORGANIC SOLVENTS
OTHERS
Toluene, methanol, tropolone
pentane, etc.
CO2 / methanol, supercritical fluid
enzymatic digestion (protease/lipase), etc.
RECOVERY TEST: Spiking (three levels)
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SELECTION OF METHODS FOR
ENVIRONMENTAL MONITORING (5)
Derivatisation (examples)
« Transformation of a given compound
for a better separation »
Hydride generation (NaBH4)
Ethylation (NaBEt4)
Grignard reactions
VERIFICATION OF YIELDS
(secondary calibrants)
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SELECTION OF METHODS FOR
ENVIRONMENTAL MONITORING (6a)
Separation (examples)
« required owing to the fact the determination of different
compounds of a same ‘family’ cannot, in general, be carried out
with a sufficient selectivity (e.g. selective detection by AAS) »
GAZ CHROMATOGRAPHY
- with packed column - with capillary column -
HIGH PERFORMANCE
LIQUID CHROMATOGRAPHY (HPLC)
OTHERS
- Cryogenic trapping - Capillary electrophoresis - Ion exchange microcolumns Philippe Quevauviller - Metrology
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SELECTION OF METHODS FOR
ENVIRONMENTAL MONITORING (6b)
Examples of chromatograms
Peak
height
1
2
2
3
4
1
4
3
A
B
13.9
16.9
11.2
11.4
12.0
Retention time (minutes)
A - Megabore column
B - Capillary column
1. Ph2SnPe2; 2. Cy2SnPe2; 3. Ph3SnPe; 4. Cy3SnPe
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SELECTION OF METHODS FOR
ENVIRONMENTAL MONITORING (7)
Detection (examples)
SPECIFIC OF A GIVEN ELEMENT
- Atomic absorption spectrometry (electrothermal, flame, quartz furnace)
MULTI-ELEMENT
- Inductively coupled plasma atomic emission spectrometry (ICP-AES) - ICP mass spectrometry (ICP-MS) -
SPECIFIC OF A GIVEN ELEMENT SPECIES
- Voltametry -
SPECIFIC OF A GIVEN COMPOUND
- Flame ionisation detection (FID) - Flame photometric detection (FPD) - Electron capture detection (ECD) -
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SELECTION OF METHODS FOR
ENVIRONMENTAL MONITORING (8)
Calibration
AVAILABILITY OF CALIBRANTS
- Primary calibrants (calibration) - Internal standards (*) (correction of matrix interférences, with associated risks, e.g. different response , linearity)
- Stoichiometry, purity -
CALIBRATION METHODS
- External - Matrix matching - Bracketing calibration - Standard additions (*) The term « standard » is often prone to confusion (calibrants, RM, written standards)
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SELECTION OF METHODS FOR
ENVIRONMENTAL MONITORING (9)
Uncertainty
« Parameter associated to the result of an analysis, characterising the dispersion
of the values which may be attributed to the measurement » : Range of values
in which the measured amount should be found
The uncertainty defines the degree of confidence which may be attributed to a measurement. It includes
both systematic effects (errors that are constant or varying in a foreseable way, which may be corrected,
e.g. blanks, incomplete extraction, etc.) and random effects (not controlled, e.g. background noise).
IMPLICATIONS FOR ENVIRONMENTAL ANALYSES
The “total” uncertainty should in principle combine the uncertainties
of each analytical step
- Sampling - Pre-treatment (extraction, derivatisation) - Separation and detection - Calibration Philippe Quevauviller - Metrology
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SELECTION OF METHODS FOR
ENVIRONMENTAL MONITORING (10)
Example :
Tributyltin (TBT) in coastal waters
PRESENT AT THE ULTRA-TRACE LEVEL (ng.L-1)
Hence need of a sensitive method
OCCURRENCE NUMEROUS ORGANOTIN COMPOUNDS
Hence need for a selective method
RISKS OF DEGRADATION OF TBT
Particular care at the sampling and storage steps.
Need to determine degradation products (DBT, MBT)
ANALYTICAL PROCEDURE
Obviously a sophisticated technique, combining an efficient extraction
(but not destructive), a good separation and a sensitive detection.
Alternative: Bioindicators (e.g. Nucella lapilus)
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PERFORMING ANALYTICAL WORK
General aspects
• Obtaining samples and conserve them in the best conditions
• Selecting the method and ensuring that it is in good functioning order
• Planning the work and identifying critical steps (including risks)
• Ensuring that a suitable working space is available
• Verifying glassware, consumables, calibrants and RMs
• Foreseeing procedures related to wastes (e.g. used solvents)
• Cleaning of the laboratory
NOTE: The analytical report and data archiving is considered as being an integral part of the metrological
system. The report should contain a detailed description of the objective of the study, of the procedures
used, quality control, performances of the method, the interpretation of the data, questions and unsolved
problems. The archiving should in principle be in electronic form (e.g. use of LIMS software).
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QUALITY CONTROL (1)
Signal
calibration
S1
Purification
separation
Extraction
digestion
S2
M
Synthetic solutions
(known calibrants)
Solutions with known
analyte concentrations and
unknown matrix
(e.g. spiked extract)
Validation
(principles)
« Demonstrating that the results obtained
with a given method are reliable,
reproducible and that the method is
adapted to the foreseen application »
• Apparatus, computers
• Analytical method (following slides)
• Control charts
“Matrix” material
similar to the sample
(natural or spiked)
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QUALITY CONTROL (2)
* **
*
******
Verification of trueness
« Closeness of agreement between the result of a measurement and
the true value of the measured value (the true value is known only is
the measured amount may be perfectly determined and if all the
measurement errors have been eliminated »
Verification of precision
« Closeness of agreement between results of measurement of a
same substance, applying the same experimental procedure
several times in the same conditions (repeteability; the
reproducibility is the closeness of agreement in time, taking into
consideration variations of conditions (location, analyst); it has
to be distinguished from robustness (capacity of the method to
remain unaffected by minor changes of the procedure (e.g.
reagents or environment) »
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* *
* ** *
* *
*
*
**
* **
***
**
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QUALITY CONTROL (3)
Reference Material
« Material or substance one or more of whose property
values are sufficiently homogeneous and well established
to be used for the calibration of an apparatus, the
assessment of a measurement method, or for assigning
values to materials (ISO, guide 30) »
Certified Reference Material
« Reference material, accompanied by a certificate, one or more
of whose property values are certified by a procedure which
establishes traceability to an accurate realisation of the unit in which
the property values are expressed, and for which each certified value
is accompanied by an uncertainty at a stated level of confidence
(ISO, guide 30) »
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QUALITY CONTROL (4)
Control charts
« Graphical mean to evaluate
the reproducibility of a method »
SIMPLE CHARTS
The value reported on the chart is the result
obtained each time a measurement is carried out.
(see following example)
CUMULATIVE CHART (CUSUM
The value reported on the chart is the sum
of the absolute value of the differences between the
measured value and a reference value.
This type of chart enables to detect more rapidly
possible method drifts.
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QUALITY CONTROL (4 ’)
Example of control chart
Measured
concentration
3s
2s
mean
Warning (2 s) and action (3 s) limits correspond, respectively, to a risk of 1 and 5 % that the result does not belong to the
population of other results. The values of the mean and standard deviation (s) are determined by several measurements
(at least 10 repetitions) carried out at the start of the analytical work, but on several days.
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QUALITY CONTROL (5)
Interlaboratory testing
« Study in the framework of which several laboratories
analyse one or several identical and homogeneous material(s),
in specified conditions
and for which the results are collected in a single report »
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INTERLABORATORY TESTING (1)
Generalities
TYPES OF STUDIES
• Method performance studies
• Proficiency testing schemes (several methods)
• Certification of reference materials (attribution of « true values »)
REQUIREMENTS
• Co-ordination
• Motivation of laboratories (and competence)
• Availability of testing materials
• Technical evaluation of the results
• Statistical evaluation
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INTERLABORATORY TESTING (2)
DETECTION
DERIVATISATION
PURIFICATION
SEPARATION
EXTRACTION
MINERALISATION
OVERALL
METHOD
S1
S2
M1
M2
Simple solutions
(pure substances
or mixtures of substances)
Matrix-matching solutions
or extracts (spiked or not)
Reference material
(« matrix ») similar
to the sample, spiked with a
known analyte concentration
Matrix material
similar to the sample
Improving schemes
(method performance studies)
The followed principle is similar to a method
validation, i.e. analyses of increasingly complex
matrices to detect errors that may occur
at various analytical steps.
These schemes have a pedagogical aim and
imply the organisation of technical meetings
in the framework of which participants exchange
their experience and discuss weak points
of the methods and the error sources.
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REFERENCE MATERIALS
Conditions
Representativeness
It implies a similarity of composition between the material and
the sample that is routinely analysed (similar sources of errors):
• Matrix composition
• Contents of substances
• Binding status of the substances in the matrix
• Physical status of the material
Homogeneity / stability
- Intra- and inter-vial homogeneity - Long-term stability -
Setting reference values
- « Definitive » method in a specialised laboratory - Several independent methods in an expert laboratory - Several methods applied by several laboratories Philippe Quevauviller - Metrology
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EXAMPLE OF IMPROVEMENT SCHEME
(Methylmercury)
Enriched
extract
YOUDEN PLOT
WORK PROGRAMME
• Improvement scheme (series of 3 rounds): 1988-90
• Certification of fish reference materials: 1991-94
• Certification of sediment reference material: 1994-96
RESULTS
Raw extract
Mean
of means
• Withdrawal of packed columns
• Detection of sources of errors (e.g. distillation)
• Two fish CRMs
• One sediment CRM
mg/kg MeHg
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EXAMPLE OF CERTIFICATION
RESULTS (Methylmercury)
65.0
75.0
GC-CVAFS
GC-CVAAS
85.0
CONCLUSIONS
• Creation of a network of laboratories
• Enhanced knowledge on methods and validation needs
• Tools for quality control
GC-CVAAS
GC-QFAAS
GC-ECD
GC-ECD
GC-ECD
PERSPECTIVES
- Development of new methods (more rapid and easy to use)
- Studies of analytical artefacts - Laboratory reference materials -
SFEGC-MIP
HPLC-CVAAS
HPLC-CVAFS
HPLC-ICPMS
MeHg (sediment)
in µg/kg
M
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PERSPECTIVES (1)
- Monitoring -
- Quality (and metrology)- Research -
- Training -
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PERSPECTIVES (2)
Environment monitoring
Towards a global approach
HARMONISATION
- of strategies - of methods (from sampling to analysis) - of “target” parameters and matrices - Selection de reference sites (at national / international level) -
“MEMORY”
- Storage of environmental specimens (specimen banking)
- Warning system at the international level -
Philippe Quevauviller - Metrology
in environmental chimistry
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PERSPECTIVES (3)
Quality assurance
STANDARDISATION?
- Necessary for monitoring strategies - Not systematic for analytical methods (risk of “progress fossilisation”) -
ACCREDITATION?
- Necessary for control laboratories - Necessary for RM producers -
REFERENCE MATERIALS
- Establishment of a producer network in Europe - Feasibility studies and CRM production - Structure production of control MRs -
PROFICIENCY TESTING
- Organisation of targeted ring tests at international level - Support to the accreditation of control laboratories -
Philippe Quevauviller - Metrology
in environmental chimistry
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PERSPECTIVES (4)
Metrology
TRACEABILITY
Avoiding “fundamentalism” - The demonstration of
traceability of a measurement should remain accessible
to routine laboratories
- Systematic studies of risks of error related to sampling - “Matrix” materials enriched with isotopically-labelled compounds - “Secondary” standards - Recovery studies on extraction and derivatisation -
UNCERTAINTY
- Systematic study on “total uncertainty budgets” (uncertainty calculated at each step and combined)
- Studies of simplified alternatives for routine uncertainty calculations -
Philippe Quevauviller - Metrology
in environmental chimistry
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EXAMPLE OF TRACEABILITY CHAIN
(Trace elements in seawater)
ANALYTICAL STEPS
REFERENCES
SAMPLING
Internationally
recognised
procedures
A
PRETREATMENT,
STORAGE
Internationally
recognised
procedures
B
CHEMICAL
TREATMENT
Addition of spike of
known purity and
stoichiometry
C
IDMS
DETECTION
Measurements
of spike ratios
D
RESULTS
Philippe Quevauviller - Metrology
in environmental chimistry
51
EXAMPLE OF TRACEABILITY CHAIN
(Tribultin in harbour dredges)
RESULTS
ANALYTICAL STEPS
REFERENCES
SAMPLING
No standards,
literature-based
A
STORAGE,
PROCESSING
No standards,
literature-based
B
EXTRACTION
No standards,
available CRMs
C
DERIVATISATION
(if necessary)
Secondary standards
D
SEPARATION
Internal standards
E
FINAL
DETECTION
Primary calibrants
F
Philippe Quevauviller - Metrology
in environmental chimistry
52
Research/testing
REFERENCE SITES
to improve field
methods and sampling
procedures
Harmonised
written standards
SAMPLING
B
C
Validated
written standards
Method
optimisation
Development
of new methods
A
STORAGE,
PROCESSING
IRMs
(fresh)
D1
LRMs
(freeze-dried)
D3
E
SPECIMENS
BANKING
D2
I
VALIDATED METHOD
Extraction,
digestion etc.
F
Chemical reactions
(e.g. derivatisation)
Secondary
standards
Separation
Internal
standards
Detection
N
E
T
W
O
R
K
Written standards,
matrix CRMs
G
Primary
calibrants
Control charts,
proficiency
testing
H
Routinely
operated
method(s)
RESULTS
I
N
T
E
R
N
A
T
I
O
N
A
L
J
FOLLOW-UP OF
ENVIRONMENT
QUALITY
53
PERSPECTIVES (5)
Research
ENVIRONMENTAL STUDIES
- Biogeochemical cycle of elements and compounds - Toxicity and bioavailability studies - Development of new methods (in particular rapid methods, low cost, applicable to the field)
FEASABILITY STUDIES
- Research on reference materials (e.g. wet materials)
- Stability studies of materials / substances -
APPLICABILITY
- Interface “science-policy” - Public awareness -
Philippe Quevauviller - Metrology
in environmental chimistry
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PERSPECTIVES (6)
Training
ENVIRONMENTAL SCIENCES
Mulidisciplinary training
- Geochemistry, biology - Analytical chemistry - Metrology (including quality assurance) - Regulations (“science-policy” interface) -
QUALITY ASSURANCE
Theoretical and applied training
- Quality of environmental measurements (from sampling to decision-making)
- Practical training on site -
Philippe Quevauviller - Metrology
in environmental chimistry
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CONCLUSIONS
CENTRES OF COMPETENCE (National / Regional)
- Multidisciplinary expertise in the environmental field - Site monitoring - Environmental specimen banking -
EUROPEAN NETWORKS
- Networked site monitoring (harmonised strategies) - International meetings held at regular intervals (involving scientists, industrialists, regulators)
EXCHANGES / TRAINING
- Transfer of knowledge and technologies - Exchanges of students and technicians - International hosting institutions -
Philippe Quevauviller - Metrology
in environmental chimistry
56
FURTHER INFORMATION
ENVIRONMENTAL METROLOGY
- Métrologie en chimie de l ’environnement (Tec&Doc, 2000) - Metrology in chemistry - A practical approach (Valcárcel et al., 1998) -
REFERENCE MATERIALS
- CRMs and interlaboratory studies for environmental analysis (1999) (Quevauviller & Maier, Elsevier, ISBN 0-444-82389-1)
- ISO/REMCO (Laboratoire National d ’Essais) - Matériaux de référence pour l ’environnement (Tec&Doc, 2002) -
ACTIVITIES OF THE EUROPEAN COMMISSION
- Institute for Reference Materials and Measurements (IRMM) (http://www.irmm.jrc.be/mrm.html)
- Various general and targeted publications (contact: [email protected])
Philippe Quevauviller - Metrology
in environmental chimistry
57