Developing benchmarks for measurements The IRMM approach

Transcription

1 RM Unit / HE / Developing benchmarks for measurements The IRMM approach Hendrik Emons Institute for Reference Materials and Measurements (IRMM) Joint Research Centre, European Commission, Geel, Belgium hendrik.emons@ec.europa.eu

2 Our Mission RM Unit / HE / JRC s Mission is to provide customer-driven scientific and technical support for the conception, development, implementation and monitoring of EU policies. As a service of the European Commission, the JRC functions as a reference centre of science and technology for the Union The mission of the IRMM is to promote a common and reliable European measurement system in support of EU policies.

3 RM Programme Considerations RM Unit / HE / EU Stakeholders: Policy Directorates of the European Commission European Agencies EURL/NRL networks CEN, EA, EURAMET Member States (authorities & laboratories) Compliance with Legislation Development of global RMs EU Legislation Global Stakeholders: ISO, ILAC, CIPM other international organisations (IAEA, Codex, OECD, ) Sector-specific bodies (IFCC, VAMAS, AOAC, ) control/monitoring laboratories Global trade Health & Quality of life

4 The drivers RM Unit / HE / Driver: Curiosity? Analytical problem with decision relevance Driver: Toxicology or Fraud or Driver: Legislation Validated analytical methods Driver: Accreditation Reference Materials

5 IRMM s RM Programmes RM Unit / HE / TSE QCMs Food CRMs Clinical CRMs Microbiol. CRMs GMO CRMs Soil/ Sediment CRMs Nuclear CRMs Water CRMs Engin. Mat. CRMs

6 What to certify? RM Unit / HE / We are able to measure cadmium in homogeneous water, Kjeldahl-nitrogen in dried foodstuff, solid particle diameters by electron microscopy, (currently) measurable parameters? = parameters with decision relevance

7 Example: Nanoparticles RM Unit / HE / Dynamic Light Scattering EHS-(decision) relevant parameter? 46 ± 2 nm Hydrodynamic diameter Disc sedimentation Nanoparticle size? 35 ± 1 nm Stokes diameter nanoparticle suspension but: particles unstable & reactive various transformations measure also dynamics

8 The measurand dilemma RM Unit / HE / VIM-3 (ISO Guide 99) definition of measurand : Quantity intended to be measured Measurand: Mass fraction of proteins in food but Real measurement subject: often Kjeldahl nitrogen Understanding of the whole measurement process & transformations required Potential fraud (melamine)

9 What to certify RM Unit / HE / Example: C-reactive protein (CRP) - Clinical marker of inflammation: 1 mg/l normal mg/l mild inflammation, viral infections mg/l severe bacterial infections, burns - Marker of cardiac risk: >2.4 mg/l increased risk MS signal Sample treatment (e.g., freezedrying) Immunoassay response?

10 CRP immunoassays RM Unit / HE / CRP Pentamer in serum matrix CRP Pentamer in buffer Monomer in buffer Material Normalized relative CRP mass concentration by with different methods IA-1 IA-2 IA-3 IA-4 IA-5 IA-6 IA-7 ERM- DA472/IFCC 100 % 89 % 107 % 100 % 89 % 98 % 100 % Pentamer In buffer 103 % 49 % 59 % 79 % 96 % 117 % 100 % Monomer In buffer 12 % 0.01 % < 0.01 % < 0.1 % < 0.1 % 0.02 % 0.02 % Standardisation required!

11 Towards comparability RM Unit / HE / Approach: Standardisation harmonized methods PASC COPANT CEN AIDMO ARSO PASC EASC ACCSQ PASC Approach: Metrology ultimate analysis Metrological traceability Measurement uncertainty MO/LDE9606B.CDR prescribed methods/procedures sampling, method-defined parameters extractable Pb, SCCP Legislation prescribed method-performance characteristics SI-traceable parameters Cd, B[a]P, Consequences for required measurement standards!

12 Expressing traceability RM Unit / HE / Traceability statements on ERM Certificates Traceability is split into Identity (measurand) Quantity value (number and unit) Operationally defined Structurally defined Reference = SI Reference = artefact

13 Challenge sum parameters RM Unit / HE / Example: SCCPs = highly complex technical mixtures of polychlorinated n-alkanes - chain length C10-C13, % Cl - up to 6300 isomers Environmental and health concern: persistent, toxic, bioaccumulative, possibly carcinogens (2B) Directive 2000/60/EC: Water Framework Directive Decision 2455/2001/EC: Introduction in the list of Priority Hazardous Substances Environmental Quality Standards: C 10 -C 13 Chloroalkanes ( g L -1 ) AA-EQS 0.4 MAC-EQS 1.4 AA annual average MAC maximum allowable concentration

14 Current limitations RM Unit / HE / SCCPs measured with GC-ECNI-MS TRACEABILITY conc. CPs Area i.s./area i.s calibrant 1 calibrant 2 calibrant concentration (mg/l) Sufficient definition of the measurement subject(s) Proper selection & description of the calibrants & calibration hierarchy

15 Operationally defined measurands RM Unit / HE / definition of (SI) unit input/influence parameters SI-traceable CRM primary calibrator CRM laboratories working calibrator routine sample RESULT primary reference measurement procedure secondary reference measurement procedure laboratories measurement procedure to be internationally agreed & accepted definition of measurand

16 Example: GM quantification RM Unit / HE / Polymerase Chain Reaction (PCR) 2 copies 1 4 copies Fluorescence Threshold Ct copies 16 copies Cycle number Ct = slope log 10 Cp + intercept with? Calibration needed!

17 14 12 True GM DNA copy number ratio RM Unit / HE / Maize NK603 cpnr- gdna calibrant Expected Normal NK603 content [cp/cp % s] NK603 content [cp/cp %] % (m/m) NK603 maize pdna A B C A B Extraction method gdna cpnr- pdna calibrant Expected Normal C No. of obs copy number (%) gdna for calibration: 1.17 % ± 0.21 % Soybean No. of obs copy number (%) pdna for calibration: 0.90 % ± 0.19 %

18 Proposed Reference System RM Unit / HE / for measurements of GM DNA copy number ratio by quantitative PCR Quality control matrix CRM % (cp/cp) pdna CRM Independent calibration Food/feed sample Sample preparation DNA extraction / purification Real-time PCR Data evaluation Measurement result PCR = limited precision consequences for CRM production & monitoring consequences for GM surveillance

19 Uncertainty of decisions RM Unit / HE / Analytical result: _ x ± u threshold (1B) (1A) (2A) (3A) (4A) (4B) Fit-for-decision: by adequate uncertainty

20 But: The 3M dilemma RM Unit / HE / Method Material Man Measurement signal + doubt about the attributed quantity value = measurement uncertainty Influences from measurement procedure (incl. instruments etc.) Relevant intrinsic material heterogeneity Influences from the analyst

21 Example: Nuclear safeguards RM Unit / HE / Minimum requirements for lab performance set by safeguards authorities: International Target Values (ITV) for measurement uncertainties lowered in recent years due to improved measurement capabilities New demands on CRMs used as IDMS spikes CRM certified value [mol. g -1 ] U rel (k=2) year 1995 year 2010 year 1995 year 2010 IRMM-046b 233 U % % IRMM-046b 242 Pu % % year 1997 year 2010 year 1997 year 2010 IRMM-049c 242 Pu % IRMM-049d 242 Pu ( ) (0.030 %)

22 Further RMP challenges RM Unit / HE / and related IRMM approaches R&D across scientific disciplines and application sectors: Team with multidisciplinary background and interdisciplinary tasks; communication & collaboration networks; involvement in various international committees and scientific bodies Expansion of RM concepts and QA/QC systems into new fields: Identity CRMs for human genetic testing & microbiology; QCMs for BSE testing Development & production of a broad range of RMs: collaborative projects; early-on coordination with other RMPs Providing new CRMs which imitate closer real-world samples: systematic checks of the equivalent analytical behaviour of RM & test sample in RM characterisation studies Qualification of RM users: Training courses; ERM Application Notes; guidance documents; customer services

23 RM Unit / HE / All Conference participants Our collaborators and cooperation partners all over the world THANK YOU! Current and former coworkers of the RM Unit & supporting IRMM staff

24 RM Unit / HE / All Conference participants Our collaborators and cooperation partners all over the world THANK YOU! Current and former coworkers of the RM Unit & supporting IRMM staff