EURACHEM / CITAC -ohjeen yleisesittely Prof., TkT Veikko Komppa, VTT Prosessit PL 1602, 02044 VTT Veikko.Komppa@vtt.fi Kemiallisten mittausten jäljitettävyys 1. EURACHEM / CITAC ohje ja esite 2. LGC VAM -ohjelman ohje
EURACHEM / CITAC -ohjeen yleisesittely Prof., TkT Veikko Komppa, VTT Prosessit PL 1602, 02044 VTT Veikko.Komppa@vtt.fi 1. EURACHEM / CITAC Guide (2003) Traceability in Chemical Measurement: A guide to achieving comparable results in chemical measurement http://www.eurachem.ul.pt/guides/ec_trace_2003.pdf 2. LGC VAM (2003) An Analyst's Guide to Meeting the Traceability Requirements of ISO 17025 (2nd Edition) http://www.vam.org.uk/themes/theme_publications_item.asp?intthemeid=2&intpublicatio nid=839 3. EURACHEM/CITAC Leaflet (2004) Traceability of Analytical Results vain painettuna
1. EURACHEM/CITAC Guide (2003) Traceability in Chemical Measurement: A guide to achieving comparable results in chemical measurement UUSI VIM (2004) voting draft metrological traceability property of a measurement result relating the result to a stated metrological reference through an unbroken chain of calibrations of a measuring system or comparisons, each contributing to the stated measurement uncertainty NOTES (1-5) 1 For this definition, a stated metrological reference can be a definition of a measurement unit through its practical realization, or a measurement procedure, or a measurement standard. 2 A prerequisite to metrological traceability is a previously established calibration hierarchy.
1. EURACHEM/CITAC Guide (2003) Contents page 1 1 Scope and Field of Application 3 2 Introduction 3 3 Principles of traceability 6 3.1 Methods, Measurands and Results 6 3.2 Measurement scales, standards and units 6 3.3 Calibration 7 3.4 Effects on measurement results 7 3.5 Controlling fixed conditions 8 3.6 Controlling variables with calibration standards 9 3.7 Common references allow arbitrary definition 11 3.8 Role of method development 11 3.9 Role of method validation 11 3.10 Traceability and measurement uncertainty 12
1. EURACHEM/CITAC Guide (2003) 4 Traceability: The International Definition 13 5 International System of Quantities and Units (SI) 13 6 Establishing Traceability 15 6.1 Essential activities in establishing traceability 15 6.2 Specifying the measurand and required uncertainty 15 6.3 Choosing a suitable method 16 6.4 Validation 16 6.5 Importance of different influence quantities 18 6.6 Choosing and applying appropriate reference standards 18 6.7 Uncertainty estimation 19
1. EURACHEM/CITAC Guide (2003) 7 Choice of the Reference 20 7.1 Introduction 20 7.2 Physical measurements 20 7.3 Confirmation of identity 21 7.4 Calibration with certified reference materials 21 7.5 Calibration with other materials 22 7.6 Calibration using reference data 23 7.7 Reference materials for Method Development, Validation 23 7.8 Assessing the traceability of commercial reference materials 24 8 Reporting Traceability 24 9 Conclusion 25 10 Bibliography 26 Appendix: Examples of Establishing Traceability (MU Guide) 27 1. Preparation of a calibration standard 28 2. Cadmium Release from Ceramic Ware 32
1. EURACHEM/CITAC Guide (2003) the key elements in establishing traceability i) Specifying the measurand, scope of measurements and the required uncertainty ii) Choosing a suitable method of estimating the value, that is, a measurement procedure with associated calculation - an equation - and measurement conditions iii) Demonstrating, through validation, that the calculation and measurement conditions include all the influence quantities that significantly affect the result, or the value assigned to a standard. iv) Identifying the relative importance of each influence quantity v) Choosing and applying appropriate reference standards vi) Estimating the uncertainty
1. EURACHEM/CITAC Guide (2003) Summary of basic principles 1. We assume that an acceptable estimate y of the measurand value can be obtained from y = f(x1, x2, xm) xm+1 xn that is, y is calculated from x1 xm using a relationship f which is valid under measurement conditions specified by xm+1 xn. 2. Validation checks that the equation above is sufficient using suitable tests. 3. y is then considered traceable to x1 xn 4. Given that Eq 1 is sufficient, all that is necessary for complete traceability to appropriate references is that all the values x1 to xn are themselves traceable or defined values.
1. EURACHEM/CITAC Guide (2003) Examples of Establishing Traceability are taken from EURACHEM/CITAC Guide Quantifying Uncertainty in Analytical Measurement (2000) 1. Preparation of a calibration standard (Cd in water) 2. Cadmium Release from Ceramic Ware (BS 6748)
2. LGC VAM: Traceability Guide Kaliumjodidin määritys vitamiinipillereistä Menetelmän jäljitettävyys- / epävarmuustarkastelun perusteella neljä tekijää on merkittävää: Kaliumjodaatin puhtaus (99,5 99,96 %) Natriumtiosulfaatin molaarisuus (titraus kaliumjodaatilla ja volymetriset astiat) Vitamiinipillerin punnitus (massa) Kaliumjodaatin ja -jodidin moolimassat (3 desimaalia)
2. LGC VAM: Traceability Guide Anionien määritys IC:llä vedestä Kriittiset muuttujat ovat Kalibrointistandardit (NaF, NaCl, NaNO3, KH2PO4, K2SO4) Varmennettu vertailuaine (CRM)
2. LGC VAM: Traceability Guide Muut esimerkit: Ruoan ja biologisten materiaalien alkuaineiden määritys (ICP MS: Na, K, Ca, Mg, P, Cu, Fe, Mn, Zn) Vesiliukoisten alkuaineiden määritys (ICP MS) Dimetyylitriatsolin määritys rehusta (HPLC) Kuningasvesiliukoiset metallit maaperässä (ICP MS)
3. EURACHEM/CITAC Leaflet (2004) Traceability of Analytical Results Esimerkki: tonnikalan Hg Elohopea mikroaaltoliuotuksen jälkeen AAS kylmähöyrytekniikalla Punnitukset tehtiin kalibroiduilla vaa'oilla (SI jäljitettävyys) Liuotus ja laimennukset astioissa, joilla on valmistajan todistus (SI jäljitettävyys) Kalibrointi varmennetulla vertailuaineella (CRM) 0.998± 0.005 mg Hg/kg (k=2) jäljitettävyys puhtaaseen elohopeaan Menetelmä validoitu matriisivertailuaineella tasolla 1.97 ± 0.04 mg Hg/kg (k=2).
3. EURACHEM/CITAC Leaflet (2004) Traceability of Analytical Results Esimerkki: tonnikalan Hg Jäljitettävyysvakuutus 1. Elohopeapitoisuus <===> CRM:n todistus 2. Näytteenmassa <===> vaakojen todistus/kalibrointi 3. Astioiden tilavuudet <===> valmistajien todistukset 4. Kuivatuslämpötila <===> uunien kalibrointi 5. Kuivatusaika <===> kellojen kalibrointi 6. Liuotusolosuhteet <===> validointi ja olosuhteiden seuranta
Lisää tietoa löytyy esimerkiksi EURACHEM:n verkkosivut: http://www.eurachem.ul.pt/ CITAC:n verkkosivut: http://www.citac.cc/ LGC VAM -ohjelman verkkosivut: http://www.vam.org.uk/