Traceability in Chemical Measurement Comparable results are needed in order to avoid duplicating measurements which cost time and money. Comparable results can only be achieved by anchoring them to a common base. Why Traceability?

Traceability ELEMENTS OF TRACEABILITY –an unbroken chain of comparisons going back to a standard acceptable to the parties, usually a national or international standard; –measurement uncertainty; –documentation; –competence; –reference to SI units; –recalibrations;

Traceability How is traceability of results best achieved? –stated and/or internationally agreed suitable references –an uncertainty* statement for the measurement whose key role is to enable to judge the "fitness for purpose" of a result »* Guide to the Expression of Uncertainty in Measurement, ISBN , International Organization for Standardization, Genève 1993 (& draft updates, respectively)

Traceability Technical Elements of Traceability –it must be able to rely on all the references necessary in the measurement process, as well as on method validation; –A laboratory finds itself typically at the end of the traceability chain; –values of all references are themselves traceable to stated references and are accompanied by a reliable uncertainty statement.

Traceability Technical Elements of Traceability masssample mass, on a balance compared to a mass reference –Determination of amount of substance often requires measurements of different properties, e.g.: identityanalyte identity by comparison to a reference quantitationanalyte quantitation by comparison to a different reference Each property of the result should be traceable, and each may contribute uncertainty to the reported result.

Traceability Traceability of Values Carried by RM –traceability supplied from outside the laboratory is the traceability of values carried by references, especially by certified reference materials; –producers of reference materials must be aware that the values they supply are invariably an indispensable link in the traceability chain. Reference: ILAC

Traceability LEVELS IN THE CALIBRATION HIERARCHY 4 International –The Bureau International des Poids et Mesures (BIPM) is in charge with coordinating the development and maintenance of primary standards and organizes intercomparisons on the highest level. 4 National Metrology Institutes –National Metrology Institutes are the highest authorities in metrology, maintaining “national standards”, ensuring that the primary standards themselves are internationally comparable.

Traceability TERMINOLOGY IN THE HIERARCHY OF STANDARDS 4 Primary standard: –A standard that is designated or widely acknowledged as having the highest metrological qualities 4 International standard: –A standard recognized by an international agreement to serve internationally as the basis for assigning values to other standards

Traceability TERMINOLOGY IN THE HIERARCHY OF STANDARDS 4 National standard: –A standard recognized by a national decision to serve as the basis for assigning values to other standards 4 Reference standard: –A standard, generally having the highest metrological quality available at a given location or in a given organization

Traceability TERMINOLOGY IN THE HIERARCHY OF STANDARDS 4 Transfer standard: –A standard used as an intermediary to compare standards. 4 Travelling standard: –A standard, sometimes of special construction, intended for transport between different locations. 4 Working standard: –Standard calibrated against a reference standard and used routinely to calibrate or check material or measuring instruments.

Traceability Calibration hierarchy