5.13 (6.13)[/b]
[b]reference material
RM
material, sufficiently homogeneous and stable regarding one or more properties, used in calibration, in assignment of a value to another material, or in quality assurance[/b]
NOTES
1
“Reference material” comprises materials embodying [b]quantities as well as nominal properties.
EXAMPLES OF REFERENCE MATERIALS EMBODYING QUANTITIES
a)
water of stated purity, the dynamic viscosity of which is used to calibrate viscometers
b)
human serum without an assigned quantity value for the concentration of the inherent cholesterol, used only as a precision control material
c)
fish tissue containing a stated mass fraction of a dioxin, used as a calibrator
EXAMPLES OF REFERENCE MATERIALS EMBODYING NOMINAL PROPERTIES
d)
colour chart indicating one or more specified colours
e)
DNA compound containing a specified nucleic acid sequence
f)
urine containing 19-andro……… (René)
2
In this definition, ‘value’ covers both “quantity value” and
“nominal property value”.
3
Reference materials with or without assigned quantity valuescan be usedfor precision control whereas only reference materials with assigned quantity values can be used for calibration or trueness control.
4
Some reference materials have quantities which are metrologically traceable to a measurement unit outside a system of units.
Such materials include vaccines to which International Units (IU) have been assigned by the World Health Organization.
5
In a given measurement, a reference material can only be used for either calibration or quality assurance.
6
A reference material
is sometimes incorporated into a specially fabricated device.
EXAMPLES
a)
substance of known triple-point in a triple-point cell
b)
glass of known optical density in a transmission filter holder
c)
spheres of uniform particle size mounted on a microscope slide
d)
array of Josephson junctions
7
All reference materials have material traceability, i.e. the origin of the material must be known.
5.14 (6.14)[/b]
[b]certified reference material
CRM
reference material, accompanied by documentation issued by an authoritative body and referring to valid procedures used to obtain a specified
property value with uncertainty and traceability
EXAMPLE
human serum containing cholesterol with assigned quantity value and associated measurement uncertainty stated in an accompanying certificate, used as calibrator or trueness control material
NOTES
1
The ‘documentation’ is given in the form of a “certificate”, see ISO Guide
30:1992.
2
Valid procedures for the production and certification of certified reference materials are given, e.g., in ISO Guides 34 and 35.
3
In this definition, ‘uncertainty’ covers both “measurement uncertainty” and “uncertainty of nominal value”, such as for identity and sequence, expressed as probabilities. ‘Traceability’ covers both “metrological traceability” of a quantity value and “traceability of nominal value”.
4
“Certified reference material” is a specific concept under “reference material”.
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