Standards are chemical or physical material used in the laboratory.
Reference materials or standards are often referred to as actual chemical or physical materials called metrological standards. A metrological standard is the fundamental example or reference for a unit of measure. Simply stated, a standard is the ‘known’ to which an ‘unknown’ can be measured. Metrological standards fall into different hierarchal levels.
Primary standards
The definitive example of its measurement unit to which all other standards are compared and whose property value is accepted without reference to other standards of the same property or quantity (1,2: VIM, ISO Guide 30). Primary standards of measure, such as weight, are created and maintained by metrological agencies and bureaus around the world (i.e. NIST).
Secondary standards
Close representations of primary standards which are measured against primary standards. Many chemical standards companies create chemical standards against a primary weight set in order to create secondary standards traceable to that primary
standard.
Working standards
Created against or with secondary standards to calibrate equipment. There are also many standards designated as reference materials, reference standards or certified reference materials which are materials which are manufactured or characterized for a set of properties and are traceable to a primary or secondary. If the material is a certified reference material, then it must be accompanied by a certificate which includes information on the material’s stability, homogeneity, traceability, and uncertainty (2,3: ISO 30 & 17024).
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