Standards and reference materials play a crucial role in any analysis. It is just not possible to imagine any analysis in which a standard reference is not involved. Identification of sample components can be made only against reference to a known standard. Similarly the amount of any component in the sample can be determined by comparison of observed response with the response obtained from unknown quantity of a standard in the same sample matrix and under identical experimental conditions.
Standard is a material used to check the quality and metrological traceability of products, validate analytical methods or for calibration of analytical instruments.
Reference material is a homogeneous and stable compound with respect to one or more specified properties which have been established for use in a measurement process
Certified Reference Material
Certified reference material is characterized by a valid procedure for one or more specified properties. It is accompanied by a certificate of analysis that guarantees the value of the specified property, its associated uncertainty and statement of metrological traceability
Role of Standards in Calibration
Calibration plays an important role in establishing reliability of analysis results generated by accredited laboratories in compliance with ISO 17025:2005. Such laboratories rely heavily on certified reference materials.
Measurement traceability relates to the value of a standard which can be associated with national or international standard bodies through an unbroken chain of comparison all having stated uncertainties.
Types of Standard Reference Materials
Reference materials can be sourced from globally recognized standard bodies such as NIST. These are available as:
- Very high purity grade chemicals or compounds characterized by chemical purity of main component as well as trace impurities.
- Liquid or gas mixtures prepared by stoichiometric mixing of the components in the right proportion.
- Preparation of synthetic mixture of components of interest in right proportions to arrive at a universally acceptable matrix composition. Standards can also be collected from specified sources such as mineral from a particular location, water from a particular natural water body such as river, lake, sea, etc.
- Physico-chemical standards with characteristic properties such as melting point, boiling point, light transmittance, viscosity, hardness, etc which can be used for establishing identity of materials.
- Food standards developed for desired taste, odour, colour, texture, etc.
The basis of correct use of standards is their proper storage under recommended conditions, proper handling and replacement before date of expiry without a break in the traceability chain.