In Quality Control Laboratory different types of standards are used for different purposes. Below is a brief information on the standards used in QC Laboratories.

The purpose of establishing chemical reference substances is to achieve accuracy and reproducibility of the analytical results required by pharmacopoeial testing and pharmaceutical control in general. These substances are normally prepared and issued by the regional or national pharmacopoeia commission or the regional or national quality control laboratory on behalf of the drug regulatory authority.

The purpose of establishing secondary reference substances is for use in routine analysis to determine the identity, purity and, in particular, the content of pharmaceutical substances in pharmaceutical preparations. The extent of characterization and testing of a secondary reference substance is less
than that for a primary reference substance. It is essential that a secondary reference substance is traceable to a primary reference substance, such as a pharmacopoeial or other officially recognized reference substance.
In principle, secondary reference standards prepared by manufacturers can be prepared as “working standards” using the same procedures. The traceability between the secondary and the primary chemical reference substance must be documented.

A) Chemical reference substance (Standard)
The term chemical reference substance refers to an authenticated, uniform material that is intended for use in specified chemical and physical tests, in which its properties are compared with
those of the product under examination, and which possesses a degree of purity adequate for its intended use.

B) Primary (Standard) Chemical reference substance
A designated primary chemical reference substance is one that is widely
acknowledged to have the appropriate qualities within a specifi ed context,
and whose assigned content when used as an assay standard is accepted
without requiring comparison with another chemical substance.

C) International Chemical Reference Substance (ICRS)
International Chemical Reference Substances (ICRS) are primary chemical
reference substances established on the advice of the WHO Expert
Committee on Specifications for Pharmaceutical Preparations. They
are supplied primarily for use in physical and chemical tests and assays
described in the specifi cations for quality control of drugs published in The
International Pharmacopoeia or proposed in draft monographs. The ICRS
may be used to calibrate secondary standards.

D) Secondary (Standard) Chemical reference substance - Working Standard
A secondary chemical reference substance is a substance whose
characteristics are assigned and/or calibrated by comparison with a
primary chemical reference substance. The extent of characterization and
testing of a secondary chemical reference substance may be less than for a
primary chemical reference substance.

E) Pharmacopoeial reference standards
Pharmacopoeial standards and substances are established and distributed by pharmacopoeial authorities.

Analytical procedures currently used in specifications for pharmaceutical substances and products that may require a chemical reference substance (Standards) are:

– infrared (IR) spectrophotometry, whether for identification or quantitative purposes;
– quantitative methods based on ultraviolet (UV) absorption spectrophotometry;
– quantitative methods based on the development of a colour and the measurement of its intensity, whether by instrumental or visual comparison;
– methods based on chromatographic separation for identification or quantitative purposes;
– quantitative methods (including automated methods) based on other separation techniques that depend on partition of the substance to be determined between solvent phases, where the precise effi ciency of the extraction procedure might depend upon ambient conditions that occasionally vary and from laboratory to laboratory;
– quantitative methods, often titrimetric but sometimes gravimetric, that are based on non-stoichiometric relationships;
– assay methods based on measurement of optical rotation; and
– methods that might require a chemical reference substance consisting of a fixed ratio of known components (for example, cis/trans isomers, spiked samples).


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