WHO Expert Committee on Specifications for Pharmaceutical Preparations - WHO Technical Report Series, No. 885 - Thirty-fifth Report
(1999; 168 pages) [Spanish] View the PDF document
Table of Contents
View the documentWHO Expert Committee on Specifications for Pharmaceutical Preparations
View the document1. Introduction
Open this folder and view contents2. The international pharmacopoeia and related issues
Open this folder and view contents3. International Chemical Reference Substances and Infrared Reference Spectra
Open this folder and view contents4. Quality control - national laboratories
Open this folder and view contents5. Good manufacturing practices
Open this folder and view contents6. Quality systems and inspection
Open this folder and view contents7. Other quality assurance topics
Open this folder and view contents8. Nomenclature and terminology
Open this folder and view contents9. Legal aspects of pharmaceuticals
Open this folder and view contents10. Regulatory issues
Open this folder and view contents11. Training activities
View the document12. Pharmaceuticals contaminated with diethylene glycol
View the documentAcknowledgements
View the documentReferences
View the documentAnnex 1. List of available International Chemical Reference Substances1
View the documentAnnex 2. List of available International Infrared Reference Spectra1
Close this folderAnnex 3. General guidelines for the establishment, maintenance and distribution of chemical reference substances
View the documentIntroduction
Close this folderPart A. Primary chemical reference substances
View the document1. Assessment of need for the establishment of chemical reference substances
View the document2. Obtaining source material
Open this folder and view contents3. Evaluation of chemical reference substances
Open this folder and view contents4. Chemical and physical methods used in evaluating chemical reference substances
View the document5. Assignment of content
Open this folder and view contents6. Handling and distribution of chemical reference substances
View the documentPart B. Secondary chemical reference substances
View the documentReferences
Open this folder and view contentsAnnex 4. Good manufacturing practices: authorized person - role, functions and training
Open this folder and view contentsAnnex 5. Good manufacturing practices: supplementary guidelines for the manufacture of pharmaceutical excipients
Open this folder and view contentsAnnex 6. Guidelines for inspection of drug distribution channels
View the documentAnnex 7. Good pharmacy practice in community and hospital pharmacy settings
Open this folder and view contentsAnnex 8. National drug regulatory legislation: guiding principles for small drug regulatory authorities
Open this folder and view contentsAnnex 9. Provisional guidelines for developing training programmes: inspection and examination of counterfeit pharmaceuticals
View the documentWorld Health Organization Technical Report Series
View the documentSelected WHO Publications of Related Interest
View the documentBack Cover
 

1. Assessment of need for the establishment of chemical reference substances

The production, validation, maintenance and distribution of chemical reference substances is a costly and time-consuming undertaking. It is therefore of great importance to determine critically whether a need for a given substance exists. Requests for new chemical reference substances usually arise when a particular approach to developing a specification for a new substance or product has been adopted. Methods may have been proposed in a specification that require the establishment of a chemical reference substance for use as a comparative standard. Therefore, the first matter that should be assessed is whether an alternative, equally satisfactory, procedure could be adopted that does not require a comparative standard.

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

(a) infrared (IR) spectrophotometry, whether for identification or quantitative purposes;

 

(b) quantitative methods based on ultraviolet (UV) absorption spectrophotometry;

(c) quantitative methods based on the development of a colour and the measurement of its intensity, whether by instrumental or visual comparison;

(d) methods based on chromatographic separation for identification or quantitative purposes;

(e) 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 efficiency of the extraction procedure might depend upon ambient conditions that vary from time to time and from laboratory to laboratory;

(f) quantitative methods, often titrimetric but sometimes gravimetric, that are based on non-stoichiometric relationships;

(g) assay methods based on measurement of optical rotation; and (h) 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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