The validation is based on the instrumental and objective colour evaluation of optically clear tinted liquids as specified in the European Pharmacopoeia, chapter 2.2.2. "Degree of coloration of liquids"
(http://www.pheur.org/). Even today, many pharmaceutical products are still assessed by visual methods to detect colour changes during production, storage or ageing.
The visual subjective comparison with colour reference solutions according to the Ph.Eur.- specifications often involves problems if one product is judged by several persons. Human colour
perception is considerably influenced by surroundings, light and mental state of the person. Moreover, no method is defined to check colour reference solutions for colour fastness and constancy. Usually
the user has to depend on the standards being replaced in regular intervals and stored orderly at any time.
This method was elaborated to develop a suitable measuring procedure on the basis of existing
national and international regulations and standards that should enable objective instrumental colour comparisons to be made.