Light stabilizing activity, test method

The light-stabilization activity of several esters was tested by an improved test method (25). This method was carried out as follows (i) Preparation of the test specimen. A mixture of 100 parts... 

The amount to be applied to the layer in stability testing is governed in particular by the sensitivity of the method of detection and the related question, beyond what degree of decomposition the activity of the preparation becomes really impaired or the decomposition products show an undesireable side effect. An example may be seen in Fig. 168. The resolved steroid mixture can be detected with either dinitrophenyl-hydrazine (Rgt. No. 82) or sulphuric acid (Rgt. No. 241B), followed by inspection in UV light. In this particular case, the sulphuric acid reaction is too sensitive, since it detects impurities and degradation products which are without therapeutic interest [64]. 

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