Stability Tests on Pharmaceutical Materials

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]. 

TLC has been often employed for qualitative stability testing. Thus, preparations containing nicotinate esters have been tested for 

Unknown products or substances which interfere with available quantitative methods of determination occur frequently during the degradation of active compounds in drugs. In such cases, it is advantageous to isolate the undecomposed active compound with the help of TLC, following then with quantitative evaluation (cf. Chapter H). 

Eye drops containing fluprednisolone acetate have been tested [80] in a way similar to that previously described for hydrocortisone acetate preparations [63], After submitting to appropriate test conditions, the steroid extracts were chromatographed on fluorescent silica gel layers, the separated steroid ester and alcohol spots localised in UV light, eluted and determined quantitatively by UV spectrophotometry or colorimetrically with tetrazolium compounds. The stability of tablets containing oestr-4-en-17 jS-ols and the influence of the quality of the auxiliary material 

The possibility of carrying out quantitative stability tests on aqueous preparations of ergot alkaloids, using TLC, has also been reported [85,178] reference may be made too to the semi-quantitative detection of free nicotinic acid in polyvitamin preparations containing nicotinamide [113]. 

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