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Liquid chromatography/mass spectrometry (LC/MS) identification of photooxidative degradates of crystalline and amorphous MK-912

✍ Scribed by Xuezhi Qin; Patricia Frech

Publisher
John Wiley and Sons
Year
2001
Tongue
English
Weight
185 KB
Volume
90
Category
Article
ISSN
0022-3549

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✦ Synopsis

How and why the chemical stability of amorphous solid is different from crystalline solid is an important problem. In this study, this problem is addressed by evaluation of the photodegradation of both crystalline and amorphous MK-912 (an a-2 adrenoceptor antagonist) according to the photostability tests of the ICH (International Conference on Harmonization) guidelines. Under the ICH conditions, the photodegradation rate of the amorphous MK-912 was $40 times faster than that of the crystalline MK-912. The photodegradation yielded isomeric, oxidative degradates. Three keto-degradates (molecular weight of 14 Da over MK-912) were observed for both forms. But, whereas ®ve alcohol and one N-oxide degradates (molecular weight of 16 Da over MK-912) were observed for the amorphous form, only one alcohol degradate was observed for the crystalline form. Liquid chromatography/mass spectrometry (LC/MS) and LC/MS/MS were applied to identify these low-level photodegradates. A thorough analysis of the MS/MS data of protonated MK-912 was the key to the identi®cation, and the special MS/MS features of the degradates due to the structural modi®cations from degradations were also important. Following this strategy, the structures of all the photodegradates were proposed. The structural identi®cation of the photodegradates of MK-912 shed light on the different photostabilities between the crystalline and amorphous MK-912.

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