LC-MS IDENTIFICATION OF THE DEGRADATES OF NGP1-O1 AND SUBSEQUENT DEVELOPMENT OF A ROUTINE STABILITY-INDICATING METHOD OF ANALYSIS

NGP1-01 (1) is a heterocyclic cage compound with calcium channel block ing activity similar to that of nifedipine. Since no data on the stabi lity or mechanism of degradation of this type of compound are availabl e, the kinetics of degradation and pH stability were investigated. The degradates formed at pH 2, 5, and 9 were separated and identified wit h LC-MS. Chromatography was performed on a Hypersil phenyl column, 150 x 2.1 mm, flow 0.2 ml/min, mobile phase acetonitrile-0.05 M ammonium acetate pH 4.7, 30/70 for 5 min, then gradient to 65/35 at 10 min. The MS was operated in the electron ionization mode at 70 eV. It was foun d that pH did not have an influence on the mechanism of degradation, a nd the same degradates were observed throughout the pH range investiga ted, namely benzylamine and a heterocyclic keto-alcohol. A method for routine stability-indicating analysis of (1) was developed using a phe nyl column (5 mu m, 250 x 4.6 mm Hypersil) with a mobile phase of acet onitrile-0.01 M ammonium phosphate, 0.3% triethylamine, pH 4.5 60/40. Flow rate was 1 ml/min, injection volume 20 mu l, and UV detection at 210 nm. The method proved usable over a range of 15-1000 mu g/ ml, wit h an accuracy of 100.1 +/- 0.55% and precision of < 2% variance over t he stated range. Reliable kinetic studies could be conducted by using this method of analysis.