Stability study of the anticonvulsant enaminone (E118) using HPLC and LC-MS

The stability of the new chemical synthetic enaminone derivative (E118) was investigated using a stability-indicating high-performance liquid chromato graphy (HPLC) procedure. The examined samples were analyzed using a chiral HSA column and a mobile phase (pH 7.5) containing n-octanoic acid (5 mM), i sopropyl alcohol and 100 mM disodium hydrogen phosphate solution (1:9 v/v) at a flow rate of 1 ml min(-1). The developed method was specific, accurate and reproducible. The HPLC chromatograms exhibited well-resolved peaks of E118 and the degradation products at retention times <5 min. The stability of E118 was performed in 0.1 M hydrochloric acid, 0.1 M sodium hydroxide, w ater/ethanol (1:1) and phosphate buffer (pH <similar to> 7.5) solutions. E1 18 was found to undergo fast hydrolysis in 0.1 M hydrochloric acid solution . The decomposition of E118 followed first order kinetics under the experim ental conditions. The results confirmed that protonation of the enaminone s ystem in the molecule enhanced the hydrolysis of E118 at degradation rate c onstant of 0.049 min(-1) and degradation half-life of 14.1 min at 25 degree sC. However. E118 was significantly stable in 0.1 M sodium hydroxide, physi ological phosphate buffer (pH 7.5) and ethanol/water (1:1) solutions. The d egradation rate constants and degradation half-lives were in the ranges 0.0 023-0.0086 h(-1) and 80.6-150.6 h, respectively. Analysis of the acid-induc ed degraded solution of E118 by liquid chromatography-mass spectrometry (LC -MS) revealed at least two degradation products of E118 at m/z 213.1 and 11 3.1, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.