Capillary electrophoresis-electrochemiluminescent detection of N,N-dimethyl ethanolamine and its application in impurity profiling and stability investigation of meclophenoxate.

Numerous drugs are carboxylic acid derivatives containing amino group, and hydrolysis reaction of these agents often generates toxic amines. Thus, the detection of amine impurity is of great importance in drug quality control of these amino group-containing ester and amide. A capillary electrophoresis method coupled with end-column electrochemiluminescent detection based on tris(2,2'-bipyridyl)ruthenium(II) system was proposed for the analysis of N,N-dimethyl ethanolamine (DMEA, the degradation product of meclophenoxate) in the presence of its precursor. Baseline separation of DMEA and meclophenoxate can be easily achieved under the selected conditions. DMEA can be assayed within 3 min over the concentration range of 5.0x10(-8) to 3.0x10(-6) mol L(-1) with a detection limit of 2.0x10(-8) mol L(-1) at the signal-to-noise ratio of 3. The relative standard deviations of the signal intensity and the migration time were less than 5.3 and 2.5% for a standard sample containing 1.0x10(-7) mol L(-1) DMEA (n=5), respectively. The presented method has been successfully applied for the profiling of DMEA resulting from the hydrolysis of meclophenoxate in commercial formulations. A primary stability investigation of meclophenoxate in aqueous solution was also carried out at different temperatures, and the results showed that the degradation of meclophenoxate accelerated at the higher temperature.