A stability-indicating method for the determination of melphalan and related impurity content by gradient HPLC

A robust gradient high performance liquid chromatographic (HPLC) procedure is described for the simultaneous determination of melphalan content and re lated impurities in melphalan drug substance. The sample solution is prepar ed in methanol and injected. A linear gradient from 5 to 60% acetonitrile i n water containing 0.05% v/v acetic acid, 0.01% v/v triethylamine, and 0.05 % w/v ammonium acetate is applied over 20 min. The chromatographic conditio ns are capable of separating and quantifying all impurities found in routin e production batches of melphalan at above 0.1% area/area. The method has b een fully validated and is linear over the column loading range of 0-3 mu g of melphalan. All related impurities occurring in routine batches at above 0.1% area/area have been identified, and structures assigned. The method h as been applied to melphalan samples stored under stressed conditions, and shown to be stability-indicating. (C) 1999 Elsevier Science B.V. All rights reserved.