Stability-Indicating Method Development and Validation for Busulfan Drug Substance by Gas Chromatography-Flame Ionization Detector.

A new, simple and stability-indicating gas chromatography-flame ionization detection (GC-FID) method was developed and validated for the quantitative determination of busulfan and its organic impurities (OI) in drug substance without derivatization. The chromatographic attributes were achieved on a fused silica capillary column (0.53 mm × 30 m, 1.0 μm, USP Phase G42), using hydrogen as a carrier gas with a split ratio of 1:1. Forced degradation studies were conducted to establish the stability-indicating capability and method specificity that showed the stressed busulfan peak was free from any co-elution. Robustness study demonstrated the chromatograms remained mostly unaffected under deliberate, but small variations of chromatographic parameters, establishing the reliability of the method during routine usage. The method was shown to be reliable, sensitive, specific, linear, accurate, precise and rugged in the 1,4-butanediol concentration range of 1-20 μg/mL. The method, intended for compendial uses, is suitable for quantitative analysis of busulfan and its organic impurities in drug substances.