Development of trace analysis for alkyl methanesulfonates in the delgocitinib drug substance using GC-FID and liquid–liquid extraction with ionic liquid

Abstract

Alkyl methanesulfonates are genotoxic impurities that should be limited to an intake of not more than 1.5 µg/day, as regulated by the International Council for Harmonization guideline M7. We herein report a trace analysis of methyl methanesulfonate (MMS), ethyl methanesulfonate (EMS), and isopropyl methanesulfonate (IPMS) in the delgocitinib drug substance using liquid–liquid extraction, with an ionic liquid as the sample-solving medium, and direct injection gas chromatography detected with a flame-ionization detector. The proposed method takes advantage of the fine solubility of ionic liquids toward the drug substance, the good extraction efficiency of alkyl methanesulfonates in liquid–liquid extraction using the Chem Elut cartridge with low-polar organic solvents, and the ability of alkyl methanesulfonates to concentrate in minimum amounts of organic solvent, resulting in excellent sensitivity and selectivity. Specifically, for the preparation of the sample solution, a mixture of 1-butyl-3-methylimidazolium chloride, water, and acetonitrile was used as the sample-solving media, extracted with diethyl ether, and the eluent was concentrated to 1 mL. The method showed good linearity, accuracy, and precision from 1 to 5 ppm, and the limits of detection of MMS, EMS, and IPMS were 0.1, 0.05, and 0.05 ppm, respectively.