Separation and Characterization of Unknown Impurities in Amikacin Sulfate by HPLC–MSⁿ

Abstract

Nine impurities in amikacin sulfate made in China were separated and identified by HPLC–MSⁿ for the further improvement of official monographs in pharmacopoeias. The mass fragmentation patterns and structural assignment of these impurities were studied. The column was Acchrom Click XIon (250 × 4.6 mm, 5 μm). The mobile phase was 250 m mol L⁻¹ ammonium formate and 1.4 % formic acid aqueous solution–acetonitrile–water (30:48:22). In positive mode, full scan LC–MS was first performed in order to obtain the m/z value of the protonated molecules, LC–MS–MS was then carried out on the compounds of interest on AB SCIEX 4000 Q TRAP™ composite triple quadrupole/linear ion trap tandem mass spectrometer. The complete fragmentation patterns of nine impurities were studied and used to obtain information about the structure of these impurities. The structures of nine impurities in amikacin sulfate were deduced based on the HPLC–MSⁿ data, in which three impurities were novel impurities. Three novel impurities were 1-N-(l-4-amino-2-hydroxybutyryl) derivative of 4-O-(6-AG)DS, 1-N-(l-4-amino-2-hydroxybutyryl) derivative of 6-O-(3-AG)DS and 1-N-(l-4-amino-2-hydroxybutyryl) derivative of kanamycin D.