Abstract:

A two-dimensional ultra performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (2D-UPLC-Q/TOF-MS) method was established for the separation and structural analysis of the components in teicoplanin. This method effectively solved the problems associated with chromatographic systems, such as liquid chromatography-mass spectrometry (LC-MS), which used a non-volatile phosphate buffer as the mobile phase and were not suitable for the rapid identification of impurities. Moreover, this method circumvented the complexities associated with locating and identifying impurities using the original method by re-establishing a chromatographic system suitable for LC-MS. In this study, for one-dimensional (1D) chromatography, the chromatographic separation was performed on an Octadecyl silica (ODS) hypersil column (250 mm×4.6 mm, 5 μm) with gradient elution using 3.0 g/L sodium dihydrogen phosphate buffer (pH 6.0)/acetonitrile=9/1 (v/v) as mobile phase A and 3.0 g/L sodium dihydrogen phosphate buffer (pH 6.0)/acetonitrile=3/7 (v/v) as mobile phase B. The column temperature was maintained at 30 ℃ and an ultraviolet detector was used at 254 nm for analysis. For 2D chromatography, desalting was performed on a Waters ACQUITY UPLC BEH C₁₈ column (50 mm×2.1 mm, 1.7 μm) with gradient elution using ammonium formate buffer (pH 6.0) and acetonitrile as the mobile phases. The column temperature was maintained at 45 ℃. The MS data for the components and impurities were collected by positive ion electrospray ionization (ESI) using the full-information tandem MS mode (MS^E). The cone and nebulizer gas flow rates were set at 50 and 900 L/h, respectively. The ion source and nebulizer gas temperatures were set at 120 ℃ and 500 ℃, respectively. The ESI and cone needle voltages were set at 2500 and 60 V, respectively. The collision energy was set at 20-50 eV. The molecular formulas of the components and impurities were determined using their exact masses and isotope distributions, and the structural components and impurities of teicoplanin were deduced from their fragment ions according to the fragmentation pathway of the TA_2-2 component. Moreover, the 10 components reported in the European Pharmacopoeia 10.0 were analyzed and 22 impurities of teicoplanin were identified by 2D-UPLC-Q/TOF-MS. Three new impurities and two characteristic fragment ions of the teicoplanin parent nucleus were detected, and the fragmentation pathway of TA_2-2 was deduced. Using this method, 1D-UPLC is applicable for the accurate qualification of components based on relative retention times, and 2D-UPLC-Q/TOF-MS is suitable for the rapid identification of the structure of components based on their fragment ions. The results indicate that 2D-UPLC-Q/TOF-MS may be used to analyze the structure of impurities in teicoplanin based on their exact masses, isotope distributions, and fragment ions. The method is rapid, simple, and sensitive, which provides a novel strategy for the quality control and process optimization of teicoplanin.

Key words: two-dimensional ultra performance liquid chromatography (2D-UPLC), quadrupole/time-of-flight mass spectrometry (Q/TOF-MS), teicoplanin, impurity, analysis