Abstract: Using high performance liquid chromatography and high resolution orbital trap mass spectrometry, a two-dimensional online desalting detection method was established to determine the structure of the impurities detected under the official testing conditions of lansoprazole enteric solution preparation, and a chromatographic method compatible with mass spectrometry was established to determine and presume the structure of the impurities that could not be separated by the the official testing method.The identification of impurity was to presume its structure according to the presence of impurity reference product, so as to investigate the difference of impurity spectrum of products from different manufacturers.The one-dimensional chromatographic conditions for the 2D online desalting method were the same as those in China Pharmacopoeia (2020) under relevant substances.Two-dimensional chromatography was performed on a Waters C₁₈ T3 column (2.1 mm × 100 mm, 1.7 μm) with 0.1% formic acid in water-acetonitrile mobile phase and gradient elution.The chromatographic conditions for the compatible mass spectra were based on an Agilent Extend C₁₈ (4.6 mm × 150 mm, 5 μm) column with mobile phase A: 25 mmol/L ammonium acetate and B: 25 mmol/L ammonium acetate-acetonitrile (1∶4) pH adjusted to 6.5 with glacial acetic acid, with gradient elution. Nine impurities were detected by two-dimensional online desalting method, with 5 known impurities (A-E) and 4 unknown ones.14 impurities were detected by the compatible mass spectrometry method, with 9 unknown impurities (4 consistent with the results of two-dimensional online desalting method, and 5 newly detected).The structures and sources of the unknown impurities were deduced.The two detection methods of lansoprazole preparation by high-performance liquid chromatography-high resolution orbital trap mass spectrometry have guiding significance for quality control and process evaluation.