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Identification of the Related Substances in Etimicin Sulfate Detected Under the Condition of Chinese Pharmacopoeia 2010 by LC/MSn with Propionic Acid Enhanced Electrospray Ionization

??OBJECTIVE To establish an LC/MSⁿ method for identification of the related substances in etimicn sulfate detected under the chromatographic condition described in Chinese Pharmacopoeia 2010.METHODS The HPLC separation was carried out on a Welch Ultimate LP-C₁₈ column(4.6 mm??300 mm,5 ??m)with mobile phase consisting of 0.2 mol??L^-1trifluoroacetic acid(containing 0.1% propionic acid )-methanol(84??16) at a flow rate of 1.0 mL??min^-1. Thirty percent of the eluent was detected by ion trap mass spectrometry, and the parent ions and the corresponding product spectra of all the related substances in etimicin sulfate were determined and elucidated.RESULTS Addition of 0.1% propionic acid into the mobile phase significantly enhanced the sensitivity of MS detector without altering the chromatographic behavior such as retention time and elution order of the related substances. Twenty-eight related substances were separated and detected by the LC/MSⁿ method in a typical sample. Nine of them were identified with the help of corresponding impurity reference substances and 14 of them were elucidated by MS fragment information, while the other five were not identified due to limitated information. CONCLUSION The established method can be applied to the identification of the related substances in etimicn sulfate detected under the chromatographic condition described in Chinese Pharmacopoeia 2010, which is helpful to the quality improvement and process optimization of etmicin sulfate.