Identification of Unknown Impurities in Polymyxin B Sulfate by HPLC-MS/MS / 中国药学杂志

ABSTRACT

OBJECTIVE: To establish an HPLC-MS/MS method to identify the unknown impurities in polymyxin B sulfate. METHODS: The analysis was performed on Agilent 1260-6550 Q/TOF-MS with a Diamonsil Plus C18 column(4.6 mm×250 mm, 5 μm). Mobile phase A was 0.01 mol•L-1 trifluoroacetic acid-acetonitrile(955), and mobile phase B was acetonitrile containing 0.1% formic acid. Mobile phase A and B were set at the volume ratio of 7921 at a flow rate of 1 mL•min-1 under isocratic elution. The detection wavelength was set at 254 nm. ESI source was used. Positive ion scanning was conducted in the range of m/z 50-1 700 for MS and MS/MS. The unknown components were identified by comparing the MS and MS/MS with the known reference standards like polymyxin B1 and B2. The photochemical Paterno-Büchi reaction was performed using a low-pressure mercury lamp as the light source at emission wavelength of 254 nm with acetone/water(50/50, V/V) as the reaction solvent. RESULTS: The structures of seven unknown related substances in polymyxin B sulfate were identified. The most abundant impurity was identified to be vinyl polymyxin B1, for which the double bond was at the end of the fatty acyl residue. CONCLUSION: Vinyl polymyxin B1 is reported for the first time. The method provides a good idea for the identification of related substances in drugs.