ABSTRACT
OBJECTIVE: To establish an HPLC-UV-ESI-MSn method for the study of impurity profile of amoxicillin and clavulanate potassium tablets. METHODS: Agilent 1100 LC/MSD Trap liquid chromatography-mass spectrometry was used, and the column was Shim pack CLC-ODS RP18(4.6 mm×250 mm, 5 μm). The mobile phase A was 20 mmol·L-1 ammonium acetate (pH adjusted to 6.0), and the mobile phase B was 20 mmol·L-1 ammonium acetate-acetonitrile (20∶80) (pH adjusted to 6.0). Gradient elution was performed at a flow rate of 1.0 mL·min-1. ESI source was used. Positive and negative ion scan was conducted with a scanning range of m/z 100-1 500. The nebulizing pressure was 275.8 kPa, dry gas flow was 9 L·min-1, and post-column diversion ratio was 1∶5. Some related substances were identified by comparing the retention time in the chromatography, [M+H]+ spectrum and MS2 spectrum with those of the reference substances, while the others which do not have reference substances were deduced or speculated by analyzing the MS2 or MSn fragmentation with the help of a rule summarized from the MS2 fragmentation of amoxicillin, clavulanic acid and system suitability impurity reference substances. RESULTS: A total of 15 related substances were separated and characterized including nine known impurities like amoxicilloic acid, amoxicillin dimer, etc. and six unknown impurities. CONCLUSION: The method can be applied in the identification and qualitative analysis of the related substances in amoxicillin and clavulanate potassium tablets and is helpful for the quality control and optimization of the synthetic process.