LAUSR

Minodronic acid (MA) is a third-generation nitrogen-containing heterocyclic bisphosphonate used to treat osteoporosis. In the process of starting materials research and preparation, the key intermediate impurities and degradation impurities have a great impact on the quality control of the drug. A sensitive, reliable high-performance liquid chromatography (HPLC) method was developed and validated for the quantitative determination of MA and its related impurities (a total of 6 compounds, including 2 new impurities). The separation was achieved on an InertSustain ODS-4 C18 (250 mm×4.6 mm, 5 μm) column using the mixture of 0.01 mol/L sodium pyrophosphate and 1 mmol tetrabutylammonium phosphate (the mobile phase pH was adjusted to 7.80 by phosphonic acid). The quantitative analytical method was fully validated with respect to linearity (r>0.999), sensitivity (limit of detection<35 ng/mL), precision, accuracy (the recovery was between 98.7% and 104.2%), and robustness. Six process-related impurities in Minodronic Acid (MA) bulk drugs were determined by high-performance liquid chromatography (HPLC). Furthermore, except for two starting materials, other four impurities were identified and characterized as 2-(imidazo[1,2-a] pyridin-3-yl) ethyl acetate (Imp-C), 2-(imidazo [1,2-a] pyridin- 3-yl)acetic acid (Imp-D), 3-(2-hydroxy-2,2- diphosphonoethyl)-4H-imidazo [1,2-a] pyridine -4- oxide (Imp-E) and 2,5- Dihydroxy- 3,6-bis(imidazo[1,2-a] pyridine-3-yl methyl) -2,5-dioxo-1,4,2,5- dioxoDiphosphonium-3,6-diyl) bisphosphonic acid (Imp-F) using liquid chromatograph-mass spectrometer (LC-MS), MS/MS, Infrared Radiation and Nuclear Magnetic Resonance spectroscopy (1H-NMR and 13C-NMR). To the best of our knowledge, two of them (Imp-E and Imp-F) are new compounds and have not been reported previously. The HPLC method was developed and optimized, which could be applied for quantitative detection of the impurities, and further quality evaluation of MA.