A new stability indicating HPLC method with QDa and PDA detectors for the determination of process and degradation impurities of ivabradine including separation of diastereomeric N-oxides†

In this study, a new reversed phase high performance liquid chromatography method using two detectors was developed for the analysis of degradation and process impurities of ivabradine in pharmaceutical preparations. A PDA detector set to 285 nm wavelength and a QDa detector set to positive scan mode were used in the method. In the developed method, the separation process was carried out in a Zorbax phenyl column with a gradient application of a 0.075% trifluoroacetic acid, acetonitrile, and methanol mixture at a flow rate of 1.5 ml min⁻¹. During the degradation studies, the samples were exposed to acidic, alkaline, oxidative, thermal, and photolytic conditions. Process-related impurities were separated not only without interfering with each other but also with the degradation product and ivabradine peaks, and thanks to QDa, all impurities could be identified with their molecular weights. This method, in addition to providing stability data, was also able to separate two diastereomeric N-oxide impurities which are major oxidative degradation impurities of ivabradine having a chiral center. Some additional measurements such as solubility, specific rotation, melting point and differential scanning calorimetry analysis proved the formation of the two diastereomeric N-oxide impurities under oxidative conditions. Method validation was performed according to the International Council for Harmonization guidelines and the analysis of ivabradine, its process related impurities (dehydro ivabradine, acetyl ivabradine, and hydroxy ivabradine) and a major oxidative degradation product (ivabradine N-oxide) was successfully performed by this method.