Investigation of Silanol Catalyzed Generation of Cyclopenta[c]Pyrrole Derivative Artifact Peaks During RP‐HPLC Impurity Profiling

ABSTRACT During the stability studies of a new chemical entity (NCE‐01), it was observed that a couple of impurities were appearing in both standard and stability samples. Initial analysis report indicated that they were absent in both standard and drug substance loaded for stability. The mass spectrometric analysis indicated that both could be oxidative cyclized cyclopenta[c]pyrrole derivative products, which were also observed during the photolytic forced degradation studies. However, their presence was not consistent during stability analysis, and they were behaving like ghost peaks. Subsequent investigations revealed that these degradation products (ghost peaks) were generated during analysis within the column on the loss of two hydrogens, most likely on interaction of the drug substance with free silanol(s) and/or residual amount of heavy metals. Catalytic effect of metals potentially present in the column such as ruthenium (III), iron (III), nickel (II), chromium (III), and titanium (IV) was evaluated outside the column by exposing the drug substance with them, however, except ruthenium, other heavy metals failed to produce these impurities. To confirm the catalytic role of ruthenium, another drug analog was also tested, and that too showed the formation of similar degradation products. A mitigation strategy was then developed to reduce/avoid the generation of such on‐column ghost peaks by implementing measures such as increasing the buffer strength and substituting acetonitrile with methanol in the mobile phase.