Validation of a reversed-phase HPLC method for 1,10-phenanthroline-5,6-dione and analysis of its impurities by HPLC-MS.

A reversed-phase HPLC analytical method for the assay of 1,10-phenanthroline-5,6-dione (I) has been developed and validated. A C18 column (150 x 4.6 mm; 5 microm) was employed together with a mobile phase of methanol-water (50:50, v/v) containing 0.1% triethylamine. UV detection was performed at 254 nm. Dione (I) eluted as a spectrally pure peak resolved from its impurities allowing the method to be applied to the purity evaluation of samples obtained via two synthetic routes. In addition, 4,5-diazafluoren-9-one (V) was identified as the main impurity by employing the method in HPLC-MS mode with photodiode array UV detection.