Development and validation of a HPLC–PDA method for quantitation of metronidazole in finished drug formulation

In the quality control of medicines and the fight against the phenomenon of substandard medicines, rapid and comprehensive methods for screening these types of medicines are urgently needed to better quantification. In the present work, we adopted the RP-HPLC technique for the development of metronidazole for evaluation and quantification in finished pharmaceutical formulations. A simple and novel rapid stability indicating RP-HPLC method for assay and related substances was developed and further validated for the metronidazole tablet dosage form. Chromatographic separation was performed for the assay method, Water Symmetry C18 column with 100 mm × 4.6 mm 3.5 μm and the related substance method Zorbax SB, C8 100 mm × 4.6 mm 3.5 μm using isopropyl alcohol and water (20:80 v/v) as mobile phase. From assay and related substances, the injection repeatability of 0.5% and 0.8% was observed for assay and RS method respectively. The resolution between metronidazole and metronidazole related impurity-A (tinidazole-related compound A) was observed 9.0. The linearity was observed in the concentration range of 75–225 µg/ml and 0.055–7.5 µg/ml with the correlation coefficient r2 = 0.9999 and r2 = 0.9998 for metronidazole and metronidazole impurity A, respectively. The LOD and LOQ values for metronidazole were 0.02 µg/mL and 0.05 µg/mL, while the values for metronidazole impurity A, LOD, and LOQ were 0.05 and 0.17 µg/ml. This study developed a more environmentally friendly approach using isopropyl alcohol (IPA) as a solvent. The greener approach has been implemented to develop a promising method that reduces the difficulties associated with other methods described as laborious to use, less sensitive, costly, etc. As run time of elution was shortened, which effectively reduced solvent consumption, making the method more environmentally friendly. Furthermore, the study revealed that, force degradation of metronidazole impurity A and unspecified impurities were accurately quantified under several International Conference on Harmonization (ICH) recommended stress conditions such as acidic, hydrolysis, oxidation, and heat.