005 and 0.0025 μg/ml respectively. The LOQ was 0.0175 and 0.00875 μg/ml of Metronidazole and Norfloxacin respectively. The results show very Trichostatin A good sensitivity of the developed method. Precision of the assay was determined by repeatability (intra-day) and intermediate precision (inter-day). The precision of the method was evaluated by carrying out five independent assays of the

sample. The intermediate precision was carried out by analyzing the sample at different day. Percentage of relative standard deviation was found to be less than 2% for within a day and day to day variations, which proves that method is precise. The accuracy studies were performed for both Metronidazole and Norfloxacin at three different levels (50%, 100% and 150%) and the mixtures were analyzed by the proposed method. The experiment was performed in triplicate and the results showed good recovery within limits. Robustness of the proposed method was determined by small deliberate changes in flow rate, change in composition of mobile phase ratio. The content of the drug was not adversely affected by these changes as evident from the low Screening Library value of RSD indicating that the method was rugged and robust (Table 3). The proposed method was applied to the

determination of Metronidazole and Norfloxacin in commercial dosage form Nor-metrogyl tablets and the result of these assays yielded 99.4 and 100.5% for Metronidazole and Norfloxacin respectively with RSD <2%. The result of the assay (Table 4) indicates that the method is selective for the assay of Metronidazole and Norfloxacin without interference from the excipients used in these tablets. MTMR9 To further confirm the stability indicating nature of the analytical method, Metronidazole and Norfloxacin were subjected to

stress testing as per ICH guidelines. The objective of stress study was to generate the degradation products under various stress conditions. The stress conditions varied both in terms of temperature and time to achieve the appropriate degradation. The spectral purity of the main peaks was evaluated using photodiode array detector to verify that the degradation peaks are well resolved from the main peaks. All degradation studies in solution were carried out at a drug concentration at 1000 μg/ml. Acid degradation was carried out in 0.1 N HCl and base degradation was carried out in 0.1 N NaOH. Both solutions are kept at room temperature for 90 min. Oxidative degradation studies were carried out in 3% H2O2 at room temperature for 15 min. Thermal degradation was carried out in water for 60 min at 60 °C. After the degradation treatments were completed, the stress content solutions were allowed to room temperature and diluted with mobile phase up to the mark. Filter the solution with 0.45 μ filters and injected to column under proposed conditions.