Maximum degradation of diacerein was observed in alkaline cisplatin mechanism of action medium, followed by decomposition under thermal degradation and photolysis. The drug was stable to acid hydrolysis and oxidative conditions. Percent degradation of diacerein under all stressed conditions and retention time of the degradation products are included in Table 1. Separation of diacerein from its degradation products has been performed on an RP C18 column. Initially water and acetonitrile in various proportions were tried. However, good resolution between peaks was not obtained. Different ratios of orthophosphoric acid in water (pH 2.9) and acetonitrile were tried. Increasing the acetonitrile ratio was accompanied by a decrease in retention time of the different components; however, separation was still achieved.
In order to ensure complete separation and high resolution, the chosen ratio was 50 : 50 (% v/v). Simultaneous monitoring with the PDA detector was carried out at a range of wavelength between 200 �C 400 nm. Detection was carried out at 257 nm, where maximum sensitivity was observed. The specificity of the method is illustrated in all the chromatograms of the degradation studies. Validation of the method The method was validated with respect to parameters like linearity, precision, accuracy, specificity, and robustness. The LOD and LOQ concentrations were found to be 0.10 and 0.50 ��g/ml. Results from the regression analysis with system-suitability data are listed in Table 2. Results of precision and accuracy are listed in Table 3.
Influences of small changes in chromatographic conditions, such as, change in flow rate (�� 10%), organic content in the mobile phase (�� 2%), wavelength of detection (�� 5%), and pH of buffer in the mobile phase (�� 0.2%) were studied, to determine the robustness of the method. The RSD was < 2% in all cases. The RSD values of the assay of diacerein during solution stability experiments Cilengitide were < 2%. No significant changes were observed during solution stability. The solution stability data confirms that the sample solutions were stable for at least seven days. Table 2 Results from regression analysis and system suitability of diacerein Table 3 Precision and recovery data CONCLUSIONS The study concludes that diacerein is most labile to alkaline hydrolysis followed by thermal degradation and photolysis. It is stable to acid hydrolysis and oxidative stress conditions. The proposed method is sensitive, precise, accurate, and stability-indicating, resolving all the degradation products from the drug. Thus, the proposed method can have its application in the determination of diacerein in bulk drug, pharmaceutical formulation, as well as in the presence of all its degradation products.