stability indicating.

To develop rapid, rugged, precise and an accurate stability indicating analytical method for estimation of related substances in Ursodeoxycholic Acid tablets. The separation of impurities and Ursodeoxycholic Acid drug is achieved by an isocratic chromatographic method on C18, 250 mm x 4.6 mm, 5µm column. The mobile phase consists of buffer, acetonitrile and methanol in the ratio of 35:28:37 v/v/v pumped at a flow rate of 1.0 ml/minute 35:37:28v/v/v pumped at a flow rate of 1.0 ml/minute. The detection was carried out by using refractive index (RI) detector. The proposed chromatographic method was validated and found to be linear over the concentration range from LOQ to 150.0% of impurity limit level.  Overall mean recovery of Chenodeoxycholic acid impurity was found to be 100.6±4.0%w/w The method was found to be simple, stability indicating, precise, accurate and robust which can be utilized for estimation of related substances in Ursodeoxycholic Acid tablets

A stability indicating reverse phase High performance liquid chromatography (RP-HPLC) method has been developed and subsequently validated for the simultaneous determination of Atazanavir and Cobicistat in bulk and pharmaceutical formulation. Separation was achieved in isocratic mode with a Kinetex C18 100 A (250 mm x 4.6 mm,  5µ) column and mixture consisting of 0.1% OPA(pH 3) and methanol in 80:20 v/v was used as mobile phase with a flow rate of 1 ml/min, column temperature at 25°C and the run time as 10 mins. UV detection was performed at 239 nm and the sample temperature was maintained ambient. The described method for simultaneous determination of Atazanavir and Cobicistat is linear over a range of 8 μg/ml to 120 μg/ml and 5 μg/ml to 60 μg/ml respectively. The method shows good precision results which were below 2.0%RSD. Limit of Detection (LOD) and Limit of Quantification (LOQ) of Atazanavir and Cobicistat was established and found to be 1.49 and 4.97 μg/ml and 1.13 and 3.77 μg/ ml respectively. The developed method was validated according to ICH guidelines for various parameters.The method is simple, rapid, selective and stability indicating method which would be used for regular stability indicating quality control determinations.