To estimate the limits of detection (LOD) and quantification (LOQ), blank methanol was applied (n = 6) and the standard deviation (��) of the analytical response was determined. The LOD and LOQ values were calculated from the calibration curves as k��/b, where k = 3.3 for LOD and 10 for LOQ, �� Idelalisib mw is the standard deviation of the intercept, and b is the slope of the calibration curve. Determination of stability The forced degradation of SRT was carried out under the condition of acid, neutral, alkaline, Inhibitors,Modulators,Libraries and oxidative hydrolysis. Appropriate amount of SRT was dissolved in methanol to prepare SRT stock solution concentration of 400 ��g/ml. One milliliter of SRT stock solution was transferred into each of four glass vials.
One milliliter of HCl (1 N) was added into first vial, 1 ml of NaOH (10 N) into the second vial, 1 ml of water into third vial, and finally 1 ml Inhibitors,Modulators,Libraries of the solution of 3% H2O2 into the fourth vial. All vials were tightly closed and maintained at constant temperature (90��C) in a heating block with simultaneous stirring. After the periods Inhibitors,Modulators,Libraries of Inhibitors,Modulators,Libraries 30, 60, 180, and 360 min, 20 ��l of each sample was analyzed employing HPLC. The blanks consisting of 1 ml of methanol and 1 ml of degradation medium were injected on to the column before every single analysis. In order to determine relative rate of hydrolytic decomposition of the drug, the logarithm of remaining concentration of SRT was plotted versus time. The rate constants were calculated from the slope of the kinetic curves. RESULTS AND DISCUSSION Optimization of mobile phase The HPLC procedure was optimized with a view to developing a method for stability-indicating assay in stressed samples.
No internal standard was used because no extraction or separation step was involved. Of the several solvents and solvent mixtures investigated, methanol�Cwater 75:25 (%, v/v) was found to furnish sharp, well-defined peaks with very good symmetry (1.25) and low tR (7.05 �� 0.12 Inhibitors,Modulators,Libraries min) [Figure 2]. With acetonitrile�Cwater 75:25 as the mobile phase, tR was 9.5 min and peak shape and sensitivity were poor. Acetonitrile was also more expensive than methanol. Methanol�Cwater 95:05 and methanol�Cwater 50:50 did not furnish sharp, well-defined peaks, and other mobile phases tried either resulted in much lower sensitivity or did not give well-defined peaks in a short time, and so were not considered.
The final decision on mobile phase composition and flow rate was made on the basis of peak shape (peak area, asymmetry, tailing factor), baseline drift, time required for analysis, and cost of solvent, and methanol�Cwater 75:25 (%, v/v) was selected as the optimum mobile phase. Under these conditions, the retention time and asymmetry factor were 7.05 min and 1.25, respectively. Entinostat Figure 2 Chromatogram of standard SRT (200 ��g/ml); Rt: 7.05 �� 0.