Linearity The linearity of this method was proved using linear co

Linearity The linearity of this method was proved using linear correlation of the peak area values and appropriate concentrations of SRT in a range of 10�C200 ��g/ml. The correlation coefficient of this dependence was calculated to be 0.998 [Table 1]. Table 1 Results of least square regression analysis Precision Precision was considered at two levels, i.e., repeatability and intermediate precision. Repeatability of sample application was determined as intra-day variation, whereas intermediate precision was determined by carrying out inter-day variation at three different concentration levels in triplicates. Results from determination of repeatability and intermediate precision, expressed as RSD (%), are listed in Table 2. The low values of RSD indicate the repeatability of the method. Table 2 Intra-and inter-day precision (n=3) Recovery The recovery of the method, determined by spiking a previously analyzed test solution with additional drug standard solution, was 99.25�C101.86%. The values of recovery (%), RSD (%), and SEM listed in Table 3 indicate the method is accurate. Table 3 Accuracy as recovery (n=3) Robustness To evaluate the method robustness, a few parameters were deliberately varied. Results presented in Table 4 indicate that the selected factors remained unaffected by small variations of these parameters. Insignificant differences in peak areas and less variability in retention time were observed. The standard deviation of peak areas was calculated for each parameter and %RSD was found to be less than 2%. The low values of %RSD indicated robustness of the method. Table 4 Robustness (n=6) LOD and LOQ The LOD and LOQ values were calculated from the calibration curves as kSD/b, where k = 3.3 for LOD and 10 for LOQ, SD is the standard deviation of the intercept, and b is the slope of the calibration curve. The lowest LOD for HPLC and also the LOQ were found to be 28 ng/ml and 85.5 ng/ml, respectively. Stability study HPLC study of SRT hydrolytic decomposition suggested the following degradation behavior. After acid hydrolysis employing HPLC, two degradation products were detected at the retention times of 1.75 and 2.0, respectively [Figure 3]. It was observed that the area values of both peaks were growing in time and this observation was accompanied with decrease in concentration of SRT. The stability of SRT was also studied using water as a medium for degradation. Although both degradation products were detected on chromatogram, the ratio between the areas of peaks was different [Figure 4] in comparison with previous experiment (acid hydrolysis). Figure 3 Chromatogram of SRT decomposition at 360 min in acid hydrolysis condition Figure 4 Chromatogram of SRT decomposition at 360 min in neutral hydrolysis condition In contrast to acid hydrolysis, alkaline conditions led to decomposition of SRT into three main degradation products.

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