The reference standard, at three different concentrations

The reference standard, at three different concentrations (50, 100, and 150%), was added to a fixed amount of the preanalyzed sample and the amounts of the drug were analyzed by the proposed method. Results from the recovery studies are given in Tables Tables55 and and66. Table 5 Results of the recovery study of tolperisone hydrochloride Table 6 Results of the recovery study of etodolac Solution stability The stability of TOLP and ETD standard and sample solutions was determined by storing the solutions at an ambient temperature (20 �� 10��C). The solutions were checked in triplicate after three successive days of storage and the data were compared with the freshly prepared samples. In each case, it could be noticed that the solutions were stable for 48 hours, as during this time the results did not decrease below 98%.

This showed that TOLP and ETD were stable in standard and sample solutions for at least two days, at ambient temperature. Robustness The robustness of the method was determined by making slight changes in the chromatographic conditions like flow rate (�� 0.1), temperature (�� 5), and pH (�� 0.2) of the mobile phase. It was observed that there were no marked changes in the chromatograms, which demonstrated that the RP-HPLC method developed was robust. RESULTS AND DISCUSSION The RP-HPLC procedure was optimized with a view to develop an accurate and stable assay method with the pure drugs TOLP and ETD, in a tablet formulation. A Phenomenax C18 (150 mm �� 4.6 mm, 5 ��) column in isocratic mode was used, with a mobile phase phosphate buffer (KH2PO4, pH 5.

5) : Methanol : Acetonitrile : Tri-ethylamine (40 : 40 : 20 : 1.5); pH of the buffer adjusted with orthophosphoric acid. The flow rate was 1 mL / minute and identical components were measured, with detection at 257 nm. Linearity was assessed by plotting concentration versus area, which is shown in Table 1, and it is linear in the range of 3.0 �C 21.0 ��g / ml for TOLP and 8.0 �C 56.0 ��g / ml for ETD, with correlation coefficients of 0.9998 and 0.9995, respectively, with a good linearity response, greater than 0.999. The % recovery was found to be within limits of the acceptance criteria with a recovery range of 99.42 �C 101.15% for TOLP and 99.28 �C 100.94% for ETD. The %RSD for intraday and Interday precision was less than 2% for TOLP and Carfilzomib ETD. The detection limit of the proposed method was 0.16 ��g / ml and 0.58 ��g / ml, and the quantification limit was 0.51 ��g / ml and 1.7 ��g / ml for TOLP and ETD, respectively. A typical overlain chromatogram of the standard solution is shown in Figure 3, chromatogram of the standard solution of TOLP and ETD at the test level is shown in Figure 4, and a chromatogram of the test solution is shown in Figure 5.

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