Effect of negatively charged dust on resistive instability corresponding to the electrostatic wave is investigated in a Hall thruster plasma when this purely azimuthal wave is tilted and strong axial component of wave vector is developed. Analytical calculations are done to obtain the relevant dispersion equation, which is solved numerically to investigate the growth rate of the instability. The magnitude of the growth rate in the plasma having dust particles is found to be much smaller than the case of pure plasma. However, the instability grows faster for the increasing dust density and the higher charge on the dust particles. The higher magnetic field is also found to support the instability.
Objective: The present study was aimed to develop a rapid, accurate, linear, sensitive and validate stability-indicating high performance liquid chromatographic [RP-HPLC] method for determination of vildagliptin and metformin in pharmaceutical dosage form.
Methods:The chromatographic separation was performed on kromasil-C18 column [4.5 x 250 mm; 5 µm] using a mobile phase consisting of 0.05 mmol potassium dihydrogen phosphate buffer: acetonitrile [80:20 v/v], [pH adjusted to 3.5 using orthophosphoric acid]. The flow rate is 0.9 ml/min and the detection was carried out at 263 nm.
Results:The chromatographic condition, the peak retention time of metformin and vildagliptin were found to be 2.215 min and 2.600 min respectively. Stress testing was performed in accordance with an international conference on harmonization [ICH] Q1A R2 guidelines. The method was validated as per ICH Q2 R1 guidelines. The calibration curve was found to be linear in the concentration range of 5-17.5 µg/ml and 50-175 µg/ml for vildagliptin and metformin. The limit of detection and quantification was found to be 0.0182 µg/ml and 0.0553 µg/ml for vildagliptin and 0.4451 µg/ml and 1.3490 µg/ml for metformin respectively.
Conclusion:A new sensitive, simple and stability indicating reverse-phase high-performance liquid chromatography [RP-HPLC] method has been developed and validated for the determination of vildagliptin and metformin. The proposed method can be used for routine determination of vildagliptin and metformin.
A new, simple, accurate, and sensitive UV -Spectrophotometric absorbance correction method has been developed for simultaneous determination of Pyridoxine Hydrochloride and Doxylamine Succinate in bulk and in combined tablet dosage form using distilled water as a solvent. The wavelengths selected for the analysis were 260 nm and 324 nm. Both Pyridoxine hydrochloride and Doxylamine Succinate were linear over the concentration range of 5 -40 µg/ mL and 10 -60 µg/ mL of Doxylamine Succinate and Pyridoxine hydrochloride, respectively. The percentage recovery was found to be in the range of 99.15 -100.71% for Pyridoxine Hydrochloride and 99.30 -101.99% for Doxylamine Succinate. The %RSD for recovery studies was found to be 0.5484 and 0.9071 for Pyridoxine hydrochloride and Doxylamine Succinate, respectively. The low %RSD of recovery studies indicated that there is no interference due to excipients used in formulation. The amount of Pyridoxine hydrochloride and Doxylamine succinate was found to be 100.92% ± 0.6961 and 101.05% ± 0.7965. Optical characteristics like slope, intercept, molar absorptivity, correlation coefficient, LOD and LOQ were calculated. The developed method was validated statistically by recovery studies as per ICH guidelines. The % RSD value was found to be less than 2. Thus the proposed method was simple, precise, rapid and accurate and can be successfully applied for routine quality control analysis of simultaneous determination of Pyridoxine Hydrochloride and Doxylamine Succinate in bulk and in combined tablet dosage form.
A simple, economic, accurate, sensitive, specific and precise stability indicating reverse phase high performance liquid chromatographic [RP-HPLC] method for the determination of Regorafenib in pure and tablet dosage from was developed and validated. The chromatographic separation was carried out using Phenomenex Luna-C18 column (4.5x250 mm; 5 µm particle size) as a stationary phase and methanol: acetonitrile: water (55:25:20 v/v/v) as a mobile phase. The flow rate of 1 mL/min was used with PDA detection at 275 nm. The retention time of Regorafenib was 2.480 min. RP-HPLC method was developed with linearity range of 40-240 µg/mL of Regorafenib. The correlation coefficient [r 2 ] was found to be 0.9999. The assay results obtained was in good agreement with the corresponding labeled amount by developed method within range of 98.83 ± 0.6937. Accuracy of the method was confirmed by recovery studies and the recoveries were found to be between 99.61 % and 100.22 %, the corresponding %RSD was found to be 0.2029. Precision, LOD, LOQ, specificity, robustness and ruggedness were performed as per ICH Q2(R1) guidelines and were within the acceptance criteria. This method can be conveniently used to detect the possible degradation product in the dosage form of Regorafenib during stability studies (acidic, alkaline, oxidative, thermal and photolytic). The method proved to be effective on the analysis of stressed marketed tablet formulation.
A simple, accurate, precise, economical and reproducible UV-Visible Spectrophotometric method has been developed for the simultaneous estimation of Lamivudine, Nevirapine and Zidovudine in bulk and in combined tablet dosage form. The stock solutions were prepared in methanol followed by the further required dilutions with distilled water. This method involves the formation and solving of simultaneous equations at 271, 282 and 267 nm, as absorbance maxima of lamivudine, nevirapine and zidovudine, respectively. Beers law obeyed the concentration range of 1.5-9, 2.5-15 and 3-18 g/mL for Lamivudine, Nevirapine and Zidovudine, respectively. The results of analysis were validated statistically and by recovery studies. The %RSD for the recovery study was less than 2. The proposed method can be effectively applied for the simultaneous estimation of these drugs in bulk and in combined tablet dosage form.
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