Liquid chromatographic methods in isocratic mode for the analysis of poor quality medicines are privileged due to their simplicity and facility in methods development. They are generally fast;do not need to be re-equi...Liquid chromatographic methods in isocratic mode for the analysis of poor quality medicines are privileged due to their simplicity and facility in methods development. They are generally fast;do not need to be re-equilibrated between sample injections;have larger flexibility with acceptable changes on different column dimensions;and are applicable to LC systems equipped with simple or high developed pumps. In this study, we focused on developing simple isocratic methods using classical mobile phase composed by methanol and ammonium formate buffer for the analysis of most common antimalarial medicines marketed in malaria endemic countries and susceptible of being counterfeit/falsified, substandard and degraded. The selected medicines were quinine and related cinchona alkaloids in tablets and injectable forms;artemether/lumefantrine tablets;and artemisinin compounds (arteether, artemether, and artesunate) in injectable forms. The current methods were developed thanks to simple methodological approach consisting in sequential isocratic runs through adjustment or adaptation of existing methods to obtain optimal analytical conditions without complex design of experiments that might be long and costly. Then, the new methods presented shorter analysis time;allowed increase of sample analysis throughput;and obviously consumed little mobile phase solvents on classical analytical columns: 50 - 250 mm of length (L), 4.6 mm of internal diameter (I.D.), and 3.5 - 5.0 μm of particle size (dp).展开更多
By using NCAR/NCEP daily reanalysis data and the precipitation data in Liaoning routine automatic station during July 14-16,2008,the regional rainstorm weather process in Liaoning was done the isentropic analysis. Acc...By using NCAR/NCEP daily reanalysis data and the precipitation data in Liaoning routine automatic station during July 14-16,2008,the regional rainstorm weather process in Liaoning was done the isentropic analysis. According to the variation characteristics of isobar,isocratic specific humidity line and wind field on the isentropic surface,the rainstorm landing zone was gained and compared with the analysis results of isobaric surface. The results showed that the warm wet transportation belt on 330 K isentropic surface provided the rich water vapor condition for the rainstorm generation,and the distribution of air-pressure and wind field on the isentropic surface favored to understand the movement of airflow. Compared with the analysis of isobaric surface,the analysis of isobaric surface could better directly judge the landing zone of precipitation,and the forecast effect was better than the analysis forecast results of isobaric surface.展开更多
In this work it presents a strategy to obtain the ozone solubility in water by gradient step method. In this methodology, the ozone in mixture with oxygen is bubbling in a reactor with distilled water at 21℃ and pH 7...In this work it presents a strategy to obtain the ozone solubility in water by gradient step method. In this methodology, the ozone in mixture with oxygen is bubbling in a reactor with distilled water at 21℃ and pH 7. The ozone concentration on gas phase is continually increased after the saturation is reached. The method proposed is faster than conventional method （isocratic method）. The solubility from the gradient method is compared with that values obtained from correlations founded in the literature.展开更多
A stability-indicating reverse phase–high performance liquid chromatography（RP–HPLC） method was developed and validated for the determination of atazanavir sulfate in tablet dosage forms using C_（18） column Phen...A stability-indicating reverse phase–high performance liquid chromatography（RP–HPLC） method was developed and validated for the determination of atazanavir sulfate in tablet dosage forms using C_（18） column Phenomenix（250 mm×4.6 mm, 5 μm） with a mobile phase consisting of 900 mL of HPLC grade methanol and100 mL of water of HPLC grade. The pH was adjusted to 3.55 with acetic acid. The mobile phase was sonicated for 10 min and filtered through a 0.45 μm membrane filter at a flow rate of 0.5 mL/min. The detection was carried out at 249 nm and retention time of atazanavir sulfate was found to be 8.323 min. Linearity was observed from 10 to 90 μg/mL（coefficient of determination R^2 was 0.999） with equation, y=23.427x＋37.732.Atazanavir sulfate was subjected to stress conditions including acidic, alkaline, oxidation, photolysis and thermal degradation, and the results showed that it was more sensitive towards acidic degradation. The method was validated as per ICH guidelines.展开更多
文摘Liquid chromatographic methods in isocratic mode for the analysis of poor quality medicines are privileged due to their simplicity and facility in methods development. They are generally fast;do not need to be re-equilibrated between sample injections;have larger flexibility with acceptable changes on different column dimensions;and are applicable to LC systems equipped with simple or high developed pumps. In this study, we focused on developing simple isocratic methods using classical mobile phase composed by methanol and ammonium formate buffer for the analysis of most common antimalarial medicines marketed in malaria endemic countries and susceptible of being counterfeit/falsified, substandard and degraded. The selected medicines were quinine and related cinchona alkaloids in tablets and injectable forms;artemether/lumefantrine tablets;and artemisinin compounds (arteether, artemether, and artesunate) in injectable forms. The current methods were developed thanks to simple methodological approach consisting in sequential isocratic runs through adjustment or adaptation of existing methods to obtain optimal analytical conditions without complex design of experiments that might be long and costly. Then, the new methods presented shorter analysis time;allowed increase of sample analysis throughput;and obviously consumed little mobile phase solvents on classical analytical columns: 50 - 250 mm of length (L), 4.6 mm of internal diameter (I.D.), and 3.5 - 5.0 μm of particle size (dp).
文摘By using NCAR/NCEP daily reanalysis data and the precipitation data in Liaoning routine automatic station during July 14-16,2008,the regional rainstorm weather process in Liaoning was done the isentropic analysis. According to the variation characteristics of isobar,isocratic specific humidity line and wind field on the isentropic surface,the rainstorm landing zone was gained and compared with the analysis results of isobaric surface. The results showed that the warm wet transportation belt on 330 K isentropic surface provided the rich water vapor condition for the rainstorm generation,and the distribution of air-pressure and wind field on the isentropic surface favored to understand the movement of airflow. Compared with the analysis of isobaric surface,the analysis of isobaric surface could better directly judge the landing zone of precipitation,and the forecast effect was better than the analysis forecast results of isobaric surface.
文摘In this work it presents a strategy to obtain the ozone solubility in water by gradient step method. In this methodology, the ozone in mixture with oxygen is bubbling in a reactor with distilled water at 21℃ and pH 7. The ozone concentration on gas phase is continually increased after the saturation is reached. The method proposed is faster than conventional method （isocratic method）. The solubility from the gradient method is compared with that values obtained from correlations founded in the literature.
文摘A stability-indicating reverse phase–high performance liquid chromatography（RP–HPLC） method was developed and validated for the determination of atazanavir sulfate in tablet dosage forms using C_（18） column Phenomenix（250 mm×4.6 mm, 5 μm） with a mobile phase consisting of 900 mL of HPLC grade methanol and100 mL of water of HPLC grade. The pH was adjusted to 3.55 with acetic acid. The mobile phase was sonicated for 10 min and filtered through a 0.45 μm membrane filter at a flow rate of 0.5 mL/min. The detection was carried out at 249 nm and retention time of atazanavir sulfate was found to be 8.323 min. Linearity was observed from 10 to 90 μg/mL（coefficient of determination R^2 was 0.999） with equation, y=23.427x＋37.732.Atazanavir sulfate was subjected to stress conditions including acidic, alkaline, oxidation, photolysis and thermal degradation, and the results showed that it was more sensitive towards acidic degradation. The method was validated as per ICH guidelines.
