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Capillary zone electrophoresis was successfully applied to the enantiomeric purity determination of valsartan using acetyl-β-cyclodextrin (A-β-CD) as a chiral selector. Separations were carried out in a 50 µm, 64/56 cm fused-silica capillary. The optimized conditions included 25 mM phosphate buffer, pH 8.0, containing 10 mM A-β-CD as background electrolyte, an applied voltage of +30 kV and a temperature of 30 °C. Ibuprofen was used as an internal standard. The assay was validated for the R-enantiomer of valsartan in the range of 0.05-3.0%. The limit of detection was 0.01%, the limit of quantitation was 0.05%, relative to a concentration of valsartan of 1 mg/ml. Intra-day precision varied between 2.57 and 5.60%. Relative standard deviations of inter-day precision ranged between 4.46 and 6.76% for peak area ratio. The percentage recovery of the R-enantiomer of valsartan ranged between 97.0 and 99.6% in valsartan product. The assay was applied to the determination of the chiral purity of valsartan tablets and R-enantiomer of valsartan was found as an impurity.

Capillary electrophoresis (CE) and proton nuclear magnetic resonance spectroscopy ((1)H-NMR) have been used to discriminate the enantiomers of sibutramine using cyclodextrin derivatives. Possible correlation between CE and (1)H-NMR was examined. Good correlation between the (1)H-NMR shift non-equivalence data for sibutramine and the degree of enantioseparation in CE was observed. In CE study, a method of enantiomeric separation and quantitation of sibutramine was developed using enantiomeric standards. The method was based on the use of 50 mM of phosphate buffer of pH 3.0 with 10 mM of methyl-beta-cyclodextrin (M-β-CD). 0.05% of LOD, 0.2% of LOQ for S-sibutramine enantiomer was achieved, and the method was validated and applied to the quantitative determination of sibutramine enantiomers in commercial drugs. On a 600 MHz (1)H-NMR analysis, enantiomer signal separation of sibutramine was obtained by fast diastereomeric interaction with a chiral selector M-β-CD. For chiral separation and quantification, N-methyl proton peaks (at 2.18 ppm) were selected because of its being singlet and simple for understanding of diastereomeric interaction. Effects of temperature and concentration of chiral selector on enantiomer signal separation were investigated. The optimum condition was 0.5 mg/mL of sibutramine and 10 mg/mL of M-β-CD at 10°C. Distinguishment of 0.5% of S-sibutramine in R-sibutramine was found to be possible by (1)H-NMR with M-β-CD as chiral selector. Host-guest interaction between sibutramine and M-β-CD was confirmed by (1)H-NMR studies and CE studies. A Structure of the inclusion complex was proposed considering (1)H-NMR and 2D ROESY studies.

In Vietnam, Physalis angulata L. has been widely used as a traditional medicine to treat fever, anti-inflammatory, and expectorant. Currently, there have been studies on the content of chemical composition especially physalin with anti-diabetic, anti-inflammatory, antibacterial, prevent cancer. This study developed a reliable and sensitive method to determine and validate simultaneous Physalin B and Physalin D in Physalis angulata L.. The QuEChERS method was used for sample preparation from leaf matrices and quantified by using High-performance liquid chromatography coupled with a diode-array detector. The method of research was validated under AOAC and ICH guidance. Chromatography conditions include Agilent C18 column (250mm × 4,6mm; 5µm) with a gradient mode using acetonitrile – methanol-water as mobile phase. The recovery of the method ranged from 94.21 – 105.93% and RSD was from 1.20 – 2.31%, the LOD, and LOQ were 0.4 mg/kg – 2.4 mg/kg, respectively. The results of the study showed that the proposed the new QuEChERS method for quantification of Physalin B and D in Physalis angulata L. in Vietnam.

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Lotus and Green Tea leaves are two frequently used medicinal plants in Vietnam, utilized as food, drink, or in traditional treatments to help with weight loss and cholesterol reduction. The study’s major goal is to determine the parameters of the process preparation in order to generate instant tea powder that satisfies quality criteria for customer demand. Twenty experiments are conducted using the D-optimal model to evaluate the cause-effect relationship and optimize the production process of instant tea powder. Four independent variables are selected for the survey namely alcohol concentration (40%; 50%; 60%), carrier mass (10 g; 20 g; 30 g), inlet air temperature (160 °C; 170 °C) and flow rate (4 rpm/min; 5 rpm/min). The instant tea powder is effectively created and met quality parameters, with a drying performance, moisture content, total phenol and flavonoid content of 29.15%, 4.83%, 45.29 mg GA/g, and 70.68 mg QE/g, respectively. In conclusion, the optimal parameters of the preparation process were identified, which included an alcohol content of 60%, a carrier mass of 10 g, an inlet air temperature of 165 °C, and a flow rate of 4 rpm/min.

Research has indicated that self-study is a constructivist learning approach that promotes student engagement within tertiary education. However, teaching at higher education institutions is largely based on traditional lecture mode and thus, students are likely become passive in their learning process. Moreover, little research has been conducted to look into this constructivist approach perceived by students in English as a foreign language (EFL) classes. These paper therefore examines the difficulties of self-study in reading comprehension classes in high quality program at a university in the Mekong Delta, Vietnam. Data collected in this study included questionnaire and interview. The participants in this study were 75 juniors in English languages and culture studies. The findings from this study indicate that student-related factors such as time, learning environment, and subject-specific vocabulary could hinder them from reading learning. Pedagogical implications and recommendations for students and teachers are provided.

Linagliptin is a highly specific, long-acting inhibitor that is used as an orally administrable agent for type-2 diabetes treatment. Because only the R-enantiomer is of clinical use, we developed a capillary electrophoresis method for the determination of the enantiomeric impurity of this compound. Carboxymethyl-β-cyclodextrin was selected as the chiral selector for the separation of linagliptin enantiomers. Design of experiments and desirability functions were used for the analytical optimization, which was focused on understanding and improving the electrophoretic process. The effects of significant parameters (background electrolyte concentration and pH, cyclodextrin concentration, temperature, and voltage) were thoroughly investigated. The complete separation of linagliptin and its enantiomeric impurity with baseline resolution was achieved within 10 min on an uncoated fused-silica capillary (50 μm inner diameter, 365 μm outer diameter, 64.5/56 cm in total/ effective length) maintained at 25 • C, under an applied voltage of 28.0 kV. The background electrolyte contained 70 mM sodium acetate and 4.7 mM carboxymethyl-β-cyclodextrin, and the pH was adjusted to 6.10. The method was validated, and a limit of quantitation of 0.05% for the impurity was estimated.