Chè và các sản phẩm chè đã được biết đến và sử dụng từ rất lâu, thậm chí trở thành nét văn hóa truyền thống ở nhiều quốc gia trên thế giới, trong đó có Việt Nam. Chất lượng chè phụ thuộc vào hàm lượng các hoạt chất điển hình ví dụ như nhóm polyphenol và các hoạt chất của nó (EGCG, EGC, catechin,…). Do đó, việc nghiên cứu các phương pháp xác định các hoạt chất này là cần thiết nhằm đánh giá chất lượng chè và sản phẩm chè. Trong nghiên cứu này, phương pháp UV-Vis được áp dụng để xác định polyphenol tổng và phương pháp HPLC dùng để xác định hàm lượng hoạt chất chính trong nhóm polyphenol là EGCG. Giới hạn phát hiện đạt được là 0,12 mg/g và 0,064 mg/g tương ứng với polyphenol tổng và EGCG. Các phương pháp đã được áp dụng để xác định hàm lượng EGCG và polyphenol tổng trong 10 mẫu chè và sản phẩm chè. Kết quả cho thấy hàm lượng các chất này khá dao động trong các mẫu khác nhau, tuy nhiên lại có mối liên quan nhất định giữa hàm lượng EGCG và polyphenol tổng trong từng mẫu chè.

This article introduces capillary electrophoresis using capacitively coupled contactless conduction detector (CE-C4D) and several applications that were developed for food analysis in Vietnam. The target analyte groups include: oxalate, sweeteners (acesulfam potassium, aspartame, cyclamate, saccharine) and food preservation (citric, benzoic and sorbic acids). This study aims to develop simple, easy to operate analytical procedures that are suitable for quick analysis or screening in food analysis in field or at local laboratories. The obtained results were compared with those measured by conventional standards method (HPLC) and proved the high reliability of CE-C4D method.

Amoxicillin (AMX) is a highly antibiotic resistance so that many studies focus on the removal of AMX in water environment. The present study investigated adsorptive removal of beta-lactam antibiotic AMX using a cationic surfactant, cetyltrimethylamonium bromide (CTAB) modified nanosilica (CMNS). The CTAB adsorption on nanosilica was independent of ionic strength, indicating that both electrostatic and hydrophobic interaction induced adsorption. Effective conditions for AMX removal using CMNS were systematically studied. The AMX removal using 10 mg/ mL CMNS reached 99 % at pH 9. Adsorption isotherms of AMX on CMNS at two salt concentrations were in good agreement with Langmuir model than Freundlich model. Adsorption isotherms at different ionic strengths and the surface modification by Fourier transform infrared (FT-IR) spectroscopy demonstrate that AMX adsorption on CMNS was mainly controlled by electrostatic interaction.

The present study investigated adsorption of 2,4-dichorophenoxy acetic acid(2,4-D) on titania (TiO2) nanoparticles with surface modification by cationic surfactant, cetyltrimethylammonium bromide (CTAB). Titania nanoparticles which were successfully synthesized by sol-gel method, were characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). Surface modification of TiO2 with CTAB enhanced the removal of 2,4-D significantly. Some effective conditions affect to the removal of 2,4-D using CTAB modified TiO2 such as pH and adsorbent dosage were systematically studied and found to be 5 and 10 mg/mL, respectively. Adsorption mechanisms of 2,4-D onto CTAB modified TiO2 was suggested based on the change in surface charge after adsorption.

The present study investigated the photodegradation of 2,4-Dichlorophenoxyacetic acid (2,4-D) in a water environment using synthesized titania nanoparticles (TiO2-NPs). The TiO2-NPs fabricated by sol-gel method were distinguished by X-ray diffraction (XRD) and Transmission electron microscopy (TEM), Infrared spectroscopy (IR), and zeta potential measurements. The results indicated that TiO2 - NPs were nanospheres of appropriately 30nm with a major anatase phase. Synthesized TiO2-NPs have the point of zero charge (PZC) of around 6.0. The efficient conditions for photocatalysis degradation of 2,4-D under sunlight were considered and found to be 120 min, pH 11, and 1 mM KCl. Under ideal conditions, the photodegradation efficiency of 2,4-D reached greater than 72 %. Our results suggest that TiO2-NPs would be promisingly applied for eliminating 2,4-D from an aqueous solution.