Papers by Keyword: Microemulsion

Abstract: This study aimed to develop oral microemulsions (MEs) containing M. alba extract. The stability study of the extract incorporated in the ME was also included. First, pseudo-ternary phase diagrams were constructed using caprylic/capric triglyceride (oil), PEG-8 caprylic/capric glycerides (S), polyglyceryl-3 diisostearate (CoS). Propylene glycol (PG) was used as a cosolvent. Then, the formulations were chosen to incorporate MSE and subjected to stability testing at 4^o C, room temperature (RT) and 45^o C at 75% RH for 8 weeks. Physical stability of the formulations was assessed by visual observation on the precipitation, phase separation and cloud point. Chemical stability was determined by quantitative analysis of oxyresveratrol using high performance liquid chromatography (HPLC). The results showed that with increasing the ratio of S/CoS, the area of ME existing region in phase diagrams increased. The addition of PG into aqueous phase at ratio 1:1 slightly affected the formation of MEs. Physical stability was not affected by temperature but was influenced by the components of the formulations. However, degradation of the extract was affected by both temperature and components of the formulations. The extract was stable at 4^o C and RT. However, at 45^o C, it degraded about 16-57%, depending on the components of the formulations. The best ME formulation consisted of 10% caprylic/capric triglyceride, 80% PEG-8 caprylic/capric glycerides and polyglyceryl-3 diisostearate (4:1), and 10% water and PG (1:1).

Abstract: A fast and effective method was developed for determination of Mn in leisure foods by incomplete digestion-microemulsion sampling-high resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS). Microemulsions were prepared with digestive liquor and n-butyl alcohol as an auxiliary emulsifier after incomplete digestion treatment. The factors influencing determination were investigated by single factor experimental design. The optimal determination conditions were found as follows: the tartaric acid (1 mg/mL) was added as a chemical modifier with the volume of 4 μL; pyrolysis temperature 1100°C; atomization temperature 2000°C. The results showed that the correlation coefficient was better than 0.996, the characteristic concentration was 0.09 μg/L, the precision (RSD) for 6 replicate measurements of Mn was 2.8% and the average of recoveries was 97.3%. F-test and t-test (95% confidence level) in between the proposed method and the microwave digestion-HR-CS GFAAS method had no significant difference. Therefore, the proposed method was accurate and stable with a high practical value. It provided scientific basis for determination of metal elements in food.

Abstract: The extraction process of cobalt using microemulsion system saponified with P₅₀₇ as extracting agent was studied. The influences of initial concentration, the concentration of P₅₀₇, initial pH, the extracting time and the volume ratio of organic phase to water phase on extraction coefficient were also studied. Experimental results show that the saponification microemulsion system using P₅₀₇ as extractant is thermodynamic stable, and it can separate cobalt better. The optimum conditions were achieved as: the initial concentration is 0.04 mol/L, pH is 2; The concentration of P₅₀₇ is 6%, extraction time is 6 min; The volume ratio of organic phase to water phase is 1.5:1.

Abstract: The aim of this work was to evaluate the microemulsification after incomplete digestion as sample preparation procedure for determination of Ca in leisure foods by high resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Microemulsions were prepared with digestive liquor and n-butyl alcohol as an auxiliary emulsifier after incomplete digestion treatment. The appropriate fuel flow, 70 L/h, and the optimum burner height, 5 mm, were obtained by single factor experimental design. The results showed that the correlation coefficient was better than 0.999, the characteristic concentration was 0.086 mg/L, the precision (RSD) for 6 replicate measurements of Ca was 1.7% and the average of recoveries was 102.1%. F-test and t-test (95% confidence level) in between the proposed method and the comparative method, using microwave digestion-HR-CS FAAS, had no significant difference. Therefore, the proposed method was accurate and stable with a high practical value. It provided scientific basis for determination of metal elements in food.

Abstract: Size controllable Barium titanate nanoparticles were synthesized in microemulsion consisting of water, OP-10, hexanol and cyclohexane under atmospheric pressure and low temperature, with Ba (OH)₂·8H₂O and tetrabutyl titanate used as starting reactants. Products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX). The results show that 65°C is the proper temperature for the synthesis. The particle size can be controlled by varying the reactants’ concentration, ω value (molar ratios of water to surfactant) and aging time.

Abstract: The design, synthesis and characterization of magnetic-luminescent nanoparticles is now more and more studied since the last decade. However, optimizing the design of such materials requires a deep understanding of their physico-chemical properties. In this paper are reported extended investigations on luminescent and magnetic @SiO₂ Nps prepared by a water-in-oil microemulsion technique. The Cs₂[Mo₆Br₁₄] cluster compound is used as red-NIR phosphor and is prepared by solid state chemistry. We bring here new insights into the structure of such Nps and its interplay with their optical or magnetic properties.

Abstract: A series of Ce_xZr_(1-x)O₂ mixed oxides with different ratio (0 x 1) have been synthesized using microemulsion method. The structure and morphology of the mixed oxides have been investigated via X-ray Diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM). The results showed that the synthesized mixed oxides were of nanoscale size and the cubic phase was obtained with the application of a ratio of x > 0.5. Additionally, it was found that the tetragonal phase existed with lower ceria content. The average crystallite size of the Ce_xZr_(1-x)O₂ series were found to be in the 5 - 10 nm range. Moreover, the roughness of these mixed oxides had also decreased with increasing ceria content.

Abstract: Oxidative damage is a public health issue in the modern world and promoting dietary anti-oxidants, such as curcumin, is a promising strategy. However, curcumin is unstable and poorly water-soluble and of poor bioavailability. This study constructed new curcumin-loaded O/W microemulsions using a pharmaceutically accepted Brij97 nonionic surfactant and evaluated several properties of curcumin encapsulated in the microemulsions. The pseudo-ternary phase diagram of Brij97/isopropyl alcohol/ethyl acetate/water system was determined and three microregions of the microemulsionsW/O, bicontinuous, and O/Ware identified by conductivity measurements, according to percolation theory. The properties investigation of a series of curcumin-loaded O/W microemulsions indicates: (1) The curcumin in such a situation performs sustained release following the first-order kinetics; (2) Better stability of curcumin to the sun light is observed over a time scale; (3) The curcumin presents relatively high anti-oxidant activity, with the IC₅₀ in between 31.5 and 17.2 μg/ml on scavenging the superoxide radicals. In addition, the structure difference in the homologues acetate seems having no effect on the stability and release behavior of curcumin, while the investigated properties clearly depend on the ME/acetate ratio in the microemulsions. This study might be a potential help to the protection and the delivery of curcumin.

Abstract: Effects of extraction-stripping loops of organic phase on organic chemical entrainment in the aqueous raffinate in copper solvent extraction were studied in this paper. Results demonstrated that the total amount of organic chemicals lost in the aqueous raffinate decreased with the increase of times of extraction-stripping loops but reached largest at third loop. Entrainment was the dominate way of organic chemicals losing in the aqueous raffinate at early stage of the loops. The formation of entrainment and its stabilization mechanism was also studied. The average size of entrained droplet trended to increase with extraction-stripping loops increasing. Meanwhile, the absolute value of zeta potential trended to decrease. The surface tension of the aqueous raffinate increased after reaching the minimum value 41.3 mN/m at the 3rd loop. It showed that the formation of entrained droplets and its stability were mainly affected by the surface tension of aqueous raffinate.

Abstract: With n-butanol/CTAB/cyclohexane as micro emulsion system, sodium tungstate and hydrochloric acid as raw material, alkali metals (Na+, K+) nitrate as dopant, pure WO3、Na+-WO3, K+-WO3 and Na+/K+-WO3 powders were prepared by ultrasonic micro-emulsion method; And performances of samples were analyzed by visible spectrophotometer. Photocatalytic activity study show that alkali metal sodium ion and potassium ion doped, photocatalytic activities of WO3 are improved markedly; When doping amount is 1.0%, catalyst amount is 2g/L, methyl orange concentration is 20mg/L, degradation time is 80 min, Na+-WO3 powder has the best photocatalytic degradation performance at 460nm, and the degradation rate is as high as 65%.