主成分回归-紫外光度法同时测定食用香料麦芽酚和乙基麦芽酚

报道了一种快速、简便的同时测定食用香料麦芽酚、乙基麦芽酚光度法,方法基于在pH2.87的B R缓冲溶液中对麦芽酚和乙基麦芽酚两组分混合溶液进行光度测定,所得的重叠波谱数据用主成分回归法(PCR)、经典最小二乘法(CLS)和偏最小二乘法(PLS)等化学计量学方法进行处理,结果表明主成分回归法(PCR)的预报误差最小。对样品进行测定,获得了较好的定量分析结果。麦芽酚和乙基麦芽酚的线性范围均为1.0～20.0mg·L-1;检出限分别为0.4347和0 5589mg·L-1。     

Translucent nanolatexes through emulsion polymerisation of ethyl acrylate

Turbid emulsion systems of ethylacrylate/sodium dodecyl sulphate/water with monomer to surfactant (M/S) ratios 10 and 40 were transformed into stable transparent/translucent nanolatexes through emulsion polymerisation using potassium persulphate as an initiator. The latex particle size was observed to be similar to that obtained by true microemulsion polymerisation where M/S ratio is one. The kinetic plots exhibited two intervals upto M/S ratios 10. AIBN initiated systems showed separation of two phases for the M/S ratio ?10. M/S ratios were varied from 1 to 54 for the comparative study of polymerisation in emulsion and microemulsion media. Gel effect dominance was observed around 40-60% conversion for the microemulsion polymerisation of ethylacrylate. Only one chain per particle was observed for microemulsion system with M/S ratio 1 and three to four chains per particle were observed for the systems with M/S ratios 10 and 40. Unlike M/S=1 system, higher dependency of polymerisation rate on initiator concentration was observed for the systems with M/S=10 and 40. A possible mechanism for such a transformation has been proposed.     

Apparent molar heat capacities of aqueous solutions of acetic,propanoic and succinic acids,sodium acetate and sodium propanoate from 300 to 525 K and a pressure of 28 MPa

The apparent molar heat capacities of dilute aqueous solutions of acetic, propanoic and succinic acid and sodium salts of the two monofunctional acids were measured at 300 Kp,2 ^o . After subtracting the heat capacity of a point mass, the remaining heat capacity was successfully decomposed into functional group contributions at all temperatures. Together with the results of our previous paper on alcohols and diols the heat capacity contributions of the CH₂, CH₃, OH, COOH, (COOH)₂, and COONa groups are now available and these allow reasonably accurate predictions of the heat capacities of all compounds composed of these groups in this temperature range.     

Regioselective cyclization of unsymmetrical dicyanoanilines to novel 2,3-bifunctionalised indole regioisomers and their use in the synthesis of 4,5-dihydro[1,3]oxazino[5,4-b]indole-6-carbonitriles

Synthesis of novel-2,3-bifunctionalised indole regioisomers (2/3 and 6/7) from unsymmetrical dicyanoanilines 1 by regioselective cyclization in two independent ways. Regioisomers 6 are further utilized in synthesis of novel 4,5-dihydro[1,3]oxazino[5,4-b] indole-6-carbonitriles 9.     

(Liquid + liquid) equilibria of (water + propionic acid + methyl isoamyl ketone or diisobutyl ketone or ethyl isoamyl keton) at T = 298.2 K

(Liquid + liquid) equilibrium (LLE) data for (water + propionic acid + solvent) were measured at T = 298.2 K and atmospheric pressure. The solvents were methyl isoamyl ketone (5-methyl-2-hexanone), ethyl isoamyl ketone (5-methyl-3-heptanone) and diisobutyl ketone. The tie-line data were correlated by means of the NRTL and UNIQUAC equation, and compared with results predicted by the UNIFAC method. A comparison of the extracting capabilities of the solvents was made with respect to distribution coefficients, separation factors, and solvent free selectivity bases.     

Effect of take-up speed on physical properties and permeation performance of cellulose acetate hollow fibers

Cellulose acetate (CA) ultrafiltration hollow fibers were spun via the dry-jet wet spinning technique. The effect of the take-up speed on the mechanical properties, morphology, thermal properties, pure water permeation, retention, and surface characterization of hollow fiber membranes were investigated. Both the inner and outer diameters of the hollow fiber decreased with the increase of take-up speed. Macrovoids were observed on the inner surface of the drawn hollow fibers. The d-space decreased with the increase of the take-up speed. The ultimate tensile stress (UTS) increased and the breaking elongation decreased with the increase of take-up speed. The permeation performance was measured. The hydraulic permeability increased and the retention decreased slightly with the increase of the take-up speed. The surface roughness increased with the increase of the take-up speed. The thermal analysis results showed that the endothermic peak shifts to the higher temperature region and coefficient of thermal expansion (CTE) decrease for a higher take-up speed.     

Flow through Porous Media XVI: Electrokinetic Transport Coefficients of Aqueous Solutions of Mercuric Chloride and Glycine through a Sintered Disc Impregnated with a Cellulose Acetate Membrane under a Magnetic Field

The effect of the magnetic field on the electrokinetic transport coefficients (permeability coefficient and electro-osmotic permeability coefficient) of water and aqueous solutions of mercuric chloride and glycine through a sintered disc impregnated with cellulose acetate at different potentials, concentrations, and magnetic fields varying up to 21 kg/cm² are reported at 308.15 K. The phenomenological coefficients characterizing the electro-osmotic flow and the membrane characteristics are also estimated for the various solutions with the object of determining the efficiencies of electrokinetic energy conversion and ζ potential. The effect of magnetic field has been attributed to the molecular orientation of dipoles in solutions and to the change in the structure of the membrane.     

Synthesis and properties of amphiphilic vinyl acetate triblock copolymers prepared by copper mediated living radical polymerisation

Polymerisation of vinyl acetate by conventional free radical polymerisation using a diazo initiator followed by copper mediated living radical polymerisation with a range of monomers was studied. This method led to the synthesis of triblock copolymers. We have thus successfully prepared several new ABA triblock copolymers where B is poly(vinyl acetate) and A is (dimethylamino)ethyl methacrylate (DMAEMA), (polyethylene glycol) methyl ether methacrylate (MeO(PEG)MA) or solketal methacrylate (SMA). The sequential conventional/living radical polymerisation approach provided an efficient route to synthesis of new block copolymers. The properties of these amphiphilic polymers have been subsequently investigated by ¹H NMR, fluorescence spectroscopy, tensiometry and dynamic light scattering to investigate their behaviour as potential surfactants.     

Green synthesis of banana flavor using different catalysts: a comparative study of different methods

ABSTRACT

Esterification of isoamyl alcohol with acetic acid was studied using different ion-exchange resins, namely Amberlyst 15 dry, Amberlyst 16 wet, Amberlite 120-IR. Esterification was carried out using different esterification methods that are quite new (ohmic, ultrasonic probe, and ultrasonic bath) and the results were compared with microwave-assisted esterification (MAE). The highest isoamyl acetate yield (99%) was obtained by MAE, using a mixture of acetic acid and isoamyl alcohol (mole ratio of 1:2) after 2?h of reaction time. In this process, 2% Amberlyst 15 dry was used. MAE had the least specific energy consumption (0.42?kWh/g isoamyl acetate) and specific CO₂ emission (34?g/g isoamyl acetate). According to the images obtained by scanning electron microscopy, lower amounts of Amberlyst 15 dry beads were destroyed by MAE method compared to other esterification methods. In conclusion, MAE proved to be an economic and environmentally-friendly method for esterification of different flavoring compounds.     

Application of correlation-gas chromatography to evaluate the vaporization enthalpy of a component in an equilibrium mixture

The vaporization enthalpies and vapor pressures of acetoin, ethyl 3-hydroxybutyrate and ethyl 3-hydroxyhexanoate, found in a variety of foods and flavors, are evaluated at T = 298.15 K using correlation-gas chromatography; values of (48.7 ± 0.4), (55.9 ± 0.6) and (61.9 ± 0.6) kJ mol⁻¹, respectively, were obtained. These values are in good agreement with estimated values. Vapor pressures of the standards as a function of temperature were also used to calculate vapor pressures of the target compounds and all resulting data were fit to second order polynomials. These polynomials were then used to predict boiling temperatures of both standards and target substances. Agreement with experimental boiling temperatures was generally within 10 K suggesting that vapor pressures are accurate to within a factor of two. Acetoin exists as an equilibrium mixture of monomer and dimer. This report provides an example of the utility of using correlation-gas chromatography to obtain thermochemical data on an impure material.