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Electrophoretic mobility and primary electroviscous effect of dilute "hard" prolate ellipsoids

The effect of DL-homocysteic acid (DL-2-amino-4-sulfonobutyric acid) on W/O microemulsion of potassium naphthenate (80%) and naphthenic acid (20%) in mixed solvent (1-octanol and n-heptane) has been found in four phases: (1) Interaction between the amino acid molecules and the polar head groups of the surfactant through hydrogen bonding enhances solubilization in the aqueous cores. (2) The interaction results in the growth of the microemulsion droplets and the homogenization of the particle size distribution. (3) The microstructure of the solubilized water remains unchanged, except that the polarity of the interface is affected. (4) The transition point is reduced to lower water content. A possible mechanism is proposed.     

A critical assessment of capillary condensation and evaporation equations: a computer simulation study

Nonaqueous reverse micelles of brij surfactants are prepared in benzene and ethylammonium nitrate (EAN). The effect of polar head group bulk on reverse micellar size was studied with brij-52, brij-56 and brij-58 whereas the effect of polarity of hydrocarbon chain was investigated taking brij-52 and brij-93 with varying W(s) (W(s)=[EAN]/[surfactant]). Dynamic light scattering (DLS) has been employed to reveal the size and shape of the reverse micelles. Micropolarities of these reverse micelles were investigated by visible spectroscopy using methylene blue (MB) and methyl orange (MO) as molecular optical probes. It has been revealed from the experimental results that with increase in polar head group size reverse micellar size increases. Moreover, it is also observed that with increasing polarity of the hydrocarbon chain the average size of the reverse micelles decreases. It can be concluded that polar head group size and polarity of hydrocarbon chain play important roles in determining reverse micellar size of the brij surfactants apart from the W(s) ratio, nature of the solvent medium, and concentration of the surfactants.     

近红外(NIRS)技术分析小样品油菜籽芥酸和含油量的应用研究

以完整油菜籽为样品,采用旋转杯和安培瓶两种样品杯、每种样品分为4×2种不同样品量并通过不同光谱预处理来优化油菜籽芥酸和含油量的近红外分析模型。结果表明:油菜籽各小样品含油量模型的决定系数(R2)从93.93%到96.93%不等,均方差(RMSECV)从0.56到0.79不等;油菜籽各小样品芥酸模型的决定系数(R2)从96.91%到98.42%不等,均方差(RMSECV)从1.73到2.43不等。随着样品量的逐渐增加,油菜籽芥酸和含油量不同样品杯模型各参数逐渐有所优化;同一样品厚度时,油菜小样品芥酸和含油量的旋转样品杯模型各参数均略优于安培瓶样品模型;不同样品量的NIRS模型,W3和W4差异不大,依次优于W2和W1。最小样品量AW1为0.3g。优化油菜小样品模型时,应该选择全部的预处理方法,根据优化结果选择最佳模型。外部检验结果表明:不同重量小样品(W1/0.3g、W2/1.0g、W3/2.0g和W4/4.0g)模型之间及其与标准化学值之间在0.01水平上差异不显著,说明W1和W2小样品模型同样可应用于油菜品质育种材料的分析选择。     

Determination of boron in blood,urine and bone by electrothermal atomic absorption spectrometry using zirconium and citric acid as modifiers

A comparative study of various potential chemical modifiers (Au, Ba, Be, Ca, Cr, Ir, La, Lu, Mg, Ni, Pd, Pt, Rh, Ru, Sr, V, W, and Zr), and different ‘coating’ treatments (Zr, W, and W+Rh) of the pyrolytic graphite platform of a longitudinally heated graphite tube atomizer for thermal stabilization and determination of boron was undertaken. The use of Au, Ba, Be, Cr, Ir, Pt, Rh, Ru, Sr and V as modifiers, and of W+Rh coating produced erratic, and noisy signals, while the addition of La, Ni and Pd as modifiers, and the W coating had positive effects, but with too high background absorption signals, rendering their use unsuitable for boron determination even in aqueous solutions. The atomic absorption signal for boron was increased and stabilized when the platform was coated with Zr, and by the addition of Ca, Mg, Lu, W or Zr as modifiers. Only the addition of 10 μg of Zr as a modifier onto Zr-treated platforms allowed the use of a higher pyrolysis temperature without analyte losses. The memory effect was minimized by incorporating a cleaning step with 10 μl of 50 g l⁻¹ NH₄F HF after every three boron measurements. The addition of 10 μl of 15 g l⁻¹ citric acid together with Zr onto Zr-treated platforms significantly improved the characteristic mass to m₀=282 pg, which is adequate for biological samples such as urine and bone, although the sensitivity was still inadequate for the determination of boron in blood of subjects without supplementary diet. Under optimized conditions, the detection limit (3σ) was 60 μg l⁻¹. The amount of boron found in whole blood, urine and femur head samples from patients with osteoporosis was in agreement with values previously reported in the literature.     

载有胰岛素的可生物降解微球的制备与表征

用乙交酯与丙交酯的无规共聚物(PLGA)和聚乙二醇单甲醚-聚丙交酯两嵌段共聚物(MPEG-PLA)的合金作为囊材料,包裹胰岛素固体粉末,包裹率分析表明,固体粉末法对胰岛素的包裹率高于双乳液法.所得微球球形很好,尺寸在1～3μm范围,剖面具有核壳结构,胰岛素以晶粒的形式包裹在高分子壳层中.两种高分子在凝聚过程中发生相分离,在壳层中有分层现象.测定微球的体外释放行为,由聚合物合金制备的微球的暴释现象得到了缓解,两种聚合物的配比不同,其暴释缓解的程度也不一样.     

极谱法测定化探样品中的钨、钼

化探样品经氢氧化钾熔融,用水提取其中的钨、钼,采用二苯乙醇酸代替苯羟乙酸,在硫酸-二苯乙醇酸-二苯胍-氯酸钾体系中,利用极谱催化波测定钨、钼,方法的灵敏度大大提高,钨、钼的峰电位分别为-0.76、-0.26 V(对饱和甘汞电极),钨、钼含量为1.0～100.0 ng/mL时,极谱峰高与浓度呈线性关系.方法经国家一级标准样品检验,测定结果与推荐值吻合,钨、钼测定结果的RSD分别为3.5%～4.1%、3.4%～3.9%(n=11).     

Zymomonas mobilis as catalyst for the biotechnological production of sorbitol and gluconic acid

The conversion of glucose and fructose into gluconic acid (GA) and sorbitol (SOR) was conducted in a batch reactor with free (CTAB-treated or not) or immobilized cells of Zymomonas mobilis. High yields (more than 90%) of gluconic acid and sorbitol were attained at initial substrate concentration of 600 g/L (glucose plus fructose at 1:1 ratio), using cells with glucose-fructose-oxidoreductase activity of 75 U/L. The concentration of the products varied hyperbolically with time according to the equations (GA)=t(GA)(max)/(W(GA) +t), (SOR)=t (SOR)(max)/(W(Sor)+t), v(GA)=[W(GA) (GA)(max)]/(W(GA)+t)(2) and V(SOR)=[W(SOR) (SOR)(max)]/(W(SOR)+t)(2). Taking the test carried out with free CTAB-treated cells as an example, the constant parameters were (GA)(max)= 541 g/L, (SOR)(max)=552 g/L, W(GA)=4.8h, W(SOR)=4.9h, upsilon(GA)=112.7 g/L. and upsilon(SOR)=112.7 g/L.     

Fluorescence anisotropy of ionic probes in AOT reverse micelles: influence of water droplet size and electrostatic interactions on probe dynamics

Fluorescence anisotropies of two structurally similar ionic probes, rhodamine 110 and fluorescein, were measured in di(2-ethylhexyl) sodium sulfosuccinate (AOT) reverse micelles as a function of the mole ratio of water to surfactant W. This study was undertaken to explore the influence of water droplet size and electrostatic interactions on the rotational diffusion of the probe molecules. It was noticed that at W = 1 and 2, the anisotropy decays of both the probes display single-exponential behavior and for a particular value of W, the time constants sensed by rhodamine 110 and fluorescein are identical. Moreover, an increase in the reorientation time was observed from W = 1 to 2. These observations indicate that, at W = 1 and 2, it is the overall rotation of micelle which is responsible for the decay of the anisotropy and also rule out the possibility of internal rotation of the probes within the reverse micelles. However, from W = 4 to 20, the anisotropy decays of the probes could only be described by a biexponential function with two time constants. The rotational diffusion of rhodamine 110 and fluorescein in the above-mentioned range of W was rationalized using the two-step model. The average reorientation time decreases with an increase in W for both the probes, and this decrease is pronounced in the case of fluorescein compared to that in rhodamine 110. The decrease in the average reorientation time with W is due to the change in the micellar packing within the core. The significant reduction in the average reorientation time of fluorescein is a consequence of repulsive electrostatic interactions between the negatively charged probe and the anionic head groups of the surfactant AOT.     

Synthesis and lyotropic liquid crystalline behaviour of a taper-shaped phosphonic acid amphiphile

A taper-shaped phosphonic acid, 3,4,5-tris(dodecyloxy)phenylmethylphosphonic acid ( 1 ), was synthesized; its lyotropic liquid crystalline (LLC) behaviour and its ability simultaneously to order and acid-dope polyaniline were examined. It was found that the ability of 1 to form LLC phases in the presence of several hydrophilic solvents is restricted by strong intermolecular interactions between the phosphonic acid head groups (presumably H-bonding). The amphiphile exhibits poor miscibility with pure water and even with strong H-bonding organic solvents such as DMF. However, it forms a lamellar mesophase in the presence of aqueous acid. Upon deprotonation of the phosphonic acid head group with NaOH, the resulting disodium salt of the amphiphile is able to form a well defined lamellar phase with pure water. The propensity of 1 to form lamellar phases is somewhat unusual since its tapered molecular shape should direct it to form an inverted hexagonal LLC phase. These results suggest that intermolecular head group interactions are more important in determining the overall LLC behaviour of this phosphonic acid amphiphile than are the hydrophobic character and shape of the organic tail system. Compound 1 was also found to be sufficiently acidic to act as an acid dopant for the conjugated polymer polyaniline in the emeraldine base form. LLC acid 1 induces the resulting polymeric salt to form an electrically conductive LLC complex with an extended lamellar microstructure. The bulk conductivity of the resulting nanostructured polyaniline salt was found to be only in the semiconducting regime (10 -5 Scm -1 ), due to an unfavourable polyaniline chain conformation in the LLC complex.     

Preparation of a stable double emulsion (W1/O/W2): role of the interfacial films on the stability of the system

This paper presents new protocols enabling preparation of W1/O/W2 double emulsions: one, using soybean oil as the O phase, that yields edible emulsions with industrial applications, and a second that yields emulsions with a previously unattainable concentration 15% (w/w) of surfactants in the external phase (the 15% target was chosen to meet the typical industry standard). Preparation of a stable W1/O emulsion was found to be critical for the stability of the system as a whole. Of the various low HLB primary surfactants tested, only cethyl dimethicone copolyol (Abil EM90), A-B-A block copolymer (Arlacel P135), and polyglycerol ester of ricinoleic acid (Grinstead PGR-90) yielded a stable W/O emulsion. Investigation of the surface properties of those surfactants using the monolayer technique found two significant similarities: (1) stable, compressible, and reversibly expandable monolayers; and (2) high elasticity and surface potential. The high degree of elasticity of the interfacial film between W1 and O makes it highly resilient under stress; its failure to break contributes to the stability of the emulsion. The high surface potential values observed suggest that the surfactant molecules lie flat at the O/W interfaces. In particular, in the case of PGR-90, the hydroxyl (-OH) groups on the fatty acid chains serve as anchors at the O/W interfaces and are responsible for the high surface potential. The long-term stability of the double emulsion requires a balance between the Laplace and osmotic pressures (between W1 droplets in O and between W1 droplets and the external aqueous phase W2). The presence of a thickener in the outer phase is necessary in order to reach a viscosity ratio (preferably approximately 1) between the W1/O and W2 phases, allowing dispersion of the viscous primary emulsion into the W2 aqueous phase. The thickener, which also serves as a dispersant and consequently prevents phase separation due to its thixotropic properties, must be compatible with the surfactants. Finally, the interactions between the low and high HLB emulsifiers at the O/W2 interface should not destabilize the films. It was observed that such destructive interaction for the system could be prevented by the use of two high HLB surfactants in the outer aqueous phase: an amphoteric surfactant, Betaine, and an anionic surfactant, sodium lauryl ether sulfate. The combination of such pairs of surfactants was found to contribute to the films' stability.