Simultaneous liquid chromatographic determination of metals and organic compounds in pharmaceutical and food-supplement formulations using evaporative light scattering detection

A novel method for the non-derivatization liquid chromatographic determination of metals (potassium, aluminium, calcium and magnesium) and organic compounds (ascorbate and aspartate) was developed and validated based on evaporative light scattering detection (ELSD). Separation of calcium, magnesium and aluminium was achieved by the cation exchange column Dionex CS-14 and an aqueous TFA mobile phase according to the following time program: 0-6 min TFA 0.96 mL L⁻¹, 6-7 min linear gradient from TFA 0.96-6.4 mL L⁻¹. Separation of potassium, magnesium and aspartate was achieved by the lipophilic C₁₈ Waters Spherisorb column and isocratic aqueous 0.2 mL L⁻¹ TFA mobile phase. Separation of sodium, magnesium, ascorbate and citrate was also achieved by the C₁₈ analytical column, according to the following elution program: 0-2.5 min aqueous nonafluoropentanoic acid (NFPA) 0.5 mL L⁻¹; 2.5-3.5 min linear gradient from 0.5 mL L⁻¹ NFPA to 1.0 mL L⁻¹ TFA. In all cases, evaporation temperature was 70 °C, pressure of the nebulizing gas (nitrogen) 3.5 bar, gain 11 and the flow rate 1.0 mL min⁻¹. Resolution among calcium and magnesium was 1.8, while for all other separations was ≥3.2. Double logarithmic calibration curves were obtained within various ranges from 3-24 to 34-132 μg mL⁻¹, and with good correlation (r > 0.996). Asymmetry factor ranged from 0.9 to 1.9 and limit of detection from 1.3 (magnesium) to 17 μg mL⁻¹ (ascorbate).The developed method was applied for the assay of potassium, magnesium, calcium, aluminium, aspartate and ascorbate in pharmaceuticals and food-supplements. The accuracy of the method was evaluated using spiked samples (%recovery 95-105%, %R.S.D. < 2) and the absence of constant or proportional errors was confirmed by dilution experiments.     

贵金属纳米颗粒杂化囊泡的制备及拉曼增强效果研究

以超支化聚合物囊泡为模板制备了贵金属纳米颗粒表面功能化的杂化囊泡.模板囊泡通过多巴胺修饰的超支化聚醚HSP-DA在水中自组装形成.在碱性条件下,囊泡表面的多巴胺自聚合生成聚多巴胺,实现囊泡的交联.由于聚多巴胺具有强黏附特性,因此可以将HSP-PDA交联囊泡分别与Au纳米溶胶、Ag纳米溶胶直接混合,得到Au纳米颗粒或Ag纳米颗粒功能化的杂化囊泡.分别测定了2种杂化囊泡的拉曼光谱,发现杂化囊泡产生了明显的表面增强的拉曼光谱(SERS)信号,清晰显示了对应于囊泡模板分子的拉曼信号,表明可以通过SERS来原位检测囊泡的组成.Ag纳米颗粒杂化囊泡展示出更高的SERS灵敏度,可进一步作为探针检测水中浓度为10-7mol/L罗丹明6G分子,得到了显著增强的拉曼光谱,证明所制备的Ag纳米颗粒杂化囊泡可用于目标分子的痕量检测.     

Influence of arm length and number on star-shaped poly(2-isopropyl-2-oxazoline) aggregation in aqueous solutions near cloud point

Four-arm star-shaped poly(2-isopropyl-2-oxazolines) (PiPrOx₄) are synthesized by cationic polymerization on t-butylcalix[4]arene macroinitiator. The obtained samples differ by polymerization degree of arms N_PiPrOx = 9 and 25 and are characterized in chloroform. The behavior in aqueous solutions is studied by light scattering methods and compared with the results of investigation of eight-arm star with similar structure. Three types of particles are observed in solution of short-arm PiPrOx₄ at room temperature, whereas only two particle types are present in long-arm star solution. Arm shortening leads to widening of the phase transition interval. The arm number decreasing reduces the phase transition temperature by 1°C.     

Angle‐dependent light scattering by highly uniform colloidal rod‐shaped microparticles: Experiment and simulation

While extensive theoretical work has been devoted to analyzing scattering behavior for nonspherical particles, few experimental studies of the light‐scattering properties of such particles are available, largely because of the difficulty of synthesizing such particles with uniform geometries. Here we report the synthesis of highly uniform, volume‐equivalent rod‐shaped colloidal particles prepared from their commercial spherical counterparts, on which we performed light scattering experiments as a function of scattering angle for micro rods with varying aspect ratio and volume. These results were compared to values calculated using the T‐Matrix method. Good agreement with theoretical predictions was found for the experimentally measured scattering cross sections and the angular dependence of the scattering intensity. An increase in the forward scattering intensity is observed and predicted for particles with larger aspect ratios relative to their volume equivalent spheres, with only minor differences observed at both mid‐range and backscattering angles. Furthermore, the light scattering results for the rod‐shaped particles did not show the scattering fringes seen in scattering by the spheres, indicating that as three‐dimensional symmetry is broken, the associated Lorenz–Mie resonances are strongly attenuated. This observation also was predicted by theory. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1889–1895     

Influence of Structural Features on the Cellular Uptake Behavior of Non‐Targeted Polyester‐Based Nanocarriers

The development of delivery systems efficiently uptaken by cells is of due importance since sites of drug action are generally localized in subcellular compartments. Herein, naked and core–shell polymeric nanoparticles (NPs) have been produced from poly(lactic‐co‐glycolic acid)—PLGA, poly(ethylene oxide)‐b‐poly(ε‐caprolactone)—PEO‐b‐PCL, and poly(ethylene oxide)‐b‐poly(lactic acid)—PEO‐b‐PLA. The nanostructures are characterized and the cellular uptake behavior is evaluated. The data evidence that cellular uptake is enhanced as the length of the hydrophilic PEO‐stabilizing shell reduces and that high negative surface charge restricts cellular uptake. Furthermore, NPs of higher degree of hydrophobicity (PEO‐b‐PCL) are more efficiently internalized as compared to PEO‐b‐PLA NPs. Accordingly, taking into account our recent published results 1 and the findings of the current investigation, there should be a compromise regarding protein fouling and cellular uptake as resistance to nonspecific protein adsorption and enhanced cellular uptake are respectively directly and inversely related to the length of the PEO‐stabilizing shell.

     

Small-angle X-ray scattering studies of the open and closed conformations of aspartate aminotransferase

Summary Aspartate aminotransferase was investigated by X-ray small-angle scattering. A small difference was found between the open (active) and the closed (liganded) conformation of the enzyme. The results were compared with X-ray crystallography data.

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Untersuchungen zur Röntgenkleinwinkelstreuung der offenen und geschlossenen Konformation von Aspartat-Aminotransferase

Zusammenfassung Aspartat-Aminotransferase wurde mittels Röntgenkleinwinkelstreuung untersucht. Ein kleiner Unterschied zwischen der offenen (aktiven) und der geschlossenen (ligandierten) Konformation wurde gefunden. Die Ergebnisse wurden mit Röntgenkristallstrukturdaten verglichen.

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Abbreviations AspAT aspartate aminotransferase     

求解非弹性散射中耦合孔道方程组的一种混合方法

给出了求解原子-分子散射理论中耦合孔道方程组的一种混合方法,该法在强相互作用区域为Johnson的LOGD算法,在其余区域用参照势能具有V=-(A²/16)+Be^-AR形式的势能追踪方法,并以Lester-Bernstein的刚性转子问题为例进行了验证。     

Automatic sugar analysis in the beet industry. Part I: Parameter optimization of a reversed phase HPLC carbohydrate determination

An evaluation of the most commonly used HPLC system (reversed phase octadecyl sillica gel) was undertaken in order to determine the level of certain carbohydrates in molasses produced in the refining of sugar beet. Chromatographic parameters and purification operations prior to analysis are discussed in order to develop an analytical method permitting automation of sugar determination. A Zorbax ODS column (250 × 9.4 mm), water elution, and light scattering detection allow easy determination of glucose + fructose, sucrose, and raffinose in molasses using an internal standard (maltose).     

Laser irradiation induced spectral evolution of the surface-enhanced Raman scattering(SERS) of 4-tert-butylbenzylmercaptan on gold nanoparticles assembly

The spectral evolution of the surface-enhanced Raman scattering (SERS) of 4-tert-butylbenzylmer-captan (4-tBBM) on gold nanoparticles assembly under laser irradiation is reported. The relative intensities of typical peaks in the spectrum of 4-tBBM gradually change with irradiation time. Comparison of the rate of spectral changes under several experimental conditions indicates that the surface plasmon resonance (SPR) induced heat in the gold nanoparticles assembly is the origin of the spectral evolution. During the process of self-assembly, 4-tBBM molecules do not form a compact ordered monolayer because of the spatial hindrance of the 4-tert-butyl end group. The heat induced by laser irradiation drives the 4-tBBM molecules to rearrange to a more stable orientation.     

甲基紫共振瑞利散射光谱法测定透明质酸钠

在pH5的乙酸盐缓冲介质中,甲基紫与透明质酸钠作用形成结合产物时将导致溶液共振瑞利散射(RRS)大大增强并产生新的RRS光谱,其最大散射峰位于341 nm处。透明质酸钠在0~2.5 mg.L-1范围内其浓度与RRS强度成正比。该法具有高灵敏度,对透明质酸钠的检出限(3σ)为20.1μg.L-1,选择性较好。此法用于测定从鸡冠组织中提取的透明质酸的粗品,测定结果的平均相对标准偏差为2.3%,加标平均回收率为98.9%。