Chromatography in fluidized beds

Summary Chromatography is carried out under the conditions of fluidization, in long, straight tubes under organized and non-organized conditions. Under non-organized conditions the column is filled only with a sorbent. In organized conditions, either metal coils are added into the column or a segmented column is utilized with metal grids. The results obtained are compared to those obtained under fixed-bed conditions when the column is completely filled with the sorbent. Organized fluidized beds provide a significant decrease in longitudinal bandspreading.     

Suzuki-Miyaura Cross-Coupling of Benzylic Bromides Under Microwave Conditions

A procedure for benzylic Suzuki-Miyaura cross-coupling under microwave conditions has been developed. These conditions allowed for heterocyclic compounds to be coupled. Optimum conditions found were Pd(OAc)₂, JohnPhos as the catalyst and ligand, potassium carbonate as the base, and DMF as the solvent. Using these conditions, a library of structurally diverse compounds was synthesized.     

Efficiency losses caused by gradients in solute velocity in packed column supercritical fluid chromatography

Summary Under a few sets of extreme conditions, retention gradients caused losses in apparent efficiency in packed column SFC. Under most practical chromatographic conditions no such losses occurred. The efficiency of five columns were measured both individually and connected in series. Under most conditions, no loss occurred. Under a few sets of conditions, the apparent efficiency of the five columns connected in series was as much as 66 % lower than the sum of the efficiencies of the individual columns measured under the same conditions. To observe a loss, the local retention near the column outlet must be unrealistically high and a steep non-linear change in retention is required. Under some sets of conditions, an approximate form of a recently proposed theory predicted losses similar to those observed.     

Importance of dynamic culture for evaluating osteoblast activity on dense silicon-substituted hydroxyapatite

This paper reports an investigation on human osteoblast-like cells (SaOs-2) seeded onto pure hydroxyapatite (HA) and silicon-substituted HA (SiHA) tablets under static and dynamic culture conditions. The biological characterizations were conducted in classical static conditions in multi-wells plates, and in a perfusion bioreactor that permits continuous circulation of culture medium at 2 mL/h. The morphology, proliferation and differentiation of osteoblastic cells were examined for the two types of samples in the both culture conditions after 1, 3 and 8 days. Under dynamic conditions, cells cultured on SiHA surfaces showed a faster adhesion process and the formation of longer and thinner focal adhesions than in static conditions. The number of cells grown onto both ceramic surfaces was higher in dynamic conditions when compared with static conditions. Moreover, a higher activity of alkaline phosphatase was found for cells seeded under dynamic conditions. Our findings suggest that the application of perfusion culture system on cells cultured on dense substrates is valuable for predicting in vivo behaviour of cells on biomaterials.     

Comparative Study on Decomposition of CFCl<Subscript>3</Subscript> in Thermal and Cold Plasma

Decomposition of CFCl₃ was investigated in an RF inductively coupled thermal reactor in neutral, oxidative and reductive conditions, and in a silent electric discharge (cold plasma) in neutral and oxidative conditions, respectively. In RF thermal plasma reactor, in neutral conditions, mainly gaseous products and minor amount of solid soot was formed. About 50% the soot could be extracted by toluene. Both the gas phase and the extract contained a wide range of aliphatic and aromatic compounds including chlorine and fluorine containing polyaromatic hydrocarbons (PAHs). In oxidative conditions much less soot was formed as compared to the neutral case. The solid product contained about 45% extractable fraction even in oxidative conditions. However, the extract contained less PAHs than in neutral conditions. In reducing atmosphere the soot yield was similar to the neutral case, but the soot contained 29% extractable fraction only. The extract consisted of polyhalogenated aromatic and polyaromatic hydrocarbons as main components. In neutral conditions different chlorofluorocarbons (CFCs) and chlorine were detected as gaseous products in cold plasma. In oxidative conditions, as final products of decomposition CO₂, CFCs and Cl₃ were formed.     

Modeling of the plasma sintering process at reduced pressures

Numerical simulation of the thermal behavior of sintering specimen under RF plasma conditions at reduced pressure is considered. A two-dimensional approach is adopted for describing flow, temperature, and electromagnetic fields in the reactor with appropriate boundary conditions. Slip boundary conditions are imposed for the velocity field at the sample surface and at the wall of the reactor, and corresponding jump boundary conditions are specified for the temperature field. Simple kinetic theory is employed for the calculation of the heat flux from the plasma to the specimen. The so-called capture-radiative-cascade model is adopted for ionization and recombination processes. The results indicate that ion-electron surface recombination is the dominant heat transfer mechanism to the sintering specimen under reduced pressure conditions.     

Advanced kinetic tools for the evaluation of decomposition reactions

Summary An advanced kinetic study on the thermal behaviour of pyrotechnic ignition mixtures has been carried out by differential scanning calorimetry using different B/KNO3 mixtures (50:50, 30:70, 20:80) as a model reaction. The experimental conditions applied (isochoric conditions/closed crucibles and isobaric conditions/open crucibles) as well as the composition of the mixtures noticeably influences the relative thermal stabilities of the energetic materials. The kinetic study focused on the prediction of the thermal stability of the different mixtures both in extended temperature ranges and under temperature conditions at which ordinary investigation would be very difficult. Using advanced numerical tools [1], thermal ageing and influence of the complex thermal environment on the heat accumulation conditions were computed. This can be done for any surrounding temperature profile such as isothermal, non-isothermal, stepwise, modulated, shock, adiabatic conditions and additionally for temperature profiles reflecting real atmospheric temperature changes (yearly temperature profiles of different climates with daily minimal and maximal fluctuations). Applications of accurate decomposition kinetics enabled the determination of the time to maximum rate under adiabatic conditions (TMR_ad) with a precision given by the confidence interval of the predictions. This analysis can then be applied for the examination of the effects of the surrounding temperature for safe storage or transportation conditions (e.g. determination of the safe transport or storage temperatures).     

Interface-Induced Coarsening Process in Polymer Blends

The coarsening process of the droplets in a two-phase polymer blend (PP/EVAc) was studied under two-dimensional and three-dimensional conditions using a phase contrast microscope and computer image analyzer. The results showed that under three-dimensional conditions the growth of the droplet's radius with time follows r(3) approximately t(1.01), corresponding to the evaporation-condensation theory of Lifshitz-Slyozov, r(3) approximately t, while under two-dimensional conditions the growth law is r(3) approximately t(1.31). The growth rate of the droplets under two-dimensional conditions is faster than that under three-dimensional conditions. This difference is caused by an interfacial interaction (wetting effects) between the substrates and polymer blend. The existence of the interface promoted the coarsening process of the polymer blend under two-dimensional conditions. Copyright 2001 Academic Press.     

Degradation and metabolism of imazapyr in soils under aerobic and anaerobic conditions

The degradation of imazapyr in four soils was investigated under laboratory aerobic and anaerobic conditions. Under aerobic conditions, imazapyr degraded faster in yellow–red soil than in other soils, and its persistence decreased depending on soil pH in the order coastal soil (pH 8.8)?>?silt-loamy paddy soil (pH 7.9)?>?fluvio-marine yellow loamy soil (pH 7.1)?>?Yellow–red soil (pH 5.3). However, soil pH did not affect imazapyr degradation under anaerobic conditions. The half-lives of imazapyr in soils under aerobic conditions were in the range of 26–44 days estimated by the first-order kinetics model, while 3–10 days calculated by two-stage model under anaerobic conditions. The preceding results demonstrated that anaerobic conditions contributed to imazapyr disappearance in soils. Based on the spectral data of APCI-MS, ¹H NMR and IR, structures of the following metabolites: 2,3-pyridinedicarboxamide, 2,3-pyridinedicarboxylic anhydride and 2,3-pyridinedicarboximide for aerobic treatments; 2,3-pyridinedicarboxylic anhydride and 2-(4-hydroxy-5-oxo-2-imdazolin-2-yl) nicotinic acid for anaerobic treatments, were identified. Degradation mechanism under the different conditions was also discussed.     

Exo/endo stereocontrolled synthesis of spiroindoloindolizidines by using classical and microwave conditions via the 1,3-dipolar cycloaddition reaction

Using both classical reflux and microwave-mediated conditions, a series of new spiroindoloindolizidines was synthesized by multicomponent 1,3-dipolar cycloaddition of azomethine ylides in unprecedented exo/endo stereocontrolled. Both conditions easily afforded two identical and separable exo/endo diastereomeric ratios of cycloadducts. However, the ratio of two diastereomeric products obtained from conventional conditions was reversed in all examined cases when the reactions were explored under microwave-mediated conditions. As expected, utilizing the microwave-assisted conditions produced higher yields and reaction rates compared to classical conditions. The structure and exact stereochemistry of synthesized cycloadducts were determined by applying various 2D-NMR spectroscopic techniques and single-crystal X-ray diffraction. Finally, the mechanism of the reaction has been briefly investigated by using density functional theory (DFT) calculations.     

可调移动重叠分离图法用于高效液相色谱多台阶梯度分离条件优化的研究

计算机辅助高效液相色谱（HPLC）分离条件优化可以低成本、快速地得到优化的分离条,因而已较为广泛地用于复杂样品的分离分析。基于移动重叠分离图方法,又发展了一种新型的多台阶梯度分离条件的优化方法可调移动重叠分离图法。该方法通过预测不同流动相条件下各组分的保留时间、峰宽和分离度,绘制出对于样品中各组分的重叠分离区域图。在对当前台阶流动相组成进行优化的同时,考虑其对后面一到两个台阶上流出组分保留的影响,实时地重新绘制对于后面台阶上流出组分的重叠分离区域图。通过观察当前台阶流动相条件对当前台阶和后面台阶上流出组分分离的影响,综合考虑样品中所有组分的分离情况,找到更接近全局最优的分离条件。通过扫描的方法对优化得到的分离条件进行微调,能够进一步提高分离效果。采用文献数据对可调移动重叠分离图法的应用加以说明,在二元流动相体系下,证明了该方法在HPLC方法建立方面的优越性。     

pH值对硅油乳液Zeta电位及其制备的影响

1994年,T．M．Obey和V．Brian采用二甲基二乙氧基硅烷在氨水催化剂下进行乳液聚合,获得了具有较好单分散性的聚二甲硅油乳液。本文研究了pH值对二甲基二乙氧基硅乳液Zeta电位的影响,比较了有相同单体浓度的单相体系在低pH值(酸性)和高pH值(碱性)条件下乳液聚合的规律,以期对硅烷乳液制备做更进一步的研究。     

钼酸铁超微粒子的制备及其选择性氧化正丁醇的研究

以Fe(NO3)3·9H2O和(NH4)6Mo7O24·4H2O为原料,采用溶胶-凝胶法于不同条件下制备Fe2(MoO4)3超微粒子催化剂,并研究了这些催化剂对正丁醇选择性氧化制备正丁醛的催化性能,从而找出Fe2(MoO4)3超微粒子催化剂选择性氧化正丁醇的最佳实验条件。结果表明,制备Fe2(MoO4)3超微粒子的适宜条件为:溶液初始pH=1.0,以EDTA为螯合剂,EDTA/(铁+钼)摩尔比为0.4时制得的催化剂对正丁醇的选择性氧化性能最好,此时正丁醛的产率可达39.3%。     

Effect of Ultrasound-Assisted,Microwave-Assisted and Ultrasound-Microwave-Assisted Extraction on Pectin Extraction from Industrial Tomato Waste

This work aimed to study the effect of ultrasound-assisted (UAE), microwave-assisted (MAE), and ultrasound-microwave-assisted (UMAE) methods for pectin extraction from industrial tomato waste. The overall performance index from the fuzzy analytical method with three criteria, pectin yield, galacturonic acid, and lycopene content, was applied to evaluate the best extraction conditions by using the weight of 75, 20, and 5, respectively. The UAE conditions was performed at a temperature of 80 °C for 20 min with the variations in the extraction pH and the solid liquid (SL) ratio. The best UAE conditions with high pectin yield, and high total carboxyl group, as well as a lycopene content, was the pH of 1.5 and the SL ratio of 1:30. The MAE conditions was performed with variations in the microwave powers and times. The results showed that the best MAE conditions were 300 W for 10 min, which gave high pectin yield with high galacturonic acid and lycopene content. Various conditions of UMAE at the best conditions of MAE and UAE were performed and exhibited that the UAE had more positively affected the pectin yield. However, the FTIR spectra of obtained pectins from different extraction techniques showed a similar pectin structure.     

Cycloisomerization of Olefins in Water

Preparative reactions that occur efficiently under dilute, buffered, aqueous conditions in the presence of biomolecules find application in ligation, peptide synthesis, and polynucleotide synthesis and sequencing. However, the identification of functional groups or reagents that are mutually reactive with one another, but unreactive with biopolymers and water, is challenging. Shown here are cobalt catalysts that react with alkenes under dilute, aqueous, buffered conditions and promote efficient cycloisomerization and formal Friedel–Crafts reactions. The constraining conditions of bioorthogonal chemistry are beneficial for reaction efficiency as superior conversion at low catalyst concentration is obtained and competent rates in dilute conditions are maintained. Efficiency at high dilution in the presence of buffer and nucleobases suggests that these reaction conditions may find broad application.     

Cycloisomerization of Olefins in Water

Preparative reactions that occur efficiently under dilute, buffered, aqueous conditions in the presence of biomolecules find application in ligation, peptide synthesis, and polynucleotide synthesis and sequencing. However, the identification of functional groups or reagents that are mutually reactive with one another, but unreactive with biopolymers and water, is challenging. Shown here are cobalt catalysts that react with alkenes under dilute, aqueous, buffered conditions and promote efficient cycloisomerization and formal Friedel–Crafts reactions. The constraining conditions of bioorthogonal chemistry are beneficial for reaction efficiency as superior conversion at low catalyst concentration is obtained and competent rates in dilute conditions are maintained. Efficiency at high dilution in the presence of buffer and nucleobases suggests that these reaction conditions may find broad application.     

正交试验法优化柠檬酸法氧化铝生产工艺

采用正交试验设计法,以丝钠铝石的收率为指标,考察了碳酸氢钠用量、pH值、反应温度和反应时间等因素对柠檬酸法氧化铝生产工艺的影响。 在优选工艺条件下：NaHCO3与Al摩尔比为5,pH=11,反应温度为80 ℃,反应时间为3 h,柠檬酸铝至丝钠铝石的转化率从原有的65%提高至76%。     

Vitamin U-bonded stationary phase in capillary ion chromatography

A vitamin U-bonded stationary phase was prepared and the retention behavior of inorganic anions was examined using ion chromatography. Inorganic anions were retained on the vitamin U-bonded stationary phase under acidic as well as neutral eluent conditions in the ion-exchange mode. The elution order of the examined anions under neutral eluent conditions was nearly the same as that observed in common ion exchange mode, while the elution order observed under acidic eluent conditions was completely different from that observed in common ion exchange mode. The retention of the analyte anions under the neutral eluent conditions was due to the sulfonium groups of the vitamin U, while protonated primary amino groups caused retention of the analyte anions with different selectivity under acidic conditions. The retention factor of the analyte anions increased with decreasing eluent concentration under both eluent conditions. The present system was applied to the determination of bromide and nitrate contained in seawater.     

Efficient NaOH-Catalyzed Reaction of Aromatic Aldehyde,Cyclic Ketones,and Malononitrile Under Solvent-Free Conditions Using a Grinding Method

An efficient and facile synthesis of 2,6-dicyanoanilines via a one-pot reaction of aromatic aldehydes, malononitrile, and cyclic ketones in the presence of NaOH under solvent-free conditions using a grinding method has been developed. Compared with the classical reaction conditions, the new synthetic method has the advantages of excellent yields, shorter reaction times, and mild reaction conditions.     

Solvation of Ti(IV) in aqueous solution under ambient and supercritical conditions

We examine the structure of the hydrated Ti(IV) complex under both ambient and supercritical conditions using first-principles molecular dynamics. We find that an unanticipated fivefold coordination of Ti(IV) is favoured under ambient conditions, with rapid interconversions between square pyramidal and trigonal bipyramidal structures. At supercritical conditions the Ti coordination increases from five to six, adopting both octahedral and trigonal prismatic geometries. At 1000 K, the magnitude of the increase in the Ti to oxygen coordination number with increasing water density is similar to that of Li-O under comparable conditions. We present a detailed picture of the bonding in the hydrated Ti(IV) complex under both ambient and supercritical conditions.