An improved method of characterizing fatty acids by equivalent chain length values

A method has been developed for calculating more accurate and reproducible equivalent chain length (ECL) values of 33 straight-chain fatty acids (FA), with various positions and numbers of cis double bonds, chromatographed on DB-Wax and DB-1 columns. The dependence of ECL values on the position and the number of double bonds is described, as is a method of utilizing these relationships for the characterization of FA by gas chromatography.     

Computer-assisted optimization of selectivity by tuning temperature and carrier gas pressure drop in two GC capillary columns coupled in series

The paper shows a computer-assisted procedure for the optimization of selectivity of two columns coupled in series by tuning the working temperature (using the isothermal mode) and columns coupling-point pressure at constant inlet and outlet carrier gas pressures. The optimization procedure validation was tested by the separation of 32 hydrocarbons in a column series with the aim to resolve the maximum number of components in the shortest possible analysis time.Dedicated to Professor J. F. K. Huber on the occasion of his 65th birthday     

High temperature gas chromatography: The development of new aluminum clad flexible fused silica glass capillary columns coated with thermostable nonpolar phases: Part 1

With the simultaneous development of blank aluminum clad flexible fused silica glass capillary tubing capable of withstanding temperatures up to 500°C, coincident with a series of special high temperature methyl polysiloxane polymers, it was possible to produce for the first time, long lived fused silica capillary columns containing thin films of thermostable stationary phases which could be maintained isothermally at 400425°C and temperature programmed to 425–440°C. The “bleed rate” here for a well conditioned column was 5 picoamperes or less. Under these circumstances, alkanes with carbon numbers in the C-90 to C-100 area were rapidly and efficiently eluted from these columns. By extrapolation here, one can easily detect certain compounds with boiling points in the 750°C range. Since this type of capillary column was found to possess certain favorable properties, it was thought that it will soon replace the packed column and will probably be more popular than the borosilicate capillary column for many high temperature applications. Moreover, evidence has now accumulated which leads us to further believe that the majority of analyses of “high molecular weight” compounds performed by Supercritical Fluid Chromatography (SFC), utilizing very narrow bore fused silica capillary columns at several hundred atmospheres, can be much more simply, much more rapidly, much more economically, and much more efficiently accomplished by gas chromatography utilizing this new generation of high temperature capillary columns.     

Theory of shear-induced crystallization of polymer melts

In the presented model elements of polymer melt rheology and polymer crystallization kinetics are combined. In particular, the proneness of the melt to the special type of crystallization which is characteristic for shear treatment is supposed to emerge only gradually during shear flow. Following Avrami's early ideas on crystal growth, an induction time is introduced. In principle, the model can be applied to any flow and temperature history. The special case of isothermal flow at constant shear rate is covered in greater detail: A favorable comparison is made with experimental results, as published by Lagasse and Maxwell [10].Dedicated to Prof. J. Meissner on the occasion for his 60th birthday.     

手性酰胺聚硅氧烷固定相的制备与气相色谱性能

以L-苯丙氨酸,L-缬氨酸为手性源,合成了二种含末端烯基,具有刚性苯基链节的新型手性酰胺单体;并通过硅氢加成方法将其接枝到含氢硅油上,制备了两种新型手性酰胺聚硅氧烷固定相.这一新方法具有简单易行,各步产率较高的优点,所制备的手性固定相具有较好的毛细管柱色谱性能.手性拆分能力和耐温性.     

表面活性剂流动相用于混合固定相薄层色谱

将表面活性剂流动相用于ＧＤＸ与硅胶Ｇ混合固定相薄层色谱,用表面活性剂、乙醇和水的混合流动相对一些水溶性食品染料及指示剂等进行了分离,得到满意的结果,可以部分代替非极性键合相薄板。     

改性环糊精气相色谱手性固定相拆分对映体的选择性及拆分机理的讨论

改性环糊精气相色谱手性固定相拆分对映体的选择性及拆分机理的讨论周昕，万宏，欧庆瑜（中国科学院兰州化学物理研究所兰州７３００００）１前言自１９８８年Ｋｏｎｉｇ￣［１］等人成功地将改性环糊精用于毛细管气相色谱固定相拆分对映体以来，环糊精衍生物以其高选择性...     

含能材料的密度、爆速、爆压和静电感度的理论研究

用密度泛函理论(DFT) B3LYP方法, 在6-31G*基组水平下, 全优化计算了系列硝胺类和硝基芳烃类爆炸物的几何构型, 用Monte-Carlo方法和自编程序, 基于0.001 e•bohr^－3等电子密度面所包围的体积空间求得分子平均摩尔体积(V)和理论密度(ρ). 用Kamlet-Jacobs方程基于理论密度(ρ)和PM3计算生成焓(ΔH_f)估算标题物的爆速(D)和爆压(p), 发现多环硝胺类化合物的爆轰性能优于芳烃硝基类化合物, 故此, 在寻求高能量密度材料(HEDM)时, 我们应特别关注多环硝胺化合物. 与ρ和D文献值比较, 表明本理论计算方法和结果是适用可靠的. 将爆速(D)和爆压(p)计算值与静电感度实验值(E_ES)进行比较和关联, 发现: 若对化合物进行细致分类讨论, 则它们之间存在较好的线性关系. 据此建议, 在含能材料分子设计中, 可通过理论计算爆轰性质(D或p)去预估难以定量求得或尚未合成的含能材料的静电火花感度值(E_ES). 此外, 我们还讨论了取代基对ρ, D和p的影响, 也有助于分子设计.     

(Mn1−xPbx)Pb10+ySb12−yS26−yCl4+yO, a new oxy-chloro-sulfide with ∼2 nm-spaced (Mn,Pb)Cl4 single chains within a waffle-type crystal structure

The new oxy-chloro-sulfide (Mn_1−xPb_x)Pb_10+ySb_12−yS_26−yCl_4+yO (x ∈ [0.2-0.3]; y ∈ [0.3-1.6]) was synthesized by dry way at 500-600 °C. A single crystal ∼Mn_0.7Pb_11.0Sb_11.3S_25.3Cl_4.7O indicates a monoclinic symmetry, space group C2/m, with a = 37.480(8), b = 4.1178(8), c = 18.167(4) Å, β = 106.37(3)°, V = 2690.2(9) Å³, Z = 2. Its crystal structure was determined by X-ray single crystal diffraction, with a final R = 5.11%. Modular analysis of the crystal structure reveals a “waffle” architecture, where complex rods with lozenge section delimitate an internal channel filled by a single chain of (Mn_0.7Pb_0.3)Cl₆ octahedra connected by opposite edges. Minimal inter-chain distances are close to 18 Å. The rod wall, two-atom thick, presents, in alternation with S atoms, Pb or (Pb,Sb) cations with prismatic coordination in the internal atom layer, while the external atom layer is constituted exclusively by Sb cations with dissymmetric square pyramidal coordination. A (Pb,Sb)₂S₂ fragment connects two successive rods along (2 0 1) to form a waffle-type palissadic layer. The unique O position, half filled, presents the same environment than the isolated O positions in the oxy-sulfide Pb₁₄Sb₃₀S₅₄O₅, or oxy-chloro-sulfides Pb₁₈Sb₂₀S₄₆Cl₂O and (Cu,Ag)₂Pb₂₁Sb₂₃S₅₅ClO. This compound belongs to a pseudo-homologous series of chalcogenides with waffle structure, ordered according to the size of their lozenge shape channel. Such a complex senary compound of the oxy-chloro-sulfide type illustrates the structural competition between three cations, on one hand, and, on the other hand, three anions. This compound is of special interest regarding the 1D distribution of magnetic Mn²⁺ atoms at the ∼2 nm scale.     

Multiple discrete energy levels and the bistable state of weak anchoring NLC cells

The weak anchoring nematic liquid crystal (NLC) cell is investigated with regard to energy. Because the Gibbs free energy of liquid crystal system used in theory does not include temperature and entropy, and because the equations and boundary conditions for δG=0 are also the mechanical equilibrium conditions of the continuum, the Gibbs free energy G is equivalent to the energy E of the liquid crystal continuum. There are multiple solutions which satisfy these equations and boundary conditions, each solution corresponding to a certain energy value. We call these discrete energy values and energy levels. Adopting a simple liquid crystal cell model, the energy levels are calculated in detail by means of analytical and numerical methods. The results show that there are three energy levels (or more in certain cases). The values and sequence of the energy levels are related to the external field and anchoring parameters. The relationships between the energy level structure and the bistable. Fréedericksz transition are disussed, together with their influence on the response time. The physical condition for the existence of more than three energy levels is also given.