HPLC in industry—A well established procedure for characterizing RP-stationary phases

Summary A well established totally automated testing procedure for characterization of RP materials is presented. The test is suited to the determination of hydrophobic and silanophilic interactions, as well as trace metal impurities on silica surfaces. it includes measurements of stationary phase stability and shows column performance at two different pH conditions. The very different parameters examined readily reveal batch to batch reproducibility and are therefore suitable for laboratories dealing with quality control and validation of columns. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

Some more 5‐GDDs and optimal (v), 5, 1)‐packings

In this paper, we continue to investigate the existence of 5‐GDDs with types g⁵ m¹ and g^u. As an application, the known results on the existence of optimal packings with block size 5 are also improved. © 2003 Wiley Periodicals, Inc.     

Patterns and Structures in Disk Packings

Using a computational procedure that imitates tightening of an assembly of billiard balls, we have generated a number of packings of n equal and non-equal disks in regions of various shapes. Our experiments are of three major types. In the first type, the values of n are in thousands, the initial disk configuration is random and a priori one expects the generated packings to be random. In fact, the packings turn out to display non-random geometric patterns and regular features, including polycrystalline textures with "rattlers" typically trapped along the grain boundaries. An experiment of the second type begins with a known or conjectured optimal disk packing configuration, which is then "frustrated" by a small perturbation such as variation of the boundary shape or a relative increase of the size of a selected disk with respect to the sizes of the other disks. We present such frustrated packings for both large n (~ 10, 000) and small n (~ 50 to 200). Motivated by applications in material science and physics, the first and second type of experiments are performed for boundary shapes rarely discussed in the literature on dense packings: torus, a strip cut from a cylinder, a regular hexagon with periodic boundaries. Experiments of the third type involve the shapes popular among mathematicians: circles, squares, and equilateral triangles the boundaries of which are hard reflecting walls. The values of n in these experiments vary from several tens to few hundreds. Here the obtained configurations could be considered as candidates for the densest packings, rather than random ones. Some of these conjecturally optimal packings look regular and the regularity often extends across different values of n. Specifically, as n takes on an increasing sequence of values, n = n(1), n(2), ...n(k), ..., the packings follow a well-defined pattern. This phenomenon is especially striking for packings in equilateral triangles, where (as far as we can tell from our finite computational experiments), not only are there an infinite number of different patterns, each with its own different sequence n(1), n(2), ...n(k), ..., but many of these sequences seem to continue indefinitely. For other shapes, notably squares and circles, the patterns either cease to be optimal or even cease to exist (as packings of non-overlapping disks) above some threshold value n(k0) (depending on the pattern). In these cases, we try to identify the values of n(k0).     

高分子色谱固定相

本文扼要介绍气相色谱和高效液相色谱所应用的各种高分子色谱固定相概况、原理、类型和制备等问题,高分子材料在色谱上的应用及其发展。     

基于遗传算法的色谱指纹峰配对识别方法

指纹峰配对识别是色谱指纹图谱分析中的关键环节之一，本文提出一种基于遗传算法的色谱指纹峰配对识别方法。该法根据对照色谱指纹图谱的峰分布特性初选出若干标定蜂，将其存入一个候选标定蜂库；同时根据这些候选标定峰从待测指纹图谱中选出相应的候选标定峰，也存入候选标定峰库；再用遗传算法从库中选取一组标定峰用于校正待测指纹图谱中各峰的峰位，并自动识别出与对照色谱指纹图谱相对应的各指纹峰。仿真实验及实际分析实验结果均表明，该法识别指纹峰准确可靠，可用于色谱指纹图谱相似度的快速自动计算。     

烟用香精的GC-MS指纹图谱

在卷烟生产中,烟用香精对卷烟的风格起着决定作用,所以稳定的烟用香精质量对卷烟内在品质的控制非常重要。目前,烟用香精的质量控制以物理指标方法为主,对质量的变化反映不显著,给质量控制带来困难。作者采用气相色谱一质谱(GC-MS)测定烟用香精的成分,建立其GC-MS指纹图,既有定量信息又有定性信息,为控制烟用香精的质量提供科学依据。     

Prediction of the chromatographic retention of saturated alcohols on stationary phases of different polarity applying the novel semi-empirical topological index

The novel semi-empirical topological index (I_ET), previously developed by Heinzen and Yunes, was extended to predict the chromatographic retention of saturated alcohols on low polarity stationary phases (OV-1). The predictive ability of I_ET was also verified on stationary phases of different polarity (SE-30, OV-3, OV-7, OV-11, OV-17 and OV-25). Simple linear regressions between the retention indices and the semi-empirical topological index (RI=a+bI_ET) were established for each stationary phase separately, showing good statistical parameters. Statistical analysis showed that the QSRR model used on stationary phases of low polarity (OV-1) has high internal stability and good predictive ability for external groups. The polarity of the SE-30, OV-3, OV-7, OV-11, OV-17 and OV-25 stationary phases, indicated by retention polarity (P_R) given by Tarján et al., is reflected in the ‘a’ (intercept) and ‘b’ (slope) coefficients of the equations obtained for each of these phases. The linear relationship between the ‘a’ coefficient and P_R showed satisfactory statistical quality. Thus, it was possible to generate a single combined model of QSRR, including a parameter that represents the property of the stationary phase P_R. The combined model also has a satisfactory predictive quality, as shown by the plot of calculated versus experimental retention indices for saturated alcohols on six stationary phases of different polarity (r²=0.9956; S.D.=9.54).     

Structural characteristics of close packings of hard spheres. Critical densities

For packings of similar hard spheres, there are several characteristic values of density. First, this is the maximal possible degree of space filling by spheres η = 0.74, realized for the crystalline packing of spheres. Another known value, η = 0.64, is the limiting (critical) value for disordered packings. We also indicate two more characteristic values of density: η = 0.60 and η = 0.66, in the vicinity of which qualitative changes in structure can occur. Computer models of the packings of hard spheres are investigated in the range of densities 0.52 < η < 0.72. Each packing consisted of 10,000 spheres in a cube with periodic boundary conditions. The structural characteristics were investigated using Delaunay simplices, defining the arrangement of the nearest four atoms. Simplices that are close to a regular tetrahedron or quartoctahedron (quarter of an octahedron) are considered. These forms are typical for the densest crystal structures. Variation of the fraction and ratio of these simplices is studied as a function of the packing density. According to the results, the threshold value, η = 0.60, corresponds to the density after which correlation of the disordered arrangement of spheres increases considerably. When η = 0.64, the structural organization changes more radically; high density demands the emergence of local crystal nuclei. The density η = 0.66 is the limiting density at which the crystalline nuclei can exist as independently distributed regions. Closer packings can only occur if a global crystal structure arises in them.     

Study on optimal packing materials for high-performance hydrophobic-interaction chromatography of proteins

Summary The nature and effects of bonded phases and analytical conditions on protein retention in high-performance hydrophobic-interaction chromatography (HIC) were investigated. Silica-based packing materials with different surface hydrophobicity were prepared and evaluated with respect to protein retention. The contact of proteins with the hydrophobic stationary phases caused conformational changes of proteins to some extent, but the extent of these changes was dependent on the hydrophobicity of the stationary phases, column temperature and the proteins themselves. Thermal behavior of some proteins in HIC on these phases is also shown.     

Ion-exchange selectivities of amorphous and anatase-types hydrous titanium dioxides and the possible separation of bivalent transition metal ions

Summary Amorphous and anatase-type hydrous titanium dioxides showed typical amphoteric ion-exchange properties. The ion-exchange selectivity for bivalent transition metal ions was studied as a function of both pH and metal ion concentration in ammonium nitrate media. The selectivity series was Co<Ni<Mn<Zn<Cd<Cu for the amorphous and Ni<Co<Mn<Zn<Cd<Cu for the anatase-type material. The separation factor on the anatase-type material is larger than on the amorphous material. Effective group separation of Co–Ni and Zn–Cd–Cu could be achieved on an ion-exchange column containing the anatase-type hydrous titanium dioxide.Part XXIV in a series on synthetic inorganic ion-exchange materials.