HPLC on pentalfuoroanilinopropyl silica gel

Summary The preparation of a new pentafluoroanilino-phase for HPLC is described. The retention times (t_r) of about twenty aromatic hydrocarbons have been determinated. It has been shown that the aromatics were eluted according to the number of rings. The influence of water content in the mobile phase is commented.     

Endcapping of high performance liquid chromatography packings derived from silica gel

The effect of endcapping a reversed phase chromatographic packing material derived from silica gel depends on the degree of derivatization of the phase. The effect can be dramatic for phases with low loading. Whether an octadecylated silica gel has been endcapped or not can be ascertained by chromatographing the pair naphthalene/1-nitronaphthalene with a water/methanol eluent producing at least k' ≈ 10 for naphthalene. The ratio of the two k' values is 1.4 or higher for an endcapped material, while it is only 1.1 -1.2 for a non-endcapped phase. A similar approach fails to give conclusions of similar utility for octylated silica gels.     

On-line multidimensional chromatography using supercritical carbon dioxide

A two-dimensional chromatographic separation is described which makes use of the unusual properties of supercritical carbon dioxide mobile phase. This solvent has the property of giving a separation of polycyclic aromatic hydrocarbons (PAH) on amine-bonded columns similar to that given by usual normal-phase solvents, and on octadecylsilane-bonded columns similar to that given by usual reversed-phase solvents. Packed columns were used, arranged so that they could be switched in or out of the solvent flow. Polycyclic aromatic hydrocarbon mixtures isolated from coal tar were fractionated according to number of aromatic carbon atoms on an amine-bonded column, and these fractions were trapped on an octadecysilane-bonded column. They were subsequently eluted according to the polarity of the individual compounds. Separations from fractions containing 16 and 18 aromatic carbon atoms are shown.     

高效液相色谱喹啉醚基键合硅胶固定相的制备及评价

采用固液相连续反应法,以γ-环氧丙氧基)丙基三甲氧基硅烷(KH560)为偶联剂,制备了一种喹啉醚基键合硅胶固定相(QBS),采用元素分析、漫反射红外光谱和热分析表征了固定相的结构。多种溶质为探针(包括非极性的烷基苯和多环芳烃、芳香族化合物位置异构体及极性的核苷和碱基等),较系统地研究了该新固定相的色谱性能。研究表明,新固定相与ODS相比,除具有弱的疏水性外,还能与溶质发生多种作用,如：氢键和π-π作用等。在分离非极性的多环芳烃时主要基于疏水作用;在分离极性的核苷和碱基时,氢键和络合作用较重要;在分离芳香族化合物位置异构体时,溶质极性取代基与喹啉醚基键合相的氢键作用。溶质苯环与喹啉基配体之间的π-π作用,两协同作用提高了QBS对位置异构体的分离选择性。     

High resolution HPLC

In order to justify its classification as a “high resolution” technique, HPLC should show an improvement in efficiency by a factor of at least 10, should be easily achievable with separation times of less than 1 h, preferably in the reversed phase mode. This is accomplished by coupling three 25 × 0.46 cm columns packed with 5 μm spherical ROSiL-C₁₈-D silica gel. Details of the method and some typical chromatograms are given.     

Anthracene silica gel,a new polycyclic-aromatic-bonded stationary phase for HPLC

Summary N(9-methylanthracene)aminopropyl silica gel is introduced as a new reversed-phase packing material. It has specific selectivity for some aromatic compounds. In this paper the anthracene phase is compared with commercial octadecyl-, phenyl- and aminopropyl-bonded silica gels.     

基于L-谷氨酸的手性硅胶球的制备及其应用

无机介孔硅球因其具有足够的机械强度、热稳定性,以及适应多种流动相的优点,成为高效液相色谱(HPLC)柱填料中使用最广泛和最重要的材料.但在此研究领域中,并未见球形的全无机手性硅胶用作HPLC手性固定相.该文以无机球形介孔硅胶作为研究对象,通过堆砌硅珠法,以硅溶胶为原料,L-谷氨酸(L-Glu)为手性源,在手性环境中制造...     

Selectivity of liquid-adsorption chromatography on hydroxylated silica gel with nonpolar and polar eluents

Summary The effect of nonpolar (hexane, decane, benzene) and polar (water, isopropanol, water+isopropanol) eluents on separation of aromatic hydrocarbons and their derivatives in liquid-adsorption chromatography on hydroxylated silica gel columns has been studied. The work has revealed that the traditional application areas of hydroxylated silica gel in liquid chromatography may be extended. In particular it has been shown that, first, polar compounds may be separated on hydroxylated silica gel with nonpolar eluents at high temperatures (100–150°C) and that polar and nonpolar compounds may be separated using pure water as eluent. The effect of adsorbed moisture on retention behaviour of silica gel with nonpolar eluents has also been investigated.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Solvent-free cyclopalladation on silica gel

Tertiary, secondary and primary benzylamines, as well as structurally different oxazolines readily reacted with Pd(OAc)₂ on silica gel to form cyclopalladated complexes containing a five or six-membered palladacycle with a (sp²)C-Pd or (sp³)C-Pd bond. The complexes were obtained in 45-98% yield, which is comparable with or exceeds the yields reported for preparation of the same compounds in solution. Aliphatic (sp³)C-H bond activation took place in the cyclopalladation of (S)-2-tert-butyl-4-phenyl-2-oxazoline on SiO₂ leading to the exclusive formation of the corresponding endo palladacycle, whereas two products were reported for the same reaction performed in AcOH.     

Hydrothermal treatment of silica gel

Summary A simple procedure was developed for preparing wide pore (≦ 40nm) silicas from a common chromatographic silica gel. The effects of various experimental conditions on pore size, pore volume, and surface area are discussed. The results show that under controlled conditions a wide variety of wide pore silica packing materials can be prepared. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

Regularities in the retention of isomeric aromatic hydrocarbons in liquid chromatography II. Analysis of polymethyl- and monoalkylbenzenes on silanized silica gel

Summary The regularities of the retention of polymethyl- and monoalkylbenzenes on a nonpolar adsorbent (silanized silica gel) with a polar eluent (23 isopropanol-water) have been studied. In contrast to the retention of the same compounds on a polar adsorbent (silica gel with hydroxylated surface) and with a nonpolar eluent (hexane) polymethylbenzenes are retained on silanized silica gel for a shorter time than the corresponding monoalkylbenzene isomers. The retention order of tert.-, sec.- and n-butylbenzenes is the reverse of that observed on silica gel having a hydroxylated surface. The retention order of xylenes, trimethyl- and tetramethylbenzenes is also the reverse of their retention order on silica gel having a hydroxylated surface. All the mixtures of the corresponding homologues and isomers have been separated.     

The optimized separation of aromatic carboxylic acids by HPLC

The optimization of the separation of eight aromatic carboxylic acids, using Hypersil SAS and MOS reverse phase columns, with respect to eluent (methanol : water) composition, pH, and temperature, is described. Window diagram techniques are used and the pH of the aqueous buffer and elution temperature are shown to be more critical than eluent composition.