沉淀二氧化硅消光剂的制备研究

涂料中的消光剂是一类能够改变涂膜表面光学性能的助剂。这类助剂能够在涂膜表面产生预期微粗糙度,使涂膜的光泽显著降低,给人一种古朴典雅的感觉。近几年来,我国的涂料工业方兴未艾,涂料总产量也跃居世界的前列。在这期间高光泽的亮光涂料以其色泽鲜艳、明亮等优点深受消费者的喜爱,并在相当长的时间内一统着涂料市场[1]。但是,随着人们生活水平的不断提高,一方面消费者感觉到了高光泽的亮光涂料成膜后反光比较严重,对人的眼睛有害;另一方面消费者的审美观念越来越倾向于休闲、时尚和个性化。这些因素就导致了人们对具有柔和外观的低光泽涂…     

An application of factorial design to the development of fused silica capillary columns

Stationary phase crosslinking conditions for fused silica capillary columns were optimized with the use of a factorial design experiment. This experimental strategy was chosen because it provided for the determination of two-factor interactions. A predictive model was developed for the desired chromatographic performance parameters as a function of the variables of the crosslinking reaction. Confirmatory experiments proved the usefulness of the mathematical model which resulted in the production of capillary columns of superior performance with significant improvements in reproducibility.     

Solid-phase extraction of iron(III) with an ion-imprinted functionalized silica gel sorbent prepared by a surface imprinting technique

A new Fe(III)-imprinted amino-functionalized silica gel sorbent was prepared by a surface imprinting technique for selective solid-phase extraction (SPE) of Fe(III) prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Compared with non-imprinted polymer particles, the ion-imprinted polymers (IIPs) had higher selectivity and adsorption capacity for Fe(III). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Fe(III) was 25.21 and 5.10 mg g⁻¹, respectively. The largest selectivity coefficient of the Fe(III)-imprinted sorbent for Fe(III) in the presence of Cr(III) was over 450. The relatively selective factor (α_r) values of Fe(III)/Cr(III) were 49.9 and 42.4, which were greater than 1. The distribution ratio (D) values of Fe(III)-imprinted polymers for Fe(III) were greatly larger than that for Cr(III). The detection limit (3σ) was 0.34 μg L⁻¹. The relative standard deviation of the method was 1.50% for eight replicate determinations. The method was validated by analyzing two certified reference materials (GBW 08301 and GBW 08303), the results obtained is in good agreement with standard values. The developed method was also successfully applied to the determination of trace iron in plants and water samples with satisfactory results.     

Synthesis of siloxane stationary phases for capillary gas chromatography and supercritical fluid chromatography

A comparison is made between dichlorosilanes and cyclic siloxanes as starting materials in the synthesis of stationary phases for capillary gas chromatography (CGC) and supercritical fluid chromatography (SFC). Siloxanes containing one or more of the side groups methyl, vinyl, phenyl, and cyanoethyl in various ratios were synthesized and compared. These phases were characterized by chromatographic (gel permeation, GPC), spectroscopic (IR, ¹H NMR, ²⁹Si NMR), and thermal (DSC) methods. Coated fused silica columns were evaluated with respect to polarity, crosslinkability with several free-radical initiators, and thermal stability. A new liquid phase, 7% cyanoethyl, 7% phenyl, 1% vinyl methyl polysiloxane is shown to be more polar than OV-1701, more temperature stable, easily crosslinked and suitable for use in supercritical fluid chromatography.     

Glass capillary columns for separation of free organic acids

Glass capillary columns have been prepared without acidic additive in the stationary phase, from which free organic acids elute as sharp and symmetrical peaks. The required surface in the borosilicate glass capillary was generated by a combination of leaching with aqueous HCl and deposition of colloidal silica particles; it can be coated with stationary phases have a broad range of polarity. Aqueous samples containing free organic acids can also be analyzed in such columns in an isothermal mode.     

Modification of HPTLC-plates by in situ chemical bonding with non-polar and polar organosilanes

A method has been developed for the preparation of modified silica plates for high performance thin-layer chromatography (HPTLC). Some typical organosilanes were thus allowed to react in situ with the silica of Merck HPTLC-plates. This method was found to be highly reproducible, simple and cheap. Non-polar plates were prepared and compared with commercial plates from Merck, Whatman and Macherey-Nagel. Modification with cyanodecyltrichlorosilane resulted in plates that showed good coverage, efficiency and low residual silica activity. Silica modified with a multifunctional silane has different properties in different organic solvents. It will appear to be non-polar in a polar solvent and vice versa. New advantageous separation systems are thus made feasible by the presence of cyano groups on the plate. The utility of modified thin-layer plates is demonstrated by the separation of some homologues of p-hydroxybenzoic acid esters and of some polycyclic aromatic hydrocarbons.     

Thermosensitive mucoadhesive gel formulation loaded with 5-Fu: cyclodextrin complex for HPV-induced cervical cancer

Human Papilloma Virus (HPV) infections are the major cause of cervical cancers. To achieve a better therapeutic efficacy and patient compliance in the treatment for HPV-induced cervical cancers, anticancer agent 5-fluorouracil has been formulated in a vaginal gel using the thermosensitive polymer Pluronic^® F127 together with alternative mucoadhesive polymers e.g., hyaluronic acid, Carbopol 934 and hydroxypropylmethylcellulose. To increase its aqueous solubility and to achieve the complete release of 5-FU from the gel, the drug was incorporated as its inclusion complex with 1:1 molar ratio with either β-cyclodextrin or hydroxypropyl-β-cyclodextrin. Following the characterization of drug:CD complexes, thermosensitive gel formulations containing different mucoadhesive polymers and the drug in free or complexed form were characterized in vitro by determining the gelation temperature and the rheological behavior of different formulations along with the in vitro release profiles of these formulations in pH 5.5 citrate buffer. It was observed that complexation with cyclodextrin accelerated the release of 5-FU with the exception of formulation containing Carbopol 934 as mucoadhesive polymer. As far as rheological properties are concerned, favorable thermosensitive in situ gelling properties were obtained with formulations containing HPMC as mucoadhesive polymer. Complete release of 5-FU from gels were obtained with both complexes of β-CD and HP-β-CD and cytotoxicity studies against HeLa human cervical carcinoma cells demonstrated that 1% 5-FU:CD complexes were equally effective as 1% free 5-FU indicating better therapeutic efficacy with lower dose.     

An efficient, rapid and regioselective nuclear bromination of aromatics and heteroaromatics with NBS using sulfonic-acid-functionalized silica as a heterogeneous recyclable catalyst

A simple, efficient and rapid method has been developed for high-yielding regioselective nuclear monobromination of aromatic and heteroaromatic compounds using NBS in the presence of sulfonic-acid-functionalized silica at room temperature. The catalyst works under heterogeneous conditions and can be recycled.     

巯基葡聚糖凝胶分离富集光度法测定镉的研究

研究了在ＴｒｉｔｏｎＸ－１００存在下，新显色剂邻羧基苯基重氮氨基偶氮苯（ＣＤＡＡ）与镉的显色体系，在ｐＨ１０．６的Ｎａ２Ｂ４Ｏ７－ＮａＯＨ体系中，显色反应灵敏度很高。络合物的最大吸收位于５４５ｎｍ处，其摩尔吸光系数为２．２２×１０＾５Ｌ·ｍｏｌ＾－１·ｃｍ＾－１。镉含量在０￣１２μｇ／２５ｍＬ符合比耳定律。将该体系用于巯基葡聚糖凝胶分离富集－光度法测水样中微量镉，结果令人满意。     

硅基交联聚酸正丁酯反相HPLC固定相的研究

采用硅胶表面直接交联聚合法，制备了硅基交联聚丙烯酸正丁酯反相高效液相色谱固定相。用红外、扫描电镜和元素分析等方法对固定对进行了表征。考察了固定相对含氧芳烃衍生物的分离。