Syntheses of stationary phases for reversed-phase LC using silanization and polymer coating

Summary Various methods and reagents for silanization of silicas originating from different manufacturers were investigated in comparison to the method published by the authors which makes use of an enolate of acetylacetone. This reagent proved to be highly reactive. New types of reversed phase materials were also synthesized by polymer coating applying crosslinking and chemical bonding to the surfaces of silica and alumina. In this work dicumyl peroxide and azo-t-butane were used for radical generation. The reversed phase materials obtained with alumina can be used for separations at P_H-values up to 12. Silica materials begin to already be deteriorated at a P_H-value of 8. Dedicated to Professor G. Wilke on the occasion of his 60th birthday. Presented at the 15th International Symposium on Chromatography, Nürnberg, October 1984     

表面活性剂对制备MoS2纳米微粉的影响

Mo0_2纳米微粉在催化l‘l、敏感元件［‘·’］及磁记录材料［‘］等方面具有特殊用途,其传统制备方法是通过在高温下用氢还原l’,‘l,利用这种方法制备M。0。纳米微粉、所得产品粒子尺寸较大,比表面积小,且反应在条件苛刻,从而限制了M00。纳米微粉的使用范围．文献曾报导用y一辐照法制备了一系列金属、合金和氧化物的纳米粒子”－‘Q’,这种方法利用水辐解产生的水合电子（efo）作为还原剂,具有在常温常压下进行操作的显著优点,因而受到普遍关注．本实验室l‘’1曾报导通过v一辐照法可制备Moo。纳米非晶,其颗粒尺寸为8－30urn…     

包覆聚丁二烯型HPLC柱填料的制备与评价

王俊德等［１］预言,未来的ＨＰＬＣ分离介质很可能是在无机填料表面包敷一层有机聚合物的复合体．因为此类填料既弥补了键合硅胶固定相ｐＨ应用范围窄及残余硅羟基易引起不可逆吸附使峰形拖尾等不足,又克服了聚合物填料的刚性差及难以进行梯度淋洗等缺陷．近年来,关于...     

The Preparation and Properties of Thermosensitive Hydrogels Based on Chitosan Grafted N-isopropylacrylamide via γ-Radiation

Thermosensitivehydrogels. were prepared by graft polymerization of chitosan and N-isopropylacrylamide via ^60Co γ-radiation.The effects of monomer concentration and total irradiation dose on percent grafting and grafting efficiency were studied.The thermosensitivity and swelling properties of the hydrogels were investigated.     

OPTIMIZATION OF THE SYNTHESIS OF ACRYLAMIDE HYDROGEL BY γ-RAY IRRADIATION

Hydrogels have been synthesized from 10%, 20%, 30%, 40%, 50% and 60% aqueous solutions of acrylamide monomer by gamma radiation employing doses in the range of 0.2-30 kGy from a Co-60 source. The effect of solution concentration, y-ray dose, pH and time was studied in order to observe the optimizing conditions in the characterization of hydrogels. Gel fraction increases with dose for all concentrations indicating hundred-percentage conversion of gel at doses ≥5 kGy for homogenous solutions in the range of 20%-50% concentration. On the other hand, 10% solution provides conversion less than 86% even at 30 kGy, whereas 60% monomer makes an inhomogeneous solution which stile gives about 100% gel fraction. Swelling of hydrogels under water with respect to time varies with both the doses and concentrations due to the change of crosslinking density in the gels. The maximum volume change of hydrogels during swelling and water desorption mainly occurs within 24 h. Swelling is also enhanced with the rise of pH due to change of ionic content of the solvent. Considering the amount of gel fraction and the properties of hydrogel, the samples prepared from 20% solution at 5 kGy show better results. Moreover, the effect of bacteria on hydrogel was found to be nil, suggesting a prohibition of growth of microorganism in it.     

X-ray emission from aluminium under intense, ultrashort irradiation

We present studies of X-ray emission from aluminium under picosecond and femtosecond irradiation in the intensity range 10¹²-10¹⁵ W cm^-2. We use a new and simple method to measure spectrally resolved absolute X-ray yields. It is shown that the X-ray yields can be obtained for arbitrary levels of X-ray flux. We present details of the variation of the absolute yields as a function of wavelength, intensity, polarization and pulse duration of the incident laser radiation. Electron temperatures in the keV range are observed at 10¹⁵ W cm^-2 with femtosecond laser pulses. Received 12 August 1999 and Received in final form 29 November 1999     

Hot particles in industrial waste and mining tailings

Industrial waste was studied concerning its radioactive pollution. Using known properties of the solid state nuclear track detector CR-39 we found among a high concentration of more or less homogeneously distributed single α-tracks discrete spots of very high enrichments of α-particles created by so called hot particles. We will report about the α-activity, the concentration of hot particles and about their ability to be air borne.     

Effect of γ-radiation on the phase transition temperature of Li0.5(NH4)0.5SO4

Polycrystalline lithium-ammonium sulphate samples were subjected to X-ray diffraction analysis for determining the lattice parameters of the prepared mixed crystals. The compositions of the samples were determined using X-ray microanalysis.

The Li_0.5(NH₄)_0.5SO₄ samples were irradiated with different doses of γ-radiation in order to investigate the effect of this ionizing radiation on the phase transition temperatures T_c1 and T_c2. The temperature dependence of the d.c. resistivity ρ_d.c. and dielectric constant of irradiated samples showed (i) a shift of T_c1 to higher temperatures; (ii) a shift of T_c2 to lower temperatures; and (iii) the appearance of a new anomaly near 128°C at moderately high γ-doses. The mechanisms giving rise to this behaviour are discussed.     

OPTIMIZATION OF THE SYNTHESIS OF ACRYLAMIDE HYDROGEL BY γ-RAY IRRADIATION

Hydrogels have been synthesized from 10%, 20%, 30%, 40%, 50% and 60% aqueous solutions of acrylamide monomer by gamma radiation employing doses in the range of 0.2-30 kGy from a Co-60 source. The effect of solution concentration, γ-ray dose, pH and time was studied in order to observe the optimizing conditions in the characterization of hydrogels. Gel fraction increases with dose for all concentrations indicating hundred-percentage conversion of gel at doses ≥5 kGy for homogenous solutions in the range of 20%-50% concentration. On the other hand, 10% solution provides conversion less than 86% even at 30 kGy, whereas 60% monomer makes an inhomogeneous solution which stile gives about 100% gel fraction. Swelling of hydrogels under water with respect to time varies with both the doses and concentrations due to the change of crosslinking density in the gels. The maximum volume change of hydrogels during swelling and water desorption mainly occurs within 24 h. Swelling is also enhanced with the rise of pH due to change of ionic content of the solvent. Considering the amount of gel fraction and the properties of hydrogel, the samples prepared from 20% solution at 5kGy show better results. Moreover, the effect of bacteria on hydrogel was found to be nil, suggesting a prohibition of growth of microorganism in it.