Showing papers on "Silica gel published in 1980"

The structure of γ-aminopropyltriethoxysilane on glass surfaces

Abstract: The structure of γ-aminopropyltriethoxysilane (APS) has been studied in aqueous solution and as a solid using Fourier transform infrared spectroscopy. The monomeric aminosilane forms an internal cyclic chelate structure when hydrolyzed. Two vibrational bands have been found near 1575 and 1600 cm −1 in condensed aminopropylsiloxane polymer. The band at 1575 cm −1 is assigned to the NH 2 deformation mode of the acceptor amine groups involved in strong hydrogen bonding and the band at 1600 cm −1 is assigned to the NH 2 groups. Heat treatment causes the formation of nonring chain-structured aminosilanes. In the study of the structure of APS coupling agent on high-surface-area silica gel (Cab-O-Sil) and E-glass fibers, it was found that the aminosilane adsorbed on silica as essentially a monolayer and the amino group chemically interacted with the glass surface. The adsorbed APS on E-glass fiber exists as a multilayer, and formed a predominately cyclic ring structure in the coupling agent interphase.

Separation of human eosinophils in density gradients of polyvinylpyrrolidone-coated silica gel (Percoll).

Abstract: A method for isolation of eosinophils from human peripheral blood using isosmolar solutions of polyvinylpyrrolidone-coated silica gel (Percoll) is described. The purity ranged from 86 to 99% eosinophils in the final preparation and the recovery was 38-56%. The separation technique did not affect the viability or the metabolic capacities of the cells.

Glass sealed thin-film electroluminescent display panel free of moisture and the fabrication method thereof

Abstract: A thin-film electroluminescent display panel is sealed by a pair of glass substrates for protection from the environment. A protective liquid is introduced between a counter glass substrate and a substrate for supporting the electroluminescent display unit. The protective liquid comprises silicone oil or grease which assures the thin-film electroluminescent film of preservation in the electroluminescent display panel. The counter glass substrate is bonded to the support substrate through an adhesive of, for example, photo-curing resin. A capillary tube is provided within the glass substrate for injecting the liquid under vacuum conditions. The liquid has the capability of spreading into pin holes generated on dielectric layers, and is resistant to high voltage, high humidity and high temperature and is inert to layers constituting the thin-film electroluminescent display panel and has a small vapour pressure and a small coefficient of thermal expansion. A moisture absorptive member is introduced into the protective liquid. The member can be an Al film coated by silica gel or silica gel particles themselves. The silica gel particles, if necessary, may be confined within a tube or dispersed within the spacer. Alternatively, they are dispersed within the protective liquid. The Al film is adhered to one of the substrates. The member serves to absorb moisture contained within the protective liquid. The protective liquid can be colored by a dye material to provide a background for the EL device.

The Silica Gel Surface and Its Interactions with Solvent and Solute in Liquid Chromatography

Abstract: The multilayer formation of water on silica gel is discussed, and experiments indicating the existence of three layers of water are described. The interaction of active silica gel with solvent is also considered. Activated silica gel as used in chromatography appears to contain one strongly hydrogen-bonded water molecule per silanol group which can dispersively interact with non-polar solvents forming a monolayer. In contact with a polar solvent, however, the hydrated silanol group can hydrogen-bond to the polar solvent and form a strongly held solvent layer on top of which a bilayer of polar solvent can form by polar interactions with the first layer. The mechanism of solute interaction with activated silica can be described as follows. Solutes interact with the multilayer surface in a chromatographic column in two ways. If the solvent layer is weakly held by dispersive forces as in the case of a non-polar solvent, the solute can displace the solvent layer and interact directly with the hydrated hydroxyl groups. If, on the other hand, the solvent is polar and is strongly held by hydrogen-bonding forces to the hydrated silanol group, solutes may associate directly with the polar solvent layer but not displace it unless the solute has a polarity similar to the solvent in which case it is consequently eluted at a high k′ value.At low concentrations of polar solvent only a small amount of the second layer of weakly held solvent is formed and thus the interaction of a solute with the surface will be with the primary layer of polar solvent. Under such circumstances, changes in retention resulting from changes in solvent composition will reflect changes in solute interactions with the mobile phase and not with the surface of the stationary phase. Such a system has been examined; it was shown that the probability of polar interactions in the mobile phase were directly related to the concentration of polar solvent, and this was substantiated by results obtained from the examination of liquid/liquid distribution systems. Evidence was also provided that indicated that the magnitude of polar interactions was related to the polarizability per cm3 of the interacting substances.

Determination of physisorbed and chemisorbed waters on silica gel and porous silica glass by means of desorption isotherms of water vapor

Abstract: The surface interaction of water vapor with the hydroxylated and dehydroxylated surfaces of silica gel and porous silica glass has been investigated by measuring the adsorption and desorption isotherms of water vapor at 20°C. On the dehydroxylated surfaces, true adsorption equilibrium was not obtained in the first adsorption isotherms because of slow chemisorption, but the first desorption ones held true equilibrium. The chemisorbed water determined from the last point of the first desorption isotherm increases as the pretreatment temperature increases until 600°C, and then decreases. From comparison between the chemisorbed water and the amount of water eliminated by thermal treatment, the degree of the rehydroxylation on both silica gel and porous silica glass has been determined. The rehydroxylation is reversible below 400°C, and not reversible above 400°C; the higher the pretreatment temperatures, the less the degree of rehydroxylation. After obtaining the first desorption isotherm, the second desorption one was measured on the rehydroxylated surface. The physisorbed water at monolayer coverage was estimated by applying the BET equation to the second desorption isotherm. The relationship between physisorbed water and the underlying hydroxyl group was examined.

The preparation and evaluation of superior bonded phases for reversed-phase, high-performance liquid chromatography

Abstract: The preparation of efficient chemically bonded phases based upon interaction of silica gel with trichlorosilanes is reported. Chlorinated solvents are found to yield superior products whilst reaction at elevated temperatures is shown to be unnecessary. A new capping procedure, involving methanolysis and subsequent reaction with trimethylchlorosilane, is shown to be more effective than existing procedures.

Technique for In Situ Coating of Ag+ Onto Silica Gel in HPLC Columns for the Separation of Geometrical Isomers

Abstract: A method is described for the in situ coating of silver nitrate onto silica gel in high performance liquid chromatography columns. The columns effectively separated a series of geometrical isomers.

Room temperature phosphorescene of nitrogen heterocycles adsorbed on silica gel

Abstract: The room temperature phosphorescence (RTP) of benzo(f)-quinoline adsorbed on several silica gel samples was investigated by luminescence, reflectance, and infrared spectroscopy to obtain a better understanding of the analytical conditions needed for strong RTP. The results showed that silica gel chromatoplates containing a polymeric binder with carboxyl groups were the best samples for inducing strong RTP from benzo(f)quinoline. The polymer itself was essential for inducing strong RTP. It was postulated that benzo(f)quinoline was adsorbed flatly on the surface with the carboxyl groups anchoring benzo(f)quinoline via hydrogen bonding with ..pi.. electrons. 5 figures, 4 tables.

Method for producing silica glass

Abstract: A method for producing silica glass wherein a dry silica gel subjected to a water desorption treatment and a carbon removal treatment is heated and has its temperature raised in an atmosphere containing chlorine, to perform a hydroxyl group removal treatment, the resultant silica gel is thereafter heated to a temperature of approximately 1,000° C.-1,100° C. in an atmosphere containing at least 1% of oxygen, to perform a chlorine removal treatment, and the resultant silica gel is further heated to a temperature of 1,050° C.-1,300° C. in He or in vacuum, to perform a sintering treatment. The silica glass thus produced does not form bubbles even when heated to high temperatures of or above 1,300° C. Therefore, it is easily worked and it is free from the lowering of transparency attributed to the bubble formation.

Fractionation of triglyceride mixtures

Abstract: Triglyceride mixture is fractionated (on the basis of Iodine Value) utilizing selected surface aluminated silica gel adsorbent and selected solvent(s).

Polymerization catalyst and process

Abstract: An olefin polymerization catalyst is provided comprising chromium oxide on a titanium-containing silica support having at least about 3 weight percent titanium in combination with an organoboron promoter. The titanium may be incorporated by coprecipitation with the silica gel or added anhydrously or nonanhydrously to the silica gel. The polymerization process comprises the contacting of olefin monomer with the titanium-containing chromium oxide catalyst in the presence of an organoboron promoter.

Thermally regenerative desiccant element

Abstract: A thermally regenerative desiccant element comprising micron size silica gel and held within an expanded web of a fluoroplastic elastomer is disclosed The expanded web of silica gel is bonded onto a heat conductive plate to form the desiccant element The desiccant elements are stacked in an arrangement such that the air to be processed passes in contact with the silica gel The other side of the plate is made to come in contact with a stream of humidified cooled air The cooled air removes the heat of sorption when the silica gel sorbs moisture A solar collector is used to heat ambient air for regeneration of the silica gel

Gangliosides from rat cerebellum: Demonstration of considerable heterogeneity using a new solvent for thin layer chromatography

Abstract: Using a new solvent (methyl acetate/n-propanol/chloroform/methanol/0.25% aqueous KCl, 25∶20∶20∶20∶17, v/v) and high performance silica gel thin layer chromatographic plates, all common gangliosides found in brain can be easily separated with 1 hr. This system is reproducible and “tailing” is negligible compared with previous solvents. When such a system is applied to separate the gangliosides found during the development of the rat cerebellum, a considerable heterogeneity is observed. Data are presented (using rechromatography experiments, fractionation on DEAE-Sephadex, treatment with neuraminidase or alkaline medium and carbohydrate analysis) suggesting that the complex profiles obtained with this chromatographic system are not due to chromatographic artifacts but result from the high resolving power of the system. After separation by ion-exchange chromatography, 28 gangliosides can be detected.