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Showing papers on "Silica gel published in 1979"


Book ChapterDOI
TL;DR: Results indicated that reverse-phase chromatography of a triester oligonucleotide could yield a pure product at each step of synthesis.
Abstract: Publisher Summary This chapter discusses an experimental study focusing on the improved phosphotriester method for the synthesis of gene fragments During studies with a modified triester approach, it was observed that the pure, fully protected product was difficult to separate quantitatively by the conventional silica gel chromatography from the crude reaction mixture, especially from the components containing several guanine bases It was found that thin-layer chromatography (TLC) on silanized silica gel (RP-2) and KC 18 (RP-18) plates in an acetone–water solvent gave excellent separation of the components containing trityl and hydroxyl groups and also of those differing in sizes The polar component (containing 3′ phosphodiester) generally moved to the solvent front, and the fully protected component (containing the trityl group) was the slowest The mobility of a component containing a 5′-hydroxyl group was between that of the polar and nonpolar compounds The purification of GGCA could not be achieved on silica gel as determined after complete deblocking and TLC on a polyethyleneimine (PEI), whereas purification by TLC on reverse-phase (RP-2) plates gave pure GGCA as analyzed on a PEI plate These results indicated that reverse-phase chromatography of a triester oligonucleotide could yield a pure product at each step of synthesis

214 citations


Journal ArticleDOI
TL;DR: In this article, a fracture-free monolithic silica glass was successfully prepared from a dry silica gel formed by the hydrolysis of silicon methoxide by careful heat-treatment.
Abstract: The reaction process in the pyrolysis of silica gel has been investigated as the basic study on the low temperature synthesis of monolithic glass from a metal alkoxide. A large volume change which may cause stress-induced fracture of a gel occurred in the following process stages: (a) the decompostion of residual organic compounds into carbon dioxide (300 to 500° C); (b) small pore collapse (400 to 500° C); (c) larger pore collapse (700 to 900° C). A fracture-free monolithic silica glass was successfully prepared from a dry silica gel formed by the hydrolysis of silicon methoxide by careful heat-treatment. The properties of the synthetic silica glass were similar to those of commercial vitreous silica.

138 citations


Journal ArticleDOI
TL;DR: In this article, a high-performance liquid chromatography with microparticulate silica gel and octadecyl silica reversed-phase columns accords ready resolution of the common autoxidation products of cholesterol.

92 citations



Journal ArticleDOI
TL;DR: This thin-layer chromatography method was used to separate pathological oligosaccharides isolated from individuals with G M1 gangliosidosis and with neuraminidase deficiency, indicating the potential usefulness of the system in the analysis of complex carbohydrates.

87 citations


Journal ArticleDOI
TL;DR: In this article, the results suggested that chromic acid forms binuclear surface complexes on the silica which become stabilized during calcination, and two or threedimensional clusters formed on Type 1 catalysts and chromium pairs or two-dimensional clusters form on Type 2 catalyst.

87 citations


Journal ArticleDOI
TL;DR: In this paper, the carbonation of wetted powders of β-dicalcium silicate (β·2CaO·SiO2=β-C2S) and tricalcium (3CaO•SiO•2=C3S) was studied as a function of reaction conditions.
Abstract: The carbonation of wetted powders of beta-dicalcium silicate (β·2CaO·SiO2=β-C2S) and tricalcium silicate (3CaO·SiO2= C3S) was studied as a function of reaction conditions. The water/solids ratio is an important parameter and there is an optimum value for each silicate. Relative humidity and the partial pressure of CO2 also strongly affect the reaction. The rate of carbonation can be conveniently represented by plotting the degree of carbonation against the logarithm of time. C-S-H and calcite are the initial reaction products. Subsequently, carbonation of the C-S-H produces silica gel, whereas aragonite may form if the system is allowed to dry out.

79 citations


Journal ArticleDOI
TL;DR: In this article, a method for the synthesis of a bonded phase that consists in attaching l -proline to triethoxypropylaminosilane and then bonding the final product to the silica gel microparticles was developed.

76 citations


Patent
20 Nov 1979
TL;DR: Porous carbon is a polymerizable organic material that is polymerized in situ in the template pores and then pyrolyzed to carbon as mentioned in this paper, suitable for instance for chromatography and as a catalyst support is formed by depositing carbon into the pores of a porous inorganic template.
Abstract: Porous carbon, suitable for instance for chromatography and as a catalyst support is formed by depositing carbon into the pores of a porous inorganic template such as silica gel, porous glass or a porous oxide, e.g. alumina, and thereafter removing the template as by dissolution or evaporation. Carbon is preferably deposited as a polymerizable organic material that is polymerized in situ in the template pores and then pyrolyzed to carbon.

74 citations


Journal ArticleDOI
TL;DR: Pyridinium chromate-on-silica gel and chromic acid on silica gel have been evaluated and evaluated as convenient off-the-shelf reagents for efficient oxidation of a variety of secondary and primary alcohols as discussed by the authors.

70 citations


Journal ArticleDOI
TL;DR: In this paper, a phosphoroscope and reflection assembly for a spectrodensitometer is described, which is employed to obtain room temperature phosphorescence (RTP) data from several nitrogen heterocycles adsorbed on dried silica gel and filter paper.
Abstract: A phosphoroscope and reflection assembly for a spectrodensitometer is described. They were employed to obtain room temperature phosphorescence (RTP) data from several nitrogen heterocycles adsorbed on dried silica gel and filter paper. The effects of acid and different gases on the RTP of these compounds adsorbed on silica gel and filter paper is discussed. Also, the analytical potential of this new approach is considered. 5 figures, 3 tables.

Journal ArticleDOI
TL;DR: In this article, a chiral stationary phase for the direct resolution of optical isomers in liquid chromatography was developed, involving less specific and milder diastereomeric association with the solute molecule than with previously known phases.

Journal ArticleDOI
TL;DR: Alcohols including prostaglandins, geraniol, and carbohydrate, can easily be methylated with diazomethane in the presence of silica gel as mentioned in this paper, and the results show that the mixture can be used to synthesize new drugs.

Journal ArticleDOI
TL;DR: The relative merits of eight procedures for preconcentrations of trace metal ions from natural water samples and synthetic solutions are evaluated in this paper, where the quantitative characteristics of these techniques and the influence of the water matrix effects are discussed, as well as the applicability for x-ray fluorescence analysis.

Patent
09 May 1979
TL;DR: A colony-stimulating factor having definite physical and chemical properties and a function of stimulating activity on human bone marrow cells to proliferate and differentiate, thereby forming granulocyte colonies, is obtained from human urine by concentrating the urine with respect to proteins contained therein by adsorption chromatography with silica gel, salting out with ammonium sulfate and other means, then removing impurities by adaption on cation exchanger and further purifying by ion exchanging chromatography on anion exchanger, further purification by ion exchange chromatography by gel filtrating
Abstract: A colony-stimulating factor having definite physical and chemical properties and a function of stimulating activity on human bone marrow cells to proliferate and differentiate, thereby forming granulocyte colonies, is obtained from human urine by concentrating the urine with respect to proteins contained therein by adsorption chromatography with silica gel, salting out with ammonium sulfate and other means, then removing impurities by adsorption on cation exchanger, and further purifying by ion exchanging chromatography on anion exchanger, gel filtrating chromatography with highly crosslinked gels, affinity chromatography with sugar affinitive adsorbents and electrophoresis. This substance is stable in the presence of a stabilizer such as albumin or urinary proteins, against heat-treatment of virus-inactivation and can be used as a leukopenia curative which is precluded from fear of virus-infection.

Journal ArticleDOI
TL;DR: A silica aerogel was prepared by hydrolysis of tetramethylsilane in methanol and evacuated; it was used with the resulting O-CH/sub 3/ surface groups or after calcination to convert these groups into OH groups as mentioned in this paper.

MonographDOI
02 Mar 1979
TL;DR: Walker et al. as mentioned in this paper used electron micrographs of fracture surfaces of Berea sandstone and representative reservoir cores to reveal that the rock surface is quite heterogeneous as to geometry and mineralogy.
Abstract: Scanning electron micrographs of fracture surfaces of Berea sandstone and representative reservoir cores reveal that the rock surface is quite heterogeneous as to geometry and mineralogy. Clay and other minor constituents cover much of the sand rather than being concentrated in cementation bridges, thus insuring intimate contact with the micellar fluid. Alkylbenzene sulfonates in dilute aqueous solution are very susceptible to salting-out by NaCl, especially if the alkyl chain contains more than 12 carbons. Cation exchange capacity measurements show that the CEC of Berea sandstone can be attributed to its clay fraction and that injection of 1N NaCl into crushed Berea sandstone generates a calcium ion wave about one pore volume wide with a peak concentration near 1500 ppm. Measurements of the calcium tolerance of several sulfonates indicate that precipitation of sulfonate begins at low calcium concentrations (200 ppm to < 10 ppm depending on sulfonate equivalent weight), and that the onset of precipitation is P ub lic at io n D at e: M ar ch 2 , 1 97 9 | d oi : 1 0. 10 21 /b k19 79 -0 09 1. ch 00 1 In Chemistry of Oil Recovery; Johansen, R., el al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1979. 1. WALKER ET AL. Micellar Flooding 15 not materially affected by added butanol or by sulfonate concen­ tration. Negligible surfactant adsorption is found on sand, but it is appreciable on silica gel. The isotherm on silica gel has a concave toe and becomes constant near the CMC at a level which decreases with increasing NaCl concentration. Sulfonate adsorp­ tion on clay is quite different: adsorption maxima are observed and adsorption is increased by NaCl. Adsorbate association (hemimicelle formation) is observed on both silica gel and clay, and some evidence for dimer adsorption is found. Both salting-out and multivalent cation precipitation complicate adsorption measure­ ments.

Patent
19 Mar 1979
TL;DR: A colony-stimulating factor having definite physical and chemical properties and a function of stimulating activity on human bone marrow cells to proliferate and differentiate, thereby forming granulocyte colonies, is obtained from human urine by concentrating the urine with respect to proteins contained therein by adsorption chromatography with silica gel, salting out with ammonium sulfate and other means, then removing impurities by adaption on cation exchanger and further purifying by ion exchanging chromatography on anion exchanger, gel filtrating chromatography, affinitive and affin
Abstract: A colony-stimulating factor having definite physical and chemical properties and a function of stimulating activity on human bone marrow cells to proliferate and differentiate, thereby forming granulocyte colonies, is obtained from human urine by concentrating the urine with respect to proteins contained therein by adsorption chromatography with silica gel, salting out with ammonium sulfate and other means, then removing impurities by adsorption on cation exchanger, and further purifying by ion exchanging chromatography on anion exchanger, gel filtrating chromatography with highly crosslinked gels, affinitive chromatography with sugar affinitire adsorbents and electrophoresis.

Journal ArticleDOI
TL;DR: In this article, a thin-layer chromatographic (TLC) system for determining simultaneously up to eleven carbohydrates commonly found in food chemistry is described, and the TLC plates are developed three times in the same direction with a mixture of acetonitrile and water before dipping them in a solution containing diphenylamine.

Journal ArticleDOI
TL;DR: A straight-phase adsorption system consisting of Si 60 silica gel as the stationary phase and mixtures of n-hexane and dioxane as mobile phases were employed, using photometric detection at either 320 or 360 nm, depending on the nature of the compounds being studied.

Journal ArticleDOI
TL;DR: GM2 and GA2 gangliosides from the brain of a patient who died of Sandhoff's disease were tritiated in the terminal N-acetylgalactosamine residue using galactose oxidase and sodium [3H]borohydride with the inclusion of catalase and peroxidase into the oxidation reaction.

01 Jan 1979
TL;DR: In this paper, the use of gel permeation chromatography followed by high resolution gas chromatography-mass spectrometry for the separation and characterization of coal derived liquids is discussed, which can be used to separate molecules over a wide range of molecular size, several million to less than 100 molecular weight.
Abstract: Characterization and estimation of components in coal derived products are always time consuming and complex due to the number of various constituents present in them. Most of the people working in this area try to separate coal derived mixtures into four or five fractions and each fraction is enriched with chemically similar species. The fractionation is achieved by either using the difference in the solubility of various components in solvents with different chemical affinities or using absorption chromatography, mainly silica gel columns or various ion exchange and ionpair columns. The latter achieves a cleaner separation than the former. The major disadvantage of both techniques is the loss of material balance at the end of the separation and the time consuming steps involved. This paper discusses the use of gel permeation chromatography followed by high resolution gas chromatography-mass spectrometry for the separation and characterization of coal derived liquids. Gel Permeation Chromatography uses columns packed with swelled polymer particles with controlled pore size, formed by the copolymerization of styrene and divinlybenzene GPC separates molecules according to molecular size based upon a distribution between a stationary phase of controlled pore size distribution and mobile liquid phase. Larger molecules elute faster than smaller moleculesmore » since larger molecules are less probable to diffuse into the liquid trapped inside the pore. Selecting the columns with proper pore size which varies from 100A to 10/sup 6/A, the technique can be used to separate molecules over a wide range of molecular size, several million to less than 100 molecular weight.« less

Journal ArticleDOI
TL;DR: In this paper, the dispersion of polymers eluted in the exclusion mode from columns of Hypersil and SG60F (a highly porous silica gel) has been measured for a range of polymer standards over different elution velocities and columns of different lengths.

Journal ArticleDOI
TL;DR: A simple and rapid procedure for the separation and determination of a number of polycyclic aromatic hydrocarbons (PAHs) in environmental dust samples is described in this paper, where an ultrasonic extraction method was used to separate the organic compounds from the dust particles.

Journal ArticleDOI
TL;DR: In this paper, the capacity factors of nickel-II biddialkyl-dithiocarbamate (DTC) complexes were investigated using high-performance liquid-solid chromatography.

Journal ArticleDOI
TL;DR: In this paper, a rapid quantitative separation of photosynthetic intermediates in spinach chloroplasts is obtained on chemically modified, totally porous, silica gel resins (10 μm).

Journal ArticleDOI
TL;DR: The procedure is shown to be sensitive, linear, reproducible and to compare well with conventional methods for the determination of plasma lipid classes.

Journal ArticleDOI
TL;DR: Gel permeation chromatography (GPC) of polyelectrolytes in dimethylformamide (DMF) is studied in this article, where three methods of monitoring elution are used to investigate the molecular-weight distribution and the chemical composition expressed in terms of the ionic charge density as a function of the chain length in two copolymers of acrylonitrile and sodium methallylsulfonate.
Abstract: Gel permeation chromatography (GPC) of polyelectrolytes in dimethylformamide (DMF) is studied. Three methods of monitoring elution (conductimetry, viscosimetry, refractometry) are used to investigate the molecular-weight distribution and, independently, the chemical composition expressed in terms of the ionic charge density as a function of the chain length in two copolymers of acrylonitrile and sodium methallylsulfonate. The distribution on the gel of the neutral salt NaNO3 added to the DMF and used for elution is discussed in terms of Donnan exclusion; in addition, it is concluded that to obtain the correct molecular-weight distribution, GPC measurements must be performed with an eluent containing a neutral salt at a concentration at least 5 × 10−2M to prevent electrostatic exclusion. The main difficulty in reaching rigorous conclusions comes from the dependence of the calibration curve on the salt composition of the eluent owing to interactions—dependent on the quality of the solvent—between the polystyrenes used as standards and the porous silica gel. Nevertheless, this perturbation is small and the agreement between the average molecular weights obtained by GPC and by direct determination is good and indicates that the universal calibration proposed for neutral polymers is also valid for polyelectrolytes.

Journal ArticleDOI
TL;DR: A method for separating individual monosulfated primary bile acid conjugates by reversed-phase partition thin-layer chromatography on octadecyl-bonded silica gel is described.

Journal ArticleDOI
TL;DR: In this article, the properties of silica gel were studied as a function of the hydrothermal treatment of hydrogel by means of the nitrogen-adsorption isotherm, the mechanical strength, thermodilatometry, and infrared spectroscopy.
Abstract: The properties of silica gel were studied as a function of the hydrothermal treatment of hydrogel by means of the nitrogen-adsorption isotherm, the mechanical strength, thermodilatometry, and infrared spectroscopy. As a result, the number of contact points between primary particles of silica was found to decrease, and closed pores were found to be produced, by this treatment. The analysis of the infrared absorption spectra of the OH groups of this material showed that there are three kinds of OH groups in silica gel; (1) free OH groups on the outer surface of primary particles, which can adsorb molecules easily, (2) weakly perturbed OH groups inside closed pores, and (3) strongly hydrogen-bonded OH groups on the surface around the contact points. The relative concentration of these OH groups changes drastically upon the hydrothermal treatment; this is in accord with the change in the macroscopic properties mentioned above.