Showing papers on "Silica gel published in 1977"
TL;DR: Although many of the C-3 substituted indoles such as indole-3-acetic acid and tryptamine had colors in the reddish-violet-blue color region, most exhibited sufficient color differentiation to allow their identification by thin-layer chromatography.
341 citations
Journal Article•
TL;DR: In this article, the solubility of amorphous silica in water at high temperatures and high pressures was investigated, using commercial gel and vitreous silicon (fused quartz) as starting materials.
Abstract: The solubility of amorphous silica in water at high temperatures and high pressures was investigated, using commercial gel and vitreous silica (fused quartz) as starting materials. The experiments were carried out in an Inconel X bomb at temperatures from 180 to 382/sup 0/C and pressures from 200 to 1379 bars. Periodically, small amounts of solution were withdrawn from the bottom of the bomb through a stainless steel filter into high-pressure stainless steel capillary sampling line, quenched in an ice bath, and immediately diluted with previously weighed silica-free water. The diluted samples were analyzed for colorimetrically-reactive and total silica. The silica gel gave the same colorimetric silica as the vitreous silica. The solubility of amorphous silica at the vapor pressure of the solution, from 0 to 250/sup 0/C, is given by the equation log C = -731/T + 4.52, where C is the silica concentration in mg/kg and T is absolute temperature. The maximum solubility at the vapor pressure of solution is 1660 mg/kg at 340/sup 0/C, and the extrapolated solubility at the critical point is 890 mg/kg. At a constant pressure of 1034 bars, the solubility of amorphous silica from 0 to 380/sup 0/C is given by the equation logmore » C = -810T + 4.82. The differential heat of solution, ..delta..H, is 3.71 +- 0.05 kcal/mole, and the differential entropy of solution, ..delta.. anti S, is 13.9 +- 0.05 cal/mole.« less
225 citations
TL;DR: A quantitative high performance liquid chromatography method for the analysis of neutral glycosylceramides as their perbenzoyl derivatives has been devised and has been applied to the quantitative analysis of erythrocyte and plasma glycolipids.
154 citations
TL;DR: In this paper, densification rates for three classes of porous glass materials are reported for soot preforms made by flame hydrolysis, silica gel, and phase-separated and leached borosilicate glass.
Abstract: Densification rates are reported for 3 classes of porous glass materials: soot preforms made by flame hydrolysis, silica gel, and phase-separated and leached borosilicate glass. Viscosity values obtained by fitting the densification data to the theory of Part I of the present study are in reasonable agreement with viscosity measured by beam bending using fully sintered glass of the same type.
103 citations
TL;DR: In this article, a linear relationship between the capacity ratios k′ and the amount of carbon was found in all cases, and the improved properties were discussed in relation to residual silanol groups on the adsorbent surface.
Abstract: Bonded hydrocarbon phases were prepared by the reaction of alkylmethyldichlorosilanes to silica (Lichrosorb Si 100, 10 μm Merck). Alkyl phases, CH3 (CH2)n (CH3)Si= with n=7, 10, 14 and 17 were investigated and compared with materials obtained by the reaction of alkyltrichlorosilanes. In reversed phase chromatography using water-methanol as mobile phase a linear relationship between the capacity ratios k′ and the amount of carbon was found in all cases. All alkylmethyl phases proved to be superior to the alkyl phases. Capacity ratios and selectivities are increased and the efficiencies, with one exception, are higher. The improved properties are discussed in relation to residual silanol groups on the adsorbent surface.
87 citations
TL;DR: In this article, high performance liquid chromatographic separations of chelates at nanogram levels by adsorption chromatography on silica gel are reported. 1,2-Diketobisthiobenzhydrazones, dialkyldithiocarbamates and 1, 2-diketabisthiosemicarbazones were used as chelate-forming ligands.
80 citations
TL;DR: Results by this method correlate well with a competitive protein-binding assay (r = 0.961), but with a negative bias of 6.9 +/- 3.3 microgram/liter.
Abstract: We describe a precise and specific method for measuring 25-hydroxyvitamin D3 in 1 ml of human serum. Extraction with chloroform/methanol followed by chromatography on a 0.5 X 2-cm silica gel column yields a sample that is sufficiently free of extraneous material for high-performance liquid chromatography on a column of microporous silica gel (10 micron average particle diameter). The measurement is not influenced by vitamins D2 or D3, 25-hydroxyvitamin D2, or any of the more hydroxylated metabolites of the vitamin D group. Results by this method correlate well with a competitive protein-binding assay (r = 0.961), but with a negative bias of 6.9 +/- 3.3 microgram/liter. We measured concentrations of 25-hydroxyvitamin D3 in serum drawn during February from 24 persons who were judged normal by physical examinations. The range was 5.5-23.8 microgram/liter (mean, 15.0 +/- 5.2 microgram/liter). The day-to-day CV for the assay was 5.46%.
66 citations
TL;DR: In this paper, small Au-Pd particles 2.0 to 4.5 nm in diameter were prepared by ion exchange of [Au(en) 2 ] 3+ and [Pd(NH 3 ) 4 ] 2+ with surface protons of silica gel to form a precursor, which was subsequently reduced in dihydrogen.
51 citations
TL;DR: In this paper, the separation and determination of the 4-nitrobenzoates of some monosaccharides, disaccharide, and trisaccharided by high-performance liquid chromatography is described.
50 citations
TL;DR: Th Thin layer chromatography (TLC) and selective solvent extraction demonstrated that the products of the reaction contained many substances with a fluorescent spectrum similar to those of lipofuscin pigments, illustrating that fluorescent substances were formed in a variety of reactions associated with the oxidation of unsaturated lipids.
Abstract: The formation of fluorescent products in the reaction of methyl linoleate hydroperoxide with glycine in aqueous emulsions correlated directly with the decrease in diene conjugation and the increase in thiobarbituric acid (TBA) reactive substances. These correlations also were reflected in the course of the oxidation of methyl linoleate in aqueous emulsions with glycine and indicated that glycine reacted with products of peroxide decomposition as opposed to intermediates of autoxidation in hydroperoxide formation. Thin layer chromatography (TLC) and selective solvent extraction demonstrated that the products of the reaction contained many substances with a fluorescent spectrum similar to those of lipofuscin pigments. When methyl esters of polyunsaturated fatty acids or other polyunsaturated lipids underwent oxidation adsorbed on silica gel particles, products with similar fluorescent spectral properties were formed illustrating that fluorescent substances were formed in a variety of reactions associated with the oxidation of unsaturated lipids.
45 citations
Patent•
06 Oct 1977
TL;DR: In this article, a cross-linked polymer was used to cover the surface of the fine holes of the porous silica gel particles in an amount of 5 to 50 wt.% of the polymer to the particles, wherein said crosslinked polymer does not contain any extractable polymer.
Abstract: In an apparatus for liquid chromatography the improvement which comprises a chromatographic column packed with a solid packing material comprising porous silica gel particles, having a specific surface area of 5 to 1500 m 2 /g, an average pore diameter of 20 to 2000 A and a crosslinked polymer selected from the group consisting of polystyrene, sulfonated polystyrene, polymethyl methacrylate and polyacrylonitrile coating the surface of the fine holes of the porous silica gel particles in an amount of 5 to 50 wt.% of the polymer to silica gel particles, wherein said crosslinked polymer does not contain any extractable polymer.
TL;DR: A competitive protein binding assay for serum 25-hydroxyvitamin D is described in which normal human serum is used as the source of binding protein and it is concluded that chromatography with either silica gel or LH20 is essential.
TL;DR: It is shown that these separations are superior to those possible on silica gel, although the efficiencies of the column are low, and the implications and future for the use of bonded opitcally active peptides as stationary phases for liquid chromatography are discussed.
TL;DR: In this paper, a metalloborane, 2-(eta(5)-C5H5)FeB5H10 (I), was prepared in the reaction of FeCl2, Na(+)C5h5(-), and Na(+B5h8(-) in tetrahydrofuran at 25 and isolated as violet crystals via silica gel chromatography.
Abstract: : A new metalloborane, 2-(eta(5)-C5H5)FeB5H10 (I), was prepared in the reaction of FeCl2, Na(+)C5H5(-), and Na(+)B5H8(-) in tetrahydrofuran at 25 and isolated as violet crystals via silica gel chromatography.
Patent•
18 Nov 1977TL;DR: In this article, the use of silica gels having a water content of 15 to 35 percent as polishing agents in dentifrice formulations was proposed for use in dentificrice formulations.
Abstract: This invention relates to polishing agents for use in dentifrice formulations. More particularly, this invention relates to the use of silica gels having a water content of 15 to 35 percent as polishing agents in dentifrice formulations.
TL;DR: In this paper, high performance liquid chromatographic separations of Pb, Zn, Cd, Hg, Cu, Ni, and Co(II) dithizonates are reported.
TL;DR: In this paper, the preparation and characteristics of 2-mercaptobenzothiazole supported on silica gel (MBT-SG), and its application to the preconcentration and determination of cadmium, copper, lead, and zinc in natural water samples are described.
Abstract: The preparation and characteristics of 2-mercaptobenzothiazole supported on silica gel (MBT–SG), and its application to the preconcentration and determination of cadmium, copper, lead, and zinc in natural water samples are described. The MBT–SG was prepared by impregnating silica gel with MBT in a dioxane–methyl acetate solvent mixture, drying, washing with deionized water, and finally drying. The chelating capacity of the material was 0.01 meq. Cu/g. Cadmium, copper, lead, and zinc were quantitatively retained on the MBT–SG at pH values of 4.8, 2.5, 4.8, and 6.5 for an aqueous solution, and at pH values of 4.8, 2.8, 4.8, and 6.5 for sea water. A column made of the material provided quantitative recovery of these metals from natural water samples at higher flow rates (2–5 1/h) than other chelating resins, e. g., chelex 100. Cadmium was eluted with hydrochloric acid (1 : 99), copper and lead with acetone–hydrochloric acid mixture (9 : 1), and zinc with an acetate–hydrochloric acid buffer solution (pH 4.0)....
TL;DR: In this paper, the authors investigated the influence of surface modification of silica gel on their adsorption behavior and proposed a new term "architecture of adorption centers" to describe the surface properties and structure of chemically modified adsorbents.
TL;DR: In this article, a phase transfer catalysts such as phosphonium salts immobilized on silica gel showed catalytic activity for anion-promoted reactions both in liquid-liquid and solid-liquid systems.
Abstract: Heterogeneous phase-transfer catalysts such as phosphonium salts immobilized on silica gel show catalytic activity for anion-promoted reactions both in liquid–liquid and solid–liquid systems; kinetic measurements show the influence of the polar silica support.
TL;DR: In this paper, the use of a stop-start liquid chromatograph is described in which the UV spectra of peaks can be scanned during chromatography for identification purposes, and a new form of thin-layer chromatography which incorporates the organo-clay Bentone 34 has been shown to be selective for PAH.
TL;DR: There were no differences in the recoveries of ganglioside sialic acid from silica gel G thin-layer chromatograms when they were sprayed with resorcinol reagent varying in normality between 3 and 10, but both the temperature at and the time for which the plates were heated after spraying did affect the recovers.
TL;DR: In this paper, the adsorption method for determination of the distribution of neptunium among its oxidation states at tracer concentrations by use of silica gel and barium sulfate as adsorbents is described.
TL;DR: In this article, it was shown that when silica gel is treated in hydrogen at about 800 °C in the presence of a metal but without physical contact with it, reduction of siloxane bridges into SiH groups occurs.
TL;DR: An analytical method is described for determining residues of the synthetic estrogen diethylstilbestrol (DES) in animal chow at levels as low as 1 ppb by high-speed liquid chromatography or derivatized to pentafluoropropionyl-DES and assayed by electron-capture gas chromatography.
Abstract: An analytical method is described for determining residues of the synthetic estrogen diethylstilbestrol (DES) in animal chow at levels as low as 1 ppb. A methanol extract of the chow is subjected to a 3-step cleanup procedure including a Sephadex LH-20 column, liquid-liquid partitioning at pH 14 and 10.2, and a silica gel column. Residues of DES in the cleaned-up extract are analyzed directly by high-speed liquid chromatography or derivatized to pentafluoropropionyl-DES and assayed by electron-capture gas chromatography. Tests with 14C-DES were used to develop and validate the procedure. Ancillary data concerning extraction efficiencies of various solvents, comparisons of various derivatizing reagents, rates of trans-cis isomerization in two solvents, P-values of DES in various solvent-systems and thin-layer chromatographic behavior i
TL;DR: The speed and efficiency of resolution of these relatively sensitive compounds by HPLC demonstrates the potential utility of this technique for resolution of all types of carcinogen-derived arene dihydrodiols.
TL;DR: In contrast to their unsupported analogues, no bi-nuclear or polynuclear species are formed from the SiO 2 -supported metal carbonyl derivatives even at temperatures up to 200°C as discussed by the authors.