Showing papers on "Silica gel published in 1972"
261 citations
126 citations
TL;DR: The Bureau of Mines developed a chromatographic separation procedure using a single dual-packed adsorption column containing silica gel and alumina that will separate high-boiling petroleum distillates into four concentrates as discussed by the authors.
Abstract: The Bureau of Mines has developed a chromatographic separation procedure using a single dual-packed adsorption column containing silica gel and alumina that will separate high-boiling petroleum distillates into four concentrates: saturates, monoaromatics, diaromatics, and polyaromatics-polar. Spectral, adsorption, and radiotracer data indicate that the concentrates produced are predominantly as labeled. Subdividing the aromatics into major aromatic types greatly simplifies subsequent separation and characterization studies.
117 citations
TL;DR: The elution of 33 GAs and abscisic acid from a gradient eluted (increasing amounts of ethyl acetate in hexane) silica gel partition column are given in this article.
100 citations
TL;DR: In this paper, a qualitative analysis of the oleoresins from ginger and grains of paradise was performed using thin-layer (silica gel) and gas chromatography (SE-30 and VO-17 liquid phases) and reference retention times and RF values reported.
74 citations
TL;DR: Methods for the chromatography of the very labile 2-hydroxyestradiol-17β on paper, thin layers and columns without oxidative decomposition are described, showing that amounts as small a 2 μg are easily and quantitatively recovered when using these new reducing chromatographic systems.
67 citations
TL;DR: In this article, the growth of brushite is simulated by growing brushite crystals on the surface of teeth suspended in phosphate solutions, and the growth morphology is observed as influenced by temperature and presence of other ions (such as F−, CO32− P2O74−, Sr2+, Mg2+).
61 citations
TL;DR: This method has a great deal of potential in achieving complete separations of naturally occurring marine or other sterol mixtures or in combination with preparative GLC in those cases where an enrichment only has been achieved.
44 citations
TL;DR: In this paper, the autoxidation of monolayers of linoleic acid adsorbed from solution onto silica gel has been studied as a function of time and α-tocopherol and acid synergist content.
Abstract: To approximate in a model system the autoxidation of monomolecular layers of lipids on the cell surfaces of freeze-dried foods, the autoxidation of presumed monolayers of linoleic acid adsorbed from solution onto silica gel has been studied as a function of time and α-tocopherol and acid synergist content The method of Honn, Bezman and Daubert was used, modified by the substitution of linoleic acid for soybean oil and the use of gas chromatography to follow oxygen disappearance at 80 C It was found that adsorption of linoleic acid onto silica gel from petroleum ether solution conforms to a Langmuir isotherm, consistent with the formation of a monolayer Confirming the finding of Honn et al with soybean oil, it was found that the most rapid uptake of oxygen occurred at a linoleic acid-silica ratio close to that for the monolayer Without included antioxidant, oxidation commences at a nearly linear rate without observable induction period Time for consumption of one-half mole of oxygen per mole of linoleic acid is ca 60 min on acid-washed silica If very small amounts of α-tocopherol are included in the layer, virtually no oxygen uptake measurable in this system occurs during an induction period, the length of which is approximately proportional to tocopherol content The inflection point at the commencement of rapid oxidation is very sharp; the ensuing oxidation rate approximates that of the unprotected acid The induction period of linoleic acid with the same tocopherol content is as much as 100% longer when exposed in monolayer than in a bulk form However the rate after commencement of rapid oxidation is 8–10 times greater in the monolayer Acid washing of the silica reduced its iron content by 75% Acid washing also reduced by 60% the rate of autoxidation without α-tocopherol and increased the length of the induction period four-fold when α-tocopherol was present The effect of pretreatment of the silica by adsorption of the acid synergists, ascorbic, phosphoric, citric and ethylenediamine tetraacetic acid was qualitatively similar to the effect of acid washing The synergists extended the induction period in increasing order as listed, EDTA producing a 100-fold extension For ascorbic acid the rate reduction and increase of induction period were not found on unwashed silica and were dependent on the extent of washing These findings are consistent with synergist sequestration of metals in a complex that is ineffective in new chain generation by perioxide decomposition
35 citations
TL;DR: The rate of disappearance of B1 or G1 at given temperature and at constant pH was found to be first order with respect to each aflatoxin, indicating first order dependent of the rate on H+ ion concentration.
Abstract: Adjusting dilute aqueous solutions of aflatoxins B1 and G1 to pH 1, 2 and 3, and heating over a range of 40–100 C resulted in the conversion of B1 to B2a and G1 to G2a as major products. Both B2a and G2a were identified by co-thin layer chromatography with authentic B2a and G2a and M1 on silica gel plates developed in two different solvents. The rate of disappearance of B1 or G1 at given temperature and at constant pH was found to be first order with respect to each aflatoxin. At given temperature the conversion is strongly pH dependent, a 10-fold increase in H+ ion (1 pH unit) producing about a 9-fold increase in the reaction rate, indicating first order dependent of the rate on H+ ion concentration.
31 citations
Patent•
10 Nov 1972
TL;DR: In this paper, a method for activating red mud formed in the Bayer alumina producing process for allowing its use as adsorbent, catalyst, ion-exchanging substance and clarifying substance, comprising a digesting red mud and dispersing the metal oxide compound particles in the compound of metal hydroxides and silica gel.
Abstract: A method for activating the red mud formed in the Bayer alumina producing process for allowing its use as adsorbent, catalyst, ion-exchanging substance and clarifying substance, comprising a digesting red mud and dispersing the metal oxide compound particles in the compound of metal hydroxides and silica gel. The method comprises digesting red mud with acid, before adjusting the pH of the acid digested mixture comprising the sludge product to above 4 to disperse oxide compound in the compound the metal hydroxides and silica gel, and removing the residue acid employed from the gelating product with washing, then with or without shaping treating, and heat treating the product to provide a active red mud, particularly with respect to the catalytic cracking, decolorization of hydrocarbon, clarification of waste gas and adsorption processes.
TL;DR: In this article, it was shown that formaldehyde exists as a monomer (form A) in nonpolar solvents to a temperature of approximately −95°C, and formation of a formaldehyde polymer (form C) begins which is thermally reversible at temperatures > −90°C.
Abstract: Absorption, emission, and NMR studies indicate that: (1) Formaldehyde exists as a monomer (form A) in nonpolar solvents to a temperature of approximately −95°C, (2) at −95°C in nonpolar solvents, formation of a formaldehyde polymer (form C) begins which is thermally reversible at temperatures > −90°C. The form C also exists at room temperature in water, dimethyl sulfoxide, dimethylformamide, and tetrahydrofuran. The formaldehyde‐formaldehyde interaction is principally of a dipole‐dipole type. (3) Formaldehyde can act as a hydrogen‐bonding donor or acceptor in a complex with solvent molecules or silica gel (form B). In aromatic hydrocarbons, formaldehyde acts as a donor whereas in 2‐methyltetrahydrofuran, chloroform, and silica gel it acts as an acceptor. Also, in 2‐methyltetrahydrofuran, forms A and B exist in addition to C. Monomer formaldehyde exhibits a fluorescence from the lowest Sn,π* state in nonpolar solvents to −95°C. Both the forms B and C exhibit emission. In addition to the classification of t...
TL;DR: In this paper, the concentration of hydroxyl groups on the surface of silica gel has been determined by determining the concentration in D2O/H2O liquid mixtures.
Abstract: By determining the concentration of D2O in D2O/H2O liquid mixtures, it has been possible to develop a method to obtain the concentration of hydroxyl groups on the surface of silica gel. The results of 4.4 ± 0.2 –OH groups per 100 A2 of surface are in good agreement with the findings of other workers.
Durch Bestimmung der Konzentration von D2O in flussigen Mischungen von D2O/H2O war es moglich, ein Verfahren zu entwickeln, um die Konzentration von Hydroxylgruppen auf der Oberflache von Silica-Gel zu bestimmen. Die erhaltenen Werte von 4,4 ± 0,2 OH-Gruppen pro 100 A2 Oberflache stimmen mit den Ergebnissen anderer Autoren gut uberein.
TL;DR: In this paper, the adsorption and desorption behavior of PMMA chains on silica gel from chloroform solution were investigated by using high-resolution NMR spectroscopy.
Abstract: The adsorption and desorption behaviour of tactic poly(methylmethacrylate) (PMMA) chain on silica gel from chloroform solution are investigated by using high-resolution NMR spectroscopy.
The conformation of PMMA chains adsorbed on silica and the effects of polar additives on polymer adsorption are discussed.
It is shown that the adsorption of PMMA on silica surface is so strong as to restrict highly the polymeric motion of PMMA at segmental level. The conformation of PMMA adsorbed on silica gel surface is considered to be a uniformly adsorbed and relatively compressed form. The NMR technique is very effective to estimate the fraction of segments of which the segmental motion is restricted because of the adsorption on silica gel.
The methanol/silica interaction is stronger than the PMMA/silica interaction, and methanol reduces rapidly PMMA adsorption on silica. The rate of adsorption displacement of PMMA by methanol is relatively rapid and PMMA almost reaches the equilibrium adsorption value within 30 min at room temperature.
Mittels hochauflosender Kernresonanzspektroskopie wird das Adsorptions- und Desorptionsverhalten taktischer Polymethylmethacrylate aus Chloroformlosung an Kieselgel untersucht. Dabei werden die Konformation der an Kieselgel adsorbierten PMMA-Ketten sowie der Einflus polarer Agenzien auf das Adsorptionsverhalten diskutiert.
Es wird gezeigt, das PMMA so stark auf der Kieselgeloberflache adsorbiert wird, das die Beweglichkeit der einzelnen Polymerenabschnitte stark eingeschrankt ist. Man kommt zu der Annahme, das die PMMA-Kette auf Kieselgel gleichmasig adsorbiert wird und in relativ kompakter Form vorliegt. Mit Hilfe der Kernresonanzspektroskopie konnen diejenigen Abschnitte, deren freie Beweglichkeit infolge der Adsorption an Kieselgel behindert i st, indirekt bestimmt werden.
Die Wechselwirkung zwischen Methanol und Kieselgel ist starker als diejenige zwischen PMMA und Kieselgel, so das durch Zugabe von Methanol die PMMA-Adsorption rasch vermindert wird. Methanol ersetzt PMMA bei der Adsorption relativ rasch. Das Gleichgewicht wird bei Zimmertemperatur nach ca. 30 Min. erreicht.
TL;DR: In this paper, the adsorption on silica gel of a series of electron pair donors with a variation of the pKa value from 12 up to the range of negative values was subjected to IR spectroscopic investigation.
01 Apr 1972
TL;DR: In this article, the modification of selectivity through pressure-induced changes in column equilibria has been shown to be significant using a chromatograph capable of going to 4000 kg/cm2.
Abstract: With water as the solvent and two azo dyes as the exemplary solutes, the modification of selectivity through pressure-induced changes in column equilibria has been shown to be significant using a chromatograph capable of going to 4000 kg/cm2. Data from high-pressure conductance, spectroscopy, adsorption chromatography, and steric-exclusion chromatography indicated that the primary contribution to the pressure shifts in selectivity was occurring in the bulk solution. An explanation correlating the various experimental observations is offered.
TL;DR: In this paper, thin-layer chromatography (TLC) was applied giving three zones with different Rf values and showing positive IAR in the urine of workers exposed to carbon disulfide, which cause the iodineazide reaction.
Abstract: Isolation and identification of two of the metabolites excreted in the urine of workers exposed to carbon disulfide, which cause the iodineazide reaction (IAR), have been performed. After concentration of the urine, thin-layer chromatography (TLC) was applied giving three zones with different Rf values and showing positive IAR. The urine was concentrated by vacuum distillation and extracted by ethyl acetate. Extract was evaporated to dryness and put on a silica gel (Silica Gel G) column. Elution with various organic solvents was performed, but water eluate produced the strongest IAR. Evaporation of the water eluate produced white crystals. By TLC, determination of melting point, mass spectra, and infrared spectra, it was established that this metabolite showed the structure of thiocarbamide. The quantity of thiocarbamide is much greater than that of the first metabolite in the urine of exposed workers.
TL;DR: In this paper, the R f values of twenty-two carotenoids separated on Whatman paper Chromedia AH 81 and SG81 are given and reproducible in about half an hour.
TL;DR: In this paper, the Astragalus cibarius Sheld was extracted with acetone and purification by silica gel chromatography of the residue from the acetone extract yielded a colorless, crystalline compound, m.p. 122°.
TL;DR: Thin-layer chromatography of keto acid 2,4-dinitrophenylhydrazones was carried out on plate coated with silica gel and sodium bicarbonate and results indicate usefulness of the present method for separation, detection, and determination ofketo acids.
TL;DR: It has been shown that a 5-m gas Chromatographic column (60–80 chromosorb G 1 per cent w / w SE 52) is comparable in terms of resolution and time of analysis to a capillary column.
TL;DR: In this paper, the preparation of copper-on-silica gel catalysts containing 15% and 20% copper is described, which can be reused three times without appreciable loss of activity.
Abstract: The preparation of copper-on-silica gel catalysts containing 15% and 20% copper is described. These catalysts can be reused three times without appreciable loss of activity. Their activity compares favorably with the highly active 5% copper-on-silica gel catalyst previously reported. Higher copper catalysts are somewhat less selective for the reduction of linolenate in soybean oil than 5% copper-on-silica gel, but these copper catalysts have greater activity, better reuse characteristics, and selectivity comparable to commercial copper-chromite catalysts.
TL;DR: The sensitivity and reliability of the improved-flow micro-calorimeter have been examined by supplying given amounts of electric energy to the calibration heater inserted in the calorimeter as discussed by the authors.
Abstract: The sensitivity and reliability of the improved-flow micro-calorimeter have been examined by supplying given amounts of electric energy to the calibration heater inserted in the calorimeter. The detection limit of the heat amount was found to be 0.01 meal, and its probable error to be ±0.5 and ±0.3% at the heat evolutions of 10 and 40 meal respectively. The heat of the adsorption of benzene on silica gel from a cyclohexane solution has been measured at 30°C by the calorimeter thus constructed. The adsorption calorimetry indicates that benzene is adsorbed reversibly on silica gel, and that the differential heat of the adsorption of benzene is independent of the amount of adsorbed benzene, but that it depends strongly on the pretreatment temperature of the silica gel. The heats of adsorption were found to be 1.2, 1.6, 2.0, and 3.8 kcal/mol on silica gel samples treated at 100, 300, 500, and 800°C respectively. The findings on the heats of adsorption have been elucidated in terms of the interaction between b...
TL;DR: Three solvent systems were utilized for the development of the dansyl derivatives of several carbamate insecticides and a number of fluorescent products were obtained.
Patent•
27 Apr 1972
TL;DR: In this article, the bodies of a SILICA gelatin gelatin gelatin were grafted with ORGANIC GROUPS to MODIFY the SURFACE PROPERTIES THEREOF in which the gRAFTed group originated from an ORGANO SILANE.
Abstract: R1-C(-R2)(-R3)-O-CH2-COO-R4-SI(-R5)(-R6)-R7 1. BODIES OF SILICA GEL GRAFTED WITH ORGANIC GROUPS TO MODIFY THE SURFACE PROPERTIES THEREOF IN WHICH THE GRAFTED GROUP ORIGINATES FROM AN ORGANO SILANE SELECTED FROM THE GROUP CONSISTING OF AN ORGANO SILANE HAVING THE FORMULA WHEREIN R1, R2 AND R3 ARE MONOVALENT GROUPS SELECTED FROM THE GROUP CONSISTING OF CX3 AND X WHEREIN X IS HALOGEN AND AT LEAST ONE X IS FLUORINE, R4 IS ALKYLENE, AND R5, R6 AND R7 ARE GROUPS ATTACHED DIRECTLY TO THE SILICON ATOM, AND ARE SELECTED FROM THE GROUP CONSISTING OF HALOGEN AND ALKYL, WITH AT LEAST ONE OF THE R5, R6 AND R7 GROUPS BEING HALOGEN; AND A COPOLYMER OF A VINYL TRIALKOXY SILANE AND A COMPOUND OF THE FORMULA CH2=CH-COO-C(-F)(-CF3)2