Adsorbents silica gel

Technique of thin-layer chromatography. Preparation of the plate. In thin-layer chromatography a variety of coating materials is available, but silica gel is most frequently used. A slurry of the adsorbent (silica gel, cellulose powder, etc.) is spread uniformly over the plate by means of one of the commercial forms of spreader, the recommended thickness of adsorbent layer being 150-250 m. After air-drying overnight, or oven-drying at 80-90 °C for about 30 minutes, it is ready for use. 

Snyder [28] has shown that there is a correlation between the e° values for a certain polar adsorbent (silica gel, florisil, and magnesia) and alumina. For example. 

The organic solvent used to elute the compound must be adequately strong (polar for the adsorbent silica gel) and a good solvent for the component. Absolute methanol should be avoided as a siugle solvent because silica gel itself and some of its common impurities (Fe, Na, SO4) are soluble iu this solvent and will contaminate the isolated material. Solvent containing less than 30% methanol is recommended, or ethanol, acetone, chloroform, dichloromethane, or the mobile phase originally used for PLC are other frequently nsed choices for solnte recovery. Water is not recommended because it is so difficult to remove by evaporation during the concentration step (removal by lyophilization is necessary). A formula that has been used to calculate the volume of solvent needed when the PLC mobile phase is chosen for elution is ... 

Buerge et al. [8] PCMs (AHTN and HHCB) Wastewater effluent Switzerland - Macroporous polystyrene-divinylbenzene adsorbent - Silica gel chromatography - GC-MS - Recovery=81-141% LOD=10 ng/L... 

Ethambutol Hydrochloride (+)-2-Amino- Butan-l-ol TLC-Method Adsorbent-Silica Gel-G, Mobile Phase-Ethyl acetate Glacial acetic Acid HC1 H20(11 7 1 1) Apply 2pi of each of two solns. in MeOH, containing (1) 5% w/v of T.S. (2)0.050% w/v of (+)-2-aminobutan-l-ol. Remove TLC plates, dry in air, heat at 105°C for 5 mts, cool, spray with cadmium and Ninhydrin soln.2, heat to 90°C for 5 mts. The spot obtained with (2) is more intense than with (1). NMT 1.0... 

Air Adsorb (silica gel) desorb (ethanol) GC/FID 0.01 mg/sample Eller (1994) [Method 2002]... 

A previous exploratory study attempted to recover the soluble, poorly volatile subclass of organic compounds in water (3). It used a set.of sequential adsorbents. Silica gel, the first adsorbent, filtered out particulate matter and adsorbed some hydrophobic compounds. The next adsorbent was a cation-exchange bed that recovered cations and amphoteric substances, and the last adsorbent was an anion-exchange bed. The effluent from this series of adsorbents contained the neutral compounds. The eluates from each bed and the effluents were then concentrated under vacuum. This system, the parfait method, was demonstrated to recover parts-per-billion concentrations of several known mutagens in amounts sufficient to be detected by bioassay. 

Adsorbent Silica gel Eluents Benzene-hexane, ethylacetate-benzene... 

Sherma and Slobodien [107] determined chloropyrofos insecticide and its metabolite 3,5,6-trichloro-2-2-pyridinol in potable water at 5pg L 1 by thin layer chromatography. Pre-adsorbent silica gel layers were used for resolution and silver nitrate for detection prior to reflectance scanning. Recovery of 3,5,6-trichloro-2,2-pyridinol from water was 84%. Recovery of chloropyrifos from potable water was 87.5%. 

In the 1950s and 1960s a major impetus was given to the use of thin-layer chromatography by Stahl [ 15-17) who constructed a spreader for the preparation of thin-layer plates, suggested the silica adsorbent ( silica gel nach Stahl ), and edited excellent text books, etc. Simultaneously, equipment for developments, chemicals, and laboratory supply for TLC became commercially available. 

A method for the complete structural analysis of complex mixrnres of methyl esters of saturated and un-samrated fatty acids has been performed by 2-D TLC. Adsorbent silica gel impregnated with a 10% solution of dodecane was used for the first direction with acetonitrile-acetone (1 1, v/v) as eluent. The silica gel for the second direction was impregnated with a 20% AgNOs and dipropyl ether-hexane (2 3, v/v) was used as eluent. In this way, complete separation of a standard mixture of the methyl esters of six saturated, nine monoethylenic, and three polyenic esters were achieved. 

The adsorbents silica gel, alumina, CaX zeolite and activated carbon were examined for their activity to adsorb phosgene [264]. Of these, the zeolite and the activated carbon were noted to be most effective. The carbon material was reported to completely adsorb small traces of phosgene from 1,1,1-trichloroethane upon stirring both adsorbent and solvent at room temperature for about 3 h [264]. Zeolite 13X is recommended for removing phosgene from trichloromethane (chloroform) [302]. 

Adsorbate Temperature/°C Pressure (mmHg) 5A Amount adsorbed/% Silica gel Active carbon... 

Figure 11. Dependence of In Vm values for benzene and some of its alkyl derivatives on reciprocal temperature. Adsorbent-silica gel, eluent-water.

The same adsorbent (silica gel 60 Fz-,., precoated plates, 20 X 20 cm Merck, Darra,stadt), the solvent systems and detection methods can be used a.s described for ascending I LC. Good. separations are obtained by solvent migrations of 5 cm only. 

Adsorbent Silica gel 60 F,.,-precoated plates (Merck, Germany)... 

Reference solutions Coumarins are prepared as 0.1% methatiolic solutions 5-lOjfl is u.sed for TLC. Adsorbent Silica gel 60 F., -precoated TLC plates (Merck, Germany)... 

Adsorbent Silica gel 60F , -precoated TLC plates (Merck, Darmstadt). 

Generalizing from Del pine s observations on the colors of a number of iridium(III) isomers, the original investigators concluded that the orange compound was the cis (1,2,3) isomer and the red compound, the trans (1,2,6) isomer. In view of the fact that the red compound exhibits solubilities and a melting point that might be expected to be characteristic of the cis isomer (see Properties) and the fact that of the two isomers the red compound is preferentially adsorbed by a polar adsorbent (silica gel), further stereochemical investigations such as measurements of dipole moments or absorption spectra would be desirable. ... 

Sholin A.F., Patrikeev V.V. and Balandin A.A. (1967) Selective adsorbing silica gels, the possibility of their applications in the catalysis. Nature of... 

Studies of typical nanomaterials (soil mineral components, adsorbents, silica gels with deposited proteins, so called smart surfaces, latexes, synthetic zeolites modified by ions, MCM-41 molecular sieves) were made earlier by the author of this chapter [11-17]. At present our research focuses on studies of surface properties (e.g. adsorption capacity), total heterogeneity (energetic and geometrical) of surface layers, as well as structures and phase transformations of... 

Krylova and Dolin [319,320] investigated the radiolysis of water adsorbed on silica gel induced by y-radiation ( Co). The radiolysis products, H2 and CO2, formed as a result of the energy transfer from the solid adsorbent silica gel to the molecules of the adsorbed water. The oxidation component of radiolysis is spent on the oxidation of trace amounts of organic compounds present on the sample surface carbon dioxide results. Radiolysis was investigated in relation to the conditions of the prehminary treatment of Si02, the amount of adsorbed water, and the intensity of the radiation. The formation of hydrogen from the surface OH groups of sihca gel was also possible. A likely mechanism of radiolysis was described. 

Adsorbent Silica gel Silica gel Molecular Aluminium Activated carbon Activated carbon... 

Bartels, V.H. Erlenmeyer, H. The problem of similarity in chemistry. Specifically adsorbing silica gels III. Helv. Chim. Acta. 1965, 48, 285-290. 

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