Silica silver-impregnated

Since the dihaloketones may induce the decomposition of the product, it is essential to cool the solution in ice befoie allowing entry of air. Otherwise, the oily cycloadduct becomes brown, and polymeric material has to be removed before crystallization by passage down a 2x5 cm. column of silica gel (impregnated with 12% silver nitrate solution and redried). 

Hammond and Irwin (97) have demonstrated a similar separation of StElSt and StOSt (St = stearic acid) on a silica column impregnated with silver ions. It is also worth mentioning in... 

Polychlorobiphenyls Silica gel impregnated with 8% paraffin oil Acetonitrile acetone methanol water (20 9 20 1) Mixture of silver nitrate and 2- phenoxy ethanol — o 1, o... 

The surface of the silica may be dynamically coated with transition metals, and the selectivities observed can be attributed to the complexes between the metal ions and the analyte species [56], The use of silver-impregnated silica (adsorption of salts of transition metals on the silica surface) has been used for the analysis of saturated and unsaturated fatty acid methyl esters (FAME) and triacylglycerols (TAG) [57], The retention of the unsaturated FAME and TAG can be attributed to the stability of the complex that is formed between the K electrons of the carbon-carbon double bonds and the silver ions. The predominant interaction for saturated analytes is with the polar silanol groups. The secondary interactions are those of the silver ions with the unpaired electrons of the carbonyl oxygens of the analytes. The amount of silver adsorbed onto the silica and the pH (employment of acidic or basic modifiers) have been determined to have an effect on the retention and resolution of certain acidic and basic compounds and fatty acids [58]. 

Monocarboxylic esters were further separated by argentation TLC [silica GF254 impregnated with 5% (w/v) silver nitrate] into saturated esters (Rf = 0.51), monounsaturated esters (R = 0.42), diunsaturated esters (Rf = 0.29), and poly unsaturated esters (Rf < 0.29) by development in n-heptane-diethyl ether-methanol (90 10 1, v/v/v) (19). 

Sfiica impregnated with saturated and unsaturated hydrocarbons (squalene, paraffin oil), silicone and plant oils, complexing agents (silver ions, boric add and borates, unsaturated and aromatic compounds), tigands (EDTA, digitonin), and transition metal salts silanized silica gel impregnated with anionic and cationic surfactants Cross-linked, polymeric dextran gels (Sephadex)... 

Gunstone ct found that separation of saturated and unsaturated fatty acid glycerides by crystallization at -10° is improved by addition of silver nitrate in methanol to complex with the unsaturated components. Morris reports separation of CIS and trans fatty acids and oxygenated fatty acids by thin-layer chromatography on silica gel impregnated with silver nitrate. With untreated silica there was no separation. 

A,S.ergotamine,ergo tami nine,caffeine Butalbital.phenobarbital Separation on silver impregnated silica gel Lichrosorb Si 100 5iim,imp. with 1.09% Agl... 

Ergta.Ergtaine Butalbital, atropine,scopo- phenobarbital lamine,caffeine Separation on silver impregnated silica gel... 

One example is known in which the elements of a phosphinic acid are eliminated in the same reaction step. In the synthesis of (-f)-( / ,2/ )-[( )-hex-l-enyl]-2-vinylcyclopropane [(-E)-dic-tyopterene, 4] and its (—)-enantiomer, the ji-oxo phosphane oxide 2 obtained by condensation of pentyidiphenylphosphane oxide with methyl 2-vinylcyclopropanecarboxylate (1) was first reduced to the corresponding /(-hydroxy phosphane oxide 3 and then treated with sodium hydride in dimethylformamide. This procedure gave the desired diene 4 and its enantiomer in 19 to 23% yield from the P-oxo phosphane oxide. The stereoselectivity was fairly good, giving 85% of the 5-isomer, which could be separated on silver-impregnated silica gel. ... 

Conversion of ( )-F to ( )-H [=( )-3f)-hydroxyisopimara-8(14), 15-diene] could be executed in the usual manner. The stereoisomers ( )-H and ( )-I were separable by chromatography over silica gel impregnated with silver nitrate. The overall yield of ( )-H was 8.5% (15 steps) based on ( )-C. 

Sterols and their acetates have been separated by column and thin-layer chromatography on silica gel impregnated with silver nitrate.17c... 

In a synthesis of A -cholestadiene-la,3 -diol (la-hydroxyprovitamin D3), Israeli chemists effected dehydrobromination of the dibromide (1) at 130° (4 hr.) in HMPT containing about 10% of triethylmethylammonium dimethyl phosphate. A 1.3 1 mixture of the A -diene (2) and the A -diene (3) was obtained in almost quantitative yield. The mixture was separated on a silica column impregnated with silver nitrate. 

Isomers of the unsaturated fatty acid esters (55) and uhsatnrated normal aldehydes (59) which differ only in the position of a double bond in the alkyl chain are surprisingly well separated on silver-impregnated silica but not on normal silica. The basis for these effects is somewhat more complicated than simple steric hindrance to silver ion complexation, however. TV"... 

Silica, and to a lesser extent alumina, are the most common stationary phases used for the separation of low molecular mass organic compounds. Chemically bonded silica sorbents are used for the separation of polar organic compounds in the normal-phase and reversed-phase modes. Wide-pore, chemically bonded sorbents, are used for the separation of biopolymers [18,22]. Some separations require specially prepared stationary phases, such as silica gel impregnated with silver nitrate for the isolation of unsaturated compounds capable of forming charge transfer complexes with silver [23] (section 10.6.1), or silica and chemically bonded phases coated with cellulose tris(3,5-... 

Pyka and Bober " separated a- and y-terpinene as well as a- and 3-pinene on silica gel and on silica gel impregnated with various percentages of silver nitrate. It was stated that argentation thin-layer chromatography is an efficient technique for separation of isomeric a- and y-terpinene as well as a- and (3-pinene. The topological indices based on... 

The cis and trans isomers of linolenic acid were analyzed as their phenacyl derivatives on a silver-impregnated silica column (2 = 242 nm). The method for the preparation of the column is discussed. A 49.75/49.75/0.5 1,2-dichloroethane/ DCM/acetonitrile mobile phase was used and elution was complete in under 40 min [763]. Peaks were well resolved and peak shapes were good. A linear concentration range of 0-200 pg was reported. 

AC-6120 silver impregnated silica gel -130 -135 102-105 High Used at the WAK plant Germany, sorbent is not regenerated... 

Reference may be made here to a procedure for separating mixtures of mono-olefinic fatty acids and for subsequently determining the structure of the components [11]. This method utilises two-dimensional TLC on silica gel, impregnated with paraffin and silver nitrate a similar procedure is described in [225]. A scheme for determination of the position and configuration of the double bonds in polyolefinic acids [170] depends on partial hydrogenation with hydrazine, separation of the reduction products through argentation-TLC and determination of... 

Silica gel impregnated with silver nitrate (usually 5-10%) is also a useful adsorbent for some functional groups. The silver cation selectively binds to unsaturated sites via a sUver-ion tt complex. Traces of alkenes are easily removed from saturated reaction products by chromatography with this system (see Experiment [12]). This adsorbent, however, must be protected from light until used, or it will quickly darken and become ineffective. 

Ishikawa, T., et al., Adsorption of organic halides on silver-impregnated silica gels, Adsorpt. Sci. Technol., 1(1), 93-102(1984). 

Esters and Skin Waxes with Chromatography on Silica Gel Impregnated with Silver Nitrate Acta Chem. Scand. 17 538-540 (1963) ... 

Anionics. The analysis of LAS using a Silica Gel G layer (a standard TLC silica) impregnated with 10% ammonium sulphate, with 2-methyl-4-pentanone/propyl alcohol/0.1 N acetic acid/acetonitrile (20 6 1.6 1, v/v/v/v) and visualisation by a spray of 5% phosphomolybdic acid in ethanol followed by charring by heating is described in [41]. The analysis of the parent LAB using layers of silica gel impregnated with 15% silver nitrate and double development with dichloromethane followed by recovery of the spots and analysis by GC/MS is described in [2]. 

Derivatives are often used in lipid chemistry to prepare fatty acid methyl esters needed to determine the fatty acid composition of lipids. Fried et al. (1992) published a technique on the transesterification of 500-mg samples of snail tissue. Because the technique is applicable to other biological tissues and fluids, it is presented herein. Lipids were extracted from snail bodies with 10 ml of chloroform-methanol (2 1) the extracts were filtered through a plug of glass wool contained in a Pasteur pipet, and nonlipid contaminants were removed by extraction with 8 ml of Folch wash (0.88% aqueous KCl). The lipid-containing lower phase was separated and evaporated just to dryness under a stream of nitrogen at room temperature. The total lipid sample was dissolved in about 30 ml of methanol, and 0.5-1.0 ml of concentrated sulfuric acid was added. The mixture was refluxed for 1 h the formed fatty acid methyl esters were extracted with 30-40 ml of petroleum ether and the extract dried over anhydrous sodium sulfate. The fatty acid methyl esters were concentrated on a Rotoevaporator at 40°C and the volume reduced to 1 ml. The fatty acid methyl esters can be separated by TLC on silica gel impregnated with silver nitrate (Christie, 1982). 

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