Reverse-phase silica gel

Sixteen solid-phase materials were tested on a laboratory scale and the antho-cyanin and sugar content of collected fractions were determined. Among these, reverse-phase silica gels and macroreticular non-ionic acrylic polymer adsorbents such as Serdolit PAD IV or Amberlite XAD-7 turned out to be most suitable. SPE was used to investigate these materials on an enlarged scale, improving elution gradient and column purification. Amberlite XAD-7 was successfully applied in a middle-scale separation. ... 

Reversed-phase silica gel column Place a cotton wool plug at the bottom of a glass chromatography column. Pack 5 g of reversed-phase silica gel slurried with a solvent mixture of n-hexane-benzene-methanol (80 20 0.4, v/v/v) into the glass column. Place an anhydrous sodium sulfate layer about 1 -cm thick above and below the silica gel bed Bell jar-type filtering apparatus Buchner funnel, 11-cm i.d. 

Reversed-phase silica gel, silica gel ODS-Q3,75A, 30-50-p.m (Wako Pure Chemical Industries, Ltd)... 

Reversed-phased silica gel column chromatography cleanup... 

Dissolve the crop residue samples from Section 6.3 in 0.5 mL of dichloromethane. Transfer this solution to the top of the reversed-phased silica gel column with... 

Curran DP (2002) Fluorous Reverse Phase Silica Gel. A New Tool For Preparative Separations in Synthetic Organic and Organofluorine Chemistry. Syn-lett 1488-1496... 

Curran DP, Luo ZY (1999) Fluorous Synthesis with Fewer Fluorines (Light Flu-orous Synthesis) Separation of Tagged from Untagged Products by Solid-Phase Extraction with Fluorous Reverse-Phase Silica Gel. J Am Chem Soc 121 9069-9072... 

Few reports exist on the l.c. separation of such cationic carbohydrate oligomers as those resulting from partial hydrolysis of chitosan. The neutral, A -acetylated analogs from chitin hydrolyses are, however, well separated on columns of aminopropyl silica gel and reversed-phase silica gel. ... 

In the case of amines the type of interaction shown in Figure 15.9 may occur. The shorter the alkyl chain length on the silica gel surface the more likely it is that adsorption also plays a part in the extraction. It is possible to buy highly endcapped reverse-phase silica gels where most of the residual silanols have been blocked but it may be better to take advantage of the mixed lipophilic and adsorptive properties of reverse phases which have not been endcapped. 

Curran, D. P. Hadida, S. He, M. Thermal Allylations of Aldehydes with a Fluorous Allylstannane. Separation of Organic and Fluorous Products by Solids Phase Extraction with Fluorous Reverse Phase Silica Gel, J. Org. Chem. 1997, 62, 6714. 

Cellulose was the first sorbent for which the resolution of racemic amino acids was demonstrated [23]. From this beginning, derivatives such as microcrystalline triacetylcellulose and /3-cyclodextrin bonded to silica were developed. The most popular sorbent for the control of optical purity is a reversed-phase silica gel impregnated with a chiral selector (a proline derivative) and copper (II) ions. Separations are possible if the analytes of interest form chelate complexes with the copper ions such as D,L-Dopa and D.L-penicillamine [24], Silica gel has also been impregnated with (-) brucine for resolving enantiomeric mixtures of amino acids [25] and a number of amino alcohol adrenergic blockers were resolved with another chiral selector [26]. A worthwhile review on enantiomer separations by TLC has been published [27],... 

Fig. 7. Synthesis of a library containing 100 mappicine derivatives with fluorous tags (Rf) efficient separation on fluorous reversed-phase silica gel is possible on the basis of the fluorine content of the tag [44].

Owing to their intrinsic basicity, marine invertebrate guanidine alkaloids have a rather polar behavior and their isolation from complex mixtures may be difficult. Isolation procedures frequently include chromatography on lipophilic Sephadex LH20, on reversed phase silica gel (such as Cig bonded, aminopropyl bonded, or cyanopropyl bonded), or even on ion-exchange resins. HPLC purification using acidic (TFA) or buffered eluents have frequently been employed. 

Fluorous reverse-phase silica gel (separation by solid phase extraction). The hydroxyl residues on silica gel are modified with perfluoroalkyl chains. This causes a fluorophilic effect between the fluorous reagent/ catalyst/product and allows facile separation independent of temperature. 

Fluorous reverse phase silica gel (FRPSG) has been used in the purification of synthetic DNA fragments.In solid phase DNA synthesis, truncated sequences are often separated from the desired product after deprotection using HPLC or electrophoresis. In order to perform, parallel syntheses and separations of nucleotides the trityl-on purification procedure was developed, in which a lipophilic support material is used to separate the desired and undesired product, followed by deprotection. If the protecting group is labelled with a fluorous group, fiuorous-fiuorous interactions between the FRPSG and the protected nucleotide can be used to aid separation of the aqueous mixture. 

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