Silver compounds selective binding

Silver nitrate may be incorporated in the adsorbent slurry (25 g l-1) giving a final concentration of about 5% in the dry plate. The silver ions bind reversibly with the double bonds in the unsaturated compounds, resulting in selective retardation, and the lipids are separated according to the number and configuration (cis or trans) of their double bonds. This technique is extremely useful in fatty acids, mono-, di- and particularly triacylglycerol analyses when even positional isomers may be resolved. Borate ions may also be incorporated in the silica gel and these plates are used to separate compounds with adjacent free hydroxyl groups. 

Making your own plates allows greater flexibility of choice of sorbent and, whereas commercial plates are restricted to three or four sorbents, with the correct recipe, homemade plates offer much wider scope for experimentation. These plates also allow the variation of thickness to accommodate the separation of large amounts of material. Binders such as calcium sulphate (gypsum) are require to bind the sorbent to the plate, but some silica sorbents (e.g., Merck 7749) contain sufficient binder for the purpose. Preparing your own plates will also give you the choice of selecting a sorbet with or without a UV indicator and will also enable the incorporation of additives that enhance separation into the sorbent. An example of this (recipe shown below) is the addition of a small quantity of silver nitrate to a silica sorbent that aids the resolution of olefinic compounds. 

When 5 -0-Dmtr-cytidines, protected at N-4, were treated with alkyl iodides in the presence of silver(I) oxide, the 2 -0-alkylated compounds were the major product. N -t-Butylphenoxyacetyl protection gave the best selectivity, and the products were deaminated to 2 -C -alkyluridines. An alternative approach to 2 -0-alkylated ribonucleosides involves the use of 181, produced by selective debenzylation of the tris-(2,4-dichlorobenzyl) derivative (see Vol.21, p.49-50), in condensations with silylated bases. 3, 5 -Di-0-trityluridine has been alkylated at 0-2 using 2-chloromethylanthracene detritylation was followed by incorporation into oligonucleotides which exhibited enhanced fluorescence on binding to complementary RNA segments. The synthesis of 3 -D-(2-aminoethyl)-2 -deoxyuridines has been described these materials were used for the synthesis of dimers of type 175. ... 

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