Fractionation of Pure Compound Classes

Argentation chromatogra phy. This method depends on the reversible formation of jr-complexes of unsaturated lipids with silver ions. Adsorbents containing 5 % silver nitrate are used in TLC. 

Mixtures of saturated and unsaturated members of a lipid class are fractionated on silver nitrate-impregnated layers according to number, configuration and position of the double bonds. Homologous saturated or unsaturated compounds cannot be separated from one another. 

Both the saturated and unsaturated lipids can be eluted unchanged from the adsorbent. 

Chromatography of mercuric acetate adducts. Unsaturated lipids form acetoxymercuri-methoxy compounds with methanolic mercuric acetate. These mercuric acetate adducts of unsaturated compounds must be prepared before chromatography in contrast to the silver complexes which are formed on the silver nitrate-containing adsorbent during chromatography. 

Saturated lipids and the adducts of unsaturated substances, are fractionated on adsorbents according to the number of the acetoxymercuri-methoxy groups. Saturated homologues are not separated from one another. The adducts of homologous, cis-trans- and positionally isomeric lipids also cannot be separated. 

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Table 71. Solvents for fractionation of pure compound classes using reversed phase partition TLG and argentation-TLC [123]...

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