Polyhydric compounds chromatography

Separations of polyhydric alcohols by gas-liquid chromatography are of interest in fields other than carbohydrate chemistry, and it is convenient to make brief mention of some of these applications. Several references to the separation of polyhydric compounds without the formation of derivatives are given in the paper by Verachtert,473 and similar methods related to the separation of acyclic and alicyclic diols,617 to the separation of a series of a,(u-diols,818 to the analysis of ethylene glycol, methanol, and diethylene glycol,819 and to the an-... 

These treatments convert to ionic substances, and remove, nearly all constituents of natural materials the acid treatments release any inositol present as phosphate, or combined in phospholipids, glycosides, etc. Glycerol remains in the deionized sample, but it can be oxidized separately, or be removed by heat decomposition or by repeatedly evaporating the solution to dryness. Such polyhydric alcohols of greater chain length as erythritol and mannitol, when present, would still interfere. However, corrections can be made for these compounds by determining the formaldehyde which they form on periodate oxidation, or they may be removed by chromatography on filter paper. The micro-periodate method is well suited to the analysis of samples eluted from filter paper, provided that care is exercised to remove the tiny particles of cellulose which are usually found in such eluates. 

Gas chromatography is particularly useful for the characterisation of more volatile substances such as mixtures of fatty acids or of alcohols, esters or hydrocarbons which are used in polymer formulations. It has the advantage that it provides more information regarding the carbon number distribution of each of these types of compounds than can be obtained by infi ared spectroscopy alone. Similarly, if the polymer is known or suspected to contain dicarboxylic acids, polyol esters, polyhydric alcohols or alcohol esters of phthalic, sebacic, adipic or azelaic acids, then frequently, information on the type of compound present can be obtained by comparing under the same conditions the retention time of the unknown with those of known authentic substances. 

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