Selective separation of ketoses and aldoses by chromatography on a polyethyleneimine ion exchanger

One of serious problems of preparative carbohydrate chemistry is the separation of aldoses from ketoses. Of a large number of chromatographic procedures for separation of aldoses and ketoses described in the literature, only the use of anion exchangers in the bisulfite form afforded satisfactory resolution. Samuelson and Sjoström [1] separated fructose from glucose and mannose on a Dowex 2 ion-exchange resin using a stepwise elution with differently concentrated ethanol. Separation of fructose, sorbose, and tagatose from aldoses was achieved on an ion-exchange resin Amberlit IRA-400 eluted with л-propanol [2]. Suitable application of Wofatit SBW in л-propanol led to the separation of ribulose from ribose and arabinose [3]. The ion exchangers in the bisulfite form enable effective separation of ketoses and aldoses only when alcohols are used as eluants. In this paper we describe a selective class separation of ketoses and aldoses on a polyethyleneimine ion exchanger in the CI or OH form eluted with water. We have investigated chromatographic separation of ketoses from aldoses on an ion exchanger Amberlit IR-120 cycled with hydrazine and using water as eluant. Even though this procedure afforded satisfactory results, the resin in the column lost its efficiency after the first run as a consequence of progressive deprivation of the cycling agent due to its disproportion to ammonia and nitrogen.