Ion-exclusion chromatography of ethanolamines on an anion-exchange resin by elution with polyols and sugars

Ion-exclusion chromatography of mono-, di- and triethanolamines of different basicity (pK(b)) and hydrophobicity was investigated on a polystyrene-divinylbenzene (PS-DVB)-based strongly basic anion-exchange resin in the OH- form. Conductivity detection and UV detection at 200 nm were used. When water was as an eluent, the ethanoamines were separated from strong base (NaOH) but the resolution was low and some peaks were fronted. This is due mainly to adsorption as a side-effect in the ion-exclusion chromatography. To improve the peak shape and the peak resolution, aqueous eluents containing polyols or sugars with 1-8 alcoholic OH groups (methanol, ethylene glycol, glycerol, erythritol, xylitol, fructose, sorbitol and sucrose) were tested for the ion-exclusion chromatographic separation of ethanolamines. When aqueous eluents containing polygols or sugars were used, peak fronting was decreased drastically by increasing a number of OH groups in the polyols and sugars. This is due mainly to the increase in the hydrophilicity of the PS-DVB surface by the OH groups. When an aqueous fructose eluent was used, fructose was strongly adsorbed on the resin surface. By this permanent coating method, the ion-exclusion chromatographic separation of ethanolamines was accomplished successfully by elution with water with reasonable resolution and highly sensitive UV and conductimetric detection.