Eluants in Ion-Exclusion Chromatography

5 mmol/L H2SO4 flow rate 0.5 mL/ min detection Rl analytes (1) sucrose, (2) glucose, (3) citric acid, 

The high retention of aliphatic monocarboxylic acids (ric 4) and aromatic carboxylic acids can be lowered by adding small amounts of an organic solvent (10 to 30 mL/L) to the eluant. This blocks adsorption sites on the surface of the stationary phase [8]. Acetonitrile, 2-propanol, or ethanol are particularly suitable. If possible, methanol should not be used, because the stationary phase is subject to strong volume changes when using this solvent. 

According to Tanaka and Fritz [9], comparably low backgroimd conductivities were obtained with a benzoic acid eluant, as benzoic acid is only partly dissociated. The acid strength of a dilute benzoic acid solution is sufficient to elute aliphatic carboxylic acids with good peak shapes. 

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