Simultanious Determination of Organic Acids by Photometric Ion Chromatography : Analysis of Sour-Taste Agents in Soft Drinks by Eluent Exchange

Abstract

A method for the simultaneous determination of organic acids was investigated by photometric ion chromatography by using two different eluents. A 4.6 mm i.d.×25 cm stainless column packed with MCI GEL SCA 01 (Mitsubishi Chemical Ind., Ltd.) was used as a separator column. Sample was injected into this column previously equilibrated with 1 mM citraconic acid at pH 6.8. After elution of monobasic organic acids, the eluent was exchanged to a stronger one, 1 mM m-sulfobenzoic acid at pH 6.8. Dibasic organic acids were eluted before the column reequilibration with the secondary eluent. On the other hand, tribasic organic acids such as citric acid were eluted with the secondary eluent. To prevent the base line disorder due to the eluent exchange, the determination at 254 nm was performed. Because this wave length is an isosbestic point of the two eluents. Sour-taste agents in soft drinks could be analysed directly after dilution of samples.