Suppressed-mode anion chromatography

It is appropriate to refer here to the development of non-suppressed ion chromatography. A simple chromatographic system for anions which uses a conductivity detector but requires no suppressor column has been described by Fritz and co-workers.28 The anions are separated on a column of macroporous anion exchange resin which has a very low capacity, so that only a very dilute solution (ca 10 4M) of an aromatic organic acid salt (e.g. sodium phthalate) is required as the eluant. The low conductance of the eluant eliminates the need for a suppressor column and the separated anions can be detected by electrical conductance. In general, however, non-suppressed ion chromatography is an order of magnitude less sensitive than the suppressed mode. 

In addition to anion-exchange and ion-exclusion chromatography, organic acids in fruit juices can also be separated by reversed-phase chromatography in the ion-suppression mode. A suitable stationary phase for this type of application is Acclaim OA, a polar-embedded stationary phase optimized for hydrophilic organic acid separations. This column is compatible with 100% aqueous mobile phases and has excellent hydrolytic stability at low pH values. Retention,... 

Figure 2.10 Separation of anions in a carbonated apple juice using suppressed ion chromatography. Chromatography conditions column, AS11 with AG11 guard detector, CD20 conductivity detector with the ASRS self-regenerating suppressor in the recycle mode. (Courtesy of Dionex Corporation.)...

Ion-exchange is the primary separation mode used with modern ion chromatography, although other approaches used for separation of inorganic anions and cations include ion interaction, ion exclusion, and chelation chromatography. Ion chromatography, with suppressed conductivity detection, is the most widely used and generally offers the best performance. 

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