Ion chromatography retrospective

In the 1960s and early 1970s, various chromatographic methods were used to separate low molecular weight inorganic anions and cations; however, the separations were only moderately efficient, and detecting those analytes that did not absorb UV radiation was rather difficult. It was more common for researchers to determine these analytes by wet-chemical methods (especially titrations) or electroanalysis (usually with an ion-selective electrode). The real impetus for the development of ion chromatography (IC) came in a paper by Small, Stevens, and Bauman in 1975 (1). This paper presented two very significant developments that laid the foundation for the emergence of IC as a powerful analytical technique‚ÄövÑvÆa new method for preparing highly efficient stationary phases to separate inorganic ions and a new approach to sensitive conductivity detection. It is rare for two such profound developments to appear within a single publication, but these developments together created a form of IC that still dominates the field today. IC should not be regarded as a single, specific analytical technique but rather as a collection of LC techniques used to separate inorganic anions and cations and low molecular weight water-soluble organic acids and bases. These techniques include ion-exchange, ion-exclusion, and ion-interaction (ion-pair) chromatographies. We cannot cover all of these techniques, so we will deal only with ion-exchange systems. These are the most common and comprise about 75% of published IC applications. Furthermore, we will emphasize determining inorganic anions because this is the most common IC application. Readers interested in comprehensive coverage of the development of IC should check elsewhere (2‚Äö-6). About the same time as the publication of the 1975 paper, Dow Chemical (where Small, Stevens, and Bauman worked) patented and subsequently licensed the technology, which became known as suppressed IC‚ÄövÑvp, to Durrum Instruments, which later became Dionex, for commercial development. This form of IC proved to be commercially successful and became widely used. The development of IC by Dionex was swift, sustained, and scientifically elegant. The patents protecting the technology had the rather unexpected effect of stimulating several alternative approaches to ion analysis, many of which are still used today.