Early milestones in the development of ion-exchange chromatography: a personal account.

Ion chromatography as we know it today was built on a foundation of knowledge accumulated over a period of many years. Here, we review some of the outstanding earlier achievements in ion-exchange chromatography. Beginning about 1947. Spedding and Powell at Iowa State published a series of papers describing practical methods for preparative separation of the rare earths by displacement ion-exchange chromatography. The same group then demonstrated the ion-exchange separation of 14N and 15N isotopes in ammonia. Beginning in the 1950s. Kraus and Nelson at Oak Ridge published numerous analytical methods for metal ions based on separation of their chloride, fluoride, nitrate or sulfate complexes by anion chromatography. In the period from about 1960 to 1980 many clever chromatographic methods for metal ion separations were reported by researchers throughout the world and automatic in-line detection was gradually introduced. A truly innovative method by Small, Stevens and Bauman at Dow Chemical Co. marked the birth of modern ion chromatography. Anions, as well as cations, could now be separated quickly and conveniently by a system of suppressed conductivity detection. A method for anion chromatography with non-suppressed conductivity detection was published by Gjerde et al. in 1979. This was followed by a similar method for cation chromatography in 1980. Ion chromatography as we know it today did not just happen. It was built on a solid foundation of knowledge that has accumulated over a period of many years. Revisiting the older ion-exchange chromatography serves not only to pay tribute to some remarkable accomplishments, but it can also be a learning experience. Trends and ideas in science tend to run in repeating cycles. Thus, an awareness of older work may provide inspiration for new research using improved contemporary technology. Selection of milestones is a rather personal matter. I chose to write about subjects of which I came to have a firsthand knowledge during my career. The topics selected are in roughly chronological order and cover the period from about 1945 to 1980. An effort has been made to explain the chemical principles as well as to recount the major accomplishments of the various research projects.