Ion Chromatography: Yesterday, Today, and Tomorrow

摘要

As a liquid chromatographer, one tends to lump ion-exchange chromatography (IEC) and ion chromatography (IC) in the same bucket, but there are actually significant differences in the practice of these methodologies. Both techniques use columns with ionogenic functionality, mobile phases with various buffer compositions, and separate ionic compounds in simple to complex matrices. Early on, IEC had its biggest success in the separation of amino acids, helping Moore and Stein win the Nobel Prize in chemistry in 1972 and in the separation of transuranium elements during the development of the atomic bomb back during World War II. However, the biggest difference between the two techniques is based on the needs of the early detection principle of conductivity the removal of the buffer from the mobile phase before detection. In the early 1970s, Hamish Small and coworkers, while working at Dow Chemical in Midland, Michigan, envisioned a method with a fast separation of non-chromophore-containing ionic compounds but in a nonconducting mobile phase, water. The concept of buffer removal (stripping), later termed eluent suppression, was a key element in the development and differentiation of IC from other ion-exchange separations. It spurred the development of specialized low specific exchange capacity packings, sophisticated suppressors with regeneration capabilities, and new detection principles such as indirect photometric and pulsed amperometric detection. Throughout the decades, alongside high performance liquid chromatography (HPLC), IC has seen parallel developments in separating ionic compounds in a variety of matrices.