"Chromatography" is the general term for a variety of physicochemical separation techniques, all of which have in common the distribution of a component between a mobile phase and a stationary phase. The various chromatographic techniques are subdivided according to the physical state of these two phases.

The discovery of chromatography is attributed to Tswett [1,2], who in 1903 was the first to separate leaf pigments on a polar solid phase and to interpret this process. In the following years, chromatographic applications were limited to the distribution between a solid stationary and a liquid mobile phase (liquid solid chromatography, LSC). In 1938, Izmailov and Schraiber [3] laid the foundation for thin-layer chromatography (TLC). Stahl [4,5] refined this method in 1958 and developed it into the technique known today. In their noteworthy paper of 1941, Martin and Synge [6] proposed the concept of theoretical plates, which was adapted from the theory of distillation processes, as a formal measurement of the efficiency of the chromatographic process. This approach not only revolutionized the understanding of liquid chromatography but also set the stage for the development of both gas chromatography (GC) and paper chromatography.

In 1952, James and Martin [7] published their first paper on gas chromatography, initiating the rapid development of this analytical technique.

High-performance liquid chromatography (HPLC) was derived from the classical column chromatography and, besides gas chromatography, is one of the most important tools of analytical chemistry today. The technique of HPLC flourished after it became possible to produce columns with packing materials made of very small beads (=10 µm) and to operate them under high pressure. The development of HPLC and the theoretical understanding of the separation processes rest on the basic works of Horvath et al. [8], Knox [9], Scott [10], Snyder [11], Guiochon [12], Möckel [13], and others.

Ion chromatography (IC) was introduced in 1975 by Small et al. [14] as a new analytical method. Within a short period of time, ion chromatography evolved from a new detection scheme for a few selected inorganic anions and cations to a versatile analytical technique for ionic species in general. For a sensitive detection of ions via their electrical conductance, the separator column effluent was passed through a "suppressor" column. This suppressor column chemically reduces the eluent background conductance, while at the same time increasing the electrical conductance of the analyte ions.

In 1979, Fritz et al. [15] described an alternative separation and detection scheme for inorganic anions, in which the separator column is directly coupled to the conductivity cell. As a prerequisite for this chromatographic setup, low-capacity ion-exchange resins must be employed so that low-ionic strength eluents can be used. In addition, the eluent ions should exhibit low equivalent conductances, thus enabling detection of the sample components with reasonable sensitivity.

At the end of the 1970s, ion chromatographic techniques began to be used to analyze organic ions. The requirement for a quantitative analysis of organic acids brought about an ion chromatographic method based on the ion-exclusion process that was first described by Wheaton and Bauman [16] in 1953.

The 1980s witnessed the development of high-efficiency separator columns with particle diameters between 5 and 8 µm, which resulted in a significant reduction of analysis time. In addition, separation methods based on the ion-pair process were introduced as an alternative to ion-exchange chromatography because they allow the separation and determination of surface-active anions and cati