Ion chromatography -Stationary phases and separation methods

Ion chromatography (IC) is the modern evolution of ion exchange chromatography. It was introduced in 1975 with the advent of conductimetric detection combined with chemical conductivity reduction by Small, Stevens and Bauman . It has gradually established itself as a general name for rapid liquid chromatographic ion separation techniques on columns coupled "on line" with a continuous cell detector, enabling detection and quantification of both organic and inorganic ions. Its success is due to its speed, sensitivity, flexibility, relative ease of use, reliability, affordability and automation capabilities.

Originally, IC was an ion exchange chromatography coupled with conductimetric detection. It rapidly diversified. Today, it covers a whole range of separative techniques for analyzing ionic species by liquid chromatography, developed through the perfecting of increasingly high-performance stationary phases, combined with a variety of detection methods. Its field of application covers sectors as diverse as energy, the environment, microelectronics, the chemical, pharmaceutical and food industries.

In the field of inorganic element determination, which is the subject of this article, ion chromatography plays a key role, mainly in water analysis, where it is highly effective for the determination of anions (fluorides, chlorides, sulfates, etc.) and certain cations such as those of the alkali and alkaline-earth families (lithium, sodium, magnesium, calcium). It should be noted, however, that the coupling of IC with absorption or atomic emission spectroscopic methods enables the analysis of transition elements, lanthanides and actinides. In addition, its separative nature enables it to resolve certain difficulties posed by direct spectrometric techniques, such as matrix effects, interferences and speciation studies. Nevertheless, in the vast majority of cases, the determination of cations is best carried out using direct spectrophotometric techniques and, in particular, the coupling of an inductively coupled plasma atomic emission method with mass spectrometric detection (ICP/MS).

The apparatus comprises the same elements as any chromatographic system; the specific components of the IC are :

• the chromatographic column packed with a stationary phase which is usually specific;

• conductivity sensor and ion suppression devices in certain applications;

• the materials making...