Ion chromatography (IC) is a form of liquid chromatography (LC) used for both inorganic and organic ions. In ion chromatography, the separation column is packed with an ion-exchange material rather than the conventional stationary phases based on adsorption. The separation mechanism is therefore different, detection is usually performed using a conductivity detector, and greater requirements are placed on the inertness of the surfaces in contact with the sample.
As the name suggests, ion chromatography is primarily used to analyse ions, which may originate from inorganic salts or, for example, organic acids. Common applications include the analysis of inorganic anions (F⁻, Cl⁻, Br⁻, SO₄²⁻, PO₄³⁻, etc.) and cations (Na⁺, K⁺, Mg²⁺, Ca²⁺, NH₄⁺). These analyses may be used for drinking water, contamination on surfaces, or purified water. For example, if deionised water is used for rinsing in a manufacturing process, it is important to ensure that the water is truly free from ions in order to avoid subsequent corrosion or adhesion problems in the process.
Organic acids such as formic acid and acetic acid can also be analysed by ion chromatography, for example to assess corrosivity or evaluate degradation processes.
Using air sampling equipment, ion chromatography can also be used to analyse emissions of both organic acids (formic acid, acetic acid, etc.) and inorganic acids (hydrochloric acid, sulfuric acid, etc.). Organic acids are often used as markers of the degradation of organic substances, while inorganic acids such as sulfuric acid can be formed as a result of the combustion of sulfur-containing compounds, for example contributing to acid rain.
Both organic and inorganic acids can cause corrosion problems in industrial processes or during product storage.
Advanced ion chromatography instrumentation with both UV-VIS and conductivity detectors, gradient pumping, electrochemical suppression, and eluent generation.