Ion Chromatography

Ion-exchange chromatography or Ion chromatography is used for analysis of aqueous samples in parts-per-million (ppm) quantities of common anions (such as fluoride, chloride, nitrate, nitrite and sulphate) and common cations (like sodium, potassium, ammonium, lithium, calcium and magnesium) using conductivity detectors. The chroma tography also has the capability to analyze aqueous samples for parts-per-billion (ppb) quantities of hydrazine, monomethylhydrazine (MMH) and unsymmetrical dimethyl hydrazine (UDMH). Ion chromatography is a process that allows the separation of ions and polar molecules based on their charges. The aqueous solution to be injected is usually called a 'sample' and the individual separated components are called 'analytes'. It is often used for water analysis, quality control and protein purification.

Ion chromatography is a form of liquid chromatography that uses ion-exchange resins or gel matrix consisting of agarose or cellulose beads in a column to separate atomic or molecular ions based on their interaction with the resin (stationary phase). A sample, with a minimum volume of 10mL, is introduced either manually or with an auto sampler, into a loop of known volume. A buffered aqueous solution known as the mobile phase carries the sample from the loop on to the column that contains the stationary phase. This target analytes (anions or cations) are retained on the stationary phase, but can be eluted by increasing the concentration of a similarly charged species that will displace the analyte ions from the stationary phase. In Ion chromatography ions in the aqueous sample are detected by measuring the conductivity of the solution. The mobile phase contains ions that create background conductivity, making it difficult to measure the conductivity due only to the analyte ions, as they exit the column. This problem can be greatly reduced by selectively removing the mobile phase ions after the analytical column and before the detector. This is done by converting the mobile phase ions to a neutral form or removing them with an eluent suppressor, which consists of an ion-exchange column or membrane. For cation analysis, the mobile phase is often HCl or HNO3 which can be neutralized by an eluent suppressor that supplies OH (-ve). For anion analysis, the mobile phase is NaOH or NaHCO3 and the eluent suppressor supplies H (+ve) to neutralize the anion.

1. It is used for water chemistry analysis and for detection of chemical contaminants in water especially drinking water.
2. It is used to determine sugar and salt content in foods.
3. It is used for isolation of select proteins.