Home > Explosives Detection > Technology > Chromatography > Ion Chromatography (IC)

Ion chromatography is a process that allows the separation of ions and polar molecules based on their charge properties. The process involves retaining target ions based on ionic interactions resulting from the stationary phase surface (i.e. resin type inside an analytical column) that contain ionic functional groups that interact, or attract, target analyte ions of opposite charge. Different stationary phases inside different analytical columns will exert different degrees of affinity for a particular target ion thus affecting its overall retention time. Additionally, the analytical column provides stable support for stationary phase ions that serve as active sites in the dynamic ion exchange process. Specific eluents, functioning as the mobile phase in ion chromatography, work to stabilize sample ions in solution and provide overall kinetic flow through the system. Eluents provide counter ions to compete with active sites located on the surface of the stationary phase within the analytical column for retention/elution of target ions. Eluent generation (concentration) can be varied as needed since its concentration is directly proportional to an applied current and inversely to the eluent flow rate. Adjusting concentration thus provides higher or lower eluent ion concentration to interact with the active sites on the stationary phase. Finally, different IC systems employ different forms of suppression that function to neutralize the salts of weak acids or weak bases that are produced via the dynamic ion exchange process. The result of suppression is a decrease in background conductivity and a concomitant increase in analyte response. These processes, working together in unison, allow ion chromatography to separate and identify those compounds generally considered nonvolatiles, not making their analysis conducive by other traditional analytical techniques such as GC/MS or LC/MS. Ion chromatography coupled with mass spectrometry can yield additional molecular elucidation by providing mass-to-charge (m/z) data, thus increasing confidence of ionic identification.