Ion chromatography (or ion exchange chromatography) separates polar ions and molecules based on their affinity for the ion exchanger. It works on almost any type of charged molecule - including large proteins, small nucleotides, and amino acids. A buffered aqueous solution called the mobile phase carries the sample from the ring circuit to a column containing some form of stationary phase material. The analyte of interest must then be detected by some means, usually by conductivity or UV/visible light absorption. Controlling a microchip system usually requires a chromatographic data system (CDS). In addition to microchip systems, some of these CDS can also drive gas chromatography (GC) and HPLC.