This sixth volume in the book series Progress in HPLC-HPCE examines the enhancement of high- performance liquid chromatography through the development of an advanced mode of electrochemical detection (ECD) — the coulometric array detection — from its initial, yet problematic, amperometric (thin-layer) design to the highly sensitive, selective and stable coulometric (flow-through) design. Unlike amperometric electrodes, the coulometric electrode is 100% efficient and measures signals from all of the analyte passing through it, which leads to improved sensitivity as well as unique selectivity. The coulometric electrode array offers the resolution of the photodiode array with the extreme sensitivity of an electrochemical detector.