An emission-based detector for use in conjunction with capillary chromatography or other applications involving a gas sample having a small volume is provided. The detector is based on optical emission from a plasma medium. An optical cartridge or other detection and/or processing means may be provided to receive and analyse the emitted radiation and thereby obtain information on the gas to be analysed. The emission-based detector includes a gas inlet, a gas outlet and a capillary channel which is in fluid communication with the gas inlet and gas outlet. The capillary channel acts as the plasma chamber. Preferably, the capillary channel has transversal dimensions of the same order as the cross-section of typical chromatography capillary columns and defines a winding path within the detection area. A multi-cell emission-based detector and a method of analysing a gas sample using multiple detection cells are also provided.