A novel ionization (electron capture) gas chromatographic detector is described. The new design features an open cell, an anode-to-cathode gas flow and a porous anode. These features greatly reduce recirculation in the detector which in turn means that polar solvents may be injected without loss of the ability to detect trace quantities of halo-organics. The new detector design is also remarkably tolerant to highly impure samples and can be used at low flows. The desirable properties of electron capture type detectors, such as selectivity, linearity of response and extreme sensitivity are retained. A number of practical applications are described.