There is a wide range of detectors available for both GC and LC each having their own particular areas of application. In general the more catholic the response, the less sensitive the detector and the most sensitive detectors are those that have a specific response. The performance of all detectors should be properly specified so that the user can determine which is most suitable for a specific application. Such specifications are also essential to compare the performance of different detectors supplied by alternative instrument manufactures. Detector specifications should be presented in a standard form and in standard units, so that detectors can be compared that function on widely different principles.