Chromatographs (such as gas-, liquid-, ion- or thin-layer chromatographs) for the determination of gas or liquid components. The gas or liquid to be analysed is passed through columns or thin layers of absorbent material and then measured by means of a detector. The characteristics of the gases or liquids under analysis are indicated by the time taken for them to pass through the columns or thin layers of absorbent material, while the quantity of the different components to be analysed is indicated by the strength of the output signal from the detector.