A photoionisation detector (PID) was coupled to packed-capillary liquid and supercritical-fluid chromatography to study its performance. Several mobile phases were tested to evaluate the potential of liquid chromatography with photoionisation detection, LC-PID. The behaviour of the PID was not as good as in gas chromatography (GC), due to the absorption of photons by the mobile phase vapour. Therefore, the minimum detection limits (MDLs) were high compared to those in GC-PID, being at the low nanogram level for, e.g., ketones, aldehydes and amides. Coupling of the PID with supercritical-fluid chromatography (SFC) using modified carbon dioxide gave more satisfactory results. For aromatic compounds like phenanthrene and pyrene MDLs were found to be 12 and 20 pg, respectively. These values were almost the same as found in GC-PID. Separation and detection of aliphatic C4-Q3 carboxylic acids and some organosulphur/phosphorus pesticides (disulfoton, ethion and sulfotepp) showed the possibility to detect several classes of compounds at the low nanogram level using methanol-modified carbon dioxide. © 1995, Taylor & Francis Group, LLC. All rights reserved.