An alternative construction of a contactless conductivity detector in which semitubular instead of tubular electrodes were used is described. The electrodes are made of a strip of aluminium foil formed into a semitubular shape. They are positioned between two Plexiglass plates in a groove matching the outer diameter of a separation capillary. One Plexiglass plate is immovable, the other is free and can be detached from the immovable plate after the fixing screws are released. The separation capillary is inserted between the plates into the groove and flattened to the electrodes by the tightening of the fixing screws. This construction permits a simple exchange of the separation capillary and makes the connection of individual electrodes with the detector electronics easier and more reliable. The detector performance was tested under the electrophoretic conditions using model sample solutions of potassium chloride in the concentration range from 10 73 to 10 78 mol=L. It was shown (for K þ ion) that the operational characteristics of the detector with semitubular electrodes, namely dynamic range, 0.5-1000 mM, linear dynamic range, 5-1000 mM, limit of detection, 0.5 mM (LOD here represents the concentration from that the detector signal ceases to change with further concentration decrease) and sensitivity (1.2 mV=pg), are comparable with those for the detectors with common tubular electrodes.