A contactless conductometric detector with easily exchangeable capillary for capillary electrophoresis

An alternative construction of a contactless conductivity detector in which semitubular instead of tubular electrodes were used is described. The elec trodes are made of a strip of aluminium foil formed into a semitubular shap e. They are positioned between two Plexiglass plates in a groove matching t he outer diameter of a separation capillary. One Plexiglass plate is immova ble, the other is free and can be detached from the immovable plate after t he fixing screws are released. The separation capillary is inserted between the plates into the groove and flattened to the electrodes by the tighteni ng of the fixing screws, This construction permits a simple exchange of the separation capillary and makes the connection of individual electrodes wit h the detector electronics easier and more reliable. The detector performan ce was tested under the electrophoretic conditions using model sample solut ions of potassium chloride in the concentration range from 10(-3) to 10(-8) mol/L. It was shown (for K+ ion) that the operational characteristics of t he detector with semitubular electrodes, namely dynamic range, 0.5-1000 muM , linear dynamic range, 5-1000 muM, limit of detection, 0.5 muM (LOD here r epresents the concentration from that the detector signal ceases to change with further concentration decrease) and sensitivity (1.2 mV/pg), are compa rable with those for the detectors with common tubular electrodes.