A novel class of capillary electrophoresis probes and a method of employing the same are described. The novel class of capillary electrophoresis probes are comprised of one or more vinylogous carboxylic acid compounds or their derivatives. In another aspect of the present invention, a method of detecting ions in water by capillary electrophoresis is provided wherein: water is introduced into a capillary filled with an electrolyte which contains UV absorbing species comprised of one or more vinylogous carboxylic acid compounds. An electric voltage is applied along the capillary to cause ions present in the water to move along the capillary and separate. The ions displace the UV absorbing species and are detected indirectly by a UV/visible light photometric detector.