Apparatus and method for detecting current or potential generated in a liquid sample suitable for use in a chromatography or other liquid sample analytical system. One embodiment is an electrolytic ion transfer device (62) with a signal detector (32) in communication with the electrodes (28a, 28b) of the transfer device. Another is a combination ion transfer device (62) /electrolyte generator (63). Another substitutes a detector for the ion transfer device in the combination.