The sensitne detection of organic acids in hqmd chromatographlc (LC) systems remains problematic The behavlour of a potentlometnc detector was studied m this type of analysis, usmg Ion-selectwe PVC-based hqmd membranes One membrane contamed a quaternary ammonmm salt as a earner and another contamed a hpophlhc macrocychc pentamme The selectmty and sensltmty of the two membrane types towards 20 ions was determmed usmg flov+mnJectlon expenments The flow-through detector was of the wall-jet type The response tunes of the membranes were evaluated and are discussed wth respect to then use m LC and flow-mlectlon analysis (FL41 The response tunes bvere compared urlth these obtained unth amperometnc wall-jet detectors The dd'ferent factors that determme the extent of the response tunes are discussed The membranes were used for the sensdlve detection of morgamc anions m an LC ion chromatography system For the separation of orgamc aclds, and Anunex HPX87H ion-exclusion chromatographlc column was used With the potentlometnc hqmd membrane detector, the detection hts were at least 100 times lower than the values obtamed urlth the low-wavelength UV detector that 1s normally used m these systems Typically, a detectlon hnut of 10 ng was measured for acetic acid The potential and hmltatlons of potentlometnc hquld membrane detectors m LC and FL4 are discussed Keywon& Flow mJectlon, Ion selective electrodes, Liquid chromatography, Potentlometry, Acids, Anion, Membrane electrodes,