The potential changes were monitored during symmetric conditioning and asymmetric conditioning of the polyvinyl chloride membrane containing sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB) or sodium tetraphenylborate (NaTPB) in dodecyltrimethylammonium chloride (DTMACl) solutions at 10(-5.0)-10(-3.5) mol dm(-3). A slow potential increase, which reflected a change in local concentration of DTMX+ in the conditioning solution proximate to the membrane, was observed for NaTFPB at a DTMACl concentration of 10(-5.0)-10(-4.5) mol dm(-3). For NaTFPB at a DTMACl concentration of 10(-4.0)-10(-3.5) mol dm(-3) or for NaTPB, the potential decreased after a rapid increase reflecting the change in DTMA(+):Na+ ratio as a counter ion in the membrane by the ion-exchange. In asymmetric conditioning, the leakage of DTMA(+) into the inner solution overlapped with the change in DTMA(+):Na+ ratio for NaTPB but was delayed from the change for NaTFPB. Some criteria for completion of the conditioning are described. (C) 2013 Elsevier B.V. All rights reserved.