A novel thin-layer electrolysis flow cell based on the ion transfer at the liquid vertical bar liquid interface was proposed for the absolute determination of a sub-nanomole ionic species. By using the conducting polymer-coated electrode as an electrode in organic phase, the flow cell was developed as a laminate structure with a thin aqueous layer and a thin organic layer, which were set between an Ag/AgCl electrode and the conducting polymer-coated electrode. Its simple structure made it possible to miniaturize the flow cell, and the required sample volume was reduced to only 1 mu l. In the present electrolysis cell, both quantitative extraction and quantitative back-extraction of total amount of the ionic species were achieved. This advantage was applied to two methods for absolute determination. One is that by flow injection method, and the other is that by pre-concentration into the thin organic phase followed by back-extraction of the species from the thin Org to the thin aqueous phase (i.e., the stripping technique). In these methods, coulometrical determination of sub-nanomol ionic species was realized without a calibration curve. (C) 2013 Elsevier B.V. All rights reserved.