An ex-situ potentiometric titrations were normally performed using an oxidation/reduction potential (ORP) electrode to monitor the electrochemically generated active electron mediators, either oxidants or reductants, in a mediator generation plant. In the present investigation, an attempt was made to monitor electron mediator [Ni1+(CN)(4)](3-) (Ni(I)) in-situ in a high electrolyte concentration (9 M KOH) during its electrochemical generation. A ring type flow cell developed using a 0.6 cm diameter electrode was tested on a standard redox couple of [Fe3+(CN)(6)](3-) (Fe(III))/[Fe2+(CN)(6)](4-) (Fe(II)) at different ratios during solution flow. The found results suggested that direct determination of an electrochemically prepared electron mediator is possible using a potentiometric method. A periodical potential change in the in-situ linear sweep voltammetry of electrogenerated Ni(I) during its electrochemical generation allowed the direct determination of electrogenerated Ni(I) by the ring type flow cell. A calibration plot derived from chemically synthesized Ni(I) using an ex-situ potentiometric titration or UV-visible spectra was used to monitor electrogenerated Ni(I) by the in-situ method. The electrochemically generated Ni(I) concentration detected in the 0-4.5 mmol/L region that followed non-Nernstian behavior. A change in the Ni(I) concentration during N2O removal at the scrubber column suggesting that air pollutant removal can be monitored using the in-situ flow sensor cell, once how many electron involved in the removal process. (C) 2018 Elsevier Ltd. All rights reserved.