Potentiometric response of polymeric liquid membranes based on quaternary ammonium salts for nitrate ion determination

Polymeric liquid membranes are prepared using 3-nitro-o-xylene (NOX), tri-butylphosphate (TBP), bis-(2-ethylhexyl) sebacate (DOS), o-nitrophenyloctyl ether (o-NPOE), tris-2-ethylhexylphosphate (TEHP), dioctylphthalate (DOP) and dibutylphthalate (DBP) as plasticizers, and they have been used as sensors for nitrate ion, employing tri-octylmethyl ammonium chloride (TOMACI) as ionosphere and poly(vinyl chloride) (PVC) as matrix. The sensors showed Nernstian slopes with values of the practical detection limit (PDL) and lower limit of linear response (LLLR) in the concentration range of 10(-6)-10(-5) mol/dm(3). All the electrodes built showed a fast and stable response of 15 seconds. Wide working pH ranges, especially in the alkaline region, were observed. The response of the sensors was determined in relation to the lipophilicity of each plasticizer used as solvent-mediator, its dielectric constant (e(Gamma)), polarity and viscosity.