Comportamiento de algunos parámetros de calibración de electrodos selectivos a nitrato, a diferentes concentraciones del ionóforo y del disolvente mediador.

Abstract

The statistical evaluation of seven ion selective chemical sensors (ISE) for nitrate ion determination, based on polymeric membranes on a conductive support, has been carried out in this work. This was donw in order to determine the influence of ionophore concentration and that of solvent-mediator on the slope (S) and the practical detection limit (PDL). Tetradecilammonium nitrate (TDAN) was used as ionophore, polyvinylchloride (PVC) as matrix and seven plasticizers, namely, 3-nitro-o-xylene (NOX),Tributylphosphate(TBP), Bis (2-ethylhexyl) sebacate (DOS), o-Ntrophenyloctyl ether (o-NPOE), Tris -2ethyl-hexylphosphate (TEHP), Dioctylphthalate (DOP) and Dibutylphthalate (DBP) as solvent-mediators (SM). The amount of PVC employed was 29% by weight in all sensors while three different concentration of SM and that of ionophore was used. All constructed sensors presented Nernstian slopes with values of the Practical detection Limit (PDL) and Lower Limit on Linear Response (LLLR) in the range 10-6 - 10-5 mol/dm3. The sensitivity of the sensors was found to be independent from composition but the values pf PDL changes with the composition of the membrane. The selectivity coefficient on the electrode constructed by using 7% by weight of ionophore for an interfering anion with concentration of 10-2 mol/dm3 was determined by using the method of additions. The principal intgesssrfering anions were found to be CIO-3, BrO-3, Br-, Cl- and Bz- (benzoate).