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

Abstract

En este trabajo se realiza una evaluación estadística para conocer cómo influye la concentración del ionóforo y el disolvente mediador (DM) en la pendiente (S) y el Límite Práctico de Detección (LPD) de siete electrodos selectivos a nitrato de membrana líquida sobre un soporte conductor, los cuales tienen como ionóforo la sal cuaternaria de amonio nitrato de tetradecil amonio (NTDA) en una matriz única de cloruro de polivinilo (PVC) y en calidad de disolvente mediador los platificantes: dioctilftalato (DOP), tris-2-etilhexil fosfato (SEP), o -Nitrofenil octil éter (o-NPOE), dibutil oftalato(DBP), tributil fosfato (TBP), 3- Nitro o -Xileno (NOX), bis-2 etilhexil-Sebacate (DOS), a tres concentraciones diferentes del ionóforo y del DM o plastificante, manteniendo fija la concentración de la matriz (29% en peso). Todos los ESI construidos presentaron pendientes nernstianas, con valores de sus LPD en el rango de 10–5 – 10–6 mol/dm3 . La sensibilidad de los mismos no varía en las tres composiciones de membranas estudiadas; pero sí varía el LPD. En cuanto a los coeficientes de selectividad potenciométricos (KPot AB ) de los electrodos correspondientes a la composición de membrana 2 (7% en peso del ionóforo), para un nivel de concentración del ion interferente de 10–2 mol/dm3 , determinadas por el método de las adiciones, las mayores interferencias se obtuvieron para los aniones monovalentes ClO– 3, BrO– 3, Br– , Cl– , Bz– . Palabras clave: Electrodo selectivo de iones. Electrodo del estado sólido. Membrana del electrodo de PVC. Ionóforo. Electrodo selectivo de nitrato. Polymeric membranes on a conductive support, has been carried out in thi 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-Nitrophenyloctyl ether (o-NPOE), Tris -2-ethylhexylphosphate (TEHP), Dioctylphthalate (DOP) and Dibutylphthalate (DBP) as solvent mediators (SM). The amount of PVC employed was 29% by weightt in all sensors while three differentt concentration of SM and that of ionophore was used. Al constructed sensors presented Nernstian slopes witth values of the Practical Detection Limit (PDL) and Lower Limit of 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 of PDL changes with the composition of the membrane. The selectivity coefficient (KPot AB ) of 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 ClO– 3, BrO– 3, Br– , Cl– and Bz– (benzoate).

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 thi 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-Nitrophenyloctyl ether (o-NPOE), Tris -2-ethylhexylphosphate (TEHP), Dioctylphthalate (DOP) and Dibutylphthalate (DBP) as solvent mediators (SM). The amount of PVC employed was 29% by weightt in all sensors while three differentt concentration of SM and that of ionophore was used. Al constructed sensors presented Nernstian slopes witth values of the Practical Detection Limit (PDL) and Lower Limit of linear Response 3 (LLLR) in the range 10(-6) 10(-5) V mol/dm(3). The sensitivity of the sensors was found to be independent from composition but the values of PDL changes with the composition of the membrane. The selectivity coefficient (K-AB(Pot)) of the electrode constructed by using 7% by weight of ionophore for an interfering anion with concentration of 10(-2) mol/dm(3) was determined by using the method of additions. The principal intgesssrfering anions were found to be ClO3-, BrO3-, Be, Cl- and Bz(-) (benzoate).