Ammonium ion sensor based on SiO2/ZrO2/phosphate-NH4+ composite for quantification of ammonium ions in natural waters

Abstract

Um eletrodo íon seletivo foi construído e avaliado para determinação de íons amônio em águas naturais. O eletrodo consiste de uma pasta de carbono com o compósito SiO 2 /ZrO 2 / fosfato-NH 4 + obtido pelo processo de sol-gel. O eletrodo exibe uma resposta sub-Nenstiana para concentrações entre 7,7×10-7 e 4,0×10 -2 mol L -1 e um limite de detecção de 1,58×10 -7 mol L -1 (8,5×10 -3 ppm). A resposta do eletrodo foi rápida (1 minuto). Os coeficientes de seletividade K pot A,B para os diversos íons geralmente presentes em águas naturais foram determinados pela aplicação do matched potential method. O método potenciométrico com o eletrodo íon seletivo foi validado pelo método de Berthelot (método padrão) pela determinação de íons amônio em águas naturais. O eletrodo íon seletivo provou ser satisfatório para o controle de qualidade de águas naturais.Ion selective-electrode was constructed and evaluated for determination of ammonium ions in natural waters. The electrode consists of paste carbon with the composite SiO 2 /ZrO 2 /phosphate-NH 4 + obtained through sol-gel process. The electrode exhibits a sub-Nernstian response for ammonium concentrations between 7.7×10 -7 and 4.0×10 -2 mol L -1 and a detection limit of 1.58×10 -7 mol L -1 (8.5×10 -3 ppm). The electrode response for ammonium was fast (1 minute). The selectivity coefficients K pot A,Bfor several ions usually present in natural waters were determined applying the matched potential method. The potentiometric method with the ion selective electrode was validated by the Berthelot method (standard method), through the determination of ammonium ions in natural waters. The ion selective-electrode proved suitable for routine quality control of natural waters by potentiometry.Keywords: ammonium ion sensor, potentiometric sensor, natural waters IntroductionThe presence of ammonium ions in rivers and lakes can be associated in most cases to pollution caused by livestock, intensive agriculture and mainly, nowadays, to liberation of domestic sewage in courses of superficial waters in an indiscriminate way and in larger and larger amounts.Ammonium ion sensor is a useful tool in environmental pollution control, 1 food and clinical analysis 2-4 and other industrial applications.5 Among the ion sensors, ammonium sensor is also used more frequently as potentiometric biosensor in which enzymes or microbial cells are immobilized on the surface of the sensor. 6,7 Due to the many applications of the ammonium ion sensors, design of solid-state sensor for ammonium and its fabrication through simple procedure are desirable. 8Inorganic ion exchangers are characterized by high thermal stability and resistivity towards strong oxidizing agents and mineral acids. Recently the SiO 2 /ZrO 2 / phosphate composite was prepared by the sol-gel process, 9 which allies the good properties of ionic exchange of the zirconium(IV) phosphate 10,11 in a matrix of mixed oxide, SiO 2 /ZrO 2 high and homogeneously dispersed. This composite presents high superficial area, phosphate groups on the surface o...

Why ammonium detection is particularly challenging but insightful with ionophore-based potentiometric sensors – an overview of the progress in the last 20 years

“…Coutinho and co-workers published the analytical performances and applications of a GCE modified with SiO 2 /ZrO 2 / phosphate-NH 4 + composite. 100 This composite presented reproducible exchange properties toward NH 4 + in the pH range from 6 to 7.5, which may be an inconvenience for certain applications. In addition, again, the selectivity coefficient for K + did not improve the values as compared to those reported for electrodes analyzed in the earlier sections (see Table 3).…”

Clinoptilolite‐based Conductometric Sensors for Detection of Ammonium in Aqueous Solutions

“…Some of these state ranges and limits of detection that appear to outperform the current sensor. For instance, the potentiometric sensor based on SiO 2 /ZrO 2 /phosphate-NH 4 composite [15] had LOD of 0.158 μM and, thus, can be viewed as an exceptionally sensitive device. To prepare the SiO 2 / ZrO 2 /phosphate composite alone, however, a long-term (only incubation time totaled 55.5 h) and sophisticated multi step approach was used [17].…”

“…Within the NH þ 4 -selective ISEs/sensors one may distinguish two main groups of materials used for the ammonium recognition predominantly. They are namely (1) organic and bioorganic polymers [9][10][11][12][13], and (2) inorganic crystalline solids [14][15][16]. Whereas the first group was pioneering in sensor application and has already contributed to a number of advantageous ammonium sensing devices, the materials of the second group still show vast potentialities and keep on raising interest for their exploration.…”

Carbon paste electrodes in the new millennium

“…Various modifications of carbon paste were applied in potentiometric sensors for copper [286][287][288][289][290][291][292], silver [97, 153,293], mercury [94-296], lead [297], arsenic [97,298], antimony [299], bismuth [300], cobalt [301], osmium [302], aluminium [107], lithium [303], ammonium [304], halides and pseudo-halides [305][306][307][308], and sulphate ions [309]. Some of them [97,302] were applied to monitor titrations based on ion-pair formation principles described and discussed in detail previously [310].…”