Sensors for nitrite

Electrochemical Sensors for Nitrite and Nitric Oxide Determination 492... 

Other early work in this field included the use of tetrakis(p-aminophenyl)-porphyrin (Fig. 7a), which was electrodeposited onto glassy carbon and showed a near-Nernstian response to iodide [76]. Electrodeposited methylthiophene-methylpyrrole copolymer was deposited and shown to give a near-Nernstian response to bromide [77]. Pyrrole-3-boronate (Fig. 7b) could be deposited to give films with a good response and marked selectivity to fluoride [78]. A cobalt aminophthalocyanine could also be electropolymerised to give a good sensor for nitrite [79] or sulphide ion [80]. 

V. Biagiotti, F. Valentini, E. Tamburri, M.L. Terranova, D. Moscone and G. Palleschi, Synthesis and characterization of polymeric films and nanotubule nets used to assemble selective sensors for nitrite detection in drinking water. Sens. Actuat. B, 122, 236-242 (2007). 

Santos WJR, Sousa AL, Luz RCS et al (2006) Amperometric sensor for nitrite using a glassy carbon electrode modified with alternating layers of ironflll) tetra-(lV-methyl-4-pyridyl)-porph5oin and cobalt(II) tetrasulfonated phthalocyanine. Talanta 70 588-594... 

Raoof JB, Ojani R, Ramine M (2009) Voltammetric sensor for nitrite determinatitm based on its electrocatalytic reduction at the surface of p-duroquinone modified carbon paste electrode. J Solid State Electrochem 13 1311-1319... 

The first interest in the electroreduction of N02 or NO catalyzed by metal complexes is to model the activity of nitrite reductase enzymes.327 There is also an extensive growth in studies related to the development of metal complex-based electrochemical sensors for NO determination in biological and environmental samples 328 329 Nitrate disproportionates to nitric oxide and nitrate in aqueous solution. 

A biosensor for nitrite [24] was recently proposed for monitoring nitrite concentration in activated sludge exposed to oxic/anoxic cycles. The biosensor contains bacteria reducing only N02 into N20, which is subsequently monitored by a built-in electrochemical sensor. Up to 90% of the response is obtained in about 1 min, and the detection limit is around 5 mg L1, a concentration sufficient for treatment process monitoring. Unfortunately, the maximum operational lifetime of the N02 biosensor is 6 weeks and some problems may occur with time. 

In potentiometric sensors, an electrical potential between the working electrode and a reference electrode is measured at zero current conditions in a solution containing ions that exchange with the surface. The first potentiometric MIP sensor was prepared in 1992 by Vinokurov (1992). The substrate-selective polyaniline electrode was electrosynthesized with polypyrrole, polyaniline, and aniline-p-aminophenol copolymers. The development of an MIP-based potentiometric sensor was reported in 1995 by Hutchins and Bachas (1995). This potentiometric sensor has high selectivity for nitrite with a low detection limit of (2 + l)x 10 M (Fig. 15.10). 

In addition to the summary registration of nitrifiable substances, it is also possible to quantify N-compounds selectively by using microbial sensors. Microbial sensors for the monitoring of ammonium ions, ammonia, nitrite, nitrate and urea have been described (see Table 9). Nitrifiers are generally used, but not only (see also Sect. 3.2.4). 

As earlier reported for electrochemical sensing, often the active chromo-phore will be dispersed in a polymeric matrix. For example, Mohr and Wolfbeis reported a nitrate sensor [121] where the active chromophore is a rhodamine B dye which had been modified with an octadecyl side chain to render it hydrophobic and prevent leaching. The dye was dispersed in a plasticised PVC membrane containing a hydrophobic anion carrier (tridodecylmethylammo-nium chloride). On exposure to nitrate, the fluorescence of the dye increased. This membrane, however, only displayed Hofmeister-type selectivity and was also affected by pH. Replacing the quaternary ammonium anion carrier with a palladium phospine chloride carrier led to selectivity for nitrite [ 122], probably due to a preferential interaction between Pd and nitrite ion. 

Although the ISEs based on cobyrinates have good selectivity for nitrite over several anions, they also respond to salicylate and thiocyanate. To eliminate this interference, the nitrite-selective electrode based on ionophore 2 was placed behind a microporous gas-permeable membrane (GPM) in a nitrogen oxide gas-sensor mode (75). NOx was generated from nitrite in the sample at pH 1.7 and, after crossing the GPM, was trapped as nitrite by an internal solution that was buffered at pH 5.5 (0.100 M MES-NaOH, pH 5.5, containing 0.100 M NaCl). The internal solution was "sandwiched" between the nitrite-selective electrode and the GPM. 

Electrocatalytic dopants (heteropolyanions) have also been incorporated into conducting polymers with a view to developing sensors for detection of nitrite (45a) or nitrogen monoxide (45b). 

Doherty, A.P., Forster, R.J., Smyth, M.R. and Vos, J.G. (1991) Development of a sensor for the detection of nitrite using a glassy-carbon electrode modified with the electrocatalyst [Os(bipy)2(PVP)10Cl] Cl. Analytica Chimica Acta, 255 (7), 45-52. 

Phosphorus and nitrogen sensors A very important area where the use of sensors for process analysis has gained much interest is in wastewater monitoring. In particular, the use of analyzers for monitoring of nutrients (nitrate, nitrite, ammonium, and phosphate) and organic matters is of considerable interest. 

Zou and coworkers assembled a porphyrin-Cso dyad able to work as an electrochemical sensor for sensing hydrogen peroxide and nitrite [269]. Ortho and para isomers were synthesized and tested showing good stability and reproducibility as sensors for river water and rainwater. In Scheme 14.15 the structure of one of the isomers used in this paper is reported. 

Wu H, Fan S, Jin X, Zhang H, Chen H, Dai Z, Zou X. Construction of a zinc potphyrin-fullerene-derivative based nonenzymatic electrochemical sensor for sensitive sensing of hydrogen peroxide and nitrite. Anal Chem 2014 86 6285-90. 

Sensor for the simultaneous determination of nanomolar concentrations of nitrite, nitrate, and ammonia in... 

Rajesh, S., Sethy, N.K., Bhargava, K., Ilavazhagan, G., Singh, S.K., Karunakaran, C., 2011. Electrochemical sensor for simultaneous measurement of nitrite and superoxide anion radical using superoxide dismutase-mimetic manganese(III) tetrakis(l-methyl-4-pyridyl)porphyrin on polypyrrole matrix. Sens. Lett. 9, 1682-1688. 

Maduraiveeran, G., Manivasakan, P.. and Ramaraj, R. (2011) Silver nanoparticles embedded three dimensional silicate sol gel matrix modified electrode for nitrite sensor application. Int J. NanotechnoL,... 

---