Selectivity nitration

The Department of the Environment UK [155] has described a number of alternative methods for the determination of total oxidised nitrogen (nitrate and nitrite) in aqueous solution, while specific methods for nitrate and nitrite are also included. Among the methods for total oxidised nitrogen, one is based on the use of Devarda s alloy for reduction of nitrate to ammonia, and another uses copperised cadmium wire for reducing nitrate to nitrite, which is determined spectrophotometrically. Nitrate may also be determined spectrophotometrically after complex formation with sulfosalicylic acid or following reduction to ammonia, the ammonia is eliminated by distillation and determined titrimetrically. Other methods include direct nitrate determination by ultraviolet spectrophotometry, measurements being made at 210 nm, and the use of a nitrate-selective electrode. Details of the scope, limits of detection, and preferred applications of the methods are given in each case. 

Of special interest is the nitrate electrode, which has found many applications in quantitative analysis of nitrates in biological fluids and agricultural products. A nitrate-selective electrode [132] based on a tributyl-octadecylphosphonium ligand is also selective for perrhenate and perchlorate ions. 

Another method used for nitrate determination on dried and milled herbage employs the nitrate selective electrode. One of the first published methods was that of Paul and Carlson (1968). Other anions, especially chloride, can interfere. These authors removed chloride with silver resin, but Barker ef al. (1971) omitted the resin because it tended to foul the electrode and cause excessive drift. Normally the Cl N03 ratio is so low as not to interfere, but saline precipitation from coastal plots could affect this. The method was further modified to allow storage of extracts for up to 64 h by adding a preservative of phenyl-mercuric acetate and dioxane, both very toxic (Baker and Smith, 1969). This paper mentions the need to change the electrode s membrane, filling solution and liquid ion exchanger every 2 months to minimize chloride interference. It is easy to overlook electrode maintenance between batches of nitrate analyses, and this can lead to errors and sluggish performance. 

Hutchins RS, Bachas LG. Nitrate-selective electrode developed by electrochemically mediated imprinting doping of polypyrrole. Anal Chem 1995 67 1654-1660. 

A nitrate-selective potentiometric MIP chemosensor has been devised [197, 198]. For preparation of this chemosensor, a polypyrrole film was deposited by pyrrole electropolymerization on a glassy carbon electrode (GCE) in aqueous solution of the nitrate template. Potentiostatic conditions of electropolymerization used were optimized for enhanced affinity of the resulting MIP film towards this template. In effect, selectivity of the chemosensor towards nitrate was much higher than that to the interfering perchlorate ( o3 cio4 = 5.7 x 10-2) or iodide ( N03, r = x 10 2) anion. Moreover, with the use of this MIP chemosensor the selectivity of the nitrate detection has been improved, as compared to those of commercial ISEs, by four orders of magnitude at the linear concentration range of 50 pM to 0.5 M and LOD for nitrate of (20 10) pM [197]. 

Nitrate in water may be analyzed by a nitrate selective sensor. Chloride and bicarbonate ions at concentrations about ten times greater than nitrate interfere in this test. Sulfide, cyanide, and halide ions are eliminated by using a buffer solution containing AgS04. The buffer — boric acid at pH 3 — removes bicarbonate. 

Whilst although not technically an amidopyrrole in the sense that the previous examples, macrocycle 33 synthesised by Sessler, Ustynuk and co-workers displays a high sulfate-to-nitrate selectivity (Figure 27).26... 

To overcome these problems use is made of the now available nitrate-selective resins (Chapter 5, Dilute Solution Anion Exchange ) for which the anion affinity sequence is ... 

Figure 8.12 Leakage profile of ion residuals for chloride cycle anion exchange on a nitrate selective resin...

Advanced Condensate Polishing designs Sub-ppb ion residuals established for condensate treatments and Ultrapure water applications Nitrate selective resins Resin copolymerization - uniform bead size... 

Key Words Direct propylene epoxidation. Propylene oxide, Gold, Titanium, Propene, Au/Ti catalysts. Catalysis by gold. Titanium silicalite, TS-1, Gold/TS-1, Hydrogen peroxide, Kinetics, Design of experiments, Deposition-precipitation, Ammonium nitrate, Selective oxidation, Alkene epoxidation, Density functional theory, DFT calculations, QM/MM calculations. 2008 Elsevier B.v. 

The solvent used in the Redox process was hexone, methyl isobutyl ketone, an extractant already in use for purifying uranium ore concentrates (Chap. 5)., Hexone is immiscible with water and will extract uranyl nitrate and plutonyl nitrate selectively from fission-product nitrates if the aqueous solution has a sufficiently high nitrate ion concentration. In the Redox process, aluminum nitrate was used as salting agent because high concentrations of nitric acid would decompose the hexone solvent. 

A. Eyal and O. Kedem, Nitrate-selective anion-exchange membranes, J. Membr. Sci., 1988, 38, 101. 

A. Eyal and O. Kedem, Nitrate-selective anion-exchange membrane, J. Membr. Sci., 1988, 38, 101 T. Sata, T. Yamaguchi, K. Matsusaki, Effect of hydrophilicity of ion exchange groups of anion exchange membrane on permselectivity between anions,... 

E. B. Schalscha, T. Schirado, and I. Vergara, Flow Injection Analysis of Nitrate in Soil Extracts—Evaluation of a Nitrate-Selective Flow Electrode Method. J. Soil Sci. Soc. Amer., 45 (1981) 446. 

In the ion-exchange part, the column is packed with nitrate-selective resin in a chloride form, which prevents treating waters with a concentration of nitrates exceeding 50 mg/L. 

S. Aravamudhan and S. Bhansali, Development of micro-fluidic nitrate-selective sensor based on doped-polypyrrole nanowires. Sens. Actuat. B, 132, 623-630 (2008). 

Bendikov, T.A., Miserendino, S., Tai, Y.-C., Harmon, T.C., 2007. A parylene-protected nitrate selective microsensor on a carbon fiber cross section. Sensor. Actuat. B Chem. 123,127-134. 

Therefore, to prepare a selective anion sensor for less lipophilic anions in the series, the selective interactions between the ionophores and the targeted anion should be considered. Truly selective nitrate electrodes were developed by the electrochemical deposition of PPy onto glassy carbon electrodes in the presence of NaNOa [131]. As seen in Figure 8.79, the selectivity pattern of PPy(N03 ) electrodes exhibited a significant deviation firom the Hofineister series. The electrodes showed selectivity especially for nitrate and thiocyanate, while the commercially available nitrate-selective electrodes were affected by the more lipophilic anions including iodide and perchlorate. 

E. Lockridgeand. S. Fritz, Determination of water using nitrate selective ion-exchange resin, U. S. Patent... 

Georgeaud V, Diamand A, Bormt D, Grange D, Coste M (2011) Electrochemical treatment of wastewater polluted by nitrate selective reduction to N 2on Boron-Doped Diamond cathode. Water Sci Technol 63 206-212... 

G.A. Alvarez-Romero, M.E. Palomar-Pardave, M.T. Ramirez-Silva, Development of a novel nitrate-selective composite sensor based on doped polypyrrole. Anal. Bioanal. Chem. 387 (2007) 1533-1541. 

The selectivity of the molecularly-imprinted NO3 ISE is much improved versus those based on the quatemaiy ammonium salts. For example, the log for perchlorate in this case is -1.24 relative to nitrate (fixed interference method). Thiocyanate, which was also a major interferent for the quatemaiy ammonium salt-based ISE, with log of 1.7 (24 is better discriminated against by the molecularly-imprinted ISE. For this nitrate-selective ISE the most important interference is chloride. 

A NOx gas sensor constructed from a molecularly-imprinted nitrate-selective electrode has also been developed in our laboratory (30). This gas sensor is produced by placing the nitrate-selective electrode behind a gas-permeable membrane. Also, there is a buffer compartment present between the gas-permeable membrane and the ISE. As before, NOx species that pass through the gas-permeable membrane are trapped in the buffer compartment as NO2 and NOs . In this case, the electrode responds proportionately to the amount of nitrate in the buffer, rather than nitrite as in the NOx sensor described above. The gas sensor based on the N03 -selective electrode offers advantages over the Severinghaus arrangement similarly to the other aforementioned gas sensors (SO2 and NOx). Detection limits for this gas sensor were on the order of 1x10 M, with response characteristics being retained for over 80 days. This lifetime is consistent with lifetimes of the molecularly-imprinted nitrate-selective electrodes. 

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