Nitrite In Aqueous Solution Research Articles

A New, Rapid, Colorimetric Chemodosimeter, 4-(Pyrrol-1-yl)pyridine, for Nitrite Detection in Aqueous Solution.

With increasing concerns over environmental impact and overall health of both the environment and its people, a need to quantify contaminants is of the utmost importance. Chemosensors with low detection limits and a relative ease of application can address this challenge. Nitrite ions are known to be detrimental to both the environment and human health. A new colorimetric chemodosimeter has been prepared from the homolytic photochemical cleavage of a reaction between pyrrole and pyridine. The product, 4-(pyrrol-1-yl)pyridine, yields a limit of detection of 0.330 (±0.09) ppm for the detection of nitrite in aqueous solution, employing a colorimetric change from yellow to pink. It is also highly selective for nitrite when various competitive anions such as SO3 2-, NO3 -, PO4 3-, SO4 -2, Cl-, F-, I-, Br-, AcO-, and CN- are present in great excess. The molecule's especially high sensitivity to nitrite is apparently the result of a complex supramolecular mechanism, characterized by both dynamic light scattering of the aggregate and the Tyndall effect. Consequently, this new sensor provides a simple, low-cost way to rapidly detect nitrite anions in aqueous solution.

Remarkable fluorescence enhancement of acridine orange and rhodamine B through immobilization on zirconia nanotube array film and its application on nitrite sensing

Zirconia nanotube array films (ZNAF) prepared by anodic oxidation method were used as immobilization materials for acridine orange (AO), rhodamine B (RB) and AO-RB systems. A comparative study on their fluorescence emission intensity, fluorescence resonance energy transfer (FRET) and fluorescence detection of nitrite in aqueous solutions and on immobilization films with ZNAF as carriers was carried out. Results demonstrate that the solution pH values and immobilization on ZNAF have a great influence on the performance of these fluorescent molecules. Compared with aqueous solutions, the fluorescence emission intensity of AO and RB is considerably increased by immobilization, which is 8.0 and 4.2 times higher than the original, respectively. The energy transfer efficiency (E) of the AO-RB system increases from 40.9 % to 84.8 % by loading it on ZNAF. Moreover, after immobilization onto ZNAF, the fluorescence detection performance of nitrite is also significantly improved. The limit of detection decreases from 0.95 ng/mL to 0.22 ng/mL and the sensitivity increases from 939.18 to 15,031.68 mL/µg through loading AO onto ZNAF.

Formation of N-Nitrosamines by Reaction of Secondary Dialkylamines with Trace Levels of Nitrite in Aqueous Solution: An Automated Experimental and Kinetic Modeling Study Using Di-n-butylamine

Formation of <i>N</i>-Nitrosamines by Reaction of Secondary Dialkylamines with Trace Levels of Nitrite in Aqueous Solution: An Automated Experimental and Kinetic Modeling Study Using Di-<i>n</i>-butylamine

Comparing the Reactivities of Methanol and Methanediol in the Photolysis of Aqueous Nitrite Solution.

Ultraviolet irradiation of aqueous nitrite (NO2-) quickly generates hydroxyl (OH) and nitric oxide (NO) radicals, which are subsequently consumed concomitantly with the generation of NxOy species. Recently, dissolved formaldehyde (CH2O) in aqueous solution (e.g., methanediol, CH2(OH)2), has been regarded as the precursor in the formation of atmospheric formic acid (HCOOH) via the reaction with OH and cascading processes ( Nature2021, 593, 233-237). In this work, a step-scan Fourier transform interferometer was utilized to monitor the time-resolved difference infrared spectra of NaNO2 aqueous solution in the presences of methanediol and methanol upon pulsed irradiation at 355 nm. The fates of the dinitrogen trioxide (N2O3), generated via a series of reactions of OH, NO, and NO2-, differed in the presences of CH2(OH)2 and CH3OH. The decay of N2O3 via hydrolysis with H2O was retarded more by CH3OH than by CH2(OH)2. The monohydroxyl group of CH3OH does not behave like the hydroxyl group of water, whereas the two hydroxyl groups of CH2(OH)2 can be treated as a water reservoir via the quick equilibrium between H2O and CH2O, further facilitating the hydrolytic solvation reaction of N2O3. The observed difference in reaction kinetics involving hydration should be thoroughly taken into consideration in formaldehyde-related aqueous reactions.

Fluorine and nitrogen co-doped near-infrared carbon dots for fluorescence "on-off-on" determination of nitrite.

A fluorescence "on-off-on" strategy was established for the determination of nitrite in aqueous solution based on fluorine and nitrogen co-doped near-infrared carbon dots (NIR-CDs). NIR-CDs were prepared via one-step hydrothermal method by using N-(4-aminophenyl)-acetamide and 4,5-difluorobenzene-1,2-diamine as precursors. The photoluminescence quantum yield of NIR-CDs reaches to 17.4%, and the optimal emission peak of NIR-CDs is 675nm under excitation of 530nm. The Stokes shift of NIR-CDs (145nm) is higher than that ofsome CDs with longer emission wavelengths. The red bathophenanthroline disulfonic acid (BPS)-Fe2+ complex can quench the fluorescence of NIR-CDs via inner filter effect and static quench modes. Nitrite can oxidize Fe2+ to produce Fe3+ in acidic environment, resulting in not only the formation of colorless and unstable BPS-Fe3+ complex but also the fluorescence recovery of NIR-CDs. This fluorescence "on-off-on" phenomenon also comes with the color variation of the mixture, resulting in both the fluorescence and the visual determination of nitrite. Under optimal conditions, this assay exhibits a good linear range from 1 to 50μM and a low detection limit of 0.056μM for nitrite determination. The method showed good applicability for nitrite determination in soil extract, human urine, and water samples with acceptable results. A convenient fluorescence "on-off-on" strategy for nitrite detection based on fluorine and nitrogen co-doped near-infrared carbon dots (NIR-CDs) and bathophenanthroline disulfonic acid (BPS)-Fe2+ complex was innovatively established. This probe showed a low detection limit of 0.056μM for nitrite in authentic samples, which offered a new sight for fluorescent and visual detection of nitrite in environmental protection and human health areas.

A novel highly specific colorimetric fluorescent probe for the detection of nitrite in aqueous solution.

Developing an effective method for the detection of nitrite (NO2 - ) ions in the natural environment especially in environmental waters and soils is very necessary, since they will cause serious damage to human health once excess NO2 - ions enters the human body. Therefore, a new colorimetric fluorescent probe NB-NO2 - for determining NO2 - ions was designed, which possesses good water-solubility and satisfactory selectivity over other common ions for NO2 - ions. The addition of NO2 - ions changed the color of solution from blue to colorless seen by the naked-eye. Furthermore, through test and calculation, the detection limit of the probe NB-NO2 - is 129 nM. Based on the earlier excellent characteristics, the probe NB-NO2 - was successfully used for monitoring NO2 - ions in environmental waters and soils.

Highly selective colorimetric fluorescent probe for detecting nitrite in aqueous solution

Nitrite (NO2− ions) is a common pollutant in water and soil environment. Developing a rapid and accurate detection method for NO2− ions is always an important task. Herein, a switch-off colorimetric fluorescent probe P-NO2− was presented as the specific monitoring of NO2− ions in aqueous media. Once NO2− ions was added to the probe P-NO2− solution, the solution color changed very quickly, which was from yellow to colorless. And, the fluorescent intensity (580 nm) decreased obviously. The probe P-NO2− could test NO2− ions quantitatively (0.5–10 μM), and the detection limit was 75 nM according to 3σ/slope. Moreover, this new probe could also be used to determinate NO2− ions in the soil solution samples, river and lake water.

Using Diazotization Reaction to Develop Portable Liquid-Crystal-Based Sensors for Nitrite Detection.

A liquid-crystal (LC)-based sensor for detecting nitrite in aqueous solutions was developed using a diazotization reaction as the sensing mechanism. First, tetradecyl 4-aminobenzoate (14CBA) was synthesized and doped into a nematic LC, i.e., 4-cyano-4′-pentylbiphenyl (5CB). When the LC mixture was cast on a glass substrate and then immersed into an aqueous solution without nitrite, the orientation of LC was planar and the LC image was bright. In the presence of nitrite, it reacted with alkylanilines to give corresponding diazonium ions with a positive charge, which aligned at the LC/aqueous interface to cause homeotropic orientation of LC. As a result, a bright-to-dark transition of the LC image was observed. The limit of detection (LOD) of this system for nitrite is 25 μM with high selectivity. In addition, this system can work in environmental water samples such as tap water and pond water. Finally, we demonstrated that the optical signals of LC can be measured and recorded using a built-in digital camera of a smartphone, suggesting the portability of this system for on-site applications.

Wind-Driven Radial-Engine-Shaped Triboelectric Nanogenerators for Self-Powered Absorption and Degradation of NOX.

As one of the major air pollutants, NOX is rather challenging to remove. The main treatment method is catalytic reduction with plenty of reducing agents, which lacks any effective control in an open air environment such as urban spaces. It is necessary to seek a self-powered electrochemical process for environmental treatment. The triboelectric nanogenerator (TENG), a developing technology with various advantages, is widely used in energy and environmental monitoring and cleaning. In this work, a radial-engine-shaped TENG system with five stacked TENGs is designed to synchronously absorb NOX and degrade its main enrichment forms of nitrate and nitrite in aqueous solution. In addition, the system possesses inherent phase differences and outputs continuous direct current after rectification. Moreover, we demonstrated that, driven by artificial wind at a speed of 6 m/s, the NOX generated by a chemical method was effectively degraded by the radial-engine-shaped TENG system.

Impregnation of Graphene Quantum Dots into a Metal-Organic Framework to Render Increased Electrical Conductivity and Activity for Electrochemical Sensing.

Graphene quantum dots (GQD) with an average size of 3.1 nm were incorporated into a mesoporous porphyrinic zirconium-based metal-organic framework (MOF) by direct impregnation to render the donor-acceptor charge transfer from GQDs to porphyrinic linkers. The hybrid material still possesses around half porosity of the pristine MOF and shows a 100-fold higher electrical conductivity compared to that of the parent MOF. By utilizing the porphyrinic linkers as catalytically active units, the GQD-MOF material exhibits a better electrochemical sensing activity toward nitrite in aqueous solutions compared to both the pristine MOF and GQD.

Intramolecular Hydrogen Bonding Facilitates Electrocatalytic Reduction of Nitrite in Aqueous Solutions.

This work reports a combined experimental and computational mechanistic investigation into the electrocatalytic reduction of nitrite to ammonia by a cobalt macrocycle in an aqueous solution. In the presence of a nitrite substrate, the Co(III) precatalyst, [Co(DIM)(NO2)2]+ (DIM = 2,3-dimethyl-1,4,8,11-tetraazacyclotetradeca-1,3-diene), is formed in situ. Cyclic voltammetry and density functional theory (DFT) calculations show that this complex is reduced by two electrons, the first of which is coupled with nitrite ligand loss, to provide the active catalyst. Experimental observations suggest that the key N-O bond cleavage step is facilitated by intramolecular proton transfer from an amine group of the macrocycle to a nitro ligand, as supported by modeling several potential reaction pathways with DFT. These results provide insights into how the combination of a redox active ligand and first-row transition metal can facilitate the multiproton/electron process of nitrite reduction.

Nanocomposite of magnetic nanoparticles/graphene oxide decorated with acetic acid moieties on glassy carbon electrode: A facile method to detect nitrite concentration

Herein, iron oxide magnetic nanoparticles/graphene oxide decorated with acetic acid moieties (Fe3O4/GO/COOH) was synthesized and applied to fabricate a novel nitrite sensor in aqueous solutions (Fe3O4/GO/COOH/GC electrode). Acetic acid moieties were incorporated through nucleophilic reaction of chloroacetic acid with hydroxyl or epoxy groups on the surface of graphene oxide. The morphologies and compositions of fabricated nanomaterials were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy (FTIR). The Electrochemical performance of Fe3O4/GO/COOH/GC electrode was evaluated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry techniques (DPV). The Fe3O4/GO/COOH/GC electrode was employed for the determination of nitrite in aqueous solutions. The DPV results showed a linear response of modified electrode with increasing concentration of nitrite in the range of 1–85μM and 90–600μM with a correlation coefficient of 0.99. The Fe3O4/GO/COOH/GC electrode displayed a considerable sensitivity towards nitrite detection with a detection limit of 0.37μM. Our results suggest the modified electrode as an easy to use and inexpensive candidate for analysis of nitrite concentrations, especially in real samples.

A novel electrochemical sensor based on silver/halloysite nanotube/molybdenum disulfide nanocomposite for efficient nitrite sensing

In the present study, the silver/halloysite nanotube/molybdenum disulfide (Ag/HNT/MoS2) nanocomposite was successfully synthesized. For this purpose, the lumen of HNTs was firstly modified by silver to generate Ag nanorods via chemical process and then the MoS2 layers deposited on the Ag/HNT nanocomposite by hydrothermal method. The characterization of Ag/HNT/MoS2 nanocomposite were investigated by field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses. The nanocomposite modified carbon paste electrode (CPE) was applied for the electrocatalytic detection of nitrite in aqueous solutions. It was demonstrated that the treatment of HNTs with Ag and MoS2 materials enhanced the catalytic performance of modified CPE. At optimal experimental conditions, the designed sensor displayed remarkable sensing ability toward nitrite oxidation, offering a good linearity from 2 to 425 µM. The limit of detection (LOD) of the proposed strategy was estimated to be 0.7 µM based S/N = 3. The good reproducibility, acceptable stability, fast response time and anti-interference performance of the proposed assay suggests that the modified CPE has great potential working as a nitrite electrochemical sensor for environmental applications.

Artifactual degradation of secondary amine-containing drugs during accelerated stability testing when saturated sodium nitrite solutions are used for humidity control

Accelerated stability studies of pharmaceutical products are commonly conducted at various combinations of temperature and relative humidity (RH). The RH of the sample environment can be controlled to set points using humidity-controlled stability chambers or via storage of the sample in a closed container in the presence of a saturated aqueous salt solution. Herein we report an unexpected N-nitrosation reaction that occurs upon storage of carvedilol- or propranolol-excipient blends in a stability chamber in the presence of saturated sodium nitrite (NaNO2) solution to control relative humidity (∼60% RH). In both cases, the major products were identified as the corresponding N-nitroso derivatives of the secondary amine drugs based on mass spectrometry, UV–vis and retention time. These degradation products were not observed upon storage of the samples at the same temperature and humidity but in the presence of saturated potassium iodide (KI) solution (∼60% RH) for humidity control. The levels of the N-nitrosamine derivatives varied with the pH of various NaNO2 batches. The presence of volatile NOx species in the headspace of a container containing saturated NaNO2 solution was confirmed via the Griess assay. The process for formation of the N-nitrosamine derivatives is proposed to involve volatilization of nitric oxide (NO) from aqueous nitrite solution into the headspace of the container followed by diffusion into the solid drug-excipient blend and subsequent reaction of NOx with the secondary amine.

Photocatalytic conversion of nitrite in aqueous solution over nanocomposite photocatalyst Er3+:Y3Al5O12/BiPO4 using different photosources

Abstract Three crystal phases of BiPO 4 (HBIP, nMBIP and mMBIP), corresponding photocatalysts (Er 3+ :Y 3 Al 5 O 12 /HBIP, Er 3+ :Y 3 Al 5 O 12 /nMBIP and Er 3+ :Y 3 Al 5 O 12 /mMBIP) and their nanocomposite photocatalyst (Er 3+ :Y 3 Al 5 O 12 /(H-nM-mM)BIP) were prepared by hydrothermal, ultrasonic dispersion and liquid boiling methods. The prepared photocatalysts were characterized by X-ray diffractometer (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectra (DRS). The catalytic activity of prepared photocatalysts was evaluated via photocatalytic conversion rate of nitrite under ultraviolet-light, visible-light and simulated solar-light irradiations. These three photocatalysts all exhibited excellent performance under simulated solar-light irradiation and reached 85.36%, 84.42% and 78.53% conversion rates, respectively, for Er 3+ :Y 3 Al 5 O 12 /mMBIP, Er 3+ :Y 3 Al 5 O 12 /nMBIP and Er 3+ :Y 3 Al 5 O 12 /HBIP. Particularly, Er 3+ :Y 3 Al 5 O 12 /(H-nM-mM)BIP was also found to play a high catalytic activity, resulting in 78.68%, 70.04% and 82.57% conversion rates, respectively, under ultraviolet-light, visible-light and simulated solar-light irradiation. In addition, the study of used times showed that the prepared photocatalysts can be effectively recycled without an apparent inactivation on the photocatalytic activity. This research may provide a potential way for converting nitrite and other contaminants by utilizing solar energy efficiently.

Novel approach for the ammonium removal by simultaneous heterotrophic nitrification and denitrification using a novel bacterial species co-culture.

Agricultural activities lead excessive emission of ammonia nitrogen in the environment and can profoundly interfere the equilibrium of the natural ecosystems leading to their contamination. Actually, the biological purification of wastewaters is the most adopted technique thanks to its several advantages such as high performance and low energy consumption. For this reason, two novel strains of Alcaligenes sp. S84S3 and Proteus sp. S19 genus were isolated from an activated sludge and applied in the treatment of ammonium and nitrite in aqueous solution. Under the optimum operating conditions of temperature (30 °C), pH (7), carbon substrate (2 g/L of glucose) and duration of incubation time (69 h), the strain Alcaligenes sp. S84S3 could oxidize 65% of the ammonium as high as 272.72 mg-NH4(+)/L. Moreover, during 48 h, the nitrate reduction rate performed by the strain Proteus S19 was about 99 % without production of nitrite intermediate (negligible concentration). Moreover, the coculture of the strains Alcaligenes sp. S84S3 and Proteus sp. S19 could eliminate 65.83% of the ammonium ions without production of toxic forms of nitrogen oxides during a short time of incubation (118 h) at the same operational conditions with providing the aeration in the first treatment phase. The coculture of our isolated strains is assumed to have a good potential for nitrification and denitrification reactions applied in the treatment of wastewater containing ammonium, nitrite and nitrate. As a result, we can consider that the mixed culture is a practical method in the treatment of high-strength ammonium wastewater with reducing of sludge production.

Nitrite reduction on a multimetallic porphyrin/polyoxotungstate layer-by-layer modified electrodes

Electro and photoelectrochemical reduction of nitrite in aqueous solution was studied using a multielectrocatalysts modified ITO electrode. ITO modification was carried out using the layer-by-layer (LBL) method, where sequential electrostatic assemblies were formed using a μ-(meso-5,10,15,20-tetra(pirydil)porphyrin)tetrakis{bis(bipyridine)chloride ruthenium (II)} [MTRP]n+, coordinated in its central cavity with Mn(III), Zn(II) or Ni(II) as a cationic layer, and polyoxotungstate [SiW12O40]4− as the anionic layer. Electrochemical measurements and UV–vis spectroscopy were used to monitor the modification process. Optimal results were obtained when three layers were deposited onto the ITO surface and were stable in aqueous solution. The order of the multilayer formation was explored by comparing a modified electrode where [Zn(II)TRP]4+ was the outermost layer with an electrode where [SiW12O40]4− was the outer layer. Results show that the best performing electrode is one with [SiW12O40]4− as the outer layer. Nitrite reduction on these electrode surfaces was studied in dark conditions and under light irradiation. Potential controlled electrolysis experiments were also performed, finding hydroxylamine, hydrazine and ammonia as the reduction products in dark conditions. Under light irradiation, only hydrazine and ammonia were found and, we observed an increase in the amount of obtained product. In this case, the electrolysis was carried out 150mV less and half of time than in dark conditions. These results show that the combination of light and potential give rise to an improvement in the electrocatalytic properties of the modified electrodes. Continuous photolysis and IR spectroelectrochemical experiments were carried out to determinate the nature of this phenomena, evidencing the formation of an intermediary species between nitrite and [Mn(III)TRP]5+.

Nucleotide/Tb3+ coordination polymer nanoparticles as luminescent sensor and scavenger for nitrite ion

Newly emerged metal organic coordination polymers have aroused the great interest in designing tailored functional materials. In this study, multiple functional components, luminescent Tb3+ ion, nucleobase and antenna molecule, were integrated in a single material and prepared into a responsive nanoparticle for nitrite. The terbium coordination polymer nanoparticles made of this kind of material have the dual functions of recognition and transduction and obey a preset sensing mechanism without a post-functionalization of common materials. As the result of the tailored, the terbium coordination polymer nanoparticles are highly sensitive and selective to nitrite by means of Dexter energy transfer between Tb3+ ion and nitrite, and can be used for the scavenger for nitrite in aqueous solution. The detection limit, dynamic range and removal capacity of U–Tb–OBBA CPNPs for nitrite are 0.3 µM, 0.3–470 µM and 4.44 mg per gram of particles, respectively. Metal organic coordination polymers show an attractive potential in constructing smart sensing materials.

Utilizing of Ag@AgCl@graphene oxide@Fe3O4 nanocomposite as a magnetic plasmonic nanophotocatalyst in light-initiated H2O2 generation and chemiluminescence detection of nitrite

A simple and sensitive chemiluminescence (CL) procedure was developed for the quantification of nitrite in aqueous solutions. The method is based on light-initiated generation of H2O2 by a magnetic Ag@AgCl@Graphene oxide nanocomposite and its subsequent redox reaction with nitrite ion in acidic medium. During the carbonate-catalyzed decomposition of produced peroxynitrite and energy transferring to uranine, a CL emission was observed at λ=534nm. Several factors affecting the CL intensity were investigated and optimized. Under optimum conditions, the CL intensity was directly proportional to the nitrite concentration in the range of 5‒200ngmL−1. The limit of detection and relative standard deviation (for n=5; at a nitrite concentration of 70ngmL‾1) were 1.15ngmL−1 and 2.57%, respectively. The method was successfully applied to determine nitrite in food stuffs with recoveries in the range of 95.0–103.0% for the spiked samples. The accuracy of the method was evaluated by comparing the results with those obtained by analyzing the samples using a standard method.

Solar Light Photocatalytic Degradation of Nitrite in Aqueous Solution Over CdS Embedded on Metal–Organic Frameworks

A CdS embedded metal-organic framework (MIL-100) composite was synthesized and used for photocatalytic degradation of nitrite ions. The obtained samples were characterized by a series of techniques such as X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM) and UV-Vis diffuse reflectance spectra (DRS). The results show that CdS nanoparticles were dispread and embedded on the MIL-100 crystals. The CdS/MIL-100 composites exhibited significant activities for photocatalytic degradation of nitrite ions through a disproportionation process in a neutral aqueous solution without any sacrificial reagents. When 20 wt% of CdS was embedded, the highest degradation yield of 92 % was achieved in 10-ppm NaNO2 aqueous solution under simulated solar light irradiation, which was fivefold of bare CdS. The enhancement in photocatalytic activities could be contributed to photosensitization and supporting of metal-organic framework scaffold.