Selective Determination Of Nitrite Research Articles

Selective determination of nitrite in water and food samples using zirconium oxide (ZrO2)@MWCNTs modified screen printed electrode.

Nitrite ions are being used in different forms as food preservatives acting as flavor enhancers or coloring agents for food products. However, continuous ingestion of nitrite may have severe health implications due to its mutagenic and carcinogenic effects. Thus, this study constructed an electrochemical assay using disposable nano-sensor chip ZrO2@MWCNTs screen printed electrodes (SPE) for the rapid, selective, and sensitive determination of nitrite in food and water samples. As a sensing platform, the use of nanomaterials, including metal oxide nanostructures and carbon nanotubes, exhibited a superior electrocatalytic activity and conductivity. Morphological, structural, and electrochemical analyses were performed using electron microscopy (SEM and TEM), Fourier-transform infrared (FTIR) spectroscopy, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry (CA). Accordingly, a wide dynamic linear range (5.0 μM to 100 μM) was obtained with a limit of detection of 0.94 μM by the chronoamperometric technique. In addition, the sensor's selectivity was tested when several non-target species were exposed to the sensor chips while no obvious electrochemical signals were generated when the nitrite ions were not present. Eventually, real food and water sample analysis was conducted, and a high recovery was achieved.

Inexpensive spectrophotometric determination of nitrite with a laboratory-constructed flow cell

Nitrite is a carcinogenic substance and its measurement in water samples is important to protect mankind. Here we have introduced a simple and inexpensive fluidic system for the online determination of nitrite in water samples. For this purpose, a highly sensitive, optical flow cell detector was fabricated and used in a fluidic system to prepare a compact unit for nitrite monitoring. Safranin solution in acidic media was used in the system for the sensitive and selective determination of nitrite. In acidic media, nitrite reacted with safranin to form a diazonium salt which caused the dye in the solution to change from reddish-orange to blue. The safranin solution absorbance, which is related to nitrite concentration, was monitored by the fabricated photometer with the flow detector at 525 nm. Water samples were processed to evaluate the effectiveness of both the introduced system and the analytical procedure. Good analytical performance was obtained, including a linear response from 0.3 up to 3 mg/l nitrite (r = 0.9918) with a detection limit of 0.1 mg/l and a relative standard deviation of 4.24% (n = 10), using the proposed setup.

Terbium metal organic framework: Microwave synthesis and selective sensing of nitrite

The rapid and facile microwave method has been employed to synthesize [Tb2(TTHA)(H2O)4]·9H2O (I; H6TTHA = 1,3,5-triazine-2,4,6-triaminehexaacetic acid) microcrystals. Based on the photoluminescent emission of I, which can be selectively turned off upon the coordination of nitrite, the selective determination of nitrite in water was developed without the use of Griess reagents. With the use of smartphone camera as a detector, the quantitative analysis of nitrite was conducted within the CIELAB colorimetric space, revealing the relative standard deviation of less than 5% for the working range of 3–12 μg. Sensitivity, detection limit and quantification limit of the measurements were evaluated, providing the values of 0.732 (Lcontrol/Lsample)·μg−1, 1 μg and 3 μg, respectively.

Template-cum-catalysis free synthesis of α-MnO2 nanorods-hierarchical MoS2 microspheres composite for ultra-sensitive and selective determination of nitrite

In this work, a novel composite constituted by α-MnO2 nanorods and hierarchical MoS2 microspheres is synthesized by a simple, template-cum-catalysis free two-step hydrothermal method for ultra-sensitive and selective detection of nitrite. The nitrite sensor (with optimal MnO2-MoS2 weight ratio) showed a limit of detection of 16 μM, the short response time (<5 s), outstanding selectivity, reproducibility, and sensitivity of 515.84 μA mM−1 cm−2 (R2 = 0.996) in the range of 100–800 μM in an optimized electrolytic pH of 4. The excellent sensing ability of the sensor can be attributed to the heterogeneous interface between two material constituents that results in unimpeded electrical transport due to the presence of intertwined nanosheets in MoS2 and 1D α-MnO2 nanorods, high number of active sites emanating from huge numbers of edges and defects in MoS2, high proportion of metallic (1T) phase than semiconducting (2H) phase in MoS2 and the combined effect of 1D α-MnO2 nanorods and MoS2 nanosheets. The fabricated sensor was also effectively assessed for the detection of nitrite in potable water. This novel, binder-free, MnO2-MoS2 composite based electrode material paves a new way for the development of simple, non-enzymatic and inexpensive electrochemical sensors for analytical applications.

Potentiodynamic formation of diaminobenzene films on an electrochemically reduced graphene oxide surface: Determination of nitrite in water samples

An electrode comprised of a polydiaminobenzene (p-DAB) film formed on electrochemically reduced graphene oxide (ERGO) on a glassy carbon (GC) (p-DAB@ERGO/GC) was fabricated using a potentiodynamic method for the sensitive and selective determination of nitrite in the presence of a common interference. The p-DAB@ERGO/GC film-modified electrode surfaces were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The film fabrication was initiated via the NH2 groups of DAB, which was confirmed by XPS from the peaks corresponding to NH (396.7eV), NH (399.4eV), NN (400.2eV), and N+H (402.2eV). The Raman spectra revealed the characteristic D and G bands at 1348 and 1595cm−1, respectively, which confirmed the fabrication of GO on the GC electrode, and the ratio of the D and G bands was increased after the electrochemical reduction of GO. The surface coverage of the modified electrode was 8.16×10−11molcm−2. The p-DAB@ERGO/GC film-modified electrode was used successfully for the determination of nitrite ions. The p-DAB@ERGO/GC film-modified electrode exhibited superior activity for the determination of nitrite compared to the bare GC and p-DAB@GC electrodes. The amperometric current increased linearly with increasing nitrite concentration from 7.0×10−6 to 2.0×10−2M. The detection limit was 30nM (S/N=3). In addition, the modified electrode was used successfully to determine the nitrite ion concentration in the presence of a 100-fold excess of common interferents. The practical application of the modified electrode was demonstrated by determining the nitrite ion concentration in water samples.

Polyamidoamine dendrimer-armed fluorescent magnetic nanoparticles for sensitive and selective determination of nitrite in beverages

Herein, we report a novel solid-phase spectrofluorimetric method for the determination of nitrite. The fluorophore 1-naphthylamine-4-sulfonic acid was covalently bonded to the surface of magnetic silica nanoparticles using polyamidoamine dendron structures as spacers. The introduction of dendritic arms significantly improved the fluorescence intensity. Compared with the conventional solid-phase spectrofluorimetry based on physical adsorption of the derived fluorescent reagents to the sorbents, our method exhibited better selectivity and could directly analyze nitrite in real color samples without pretreatment. The concentrations of nitrite in beer, peach juice and grape juice were determined to be 0.146, 0.165 and 0.110mg/L, respectively, which is in good agreement with capillary electrophoresis results. Moreover, our novel method circumvented the disadvantage of the Langmuir-type isotherm of conventional solid-phase spectrofluorimetry and offered a detection limit of 10ng/L for a 500-mL fortified sample with a recovery of 90.5%. These promising results suggest that our strategy can be applied for the facile, sensitive and selective detection of nitrite in complicated matrices.

Simultaneous and Selective Determination of Nitrite, Nitrate and Phosphate Ions in Seawater by Ion Chromatography

Simultaneous and Selective Determination of Nitrite, Nitrate and Phosphate Ions in Seawater by Ion Chromatography

Simultaneous and Selective Determination of Nitrite, Nitrate, and Ammonium Ions in Seawater Samples by Ion Chromatography

Simultaneous and Selective Determination of Nitrite, Nitrate, and Ammonium Ions in Seawater Samples by Ion Chromatography

Highly sensitive and selective amperometric determination of nitrite using electropolymerized film of functionalized thiadiazole modified glassy carbon electrode

This paper reports a highly sensitive and selective determination of nitrite at physiological pH using electropolymerized film of 5-amino-1,3,4-thiadiazole-2-thiol (p-ATT) on glassy carbon electrode (GCE) by amperometry. Bare GCE oxidizes nitrite at 0.96 V in the first cycle and in the subsequent cycles the oxidation peak was shifted to 1.03 V with decreased peak current. However, p-ATT modified electrode oxidizes nitrite at 0.84 V with an enhanced peak current and this oxidation peak was very much stable in the subsequent cycles. Using amperometric method, we achieved the lowest detection of 50 nM nitrite for the first time. Further, the amperometric current increases linearly while increasing the nitrite concentration from 5.0 × 10 −8 to 1.6 × 10 −5 M and a detection limit was found to be 340 pM ( S/ N = 3). The modified electrode was used to determine nitrite in the presence of 1000-fold excess interferents such as Na +, F −, Ca 2+, Cl −, Mg 2+, SO 4 2 - , NH 4 + , K +, CO 3 2 - , NO 3 - , glucose, urea and oxalate. The practical application of the present method was successfully applied to the determination of nitrite in water samples.

A simplified screening procedure for determination of total N–NO groups (TNG) and nitrite (NO2−) in commercial low-molecular-weight heparins (LMWH) by selective chemical denitrosation followed by high-sensitivity chemiluminescence detection (NO-analyzer, NOA)

Aim of this work was to set up a method for the sensitive and selective determination of nitrite (NO2−) and total N-nitroso groups (TNG) in dalteparin and nadroparin, commercial low- molecular-weight heparins (LMWH), prepared by deaminative depolymerization of heparin with nitrous acid. The European Pharmacopoeia VI ed. indicates respectively 5ppm as the maximum content for contaminant NO2− in the former and 0.25ppm for TNG in the latter and no clear indication is given for N–NO groups in dalteparin, i.e. TNG must be absent because of the specific manufacturing process.The proposed technique is based on the development of a pre-analytical device, coupled to a chemiluminometer, constituted by three sequentially connected and commercially available purge vessels, where selective reagents are employed for the conversion of NO2− and N–NO to nitric oxide (NO). In detail, NO2− was determined in the first chamber and non-volatile and volatile TNG in the second and third. This method was validated for selectivity, sensitivity, linearity, accuracy and precision. The method was shown to be selective, with a quantitative linear range of 1–1000ppb). The bias, intra- and inter-day percent relative error was lower than 1%. The contamination of NO2− and TNG in nadreparin was below the limits; for dalteparin NO2− fell within the limit, but there was a huge amount of TNG (15.80±0.05ppm–6.69±0.02ppm). Preliminary investigation on the solvent-extractable material from dalteparin showed the majority of chemiluminescence retained in the aqueous residue to indicate that this N–NO groups may belong to solvent unextractable material or be tightly bound to the dalteparin backbone.

Chemiluminescence study of carbonate and peroxynitrous acid and its application to the direct determination of nitrite based on solid surface enhancement

Peroxynitrous acid (ONOOH) was produced by the on-line mixing of acidified hydrogen peroxide with nitrite in a flow system. A strong chemiluminescent (CL) emission was observed when ONOOH reacted with carbonate without any special CL reagents. When cotton was present in the CL cell, the CL emission was enhanced significantly. The method was developed to determine nitrite, which showed a key improvement that any CL reagents and sensitizers were not used, resulting in better selectivity. The applicability of the present CL system was demonstrated for the sensitive and selective determination of nitrite in natural water samples without any special pretreatment. Good agreements were obtained for the determination of nitrite in tap and well waters between the present approach and a standard spectrophotometric method. The average precision was 4.6% ( n=7) and detection limit ( S/ N=3) was 1.0×10 −7 M. Based on the CL spectrum, UV spectra, and dissolved oxygen measurement, a possible CL mechanism was proposed. ONOOH was an unstable compound in acidic solution and could be quenched into peroxynitrite (ONOO −) in basic solution. ONOO − reacted with CO 2 to produce ONOOCO 2 −, which can rapidly decompose into NO 2 and CO 3 − radicals. In the presence of H +, CO 3 − radicals can protonate to bicarbonate radical (HCO 3 ). The recombination of HCO 3 radicals and decomposition can lead to light emission.