Determination Of Nitrite Research Articles

Single flow-based system for the automatic multiparametric nutrients (NPK & Fe) assessment in soil leachates

A multiparametric sequential injection system for the determination of phosphate, nitrite, nitrate, potassium, and iron(III) in a single manifold was developed. The main goal of the proposed method was to develop an efficient tool to assess a number of essential chemical compounds in soils, providing the corresponding information on soil fertility and, additionally, information on possible groundwater contamination. The method was applied for the quantification of the aforementioned parameters in simulated leachates produced in laboratory-scale core columns. The relative standard deviations of ten replicate analyses of a standard were: 6% for phosphate; 2% for nitrite; 2% for nitrate; 5% for potassium; and 6% for iron(III). The limits of detection and quantification were: 2.15 and 7.18 μmol/L for phosphate determination; 0.22 and 0.73 μmol/L for nitrite determination; 3.42 and 8.00 μmol/L for nitrate determination; 39 μmol/L (limit of detection) for potassium determination; and 0.46 and 1.85 μmol/L for iron(III) determination. The sequential injection system was successfully applied for the quantification of multiple soil chemical components (PO43−, NO2−, NO3−, K+, and Fe3+) in soil leachates. The analysis of a sample, involving all the analytes, has a duration of 28 min.

Facile synthesis and modifying of Nitrogen-doped graphene quantum dots (N-doped GQDs) as fluorescent probes for detection of nitrite ions

Modifying of graphene quantum dots (GQDs) by adding heteroatoms to them improves their structural and optical properties and also makes them applicable in different areas. In this work, we synthesized nitrogen- doped GQDs (N-GQDs) by green method. They were used as fluorescence probes for the recognition and determination of nitrite. The reaction between the nitrogen groups of N-GQDs sensors and the analyte caused quenching fluorescence to increase linearly with increasing nitrite concentration due to an electron transfer mechanism. Under the ideal tested conditions, the response of N-GQDs to nitrite showed a concentration range of 0.3–1400 µM and R2 = 0.9956 with a LOD of 0.1 µM, with (S/N = 5).

Nitrite determination in food using electrochemical sensor based on self-assembled MWCNTs/AuNPs/poly-melamine nanocomposite

A nanocomposite of multi-walled carbon nanotubes/gold nanoparticles/poly-melamine (MWCNTs/AuNPs/PM) was designed using layer-by-layer self-assembled method on glassy carbon electrode (GCE) by electrochemical deposition to construct an electrochemical sensor for sensitive detection of nitrite. First, a layer of MWCNTs was modified on electrode, and then gold nanoparticles and melamine were in-situ polymerized onto MWCNTs through self-assembled technique to form GCE/MWCNTs/AuNPs/PM. MWCNTs have large specific surface area, which increased the number of gold nanoparticles deposited on MWCNTs. Meanwhile, the doping of gold nanoparticles also improved the polymerization of melamine. The synergistic interaction of nanocomposite further improved the catalytic effect on nitrite. Under optimized conditions, the detection range for nitrite was from 0.4 to 1475 μM and the detection limit was 0.041 μM. Through the detection of nitrite in food samples, the recovery rates were from 93.16% to 108.68%. Therefore, the method can be used as a practical platform for nitrite detection in food.

Разработка метода одновременного определения нитратов и нитритов в различных видах пищевых продуктов

Нитраты и нитриты – это соли неорганической природы, добавляемые в пищевые продукты для улучшения их вкусовых качеств и продления срока хранения. Однако, если их содержание превышает нормы, они могут стать причиной различных заболеваний, например, болезней сердечно-сосудистой системы, образования злокачественных опухолей и даже метгемоглобинемии. Соответственно существует необходимость контроля данных соединений. В данной статье рассмотрена возможность проведения одновременного определения нитрат- и нитрит-ионов в пищевых продуктах с целью упрощения и оптимизации работы аналитических лабораторий. Это связано с широким спектром узконаправленных методик, подходящих только конкретным группам продуктов. Автором был проведен обзор существующих методов, распространенных как в нашей стране, так и за рубежом. На основании обзора был подобран метод высокоэффективной жидкостной хроматографии с использованием неподвижной фазы на основе диоксида кремния с гидрофобной алкильной цепью с ионизированным концом, что обеспечило как гидрофобные обращенно-фазовые, так и слабые анионообменные свойства. Были исследованы разные составы подвижной фазы для сравнения эффективности и простоты разделения. В процессе работы подобраны условия для выделения и определения нитратов и нитритов в любых пищевых матрицах. Также автором была проведена оценка повторяемости методики для разных групп продуктов в условиях одной лаборатории. Результаты исследования показали, что разработанная методика определения нитрат- и нитрит-ионов имеет высокие значения точности и повторяемости, что позволяет использовать ее в качестве альтернативного и универсального метода определения содержания нитратов и нитритов в любых группах пищевых продуктах. Этот метод может быть широко применен в пищевой промышленности и научных исследованиях для контроля качества и безопасности продуктов питания. Nitrates and nitrites are inorganic salts added to food products to improve taste and extend shelf life. However, if their levels exceed the norms, they can cause various diseases, such as cardiovascular disease, malignant tumor formation, and even methemoglobinemia. Therefore, there is a need to control these compounds. This article discusses the possibility of simultaneous determination of nitrate and nitrite ions in food products to simplify and optimize the work of analytical laboratories. This is due to a wide range of narrowly targeted methods that are suitable only for specific groups of products. The author reviewed existing methods, which are common both in our country and abroad. Based on the review, the method of high-performance liquid chromatography with a stationary phase based on silica dioxide with a hydrophobic alkyl chain with an ionizable terminus, which provided both hydrophobic reverse-phase and weak anion-exchange properties was selected. Different compositions of the mobile phase were studied to compare the efficiency and simplicity of separation. During the work, conditions were selected for the isolation and determination of nitrates and nitrites in any food matrix. The author also assessed the repeatability of the methodology for different product groups under the conditions of one laboratory. The research results showed that the developed method for determining nitrate and nitrite ions has high accuracy and reproducibility values, which allows its use as an alternative and universal method for determining the content of nitrates and nitrites in any food product group. This method can be widely used in food industry and scientific research to control the quality and safety of food products.

Application of oxygen scavengers in gel electromembrane extraction: A green methodology for simultaneous determination of nitrate and nitrite in sausage samples.

The generation of oxygen from electrolysis in gel electromembrane extraction (G-EME) causes a negative error when applied to the analysis of easily oxidized species such as nitrite. Nitrite in G-EME is oxidized by oxygen to nitrate, leading to the negative error and the impossibility of simultaneous analysis. In this work, the application of oxygen scavengers to the acceptor phase of the G-EME system was attempted to minimize the oxidation effect. Several oxygen scavengers were selected and examined according to their compatibility with ion chromatography. The mixture of sulfite and bisulfite (14mg L-1) showed the highest efficiency in preventing the oxidation of nitrite to nitrate. Under the optimized conditions, a good linear range was obtained (10-200μg L-1; R2>0.998) with a detection limit of 8µg L-1 for both nitrite and nitrate. This method was applied to the simultaneous determination of nitrite and nitrate in sausage samples.

Nutrients and chlorophyll-a concentration in Socah Estuary receiving shrimp pond waste, Bangkalan Regency

This study investigates the nutrient content, water quality, and its relationship with chlorophyll-a in the Socah Estuary, Bangkalan Regency. The research was conducted in four stations. Determination of nitrate and nitrite in samples was performed by the colorimetric method. Meanwhile, phenate and Nessler reagent spectrophotometric methods were used to determine the ammonia and ammonium content in samples, respectively. The phosphate and chlorophyll-a were determined using ascorbic acid and spectrophotometry, respectively. The Spearman rank correlation was used to measure the degree of relationship between nutrients and chlorophyll- a content. Based on the results of Spearman rank correlation, the nitrate showed the strongest correlation (rho = 0.76) compared to other nutrients. Moreover, the increased chlorophyll-a level in the water will be closely related to the increased nitrate level. According to the value of Secchi depth, nutrients, and chlorophyll-a concentration, eutrophic is a trophic state in Socah Estuary. This condition is caused by the input of shrimp pond wastewater which triggers nutrient enrichment, decreasing the water quality and increasing the phytoplankton biomass in Socah Estuary.

Recovery of Agricultural Waste to Obtain Compost

The aim of this study is to make compost in a specialized container, using household and agricultural waste from own farm and the physicochemical characterization of obtained compost. The physicochemical characterization of the compost samples was carried out through the following determinations: determination of moisture, pH, determination of total soluble salts, determination of nitrate nitrogen, determination of nitrite, determination of ammonium nitrogen and determination of organic matter content. The compost samples analysed showed a high physicochemical quality. The use of compost offers environmentally friendly solutions with a long-term impact on the environment and quality of life.

A Dual-mode Ratiometric Fluorometric and Colorimetric Platform Based on Nitrogen-doped Carbon Dots and o-phenylenediamine for the Detection of Nitrite.

In this study, a dual-mode ratiometric fluorometric and colorimetric platform for the determination of nitrite in pickles was proposed by exquisitely employing the fact that non-fluorescent o-Phenylenediamine (OPD) was oxidized by nitrite under acidic conditions to form fluorescent 2,3-diaminophenazine (DAP) (Em = 575), which meanwhile quench the fluorescent nitrogen-doped carbon dots (N-CDs) at 455nm, the ratio of fluorescence intensity of DAP to N-CDs (F575/F455) changed with the increase of nitrite accompanied by visible color changes. Thus, nitrite can be quantitatively detected within a wide linear range (10-500 µM) with a low detection limit of 0.45 µM due to the high quantum yield of 39.7% of N-CDs. In addition, the colour of the N-CDs/OPD system changed from transparent to yellow when the nitrite was introduced, enabling colorimetric and on-site visual detection. The detection limit of the colorimetric method was 3.03 µM with a linear range of 10-500 µM. The proposed ratiometric fluorometric method has pleasant selectivity and good immunity to interference.

Parts per billion of nitrite in microcrystalline cellulose by ion chromatography mass spectrometry with isotope labeled internal standard

Regulatory authorities like the U.S. Food and Drug Administration (FDA) have set strict specification levels for N-nitrosamines in finished drug products. Nitrite is a potential precursor for the formation of probable carcinogenic N-nitrosamines when secondary or tertiary amines are also present in the active pharmaceutical ingredient (API) synthesis or drug formulation process. An accurate and sensitive determination of nitrite will be useful when a drug product manufacturer chooses to investigate the reaction kinetics between nitrite and amines or to select appropriate excipients for its drug formulation. Pharmaceutical excipient manufacturers may also need an accurate nitrite measurement to investigate the nitrite content in their excipients. This study details the development and validation of an ion chromatography mass spectrometry (IC-MS) method for trace nitrite determination in microcrystalline cellulose materials, one of the important pharmaceutical excipients used in many drug formulations. MS operated under selected ion monitoring mode was used to solve the commonly encountered interference issue with conductivity detection, and nitrite isotope internal standard was employed to address the ion suppression issue with MS detection. The installation of an after-column “jumper” to flush water with an auxiliary pump through the MS when it is not used for data collection avoided sensitivity loss due to trace salt accumulation in the ion source. Validation of the optimized method was satisfactory, with linearity of nitrite in the concentration range of 0.02–7.50 ppm (µg/g) having a regression coefficient of > 0.999, precision of RSD < 9.5% at 0.03 ppm and RSD < 3.4% at 0.4 ppm and recovery of 92.0–103.0%. The limit of detection and limit of quantitation were 0.005 and 0.016 ppm, respectively.

Ag nanoparticles-decorated CuBi2O4-rGO electrodes as an amperometric sensor for electrochemical determination of nitrite

There is an increasing demand for developing more sensitive sensors for determining nitrite, which has potential use in wastewater, food preservatives, and corrosion inhibitors. Here, we designed a CuBi2O4/rGO nanocomposite via simultaneous electrochemical deposition of GO and CuBi2O4. Then, the nanocomposite surface was electrochemically functionalized with Ag nanoparticles. Analytical and morphological characterizations showed that nanocomposites were synthesized with high purity and crystallinity. Finally, the electrocatalytic activity of the prepared Ag@CuBi2O4/rGO electrode was investigated as an electrochemical sensor application in nitrite detection. Ag@CuBi2O4/rGO had a higher faradaic current than CuBi2O4/rGO and PGE. The modified electrode exhibited high selectivity with low nitrite oxidation potential (+ 0.8 V) and detection limit (0.18 µM). The detection limit for nitrite is lower than that of most reported materials.

Density functional theory–guided electrochemical determination of nitrite in foods based on 2D metal-organic frameworks

This paper presents results for four types of morphology-controlled two-dimensional cobalt based tetrakis (4-carboxyphenyl) porphyrin metal-organic frameworks (2D Co-TCPP MOFs) with different catalytic properties for nitrite, and an electrochemical sensor was fabricated by the Co-TCPP MOF with superior catalytic properties. The sensor exhibited a high sensitivity of 311.3 μg/g, an extra low detection limit (LOD) of 0.03 μM, and a wide linear range of 0.1–375 μM, which was applied successfully for nitrite detection in water, milk and sausage. Moreover, density functional theory (DFT) calculations were used to establish the sensing method, the adsorption structures of nitrite on the surface of Co-TCPP MOF were built and the electrocatalytic mechanism was confirmed. The results explained why the sensor fabricated by a single Co-TCPP MOF exhibited equal or better performance than reported sensors fabricated by composite materials based on a combination of theory and experiment. This work reported a universal electrochemical sensing method for nitrite detection in food based on a single morphology-controlled 2D TCPP MOF, which provided a new and valuable strategy for establishing an efficient food safety determination method guided by theoretical calculations.

Flower-like 3D MoS2 microsphere/2D C3N4 nanosheet composite for highly sensitive electrochemical sensing of nitrite

Nitrite pollution poses a serious threat to human health and the environment. In this study, a reliable and selective electrochemical (EC) sensor was developed for the quantitative determination of nitrite by combining flower-like three-dimensional (3D) MoS2 microspheres with two-dimensional (2D) C3N4 nanosheets. Benefiting from the synergistic effects of MoS2 and C3N4, the 3D MoS2/2D C3N4 nanocomposite displayed numerous active sites, a 3D mesoporous structure, high conductivity and excellent catalytic activity. The 3D MoS2/2D C3N4-modified glassy carbon electrode (GCE) exhibited a superior electrocatalytic activity toward nitrite oxidation, with a wider linear detection range (0.1–1100 μM), a lower detection limit (LOD) (0.065 μM, S/N = 3), outstanding stability, remarkable reproducibility and strong selectivity. Furthermore, the nitrite EC sensor was successfully applied to detect actual food and environmental samples involving sausage, pickled vegetables, river water and tap water, thus demonstrating the potential of the prepared 3D MoS2/2D C3N4/GCE for food analysis and environmental monitoring.

A dual-mode nanoprobe based on silicon nanoparticles and Fe(II)-phenanthroline for the colorimetric and fluorescence determination of nitrite

A dual-mode nanoprobe based on silicon nanoparticles and Fe(II)-phenanthroline for the colorimetric and fluorescence determination of nitrite

Determination of nitrite in food specimens using electrochemical sensor based on polyneutral red modified reduced graphene oxide paste electrode

This work's purpose was a design a nanocomposite of polyneutral red and reduced graphene oxide paste electrode (pNR/rGO-PE) that may be employed as an accurate and sensitive electrochemical sensor to measurement of nitrite level in real food samples. The electro-polymerization process was employed for the synthesis of pNR/rGO-PE. Results from XRD and SEM analysis proved that NR was successfully electro-polymerized on rGO-PE. The incorporation of rGO nanosheets into conducting NR polymer with synergistic effects improved the electrochemical response of the modified electrode with great selectivity and sensitivity of 0.01511 µA/µM and a stable and broad linear range from 0 to 14,000 µM, according to electrochemical studies using CV and amperometry. The low detection limit of the nitrite sensor was 17 nM. The accuracy and validation of the pNR/rGO-PE as a nitrite sensor in prepared meat samples were studied. The attained RSD values (3.56–4.78%) and recovery (90.00–96.66%) values for amperometry analysis were satisfactory, confirming the applicability and validation of the pNR/rGO-PE results for the determination of nitrite level in food samples.

Cobalt-Nitrogen Co-Doped Carbon as Highly Efficient Oxidase Mimics for Colorimetric Assay of Nitrite.

Transition metal-N-doped carbon has been demonstrated to mimic natural enzyme activity; in this study, cobalt-nitrogen co-doped carbon (Co-N-C) nanomaterial was developed, and it could be an oxidase mimic. Firstly, Co-N-C with oxidase-like activity boosts the chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB) to produce the oxidized TMB (oxTMB). And the aromatic primary amino group of oxTMB reacts with nitrite (NO2-) to form diazo groups. Based on this background, we developed a cascade system of a Co-N-C-catalyzed oxidation reaction and a diazotization reaction for nitrite determination. The low detection limit (0.039 μM) indicates that Co-N-C is superior compared with the vast majority of previously reported nitrite assays. This study not only provides a novel nanozyme with sufficiently dispersed active sites, but it also further applies it to the determination of nitrite, which is expected to expand the application of nanozymes in colorimetric analysis.

Određivanje sadržaja nitrata i nitrita u mesnim proizvodima bez dodanih aditiva

A food additive is any substance not consumed as a food ingredient but added to food for a specific purpose, for example inhibiting microorganism growth and maintaining sensory quality. Potassium and sodium nitrates and nitrites are among the most commonly used food additives in the meat industry due to their antimicrobial effect, in particular to prevent the growth of pathogenic bacteria Clostridium botulinum and its spores. Additionally, they provide specific sensory attributes, primarily the inherent pink color of meat products. Studies showed that excessive intake of nitrates and nitrites may pose a risk to human health. The object of this research was determination of nitrite and nitrate content in meat products without added additives or with those additives from natural sources. Samples were mortadella, cooked ham and bologna sausage as thermally proccessed (cured) meat products and fermented sausage. The statistical analysis of the results for mortadella, cooked ham and bologna sausage as thermally proccessed meat products showed a p-value &amp;lt;0.05 between recipes with added nitrite salt and new recipes. The values of the median mass concentration of sodium nitrite in the commercial recipes were from 3.50-40.50 mg/kg, whereas this value was below the limit of detection in new recipes. Also, for fermented sausage, the p-value below 0.05 between commercial recipe with nitrite and nitrate salt and new recipes confirmed the hypothesis for replacement of mentioned salts with new concepts. The value of the median mass concentration of sodium nitrate in the recipe with added nitrate salt was 268.52 mg/ kg, whereas this value was below the limit of detection in other recipes.

Bifunctional manganese-doped silicon quantum dot-responsive smartphone-integrated paper sensor for visual multicolor/multifluorescence dual-mode detection of nitrite

Considering great threats of nitrite in food toward public health, it is significant to develop portable, dependable, and cost-effective methods to detect the target. In comparison with traditional colorimetric or fluorometric strategies relying on the intensity variation at a single wavelength, multimodal measurement with notable color changes is a more attractive paradigm because of its stronger resistance against external conditions, expanded application scenario, improved reliability, and naked-eye distinguishable readouts. However, it remains a challenge on how to attain this goal. Here we proposed a smartphone-integrated paper sensor based on manganese-doped silicon quantum dots (Mn-SiQDs) for the visual dual-mode multicolor/multifluorescence determination of nitrite. The Mn-SiQDs featured both photoluminescence and oxidase-mimetic catalytic activity, and could stimulate the colorless 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation to a blue species TMB+. When nitrite existed, the generated TMB+ selectively reacted with the analyte to produce yellow diazotized TMB+. Meanwhile, the photoluminescence of Mn-SiQDs could be suppressed by the diazotized TMB+ via inner filter effect. As a result, with a facile electrostatic assembly of Mn-SiQDs and [Ru(bpy)3]2+, the formed complex Mn-SiQDs/[Ru(bpy)3]2+ led to the variations of both color and photoluminescence upon different levels of nitrite. By combining the principle with paper strips and smartphone sensing, the fabricated sensor offered naked-eye visible multicolor/multifluorescence dual-mode response toward nitrite, exhibiting excellent specificity, performance stability, and practicability in food analysis. Our work provides an effective tool to achieve the multicolor/multifluorescence bimodal measurement of nitrite, and it will inspire future effort on designing versatile materials for advanced sensing applications.

A new ultrasound-assisted liquid-liquid microextraction method utilizing a switchable hydrophilicity solvent for spectrophotometric determination of nitrite in food samples

A new ultrasound-assisted liquid-liquid microextraction method utilizing a switchable hydrophilicity solvent for spectrophotometric determination of nitrite in food samples

Synthesis and synergistic effect of positively charged jute carbon supported AuNPs coated polymer nanocomposite for selective determination of nitrite

A nanocomposite with highly dispersed AuNPs coated poly[2-(methacryloyloxy) ethyl] trimethylammonium chloride (PMTC) supported upon jute carbon (AuNPs-PMTC-JC) was prepared in aqueous medium for the selective determination of nitrite (NO2−) ions. Quaternary ammonium groups of PMTC in the nanocomposite results in a positive zeta potential, elevating the electrocatalytic properties of the modified electrode for negatively charged NO2− ions oxidation. The AuNPs-PMTC-JC composite was characterized using UV–vis, FESEM, TEM, SAED, XRD, EDS, CV and EIS. The LOD (S/N = 3) value for NO2− determination is 0.16 µM in the linear range of 0.4–706.5 µM based on the i-t current response, while it is 1.28 µM based on CV responses in the wide range of 10–1000 µM. The modified electrode is highly selective for NO2− ions and shows highly stable, and reproducible results. CV was used to analyze tap water spiked with NO2− and a recovery close to 100 % was observed.

Fabrication of a colorimetric sensor using acetic acid-capped drug-mediated copper oxide nanoparticles for nitrite biosensing in processed food

Nitrite (NO2−) and nitrate (NO3−) are frequently used in cured meat products as preservatives, as they give a better taste and work well in color fixation. As a key possible carcinogen, excessive dietary consumption of NO2− in cured meat products would be bad for health. Herein, copper oxide nanoparticles (CuO NPs) were synthesized using the drug Augmentin as a reducing and capping agent. The desired synthesis of CuO NPs was confirmed by various characterization techniques, including UV–visible spectroscopy, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, thermal gravimetric analysis, X-ray diffraction, and scanning electron microscopy. The new approach of drug-mediated acetic acid-capped CuO NPs was developed for simple colorimetric detection of nitrite ions in a mimic solution of processed food. The color of the detection system changes from brown to yellow with the increase in the concentration of NO2− and has been observed with the naked eye. The selectivity of the NO2− detection system by the UV–visible spectrum and the naked eye is compared to other ions, such as Br−, I−, Cl−1, PO4−3, CO32−, and SO42−. The platform was successfully employed for the determination of nitrite in real samples. Moreover, this probe can be used for the sensitive detection of NO2− with a linear range of 1 × 10−8 to 2.40 × 10−6 M, a detection limit of 2.69 × 10−7 M, a limit of quantification 8.9 × 10−7 M, and a regression coefficient (R2) of 0.997. Our results suggest that this sensor can be used for on-site analysis and quantification as well as in the fields of disease diagnosis, environmental monitoring, and food safety.