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There are many works associating the presence of nitrate in water and the occurrence of cancer in humans. The most common method for quantifying nitrate in water is based on the use of toxic cadmium as a reductant. In this work, a new approach was developed for the quantification of nitrate in bottled water with indirect spectrophotometry using Zn0 as a reductant. Nitrate is reduced to nitrite using Zn0 in a buffered medium (acetate/acetic acid) and quantified with visible spectrophotometry using the Griess reaction between sulfanilamide and N-(1-naphthyl)-ethylenediamine. The influence of pH, buffer solution (constitution and concentration), Zn0 (mass and granulometry), and agitation time on the efficiency of nitrite generation was evaluated. The optimal conditions were an acetate-acetic acid buffer solution with a concentration and pH of 0.75 mol L-1 and 6.00, respectively, and a Zn0 particle size of 20 MESH and Zn0 mass of 300 mg. The limits of detection and quantification (LoD and LoQ) were 0.024 and 0.08 mg L-1, respectively. The method's accuracy and precision were evaluated using the analysis of commercial bottled water. In conclusion, the use of Zn0 instead of cadmium provided a green method with excellent LoD/LoQ. Further, the method proved to be simple and easy to apply during outdoor analysis.

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Dysregulation of nitric oxide (NO) and it's two relatively stable metabolites, nitrite, and nitrate, in SARS-CoV-2, are reported in infected populations, especially for nitrates levels > 68.4 µmol/L. In this paper, we measure the abnormal presence of nitrite in the saliva by developing a cheap µPAD for colorimetric detection through the modified Griess reaction. This includes a diazotization reaction between nitrite and Griess reagent, including Sulfanilamide and N-Naphthyl-ethylenediamine in an acidic medium, causing a pink Azo compound. The modifications are suggested by a numerical method model that couples the mass flux with the porosity medium equations (convection, diffusion and, dispersion) that improves the mixing process. The mixing index was quantified from the concentration deviation method via simulation of a homogeneous two-phase flow in a porous environment. Five µPAD designs were fabricated to verify the simulation results of mixing enhancement on the Griess reactants in saliva samples. The investigated geometries include straight, helical, zig-zag, square wave, and inclined jagged shapes fabricated by direct laser writing, suitable for low cost, mass fabrication. Inclined jagged micromixer exhibited the best performance with up to 40% improvement compared with the simple straight geometry. Deliberate geometrical modifications, exemplified here in a jagged micromixer on paper, cut the limit of detection (LOD) by at least half without impacting the linear detection range.

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To facilitate on-site nitrite determination for processed meat products, Griess-doped polyvinyl alcohol film was synthesized in the bottom of a plastic tube for in-tube determination. The tube's aperture was used to control the sample dimensions. Each sample, cut into eight sectors, was subjected to nitrite extraction by water. Use of tap water or commercial drinking water vs. ultrapure water was associated with < 2% differences in nitrite levels. The use of film and digital image colorimetry showed a low limit of detection (12.6 ± 0.5 µg L-1), good precision (1.0%RSD, n = 5 days), and good accuracy (93.2 ± 3.5 to 108.5 ± 1.8%recovery). Using these methods, sodium nitrite concentrations in 700 processed meat products for sale in Phuket, Thailand, were found to range from 6.8 ± 0.2 to 113.6 ± 1.3 mg kg-1. These results showed no significant differences with the HPLC standard method (p > 0.05, n = 45).

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In this work, the design of a microfluidic paper-based analytical device (µPAD) for the quantification of nitrate in urine samples was described. Nitrate monitoring is highly relevant due to its association to some diseases and health conditions. The nitrate determination was achieved by combining the selectivity of the nitrate reductase enzymatic reaction with the colorimetric detection of nitrite by the well-known Griess reagent. For the optimization of the nitrate determination µPAD, several variables associated with the design and construction of the device were studied. Furthermore, the interference of the urine matrix was evaluated, and stability studies were performed, under different conditions. The developed µPAD enabled us to obtain a limit of detection of 0.04 mM, a limit of quantification of 0.14 mM and a dynamic concentration range of 0.14-1.0 mM. The designed µPAD proved to be stable for 24 h when stored at room temperature in air or vacuum atmosphere, and 60 days when stored in vacuum at -20 °C. The accuracy of the nitrate µPAD measurements was confirmed by analyzing four certified samples (prepared in synthetic urine) and performing recovery studies using urine samples.

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When nitrite is ingested and absorbed by the body, it can be converted into highly toxic nitrosamines (carcinogens, teratogens, and mutagens), posing health risks to the general population. Therefore, it calls for establishing a method for determination of nitrite. In this paper, the glass-SiO2-Ag surface-enhanced Raman scattering (SERS) substrate with a large number of "hot spots" were prepared by two kinds of silane coupling agents. The SERS substrate had high sensitivity and repeatability. Silicon dioxide supported the silver nanoparticles (Ag NPs), which increased surface roughness of the substrate, generated a great quantity of hot spots and enhanced the SERS signal. In the SERS spectrum, the intensity ratio of the two characteristic peaks (1287 cm-1 and 1076 cm-1) had a good linear correlation with the logarithm of the concentration of nitrite, R2 = 0.9652. The recoveries of 50 µM and 100 µM nitrite in three kinds of foods, three kinds of cosmetics and tap water were 90.9-105.3%.

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Nitric oxide (NO) is a reactive gas that participates in many physiological as well as pathogenic processes in higher eukaryotic organisms. Inflammatory responses elicit higher levels of this molecule. Nevertheless, there are many technical challenges to accurately measure the amount of NO produced. Previously, a method using whole-cell extracts from Escherichia coli was able to generate the conversion of nitrate into nitrite to measure the amount of nitrate or indirectly the NO present in a sample using the Griess reaction. Here we present an improvement to this method, by using E. coli whole-cell extracts lacking one of the two nitrite reductases, rendered a more precise measurement when coupled with the Griess reaction than our previous report. Alternatively, osmotic stress showed to downregulate the expression of both nitrate reductases, which can be an alternative for indirect nitrate and NO reduction. The results presented here show an easy method for nitrate and NO reduction to nitrite and avoid the reconversion to nitrate, also as an alternative for other analytical methods that are based on cadmium, purified nitrate reductase enzyme, or salicylic methods to reduce NO. This method can be widely used for measuring NO production in living organisms, soil, and other relevant microbiological samples.

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In this paper, we report a simple and inexpensive paper-based microfluidic device for detecting nitrate in water. This device incorporates two recent developments in paper-based technology suitable for nitrate detection and has an optimized microfluidic design. The first technical advancement employed is an innovative fibrous composite material made up of cotton fibers and zinc microparticles that can be incorporated in paper-based devices and results in better nitrate reduction. The second is a detection zone with an immobilized reagent that allows the passage of a larger sample volume. Different acids were tested-citric and phosphoric acids gave better results than hydrochloric acid since this acid evaporates completely without leaving any residue behind on paper. Different microfluidic designs that utilize various fluid control technologies were investigated and a design with a folding detection zone was chosen and optimized to improve the uniformity of the signal produced. The optimized design allowed the device to achieve a limit of detection and quantification of 0.53 ppm and 1.18 ppm, respectively, for nitrate in water. This accounted for more than a 40% improvement on what has been previously realized for the detection of nitrate in water using paper-based technology.

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Reported herein is the immobilization of N-(1-naphthyl)ethylenediamine (NED) on cellulose via an epichlorohydrin (ECH)-based covalent attachment and the implementation of the functionalized cellulose into an ultrasensitive, paper-based device for nitrite detection. The reported functionalization procedure resulted in a 12.9-fold higher functionalization density than the density that results from the previously reported procedures, and the subsequent device allows for nitrite detection limits in synthetic freshwater and real seawater of 0.26 and 0.22 µM, respectively. The sensor is efficient in a wide range of temperature, humidity, turbidity, and salinity conditions and has been successfully applied for nitrite detection in real water samples.

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This study employed the use of a microfluidic paper-based analytical device (µPAD) to determine the concentration of nitrite in pork and enhanced the limit of detection by analyzing the coffee-ring effect. The µPAD was fabricated by designing and embedding wax channels onto the cellulose-based filter paper through printing and subjecting the paper to heat treatment to allow wax penetration. Nitrite concentration was determined by monitoring the colorimetric reaction that occurred between nitrite and the added Griess reagent. The limit of detection of this device for nitrite in pork was determined to be 19.2 mg kg-1 by analyzing the inner-chamber reaction, while it could be as low as 1.1 mg kg-1 if the coffee-ring region was analyzed. The overall analysis could be completed within 15 min. This µPAD-based method has potential applications to routinely screen the nitrite concentration of meat products and ensure food safety and consumer health.

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Primaquine (PMQ), a well-known anti-malarial drug, is of increasing importance as people moving toward global malaria eradication. PMQ has serious side effects that it often causes acute hemolytic toxicity in people with glucose-6-phosphate dehydrogenase (G6PD) deficiency. The development of simple and reliable approaches for quantitative dose monitoring is thus becoming important during malarial treatment with PMQ. Herein, an unexpected Griess reaction on PMQ was systematically studied. The reaction happened between substituted aniline and a primaquine molecule in the presence of nitrite. Both experimental measurements and theoretic calculation showed that UV-vis absorption of the azo products varied because of different electron contributing effects of substituents. Based on the optimized conditions, a novel colorimetric method has been developed for PMQ determination with excellent sensitivity and selectivity. The detection limits for PMQ in water and synthetic urine samples were down to nanomolar range. More importantly, this method has been successfully used to quantify PMQ from human serum samples within clinically relevant concentration ranges.

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Nitrite and Nitrate have been used extensively as additives in various meat products to enhance flavor, color, and to preserve the meat from the bacterial growth. High concentrations of nitrite can threat human health since several studies in the literature claim that nitrite is associated with cancer incidences, leukemia, and brain tumors. Therefore, it is vital to measure the nitrite concentrations in processed meat products. In this study, an in-lab miniaturized photometric detection system is fabricated to inspect the nitrite concentration in processed meat products in Jordan. The analytical performance of nitrite detection is evaluated based on three key statistical parameters; linearity, limit of detection, and limit of quantitation. Respectively, for the fabricated system, the three values are found to be equal to 0.995, 1.24 × 10-2 ppm, and 4.12 × 10-2 ppm. Adherence to Beer's law is found over the investigated range from 2.63 ppm to 96.0 ppm. The developed system is utilized for photometric detection of nitrite in processed meat products available in the Jordanian market like pastrami, salami, and corned beef. In all of the analyzed samples, the nitrite content is found to be lower than 150 ppm, which represents the maximum allowable nitrite limit.

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This study demonstrates a novel strategy for colorimetric/fluorescent/surface enhanced Raman scattering (SERS) triple-mode sensing of nitrite based on Griess reaction modulated gold nanorods (GNRs)-Azo-gold nanoparticles (GNPs) (GNRs-Azo-GNPs) assembly. The p-aminothiophenol (PATP)-capped GNRs (GNRs@PATP) and 1,8-diaminonaphthalene (DAP)-modified GNPs (GNPs@DAP) are first synthesized through Au-S and Au-N bonds, respectively. Upon being excited at 365nm, the dispersion of GNRs-GNPs (GNRs@PATP and GNPs@DAP) emits cyan fluorescence. Next, the addition of nitrite into the GNRs-GNPs induces the formation of GNRs-Azo-GNPs assembly, resulting in the enhancement of color and decrease of fluorescence. Therefore, the GNRs-Azo-GNPs assembly can not only be used as a naked-eye indicator of nitrite changed from orange-yellow to purple, but also as a highly selective ''fluorescence quenching'' probe due to the fluorescence resonance energy transfer (FRET) between azo-moiety and DAP. The limit of detection (LOD) for nitrite is 0.05µM by colorimetry and 0.01µM by fluorescence. Meanwhile, the GNRs-Azo-GNPs assembly possesses controllable core-satellites nanostructures and enables on-field SERS detection of nitrite with the LOD of 0.8nM. More importantly, the GNRs-GNPs sensing system can not only be used as a paper-based test strip for on-site fast screening of nitrite with a high sensitivity and selectivity, but also as a SERS substrate for reliable quantitative analysis of nitrite. This study offers a new method for on-site visual detection of nitrite in human urine and meat products, as well as provides a strategy for designing multi-mode sensing platform for various applications.

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The German organic chemist Johann Peter Griess (1829-88), who first developed the diazotization of aryl amines (the key reaction in the synthesis of the azo dyes), and a major figure in the formation of the modern dye industry, worked for more than a quarter of a century at the brewery of Samuel Allsopp and Sons in Burton upon Trent, which, owing to the presence of several notable figures and an increase in the scientific approach to brewing, became a significant centre of scientific enquiry in the 1870s and 1880s. Unlike the other Burton brewing chemists, Griess paralleled his work at the brewery with significant contributions to the chemistry of synthetic dyes, managing to keep the two activities separate-to the extent that some of his inventions in dye chemistry were filed as patents on behalf of the German dye company BASF, without the involvement of Allsopp's. This seemingly unlikely situation can be explained partly by the very different attitudes to patent protection in Britain and in Germany combined with an apparent indifference to the significant business opportunity that the presence of a leading dye chemist presented to Allsopp's. Although his work for the brewery remained largely proprietary, Griess's discoveries in dye chemistry were exploited by the German dye industry, which quickly outpaced its British counterpart. One less well-known connection between brewing and synthetic dyes, and one that may further explain Allsopp's attitude, is the use of synthetic dyes in identifying microorganisms-the perennial preoccupation of brewers seeking to maintain yield and quality. Developments of Griess's original work continue to be applied to many areas of science and technology.

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The article considers results of study of total concentration of nitrites and nitrates (NOx) in blood plasma of healthy individuals residing in St. Petersburg. The samples from 58 healthy individuals were analyzed and out of them - 31 aged 18-25 years and 27 aged 48-63 years. The concentration of NOx in blood plasma was determined using Griess reagent after reduction of nitrates under effect of NADH-dependent recombinant nitrate reductase from Arabidopsis thaliana. The surplus of NADH preventing Griess reaction was removed at the expense of of enzyme reaction in presence of lactate dehydrogenase and sodium pyruvate. The analysis and its calibration was carried out using additions of solution of sodium nitrate to samples of blood plasma without deproteinization. The data was obtained concerning variation of content of NOx in healthy individuals of various age. In particular, it is demonstrated that the level of total content of nitrogen oxide in the group of elder age was reliably higher (p=0.0001) as compared with donors aged 18-25 years.

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Determination of nitrate in aqueous samples is an important analytical objective for environmental monitoring and assessment. Here we report the first automatic flow injection analysis (FIA) of nitrate (plus nitrite) using VCl3 as reductant instead of the well-known but toxic cadmium column for reducing nitrate to nitrite. The reduced nitrate plus the nitrite originally present in the sample react with the Griess reagent (sulfanilamide and N-1-naphthylethylenediamine dihydrochloride) under acidic condition. The resulting pink azo dye can be detected at 540 nm. The Griess reagent and VCl3 are used as a single mixed reagent solution to simplify the system. The various parameters of the FIA procedure including reagent composition, temperature, volume of the injection loop, and flow rate were carefully investigated and optimized via univariate experimental design. Under the optimized conditions, the linear range and detection limit of this method are 0-100 µM (R(2)=0.9995) and 0.1 µM, respectively. The targeted analytical range can be easily extended to higher concentrations by selecting alternative detection wavelengths or increasing flow rate. The FIA system provides a sample throughput of 20 h(-1), which is much higher than that of previously reported manual methods based on the same chemistry. National reference solutions and different kinds of aqueous samples were analyzed with our method as well as the cadmium column reduction method. The results from our method agree well with both the certified value and the results from the cadmium column reduction method (no significant difference with P=0.95). The spiked recovery varies from 89% to 108% for samples with different matrices, showing insignificant matrix interference in this method.

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A continuous-flow microfluidic chip-based standard addition/absorption detection system has been developed for accurate determination of nitrite in water of varying salinity. The absorption detection of nitrite is made via color development using the Griess reaction. We have found the yield of the reaction is significantly affected by salinity (e.g., -12% error for 30‰ NaCl, 50.0 µg L(-1)N-NO2(-) solution). The microchip has been designed to perform standard addition, color development, and absorbance detection in sequence. To effectively block stray light, the microchip made from black poly(dimethylsiloxane) is placed on the top of a compact housing that accommodates a light-emitting diode, a photomultiplier tube, and an interference filter, where the light source and the detector are optically isolated. An 80-mm liquid-core waveguide mounted on the chip externally has been employed as the absorption detection flow cell. These designs for optics secure a wide linear response range (up to 500 µg L(-1)N-NO2(-)) and a low detection limit (0.12 µg L(-1)N-NO2(-) = 8.6 nM N-NO2(-), S/N = 3). From determination of nitrite in standard samples and real samples collected from an estuary, it has been demonstrated that our microfluidic system is highly accurate (<1% RSD, n = 3) and precise (<1% RSD, n = 3).

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A high-performance ionic-sensing platform has been developed by an interdisciplinary approach, combining the classical colorimetric Griess reaction and new concepts of nanotechnology, such as plasmonic coupling of nanoparticles and surface-enhanced Raman scattering (SERS) spectroscopy. This approach exploits the advantages of combined SERS/surface-enhanced resonant Raman Scattering (SERRS) by inducing the formation of homogeneous hot spots and a colored complex in resonance with the laser line, to yield detection limits for nitrite down to the subpicomolar level. The performance of this new method was compared with the classical Griess reaction and ionic chromatography showing detection limits about 6 and 3 orders of magnitude lower, respectively.

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Nitric oxide (NO) is involved in bone remodelling and has been shown to play a role in regulating the rate of orthodontic tooth movement (OTM) in rat models. In humans, however, the role of NO in OTM remains less clear. In this study, NO concentration in gingival crevicular fluid (GCF) was measured in patients undergoing orthodontic treatment. Thirteen male participants (ages 11-18 years) planned for non-extraction fixed orthodontic therapy were recruited. Samples of GCF were collected from each maxillary central incisor and first and second molar immediately before (T0), 1h after (T1), and 3-4 days after (T2) application of light orthodontic forces. The maxillary second molars were not included in the appliance and served as controls. Measureable NO levels were consistently obtained from all sampled sites. Total NO levels showed significantly higher NO levels (p<0.05) at T1 at the buccal surfaces of the central incisors when compared to the first and second molars. The results indicate a possible role for NO in OTM at the pressure sites of incisors at early time points. Further studies are required to determine whether NO levels in the periodontal ligament tissues of human teeth during OTM are affected by a force gradient and the magnitude of the applied force.

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Despite their potential carcinogenicity and probable formation during water disinfection processes, little is known about the occurrence of other nitro(so) compounds than a few specific N-nitroso compounds such as N-nitrosodimethylamine (NDMA). An analytical method was developed to monitor various nitro(so) compounds including N-nitrosamines based on the Griess colorimetric determination of nitrite generated by UV-254 nm photolysis of nitro(so) compounds after separation by HPLC (HPLC-Post Column UV photolysis/Griess reaction (HPLC-PCUV)). To differentiate N-nitro(so) compounds (i.e. UV-labile) from other nitro(so) and N-containing compounds (i.e. UV-resistant), a pre-treatment was established by photolyzing solid-phase extracted samples at 254 nm (1000 mJ/cm(2)) and thus removing N-nitro(so) compounds selectively. Considering a 1000-fold concentration factor and extraction efficiencies (57-83%) during solid phase extraction, the method detection limits ranged from 4 to 28 ng/L for dimethylnitramine and eight N-nitrosamines (EPA 8270 nine nitrosamines mixture except for N-nitrosodiphenylamine). For four pool waters, the UV-resistant groups accounted for more than 78% of the estimated total concentration of nitro(so) and other N-containing compounds (6.1-48.6 nM). Only one unknown UV-labile compound was detected in one pool water (2.0-7.9 nM). NDMA was most frequently detected and N-nitrosodipropylamine (NDPA) and N-nitrosodibutylamine (NDBA) were additionally detected in one pool water. Chloramination of a secondary wastewater effluent with NDMA (0.2 nM) and UV-resistant compounds (7.9 nM) from a pilot-scale municipal wastewater treatment plant led to a significant formation of not only unidentified UV-resistant compounds (67.8 nM) and UV-labile compounds (14.6 nM), but also identified nitrosamines such as NDMA (4.3 nM), N-nitrosopiperidine (1.8 nM), NDPA (0.5 nM), and NDBA (0.5 nM). Overall, the novel HPLC-PCUV system is a powerful screening tool for the detection of (un)known N-nitro(so) as well as other nitro(so) and UV-induced nitrite-producing compounds.

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Nitric oxide (NO) derivative of l-arginine is an important signaling molecule that mediates a variety of essential physiological processes including vasodilation neurotransmission, and host cell defense. Many types of cells produce NO e.g., smooth muscle cell, endothelial cell, and leukocytes. Host defense functions are known for many bacterial and parasitic infections. In the present study we estimated the levels of serum NO in cases of salmonellosis and in controls. The nitric oxide was estimated by cadmium reduction method, Griess reaction. We observed that in controls the level of NO was (22 ± 2.06) µmol/l and in cases the level was (137.49 ± 29.84) µmol/l. The level of NO was significantly higher than controls (p < 0.001). The raised level of NO could be accounted for by host response to the infection. The host rapidly expresses iNOS, which in turn produces an excess amount of NO. Its cytotoxic effect is by its reactive nitrogen oxide derivative e.g., peroxynitrite. Apart from this it also has anti apoptotic functions. In future one can do follow up study of typhoid cases by bacterial culture.