Colorimetric Detection Of Nitrite Research Articles

Dual-mode SERS/colorimetric sensing of nitrite in meat products based on multifunctional au NPs@COF composite

The presence of nitrite in food products has generated significant public concern. A simple and rapid dual-mode surface-enhanced Raman spectroscopy (SERS)/colorimetric detection of nitrite is proposed based on a diazo reaction and multifunctional gold nanoparticle-doped covalent organic framework (Au@COF) composite. Under acidic conditions, the reaction between toluidine blue and nitrite yielded a colorless diazo salt, simultaneously attenuating its characteristic absorption peak and Raman signal. The multifunctional Au@COF materials enhanced the Raman signal and ensured good reproducibility. Additionally, the reaction rates improved, and the sensitivity was enhanced due to the excellent adsorption capacity of the COF. The proposed method demonstrated high sensitivity and excellent recovery rates for nitrite detection in food samples. This approach shows potential for precisely detecting nitrite content in real-world food samples by integrating the simplicity of colorimetric analysis with the enhanced sensitivity of SERS.

The Eschenmoser's Salt as a Formylation Agent for the Synthesis of Indolizinecarbaldehydes and Their Use for Colorimetric Nitrite Detection.

C-H bond formylation is the most immediate way to incorporate the versatile formyl group into (hetero)aromatics. However, the type of reagents and severe conditions involved in the classical formylation methods often curtail their application, especially in the presence of other functional groups. Herein, we present the Eschenmoser's salt, a commercially available (dimethylamino)methylating chemical, as a useful reagent for the C-H formylation of indolizines and other compounds. The method is straightforward and mild, furnishing indolizinecarbaldehydes in modest-to-good yields with exclusive and remote regioselectivity. Furthermore, these compounds can be easily transformed into push-pull dyes and are highly selective in the colorimetric detection of nitrite, a substance extensively employed as preservative in the food industry, the concentration of which is crucial to control to prevent harmful effects in living organisms. The assay is simple, allowing the naked-eye detection of nitrite in solution or on a cotton swab for a wide range of concentrations.

The Eschenmoser's Salt as a Formylation Agent for the Synthesis of Indolizinecarbaldehydes and Their Use for Colorimetric Nitrite Detection

AbstractC−H bond formylation is the most immediate way to incorporate the versatile formyl group into (hetero)aromatics. However, the type of reagents and severe conditions involved in the classical formylation methods often curtail their application, especially in the presence of other functional groups. Herein, we present the Eschenmoser's salt, a commercially available (dimethylamino)methylating chemical, as a useful reagent for the C−H formylation of indolizines and other compounds. The method is straightforward and mild, furnishing indolizinecarbaldehydes in modest‐to‐good yields with exclusive and remote regioselectivity. Furthermore, these compounds can be easily transformed into push‐pull dyes and are highly selective in the colorimetric detection of nitrite, a substance extensively employed as preservative in the food industry, the concentration of which is crucial to control to prevent harmful effects in living organisms. The assay is simple, allowing the naked‐eye detection of nitrite in solution or on a cotton swab for a wide range of concentrations.

A Hydrogel-Based Chemosensor Applied in Conjunction with a Griess Assay for Real-Time Colorimetric Detection of Nitrite in the Environment

A Hydrogel-Based Chemosensor Applied in Conjunction with a Griess Assay for Real-Time Colorimetric Detection of Nitrite in the Environment

Design and Functionalization of a µPAD for the Enzymatic Determination of Nitrate in Urine.

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.

Rapid and unbiased colorimetric quantification of nitrite and ammonium ions released from 2,4,6-trinitrotoluene during biodegradation studies: Eliminating interferences

Worldwide contamination of soils and groundwater by 2,4,6-trinitrotoluene (TNT) has drawn considerable attention to bioremediation solutions. To evaluate the environmental relevance of a biodegradation process or to discover new TNT degrader microorganisms, effective and reliable monitoring strategies are essential, including the sensitive detection of inorganic nitrogen species released from TNT. In this study we describe improved colorimetric methods for a rapid and unbiased monitoring of nitrite and/or ammonium ions produced in TNT-biodegradation experiments. Considerable interferences in the colorimetric detection of nitrite by the Griess reaction were observed in the presence of various chemicals used in biodegradation assays including reduced pyridine nucleotides (NAD(P)H) and commonly used biological buffers and buffer constituents. In the colorimetric quantification of ammonium through the Berthelot reaction, significant interferences were generated by TNT itself and some reduced TNT metabolites. We highlight these pitfalls and give solutions to overcome these problems, including buffer selection, appropriate dilutions, oxidation of NAD(P)H and selective removal of TNT and some of its metabolites.

Multipumping Nitrite Determination in Exhaled Breath Condensate

A flow system based on multicommutation is proposed for the rapid, clean, and inexpensive determination of nitrites in small volumes of breath condensates. The procedure exploits the colorimetric detection of nitrite with the Griess reagent [0.03% naphthylethylene diamine dihydrochloride (NED), 0.5% sulpfhanilamide, and 3.0% phosphoric acid] in acidic medium at 540 nm correcting the variations of the baseline with measurements at 424 nm. The flow system was designed with a set of solenoid micropumps to minimize sample and reagent consumption and waste generation. The detection limit was estimated as 3.8 ng mL−1 (99.7% confidence level) with a linear response ranging up to 500 ng mL−1. The coefficient of variation was estimated as 0.7% for a solution containing 300 ng mL−1 nitrite (n=9). Approximately 144 determinations can be carried out per hour, consuming only 678.4 µg Griess reagent and generating 1.184 mL of effluent per determination, thus providing an environmentally friendly alternative and a nonexpensive method. The procedure was successfully applied to determine nitrite in breath condensates. The authors were invited to contribute this paper to a special issue of the journal entitled “Spectroscopy and Automation”. This special issue was organized by Miguel de la Guardia, Professor of Analytical Chemistry at Valencia University, Spain.