Development of a Simple and Accurate Analytical Method for the Determination of Nitrite in Processed Meat Products by Using an Optical Solid Chemosensor and Smartphone

A smartphone-assisted ratiometric colorimetric and fluorescent probe for triple-mode determination of nitrite based on MnO2 nanoparticles and carbon quantum dots

A triple-mode colorimetric and fluorescent sensing scheme based on manganese dioxide nanoparticles (MnO₂NPs) and carbon quantum dots (CQDs) were developed to determine nitrite. MnO₂NPs can oxidize 3,3',5,5'-tetramethylbenzidine (TMB) into a blue oxidation product (TMBox), which is further oxidized into a yellow diimine derivative by nitrite. The ratio of absorbance at 652 nm to 452 nm was monitored as signal response for UV-vis detection mode. A "turn-off" CQDs fluorescence probe was also constructed for fluorescent detection mode. Smartphone tool kit was used to capture the color of sample for smartphone-based measurement. Various analytical performance under different detection modes were obtained and compared. The proposed methods were applied to food samples with satisfactory recoveries (83.3-106 %). The results were validated with AOAC standard spectrophotometric method. The current triple-mode detection were accurate, convenient, low-cost and fast for analyzing nitrite in foods and water samples on-site.

Development of a simple analytical method for the determination of nitrite in waters using redox reaction and smartphone

In this study, it was aimed to perform the colorimetric determination of nitrite in waters using the redox reaction of iodide in acidic conditions with smartphone. The simple redox reaction of iodide and nitrite in an acidic medium was used instead of the conventional nitrite methods based on the formation of azo dye. The quantitative relationship between the yellow-colored iodine formed because of the reaction and nitrite was determined by the digital image-based colorimetric method (DIC). In the optimal experimental conditions, detection limit and R² values were determined as 0.02 mg/L and 0.9925, respectively. New method (Redox-DIC method) was validated by the standard Griess Method for nitrite in lake waters. The perfect recovery results (94-112%) were calculated for lake, river, tap, and spring waters spiked at different concentrations, and very good (< 5.0%) percent relative standard deviation values were recorded. Unlike conventional nitrite methods, organic reagents and solvents were not used in this method. The method is fast, simple, and low cost.