Spectrophotometric Determination of Trace Nitrite with Brilliant Cresyl Blue Using β-Cyclodextrin as a Sensitizer

Nitrate, nitrite and nitrosamines in the global food supply

Inorganic nitrate provided by either nitrate salts or food supplements may improve cardiometabolic health. However, current methods to assess dietary nitrate, nitrite and nitrosamine consumption are inadequate. The purpose of this study was to develop a reference database to estimate the levels of nitrate, nitrite and nitrosamines in the global food supply. A systematic literature search was undertaken; of the 5,747 articles screened, 448 met the inclusion criteria. The final database included data for 1,980 food and beverages from 65 different countries. There were 5,105 unique records for nitrate, 2,707 for nitrite, and 954 for nitrosamine. For ease of use, data were sorted into 12 categories; regarding nitrate and nitrite concentrations in food and beverages, 'vegetables and herbs' were most reported in the literature (n = 3,268 and n = 1,200, respectively). For nitrosamines, 'protein foods of animal origin' were most reported (n = 398 records). This database will allow researchers and practitioners to confidently estimate dietary intake of nitrate, nitrite and nitrosamines. When paired with health data, our database can be used to investigate associations between nitrate intake and health outcomes, and/or exercise performance and could support the development of key dietary nitrate intake guidelines.

A rapid and sensitive evaluation of nitrite content in Saudi Arabian processed meat and poultry using a novel ultra performance liquid chromatography-mass spectrometry method

Quantitative assessment of nitrite (NO₂^-) anion was performed using a newly developed high throughput ultra performance liquid chromatography-mass spectrometric (UPLC-MS) method. The nitrite determination with the proposed method using micellar mobile phase was unknown. Selected ion reaction mode using negative electrospray ionization was adopted for the identification and quantitative analysis of nitrite. The chromatographic separation was performed using BEH C-18 column and a micellar mobile phase consisted of sodium dodecyl sulphate and acetonitrile in ratio 30:70 was used. The elution of nitrite anion was accomplished in less than 1 min. Under the optimal analysis conditions, the linearity of the developed method was checked in the concentration range of 0.5-20 mg kg^-1 NO₂^- with an excellent correlation coefficient of 0.996. The precisions of the method with relative standard deviation <2% was observed when standard at concentration of 1 mg kg^-1 was used. The limit of detection and limit of quantitation of the developed mass spectrometric method was found to be 0.114 and 0.346 mg kg^-1, respectively. The developed UPLC/MS method was applied to quantify this anion in processed meats and poultries from various super market of Saudi Arabia (Riyadh region). The recoveries of the nitrite in the various samples were found in the range of 100.03-103.5%.

Development of a cloud point extraction and spectrophotometry-based microplate method for the determination of nitrite in human urine and blood

A novel and simple method for the sensitive determination of trace amounts of nitrite in human urine and blood has been developed by combination of cloud point extraction (CPE) and microplate assay. The method is based on the Griess reaction and the reaction product is extracted into nonionic surfactant Triton-X114 using CPE technique. In this study, decolorization treatment of urine and blood was applied to overcome the interference of matrix and enhance the sensitivity of nitrite detection. Multi-sample can be simultaneously detected thanks to a 96-well microplate technique. The effects of different operating parameters such as type of decolorizing agent, concentration of surfactant (Triton X-114), addition of (NH4)2SO4, extraction temperature and time, interfering elements were studied and optimum conditions were obtained. Under the optimum conditions, a linear calibration graph was obtained in the range of 10-400 ng mL(-1) of nitrite with limit of detection (LOD) of 2.5 ng mL(-1). The relative standard deviation (RSD) for determination of 100 ng mL(-1) of nitrite was 2.80%. The proposed method was successfully applied for the determination of nitrite in the urine and blood samples with recoveries of 92.6-101.2%.

The Determination of Nitrate and Nitrite in Human Urine and Blood by High-Performance Liquid Chromatography and Cloud-Point Extraction

A simple efficient and practical separation/preconcentration coupled with HPLC method for the determination nitrate and low concentrations of nitrite in human urine and blood was investigated. The method is based on precolumn derivatization using the Griess reaction and cloud-point extraction (CPE) of nitrite anion and direct determination of nitrate using its UV absorbance by ion-pair HPLC. The chromatographic process with detection at two wavelengths (510 and 220 nm) allows the determination of nitrite and nitrate. Decolorization and protein precipitation of urine and blood was applied to overcome the interference of matrix and enhance the sensitivity. The method was validated for linearity, accuracy and precision. Under the optimum conditions, the linear range of nitrite from 10 to 1,000 ng/mL and nitrate from 0.1 to 10 µg/mL. Product recoveries ranged from 92.4 to 99.9%. The limits of detection were 1 ng/mL and 0.1 µg/mL for nitrite and nitrate, respectively. Therefore, the technique was simple and reliable, with potential application in biological sample analysis of nitrate and nitrite.

A new catalytic-spectrophotometric method for quantification of trace amounts of nitrite in fruit juice samples

A new kinetic method has been developed for the determination of nitrite in fruit juice samples. The method is based on the catalytic effect of nitrite with the oxidation of Nile Blue A (NBA) by KBrO(3) in the sulfuric acid medium. The optimum conditions obtained are 1.2 mM sulfuric acid, 0.034 mM of NBA, 2.8 × 10(-3) M KBrO(3), reaction temperature of 20 °C, and reaction time of 100 s at 595.5 nm. Under the optimized conditions, the method allowed the quantification of nitrite in a range of 0.2-800 μg/mL with a detection limit of 0.02 μg/mL. The method was applied to the determination of nitrite in 15 brands of fruit juice samples.