Spectrophotometric Determination Of Nitrite Research Articles

Feedback standard addition method coupled flow injection analysis – Validation by spectrophotometric determination of nitrite in seawater

The standard addition method is a powerful tool to eliminate matrix interferences and enables accurate determinations, but it is time-consuming and labor-intensive. This paper proposes a feedback standard addition method coupled flow injection analysis, FB-SAM/FIA, for the rapid and accurate determination of trace interest in seawater samples. This approach automatically prepares spiked samples by feeding back the peak height in the fiagram, thus significantly improving the sample throughput compared to the manual standard addition method. Spectrophotometric determination of NO2− with the Griess assay was used as an evaluation model. The proposed technique demonstrated a sample throughput of 3 samples/h, ranging from 0.0050 mg L−1 (LOD) to 0.125 mg L−1 NO2−. The accuracies of NO2− determination with FB-SAM/FIA and an absolute calibration method were tested using natural seawater and pseudo-seawater samples containing 0.040 mg L−1 NO2− in 0, 1, 2, 3, and 4 % sodium chloride media. With the absolute calibration method, the calculated concentration increased with an increase in salinity, reaching an overestimation of about 40 %. On the other hand, FB-SAM/FIA suppressed the errors in the range of −7.8 % to 1.3 % and applied successfully to the determination of NO2− in the natural seawater samples.

Spectrophotometric determination of nitrite in curing meat samples basing on the nitrosation reaction

A new Spectrophotometric method for the determination of nitrite ion was studied. The method is based on the nitrosation reaction of nitrite ion with tryptophan in sulphuric acid medium. During it's reaction with nitrite, an intensively yellow-coloured substance is formed, having maximum absorption at 440nm. The calibration curve showed that Beer s law obeyed over the range of 0.05-3.0μg/ml of nitrite, with a detection limit of 0.00μg/ml. The molar absorptivity and Sandell index were 1.3887*104 L/mol.cm and 0.00331μg/cm2 respectively. The optimum conditions affecting and interferences of the foreign ions were studied. The results obtained of the proposed method for determination of nitrite in meat samples were agreed with those obtained by the Naphthyl ethylene diamine NEDA standard method.

Spectrophotometric Determination of Nitrite and Nitrate in Some Selected Vegetables Cultivated in Adami Tulu Judo Kombolicha District Farms, Ethiopia

Spectrophotometric Determination of Nitrite and Nitrate in Some Selected Vegetables Cultivated in Adami Tulu Judo Kombolicha District Farms, Ethiopia

Solid-phase spectrophotometric iodometric determination of nitrite and selenium(IV) using a polymethacrylate matrix

Procedures for the iodometric solid-phase spectrophotometric determination of nitrite and selenium( IV) using a polymethacrylate matrix are proposed. The procedures are based on the reaction of nitrite and selenium(IV) with iodine in an acidic medium with the release of free iodine in amounts equivalent to those of the substances to be determined, extraction of the iodine formed with a polymethacrylate matrix, and measurement of absorbance of the matrix at 370 nm. The developed procedures ensure the determination of 0.01–0.12 mg/L of nitrite and 0.05–0.40 mg/L of selenium(IV) with limits of detection of 0.005 and 0.03 mg/L, respectively. It was shown that the proposed procedures can be applied to the determination of selenium(IV) in mineral water and nitrites in vegetables and soil.

Spectrophotometric determination of nitrite in cured meat products

O mercado de embutidos tem apresentado grande expansão e alta competitividade na última década, uma vez que o consumo de produtos cárneos como salsichas, linguiças e mortadelas tem se tornado cada vez mais presente no hábito alimentar da população brasileira. Sais de cura, como nitrato e nitrito de sódio e de potássio, são largamente utilizados como aditivos alimentares no processamento de produtos cárneos e têm a finalidade de conservar, intensificar ou modificar as propriedades sensoriais dos alimentos. Este trabalho teve como objetivo determinar o teor de nitrito em embutidos comercializados na cidade de Avaré - SP e região através do método espectrofotométrico. Os embutidos utilizados na pesquisa foram mortadelas, salsichas e linguiças frescais. Foi analisado um total de 270 amostras de embutidos de três diferentes marcas cada. A determinação do íon nitrito foi realizada através do método espectrofotométrico a 540 nm. A presença de nitrito estava em todas as amostras dos produtos cárneos analisados, cujas concentrações médias variaram de 29,25 ppm a 249,80 ppm. Entre os embutidos, a linguiça das marcas A e C apresentaram um teor de nitrito superior ao permitido na legislação brasileira (máximo 150 ppm). Conclui que medidas de controle de produção de linguiça frescal e educação sanitária poderiam ser aplicadas com mais rigor em indústrias e estabelecimentos comerciais a fim de se garantir produtos de maior qualidade e seguros quanto ao teor de nitrito em sua composição.

Determination of Nitrite in Food Samples by Kinetic Spectrophotometric Data and Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS)

Herein, a method for spectrophotometric determination of nitrite in food samples with complex matrices is developed. The method is based on the standard addition and collecting kinetic data of the reaction of nitrite with 4-amino-3-hydroxynaphthalene-1-sulfonic acid (AHNSA) and 1-naphthylamine. Standard additions were made based on the linear range of the method using the above reagents. Kinetic data of different standard additions were augmented and subsequently analyzed by multivariate curve resolution-alternating least squares (MCR-ALS) to achieve second-order advantage. The proposed method was applied to real samples, and 19.86, 19.68, 1.38, 2.50, and 4.00 mg kg−1 of nitrite was found in cheese, tomato paste, sausage, hamburger, and kielbasa, respectively. The results were validated by a standard method.

Aqueous Two-Phase Extraction and Spectrophotometric Determination of Nitrite in Food Samples

An ethanol-(NH 4 ) 2 SO 4 aqueous two-phase system has been applied to the extraction and spectrophotometric determination of nitrite. The complex formed by nitrite and methyl orange was extracted to the upper ethanol phase and was measured at 432 nm. The concentration of nitrite varies linearly with the absorbance over the range of ~0.5–6.0 mg/l. The proposed method has been applied to the determination of nitrite in food samples. The analytical results obtained by this method and the naphthyl ethylenediamine spectrophotometric method were in good agreement.

NITRITE REMOVAL FROM AQUEOUS SOLUTION USING SURFACE MODIFIED MAGHEMITE NANOPARTICLES

In the present work, maghemite nanoparticles (MNP) was synthesized by a simplified method and then modified by sodium dodecyl benzene sulfonate (NaDBS) for the removal of nitrite from aqueous solution. The prepared nanoparticles were characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The SEM image and XRD analysis showed that the average particle size and crystallite of the maghemite nanopaticles are ca. 32.7 nm and 33.5 nm, respectively. Different parameters namely, pH of the adsorption solution, adsorbent dosage and spectrophotometric reagents were optimized. Spectrophotometric determination of nitrite in an optimized condition showed that the MNP is able to deplete over 88% of nitrite from the initial solution. Moreover, dynamic adsorption study per se confirmed the shortest necessary contact time (ca. 6 min) in the adsorption process of nitrite which is quite encouraging from a practical and industrial point of view. The kinematic study revealed that the nitrite adsorption is a pseudo-first-order process. In addition, two different models (Freundlich- and kinetic-type model) were developed for the adsorbent dosage effect on nitrite adsorption. A Freundlich-type model manifested high coefficients of regression, indicating its robustness.

Iodine speciation in coastal and inland bathing waters and seaweeds extracts using a sequential injection standard addition flow-batch method

The present work describes the development of a sequential injection standard addition method for iodine speciation in bathing waters and seaweeds extracts without prior sample treatment. Iodine speciation was obtained by assessing the iodide and iodate content, the two inorganic forms of iodine in waters. For the determination of iodide, an iodide ion selective electrode (ISE) was used. The indirect determination of iodate was based on the spectrophotometric determination of nitrite (Griess reaction). For the iodate measurement, a mixing chamber was employed (flow batch approach) to explore the inherent efficient mixing, essential for the indirect determination of iodate. The application of the standard addition method enabled detection limits of 0.14µM for iodide and 0.02µM for iodate, together with the direct introduction of the target water samples, coastal and inland bathing waters. The results obtained were in agreement with those obtained by ICP-MS and a colorimetric reference procedure. Recovery tests also confirmed the accuracy of the developed method which was effectively applied to bathing waters and seaweed extracts.

Spectrophotometric determination of nitrite by its catalytic effect on the oxidation of congo red with bromate

A novel simple, sensitive and rapid kinetic-spectrophotometric method for the determination of trace amounts of nitrite is proposed. The method is based on its catalytic effect on the oxidation of congo red (CR) by potassium bromate in acidic solution. The oxidation reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of CR at a suitable λ max = 570 nm for the first 10–40 s from the start of the reaction. Under the optimum experimental conditions (sulfuric acid, 0.3 M; CR, 0.75x10 -4 M; potassium bromate, 5x10 -4 M and 25 o C), nitrite can be determined in the range of 0.015–0.75 µg mL −1 with the detection limit of 0.006 µg mL −1 . The relative standard deviation of five replicate determination of 0.25 µg mL −1 nitrite was 2.5%. The proposed method was applied satisfactorily to the determination of nitrite in spiked drinking water samples. KEY WORDS : Nitrite, Catalytic effect, Congo red, Spectrophotometry, Drinking water Bull. Chem. Soc. Ethiop. 2012 , 26(2), 159-169. DOI: http://dx.doi.org/10.4314/bcse.v26i2.1

Indirect cloud point extraction and spectrophotometric determination of nitrite in water and meat products

A new indirect micelle mediated cloud point extraction method has been developed for sensitive determination of trace amounts of nitrite by spectrophotometry. The method is based on the well known oxidation–reduction reaction of nitrite by iodide ion in acidic medium and cloud point extraction of I3− formed from aqueous solution using Triton X-100. The extracted surfactant rich phase is diluted with water and its absorbance is measured at 365nm. The effects of different operating parameters such as concentration of surfactant, KI concentration, temperature, incubation time and acid concentration on the cloud point extraction were studied in details and a set of optimum conditions was obtained. A linear calibration graph was obtained in the range of 8–120ngmL−1. The limit of detection (LOD) based on three times the standard deviation of the blank (3Sb) was 6.0ngmL−1 (n=10) and the relative standard deviation (RSD) for determination of 60ngmL−1 of nitrite was 3.40% (n=10). The method was applied to the determination of nitrite in meat products and water samples.

Kinetic Spectrophotometric Determination of Nitrite with Tropaeolin 00-Bromate System

A simple accurate kinetic spectrophotometric method was developed for the determination of nitrite based on its catalytic effect on the redox reaction between tropaeolin 00 and bromate in acid medium. Nitrite was determined by measuring the decrease in the absorbance of tropaeolin 00 at 530 nm by a fixed time method, after 30 s from the initiation of the reaction. The calibration graph was linear in the range 6–500 ng mL−1 of nitrite and the detection limit was 2 ng mL−1. The proposed method is selective and is useful for the determination of nitrite in drinking water samples.

Spectrophotometric Determination of Nitrite in Water Samples with 4‐(1‐Methyl‐1‐Mesitylcyclobutane‐3‐yl)‐2‐Aminothiazole

A simple, sensitive, and specific spectrophotometric method for the measurement of nitrite in water has been developed and optimum reaction conditions along with other analytical parameters have been evaluated. The azo dye, 4‐(1‐methyl‐1‐mesitylcylobutane‐3‐yl)‐2‐(p‐N,N‐dimethylazobenzene)‐1,3‐thiazole was synthesized with the reaction of 4‐(1‐methyl‐1‐mesitylcylobutane‐3‐yl)‐2‐aminothiazole and N,N‐dimethyl aniline in acidic medium. Obtained azo dye has been characterized by infrared (IR), 1H nuclear magnetic resonance (NMR), and microanalysis methods. The dye shows an absorption maximum at 482 nm. The method is optimized for acid concentration, pH, amount of reagents required, time, and interfering species. All the determinations were carried out at this wavelength throughout the work. At an analytical wavelength of 482 nm, Beer's law is obeyed over the concentration range 0.05 to 2.00 µg nitrite per mL analyte. The molar absorptivity, Sandell's sensitivity, and relative standard deviation are 2.03×104 L mol−1 cm−1±251.3 (95%), 2.28×10−3 µg cm−2, and 2.74% (n=10), respectively. The detection limit of the method is 0.012 µg ml−1 of nitrite ion. The method was succesfully applied to the determination of nitrite in tap water and lake water.

Kinetic Spectrophotometric Determination of Nitrite Based on Its Catalytic Effect on the Oxidation of Methyl Red by Bromate

A precise, sensitive, and accurate catalytic spectrophotometric method for the determination of nitrite in food stuff is presented. In acidic solution, methyl red (MR) is oxidized by bromate to form a colorless compound. The reaction is accelerated by trace amounts of nitrite and can be followed by measuring the absorbance at 520 nm. The absorbance of the reaction mixture decreases with increasing time and reaches to a minimum that is inversely related to the nitrite concentration. The change in absorbance at 25 and 50 sec was calculated as an analytical signal. Under the optimum experimental conditions (0.3 M sulfuric acid, 1.1 × 10−5 M MR, 2.6 × 10−4 M bromate, 0.2 M nitrate, and 25°C), nitrite can be determined in the range of 0.05–1.2 µg g−1. The standard deviation is 0.06 for six replications at 0.3 µg g−1.The detection limit as the mean of the blank signals plus three times the blank standard deviation is 0.045 mg kg−1. The method was successfully applied for the determination of nitrite in meat products.

Spectrophotometric Determination of Nitrite and Nitrate in Cured Meat by Sequential Injection Analysis

ABSTRACT: A robust, automated, labor‐saving, accurate, and economical sequential injection system was developed for simultaneous determination of nitrite and nitrate in cured meat samples, based on the Shinn reaction. Nitrite is coupled and diazotized with sulfanilamide and N‐(1‐naphtyl)‐ethylenediamine dihydrochloride, to form a colored compound that absorbs at 538 nm. Nitrate is previously in‐line reduced to nitrite in a copperized cadmium column and measured as nitrite. The solutions' aspiration sequence, the influence of reagent and buffer concentrations, the manifold parameters, and the characteristics of the reducing column were studied. Nitrite and nitrate can be determined within the 0.030 to 1.22 of N‐NO2− and 0.034 to 3.95 mg/L of N‐NO3− ranges, respectively, at a sampling rate of 9/h. Detection limits of 9 μg/L of N for nitrite and 9 μg/L of N for nitrate were obtained, and the conversion rate of nitrate to nitrite was 100.6%± 1.8%. The results were in good agreement with those obtained by the reference methods, with relative standard deviations (r.s.d.) better than 3.70% for nitrites and 2.42% for nitrates.

A Facile Spectrophotometric Determination of Nitrite Using Diazotization with p-Nitroaniline and Coupling with Acetyl Acetone

A simple and sensitive spectrophotometric method is described for the determination of nitrite in water and soil samples. The method is based on the reaction of nitrite with p-nitroaniline to form a diazonium ion, which is coupled with a new coupling agent, acetyl acetone in an alkaline medium. The dye shows an absorption maximum at 490 nm and obeys Beer’s law over a range of 0.5 to 14 µg nitrite per 10 mL analyte. The molar absorptivity of the colour system is 3.2×104 L mol−1 cm−1. The relative standard deviation is 2.7% (n = 10). The dye formed is stable for 3 h. The effect of interfering ions on the determination is described. The method has been suggested for the determination of nitrite in water and soil samples. The results obtained were compared with the standard N-(1-naphthyl) ethylenediamine dihydrochloride method.

Sensitive Spectrophotometric Determination of Nitrite in Human Saliva and Rain Water and of Nitrogen Dioxide in the Atmosphere

A new simple, sensitive, and selective spectrophotometric method was developed for the determination of nitrite. The method is based on the reaction of nitrite with sulfathiazole in acidic medium to form a diazonium cation, which is subsequently coupled with N-(1-naphthyl)ethylenediamine dihydrochloride to form a highly stable, violet azo dye. The reaction product has an absorption maximum at 546 nm and obeys Beer's law over a nitrite range of 0.054-0.816 microg/mL. The molar absorptivity of the colored compound is 4.61 x 10(4) L/mol x cm). The detection limit is 12.1 microg/L. The relative standard deviation is 0.85% for 5 determinations of nitrite at 0.27 microg/mL. The reproducibility and validity of the proposed method are discussed in the present paper. The simplicity of the method is demonstrated by the high stability of the azo-dye product as well as the short time required for its complete formation in a reaction at room temperature without pH control or extra extraction. The sensitivity of the method is shown by the successful determination of nitrite in human saliva and rain water, and of nitrogen dioxide in the atmosphere. The results compare favorably with those obtained by the reference method. The selectivity of the method is indicated by its freedom from most interferences, even at high concentrations of nitrate (500 microg/mL).

Simultaneous Spectrophotometric Determination of Nitrite and Nitrate in Water Samples by Flow-Injection Analysis

An automatic direct spectrophotometric method for the simultaneous determination of nitrite and nitrate by flow-injection analysis has been developed. The method is based on the reaction of nitrite and nitrate with the spectrophotometric reagent N-phenylanthranilic acid in sulfuric acid medium (pH=0.4∼0.6) to form the same color products while the absorbance is measured at 410 nm. This method has the advantage of direct determination of nitrite and nitrate and without reducing nitrate to nitrite as other reported methods. Various analytical parameters, such as flow rate, sample size, effect of acidity(pH), reagent concentration and interfering species were studied. The detection limit is 2.5 ng ml−1 for nitrite and 12 ng ml−1 for nitrate. Up to 35 samples per hour can be analyzed with a relative precision of ca. 0.1–2%.

Sequential injection spectrophotometric analysis of nitrite in natural waters using an on-line solid-phase extraction and preconcentration method

An automatic sequential injection analysis (SIA) set-up for the isolation, preconcentration and spectrophotometric determination of nitrite in waters based on the Shinn reaction was designed and evaluated. The system performs the on-line azo dye formation and its subsequent extraction on a solid phase (monofunctional C18), which is held inside a glass column incorporated into the system. A large sample volume (maximum, 10 ml) is sequentially segmented with sulfanilamide and N-(1-naphthyl)ethylenediamine dihydrochloride by using an iterative method. The azo dye collected is eluted with a small volume of 80% methanol and conducted to a diode-array spectrophotometer for quantitative analysis. It has been proved that the retention efficiency is maintained for up to 45 sample injections of 10 ml in spite of the high chromogenic reagent acidity. Nitrite has been determined within the 13.4–160 ng ml−1 and 0.83–20 ng ml −1 ranges for 1 and 10 ml of sample, respectively. For these volumes, the detection limits are 5.9 and 0.32 ng ml −1, the enhancement factors 17 and 170 and the sample throughput 15 and 3 h−1, respectively. A maximum RSD of 4.0% was achieved in all determinations. It is an advantage of this approach that it is possible to use the same mass calibration graph for any sample volume.

Spectrophotometric Determination of Nitrite in Water

Spectrophotometric Determination of Nitrite in Water