Spectrophotometer Determination of Nitrite Using Salbutamol sulphate as a Reagent

Abstract

A simple spectrophotometric method for the trace determination of nitrite (NO^? ₂) is described. Nitrite is reacted with Salbutamal sulphate in acidic medium which gives a yellow colour in alkaline medium (?pH 7) and can be determined in the presence of several cations and anions. Beer's law is obeyed in the range of 1.8 to 27.6 ppm of nitrite with the molar absorptivity 1.8 × 10³ 1 × mole^?1 × cm^?1 at 4l0 nm. The proposed method can also be utilized for the determination of nitrate (NO^? ₃) after its reduction to nitrite. The method has been applied for the determination of various samples containing traces of nitrite.     

Spectrofluorimetric Determination of Nitrite with Pyridoxal-5-Phosphate-2-Pyridylhydrazone

Abstract

The nitrite ion oxidizes pyridoxal-5-phosphate-2-pyridyl-hydrazone in acid medium giving a fluorescent product (λ_ex 325 nm, λ_em 420 nm). This redox reaction is used to developed a spectrofluorimetric method for the determination of nitrite. The calibration graph is liner in the 0.1 ? 1.0 μg mL^?1 range. The interference levels, stoichiometry and nature of the reaction have been studied. The method is applied to determine nitrite in water and soil samples     

Kinetic Flow Injection Spectrophotometric Determination of Nitrite by its Catalytic Effect on the Oxidation of Chlorophosphonazo-pN by Bromate

Abstract

A flow injection kinetic method has been developed for the determination of nitrite, based on its catalytic effect on bromate oxidation of chlorophosphonazo-pN in H₂SO₄ medium. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance at 551 nm. The sampling frequency was 83 h^?1. The calibration curve was linear between 0.050 and 1.00 μg/ml, and the detection limit was 0.018 μg/ml. The proposed method was applied to the determination of nitrite in waters and soil with satisfactory results.     

Determination of Nitrite by a New Spectrophotometric Method Using Safranin

Abstract

A spectrophotometric method was developed to determine nitrite using safranin as color reagent. The reaction between nitrite and safranin produces a safranin-HNO₂ species, which exhibits absorption peaks at 280, 349, 420(shoulder) and 610 nm. The peak at 610 nm was chosen as the analysis wavelength because nitrite ion and safranin do not present absorption bands in this region. The Lambert-Beer law was obeyed in the concentration range 7.0 × 10^?6 - 5.0 × 10^?5M. The effects of various ions on absorbance of the safranin-HNO₂ species were studied; the nitrite analysis can be performed without interference in the presence of the ions SCN^?, Br^?, CH₃COO^?, Cl^? (≤ 1.0 × 10^?3 M) and NO₃ ^? (< 1.0 × 10^?5 M). The SO₄ ⁼ does not interfere even at a concentration of 0.25M.     

Diaminobenzene as a Novel Reagent for Nitrite Assay in Environmental Samples: Evidence for Its Mechanistic Aspects

Abstract

o-Phenylenediamine has been used as a reagent to quantify nitrites/nitrates in a variety of sample matrices. The method is based on the cyclization reaction between o-phenylenediamine and nitrite in acid medium. The amine undergoes diazotization with nitrite in the presence of acid to form the diazonium ion, which subsequently cyclizes to yield yellowish orange benzotriazole at room temperature with an absorption maximum at 450 nm. The formed dye has been separated, purified, and characterized by IR, NMR, and spectroscopy techniques. The parameters of the reaction between amine and nitrite have been optimized. The effect of interfering ions on the determination of nitrites/nitrates has been described. The developed method has been applied for the determination of residual NO₂ gas present in the ambient air after fixing it as a nitrite ion using sodium arsenite as a trapping medium. The dye formed has been extracted into organic solvent to improve the detection limit during the measurement of low levels of ambient NO₂ in air. The method obeyed Beer's law in the concentration range 0–250 µg in aqueous medium and 0–50 µg in organic medium with molar absorptivity of 4.09 × 10⁴ L mol^?1 cm^?1 and 4.3 × 10⁴ L mol^?1 cm^?1 respectively. Nitrate is determined by reducing it to nitrite after passing through the copperized cadmium reductor column. The developed method has been applied to determine nitrite/nitrate levels in water, soil, and biological samples.     

Spectrophotometric Determination of Nitrogen Dioxide <Nitrite>

Abstract

A highly sensitive spectrophotometric method has been developed for the determination of nitrogen dioxide (nitrite as NO_z ^?) by reacting manganese dioxide in 1:20 perchloric acid. An amount of manganese dioxide (MnO_z) equivalent to the concentration of nitrogen dioxide becomes soluble due to the reduction of Mn (IV) to Mn (II) by nitrite in acidic medium. The soluble Mn (II) ion is filtered to remove excess of MnO₂ and is oxidized to permanganate ion by periodic acid in presence of phosphoric acid. The violet colored solution shows maximum absorbance at 525 nm. The sensitivity of the method is 0.08 ppm based on 0.0044 absorbance, and Beer's law is obeyed in the concentration range of 0.2 to 10.0 μg/mL of NO₂ ^?. Molar absorbance is found to be 2442 at 525 nm.

In the present investigation NO₂ ^? was treated with excess of MnO₂ in 1:20 perchloric acid where NO₂ ^? reduces equivalent amount of Mn (IV) to Mn (II) and becomes soluble. The soluble Mn (II) was heated to boiling and 25 mg (approx.) periodic acid is added and cooled. The volume of each solution is made to 50 mL in volumetric flask. Reagent blank is prepared in similar way except sodium nitrite solution. The absorbance is measured at 525 nm against reagent blank.     

The Catalytic Cycle of Oxidation of Iodide Ion in the Oxygen/Nitrous Acid/Nitric Oxide System and Its Potential for Analytical Applications

Abstract

The oxidation of iodide to iodine by nitrous acid in aqueous acidic medium takes place catalytically in the presence of dissolved oxygen and can be followed spectrophotometrically at 288 and 352 nm. An indirect molar absorptivity for nitrite on the basis of I₃ ^? formation can be as high as 8.5×10⁵ L mol^?1 cm^?1 at 288 nm. Analytical curves were established. The iodine released in the catalytic cycle can also be titrated with thiosulfate. The reaction is pseudo–second‐order in oxygen consumed, with t_1/2=15.7 min at 25°C. A rate determining step could be the NO · O₂ as the activated species. Measurements of the iodine formed at catalytic conditions was used to determine nitrite in meat extracts and NOx in car exhausts.     

Selective Kinetic Spectrophotometric Determination of Nitrite in Food and Water

Abstract

A highly selective and sensitive method for the kinetic spectrophothometric determination of sub-microgram amounts of nitrite has been development based on its reaction with Nile blue 2B in acidic medium. The reaction is monitored spectrophotometrically at 595 nm at a fixed time of 4.5 min. The change in absorbance at 595 nm is related to the concentration of nitrite in the range 0.005 - 1.100 μg.ml^?1 The detection limit is 0.001 μg.ml^?1. The relation standard deviation is 1% for 0.020 μg.ml^?1 of nitrite for ten replicate measurements. Most common anions and cations do not interfere. The procedure was applied to the determination of trace amounts of nitrite in sausage and water.     

Electrocatalytic Reduction of Nitrite by Phosphotungstic Heteropolyanion. Application for Its Simple and Selective Determination

Three couples of reversible redox peaks of the PW₁₂O₄₀^3? (PW₁₂) anion, which are composed of two one‐electron and one two‐electron processes occur in the potential range from +0.25 to ?0.7 V in aqueous solutions. The electrocatalytic reduction of nitrite has been studied by the first redox couple of the PW₁₂ anion at the surface of a carbon paste electrode. Cyclic voltammetric and chronoamperometric techniques were used to investigate the suitability of PW₁₂ anion as a mediator for nitrite electrocatalytic reduction in aqueous solution with strongly acidic concentration of H₂SO₄. Results showed that H₂SO₄ 1.00 M is the best medium for this purpose. In the optimum concentration of H₂SO₄, the electrocatalytic ability about 500 mV can be seen and the homogeneous second‐order rate constant (k_s) for nitrite coupled catalytically to PW₁₂ anion was calculated as 2.52×10³ M^?1 s^?1 using the Nicholson–Shain method. According to our voltammetric experiments, the catalytic reduction peak current was linearly dependent on the nitrite concentration and the linearity range obtained was 3×10^?5 to 1.00×10^?3 M. The detection limit has been found to be 2.82×10^?5 M (2σ). This method has been applied as a selective, simple, and precise method for determination of nitrite in real samples.     

Determination of Nitrite in Aqueous Solutions using the Linear Sweep Voltammetry Technique

ABSTRACT

An electrochemical method using linear sweep voltammetry techniques was developed to determine nitrite ion in aqueous solution in the presence of nitrate. Nitrite solutions exhibited a well-defined oxidation wave at +1.0V vs SCE at vitreous carbon, while no oxidation process was observed for nitrate solutions. The pH of the nitrite solutions varied from 2.37 to 5.60 and no change was observed in the Ep values, except for the pH 5.60 solution, where little change was verified. The potential also did not vary with change in the nitrite concentration in the 5.0 x 10^?5 to 7.0 x 10^?4 mol L^?1 range. Very good straight lines for plots of current versus nitrite concentration in the 7.0 x 10^?5 to 7.0 x 10^?4 mol L^?1 range were obtained; the correlation coefficient was never worse than 0.990. The nitrite determination was also performed in the presence of 1.0 x 10^?3 mol L^?1 of NO₃ ^? ions. The addition of NO₃ ^? did not change significantly the current values even when it was added in one hundred times molar excess.     

Detection of trace nitrite in waters using a QDs-based chemiluminescence analysis system

In the present work, a novel flow-injection chemiluminescence method based on CdTe quantum dots (QDs) was developed for the determination of nitrite. Weak chemiluminescence (CL) signals were observed from a CdTe QDs–H₂O₂ system under basic conditions. The addition of a trace amount of hemoglobin (Hb) caused the CL from the CdTe QDs–H₂O₂ system to increase substantially. In the presence of nitrite, the ferrous Hb reacted with the nitrate to form ferric Hb and NO. The NO then bound to ferrous Hb to generate iron nitrosyl Hb. As a result, the CL signal from the CdTe QDs–H₂O₂–Hb system was quenched. Thus, a flow-injection CL analytical system for the determination of trace nitrite was established. Under optimum conditions, there was a good linear relationship between CL intensity and the concentration of nitrite in the range 1.0?×?10^?9 to 8.0?×?10^?7 mol L^?1 (R ²?=?0.9957). The limit of detection for nitrite using this system was 3.0?×?10^?10 mol L^?1 (S/N?=?3). This method was successfully applied to detect nitrite in water samples.

An Extractive Spectrophotometric Method for the Determination of Nitrite Using Fluorescein Amine Isomer I

ABSTRACT

A sensitive spectrophotometric method for the determination of nitrite using fluorescein amine isomer I is described. The method is based on the formation of azido derivative of fluorescein amine isomer I, which is selectively extracted into 20% iso amyl alcohol in toluene and is stripped to aqueous phase using NaOH. Formation of the azido derivative depends on nitrite concentration and the system obeys Beer's law in the range 0-0.4 ppm of nitrite at 495 nm. The molar absorptivity of the colour system is 6.67 × 10⁴ L mol^-1 cm^-1 with a relative standard deviation of 3% for 10 determinations at 1 μg of nitrite. The proposed method is successfully applied for the determination of nitrite and nitrate in soil, water and radiator coolant sample, NO₂ gas in a laboratory fume cupboard is determined after fixing it as nitrite in sodium arsenite absorber solution.     

Interference of Humic Substances in the Spectrophotometric Determination of Bromate by Phenothiazines in Natural Waters

Abstract

The spectrophotometric method of bromate (BrO₃ ^?) determination by phenothiazines was applied to natural water samples and the interferences due to the presence of inorganic and humic substances were investigated. Common ions present in natural waters did not interfere and only the less abundant NO₂ ^? and Fe²⁺ exhibited strong interferences. Interferences of the two latter ions, if they existed, could be controlled and the method proved to be accurate and with a low detection limit. However, it was found that the presence of soluble humic substances resulted in positive interference, rendering the method unsuitable for bromate determination in natural waters and restricted its use in pure bromate solutions. This interference can be attributed to the electron acceptor groups invariably existing in the humic molecules. Since humic substances can remain in the water even after its ozonation, they will also contribute to a positive interference in bromate determination in potable waters.     

Determination of Nitrite by Single-Sweep Polarography

Abstract

A new method for determining nitrite is proposed. the mechanism for the polarographic waves and the condition for determining nitrite are discussed in this paper. In cathodic sweeps, the peak height is directly proportional to the concentration of nitrite over the range 5×10^?9?6×10^?7 g/ml, the detection limit is 4×10^?9g/ml. the experiments showed that this polarographic wave is an adsorption wave, and useful in determination of nitrite in water sample.     

INTERACTIONS OF COBALT(II) TETRASULFOPHTHALOCYANINE WITH NITRITE IN THE PRESENCE OF NITRATE AND PERCHLORATE IONS

Abstract

Spectroscopic changes observed on addition of nitrite to solutions of cobalt(II) tetra-sulfophthalocyanine ([Co(II)TSPc]^4-) in the presence of N^? ₃ or ClO^? ₄ are reported. There is spectroscopic evidence for the oxidation of [Co(II)TSPc]^4- to a [Co(III)TSPc]^3- species in the presence of nitrite ions. Equilibrium and kinetic studies for the interaction between [Co(II)TSPc]^4- and NO^? ₂ are reported. The rate was found to be first order in both [Co(II)TSPc]^4- and NO^? ₂. The rate constant for the forward reaction, k _f=1.6 × 10^?4 dm³mol^?1s^?1 was determined at 20°C for the interaction between nitrite ions and [Co(II)TSPc]^4- in the presence of NO₃ ^? or ClO₄ ^? ions.     

Use of A Novel Acetone-H2O2−C10− Chemiluminescence System for the Determination of Iodide Ion

Abstract

The present paper reports a new chemiluminescence system, i.e, acetone-H₂O₂?C10^?, which can be catalyzed by iodide ion (I^?). Based on this catalysis, a new chemiluminescence method for the determination of trace iodide ion is proposed. the optimum conditions are reported in this note. the detection limit is 2 × 10^?11 g/ml I^?, the linear dynamic range is 4 × 10^?10 g/ml to 3 × 10^?7 g/ml I^?, and the variation coefficient at an iodide concentration of 5 × 10^?9 g/ml I^? (n=10) is 4.6%. the method has been satisfactorily applied to the determination of trace iodide ion in water.     

Fluorescent sensing of nitrite at nanomolar level using functionalized mesoporous silica

Aminopyrene was covalently anchored onto mesoporous silica through serial post-grafting to obtain a fluorescent solid that can be used as a sensing material for the determination of nitrite. The latter, in acidic medium, reacts with the secondary amino groups on the material to form a non-fluorescent nitroso derivative. Based on the fluorescence quenching caused by this specific reaction, a method was developed for the determination of nitrite at nanomolar levels. The range for detection of nitrite in 1.5?mol.L^?1 HCl is linear between 1.50?nM to 0.45???M and 0.45???M to 2.22???M, the detection limit being 1.10?nM and 0.307???M respectively at an S/N of 3.

Aminophenyl Benzimidazole as a New Reagent for the Estimation of NO2/Nitrite/Nitrate at Trace Level: Application to Environmental Samples

Abstract

A simple and sensitive spectrophotometric method for the determination of nitrogen dioxide in ambient air and nitrite/nitrate in water and soil samples has been developed. Nitrogen dioxide in air has been fixed as nitrite ion using alkaline sodium arsenite as absorbing medium. The method is based on the reaction of nitrite with aminophenyl benzimidazole in acid medium to form diazonium ion, which is coupled with N‐(1‐naphthyl)ethylenediamine dihydrochloride to form an azo dye with an absorption maximum at 555 nm in aqueous phase. The method obeys Beer's law in the concentration range 0–10 µg of nitrite in 25 ml solution. The molar absorptivity has been found to be 6.3×10⁴ l mol^?1 cm^?1. The dye can be extracted quantitatively into isoamyl alcohol under alkaline condition and the addition of methanolic hydrochloric acid restores the original dye colour. Beer's law is obeyed in the concentration range 0–2 µg of nitrite with a detection limit of 0.009 µg. The effect of interfering species has been studied and the developed method has been applied to determine trace levels of nitrogen dioxide in ambient air and the results have been compared with the standard method. It is also applied to measure the nitrite/nitrate levels of surface and ground water samples collected from lakes, tube wells as well as soil samples.     

Determination of nitrite and nitrate in Venice lagoon water by ion interaction reversed-phase liquid chromatography

Ion interaction reversed-phase liquid chromatography with octylammonium orthophosphate as the interacting reagent and a reversed-phase C₁₈ column was applied to the identification and determination of nitrite and nitrate in Venice lagoon water. Interference by the high chloride concentration was systematically studied and the results obtained with different column packings were compared. With spectrophotometric detection at 230 nm, nitrite at 0.005 mg 1^?1 can be detected and determined even in the presence of 0.70 M chloride. The dependence of the retention time of nitrite on the chloride concentration was studied for two reversed-phase columns with different packings. Concentrations of 0.30 ± 0.05 mg 1^?1 of nitrite and 0.20 ± 0.05 mg 1^?1 of nitrate were found in Venice lagoon water.     

An Addition Method for the Direct Ultraviolet Spectrophotometric Determination of Nitrite in the Presence of a Large Excess of Nitrate

Abstract

The ultraviolet spectra of aqueous nitrite and nitrate solutions and of binary mixtures were obtained. By using an addition technique and a reference nitrate/nitrite solution it was possible to compensate for the interference caused by the overlapping of the nitrate and nitrite bands, which is normally a limiting factor in the analysis of mixtures of nitrite with large excesses of nitrate. The detection limit was 5 × 10^?5 M NO₂ ^? which corresponded to a minimum detectable amount of 2.3 ppm NO₂ ^? in the presence of up to 20,000 times greater amount of NO₃ ^?. The accuracy was ± 0.6% and the standard deviation ± 0. 002.