New Potentiometric Sensor for the Determination of Bromate Ion in Drinking Water

The characteristics, performance and application of ion‐selective electrodes for bromate ion based on rhodamine B and tetrahexyl ammonium bromide as electrode‐active substances are described for the first time. These electrodes respond with sensitivities of (58.0±1.0) and (61.0±2.0) mV decade^?1 over the range 1.0×10^?8–1.0×10^?2 mol l^?1 at pH 4–9 and 4–8 and a detection limit of 6.0×10^?8 and 4.0×10^?8 mol l^?1 for rhodamine B and tetrahexyl ammonium bromide sensors, respectively. The electrodes are easily constructed at a relatively low cost, have a fast response time and can be used for a period of 3 months without any considerable divergence in potential. The proposed sensors displayed good selectivity for bromate ion in the presence of several substances and inorganic anions. Sensors were used for the direct assay of bromate ion in drinking water samples.     

Synthesis,characterization, and electrocatalysis of a dinuclear cobalt(III) thioxanthate complex

This study reports on the synthesis, characterization, and performance of a new dinuclear cobalt(III) thioxanthate complex of [Co₂(μ-SC₂H₄OH)₂(HOC₂H₄SCS₂)₄] as an electrocatalyst for trichloroacetic acid (TCA) and bromate reduction. Its structure was characterized by X-ray crystallography and elemental analysis. The structure contains two different anions of 2-sulfanylethanol thioxanthate and 2-sulfanylethanol. The electrochemical behavior and the electrocatalysis of the cobalt complex bulk-modified carbon paste electrode have been studied by cyclic voltammetry. It shows good electrocatalytic activities toward the reduction of TCA and bromate. The values for the detection limit and the sensitivity are 0.06 µmol L^?1 and 19.40 µA µmol L^?1 for TCA detection and 0.01 µmol L^?1 and 177.6 µA µmol L^?1 for bromate detection, respectively. This modified electrode exhibits good reproducibility, high stability, low detection limit and technical simplicity, and allows a possibility for rapid preparation, which is important for practical applications.     

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.     

Catalytic Adsorptive Stripping Voltammetry of Molybdenum: Redox Kinetic Measurements

The electrode mechanism of Mo(VI) reduction was studied under catalytic adsorptive stripping mode by means of square‐wave voltammetry (SWV). Mo(VI) creates a stable surface active complex with mandelic acid. The electrode reaction of Mo(VI)‐mandelic acid system undergoes as one‐electron reduction, exhibiting properties of a surface electrode process. In the presence of chlorate, bromate, and hydrogen peroxide, the electrode reaction is transposed into a catalytic mechanism. The experimental results are compared with the recent theory for surface catalytic reaction, enabling qualitative characterization of the electrode mechanism in the presence of different catalytic agents. Utilizing both the method of “split SW peaks” and “quasireversible maximum” the standard redox rate constant of Mo(VI)‐mandelic acid system was estimates as k_s=150±5 s^?1. By fitting the experimental and theoretical results, the following catalytic rate constants have been estimated: (8.0±0.5)×10⁴ mol^?1 dm³ s^?1, (1.0±0.1)×10⁵ mol^?1 dm³ s^?1, and (3.2±0.1)×10⁶ mol^?1 dm³ s^?1, for hydrogen peroxide, chlorate, and bromate, respectively.     

Preparation and application of trimethylamine amination polychloromethyl styrene nanolatex coated capillary column for the determination of bromate by field‐amplified sample stacking open‐tubular capillary electrochromatography

A new trimethylamine amination polychloromethyl styrene nanolatex (TMAPL) and TMAPL coated capillary column (ccc‐TMAPL) were successfully prepared. The TMAPL coating was characterized with reversed steady EOF values of ca. ?16.8 × 10^?5 cm² V^?1 s^?1. It was applied to establish open‐tubular (OT) CEC and field‐amplified sample stacking (FASS) OT‐CEC methods for the determination of bromate in tap water. Compared to OT‐CEC, the LOD with FASS‐OT‐CEC was improved from 80 to 8 ng/mL. The developed FASS‐OT‐CEC method was practically used for the analysis of bromate in tap water samples with recoveries ranging from 93.6 to 103.5%.     

Solubility studies in formamide: III. Solubility product of silver bromate and standard electrode potential of silver—silver bromate electrode in formamide

The solubility and solubility product of silver bromate in formamide in sodium perchlorate solutions have been determined at 25, 30 and 35°C. At these temperatures, the solubilities in pure formamide are found to be 1.837 × 10^?2, 1.967 × 10^?2, and 2.092 × 10^?2 moll^?1, respectively, and the corresponding solubility products are 3.375 × 10^?4, 3.869 × 10^?4, and 4.377 × 10^?4 mol² l^?2. The standard potentials of the Ag(s)/AgBrO₃(s)/BrO^?₃ electrode have been calculated and found to be 0.4997, 0.4948, and 0.4892 V, at 25, 30, and 35°C, respectively. The mean activity coefficients of silver bromate at various rounded molarities of sodium perchlorate solutions, and the standard thermodynamic quantities for the process AgBrO₃(s) → Ag⁺(solvated) + BrO^?₃(solvated) have been calculated at these three temperatures and compared with those for the process AgIO₃(s) → Ag⁺(solvated) + IO^?₃(solvated) in formamide.     

Determination of Molybdenum(VI) At Trace Levels by a Catalytic Polarographic Method

Abstract

ARSTRACT

A d.c. polarography method for molybdenum (VI) determination at trace levels has been developed. The reaction is catalytic between molybdenum, salicylaldoxime (SCAD) and bromate in acetic-acetate medium. The obtained peak is proportional to molybdenum (VI) concentrations in the range 1.08.10^?a to 1.37.10^?6 M. The proposed procedure is selective, the most serious interferents being W(VI), Pb(II) and Fe(II). It is applied to molybdenum determination in steel samples after iron extraction by ethyl ether.     

Cetyltrimethylammonium-coated magnetic nanoparticles for the extraction of bromate,followed by its spectrophotometric determination

We report on a combination of magnetic solid-phase extraction and spectrophotometric determination of bromate. Cetyltrimethylammonium ion was adsorbed on the surface of phenyl-functionalized silica-coated Fe₃O₄ nanoparticles (Ph-SiO₂@Fe₃O₄), and these materials served as the sorbent. The effects of surfactant and amount of sorbent, the composition of the desorption solution, the extraction time and temperature were optimized. Under optimized conditions, an enrichment factor of 12 was achieved, and the relative standard deviation is 2.9 % (for n?=?5). The calibration plot covers the 1–50 ng mL^?1 range with reasonable linearity (r ²?>?0.998); and the limit of detection is 0.5 ng mL^?1. The method is not interfered by ionic compounds commonly found in environmental water samples. It was successfully applied to the determination of bromate in spiked water samples.

Kinetics and simulations of reaction between safranine‐O and acidic bromate and role of bromide therein

Safranine‐O, a dye of the phenazinium class, was found to exhibit intricate kinetics during its reaction with bromate at low pH conditions. Under conditions of excess concentrations of acid and bromate, safranine‐O (SA⁺) initially depleted very slowly (k = (3.9 ± 0.3) × 10^?4 M^?3 s^?1) but after an induction time, the reaction occurred swiftly. Bromide exhibited a dual role in the reaction mechanism, both as an autocatalyst and as an inhibitor. The added bromide increased the initial rate of depletion of SA⁺, but delayed the transition to rapid reaction. The overall stiochiometric reaction was found to be 6SA⁺ + 4 BrO₃ ^? = 6SP + 3N₂O + 3H₂O + 6H⁺ + 4Br^?, where SP is 3‐amino‐7‐oxo‐2,8‐dimethyl‐5‐phenylphenazine. The fast kinetics of the reaction between aqueous bromine and safranine‐O (k = (2.2 ± 0.1) × 10³ M^?1 s^?1) are also reported in this paper A 17‐step mechanism, consistent with the overall reaction dynamics and supported by simulations, is proposed and the role of various bromo and oxybromo species is also discussed. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 542–549, 2002     

Spectrophotometric Determination of Bromate in Water Using Multisyringe Flow Injection Analysis

A multisyringe flow injection system for the spectrophotometric determination of bromate in water is proposed, based on the oxidation of phenothiazine compounds by bromate in acidic medium. Several phenothiazines were tested, including chlorpromazine, trifluoperazine, and thioridazine. Higher sensitivity and lower LOD were attained for chlorpromazine. Interference from nitrite, hypochlorite, and chlorite was eliminated in-line, without any changes in the manifold. The automatic methodology using chlorpromazine allowed the determination of bromate between 25 and 750 µg L^?1, with LOD of 6 µg L^?1, good precision (RSD < 1.6%, n = 10), and determination frequency of 35 h^?1.     

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.     

Stacking in CE for Analysis of Bromate Flour Additive

In this paper we report a simple and effective on-line sample-stacking method in capillary electrophoresis for analysis of bromate ion. The detection limit is 10.9 ng mL^?1. Direct injection is performed after a simple extraction procedure. It is possible to detect 2.18 mg kg^?1 bromate ion in flour by use of this technique.     

Flow-Injection Determination of Iron Based on Its Catalysis on the Oxidation Reaction of Xylenol Orange by Potassium Bromate

A flow injection system is proposed for catalytic kinetic spectrophotometric determination of trace iron(II + III). The involved reaction is based on the catalytic effect of iron(III) on oxidation reaction of xylenol orange by potassium bromate to form a blue-violet complex. Iron(II) is also determined, being oxidized to iron(III) by potassium bromate. The calibration graph is linear in the range of 0.02–10.0 µg l^?1 and 10.0–1100 µg l^?1. The relative standard deviation is 1.5% for 4.0 µg l^?1 iron(III) and 2.3% for 60.0µg l^?1 iron(III) (n = 11). The presented system was applied successfully to the determination of iron in natural waters.     

Kinetic Study of the Reduction of Bromate Ion by Tris(1,10-Phenanthroline)Iron(II) and Aquoiron(II) Ions — Implication for the Bromate-Gallic Acid Oscillating Reaction

The kinetics of the bromate oxidation of tris(1,10-phenanthroline)iron(II) (Fe(phen)₃²⁺) and aquoiron(II) (Fe²⁺ (aq)) have been studied in aqueous sulfuric acid solutions at μ = 1.0M and with Fe(II) complexes in great excess. The rate laws for both reactions generally can be described as -d [Fe(II)]/6dt = d[Br^?]/dt = k[Fe(II)] [BrO^?₃] for [H⁺]₀ = 0.428–1.00M. For [BrO^?₃]₀ = 1.00 × 10^?4M. [Fe²⁺]₀ = (0.724–1.45)x 10^?2 M, and [H⁺]₀ = 1.00M, k = 3.34 ± 0.37 M^?1s^?1 at 25°. For [BrO^?₃]₀ = (1.00–1.50) × 10^?4M, [Fe²⁺]₀ = 7.24 × 10^?3M ([phen]₀ = 0.0353M), and [H⁺]₀ = 1.00M, k = (4.40 ± 0.16) × 10^?2 M^?1s^?1 at 25°. Kinetic results suggest that the BrO^?₃-Fe²⁺ reaction proceeds by an inner-sphere mechanism while the BrO^?₃-Fe(phen)₃²⁺ reaction by a dissociative mechanism. The implication of these results for the bromate-gallic acid and other bromate oscillators is also presented.     

Determination of nitrite in environmental waters by flow injection catalytic spectrophotometry

ABSTRACT

The flow injection catalytic spectrophotometry is proposed for the determination of nitrite based on the catalytic effect on the redox reaction between methylene blue and potassium bromate in acidic medium. The reaction is monitored spectrophotometrically by measuring the decrease in the absorbance of methylene blue at the maximum absorption wavelength of 664 nm. The method is characterised by low solvent consumption and easy automatic continuous analysis. It has higher sensitivity and lower detection limit. Experimental analysis conditions of the flow injection-catalytic photometry are optimised, and the best analysis conditions are: the concentration of the potassium bromate is 0.068 mol L^?1; the concentration of the phosphoric acid in oxidation liquid is 0.045 mol L^?1; the concentration of the methylene blue in colour-substrate solution is 2.4 mg L^?1, the volume of sample ring is 200 μL; the reaction coil is around 7 m in length; the inject time is 50 s and analysis time is 70 s. Under the optimal conditions, the linear range is from 10 to 500 μg L^?1 and the detection limit is 1 μg L^?1. The nitrate standard solution is continuously determined with a mass concentration of 300 μg L^?1. The RSD is determined to be 1.41% (n = 10). The nitrite in water samples, which were from the Half Acre pond, the Ink River and the Small West lake in a campus, was determined respectively by this method. A satisfactory standard addition recovery of 96.7%–103.9% was obtained.     

Determination of bromate via the chemiluminescence generated in the sulfite and carbon quantum dot system

The authors describe a chemiluminescence (CL)-based assay for the determination of bromate. The method is based on the use of a solution of carbon quantum dots (CQDs) and sulfite. Strong CL (peak at 490 nm) is observed when bromate is injected into the solution. The CL increases linearly in the 0.3 to 10 μmol L^?1 bromate concentration range, giving a 0.1 μmol L^?1 limit of detection (at an S/N ratio of 3). A possible CL mechanism is suggested that involves a redox reaction between the CQDs, bromate and sulfite in the acidic medium. This leads to the formation of hole-injected and electron-injected CQDs. Radiative recombination of oxidant-injected holes and electrons in the CQDs accounts for the occurrence of CL. This mechanism contradicts the previous assumption that the transfer of energy occurs from SO₂* to the CQDs. Although nitrite may interfere in the determination of bromate, its effect can be eliminated by adding sulfamic acid. The assay is sensitive and represents a new tool for the determination of bromate, which is a carcinogen.

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Graphical abstract Under acidic condition, carbon quantum dots (CQDs) can react with sulfite and bromate transforming to hole-injected CQDs (CQDs^?–) and electron-injected CQDs (CQDs^?+), respectively. Thereafter, strong chemiluminescence (490 nm) aroused from the radiative electron-hole annihilation between CQDs^?– and CQDs^?+.

     

Two new metal-organic frameworks possessing binodal high-connected topologies based on Cd4-clusters and organic ligands

Two new compounds, [Cd₂(bptc)(bpimb)(H₂O)]?·?2H₂O (1) and [Cd₂(bptc)(bpib)]?·?4H₂O (2) (where H₄bptc?=?biphenyl-3,3′,4,4′-tetracarboxylic acid, bpimb?=?1,3-bis((2-(pyridin-2-yl)-1H-imidazol-1-yl)methyl)benzene, bpib?=?1,4-bis(2-(pyridin-2-yl)-1H-imidazol-1-yl)butane), were synthesized by reactions of the corresponding metal salts with H₄bptc and N-containing auxiliary ligands and their structures have been determined by single-crystal X-ray diffraction. Compound 1 is built by Cd₄-clusters which further construct a 3-D (3,8)-connected framework with tfz-d notation; 2, also built by Cd₄-clusters, is a 3-D (4,8)-connected framework with (3²?·?4²?·?5²)(3⁴?·?4⁸?·?5¹²?·?6⁴) topology. In addition, the elemental analyses, infrared spectra, fluorescence, and thermogravimetric analyses for 1 and 2 are discussed.     

Silicomolybdate‐Incorporated‐Glutaraldehyde‐Cross‐Linked Poly‐L‐Lysine Film Modified Glassy Carbon Electrode as Amperometric Sensor for Bromate Determination

Silicomolybdate‐doped‐glutaraldehyde‐cross‐linked poly‐L ‐lysine (PLL‐GA‐SiMo) film modified glassy carbon electrode was successfully prepared by means of electrostatically trapping the silicomolybdate anion in PLL‐GA cationic coating. The PLL‐GA‐SiMo film was stable and the charge transport through the film was fast. The modified electrode shows excellent electrocatalytic activity towards bromate reduction with significant reduction of overpotential. In amperometric determination of bromate, the calibration plot was linear over the concentration range of 5×10^?5 to 1.2×10^?3 M with a sensitivity of 3.6 μA mM^?1. Furthermore, PLL‐GA‐SiMo film electrode showed fast response and good stability.     

Bromate formation during oxidation of bromide-containing water by the CuO catalyzed peroxymonosulfate process

Bromate formation has been found in the SO₄^??-based oxidation processes, but previous studies primarily focused on the bromate formation in the homogeneous SO₄^??-based oxidation processes. The kinetics and mechanisms of bromate formation are poorly understood in the heterogeneous SO₄^??-based oxidation processes, although which have been widely studied in the eliminations of micropollutants. In this work, we found that the presence of CuO, a common heterogeneous catalyst of peroxymonosulfate (PMS), appreciably enhanced the bromate formation from the oxidation of bromide by PMS. The conversion ratio of bromide to bromate achieved over 85% within 10 min in this process. CuO was demonstrated to play a multiple role in the bromate formation: (1) catalyzed PMS to generate SO₄^??, which then oxidizes bromide to bromate; (2) catalyzed the formed free bromine to disproportionate to bromate; (3) catalyzed the formed free bromine to decomposed back into bromide. In the CuO-PMS-Br system, bromate formation increases with increasing CuO dosages, initial CuO and bromide concentrations, but decreases with increasing bicarbonate concentrations. The presence of NOM (natural organic matter) resulted in a lower formed bromate accompanied with organic bromine formation. Notably, CuO catalyzes PMS to transform more than 70% of initial bromide to bromate even after recycled used for six times. The formation of bromate in the PMS catalysis by CuO system was also confirmed in real water.     

A Fluorescence Quenching Method for the Determination of Bromate Ion with 4,5-Dibromophenylfluorone and Cetyltrimethylammonium Bromide

Abstract

A highly sensitive and selective fluorescence quenching method was developed to determine the bromate ion (BrO₃ ^?) with 4,5-dibromophenylfluorone (DB-PF) as fluorogenic reagent. BrO₃ ^? reacts with potassium bromide in sulfuric acid solution (0.6M) giving bromine (Br₂) which is estimated with fluorescence quenching method using DB-PF as fluorogenic reagent. Bromine reacts with DB-PF to produce a compound, whose maximum excitation wavelength and emission wavelength are 543nm, 560nm respectively. The linear calibration range is 0.05–0.5 μg/25ml. The detection limit is 0.05μg/25ml. The method may be used to determine microamounts of BrO₃ ^? in potassium chlorate with satisfactory results. The method offers the advantages of simplicity, rapidity and sensitivity.