Bromate determination in water using chlorpromazine after correction of chlorinating agents and humic substances interference

The presence of soluble humic substances and chlorinating agents interfered positively with the spectrophotometric determination of bromate (BrO ₃ ⁻ ) using chlorpromazine. Removal of the soluble humic substances through their precipitation by a basic lead acetate (15.9 g/L Pb(CH₃COO)₂ · 3H₂O-4.7 g/L PbO) solution corrected their interference effectively. In addition, the use of NaHSO₃ at pH 5.1 ± 0.2 eliminated the interference of ClO ₂ ⁻ , Cl₂-OCl⁻, and Cl₂-NH₂Cl, when present in concentrations of up to 1.5, 3.5, and 3.5 mg/L, respectively. Thus, the spectrophometric method was rendered suitable for the direct bromate determination in natural, chlorinated, and ozonated waters, since the application to such samples resulted in the accurate and precise determination of bromate. The method’s detection limit was estimated as 1.6 μg BrO ₃ ⁻ /L and the linear range of the calibration curve was extended up to 700 μg BrO ₃ ⁻ /L. The method also gave results comparable to those obtained by the well-established ion chromatographic method and had the additional advantage of being simple, rapid, low cost, and suitable for brackish water. The text was submitted by the author in English.     

A Multicolumn Ion Chromatographic Determination of Nitrate and Sulfate in Waters Containing Humic Substances

Abstract

A three-column ion chromatographic system for the removal of humic substances from natural waters, and subsequent on-line concentration and determination of nitrate and sulfate using non-suppressed ion chromatography is presented. Humic substances are removed using disposable adsorption columns packed with chemically bonded amine silica material. The sample is directly transfered to an ion exchange column where the anions are concentrated ca 10 times. After reversing the flow, the ions are transferred to a third column where they are separated and quantified. The detection limit is less than 1 mg L^?1 of nitrate or sulfate in water containing 45mgL^?1 of humic acid.     

Determination of nitrate in natural waters by voltammetry at a stationary mercury drop electrode

Nitrate can be determined by second-sweep cyclic voltammetry at a stationary mercury drop electrode utilizing the autocatalytic effect of the hydroxyl ions formed at the surface of the electrode during the reduction of nitrate in the presence of an excess of trivalent cations. The reduction current in the second sweep with the same drop is proportional to the nitrate concentration in the range 1–1500 μmol l^?1 in natural waters. The humic substances present in natural waters have a favourable effect on the determination of nitrate. The method is applied to the determination of nitrate in drinking and river waters.     

Matrix Effects in Determination of Triazines and Atrazine Metabolite in Waters with Solid‐Phase Extraction Followed by High Performance Liquid Chromatography Coupled with Tandem Mass Spectrometry

Abstract

A method for determination of selected triazines in waters was developed. The method includes off‐line solid‐phase extraction of triazines on the polymeric sorbent, high‐pressure liquid chromatographic separation, and determination with tandem mass spectrometer. The linearity extended from 0.008 to 1.000 µg L^?1 for each triazine while the limits of detection ranged from 0.001 to 0.004 µg L^?1. Solid‐phase extraction recoveries from ground, surface, and waste waters ranged from 64% to 96%. Possible water interferences were investigated. Natural humic acids and salts did not influence the ionization process. The presence of humic acids did not affect binding ability of the solid‐phase sorbent, while the presence of salts increased the extraction efficiency by approximately 10%.     

Flotation separation and electrothermal atomic absorption spectrometric determination of lead in water samples

Abstract

The application of macro- and micro-electrodes constructed using the new ionophore were tested in a range of solution compositions reflecting concentrations found in fresh waters, and containing Cl^?, NO₃ ^?, SO₄ ^2-, HCO₃ ^2-, H₄SiO₄ and a natural humic acid. The inhibition of the electrode responses to these ions was quantified using a mixed-solution method by optimising the agreement between the measured potentials and predictions from the Nicolsky-Eisenman equation. In addition, measurements were made in separate solutions of KC1 to enable results to be compared with the literature. Apart from the results obtained for humic acid, mean selectivity coefficients for 16 macro- and 21 micro-electrode experiments are given. The results indicate inhibition of the electrode response to phosphate for all the anions in the concentration ranges of 0.05–1 mM Cl^?, 0.1–1.0 mM NO₃ ^?, 0.1–10.0 mM HCO₃ ^? and 0.1–1.5 mM SO₄ ^2- with high selectivity for HPO₄ ^2- in the presence of both dissolved silicon and a standard humic acid. This means that the application of the electrodes to hard waters is impracticable although studies of soft waters and laboratory studies in controlled conditions, e.g. calcium phosphate precipitation experiments, are feasible.     

Monitoring Humic Acid Photodegradation by CUPRAC Colorimetric and HPLC Determination of Dihydroxybenzoate Isomers Produced From a Salicylate Probe

Abstract

Novel analytical methods were designed for monitoring humic acid photodegradation in environmental waters. Modified CUPric Reducing Antioxidant Capacity (CUPRAC) spectrophotometric and chromatographic methods were used for the determination of dihydroxybenzoate isomers (DHBAs) produced from a salicylate probe, which was hydroxylated by hydroxyl radicals (^?OH) produced from the photodegradation of humic acid under ultraviolet A-radiation. The combined use of CUPRAC colorimetry and HPLC was shown to effectively monitor humic acid photodegradation and ^?OH generation for the first time. The formation of 2,5-dihydroxybenzoate and 2,3-dihydroxybenzoate, as major and minor products, respectively, from the hydroxylation of a salicylate probe was demonstrated by HPLC and confirmed by a modified CUPRAC method to indicate ^?OH formation from humic acid, which acted as both a generator and absorber of hydroxyl radicals. Salicylate hydroxylation showed an increase between 30 and 50?min of illumination, and was affected by the initial concentration of humic acid up to 0.01% but not by solution pH around the neutral values. Traces of Fe(III) and Mn(II) present in natural waters decreased the ^?OH production, but EDTA partly restored the probe hydroxylation by chelating these metal cations. Since humic acid-mediated ^?OH generation may aid in natural disinfection processes, this work may extend our comprehension of concentration- and time-dependent generation of ^?OH in environmental waters and of the possible effects of other antioxidants.     

Ultraselective and Sensitive Determination of Cr(VI) in the Presence of a High Excess of Cr(III) in Natural Waters with a Complicated Matrix

In the present work, the catalytic adsorptive stripping voltammetric procedure for trace determination of Cr(VI) in the presence of a high excess of Cr(III) in natural waters with a complicated matrix has been developed. The influence from potentially interfering substances such as organic matter was successfully eliminated by exploiting adsorptive properties of polymeric resin. The detection limit estimated from 3 times the standard deviation for a low Cr(VI) concentration in the simultaneous presence of a 2×10³ fold excess of Cr(III), 50 mg L^?1 surfactants, 50 mg L^?1 humic substances and the accumulation time of 30 s was about 5.3×10^?10 mol L^?1.     

Simultaneous spectrophotometric determination of humic acid and iron in water

A simple and rapid method for the determination of humic acid and iron in solution is described. Two absorbance measurements are required, one on an untreated sample aliquot, and the other on an aliquot treated to enhance iron absorptivity. The method requires sample volumes of less than 15 ml and is sensitive enough for direct application to most natural waters. Limits of detection for each component vary with concentration of the other, but 0.01 mg 1^?1 for humic acid and 0.04 μM for iron can be achieved. For six natural waters, determinations based on independent calibration curves for each component gave results 6–40$ higher for iron, and 6–29% higher for humic acid, than results obtained by the proposed method. The interference of fulvic acid and the use of different humic acid standards are examined.     

Effect of Cobalt(II) and Manganese(II) on the Chemiluminescent Reaction of Peroxymonosulfate with Humic Acid and Some Organic Compounds. Analytical Applications

Abstract

The intensity of the radiation emitted by humic acid (HA) in the presence of SO₅ ^2? in basic medium was used to determine HA in the range up to 20.0 mg l^?1. The detection limit was 0.24 mg l^?1. The addition to the sample of 50 mg l^?1 of Co(II) or Mn(II), as EDTA complexes or chloride salts, enhanced the radiation emission as a result of the formation of strong oxidant radicals such as SO₅ ^??, SO₄ ^??, and HO^?. In the presence of these metal ions, the oxidation of HA and the catalytic decomposition of SO₅ ^2? occur simultaneously. Low concentration of HA in natural waters can be detected. HA was replaced by some model organic compounds. The marked chemiluminescent (CL) signals followed the order: phloroglucinol>fulvic acid>humic acid>resorcinol>pyrogallol>cathecol>hydroquinone.     

Flow Injection Determination of Humic Acid with Chemiluminescence Detection

Abstract

A very sensitive and fast flow injection chemiluminescence method, based on the oxidation of humic acid (HA) by 1,3‐dibromine‐5,5‐dimethylhydantion in the presence of glycine in alkaline medium, was developed for the determination of trace humic acids in water. A wide calibration range from 0.001 to 1.0 µg mL^?1 was obtained at the optimized conditions and the detection limit was as low as 0.5 ng mL^?1 of humic acids. Most of the foreign substances tested showed relatively high tolerance levels and the proposed method was successfully applied to the determination of humic acid in river water and tap water.     

Rubidium Determination In Mineral and Thermal Waters By Atomic-Absorption Spectrometry

Abstract

A new procedure for rubidium determination in mineral and thermal waters using flame atomic-absorption spectrometry is described. to supress ionisation interference potassium solution was added. Rubidium can be determined in presence of Ca, Mg, Sr, Li, Cs, Fe, Al, CO² ₃, F^? and S^2? at higher levels that levels of these elements in waters. the precision and accuracy of the method were also investigated. In 163 mineral and thermal waters analysed, the rubidium concentration range is between 0.08 to 0.84 μg mL^?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.     

Flow-injection spectrophotometric determination of aluminium in water with pyrocatechol violet

Optimum conditions for the adaptation of the spectrophotometric pyrocatechol violet method for aluminium to a flow-injection system are described. The detection limit is 3 μg Al l^?1 and calibration graphs are linear up to 3 or 10 mg l^?1 (with 200-μl or 10-μl injection loops, respectively). The relative standard deviation is 〈 2% at 0.1 mg Al l^?1. Potential interferences of 40 common inorganic ions and of 20 organic substances, including fulvic acid, are reported. With the use of conventional masking agents and predigestion of samples with high organic content, the method is suitable for determining total aluminium in natural waters.     

Spectrophotometric determination of trace-level bromate in drinking water after post-column reaction with pararosaniline based on multi-walled carbon nanotubes

A simple and sensitive spectrophotometric method is described for low level determinationof bromate in drinking water. This method is based on the reduction of bromate ions into bromine in the presence of pararosaniline by sodium metabisulphite to form a highly stable pink-red complex measured at 540 nm. Maximum colour formation was obtained at about 45 min. Multi-walled carbon nanotubes, a solid phase extraction sorbent, has been described for the removal of cationic interferences of major elements and heavy metals from water samples prior to conducting the assay. Bear’s law is obeyed in the range of 5–80 µg.L^?1 with limit of detection of 0.44 µg.L^?1 and correlation coefficient of 0.998 (n = 5). The mean relative standard deviation (RSD%) of the results within-day precision and accuracy were ≤1.2% which confirmed the reproducibility of the assay technique. The optimum assay conditions and their applicability to the determination of water samples are described. The method was successfully applied for the determination of bromate in water samples with satisfactory results and recommended to be applied in all desalination plant samples.     

Flow Injection Catalytic Determination of Vanadium using the Indicator Reaction between Victoria Blue B and Bromate and A Citric Acid Activator

ABSTRACT

A flow injection catalytic method is proposed for determination of trace vanadium based on its catalytic action on a new indicator reaction between Victoria blue B (VBB) and potassium bromate in the presence of citric acid as an activator and in dilute sulfuric acid medium. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of VBB injected at the maximum absorption wavelength of 618 nm. The detection limit is 0.5 ng ml^?1 and is independent of the initial valence state of vanadium. The relative standard deviation is 1.5% obtained from 11 standard solutions each containing 40 ng ml^?1 of vanadium. The sampling rate is about 15 samples per hour. This method is very simple and has been applied to the determination of trace vanadium in some natural waters with recoveries of 93-103%.     

Effect of Organic Substances on the Results of Anodic Stripping Voltammetry Detection of Metal Ions in Aqueous Media

Abstract

The d.c. anodic stripping voltammetry method has been used to investigate the effect of organic substances simulating the composition of natural waters on the results of determination of concentration levels of copper, lead and cadmium. The response, sensitivity and concentration (the latter determined by the standard additions method) have been used as sources of information. In the presence of enzymes, fulvic acids, humic acids and polyethylene glycol all these three parameters change in the case of determination of copper and lead, making the results unreliable. The determination of cadmium concentration is not hampered by the said organic substances.     

Cyclopentane-1,3-dione Bis (4-Methylthiosemicarbazone) Monohydrochloride as a Spectrophotometric Reagent for the Determination of Bromate in Perchloric Acid Medium

Abstract

Cyclopentane-1,3-dione bis (4-methylthiosemicarbazone) monohydrochloride produces coloured solutions with bromate ions in perchloric acid medium. The yellow colour obtained (molar absorptivity 1.8×10⁴ 1.mol^?1.cm^?1 at a wavelength of 400 mm) has been used for the spectrophotometric determination of trace amounts of bromate.     

Determination of Cr(VI) in the Presence of Complexing Agents and Humic Substances by Catalytic Stripping Voltammetry

The voltammetric method of Cr(VI) determination in a flow system is proposed. Determinations can be carried out in the simultaneous presence of an excess of Cr(III), complexing agents, humic substances and surfactants. The method is based on the combination of a selective accumulation of the product of Cr(VI) reduction to the metallic state and a very sensitive voltammetric method of chromium determination in the presence of DTPA and nitrates. The calibration graph is linear from 1×10^?9 to 5×10^?8 mol L^?1 for accumulation time of 30 s. The relative standard deviation is 5.2% (n=5) for Cr(VI) concentration 1×10^?8 mol L^?1. The influence of humic and fulvic acids, complexing agents and surfactants on Cr(VI) and the interfering Cr(III) signal is presented. The method was applied to Cr(VI) determination in certified reference material, soil sample, natural water sample and EDTA extracts from soil certified reference material.     

A Novel Room Temperature Ionic Liquid Extraction Spectrophotometric Determination of Trace Germanium in Natural Water with Methybenzeneazosalicylfluorone

Abstract

This paper describes a highly sensitive and selective extraction spectrophotometric method for determination of trace germanium in natural water with new a chromogenic reagent methybenzeneazosalicylfluorone abbreviated as MBASF, in which a typical room temperature ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate abbreviated as [C₄mim][PF₆] was used as novel medium for liquid/liquid extraction of germanium(IV). In the presence of TritonX‐100, MBASF reacted with germanium(IV) to form a red complex rapidly, the complex was then extracted into the [C₄mim][PF₆] phase, the absorbance of the complex in ionic liquid at 496 nm was recorded and used to determine trace germanium(IV). The apparent molar absorptivity of the complex and the detection limit for the real sample were found to be 3.12×10⁶ L mol^?1 cm^?1 and 0.2 ng mL^?1, respectively. The absorbance of the complex at 496 nm increases linearly with the concentration up to 4 µg of germanium (IV) in 250 mL of aqueous solution. The interference study show the determination of germanium is free from the interference of almost all positive and negative ions found in the natural water samples. The determination of germanium in natural water was carried out by the present method and electrothermal atomic absorption spectrometry (AAS). The results were satisfactorily comparable so that the applicability of the proposed method was confirmed using the real samples. Moreover, the extraction mechanism with the ionic liquid system was also investigated. We think the extraction performance of the ionic liquid system is a combination of ion‐pairing effect between imidazolium cation and basic solute in the aqueous phase with the dissolution of polar molecule in ionic liquid phase. A wise choice of the appropriate combination of anion with imidazolium cation hydrophobicity allows playing with solute selectivity.     

Spectrophotometric determination of traces of bromide based on its catalysis of the pyrocatechol violet/hydrogen peroxide reaction

A kinetic-spectrophotometric method for the determination of bromide (0.004–0.3 mg l^?1) based on its catalysis of the oxidation of pyrocatechol violet by hydrogen peroxide in HCl/H₂SO₄ is described. The effect of bromide is greatly increased in the presence of large amounts of chloride. The relative standard deviations are 6.4 and 13% for 0.034 and 0.010 mg l^?1 bromide, respectively (n = 10). Most ions commonly occurring in natural waters do not interfere except for iodide.