Iodide In Acidic Medium Research Articles

Indirect spectrophotometric determination of aqueous ferrate(VI) based on its reaction with iodide in acidic media

Ferrate(VI) (Fe(VI)) is utilized as an efficient and environmentally friendly water treatment agent that can be widely used for degradation of (in)organic pollutants in practical applications. However, only a few spectrophotometric methods for Fe(VI) determination were reported. In this study, a novel method for determining trace levels of aqueous Fe(VI) was developed based on the fact that Fe(VI) reacts with iodide at acidic pH to form iodine, which subsequently is treated with starch to yield the blue starch-iodine complex measured spectrophotometrically at 590 nm. The key measurement parameters, including acidic medium, starch dosages, temperature, time, and addition order were optimized to improve the sensitivity of detection. The increase in absorbance at 590 nm was linear with respect to Fe(VI) added (0.022–50 µM). Its sensitivity was determined as (4.61 ± 0.05) × 104 M−1 cm−1, which was higher than that of existing spectrophotometric methods. The principle for Fe(VI) determination was studied by investigating stoichiometry, kinetics, and mechanism of Fe(VI) reaction with iodide. The molar stoichiometry of Fe(VI) with I3− species was determined to be 1:2. The reaction of Fe(VI) with iodide followed a second-order rate law with first order in each reactant and displayed apparent anti-Arrhenius kinetics, then its reaction pathway was proposed as well. Furthermore, the established method was successfully applied to measure Fe(VI) in various environmental water samples. The results show that the proposed approach is simple, convenient, highly reproducible and extremely sensitive, and is also expected to be of use for kinetic studies of Fe(VI) reaction with (in)organic compounds under acidic conditions.

Flow Injection Amperometric System Coupled with a Well-Plate for Fast Screening of Total Antioxidant Capacity

ABSTRACTA flow injection (FI) system with an amperometric detection in combination with a 96-well-plate has been developed for high throughput screening of total antioxidant capacity. It is based on the reaction between dichromate and antioxidants Chromium reducing antioxidant capacity (CHROMAC) assay. Antioxidant reduces dichromate leading to a decrease of dichromate concentration, in which reacts further with triiodide reagent. The slow reaction between antioxidant and dichromate takes place in parallel in a 96-well microplate, with the reaction time sufficiently long to reach steady state conditions. Microliter volumes of the remaining dichromate solution were manually injected into the FI amperometric system. Reaction with iodide in acidic medium produces triiodide which undergoes electrochemical reduction on a glassy carbon working electrode at 200 mV versus a Ag/AgCl reference electrode. The decrease of electrical current was directly proportional to the antioxidant capacity. The optimum conditions have been achieved as follow: 160 mg L−1 of potassium dichromate, pH of dichromate solution of 2.82, 0.005 mol L−1 of potassium iodide, 0.20 mol L−1 of hydrochloric acid, and 3.0 mL min−1 total flow rate. The developed method was applied for the determination of total antioxidant capacity of tea and herbal infusions and fruit juice samples. The results obtained indicated that the developed method had good correlation with the batch CHROMAC spectrophotometric method and 1,1-diphenyl-2-picrylhydrazyl scavenging assay. The proposed method provides fast and high throughput analysis, convenient operation, and low consumption of chemical reagents and samples.

An optical sensor for selenite determination in aqueous samples

BackgroundIn the present work, an optical sensor has been developed for the determination of selenium (IV) in aqueous samples. The optical sensor is a cellulose triacetate plasticized membrane with tri-octyl methyl ammonium chloride (Al-336) immobilized in it as an ion exchanger.MethodsThe sensor works in two steps. In the first step, a 1 × 2 cm piece of the membrane is allowed to equilibrate with a known amount of selenium (IV) solution and potassium iodide in acidic medium. During this equilibration, the iodometric reaction takes place and, I3− (tri-iodide anion) is formed which gets sorbed into the membrane due to which the colorless film changes to yellow color showing an absorption maxima at 355 nm which is a characteristic of I3−. In the second step the I3− loaded membrane is allowed to equilibrate with a solution of variamine blue dye in presence of sodium acetate. In this step, oxidation of the dye takes place and the membrane shows a color change from yellow to violet and a shift in the absorption maxima from 355 to 550 nm.ResultsThe method is used to study the quantitative determination of selenium in aqueous samples, where the amount of selenium is varied and the corresponding absorbance at 550 nm is measured. A good linear curve is obtained in the concentration range of 0.2 to 3 μg mL−1 of selenium.ConclusionsThe proposed method can be successfully applied to determination of selenium (IV) in various pharmaceutical and environmental samples.

Determination of trace amounts of palladium by solution scanometric method

In this study, solution scanometry is presented as a highly sensitive, simple and rapid method for the colorimetric determination of palladium ion in water samples and walnut leaf. The method is based on the formation of a rose-brown complex between Pd2+ ion and an excess of iodide in acidic medium in Plexiglas cells, which are scanned by conventional flatbed-scanner, and the colour of each cell is analysed by software written in Visual Basic (VB 6) media to determine red, green and blue values. The relative standard deviation and linear range of the method were determined to be 1.0% and 0.1–72.0μgmL−1, respectively. The proposed method was successfully applied for the determination of Pd2+ ion in water samples and walnut leaf.

Spectrophotometric Determination of Selenium Through Triiodide Anion.

Selenium is a chemical element found in the human body that plays a crucial role in its regulation. Depending on the concentration, it may have beneficial or have toxic effects. Selenium is incorporated as selenocysteine amino acid residue in selenoproteins which play an important role in many biological functions: anti-oxidant defense, regulation of the immune function and of the inflammatory response, metabolism of thyroid hormones, functioning of the central nervous system, biosynthesis of DNA and RNA, fertility, and reproduction. Excess selenium, altough less common than selenium deficiency, has equally important negative effects. Given the importance of selenium quantification in various samples, the study proposes a simple and direct spectrophotometric determination of selenium using triiodide anions. The method is based on the oxidation of iodide in acidic medium by selenium (IV) contained in the sample, to form elemental iodine which, in turn, reacts with the excess iodide to form the triiodide anions, the most stable soluble species in aqueous solution. Triiodide is colored from yellow to brown, depending on the concentration. The coloured compound has maximum absorbance at specific wavelengths and thus, the stage of interaction with a chromogenic agent is eliminated. Due to the sensitivity of the reaction, the detection limit of triiodide, and therefore selenium, is extended toward lower values. The optimal conditions for the measurements were established: λ = 290 nm, pH = 1.0 - 1.5, reaction time = 15 minutes. Two areas of selenium detection were determined from the samples: 0.025 - 0.100 ppm, and 0.1 - 4.0 ppm. The detection limit of selenium was lowered at 0.100 ppm and even at 0.025 ppm, which significantly improves the sensitivity of the determination. Types of samples were specified which are suitable for analysis using the proposed method and explained why, in case of biological fluids, it must be used only accompanied by an adequate digestion method of the samples. Selenium can be measured by direct spectrophotometric determination of the triiodide anion resulting from the oxidation of iodide by selenium (IV) compounds from the sample. In this regard, a simple, direct, and sensitive determination method of selenium from the samples by UV-Vis spectrophotometry, without the use of chromogenic agents has been optimized.

Determination of iodate ion in the presence of hydrogen peroxide with the stopped-flow technique

The modified titration of iodate and hydrogen peroxide with iodide in acidic medium was investigated in order to study the possibility of separation and determination of iodate under certain conditions. The stopped-flow technique was used to kinetically distinguish titration products $${\text{I}}_{ 2}$$ and $${\text{I}}_{3}^{ - }$$ formed in both reactions. Under the given conditions, the reaction between iodate and iodide is finished considerably faster than the reaction between peroxide and iodide. For the ratio [KIO3]/[H2O2] ≈ 0.08 and acidity of [H2SO4] = 1.005 × 10−1 M, the kinetic separation between both components may be achieved to within 0.3 %, in less than 3 s. The recovery value of the iodate, with the applied technique after completion of the reaction, is ≈98 % showing appropriately chosen reaction conditions. Our results show that when iodate–iodide and peroxide–iodide reactions occur simultaneously under certain conditions, the contribution of peroxide–iodide products may be neglected. It was shown that stopped-flow titration of iodate in specific reactions and certain iodate/peroxide ratio may be used for determination of iodate concentration within a few percent.

Development of surfactant assisted kinetic method for trace determination of thallium in environmental samples

A simple and highly selective surfactant assisted kinetic spectrophotometric method for the determination of thallium has been developed. The method is based on the quantitative oxidation of Tl(I) to Tl(III) using bromine water where the resulting Tl(III) liberated iodine from potassium iodide in acidic medium. The liberated iodine was subsequently reacted with I− ion to form tri-iodide ions (I3−). The tri-iodide ions formed were further reacted with cetylpyridinium cation (CP+) which produced a violet ion associate species having a λmax of 512nm at which reaction was monitored. The reaction variables such as time, temperature, reagent concentration and acidity were optimized for the indicator reaction to achieve maximum sensitivity. The linear regression calibration concentration range of 0.007–0.1μgmL−1 Tl(I) was established as the Beer's law was obeyed in this range. Sandell's sensitivity and molar absorptivity of the ion associate species in terms of thallium were determined to be 0.000133μgcm−2 and 1.99×106Lmol−1cm−1 respectively. The limit of detection was determined as 0.0029μgmL−1. The developed method has successfully been applied for the determination of thallium in different environmental samples with satisfactory results.

A cloud point extraction for spectrophotometric determination of ultra- trace antimony without chelating agent in environmental and biological samples

We report on a simple, sensitive and reliable method for the cloud point extraction of antimony (Sb) and its subsequent spectrophotometric detection. It is based on the color reaction of Sb (III) with iodide in acidic medium and subsequent micelle-mediated extraction of tetraiodoantimonate using a non-ionic surfactant in the absence of any chelating agent. The effects of reaction and extraction parameters were optimized. The calibration plot is linear in the range of 0.80–95 ng mL−1 of antimony in the sample solution, with a regression coefficient (r) of 0.9994 (for n = 9). The detection limit (at SNR = 3) is 0.23 ng mL−1, and the relative standard deviations at 10 and 70 ng mL−1 of antimony are 3.32 and 1.85 % (at n = 8), respectively. The method compared favorably to other methods and was applied to determine antimony in seawater, anti-leishmania drug (glucantime), and human serum.

Role of Free Radicals in Modeling the Iodide–Peroxide Reaction Mechanism

The mechanism of monotonous decomposition of hydrogen peroxide by iodide in acidic medium is investigated at room temperature. For this purpose, O(2) pressure, I(-), I(2), and I(3)(-) concentrations are simultaneously monitored, establishing a useful framework for better understanding of the reaction mechanism and testing various models. The possibility of nonradical and radical approaches to describe experimental data is examined. Results suggest that the best description of experimentally recorded components is obtained by introducing free radicals into the model of the reaction.

Ultrasound-assisted cloud point extraction for speciation and indirect spectrophotometric determination of chromium(III) and (VI) in water samples

Ultrasound-assisted cloud point extraction (UACPE) procedure was developed for speciation and indirect spectrophotometric determination of chromium(III) and (VI) in environmental water samples. The method is based on the reduction of Cr(VI) by iodide in acidic media and subsequently formation of I3− anion. The I3− formed can further react with cetyltrimethylammonium bromide (CTAB) and induce its clouding due to formation of an ion-association complex. The formed complex was separated from solution and dissolved in ethanol for spectrophotometric measurement. Cerium(IV) ammonium sulphate was chosen as an oxidizing reagent for pre-oxidation step of Cr(III) to Cr(VI) species before the addition of iodide to the system, up to chromium in trivalent can be determined by the procedure. Experimental parameters for both spectrophotometric reaction and extraction procedure have been optimized. Under optimized conditions Cr(VI) can be determined in the range 20–400ngmL−1 (R2=0.999). Detection limit, preconcentration factor and relative standard deviation were 12ngmL−1, 20.0 and 2.2% (n=5), respectively with 10mL sample volumes. The proposed method has been successfully applied for determination of chromium(V) in spiked water, synthetic seawater and electroplating wastewater samples with average recoveries of 100.1, 99.4 and 99.1%, respectively.

Sequential spectrophotometric determination of trace amounts of periodate and iodate in water samples after micelle-mediated extraction

A cloud point extraction process using the nonionic surfactant Triton X-114 for extraction and preconcentration of periodate and iodate ions from aqueous solution was investigated. The method is based on the extraction of triiodide ion, the colored product of the reaction of periodate and iodate with iodide in acidic media. The triiodide was concentrated in surfactant rich phase and then determined spectrophotometrically at 358 nm. For the determination of periodate and iodate in mixture, two sets of conditions were established. In one set of conditions only periodate reacted with iodide but in the other set both ions reacted with iodide. The data were evaluated by the method of proportional equations. The optimal extraction and reaction conditions (e.g., surfactant and reagent concentrations and centrifuge time) were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration factor, and enhancement factors) were obtained. Under the optimized conditions, the methods allowed the determination of periodate and iodate at concentrations between 2.0 and 1000 and 4.0 and 400 ng/mL, respectively. The proposed method was successfully applied to the determination of periodate and iodate in water samples.

Spectrophotometric Determination of Hydrogen Peroxide Using Leucocrystal Violet in Micellar Medium

A simple and sensitive spectrophotometric method for the determination of hydrogen peroxide, based on the increase in color intensity of dye on addition of surfactant, is described. Hydrogen peroxide is first reacted with potassium iodide in acidic medium, in presence of ammonium molybdate to liberate iodine. The liberated iodine oxidizes leucocrystal violet to crystal violet having maximum absorbance at 593 nm. The color of the dye intensifies with the addition of the surfactant, cetyl pyridinium chloride though the absorption maximum remains the same. Beer's law is obeyed in the range 0.05–0.45 µg of hydrogen peroxide per 25 mL of final solution (0.002–0.018 µg mL−1) with an excellent correlation coefficient (r = 0.9977). The proposed method has been successfully applied for the analysis of hydrogen peroxide in various food products and rainwater.

Aerobic Oxidative Iodination of Organic Compounds with Iodide Catalyzed by Sodium Nitrite

AbstractSelective and efficient iodinations of organic compounds were achieved by an aerobic oxidative process catalyzed by sodium nitrite using potassium iodide in acidic media. Using the potasasium iodide (KI)/air/sodium nitrite (NaNO2; cat.)/sulfuric acid (H2SO4) iodinating system, activated and moderately deactivated aromatic compounds were exclusively or preferentially iodinated at the para position. In protic solvents ketones and 1,3‐dicarbonyl compounds were iodofunctionalized at the α carbonyl position, while in the case of aryl methyl ketones bearing an activated aromatic ring, the regioselectivity of iodination could be directed by the solvent used. In acetonitrile (MeCN) the aromatic ring was selectively iodinated, while in aqueous rethanol (EtOH) functionalization of the methyl carbon atom took place. Alkenes were transformed to vicinal iodohydrins or vicinal iodoalkoxy derivatives following Markovnikov‐type regioselectivity and anti stereoselectivity, while 1,2‐diiodoalkenes with preferentially E orientation were formed from alkynes.

Kinetic-spectrophotometric determination of Sb(V) based on its reaction with iodide in the presence of methylene blue

A rapid, simple, and sensitive kinetic method is developed for the determination of trace amounts of Sb(V). The method is based on the reaction of Sb(V) with iodide in acidic media in the presence of methylene blue. The reaction was monitored spectrophotometrically by measuring the decrease in the absorbance at 664 nm by a fixed-time technique of 60 s. The method allowed the determination of Sb(V) at concentrations between 0.01 and 2.2 μg/mL. The limit of detection was 0.006 μg/mL and the relative standard deviation for ten replicate measurements of 0.5 μg/mL Sb(V) was 1.2%. The method was applied to the determination of Sb(V) in tap water and spring water with satisfactory results.

An Easy Spectrophotometric Method for the Determination of Hypochlorite Using Thionin

A simple, rapid, and sensitive spectrophotometric method has been developed for the determination of hypochlorite using thionin. The method is based on the reaction of hypochlorite with potassium iodide in acidic medium to liberate iodine. The liberated iodine bleaches the violet color of thionin, which is measured at 600 nm. The decrease in absorbance is directly proportional to the concentration of hypochlorite. Beer’s law is obeyed in the range 0.2– 1.2 µg/mL of hypochlorite. The molar absorptivity, Sandell’s sensitivity, detection limit, and quantitation limit are found to be 1.489 × 104 L/(mol cm), 3.25 × 10−3 µg cm−2, 0.1026 µg/mL, and 0.3112 µg/mL, respectively. The method has been successfully applied to the determination of hypochlorite in various samples of natural water, tap water, milk, etc.

One‐Pot Conversion of Azido Arenes to N‐Arylacetamides and N‐Arylformamides: Synthesis of 1,4‐Benzodiazepine‐2,5‐diones and Fused [2,1‐b]Quinazolinones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

One pot conversion of azido arenes to N-arylacetamides and N-arylformamides: synthesis of 1,4-benzodiazepine-2,5-diones and fused [2,1- b]quinazolinones

Sodium iodide in acidic media has been employed for the synthesis of N-arylformamides and N-arylacetamides. The NaI/acetic acid reagent system has also been extended for the synthesis of 1,4-benzodiazepine-2,5-diones, pyrrolo[2,1- c][1,4]benzodiazepine-5,11-diones, and fused [2,1- b]quinazolinones.

A Simple Sensitive Spectrophotometric Method for the Determination of Ce 4+ Using Variamine Blue as a Chromogenic Reagent

A rapid and sensitive spectrophotometric method is described for the determination of trace amounts of cerium using Variamine Blue (VB) as a chromogenic reagent. The proposed method is based on the reaction of cerium with potassium iodide in acidic medium to liberate iodine, which oxidizes Variamine Blue to give a violet colored species with an absorption maximum at 560 nm. Beer's law was obeyed in the range 2-10m gm L � 1 of cerium. The molar absorptivity and Sandell's sensitivity are found to be 1.65� 10 4 L mol � 1 cm � 1 and 8.48� 10 � 3 m gc m � 2 , respectively. The proposed method has been successfully applied to the determination of cerium in alloy and synthetic mixtures.

Reverse flow injection spectrophotometric determination of iodate and iodide in table salt

A very simple and sensitive reverse flow injection method is described for the determination of iodate and iodide. The iodate reacts with excess iodide in acidic medium to form tri-iodide, which can be spectrophotometrically monitored at 351nm, and the absorbance is directly related to the concentration of iodate in the sample. The determination of iodide is based on oxidizing iodide to iodate. The calibration curve is linear in the range of 0.02–3.0μgml−1 I with r2=0.9998, and the limit of detection is 0.008μgml−1 I. The chemical and flow injection variables were studied and optimized to make the procedure suitable for quantitating iodate and iodide in table salts. It is shown that the reverse flow injection analysis could greatly improve the sensitivity and precision for determination of iodate with a relative standard deviation of 0.9%. A complete analysis, including sampling and washing, could be performed in 35s. The procedure was applied successfully to the determination of iodate and iodide in table salts, and the results were statistically compared with results determined by standard iodometry method.

Simultaneous spectrophotometric determination of Bi(III) and Sb(III) based on their complexes with iodide in acidic media using the H-point standard addition method and first-derivative spectrophotometry.

The H-point standard addition method (HPSAM) was applied to the simultaneous determination of Bi(III) and Sb(III). This method is based on the difference in the absorbance of complexes of Bi(III) and Sb(III) with iodide in acidic media in different wavelength pairs. The results showed that Bi(III) and Sb(III) can be determined simultaneously with concentration ratios of 15:1 to 1:20. First-derivative spectrophotometry was also used for the simultaneous determination of Bi(III) and Sb(III) based on their complexes with iodide. The proposed methods were successfully applied to the simultaneous determination of Bi(III) and Sb(III) in synthetic samples.