A Fluorescence Quenching Method for the Determination of Iodide Ion with Salicylfluorone and Hydrogen Peroxide

Abstract

A highly sensitive and selective fluorescence quenching method has been developed for rapid determination of iodide ion with salicylfluorone (SAF) as fluorogenic reagent (λ_ex = 495 nm, λ_em = 520 nm) at pH 2.5-3.0. The calibration graph is linear over the range 0.05-300 μg/25 ml. The detection limit is 0.05 μ/25 ml iodide. Other halide ions do not interfere with the determination even when present in large excess. The method is rapid and was successfully applied for the determination of iodide ion in sodium chloride, table salt and low sodium salt.     

A Fluorimetric Method for the Determination of Cyanide with Fluorescein and Iodine∗

Abstract

A rapid, simple and sensitive fluorimetric method has been developed for the determination of cyanide with fluorescein as fluorogenic reagent (λ_ex = 494 nm, λ_em = 514 nm) at pH 6.0–7.0. A linear calibration curve was obtained in the range 0.004–2.0 μg CN^?/25 ml. The detection limit is 0.004 μg CN^-/25 ml. The method was successfully applied to the determination of cyanide in waste water.

     

A Fluorimetric Method for the Determination of Atmospheric Sulphur Dioxide With 2′, 7′—Dichlorofluorescein∗

Abstract

A rapid, simple and sensitive fluorimetric method has been developed for the determination of atmospheric sulphur dioxide with dichlorofluorescein as fluorogenic reagent (λ_ex = 505 nm, λ_em = 520 nm) at pH 4.0–6.0. A linear calibration curve was obtained in the range 0.01–0.40 μg SO₂/25 ml. The detection limit is 0.01 μg SO₂/25 ml. Nitrogen dioxide does not interfere with the method. The method was successfully applied to the determination of atmospheric sulphur dioxide.

     

Electron transfer. 102. Some oxidations by bromite (BrO2−)

Bromite, BrO₂^?, in aqueous carbonate or borate buffers (pH 9–11), reacts rapidly with H₃AsO₃, with the tartrate complex of Sb(III), and with the EDTA complexes of Sn(II) and U(IV). Each reaction yields Br^?, even when BrO₂^? is taken in excess. Reaction rates with Sb(III) and Sn(II) are independent of pH, but the acidity pattern observed with As(III) points to competing bimolecular reductions by H₂AsO₃^? and H₃AsO₃ having specific rates 3.4 and 1.2 M^?1 s^?1 (25°C, μ = 0.5M). Reduction by U(IV) is strongly inhibited by carbonate; data for carbonate buffers are in accord with the operation of two contributing reaction paths (specific rates 0.45 and 6.3 M^?1 s^?1) with the activated complex for the slower featuring one more carbonate than that for the rapid. Reactions of BrO₂^? with single electron reductants, or with reagents that can undergo both 1e and 2e changes, are generally complicated by variable induction periods, inhibition by O₂, catalyzed decomposition of BrO₂^?, or combinations of these. The much smoother reductions by 2e^? reagents must pass through OBr^?, which reacts much more rapidly than BrO₂^? in each case. An inner-sphere path, operating through an oxygen-bridged transition state and culminating in oxygen atom transfer, is proposed for the 2e reductants. Hypophosphite, despite its highly negative formal potential, is not oxidized by BrO₂^? under our conditions. Here it is likely that the substitution-inert character of the coordinatively saturated P(I) center rules out formation of the precursor required for redox.     

罗丹明6G缔合微粒荧光猝灭法测定痕量碘酸根

研究发现在0.01mol/LHCl-8.0×10-4mol/LKI介质中,罗丹明6G(RhG)在550nm处有1个荧光峰.当有IO-3,I-3与RhG形成缔合微粒,550nm处荧光峰猝灭,在320、400、6103存在时,IO-3与过量的I-反应生成I-nm处有3个共振散射峰,在470nm处有1个同步散射峰.碘酸根浓度在2.0～100×10-7mol/L范围内与荧光猝灭强度成线性关系.据此建立了一个测定食盐中IO-3的荧光猝灭分析法.光谱研究结果表明,(RhG-I3)n缔合微粒和界面的形成是导致体系荧光猝灭的根本原因.     

Lifetime of the B3Σ−u state of S2

Using the single-photon time correlation method, we have determined the lifetime of the S₂(B³Σ^?_u) state from the decay rate of the fluorescence at 370 nm. A lifetime of 45.0 ± 0.6 ns was measured, and the cross section for fluorescence quenching by S₂ as found to be 81.3 ± 4.7 A². A slight dependence of the lifetime on the wavelength of the excitation source over the range of 280 to 337 nm was observed.     

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.     

A Novel Spectrophotometric Method for the Determination of Levodopa with the Detection System of Potassium Ferricyanide‐Fe(III)

In this paper, a novel method has been established to determine levodopa with the detection system of potassium ferricyanide‐Fe(III). In the presence of potassium ferricyanide, it has been demonstrated that Fe(III) is reduced to Fe(II) by levodopa at pH 4.0. In addition, the in situ formed Fe(II) reacts with potassium ferricyanide to form soluble prussian blue (KFe^III[Fe^II(CN)₆]). Beer's law is obeyed in the range of levodopa concentrations of 0.01–4.00 μg mL^?1 at the maximal absorption wavelength of 735 nm. The linear regression equation is A = 0.0082 + 0.61365 C (μg mL^?1) with a correlation coefficient of 0.9996. The detection limit (3σ/k) is 9 ng mL^?1, and R.S.D. is 0.73% (n = 11). Moreover, the apparent molar absorption coefficient of indirect determination of levodopa is 1.2 × 10⁵ Lmol^?1cm^?1. The parameters with regard to determination are optimized, and the reaction mechanism is discussed. This method has been successfully applied to determine levodopa in pharmaceutical, serum and urine samples. Analytical results obtained with this novel assay are satisfactory.     

Spectrofluorimetric Determination of Cu2＋ Using New Fluorogenic Reagent

A new synthesized fluorogenic reagent,8-[(2-pyridine)methylideneamino] quinoline (PMAQ), was utilized for spectrofluorimetric determination of Cu(II) at trace levels. PMAQ, a good fluorogenic reagent, though insoluble in water, but is soluble in ethanol and 20% ethanol-water. The excitation and the fluorescence wavelengths of PMAQ were 310 and 434 nm respectively. When the reagent was complexed with Cu(II), the fluorescence intensity decreased proportionally with the concentration of Cu(II) at pH 4.5 by a static quenching effect. The highest sensitivity to Cu^2＋ determination was shown to be at PMAQ concentration of 1.0×10^－5mol•L^－1. In order to enhance the quenching effect, the Cu(II)-PMAQ complex solution was kept at 22 ℃ for 20 min. Though the interferences by Co(II) and Fe(III) were very serious, they were however, completely eliminated by being masked with oxalate and ascorbate ions respectively. The linear dynamic range for Cu(II) determination was between 25—441 µg•L^－1 with the detection limit of 18 µg•L^－1 (RSD＝3.7%, n＝6). The proposed method was successfully applied to the determination of Cu(II) in real samples including human blood serum, commercial tea and wheat flour.     

Spectrophotometric determination of BrO3− using the 1,2,4-trihydroxyanthraquinone-3-carboxylic acid as reagent

The reaction between the 1,2,4-trihydroxyanthraquinone-3-carboxylic acid and BrO₃^? in hydrochloric acid medium has been studied spectrophotometrically. The red color of the oxidation product serves as basis for a new method for determination of traces of BrO₃^?, measuring the absorbance at 520 nm. The influence of foreign ions on the determination, the stoichiometry of the reaction, and the nature of the oxidation product, have been reported.     

Fluorometric Determination of Arsenic(III) with Fluorescein

A rapid, simple, and sensitive fluorometric method has been developed for the determination of arsenic(III) with fluorescein as fluorogenic reagent (λ_ex= 495 nm, λ_em= 516 nm) at pH 5.2–7.0. A linear calibration curve was obtained in the range 0.01–2.5 μg As(III)/25 ml. The detection limit is 0.01 μg As(III)/25 ml. The method was successfully applied to the determination of arsenic(III) in waste- and river water.     

Spectrofluorimetric determination of BrO 3 − by oxidation of 1,2,4-trihydroxyanthraquinone-3-carboxylic acid

Summary A method is described for the fluorimetric determination of BrO₃, at the nanogram level, based on the oxidation of 1,2,4-tri-hydroxyanthraquinone-3-carboxylic acid in sulfuric acid medium. The fluorescence emission is monitored at 585 nm (wavelength of excitation 521 nm). The method shows a detection limit of 5 ng/ml, being the most sensitive of all the established methods for the determination of this anion by photometry and fluorimetry.

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Spektrofluorimetrische Bestimmung von Bromat durch Oxydation von 1,2,4-Trihydroxyanthrachinon-3-carbonsäure

Zusammenfassung Die fluorimetrische Bestimmung von Bromat im Nanogrammbereich auf der Grundlage der Oxydation von 1,2,4-Trihydroxyanthrachinon-3-carbonsäure in schwefelsaurer Lösung wurde beschrieben. Die Fluoreszenz wird bei 585 nm gemessen (Anregung bei 521 nm). Die Erfassungsgrenze liegt bei 5 ng/ml. Das Verfahren ist somit das empfindlichste unter allen bekannten Methoden zur photometrischen bzw. fluorimetrischen Bestimmung dieses Anions.

     

High‐Performance Liquid Chromatography Determination of Latanoprost in Pharmaceutical Formulations using UV Detection

Abstract

A simple, fast, and accurate high‐performance liquid chromatography (HPLC) method was developed to determine latanoprost in pharmaceutical formulations. The drug was chromatographed on a C₁₈ column. Eluents were monitored at a wavelength of 210 nm using a mixture of acetonitrile and 0.05 M potassium phosphate buffer pH 3.0 (70:30, (v/v). A linear response (r>0.9998) was observed in the range of 10.0–90.0 µg mL^?1. The method showed good recoveries (average 100.4%) and the relative standard deviations intra‐ and inter‐day were ≤1.0%. The method can be used for quality control assay of latanoprost in raw materials as well as in pharmaceutical formulations.     

Spectrofluorimetric Determination of Reduced Glutathione Using Organic Nanoparticle Probes

Introduction Reduced glutathione (GSH) is a very important tripeptide.1 GSH widely exists in living tissues. In ani-mal organization, the concentration of free glutathione is in the range 0.5—10.0 mmol/L. Usually over 99% of glutathione is present in the reduced form in all organ-isms.2 Intermediates of GSH biosynthesis such as cys-teine, g-glutamyl-cysteine (g-Glu-Cys) or cysteinyl-gly- cine (Cys-Gly) also occur in the cell but at much lower concentrations.3 GSH plays an important bio…     

Inclusion as a driving force for the intramolecular charge transfer (ICT) fluorescence of p-(N,N-diphenylamino)benzoic acid methyl ester (DPABME) in α-cyclodextrin (α-CD) aqueous solution

A 1:1 inclusion complex between p-(N,N-diphenylamino)benzoic acid methyl ester (DPABME) molecule and α-cyclodextrin (α-CD) in aqueous solution is formed with a stabilization constant of ca. 45.65 ± 3.59 M^?1 at 25 °C. The formation of the complex is accompanied by enhancement of the long wavelength fluorescence at 510 nm (attributed to intramolecular charge transfer (ICT) due to twisting) relative to the normal fluorescence at 420 nm. In water, the long-wavelength fluorescence is hidden under the red tail of the normal fluorescence band due to quenching by non-radiative transition. Inclusion by CD reduces quenching and thus constitutes a driving force for DPABME to emit at longer wavelength via ICT process.     

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.     

Jodometrische Titration von Perbromat (Bestimmung von BrO 4 − und BrO 3 − nebeneinander)

Perbromate is reduced to bromate by iodide in weakly alkaline solution (pH 7–9) at 100° C. The formation of iodine in the hot solution is prevented by addition of an excess of arsenite, which is finally titrated with a I₂-solution for the determination of BrO ₄ ^? . The total BrO ₃ ^? content is then determinated by titration of the acidified solution with thiosulphate. From both titrations the initial content of BrO ₃ ^? is obtained. Both methods are simple and accurate. A direct method for the determination of BrO ₃ ^? in solutions containing BrO ₄ ^? is also described.     

Hydroxy Naphthol Blue as a Spectrophotometric and Fluorometric Reagent for the Uranyl Ion

Abstract

The utility of hydroxy naphthol blue (HNB) as a spectrophotometric and fluorometric reagent for the uranyl ion has been investigated. In phthalate buffer (at a pH of 4.0), UO₂ ²⁺ forms a brown complex of low absorptivity with the red form of HNB. By following the decrease in HNB absorbance at 530 nm (which has ε = 4.1 × 10³) uranyl ion can be determined to levels as low as 1.1 × 10^?6 M (0.30 μg/ml). HNB also emits at 460 nm when excited at 365 nm at these pH values, while the UO₂ ²⁺ complex exhibits greatly reduced emission. Examination of the quenching of HNB emission by UO₂ ²⁺ allows the determination of uranyl ion to levels as low as 3.2 × 10^?6 M (0.86 μg/ml). A 1:1 type complex was formed between UO₂ ²⁺ and HNB, and a formation constant of 9.77 × 10³ (log K₁ = 3.99) was measured for the complex.     

Novel Method for Selective Spectrophotometric Determination of Titanium(IV) with Water Extract of Slippery Elm Leaf as a New Reagent

Abstract

A novel spectrophotometric method for the determination of titanium(IV) by using a new reagent, water extract of slippery elm leaf is developed. In 0.05 M hydrochloric acid, titanium(IV) reacts with this reagent to form a yellow product. The formed product shows maximum absorbance at 415 nm with a molar absorptivity value of 0.68×10⁴ l mol^–1 cm^–1 and the method was linear in the 0.2–6 µg ml^?1 concentration range. The detection limit value was found to be 0.0131 µg ml^?1. The proposed method was simple, low cost, selective, and sensitive. It was applied to the analytic samples with satisfactory results.     

Reactions of Bromine Fluoride Dioxide,BrO2F,for the Generation of the Mixed‐Valent Bromine Oxygen Cations Br3O4+ and Br3O6+

A reliable synthesis of unstable and highly reactive BrO₂F is reported. This compound can be converted into BrO₂⁺SbF₆^?, BrO₂⁺AsF₆^?_, and BrO₂⁺AsF₆^??2 BrO₂F. The latter decomposes into mixed‐valent Br₃O₄?Br₂⁺AsF₆^? with five‐, three‐, one‐, and zero‐valent bromine. BrO₂⁺ H(SO₃CF₃)₂^? is formed with HSO₃CF₃. Excess BrO₂F yields mixed‐valent Br₃O₆⁺OSO₃CF₃^? with five‐ and three‐valent bromine. Reactions of BrO₂F and MoF₅ in SO₂ClF or CH₂ClF result in Cl₂BrO₆⁺Mo₃O₃F₁₃^?. The reaction of BrO₂F with (CF₃CO)₂O and NO₂ produces O₂Br‐O‐CO‐CF₃ and the known NO₂⁺Br(ONO₂)₂^?. All of these compounds are thermodynamically unstable.