Determination of Coenzyme II Using Balofloxacin–Terbium(III) as a Fluorescence Probe by Spectrofluorometry

Abstract

A new spectrofluorometric method was developed for determination of coenzyme II. We studied the interactions between balofloxacin–terbium(III) complex and coenzyme II by using ultraviolet–visible absorption and fluorescence spectra. While balofloxacin–terbium(III) was used as a fluorescence probe, under the optimum conditions, coenzyme II could remarkably enhance the fluorescence intensity of the balofloxacin–terbium(III) complex at λ = 545 nm, and the enhanced fluorescence intensity was in proportion to the concentration of coenzyme II. Optimum conditions for the determination of coenzyme II were also investigated. The dynamic range for the determination of coenzyme II was 6.0 × 10^?8 to 6.0 × 10^?6 mol L^?1, and the detection limit (3σ/k) was 3.5 × 10^?8 mol L^?1. This method was simple, practical, and relatively free interference from coexisting substances and could be successfully applied to determination of coenzyme II in synthetic samples. The mechanism of fluorescence enhancement of balofloxacin–terbium(III) complex by coenzyme II was also discussed.     

Potentiometric Dipyridamole Sensors Based on Lipophilic Ion Pair Complexes and Native Ionic Polymer Membranes

Abstract

A new spectrofluorimetric method was developed for the determination of trace amounts of lecithin. Using enoxacine (ENX)‐terbium ion (Tb³⁺) as a fluorescent probe, in a buffer solution at pH=5.80, lecithin can remarkably reduce the fluorescence intensity of the ENX‐Tb³⁺ complex at λ=545 nm; the reduced fluorescence intensity of the Tb³⁺ ion is proportional to the concentration of lecithin. Optimum conditions for the determination of lecithin were also investigated. The linear range and detection limit for the determination of lecithin were 1.96×10^?7–9.8×10^?6 mol l^?1 and 9.74×10^?8 mol l^?1. This method is simple, practical and relatively free of interference from coexisting substances, and can be successfully applied to assess lecithin in serum samples.     

Sensitive Determination of Prulifloxacin by Its Fluorescence Enhancement on Terbium(III)–Sodium Dodecylbenzene Sulfonate System

Abstract

A terbium-sensitized fluorescence spectrophotometry method using an anionic surfactant, sodium dodecyl benzene sulphonate (SDBS), was developed for the determination of prulifloxacin (PUFX). It was found that SDBS significantly enhanced the fluorescence intensity of the PUFX–Tb³⁺ complex (about 13-fold). The optimal experimental conditions were determined as follows: excitation and emission wavelengths of 290 nm and 545 nm, pH 8.0, 4.0 × 10^?5 mol L^?1 terbium(III), and 4.0 × 10^?4 mol L^?1 SDBS. The enhanced fluorescence intensity of the system (ΔF) showed a good linear relationship with the concentration of PUFX over the range 6.0 × 10^?8 to 2.0 × 10^?6mol L^?1 with a correlation coefficient of 0.9991. The detection limit (S/N = 3) was determined as 8.5 × 10^?9 mol L^?1. This method has been successfully applied for the determination of PUFX in pharmaceuticals and human urine/serum samples. Compared with most other methods reported, the rapid and simple procedure proposed here offered higher sensitivity, wider linear range, and good stability. The luminescence mechanism of the system was also discussed in detail. In the fluorescence system of PUFX–Tb³⁺–SDBS, SDBS acted not only as the surfactant but also as the energy donor.     

Highly Sensitive Spectrofluorimetric Determination of Trace Amounts of Superoxide Dismutase Using a Prulifloxacin-Terbium(III) Probe

Abstract

A new spectrofluorimetric method was developed for determining superoxide dismutase. The interactions between prulifloxacin (PUFX) –Tb³⁺ complex and superoxide dismutase had been studied by using UV-Vis absorption and fluorescence spectra. Using prulifloxacin–Tb³⁺ as a fluorescence probe, under optimum conditions, superoxide dismutase could remarkably enhance the fluorescence intensity of the prulifloxacin–Tb³⁺ complex at λ = 545 nm, and the enhanced fluorescence intensity was in proportion to the concentration of superoxide dismutase. Optimum conditions for the determination of superoxide dismutase were also investigated. The dynamic range for the determination of superoxide dismutase was 0.032 to 22.56 µg mL^?1, and the detection limit (S/N = 3) was 1.5 ng 4 mL^?1. This method was simple, practical, and relatively free of interference from coexisting substances and could be successfully used to determine superoxide dismutase in the plant and blood samples. The mechanism of fluorescence enhancement of prulifloxacin–Tb³⁺ complex by superoxide dismutase was also discussed.     

Enoxacin—Tb3+ Complex as an Environmentally Friendly Fluorescence Probe for Coenzyme A and Its Application

Abstract

A new spectrofluorimetric method was developed for the determination of trace amounts of coenzyme A using enoxacin–Tb³⁺ as a fluorescent probe. In the presence of periodic acid (H₅IO₆), coenzyme A could remarkably enhance the fluorescence intensity of the Tb³⁺–enoxacin complex at 545 nm at pH 5.4. The optimal conditions for the determination of coenzyme A were also investigated. This method could be successfully applied to assess coenzyme A in injection and biological samples. Moreover, the enhancement mechanism of the fluorescence intensity of the coenzyme A–Tb³⁺–enoxacin system in the presence of H₅IO₆ was also discussed.     

Photochemical Fluorescence Enhancement of Terbuium-Fleroxacin System and Determination of Fleroxacin

ABSTRACT

The sensitized fluorescence of the terbium ion (Tb³⁺) can be observed when excited in the presence of fleroxacin (FLRX) in the aqueous solution because a Tb³⁺ -FLRX complex was formed. The sensitised fluorescence was greatly enhanced after the complex system was irradiated by 365nm ultraviolet light. The irradiation makes the complex system undergo photochemical reactions and a new terbium complex which is more favourable to the intramolecular energy transfer is formed. On this basis a new sensitive and selective photochemical fluorimetric method for the determination of FLRX was developed. Under the optimum experimental conditions, the linear range of the determination is 1.0—200×10^?7 mol 1^?1 for FLRX, and the detection limit is 1.2×10^?8mol 1^?1. Without any pre-treatment the recoveries of FLRX in human urine samples were determined with satisfaction.     

Chlorodesmethyldiazepam Fluorimetric Determination in Pharmaceutical Formulations and in Aqueous Media

Abstract

A direct fluorimetric method for the determination of chlorodesmethyldiazepam was proposed. The fluorescence process was pH dependent. The dynamic range for the method was 1.6–12 µg ml^–1. A linear relationship between the fluorescence intensity and the concentration of chlorodesmethyldiazepam solution was obtained with r ² of 0.9958. The detection limit for the method was found to be 0.224 µg ml^–1. The method has successfully applied to the determination of chlorodesmethyldiazepam in pure, authentic, and aqueous samples.     

Fluorimetric Determination of Gatifloxacin in Aqueous,Pure and Pharmaceutical Formulations

Abstract

A spectrofluorimetric method was developed for the determination of gatifloxacin. The emission peak for gatifloxacin was recorded at 495 nm upon excitation at 291 nm. The fluorescence process was pH dependent. The dynamic range for the method was 16–80 ng ml^?1with detection limit of 3.97 ng ml^?1. A linear relationship between the fluorescence intensity and the concentration of gatifloxacin solution was obtained with r ² of 0.9968. The method has successfully applied to the determination of gatifloxacin in pure, authentic and aqueous samples.     

Determination of DNA based on fluorescence quenching of terbium doped carbon dots

This work describes the preparation of carbon dots doped with terbium(III) (Tb-CDs) via a hydrothermal method, starting from terbium ion and ethylenediamine. The size, composition and spectral properties of the Tb-CDs were characterized by transmission electron microscopy, infrared spectra, and fluorescence spectra. The results show that doping of the CDs with Tb(III) reduces the particle size and results in more uniform particles, while fluorescence (at excitation/emission peaks of 380/475 nm) is strongly enhanced. The interaction between Tb-CDs and ct-DNA results in fluorescence quenching of Tb-CDs. The findings were exploited to design a quenchometric method for the determination of ct-DNA. The signal drops linearly in the 80 ng·mL^?1 to 50 μg·mL^?1 ct-DNA concentration range, and the detection limit is 53 ng·mL^?1. The method was applied to the determination of ct-DNA in spiked samples and gave satisfactory results. The possible fluorescence quenching mechanism (which is mainly static) was investigated using the Stern–Volmer equation and thermodynamic equations.

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Graphical abstract A kind of carbon dots doped with terbium(III) (Tb-CDs) were prepared via a hydrothermal method, using terbium ion and ethylenediamine as precursor. Doping with Tb(III) reduced the particle size of CDs and results in uniform particle size and stronger fluorescence. The interaction between the Tb-CDs and dsDNA results in quenching of the fluorescence of Tb-CDs and can be applied to determination of dsDNA.

     

Spectrofluorimetric method for the determination of uric acid in human serum

A new spectrofluorimetric method is described for the determination of uric acid (UA), that can remarkably reduce the fluorescence intensity of the enoxacin (ENX)-terbium ion (Tb³⁺) complex at 545 nm. The reduced fluorescence intensity of Tb³⁺ ion at pH 5.7 is proportional to the concentration of UA. Optimum conditions for the determination of UA have been investigated. The linear range and detection limit for the determination of UA are 6.0 × 10^?7–3.0 × 10^?5 M and 1 × 10^?7 M, respectively. The relative standard deviation (RSD) was 0.4% for 6 × 10^?6 M UA (n = 11). The method is simple, practical and relatively free of interferences. It has been successfully applied to assess UA in serum at the level of 3 × 10^?4 M with an RSD of 5–7% (n = 3). The results were evaluated by comparison with a common clinical spectrophotometric method using phosphotungstic acid as developer.     

Sensitive detection of dopamine using micelle-enhanced and terbium-sensitized fluorescence

A new terbium sensitized spectrofluorimetric method was developed for the determination of trace amounts of dopamine (DA) using ethylenediaminetetraacetic acid as co-ligand and cetyltrimethylammonium chloride as sensitizer. UV absorption and fluorescent spectra were used to investigate the photophysical properties of the ternary complex. Under the optimum conditions, the enhanced fluorescence intensities of the Tb(III) complexes increased linearly with the concentration of DA over the ranges 8 × 10^–8–5 × 10^–5 M and the limit of detection for DA was found to be 2.4 × 10^–8 M. The proposed method has been applied for the quantitative determination of DA in a pharmaceutical preparation and urine samples. The possible energy transfer mechanisms in the lanthanide complexes were discussed.     

Determination of Folic Acid at a Bismuth Film Electrode by Adsorptive Stripping Voltammetry

This article reports a new simple and sensitive method for the determination of folic acid by adsorptive stripping voltammetry. The method is based on the accumulation of folic acid at a bismuth film plated in situ on a glassy carbon substrate. In order to stabilize bismuth ions, sodium potassium tartrate was added to the supporting electrolyte. The bismuth film formation and folic acid accumulation conditions were optimized and measurements were carried without solution deaeration. The calibration graph was linear from 5 × 10^?10 to 2 × 10^?8 mole per liter with an accumulation time of 180 seconds with a limit of detection of 2 × 10^?10 mole per liter. The relative standard deviation for 5 × 10^?9 mole per liter of folic acid was 3.1 percent (n = 5). The method was successfully applied for determination of folic acid in pharmaceutical preparations.     

Fluorescent carbon dots derived from lactose for assaying folic acid

The fluorescent carbon dots were successfully synthesized by simply heating the mixture of lactose and Na OH solution. The as-synthesized carbon dots had been systematically characterized by fluorescence, Fourier transform infrared(FTIR), high resolution transmission electron microscopy(HR-TEM) and ~(13)C NMR. Since the fluorescence of the carbon dots was efficiently quenched by folic acid, the carbon dots were employed as selective fluorescence probes for detecting folic acid, depending on the formation of hydrogen bond among the functional group of folic acid(–OH, –COOH and –NH_2) and –OH and –COOH of the carbon dots. Moreover, the decrease of fluorescence intensity was capable of detecting folic acid in a linear range of 6×10~(-5)–8×10~(-8) mol/L with a detection limit of 1.2×10~(-9)mol/L at a signal-to-noise ratio of 3, suggesting a promising assay for folic acid. Significantly, the practicability of this fluorescence probe to assay folic acid in human urine samples was further evaluated.     

Novel Copper(II)-Selective Potentiometric Sensor Based on a Folic Acid-Functionalized Carbon Nanotube Material

Abstract

A folic acid-functionalized carbon nanotube nanomaterial was prepared by immobilizing folic acid molecules on the carbon nanotubes through covalent bonds. The material was characterized using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy. Fourier transform infrared spectroscopy confirmed that folic acid molecules were grafted on the carbon nanotube surfaces through the amide bonds between the carboxylic acid functional groups of the oxidized carbon nanotubes and the amine groups of the folic acid molecules. The folic acid molecules bonded to carbon nanotube surfaces led to appreciable changes in the morphology. By using currently obtained folic acid-functionalized carbon nanotube nanomaterial as electroactive material in a polyvinyl chloride membrane, a potentiometric copper (II)-selective sensor was developed. Membrane optimization studies showed that the composition exhibiting the best potentiometric properties was 4.0% (w/w) folic acid–carbon nanotube, 64.0% (w/w) o-nitrophenyl octylether, and 32.0% (w/w) polyvinyl chloride. The developed sensor displayed a linear response in the copper (II) concentration ranging from 1.0?×?10^–6 to 1.0?×?10^–1 M with a correlation coefficient of 0.9993 and a slope of 29.8?±?0.6?mV/decade of activity. The response time, detection limit, and pH working range were determined to be 4?s, 3.8?×?10^–7 M and 4.0–8.0, respectively. The developed sensor showed highly selective and satisfactory potentiometric response for the determination of copper (II) in a Turkish coin.     

Fluorimetric Determination of p -Hydroxybenzoic Acid in Beer as α -Cyclodextrin Inclusion Complex

Abstract

The inclusion complex of p-hydroxyenzoic acid and α- and β-cyclodextrin has been studied by fluorescence spectroscopy. To describe quantitatively complex formation between α-cyclodextrin (α-CD) and p-hydroxybenzoic acid, an association constant of 967 ± 14 M^?1 at 21°C was obtained. The inclusion complex has been used to determine p-hydroxybenzoic acid in the range 0.15–1.00 mg L^?1 (RSD 4.5%, n = 8). Application of the method to determination of p-hydroxybenzoic acid in beer samples gave an endogenous content of 1.25 mg L^?1.     

Highly sensitive spectrofluorimetric determination of trace amounts of lecithin

A new spectrofluorimetric method was developed for the determination of trace amounts of lecithin using the ciprofloxacin (CIP)–terbium (Tb³⁺) ion complex as a fluorescent probe. In a buffer solution at pH=5.60, lecithin can remarkably reduce the fluorescence intensity of the CIP–Tb³⁺ complex at λ=545 nm. The reduced fluorescence intensity of the Tb³⁺ ion is proportional to the concentration of lecithin. Optimum conditions for the determination of lecithin were also investigated. The linear range and detection limit for the determination of lecithin were 1.0×10⁻⁶–3.0×10⁻⁵ mol L⁻¹ and 3.44×10⁻⁷ mol L⁻¹, respectively. This method is simple, practical, and relatively free of interference from coexisting substances. Furthermore, it has been successfully applied to assess lecithin in serum samples.      

Synchronous fluorescence analysis of phytate in food

A novel synchronous fluorescence method is described for determination of phytic acid in food samples. It is based on the formation of a ternary complex between phytate, 1,10-phenanthroline (phen) and Fe³⁺. The synchronous fluorescence intensity of the solution was accordingly enhanced proportionally to the increased phytate concentration. Synchronous luminescence spectroscopy was adopted in the study, and the Δλ was set to 40 nm. The calibration graph is linear from 0.33 to 32 mg L^?1 with a linear equation of I _f?=?8.770?+?2.980c (R ²?>?0.9994). The method was applied to determine phytate in food samples and the found concentrations of phytic acid in food were in the range of 4.62–24.08 mg g^?1 with recoveries of 92.2%–98.3%. The control experiments were performed using UV-spectrophotometry method, and the results showed the method to be reliable.     

Spectrofluorimetric trace determination of terbium(III) with potassium oxalate

Potassium oxalate acts as a specific reagent in enhancing the fluorescence intensity of terbium in aqueous solutions. Maximum fluorescence intensity is obtained by irradiating (at 255 mμ) terbium(III) dissolved in 0.01 M potassium oxalate solution at pH 7.8. The enhancement and quenching phenomena caused by other lanthanides, errors in the determination, and various examples of spectrofluorimetric analysis of traces of terbium in mixtures with other lanthanides are described. The sensitivity of the method is 5·10^-2μg/ml of terbium.     

Chemiluminescence Determination of Tetracyclines via Aluminum Sensitized Fluorescence

Tetracycline, oxytetracycline, doxycycline, and chlortetracycline have been determined by chemiexcitation of the corresponding Al(III) highly fluorescent complex from the permanganate or cerium(IV)-sulphite chemiluminogenic reactions. Limits of detection and ranges of linearity are equal to 0.024, 0.015, 0.014, and 0.050 µg mL^?1 and 0.067–3.20, 0.042–1.70, 0.042–3.00, and 0.103–2.80 µg mL^?1 for tetracycline, oxytetracycline, doxycycline, and chlortetracycline, respectively. Average recovery of tetracyclines from solutions of commercial formulations was equal to 99.8% and the procedure was successfully applied to the determination of tetracyclines in commercial products with mean relative error equal to 3.4% (range 1.4–5.0%).     

Fluorescence Enhancement of Rare Earths by Yttrium and its Application

Abstract

A study of the enhancement effect on the fluorescence intensity of the Eu³⁺–-thenoyltrifluoroacetone (TTA)–-cetyltri–-methylammonium bromide (CTMAB) and the Dy³⁺ pyrocatechol–-3,5-disulphonic acid (Tiron) systems by Y³⁺has been carried out. In the presence of yttrium the fluorescence intensity of the systems was enhanced by a factor of about 100 and 15, respectively. The fluorescence intensity was a linear function of the concentration of europium or dysprosium in the range 1.0 × 10^?10–-1.0 × 10^?8mol dm^?3 and 8.0 × 10^?8–-9.0 × 10^?6mol dm^?3, respectively. The detection limit was 1.0 × 10^?11mol dm^?3 and 1.0 × 10^?10mol dm^?3, respectively. The standard addition method was used for the determination of europium or dysprosium in rare earth oxides and gave satisfactory results. The mechanism of enhanced fluorescence was proposed.