Study on the Fluorescence System of Oxolinic Acid‐Tb(III) and the Determination of Oxolinic Acid

Abstract

In Tris‐HCl buffer (pH=7.43), Tb³⁺ can react with oxolinic acid (OA) and form a 1:2 complex, which emits the intrinsic fluorescence of Tb³⁺. Based on this, a new fluorimetric method of determination of OA is developed. Under the optimum conditions, the enhanced fluorescence intensity of the system is proportional to the concentration of OA in the range of 1.5×10^?7～2.5×10^?5mol/L, and the detection limit is 5.5×10^?9 mol/L. Recovery test was also satisfactory. The experiments indicated that the luminescence mechanism was attributed to the M*–M luminescence.     

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.     

Analytical study of the phenyl-2-pyridyl ketone azine-palladium system. Photometric determination of palladium

Phenyl-2-pyridyl ketone azine reacts with palladium(II) to produce a yellow 1:1 complex (λ_max = 425 nm, ? = 10.4 × 10³M^?1 cm^?1 in aqueous ethanolic solution) and a red-violet 3:1 complex (λ_max = 530?540 and 380?390 nm). The yellow complex in aqueous ethanolic solution has been used for the spectrophotometric determination of trace amounts of palladium. The method has been applied to the determination of palladium in some catalysts and one mineral.     

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.     

Study of Fluorescence System of Gmanylic Acid-Tb3+ and the Determination of Gmanylic Acid

Abstract

It was found that gmanylic acid (GMP) can be selectively completed with Tb³⁺ at pH 6.0-6.6, which then emits strong fluorescence characteristic of Tb³⁺. This reaction can be used for the determination of GMP in presence of adenylic acid (AMP), uridylic acid (UMP) and cylidylic acid (CMP). A linear relationship is obtained between the fluorescence intensity and GMP concentration in the range of 2.0×10^?7 - 1.0×10^?4M. The detection limit is 2.0×10^?8 M. The results showed that the composition ratio and apparent stability constant of GMP-Tb complex were 1:1 for GMP Tb³⁺- and 2.3×10^?5, respectively.     

Fluorescence enhancement by gadolinium of the europium or samarium-dibenzoylmethane-diethylamine system

A fluorescence enhancement produced by adding Gd³⁺, Y³⁺, Tb³⁺, La³⁺ or Lu³⁺ to europium or samarium-dibenzoylmethane-diethylamine was observed. Gd³⁺ enhanced the fluorescence intensity by 2–3 orders of magnitude compared with the system without Gd³⁺. The new system was used for the simultaneous determination of traces of Sm³⁺ and Eu³⁺ in the ranges 1.0 × 10^?9?8.0 × 10^?8 M and 1.0 × 10^?11?4.0 × 10^?9 M, respectively, and the detection limits were 5 × 10^?13 M for Sm³⁺ and 8 × 10^?14 M for Eu³⁺. The luminescence mechanism of the system is discussed.     

Electrochemical Behaviour of the Anticancer Dacarbazine‐Cu2+ Complex and Its Analytical Applications

Electrochemical reduction of the dacarbazine‐Cu²⁺ complex was investigated using cyclic voltammetry and square wave voltammetry at a hanging mercury drop electrode. The reduction of the dacarbazine‐Cu²⁺ complex is irreversible. A reduction mechanism is proposed comprising a one‐electron reduction of the Cu²⁺ directly within the complex. The sharp peak of the adsorbed dacarbazine‐Cu²⁺ complex associated with an effective interfacial accumulation facilitates the determination of the anticancer drug dacarbazine in pharmaceutical formulations and biological fluids. Detection limits for dacarbazine of 6.12×10^?10 M, 1.57×10^?10 M and 1.97×10^?9 M were achieved for the determination of the drug in vial, human urine and serum, respectively.     

The electrochemical stripping determination of bismuth in aqueous and nonaqueous media after its extraction

The cyclic voltammetry of bismuth in aqueous media and electrochemical stripping determination of bismuth in aqueous and nonaqueous media after its extraction using a rotating disc electrode of glassy carbon was studied. To raise the conductivity of the organic medium and for the preparation of a convenients medium for the determination of bismuth, an alcoholic (methanol) solution of NH₄SCN+HClO₄ was employed. In non-aqueous medium bismuth can be determined down to concentrations 10^?8M by anodic stripping voltammetry and to 5×10^?8M by anodic stripping chronopotentiometry. The selectivity of the determination of bismuth after its extraction was studied. Electrochemical determination of 10^?6M Bi³⁺ with error ±3–4% was not interfered with by these elements: Co²⁺, Ni²⁺, Zn²⁺, Cd²⁺, As³⁺ in the concentration 8×10^?3M, Fe³⁺, In³⁺, Sn²⁺ and Sn⁴⁺ (5× 10^?3M), Cu²⁺ (10^?3M), Sb³⁺ (1.5×10^?4M) and Hg²⁺ (2×10^?5M). The reproducibility of the electrochemical determination of bismuth according to the recommended procedure is very good.     

A Lanthanide‐Complex‐Based Ratiometric Luminescent Probe Specific for Peroxynitrite

A lanthanide‐complex‐based ratiometric luminescence probe specific for peroxynitrite (ONOO^?), 4′‐(2,4‐dimethoxyphenyl)‐2,2′:6′,2′′‐terpyridine‐6,6′′‐diyl]bis(methylenenitrilo)tetrakis(acetate)‐Eu³⁺/Tb³⁺ ([Eu³⁺/Tb³⁺(DTTA)]), has been designed and synthesized. Both [Eu³⁺(DTTA)] and [Tb³⁺(DTTA)] are highly water soluble with large stability constants at ≈10²⁰, and strongly luminescent with luminescence quantum yields of 10.0 and 9.9 %, respectively, and long luminescence lifetimes of 1.38 and 0.26 ms, respectively. It was found that the luminescence of [Tb³⁺(DTTA)] could be quenched by ONOO^? rapidly and specifically in aqueous buffers, while that of [Eu³⁺(DTTA)] did not respond to the addition of ONOO^?. Thus, by simply mixing [Eu³⁺(DTTA)] and [Tb³⁺(DTTA)] in an aqueous buffer, a ratiometric luminescence probe specific for time‐gated luminescence detection of ONOO^? was obtained. The performance of [Tb³⁺(DTTA)] and [Eu³⁺/Tb³⁺(DTTA)] as the probes for luminescence imaging detection of ONOO^? in living cells was investigated. The results demonstrated the efficacy and advantages of the new ratiometric luminescence probe for highly sensitive luminescence bioimaging application.     

Method for determination of fluoroquinolones based on the plasmonic interaction between their fluorescent terbium complexes and silver nanoparticles

We report on a fluorometric method for the determination of the fluoroquinolones levofloxacin (LEV) and moxifloxacin (MOXI). It is based on the Tb(III)-sensitized luminescence that is plasmonically enhanced by silver nanoparticles (Ag NPs). The emission of the Tb(III) complexes has maximum at 545?nm after excitation at 284?nm and is strongly enhanced in the presence of the colloidal Ag NPs. Under optimum experimental conditions, luminescence intensity increases linearly with the concentration in the range from 4.16?×?10^-17-3.59?×?10^-15?M of LEV, and from 4.98?×?10^-17-2.49?×?10^-15?M for MOXI with correlation coefficients of 0.9996 and 0.9996, respectively. The limits of detection are 7.19?×?10^-18?M and 8.47?×?10^-18?M, respectively, and the relative standard deviations are 1.3 and 1.5% for 5 replicate measurements at 6.08?×?10^-14?M of LEV and 5.48?×?10^-14?M of MOXI. The method was successfully applied to the determination of LEV and MOXI in pharmaceutical samples, in urine and in serum.

Fluorometric Determination of Traces Of Mg(II) Using 1, 5-Dihydroxyanthracuinone as Reagent

Abstract

The florescent characteristics of the complex formed by 1, 5-dihydroxyanthraquinone with Mg(II) in aqueous ethanol (λ_ex 490 nm,λ_em=600 nm; pH_ap=9.1-9.6; 10% H₂O; reagent concentration=4×10^?5M) are described. The stoichiometry and the stability constant (1:1 and log K=4.90) are determined. A new fluorometric method for the determination of 10-100 ppb Mg(II) is proposed.     

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.     

Anodic stripping voltammetric determination of arsenic(III) using a glassy carbon electrode modified with gold-palladium bimetallic nanoparticles

We have developed a method for the determination of the three catecholamines (CAs) epinephrine (EP), norepinephrine (NE), and dopamine (DA) at sub-nanomolar levels. It is found that the luminescence of the complexes formed between the CAs and Tb³⁺ ion is strongly enhanced in the presence of colloidal silver nanoparticles (Ag-NPs). The Ag-NPs cause a transfer of the resonance energy to the fluorophores through the interaction of the excited-state fluorophores and surface plasmon electrons in the Ag-NPs. Under the optimized condition, the luminescence intensity of the system is linearly related to the concentration of the CAs. Linearity is observed in the concentration ranges of 2.5–110?nM for EP, 2.8–240?nM for NE, and 2.4–140?nM for DA, with limits of detection as low as 0.25?nM, 0.64?nM and 0.42?nM, respectively. Relative standard deviations were determined at 10?nM concentrations (for n?=?10) and gave values of 0.98%, 1.05% and 0.96% for EP, NE and DA, respectively. Catecholamines were successfully determined in pharmaceutical preparations, and successful recovery experiments are demonstrated for urine and serum samples.

Lifetime studies of the HgNH3 complex

The luminescence induced by the Hg-photosensitized reaction of NH₃ was studied by repetitive fast pulsed excitation. From observations of the decay of the luminescence, the emitter of the 290 nm fluorescence was found to be the precursor of the 340 nm emission (the stabilized complex). The first-order decay rate of the stabilized complex was found to be given by 1/τ_O + k[NH₃], where τ₀ = 2.3 μs and k = 3.5 × 10^?13 cm³ molecule^?1 s^?1.     

Rapid Determination of Minocycline in Pharmaceutical Formulations and Human Urine/Serum Samples Based on the Minocycline-Europium-Sodium Dodecylbenzene Sulfonate Luminescence System

Abstract

A new luminescence method based on the minocycline (MNC)-europium (Eu³⁺)-sodium dodecylbenzene sulfonate (SDBS) system was developed for the determination of MNC. SDBS formed a ternary complex with MNC-Eu³⁺ and significantly enhanced the luminescence intensity of Eu³⁺. The enhanced luminescence intensity showed a good linear relationship with the concentration of MNC over the range of 4.0 × 10^?7 ～ 1.0 × 10^?5 mol L^?1 with a detection limit of 2.0 × 10^?8 mol L^?1. This method is rapid and sensitive, and has been successfully applied for the determination of MNC in capsules and human urine/serum samples. The luminescence mechanism is also studied.     

Sequential Injection Analysis of Ciclopirox Olamine Using Lanthanide-Sensitized Luminescence Detection

Ciclopirox olamine is an antifungal agent widely used in dermatological formulations for topical application. The methods described for its determination usually present time-consuming sample treatment or require major human participation. Here we present a rapid flow system for the determination of ciclopirox olamine, based on the use of sequential injection analysis with terbium-sensitized luminescence detection. The reaction between terbium and the analyte is carried out on-line, recording the analytical signal at 300/545 nm (λ_ex/λ_em). A detection limit of 15 µg L^?1 and a R.S.D. of 3% (n = 10) were obtained. It is worth mentioning that the method here presented is the only one that uses a flow system for the determination of ciclopirox olamine.

The flow system was applied to the analysis of different pharmaceutical preparations available in the Spanish Pharmacopoeia. A recovery study was performed, obtaining satisfactory results. The high solution throughput obtained, 50 samples per hour, makes the method suitable for its implementation in pharmaceutical laboratories for routine analysis.     

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.     

Spectrophotometric microdetermination of anti-Parkinsonian and antiviral drug amantadine HCl in pure and in dosage forms

Two simple, rapid, sensitive, low-cost, and accurate methods (A and B) for the microdetermination of amantadine HCl (AMD) in pure form and in pharmaceutical formulations are developed. Method A is based on the formation of tris (o-phenanthroline)-iron(II) complex (ferroin) upon reaction of amantadine HCl with an iron (III)-o-phenanthroline mixture in sodium acetate-acetic acid buffer media. The ferroin complex is spectrophotometrically measured at λ_max 509 nm against reagent blank. Method B is based on the reduction of Fe (III) by the drug which forms colored complex (λ_max 521 nm) with 2,2′-bipyridyl. Optimizations of the experimental conditions are described. Beer’s law is obeyed in the concentration ranges 0.4–10 and 0.6–22 μg mL^?1 using 1,10-phenanthroline and 2,2′-bipyridyl, respectively. The developed methods have been successfully applied for the determination of AMD in bulk drugs and in pharmaceutical formulations. The common excipients and additives did not interfere in their determinations.     

A sequential injection method for the determination of piroxicam in pharmaceutical formulations using europium sensitized fluorescence

A simple, selective and sensitive luminescence method for the assay of piroxicam (PX) in pharmaceutical formulation is developed. The method is based on the luminescence sensitization of europium (Eu³⁺) by complexation with PX. The signal for PX–EU is monitored at λ_ex=358 nm and λ_em=615 nm. Optimum conditions for the formation of the complex in methanol were 0.01 M TRIS buffer and 0.2 mM of Eu³⁺ which allows the determination of 100–2000 ppb of pX in batch method and 100–1000 ppb with limit of detection (LOD) = 23.0 ppb using sequential injection analysis (SIA). The relative standard deviations of the method range between 2 and 3% indicating excellent reproducibility of the method. The proposed method was successfully applied for he assay of PX in pharmaceutical formulations (Feldene capsules and tablets). Average recoveries of 101.0±0.3 and 98.8±2.7% were obtained for capsules in methanol using batch and sequential injection (SI) methods, respectively.     

Rare earth complexes chemiluminescence catalyzed by gold nanoparticles for fast sensing of Tb3+ and Eu3+

Developing multiplex sensing technique is of great significance for fast sample analysis. However, the broad emissions of most chemiluminescence(CL) luminophores make the multiplex CL analysis be difficult. In this work, a simple and sensitive CL analytical method has been developed for the simultaneous determination of Tb³⁺and Eu³⁺thanking to their narrow band emission. The technique was based on a mixed CL system of periodate(IO₄^-)-hydrogen peroxide(...