Durable diagnosis of seminal vesicle and sexual gland diseases using the nano optical sensor thin film Sm-doxycycline complex

A new method in which a nano optical sensor for diagnosis of different diseases of seminal vesicle and sexual gland was prepared. The working principle of the method depends on the determination of the fructose concentration in semen of different patients by using nano optical sensor thin film Sm-doxycycline doped in sol–gel matrix. The assay is based on the quenching of the characteristic emission bands of Sm³⁺ present in silica doped Sm-doxycycline nanooptode thin film by different fructose concentrations in acetonitrile at λ_ex = 400 nm. This method was optimized for parameters, such as, solvent effect, operational stability, shelf life and interference parameters. Good and reproducible linearity (1 × 10⁻⁹ – 5.0 × 10⁻⁵ mol L⁻¹) with a detection limit of 9.0 × 10⁻¹⁰ mol L⁻¹ and quantification limit of detection (LOQ) 2.7 × 10⁻⁹ mol L⁻¹ were obtained. Seminal fructose determination in different patient samples after appropriate dilutions confirmed the reliability of this technique. The method was successfully applied for routine fructose monitoring in human semen samples of different cases such as; obstructive and non-obstructive azoospermia, inflammation of male accessory glands, atrophy of seminal vesicle, congenital vas deferens and retrograde ejaculation.     

A novel Lu fluorescent nano-chemosensor using new functionalized mesoporous structures

A new Lu³⁺ sensitive fluorescent chemosensor is designed using 8-hydroxyquinoline functionalized mesoporous silica with highly ordered structure (LUS-SPS-Q). The characterization of LUS-SPS-Q showed that the organized structure has been preserved after the post grafting procedure. The synthesized material showed a selective interaction with Lu³⁺ ion, most probably due to the presence of the fluorophore moiety at its surface. The emission intensity of the Lu³⁺-bound mesoporous material increases with an increase in concentrations of Lu³⁺ ion. Addition of other mono-, di-, trivalent ions resulted in insignificant change in the fluorescent intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Lu³⁺ ion. The linear response range of Lu³⁺ chemo-sensor was from 1.6 × 10⁻⁷ to 1.0 × 10⁻⁵ mol L⁻¹. The Limit of detection obtained was 8.2 × 10⁻⁸ mol L⁻¹ and the pH range which the proposed chemo-sensor can be applied was 3.3–8.3.     

p-Dimethylaminobenzaldehyde thiosemicarbazone: a simple novel selective and sensitive fluorescent sensor for mercury(II) in aqueous solution

A novel and simple fluorophore, p-dimethylaminobenzaldehyde thiosemicarbazone (DMABTS), was prepared in order to find available fluorescent chemosensor for mercuric ion in aquesous solution. DMABTS emitted fluorescence at 448 nm in aqueous solution and its fluorescence intensity was completely quenched upon interaction with Hg²⁺ ions, which should be attributed to the 1:1 complex formation between DMABTS and Hg²⁺. The binding constant of the complex was determined as 7.48 × 10⁶ mol l⁻¹. The linear range of quantitative detection of 0 to 5.77 × 10⁻⁶ mol l⁻¹ and the detection limit of 7.7 × 10⁻⁷ mol l⁻¹ for Hg²⁺ in the 6.3 × 10⁻⁶ mol l⁻¹ DMABTS aqueous solution were obtained from a calibration curve. The coexistence of several transition metal ions and anions did interfere the fluorometric titration of Hg²⁺ ion by less than 4% in the emission change.     

Electrogenerated chemiluminescence from thiol-capped CdTe quantum dots and its sensing application in aqueous solution

In this paper, the electrogenerated chemiluminescence (ECL) from thiol-capped CdTe quantum dots (QDs) was reported. The ECL emission was occurred at −1.1 V and reached a maximum value at −2.4 V when the potential was cycled between 0.0 and −2.5 V. The reduced species of CdTe QDs could react with the coreactants to produce the ECL emission. The CdTe QD concentration (6.64 × 10⁻⁷ mol L⁻¹) of ECL is lower than that (1.0 × 10⁻³ mol L⁻¹) of chemiluminescence (CL). Based on the enhancement of light emission from thiol-capped CdTe QDs by H₂O₂ in the negative electrode potential, a novel method for the determination of H₂O₂ was developed. The light intensity was linearly proportional to the concentration of H₂O₂ between 2.0 × 10⁻⁷ and 1.0 × 10⁻⁵ mol L⁻¹ with a detection limit of 6.0 × 10⁻⁸ mol L⁻¹. Compared with most of previous reports, the proposed method has higher sensitivity for the determination of H₂O₂. In addition, the ECL spectrum of thiol-capped CdTe QDs exhibited a peak at around 620 nm, which was substantially red shifted from the photoluminescence (PL) spectrum, suggesting the surface states play an important role in this ECL process.     

Tris(2,2'-bipyridyl)ruthenium(II)-Zirconia-Nafion composite modified electrode applied as solid-state electrochemiluminescence detector on electrophoretic microchip for detection of pharmaceuticals of tramadol, lidocaine and ofloxacin

Tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺)-Zirconia-Nafion composite modified glassy carbon disk electrode as a solid-state electrochemiluminescence (ECL) detector is successfully applied to an electrophoretic microchip system with a wall-jet configuration. Pharmaceuticals such as tramadol, lidocaine and ofloxacin were selected to characterize the performance of this microchip capillary electrophoresis (CE)-ECL detection system. Voltammetric and ECL behaviors of immobilized Ru(bpy)₃²⁺ were investigated in lidocaine system. Influences of the separation electric field to cyclic voltammograms (CVs) of the immobilized Ru(bpy)₃²⁺ were also investigated. Tramadol, lidocaine and ofloxacin can be baseline separated without any additives. The detection limits (S/N = 3) were 2.5 × 10⁻⁵ mol L⁻¹ for tramadol, 5.0 × 10⁻⁶ mol L⁻¹ for lidocaine, 1.0 × 10⁻⁵ mol L⁻¹ for ofloxacin under the sample injection of picoliters, and the linear ranges were from 5.0 × 10⁻⁵ to 2.5 × 10⁻³ mol L⁻¹ for tramadol, 1.0 × 10⁻⁵ to 1.0 × 10⁻³ mol L⁻¹ for lidocaine, and 1.0 × 10⁻⁵ to 2.5 × 10⁻³ mol L⁻¹ for ofloxacin, respectively.     

Electrochemiluminescent behaviors of alkaloids and tris(2,2'-bipyridine) ruthenium in organically modified silicate film

Electrogenerated chemiluminescences (ECLs) of alkaloids, such as berberine, trigonelline, allantoin and betaine, were studied in an aqueous alkaline buffer solution (pH 9.5), based on tris(2,2′-bipyridine)ruthenium(II) [Ru(bpy)₃²⁺] immobilized in organically modified silicates (ORMOSILs) film on a glassy carbon electrode (GCE). The immobilized Ru(bpy)₃²⁺ showed good electrochemical and photochemical activities. In a flow system, the eluted alkaloids were oxidized on the modified GCE, and reacted with immobilized Ru(bpy)₃²⁺ at the potential of +1.50 V (versus Ag/AgCl). The luminescence with λ_max 610 nm was caused by a reaction of electrolytically formed Ru(bpy)₃³⁺ with an oxidized amine group to generate Ru(bpy)₃^2+*. The determination limit was 5 × 10⁻⁶ mol L⁻¹, 8 × 10⁻⁶ mol L⁻¹, 2.0 × 10⁻⁵ mol L⁻¹ and 5.0 × 10⁻⁵ mol L⁻¹ for berberine, trigonelline, allantoin and betaine at S/N 3, respectively. In addition, the factors affecting the determination of the four alkaloids were also studied.     

Determination of brominated phenols in water samples by on-line coupled isotachophoresis with capillary zone electrophoresis

A method for determination of nine brominated phenols as environmental risk compounds was developed by on-line coupled capillary isotachophoresis and capillary zone electrophoresis (ITP–CZE). For ITP step, 1 × 10⁻² mol L⁻¹ hydrochloric acid with 3 × 10⁻² mol L⁻¹ ammediol pH 9.1 was used as the leading electrolyte, and 3 × 10⁻² mol L⁻¹ β-alanine with 2 × 10⁻² mol L⁻¹ sodium hydroxide pH 10.05 was used as the terminating electrolyte. As the background electrolyte for CZE separation, 2.5 × 10⁻² mol L⁻¹ β-alanine with 2.5 × 10⁻² mol L⁻¹ lysine pH 9.6 was used. All electrolytes contained 0.05% or 0.1% (m/v) hydroxyethylcellulose to suppress the electroosmotic flow. UV detection at wavelength 220 nm was used. Detection limits in order of tens of nmol L⁻¹ were achieved. Good repeatability of migration times (less than 0.33% RSD) and good repeatability of peak areas (less than 7.19% RSD) at concentration level 5 × 10⁻⁸ mol L⁻¹ were observed. Developed ITP–CZE method was applied to determination of brominated phenols in spiked tap and river water samples.     

Triethanolamine-capped CdSe quantum dots as fluorescent sensors for reciprocal recognition of mercury (II) and iodide in aqueous solution

Water-soluble luminescent CdSe quantum dots surface-modified with triethanolamine (TEA-CdSe-QDs) were prepared with high stability. The fluorescence of the TEA-CdSe-QDs was greatly quenched only when Hg²⁺ and I⁻ coexisted in the solution, whereas addition of either Hg²⁺ or I⁻ individually has no noticeable effect on the fluorescence emission. Such a unique quenching effect could be used for reciprocal recognition of mercury (II) ions and/or iodide anions in aqueous solution with rather high selectivity and sensitivity. The detection limits of Hg²⁺ or I⁻ ion were 1.9 × 10⁻⁷ mol L^-1 or 2.8 × 10⁻⁷ mol L⁻¹, respectively. The adequate experiments showed that iodine (I) anions could bridge between TEA-CdSe-QDs and Hg²⁺ to form a stable complex (QDs-I⁻-Hg²⁺) and the following effective electron transfer from the QDs to the Hg²⁺ could be responsible for the fluorescence quenching of QDs.     

A new resonance scattering spectral method for the determination of trace amounts of iodate with rhodamine 6G

Under the conditions of 0.04 mol L⁻¹ HCl-8.0 × 10⁻⁴ mol L⁻¹ KI, there is a fluorescence peak at 540 nm and a synchronous fluorescence peak at 540 nm for rhodamine 6G (RhG). When there is IO₃⁻, it reacts with exceed I⁻ to form I₃⁻. And I₃⁻ and RhG combine into ion association particles. The particles exhibit three resonance scattering peaks at 320, 400 and 595 nm. And there is fluorescence quenching at 540 nm. Iodine concentration is proportional to the intensity of the resonance scattering intensity at 400 nm in the range of 1.0-20 × 10⁻⁷ mol L⁻¹. And a new resonance scattering spectral (RSS) method has been described for the determination of IO₃⁻ in salt samples. The spectral results have been verified that the formation of (RhG-I₃)_n association particles and solid-liquid interfaces are the main factor that cause the fluorescence quenching and resonance scattering effects.     

Ultrasensitive determination of silver ion based on synchronous fluorescence spectroscopy with nanoparticles

Based on the characteristics of synchronous fluorescence spectroscopy (SFS), a new method with high sensitivity and selectivity was developed for rapid determination of silver ion with functional cadmium sulphide (CdS) nanoparticles as a fluorescence probe. When Δλ (λ_em − λ_ex) = 215 nm, maximum synchronous fluorescence is produced at 304 nm. Under optimal conditions, functional cadmium sulphide displayed a calibration response for silver ion over a wide concentration range from 0.8 × 10⁻¹⁰ to 1.5 × 10⁻⁸ mol L⁻¹. The limit of detection was 0.4 × 10⁻¹⁰ mol L⁻¹ and the relative standard deviation of seven replicate measurements for the lowest concentration (0.8 × 10⁻¹⁰ mol L⁻¹) was 2.8%. Compared with several fluorescence methods, the proposed method had a wider linear range and improved the sensitivity. Furthermore, the concentration dependence of the synchronous fluorescence intensity is effectively described by a Langmuir-type binding isotherm.     

Rapid simultaneous analysis of 1-hydroxypyrene, 2-hydroxyfluorene, 9-hydroxyphenanthrene, 1- and 2-naphthol in urine by first derivative synchronous fluorescence spectrometry using Tween-20 as a sensitizer

A novel method of first derivative synchronous fluorescence was developed for the rapid simultaneous analysis of trace 1-hydroxypyrene (1-OHP), 1-naphthol (1-NAP), 2-naphthol (2-NAP), 9-hydroxyphenanthrene (9-OHPe) and 2-hydroxyfluorene (2-OHFlu) in human urine. Only one single scan was needed for quantitative determination of five compounds simultaneously when Δλ = 10 nm was chosen. In the optimal experimental conditions, there was a linear relationship between the fluorescence intensity and the concentration of 1-OHP, 1-NAP, 2-NAP, 9-OHPe and 2-OHFlu in the range of 1.75 × 10⁻⁹ to 4.50 × 10⁻⁶ mol L⁻¹, 3.64 × 10⁻⁸ to 2.20 × 10⁻⁴ mol L⁻¹, 8.18 × 10⁻⁹ to 1.20 × 10⁻⁴ mol L⁻¹, 3.26 × 10⁻⁹ to 8.50 × 10⁻⁵ mol L⁻¹ and 4.88 × 10⁻⁹ to 5.50 × 10⁻⁶ mol L⁻¹, respectively. The limits of detection (LOD) were found to be 5.25 × 10⁻¹⁰ mol L⁻¹ for 1-OHP, 1.10 × 10⁻⁸ mol L⁻¹ for 1-NAP, 2.46 × 10⁻⁹ mol L⁻¹ for 2-NAP, 9.77 × 10⁻¹⁰ mol L⁻¹ for 9-OHPe and 1.46 × 10⁻⁹ mol L⁻¹ for 2-OHFlu. The proposed method is reliable, selective and sensitive, and has been used successfully in the determination of traces of 1-OHP, 1-NAP, 2-NAP, 9-OHPe and 2-OHFlu in human urine samples, whose results were in good agreement with those gained by the HPLC method.     

Construction of a new Cu2+ coated wire ion selective electrode based on 2-((2-(2-(2-(2-hydroxy-5-methoxybenzylidene amino)phenyl)disufanyl)phenylimino)methyl)-4-methoxyphenol Schiff base

In this article a new coated platinum Cu²⁺ ion selective electrode based on 2-((2-(2-(2-(2-hydroxy-5-methoxybenzylideneamino)phenyl)disufanyl)phenylimino) methyl)-4-methoxyphenol Schiff base (L₁) as a new ionophore is described. This sensor has a wide linear range of concentration (1.2 × 10⁻⁷-1.0 × 10⁻¹ mol L⁻¹) and a low detection limit of 9.8 × 10⁻⁸ mol L⁻¹of Cu(NO₃)₂. It has a Nernstian response with slope of 29.54 ± 1.62 mV decade⁻¹ and it is applicable in the pH range of 4.0-6.0 without any divergence in potentioal. The coated electrode has a short response time of approximately 9 s and is stable at least for 3.5 months. The electrode shows a good selectivity for Cu²⁺ ion toward a wide variety of metal ions. The proposed sensor was successfully applied for the determination of Cu²⁺ ion in different real and environmental samples and as indicator electrode for potentiometric titration of Cu²⁺ ion with EDTA.     

Bulk optode sensors for batch and flow-through determinations of lead ion in water samples

A sensitive optode consisting of highly lead-selective ionophore (Lead IV), proton-selective chromoionophore (ETH 5294) and lipophilic anionic sites (KTpClPB) in plasticized polyvinyl chloride (PVC) membrane was fabricated. The optode membranes were used for determination of Pb²⁺ by absorption spectrophotometry in batch and flow-through systems. The influence parameters such as pH, type of buffer solution, response time and concentration of regenerating solution were optimized. The membrane responded to Pb²⁺ by changing its color from blue to pinkish purple in Tris buffer containing different concentration of Pb²⁺ at pH 7.0. The optode provided the response range of 3.16 × 10⁻⁸ to 5.00 × 10⁻⁵ mol L⁻¹ Pb²⁺ with the detection limit of 2.49 × 10⁻⁸ mol L⁻¹ in the batch system within the response time of 30 min. The dynamic range of 1.26 × 10⁻⁸ to 3.16 × 10⁻⁵ mol L⁻¹ Pb²⁺ with detection limit of 8.97 × 10⁻⁹ mol L⁻¹ were obtained in the flow-through system within the response time of 15 min. Moreover, the proposed optode sensors showed good selectivity towards Pb²⁺ over Na⁺, K⁺, Mg²⁺, Cd²⁺, Hg²⁺ and Ag⁺. It was successfully applied to determine Pb²⁺ in real water samples and the results were compared with well-established inductively coupled plasma optical emission spectrometry (ICP-OES). No significant different value (t_critical = 4.30 > t_exp = 1.00-3.42, n = 3 at 95% of confidence level) was found.     

Study of the influence of silver nanoparticles on the second-order scattering and the fluorescence of the complexes of Tb(III) with quinolones and determination of the quinolones

Quinolones (Qs) can form the complex with Tb(III) ion, and the intramolecular energy transfer from Qs to Tb(III) takes place when excited. And thus the characteristic fluorescence of Tb(III) ion was enhanced and the maximum fluorescence peak locates at 545 nm. The second-order scattering (SOS) peak at 545 nm also appears for the Tb(III)-Qs complexes with the exciting wavelength of 274 nm. When the silver nanoparticles were added to the Tb(III)-Qs system, the luminescence intensity at 545 nm greatly increased. And the relative intensity is proportional to the amount of Qs. Based on this phenomenon, a novel method for determination of quinolones has been developed by using a common spectrofluorometer to measure the intensity of fluorescence and SOS. The luminescence intensity is greatly enhanced by silver nanoparticles in the pH range 5.5-6.2. The calibration graphs for pipemidic acid (PPA) and lomefloxacin (LMFX) are linear in the range 2.0 × 10⁻¹⁰ to 1.0 × 10⁻⁵ and 1.0 × 10⁻⁹ to 1.0 × 10⁻⁵ mol L⁻¹, respectively. The limits of detection are 4.7 × 10⁻¹¹ mol L⁻¹ for PPA and 1.1 × 10⁻¹⁰ mol L⁻¹ for LMFX. The method was applied satisfactorily to the determination of the two quinolones (Qs) in tablet, capsule, urine and serum samples. The experimental results showed that it is the certain size and certain concentration of silver nanoparticles that can greatly enhance the fluorescence -SOS intensity.     

One-step synthesis and applications of fluorescent Cu nanoclusters stabilized by l-cysteine in aqueous solution

Herein, an innovative and simple strategy for synthesizing high fluorescent Cu nanoclusters was successfully established while l-cysteine played a role as the stabilizer. Meaningfully, the current Cu nanoclusters together with a quantum yield of 14.3% were prepared in aqueous solution, indicating their extensive applications. Subsequently, the possible fluorescence mechanism was elucidated by fluorescence, UV–vis, HR-TEM, FTIR, XPS, and MS. Additionally, the CuNCs were employed for assaying Hg²⁺ on the basis of the interactions between Hg²⁺ and l-cysteine; thus facilitating the quenching of their fluorescence. The proposed analytical strategy permitted detections of Hg²⁺ in a linear range of 1.0 × 10⁻⁷ mol L⁻¹ × 10⁻³ mol L⁻¹, with a detection limit of 2.4 × 10⁻⁸ mol L⁻¹ at a signal-to-noise ratio of 3. Significantly, this CuNCs described here were further applied for coding and fluorescent staining, suggesting may broaden avenues toward diverse applications.     

Ultrasensitive fluorometric determination of hydrogen peroxide and glucose by using multiferroic BiFeO3 nanoparticles as a catalyst

BiFeO₃ magnetic nanoparticles (BFO MNPs) are used as a catalyst to develop an ultrasensitive method for the determination of H₂O₂. It is found that BFO MNPs can catalyze the decomposition of H₂O₂ to produce OH radicals, which in turn oxidize the weakly fluorescent benzoic acid to a strongly fluorescent hydroxylated product with a maximum emission at 405 nm. This makes it possible to sensitively quantify traces of H₂O₂. Under optimized conditions, the fluorescence intensity is observed to be well linearly correlated with H₂O₂ concentration from 2.0 × 10⁻⁸ to 2.0 × 10⁻⁵ mol L⁻¹ with a detection limit of 4.5 × 10⁻⁹ mol L⁻¹ (S/N = 3). In addition, a selective method for glucose determination is developed by using both glucose oxidase and BFO MNPs, which has a linear range for glucose concentration from 1.0 × 10⁻⁶ to 1.0 × 10⁻⁴ mol L⁻¹ with a detection limit of 5.0 × 10⁻⁷ mol L⁻¹. These new methods have been successfully applied for the determination of H₂O₂ in rainwater and glucose in human serum samples.     

Square wave voltammetric determination of nitrofurantoin in pharmaceutical formulations on highly boron-doped diamond electrodes at different boron-doping contents

The influence of the boron-doping levels in boron-doped diamond film electrodes on the electrochemical response of nitrofurantoin (NFT) and the development of an electroanalytical procedure for NFT determination were investigated. The investigations were carried out using the techniques of cyclic voltammetry and square wave voltammetry on diamond film electrodes with different boron-doping levels (i.e., 5000, 10,000 and 20,000 mg L⁻¹). The level of boron-doping in the diamond film electrodes influenced the electrochemical reduction of NFT. The appropriate cyclic voltammetric response of NFT was obtained with Britton-Robinson buffer at pH 4 and for diamond films doped with 10,000 and 20,000 mg L⁻¹ of boron. These two films were selected for the development of the electroanalytical procedure. The use of square wave voltammetry with the optimized parameters demonstrated a good linear relationship between the peak current and the NFT concentration for a wide range of concentration. The lower limit of detection for the electrodes doped with 10,000 and 20,000 mg L⁻¹ of boron were 2.69 × 10⁻⁸ mol L⁻¹ (6.40 μg L⁻¹) and 8.15 × 10⁻⁹ mol L⁻¹ (1.94 μg L⁻¹), respectively, while the lower limits of quantification were 8.96 × 10⁻⁸ mol L⁻¹ (21.33 μg L⁻¹) and 2.72 × 10⁻⁸ mol L⁻¹ (6.47 μg L⁻¹), respectively. The applicability of the proposed procedure was tested using a commercial pharmaceutical formulation of NFT, and the results were compared with the procedure recommended by the British Pharmacopeia. The proposed procedure was sensitive, accurate and precise for analysis of NFT and did not require complex preparations or renovations of the electrode surface. This presents the advantage of eliminating mercury waste and minimizing the adsorptive problems related to the use of other electrodic solid surfaces.     

Electrospinning preparation and drug delivery properties of Eu/Tb doped mesoporous bioactive glass nanofibers

Luminescent Eu³⁺/Tb³⁺ doped mesoporous bioactive glass nanofibers (MBGNFs) with average diameter of 100-120 nm were fabricated by electrospinning method. Pluronic P123 and N-cetyltrimethylammonium bromide (CTAB) were used as co-surfactants to generate porous structure of the nanofibers. N₂ adsorption-desorption measurement reveals that the MBGNF:Eu³⁺ have a surface area of 188 m² g⁻¹, a pore volume of 0.246 cm³ g⁻¹ and average pore size of 4.17 nm, and the MBGNF:Tb³⁺ have a surface area of 171 m² g⁻¹, a pore volume of 0.186 cm³ g⁻¹ and average pore size of 3.65 nm. Photoluminescence measurements reveal that the MBGNF:Eu³⁺ show strong red emission dominated by the ⁵D₀ → ⁷F₂ transition of Eu³⁺ at 614 nm with a lifetime of 1.356 ms, and MBGNF:Tb³⁺ show strong green emission dominated by the ⁵D₄ → ⁷F₅ transition of Tb³⁺ at 544 nm with a lifetime of 1.982 ms. The biocompatibility tests on L929 fibroblast cells using MTT assay reveal low cytotoxicity of MBGNF. These luminescent nanofibers show sustained release properties for ibuprofen (IBU) in vitro. The emission intensities of Eu³⁺ in the drug delivery system vary with the released amount of IBU, thus making the drug release be easily tracked and monitored by the change of the luminescence intensity.     

Highly selective electrogenerated chemiluminescence (ECL) for sulfide ion determination at multi-wall carbon nanotubes-modified graphite electrode

In the present work, a novel method for immobilization of carbon nanotubes (CNTs) on the surface of graphite electrode was proposed. We further found that superoxide ion was electrogenerated on this CNTs-modified electrode, which can react with sulfide ion combing with a weak but fast electrogenerated chemiluminescence (ECL) emission, and this weak ECL signal could be enhanced by the oxidative products of rhodamine B. In addition, the rate constant of this electrochemical reaction k⁰ was investigated and confirmed that the speed of electrogenerating superoxide ion was in accordance with the subsequent fast CL reaction. Thus, the fast CL reaction of superoxide ion with target brought in the possibility of high selectivity based on time-resolved, relative to other interferences. Based on these findings, an excellently selective and highly sensitive ECL method for sulfide ion was developed. Under the optimum conditions, the enhancing ECL signals were linear with the sulfide ion concentration in the range from 6.0 × 10⁻¹⁰ to 1.0 × 10⁻⁸ mol L⁻¹, and a 2.0 × 10⁻¹⁰ mol L⁻¹ detection limits (3σ) was achieved. In addition, the proposed method was successfully used to detect sulfide ion in environmental water samples.