Electrochemiluminescence from tris(2,2′-bipyridyl)ruthenium(II)-graphene-Nafion modified electrode

An electrochemiluminescence (ECL) sensor based on Ru(bpy)₃²⁺-graphene-Nafion composite film was developed. The graphene sheet was produced by chemical conversion of graphite, and was characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM), and Raman spectroscopy. The introduction of conductive graphene into Nafion not only greatly facilitates the electron transfer of Ru(bpy)₃²⁺, but also dramatically improves the long-term stability of the sensor by inhibiting the migration of Ru(bpy)₃²⁺ into the electrochemically inactive hydrophobic region of Nafion. The ECL sensor gives a good linear range over 1 × 10⁻⁷ to 1 × 10⁻⁴ M with a detection limit of 50 nM towards the determination of tripropylamine (TPA), comparable to that obtained by Nafion-CNT. The ECL sensor keeps over 80% and 85% activity towards 0.1 mM TPA after being stored in air and in 0.1 M pH 7.5 phosphate buffer solution (PBS) for a month, respectively. The long-term stability of the modified electrode is better than electrodes modified with Nafion, Nafion-silica, Nafion-titania, or sol-gel films containing Ru(bpy)₃²⁺. Furthermore, the ECL sensor was successfully applied to the selective and sensitive determination of oxalate in urine samples.     

Silver(I) ions-enhanced electrochemiluminescence of tris(2,2-bipyridyl)ruthenium(II)

In this paper, we demonstrate an electrochemiluminescence (ECL) enhancement of tris(2,2-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) by the addition of silver(I) ions. The maximum enhancement factor of about 5 was obtained on a glassy carbon electrode in the absence of co-reactant. The enhancement of ECL intensity was possibly attributed to the unique catalytic activity of Ag⁺ for reactions between Ru(bpy)₃³⁺ with OH. The higher enhancement was observed in phosphate buffer solutions compared with that from borate buffer solutions. This resulted from the fact that formation of nanoparticles with large surface area in the phosphate buffer solution exhibited high catalytic activity. The amount of Ag⁺, solution pH and working electrode materials played important roles for the ECL enhancement. We also studied the effects of Ag⁺ on Ru(bpy)₃²⁺/tripropylamine and Ru(bpy)₃²⁺/C₂O₄²⁻ ECL systems.     

3D nanostructured Ni(OH)2 microspheres as an efficient immobilization matrix of Ru(bpy)3 for high-performance electrochemiluminescence sensor

The electrochemistry and electrochemiluminescence (ECL) of novel three-dimensional nanostructured Ru(bpy)₃²⁺/Ni(OH)₂ microspheres were investigated for the first time. The negatively charged porous Ni(OH)₂ microspheres composed of Ni(OH)₂ nanowires were specifically designed to interact with Ru(bpy)₃²⁺. The large surface area and porous structure of Ni(OH)₂ microspheres enhance loading of Ru(bpy)₃²⁺ and mass transport of the model analyte, tripropylamine (TPA). Excellent ECL performance of the presented sensor was achieved including good stability and wide linear range from 7.7 × 10⁻¹⁰ to 3.8 × 10⁻³ M with the detection limit of 2.6 × 10⁻¹⁰ M to TPA.     

Determination of adrenaline by using inhibited Ru(bpy)3 electrochemiluminescence

Adrenaline was found to inhibit strongly the electrochemiluminescence (ECL) from the Ru(bpy)₃²⁺/tripropylamine system when a working Pt electrode was maintained at 1.05 V (versus Ag/AgCl) in pH 8.0 phosphate buffer. On this basis, a flow injection (FI) procedure with inhibited electrochemiluminescence detection has been developed for determination of adrenaline. The method exhibited a good reproducibility, sensitivity, and stability with a detection limit (signal-to-noise ratio = 3) of 7.0×10⁻⁹ mol l⁻¹ and dynamic concentration range of 2×10⁻⁸ to 1×10⁻⁴ mol l⁻¹. The relative standard deviation was 2.2% for 1.0×10⁻⁶ mol l⁻¹ adrenaline (n=11). The method was successfully applied to the determination of adrenaline in pharmaceutical samples. Moreover, ECL emission spectra, UV-Vis absorption spectra and cyclic voltammograms of Ru(bpy)₃²⁺/tripropylamine/adrenaline were studied. The inhibition mechanism has been proposed as the interaction of electrogenerated Ru(bpy)₃^2+* and the o-benzoquinone derivatives, adrenochrome and adrenalinequinone, at the electrode surface.     

Immobilization of tris(1,10-phenanthroline)ruthenium with graphene oxide for electrochemiluminescent analysis

Electrochemiluminescence (ECL) of ruthenium complexes has broad applications and the immobilization of Ru(bpy)₃²⁺ has received extensive attention. In comparison with Ru(bpy)₃²⁺, Ru(phen)₃²⁺ can be immobilized more easily because of its better adsorbability. In this study, immobilization of Ru(phen)₃²⁺ for ECL analysis has been demonstrated for the first time by using graphene oxide (GO) as an immobilization matrix. The immobilization of Ru(phen)₃²⁺ is achieved easily by mixing Ru(phen)₃²⁺ with GO without using any ion exchange polymer or covalent method. The strong binding of Ru(phen)₃²⁺ with GO is attributed to both the π–π stacking interaction and the electrostatic interaction. The Ru(phen)₃²⁺/GO modified electrode was characterized by using tripropylamine (TPA) as the coreactant. The linear range of TPA is from 3 × 10⁻⁷ to 3 × 10⁻² mol L⁻¹ with the detection limit of 3 × 10⁻⁷ mol L⁻¹. The ECL sensor demonstrates outstanding long-term stability. After the storage in the ambient environment for 90 days, the ECL response remains comparable with its original signal.     

Polyelectrolyte-based electrochemiluminescence enhancement for Ru(bpy)3 loaded by SiO2 nanoparticle carrier and its high sensitive immunoassay

In this paper the strong electrochemiluminescence (ECL) nanoparticles have been prepared based on the anionic polyelectrolyte sodium polyacrylate (PAA)-ECL enhancement for Ru(bpy)₃²⁺, which were loaded by the carrier of SiO₂ nanoparticle. There were two kinds of Ru(bpy)₃²⁺ for the as-prepared nanoparticles, the doped one and the exchanged one. The former was loaded inside the ECL nanoparticles by doping, in a form of ion-pair macromolecules PAA–Ru(bpy)₃²⁺. The corresponding ECL was enhanced about 2 times owing to the doping increase of Ru(bpy)₃²⁺. The latter was loaded on the PAA-doped Nafion membrane by ion exchange. The corresponding ECL was enhanced about 3 times owing to the ion-exchanging increase of Ru(bpy)₃²⁺. At the same time, ECL intensity of the doped-inside Ru(bpy)₃²⁺ was further enhanced 13 times because polyelectrolyte PAA in the doped membrane could obviously enhance electron transfer between the doped Ru(bpy)₃²⁺ and the working electrode. Furthermore, based on hydrophobic regions of the doped membrane antibody labeling could be easily realized by the as-prepared nanoparticles and then a high sensitive ECL immunoassay for HBsAg was developed. The linear range was between 1.0 and 100 pg mL⁻¹ (R² = 0.9912). The detection limit could be as low as 0.11 pg mL⁻¹ (signal-to-noise ratio = 3).     

Electrogenerated chemiluminescence biosensor based on Ru(bpy)3(2+) and dehydrogenase immobilized in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) composite material

A new electrogenerated chemiluminescence biosensor was fabricated by immobilizing ECL reagent Ru(bpy)₃²⁺ and alcohol dehydrogenase in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) (PSS) organically modified composite material. The component PSS was used to immobilize ECL reagent Ru(bpy)₃²⁺ by ion-exchange, while the addition of chitosan was to prevent the cracking of conventional sol-gel-derived glasses and provide biocompatible microenvironment for alcohol dehydrogenase. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate and it was much simpler than previous double-layer design. The detection limit was 9.3 × 10⁻⁶ M for alcohol (S/N = 3) with a linear range from 2.79 × 10⁻⁵ to 5.78 × 10⁻² M. With ECL detection, the biosensor exhibited wide linear range, high sensitivity and good stability.     

One-step immobilization of tris(2,2'-bipyridyl)ruthenium(II) via vapor-surface sol-gel deposition towards solid-state electrochemiluminescence detection

A novel method for immobilization of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃Cl₂) on electrode surfaces based on the vapor-surface sol-gel deposition strategy is first demonstrated in this paper. Ru(bpy)₃Cl₂ immobilized sol-gel (Ru(bpy)₃Cl₂/sol-gel) films were characterized by UV-vis spectroscopy and field-emitted scanning electron microscopy (FE-SEM). These results showed that Ru(bpy)₃Cl₂ was successfully incorporated into the silica sol-gel film. It was found that many irregular Ru(bpy)₃Cl₂/sol-gel clusters were formed on surfaces through one deposition and thick sol-gel films were observed after further deposition. Electrochemical properties and electrochemiluminescence (ECL) behaviors of Ru(bpy)₃Cl₂/sol-gel films could be easily adjusted by deposition numbers and time. At last, the Ru(bpy)₃Cl₂/sol-gel film modified electrode was used for solid-state ECL detection of tripropylamine. The linear range was from 5.8 × 10⁻⁸ to 2.4 × 10⁻⁴ M with the detection limit of 5 nM, which was three orders of magnitude lower than that from pure Nafion-modified electrodes. The ECL sensor also exhibited high stability, and still remained 92% response after being stored in air for 35 days. This method for immobilization of Ru(bpy)₃Cl₂ is simple, convenient and low-cost relative to others, so it shows promising applications in solid-state ECL detection.     

Multi-walled carbon nanotubes and Ru(bpy)3/nano-Au nano-sphere as efficient matrixes for a novel solid-state electrochemiluminescence sensor

An effective method for immobilization of Ru(bpy)₃²⁺ on glassy carbon electrode surface (GCE) is developed for the preparation of a novel electrochemiluminescence sensor. First of all, the positively charged Ru(bpy)₃²⁺ is modified on the surface of negatively charged gold nanoparticles (nano-Au) via the electrostatic interactions to obtain the Ru(bpy)₃²⁺/nano-Au nano-sphere (abbreviate as Ru-AuNPs). Subsequently, the large amount of Ru-AuNPs are immobilized on the multi-wall carbon nanotubes (MWCNTs)-Nafion homogeneous composite coated GCE by dual interaction: firstly, the Nafion, a kind of typical cation-exchange membrane, can absorb the Ru-AuNPs as the enrichment of cation Ru(bpy)₃²⁺ on the Ru-AuNPs surface; secondly, the employment of carboxylic MWCNTs in the Nafion film can also chemosorb the Ru(bpy)₃²⁺ cation on the Ru-AuNPs surface to increase the carrier content. At the same time, the experiment confirms that the enhancement of the ECL intensity on the sensor is attributed to following reasons. One hand, the employment of MWCNTs in the Nafion film enlarged the electro-active surface areas to benefit the contact between the signal probe on the composite film and coreactant used as reinforcing agent. On the other hand, the nano-materials of MWCNTs and nano-Au also improve the conductivity of the assembled film to increase the quantity of excited state of Ru(bpy)₃²⁺ in the unit time under the electrochemical condition and finally cause better properties in luminescence. In the experiment, the influence of the coreactant tripropylamine (TPA) on proposed ECL sensor is investigated. The logarithm of ECL intensity is proportional to the logarithm of TPA concentration on the range of 4 × 10⁻¹⁰ M to 2.8 × 10⁻⁶ M and 2.8 × 10⁻⁶ M to 0.71 × 10⁻³ M. After optimizing these conditions, the ECL sensor with TPA as coreactant is employed to detect a kind of alkaloid medicine, Matrine, for evaluating the practical application in the medicine analysis. The present sensor with TPA as coreactant shows the good response to the medicine concentration of the Matrine from 2.0 × 10⁻⁶ M to 6.0 × 10⁻³ M, which is used to detect the Matrine concentration in the Matrine injection.     

Electrochemiluminescence from Ru(bpy)3 immobilized in poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)-poly(vinyl alcohol) composite films

Electrochemical behavior and electrogenerated chemiluminescence (ECL) of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) immobilized in poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)-poly(vinyl alcohol) (PEDOT/PSS-PVA) composite films via ion-exchange have been investigated with tripropylamine (TPA) as the co-reactant at a glassy carbon electrode. The immobilized Ru(bpy)₃²⁺ performed a surface-controlled electrode reaction. The Ru(bpy)₃²⁺ modified electrode showed a fast ECL response to TPA, and was used for the ECL detection of TPA with high sensitivity. The ECL intensity was linearly related to concentrations of TPA over the range from 0.50 μmol L⁻¹ to 0.80 mmol L⁻¹, and the detection limit was 0.10 μmol L⁻¹ (S/N = 3). The as-prepared electrode exhibited good precision and long-term stability for TPA determination.     

Determination of itopride hydrochloride by high-performance liquid chromatography with Ru(bpy)3 electrogenerated chemiluminescence detection

In this work, a stable electrogenerated chemiluminescence (ECL) detector was developed. The detector was prepared by packing cation-exchanged resin particles in a glass tube, followed by inserting Pt wires (working electrode) in this tube and sealing. The leakage of Ru(bpy)₃²⁺ can be compensated by adding a small amount of Ru(bpy)₃²⁺ into solution phase. Coupled with high-performance liquid chromatography separation, the detector has been used for determination of itopride hydrochloride in human serum. Under the optimal conditions, the ECL intensity has a linear relationship with the concentration of itopride hydrochloride in the range of 1.0 × 10⁻⁸ g mL⁻¹ to 1.0 × 10⁻⁶ g mL⁻¹ and the detection limit was 3 × 10⁻⁹ g mL⁻¹ (S/N = 3). The as-prepared ECL detector displayed good sensitivity and stability.     

Tris(2,2'-bipyridyl)ruthenium(II) electrochemiluminescence sensor based on carbon nanotube/organically modified silicate films

In this paper, a novel electrochemiluminescence (ECL) sensor was constructed to determine herring sperm (HS) double-stranded (ds) DNA. Tetramethoxysilane and dimethyldimethoxysilane were selected as co-precursors to form an organically modified silicate (ORMOSIL) film for the immobilization of multiwall carbon nanotubes (MWNTs) wrapped by poly(p-styrenesulfonate) (PSS), and then Tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) was successfully immobilized on a glassy carbon electrode via ion-association. PSS was employed to increase the conductivity of the ORMOSIL film and disperse the cut MWNTs, which were cut and shortened in a mixture of concentrated sulfuric and nitric acids, in the film. It was found that MWNTs could adsorb Ru(bpy)₃²⁺ and acted as conducting pathways to connect Ru(bpy)₃²⁺ sites to the electrode. MWNTs also played a key role as materials for the mechanical and thermal properties. The ECL performance of this modified electrode was evaluated in a flow injection analysis (FIA) system, and the detection limit (S/N = 3) for HS ds-DNA was 2.0 × 10⁻⁷ g mL⁻¹ with a linear range from 1.34 × 10⁻⁶ to 6.67 × 10⁻⁴ g mL⁻¹ (R² = 0.9876). In addition, the ECL sensor presented excellent characteristics in terms of stability, reproducibility and application life.     

Disposable biosensor based on cathodic electrochemiluminescence of tris(2,2-bipyridine)ruthenium(II) for uric acid determination

A new method for uric acid (UA) determination based on the quenching of the cathodic ECL of the tris(2,2-bipyridine)ruthenium(II)–uricase system is described. The biosensor is based on a double-layer design containing first tris(2,2-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) electrochemically immobilized on graphite screen-printed cells and uricase in chitosan as a second layer. The uric acid biosensing is based on the ECL quenching produced by uric acid over the cathodic ECL caused by immobilized Ru(bpy)₃²⁺ in the presence of uricase. The use of a −1.1 V pulse for 1 s with a dwelling time of 10 s makes it possible to estimate the initial enzymatic rate, which is used as the analytical signal. The Stern–Volmer type calibration function shows a dynamic range from 1.0 × 10⁻⁵ to 1.0 × 10⁻³ M with a limit of detection of 3.1 × 10⁻⁶ M and an accuracy of 13.6% (1.0 × 10⁻⁴ M, n = 5) as relative standard deviation. Satisfactory results were obtained for urine samples, creating an affordable alternative for uric acid determination.     

Determination of noradrenaline and dopamine in pharmaceutical injection samples by inhibition flow injection electrochemiluminescence of ruthenium complexes

Two maximal potential-resolved flow injection-electrochemiluminescent (FI-ECL) peaks were observed for Ru(bpy)₃²⁺/TPrA system at 0.90 and 1.05 V, and for Ru(phen)₃²⁺/TPrA at 1.01 and 1.25 V (vs. Ag/AgCl) in pH 8.0 phosphate buffer solutions. Sensitive ECL inhibition effects were observed in the presence of noradrenaline and dopamine for both of these systems. Therefore, an FI-ECL inhibition method for determination of noradrenaline and dopamine has been developed. Under optimal conditions, linear responses between logarithm of ECL intensity changes and logarithm of sample concentration were found for noradrenaline in the linear range (LR) of 4×10⁻⁸-1×10⁻⁵ mol l⁻¹ with theoretical detection limit (DL) of 2.5×10⁻⁸ mol l⁻¹ for Ru(bpy)₃²⁺/TPrA system, and in LR of 2×10⁻⁸-2×10⁻⁵ mol l⁻¹ with DL of 7.1×10⁻⁹ mol l⁻¹ for Ru(phen)₃²⁺/TPrA system; and for dopamine in LR of 8×10⁻⁸-2×10⁻⁵ mol l⁻¹ with DL of 5.2×10⁻⁸ mol l⁻¹ for Ru(bpy)₃²⁺/TPrA system, in LR of 4×10⁻⁸-2×10⁻⁵ mol l⁻¹ with DL of 1.5×10⁻⁸ mol l⁻¹ for Ru(phen)₃²⁺/TPrA system. It was applied for determination of commercial pharmaceutical injection samples with satisfied results. The mechanism of the inhibition effects was proposed in the preliminary way.     

Development of an ultrasensitive electrochemiluminescence inhibition method for the determination of tetracyclines

An electrochemiluminescence (ECL) inhibition method is developed for quantitative determination of four tetracyclines (TCs) in honey samples, including tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC) and doxycycline (DC). It was found that the four TCs strongly inhibited the ECL signal of the Ru(bpy)₃²⁺/DBAE system. Based on the ECL signal changes, a simple and ultrasensitive detection method for TCs was thus established. The optimum experimental conditions including the scan mode and scan rate of the applied potential, the type of the buffer solution and its pH, and the concentration of Ru(bpy)₃²⁺ and DBAE for the ECL inhibition method, were investigated in detail. Under the optimized conditions, the quenched ECL intensity versus the logarithm of the concentration of TCs is in good linear relationship over a concentration range from 4.0 × 10⁻¹¹ to 4.0 × 10⁻⁹ g mL⁻¹. The detection limits were found to be 2.0 × 10⁻¹² g mL⁻¹. The results obtained by the proposed ECL system, in terms of sensitivity, were much better than those of previously reported methods. In addition, the method was applied successfully to determine the total residuals of the four TCs in honey samples. The relative standard deviations were found in a range of 4.9–14.3%, and the recoveries were obtained from 87.5% to 115.0%. A possible mechanism for the quenching effects of Ru(bpy)₃²⁺/DBAE system was also proposed.     

A novel solid-state electrochemiluminescence detector for capillary electrophoresis based on tris(2,2'-bipyridyl)ruthenium(II) immobilized in Nafion/PTC-NH2 composite film

A new electrochemiluminescence (ECL) detector for capillary electrophoresis (CE) based on tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) immobilized in Nafion/PTC-NH₂ (an ammonolysis product of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA)) composite film was presented for the first time. The Nafion/PTC-NH₂ composite film could effectively immobilize tris(2,2′-bipyridyl)ruthenium(II) via ion-exchange and electrostatic interaction. Cyclic voltammetric and ECL behavior of Nafion/PTC-NH₂/Ru composite film was investigated compared to Nafion/Ru composite. The Nafion/PTC-NH₂/Ru composite film exhibited good ECL stability and simple operability. Then the CE with solid-state ECL detector system was successfully used to detect sophora - a quinolizidine type - alkaloids as sophoridine (SR) and matrine (MT). The CE-ECL parameters that affected separation and detection were optimized. Under the optimized conditions, the linear range was from 2.5 × 10⁻⁸ to 2 × 10⁻⁶ mol/L for SR, 1.0 × 10⁻⁸ to 1.0 × 10⁻⁶ mol/L for MT. The detection limit (S/N = 3) was estimated to be 5 × 10⁻⁹ and 10⁻⁹ mol/L for SR and MT, respectively. It was shown that the CE coupling with solid-state ECL detector system exhibited satisfying sensitivity of analysis.     

Solid-state electrochemiluminescence sensor through the electrodeposition of Ru(bpy)3/AuNPs/chitosan composite film onto electrode

Tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) has been successfully immobilized onto electrode through the electrodeposition of Ru(bpy)₃²⁺/AuNPs/chitosan composite film. In the experiments, chitosan solution was first mixed with Au nanoparticles (AuNPs) and Ru(bpy)₃²⁺. Then, during chronopotentiometry experiments in this mixed solution, a porous 3D network structured film containing Ru(bpy)₃²⁺, AuNPs and chitosan has been electrodeposited onto cathode due to the deposition of chitosan when pH value is over its pK_a (6.3). The applied current density is crucial to the film thickness and the amount of the entrapped Ru(bpy)₃²⁺. Additionally, these doping Ru(bpy)₃²⁺ in the composite film maintained their intrinsic electrochemical and electrochemiluminescence activities. Consequently, this Ru(bpy)₃²⁺/AuNPs/chitosan modified electrode has been used in ECL to detect tripropylamine, and the detection limit was 5 × 10⁻¹⁰ M.     

Mechanism study on inorganic oxidants induced inhibition of Ru(bpy)₃²+ electrochemiluminescence and its application for sensitive determination of some inorganic oxidants

Inhibited Ru(bpy)₃²⁺ electrochemiluminescence by inorganic oxidants is investigated. Results showed that a number of inorganic oxidants can quench the ECL of Ru(bpy)₃²⁺/tri-n-propylamine (TPrA) system, and the logarithm of the decrease in ECL intensity (ΔI) was proportional to the logarithm of analyte concentrations. Based on which, a sensitive approach for detection of these inorganic oxidants was established, e.g. the log-log plots of ΔI versus the concentration of MnO₄⁻, Cr₂O₇²⁻ and Fe(CN)₆³⁻ are linear in the range of 1 × 10⁻⁷ to 3 × 10⁻⁴ M for MnO₄⁻ and Cr₂O₇²⁻, and 1 × 10⁻⁷ to 1 × 10⁻⁴ M for Fe(CN)₆³⁻, with the limit of detection (LOD) of 8.0 × 10⁻⁸ M, 2 × 10⁻⁸ M, and 1 × 10⁻⁸ M, respectively. A series of experiments such as a comparison of the inhibitory effect of different compounds on Ru(bpy)₃²⁺/TPrA ECL, ECL emission spectra, UV-Vis absorption spectra etc. were investigated in order to discover how these inorganic analytes quench the ECL of Ru(bpy)₃²⁺/TPrA system. A mechanism based on consumption of TPrA intermediate (TPrA^·) by inorganic oxidants was proposed.     

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.     

Effects of Divalent Metal Ions on Electrochemiluminescence Sensor with Ru(bpy)32+ Immobilized in Eastman‐AQ Membrane

Different effects of divalent metal ions on electrochemiluminescence (ECL) sensor with Ru(bpy)₃²⁺ immobilized in Eastman‐AQ membrane were investigated. Mg²⁺, Ca²⁺ and Fe²⁺ can elevate the ECL of Ru(bpy)₃²⁺/proline; while metal ions that underwent redox reactions on the electrode such as Mn²⁺ and Co²⁺ presented intensive quenching effects on Ru(bpy)₃²⁺ ECL. Also, the quenching effect of Mn²⁺ on the ECL sensor with Ru(bpy)₃²⁺ immobilized in Eastman‐AQ membrane enhanced to about 30‐folds compared with the case that Ru(bpy)₃²⁺ was dissolved in phosphate buffer, and the enhanced quenching effects of Mn²⁺ were studied.