Electrochemiluminescent behavior of allopurinol in the presence of Ru(bpy)(3)(2+)

The electrochemiluminescent (ECL) response of allopurinol was studied in aqueous media over a wide pH range (pH 2–13) using flow injection (FI) analysis. It was revealed that allopurinol itself had no ECL activity, but could greatly enhance the ECL of Ru(bpy)₃²⁺ in alkaline media giving rise to a sensitive FI-ECL response. The effects of experimental conditions including the mode of applied voltage signal, the potential of working electrode, pH value, the flow rate of carrier solution, and the concentration of Ru(bpy)₃²⁺ and allopurinol on the ECL intensity were investigated in detail. The most sensitive FI-ECL response of allopurinol was found at pH 12.0, where the FIA-ECL intensity showed a linear relationship with concentration of allopurinol in the range 1 × 10⁻⁸ mol L⁻¹ to 5 × 10⁻⁷ mol L⁻¹, and the detection limit was 5 × 10⁻⁹ mol L⁻¹.     

Capillary electrophoresis with electrochemiluminescence detection of procyclidine in human urine pretreated by ion-exchange cartridge

This paper describe a Ru(bpy)₃²⁺ based electrochemiluminescence (ECL) method to detect procyclidine in human urine following separation by capillary electrophoresis (CE). An ECL detection cell was designed for post-column addition of Ru(bpy)₃²⁺. Parameters affecting separation and detection were optimized, leading to a detection limit of 1×10⁻⁹ mol/l in an on-capillary stacking mode. For application in urine, a cartridge packed with slightly acidic cation-exchange resin was used to eliminate the matrix effects of urine and improve the detection sensitivity. Extraction recovery was nearly 90%.     

Determination of fenoterol and salbutamol in pharmaceutical formulations by electrogenerated chemiluminescence

Fenoterol and salbutamol were determined by electrogenerated chemiluminescence (ECL) coupled with flow injection analysis (FIA), using Ru(bpy)₃²⁺ as the luminescent substance. Fenoterol and salbutamol oxidize together with the ruthenium 2,2-bipyridyl at a platinum electrode, which leads to an increase in the luminescent intensity, and this increase is proportional to the analyte concentration. For fenoterol a linear calibration curve within the range from 1.0 × 10⁻⁵ to 1.0 × 10⁻⁴ mol l⁻¹ was obtained with a correlation coefficient of 0.998 (n = 5) and for salbutamol the linear analytical curve was also obtained in this range with a correlation coefficient of 0.995 (n = 5). The relative standard deviation was estimated as ≤2.5% for 3 × 10⁻⁵ mol l⁻¹ for fenoterol solution and as ≤1.3% for 5.0 × 10⁻⁵ mol l⁻¹ salbutamol solution for 15 successive injections. The limit of detection for fenoterol was 2.4 × 10⁻⁷ mol l⁻¹ and for salbutamol was 4.0 × 10⁻⁷ mol l⁻¹. Fenoterol and salbutamol were successfully determined in drug tablets and the soluble components of the matrix did not interfere in the luminescent emission. The results obtained using the luminescent methodology were not statistically different from those obtained by UV-spectrophotometry at 95% confidence level.     

Characterization of the low-oxidation-potential electrogenerated chemiluminescence of tris(2,2′-bipyridine)ruthenium(II) with tri-n-propylamine as coreactant

The electrogenerated chemiluminescence (ECL) of the Ru(bpy)₃²⁺ (bpy, 2,2′-bipyridine)/tri-n-propylamine (TPrA) system can be produced at an oxidation-potential well before the oxidation of Ru(bpy)₃²⁺. Here, we describe the unique features of the low-oxidation-potential (LOP) ECL. The LOP ECL exhibited strong dependence on solution pH with the maximum emission at pH  7.7. Compared with the conventional ECL, the LOP ECL was much more significantly diminished at high pH (>10), probably due to the short lifetime of TPrA cation radical which is a crucial intermediate for the LOP emission. It was also found that the preceding deprotonation step played an important role in TPrA oxidation at neutral pH and would remarkably influence the emission intensity. As excess intermediate radicals were produced upon rapid TPrA oxidation, only 5 mM TPrA was needed to achieve the maximum LOP ECL intensity in detecting trace Ru(bpy)₃²⁺ (<1 μM) and the LOP ECL response to Ru(bpy)₃²⁺ concentration was linear. Compared with the conventional Ru(bpy)₃²⁺/TPrA ECL, the LOP ECL technique not only produces higher emission intensity at lower oxidation-potential, but also significantly reduces the amount of the coreactant.     

Voltammetric determination of glucose based on reduction of copper(II)–glucose complex at lanthanum hydroxide nanowire modified carbon paste electrodes

A novel voltammetric method for the determination of β-d-glucose (GO) is proposed based on the reduction of Cu(II) ion in Cu(II)(NH₃)₄²⁺–GO complex at lanthanum(III) hydroxide nanowires (LNWs) modified carbon paste electrode (LNWs/CPE). In 0.1 mol L⁻¹ NH₃·H₂O–NH₄Cl (pH 9.8) buffer containing 5.0 × 10⁻⁵ mol L⁻¹ Cu(II) ion, the sensitive reduction peak of Cu(II)(NH₃)₄²⁺–GO complex was observed at −0.17 V (versus, SCE), which was mainly ascribed to both the increase of efficient electrode surface and the selective coordination of La(III) in LNW to GO. The increment of peak current obtained by deducting the reduction peak current of the Cu(II) ion from that of the Cu(II)(NH₃)₄²⁺–GO complex was rectilinear with GO concentration in the range of 8.0 × 10⁻⁷ to 2.0 × 10⁻⁵ mol L⁻¹, with a detection limit of 3.5 × 10⁻⁷ mol L⁻¹. A 500-fold of sucrose and amylam, 100-fold of ascorbic acid, 120-fold of uric acid as well as gluconic acid did not interfere with 1.0 × 10⁻⁵ mol L⁻¹ GO determination.     

Determination of dioxopromethazine hydrochloride by capillary electrophoresis with electrochemiluminescence detection

The paper presents a rapid method for the determination of dioxopromethazine hydrochloride (DPZ), an antihistamine drug, by the capillary electrophoresis with electrochemiluminescene detection (CE–ECL) using tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) reagent. This CE–ECL detection method has high sensitivity, good selectivity and reproducibility for DPZ analysis. Under the optimized conditions: separation capillary, 38 cm length (25 μm i.d.); sample injection, 10 s at 8 kV; separation voltage, 12.5 kV; running buffer, 20 mmol L⁻¹ sodium phosphate of pH 6.0; detection potential, 1.15 V; 50 mmol L⁻¹ of phosphate buffer (pH 7.14) containing 5 mmol L⁻¹ of Ru(bpy)₃²⁺ in ECL detection cell, the detection limit of DPZ was 0.05 μmol L⁻¹ (S/N = 3). The linear range extended from 5 to 100 μmol L⁻¹. The linear curve obtained was Y = 181.62 + 9.28X with a correlation coefficient of 0.9970. The relative standard deviations of the ECL intensity and the migration time for six continuous injections of 5 μmol L⁻¹ DPZ were 3.7% and 0.92%, respectively. The CE–ECL method was applied to analyze DPZ in real samples including tablets, rat serum and human urine, and satisfactory results were obtained without interference from samples matrix. The CE–ECL technique was proved to be a potential method for the detection of DPZ in clinic analysis.     

Persulphate quenching of the excited state of ruthenium(II) tris-bipyridyl dication: thermal reactions

The rate constant for the reaction between the sulphate radical (SO₄^√−) and the ruthenium (II) tris-bipyridyl dication (Ru(bipy)₃²⁺) is (3.3±0.2)×10⁹ mol⁻¹ dm³ s⁻¹ in 1 mol dm⁻³ H₂SO₄ and (4.9±0.5)×10⁹ mol⁻¹ dm³ s⁻¹ in 0.1 mol dm⁻³, pH 4.7 acetate buffer. The SO₄^√−radical produced by the electron transfer quenching of Ru(bipy)₃^2+* by S₂O₈²⁻ reacts rapidly with both acetate buffer and chloride ions. These side reactions result in a reduction in the overall quantum yield of Ru(bipy)₃³⁺ production and reduced reaction selectivity when Ru(bipy)₃^2+* is quenched by persulphate.     

Electrochemiluminescence sensor using tris(2,2′-bipyridyl)ruthenium(II) immobilized in Eastman-AQ55D–silica composite thin-films

An electrochemiluminescence (ECL) sensor with good long-term stability and fast response time has been developed. The sensor was based on the immobilization of tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) into the Eastman-AQ55D–silica composite thin films on a glassy carbon electrode. The ECL and electrochemistry of Ru(bpy)₃²⁺ immobilized in the composite thin films have been investigated, and the modified electrode was used for the ECL detection of oxalate, tripropylamine (TPA) and chlorpromazine (CPZ) in a flow injection analysis system and showed high sensitivity. Because of the strong electrostatic interaction and low hydrophobicity of Eastman-AQ55D, the sensor showed no loss of response over 2 months of dry storage. In use, the electrode showed only a 5% decrease in response over 100 potential cycles. The detection limit was 1 μmol l⁻¹ for oxalate and 0.1 μmol l⁻¹ for both TPA and CPZ (S/N=3), respectively. The linear range extended from 50 μmol l⁻¹ to 5 mmol l⁻¹ for oxalate, from 20 μmol l⁻¹ to 1 mmol l⁻¹ for TPA, and from 1 μmol l⁻¹ to 200 μmol l⁻¹ for CPZ.     

毛细管电泳电致化学发光检测血浆中布比卡因

布比卡因是一种外科局部麻醉剂,使用过量会导致中枢神经系统和心脏血管系统中毒^[1],可引起心脏停博.高效液相色谱和毛细管电泳(CE)^[2]是该药常用的检测方法.     

Effect of Ionic Strength on the Electrochemiluminescence Generation by Tris(2,2'-bipyridyl)ruthenium(II)/Tri-n-propylamine

Electrochemiluminescence(ECL) is a powerful transduction technique used in biosensing and in vitro diagnosis, while the mechanism of ECL generation is complicated and affected by various factors. Herein the effect of ionic strength on ECL generation by the classical tris(2,2'-bipyridyl)ruthenium(II)[Ru(bpy)₃²⁺]/tri-n-propylamine(TPrA) system was investigated. It is clear that the ECL intensity decreases significantly with the increase of ionic strength, most likely arising from the reduced deprotonation rate of TPrA^+·. We further combined microtube electrode(MTE) with ECL microscopy to unravel the evolution of ECL layer with the variation of ionic strength. At a low concentration of Ru(bpy)₃²⁺, the thickness of ECL layer(TEL) nearly kept unchanged with the ionic strength, indicating the surface-confined ECL generation is dominated by the oxidative-reduction route. While at a high concentration of Ru(bpy)₃²⁺, ECL generation is dominated by the catalytic route and TEL increases remarkably with the increase of ionic strength, because of the extended diffusion length of Ru(bpy)₃³⁺ at a reduced concentration of TPrA^·.     

Micellar effects on photoinduced redox reactions of Fe(bpy)2(CN)2

Excitation of solutions of Fe(bipy)₂(CN)₂ by a 266-nm laser pulse produces a hydrated electron and the oxidized complex, Fe(bipy)₂ (CN)₂⁺, in the primary photochemical step, in homogeneous aqueous solution as well as in aqueous solutions containing cetyltrimethylammonium bromide (CTAB) or sodium dodecyl sulfate (SDS) micelles. In all cases nascent hydrated electrons react with ground state Fe(bipy)₂(CN)₂ to form Fe(bipy)₂(CN)₂⁻, and comparison of the decay constants in the three media (H₂O: k = 2.8 × 10¹⁰ M⁻¹ s⁻¹; CTAB: k = 2.9 × 10¹⁰ M⁻¹ s⁻¹; SDS: k = 5.5 × 10⁹ M⁻¹ s⁻¹), shows that the reaction is essentially unaffected by CTAB micelles but is much slower in SDS solution. Similar micellar effects were found for the back reaction between e_aq⁻ and Fe(bpy)₂(CN)₂⁺. Rate constants for the scavenging of the photogenerated hydrated electrons by methyl viologen (MV²⁺) cations and NO₃⁻ anions were measured in the three systems, and the results indicate that for scavenging by MV²⁺ the rate constants are decreased in the micelle systems (k in H₂O, 8.4 × 10¹⁰; CTAB, 3.5 × 10¹⁰ and SDS, 1.58 × 10¹⁰ M⁻¹ s⁻¹), whereas for NO₃⁻ the CTAB micelle decreases while the SDS micelle enhances the scavenging compared to water solution (k in H₂O, 8.3 × 10⁹; CTAB, 7 × 10⁸; and SDS, 2.05 × 10¹⁰ M⁻¹ s⁻¹). For the comproportionation reaction between Fe(bipy)₂(CN)₂⁺ and Fe(bipy)₂(CN)₂⁻ both micelles reduce the rate (k in H₂O, 3.3 × 10¹⁰; CTAB, 2.3 × 10¹⁰; and SDS, 1.05 × 10¹⁰ M⁻¹s⁻¹), but while the reaction of Fe(bipy)₂(CN)₂⁺ with MV⁺ is increased in CTAB compared to water, it is slowed in SDS (k in H₂O, 2.4 × 10¹⁰; CTAB, 8.9 × 10¹⁰; and SDS, 1.8 × 10¹⁰ M⁻¹s⁻¹). All effects observed in these microheterogeneous systems can be uniformly interpreted in terms of Coulombic interactions between the actual reactants and the charged surface of the micelles.     

Stabilization and electron spin resonance characterization of Ru(bpy)3 and Ru(bpy)3 by radiolysis of Ru(bpy)3 adsorbed on silica gel

Ru(bpy)₃³⁺, which is important in artificial photosynthetic systems due to its high reduction potential, is stabilized together with its counter anion, Ru(bpy)₃⁺, by radiolysis of Ru(bpy)₃²⁺ adsorbed on silica gel at 77 K. Both species are characterized by electron spin resonance.     

Hydrogen peroxide photoproduction by the semicarbazide—tris(2,2′-bipyridine)ruthenium(II)—oxygen system

A light-driven system consisting of tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)₃²⁺) as the photosensitizer, semicarbazide as the electron donor and molecular oxygen as the electron acceptor has been employed for hydrogen peroxide production. The efficiency of this photosystem markedly depends on pH: while the peroxide yield is almost negligible at acid, neutral or slightly alkaline pH, it reaches significant values at high hydroxide concentrations, the initial rate of H₂O₂ formation drastically increasing from pH 12 to pH 14. In 1 M NaOH solutions containing Ru(bpy)₃²⁺ and semicarbazide at optimum concentrations, the number of catalytic cycles (or turnover number) undergone by the ruthenium complex over the complete course of the photochemical reaction is as high as 1.1 × 10⁴.

Spectrofluorometric and laser flash photolysis techniques were used to study the primary photochemical reactions involving the excited state of the ruthenium complex as well as the photochemically generated species Ru(bpy)₃³⁺ and Ru(bpy)₃⁺. It is proposed that at pH 14 a sequence of reactions leading to O₂ photoreduction by electrons from semicarbazide takes place, with the concomitant formation of H₂O₂; the excited state of Ru(bpy)₃²⁺ appears to react via oxidative quenching by oxygen rather than via reductive quenching by semicarbazide. At neutral pH, in contrast, there is no H₂O₂ formation owing to the fact that semicarbazide is unable to reduce (Ru(bpy)₃³⁺ to Ru(bpy)₃²⁺, although the photoexcited ruthenium complex is quenched equally by oxygen.     

The electrogenerated chemiluminescent behavior of hemin and its catalytic activity for the electrogenerated chemiluminescence of lucigenin

The electrogenerated chemiluminescent (ECL) behavior of hemin at a platinum electrode in the alkaline solution has been investigated in detail. Under the optimum conditions the linear response range of hemin is 1.0×10⁻⁵–1.0×10⁻⁸ g ml⁻¹, the detection limit was 1.0×10⁻⁸ g ml⁻¹, and the relative standard derivation for 1×10⁻⁷ g ml⁻¹ hemin was 2.8%. It has been also found that hemin would catalyze the ECL of lucigenin at a platinum electrode in a neutral solution in the presence of hydrogen peroxide, the catalytic ECL intensity was linear with the concentration of hemin in the range of 1.0×10⁻¹⁴–1.0×10⁻¹⁰ g ml⁻¹. IgG labeled with hemin was used to examine the ECL catalytic activity of hemin after conjugating to protein, and the results showed that hemin retained ECL catalytic activity when conjugated to protein.     

Enhancement of the chemiluminescence of penicillamine and ephedrine after derivatization with aldehydes using tris(bipyridyl)ruthenium(II) peroxydisulfate system and its analytical application

A novel sequential injection (SI) method was developed for the determination of penicillamine (PA) and ephedrine (EP) based on the reaction of these drugs with tris(bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) and peroxydisulfate (S₂O₈²⁻) in the presence of light. Derivatization of PA and EP with aldehydes has resulted in a significant enhancement of the chemiluminescence emission signal by at least 25 times for PA and 12 times for EP, leading to better sensitivities and lower detection limits for both drugs. The instrumental setup utilized a syringe pump and a multiposition valve to aspirate the reagents, (Ru(bpy)₃²⁺ and S₂O₈²⁻), and a peristaltic pump to propel the sample. The experimental conditions affecting the derivatization reaction and the chemiluminescence reaction were systematically optimized using the univariate approach. Under the optimum conditions linear calibration curves between 0.2–24 μg mL⁻¹ for PA and 0.2–20 μg mL⁻¹ for EP were obtained. The detection limits were 0.1 μg mL⁻¹ for PA and 0.03 μg mL⁻¹ for EP. The procedure was applied to the analysis of PA and EP in pharmaceutical products and was found to be free from interferences from concomitants usually present in these preparations.     

Synthesis and Fluorescence of a New Active Material for Electrochemiluminescent Sensor:Ru(phen)2[phen-NHCO(CH2)4Br](PF6)2

Recently, much attention has been paid to Ru(II) complexes because of their excellent properties of photochemistry, phtophysis. Bis(2,2'-bipyridine)[4-methyl-4'-(6-bromohexyl)-2,2'-bipyridine] ruthenium(II) perchlorate has been used as an active material for electrochemiluminescent (ECL) sensor for selective detection of oxalic acid.It is known that ECL efficiency of Ru(phen)₃²⁺ is much higher than that of Ru(bpy)₃²⁺. In order to make out more efficient ECL sensor, we have designed and synthesized a new Ru(II) complex, Ru(phen)₂[phen-NHCO(CH₂)₄Br](PF₆)₂.     

Square wave adsorptive stripping voltammetric determination of famotidine in urine

Electrochemical studies of famotidine were carried out using voltammetric techniques: cyclic voltammetry, linear sweep and square wave adsorptive stripping voltammetry. The dependence of the current on pH, buffer concentration, nature of the buffer, and scan rate was investigated. The best results for the determination of famotidine were obtained in MOPS buffer solution at pH 6.7. This electroanalytical procedure enabled to determine famotidine in the concentration range 1 × 10⁻⁹–4 × 10⁻⁸ mol L⁻¹ by linear sweep adsorptive stripping voltammetry (LS AdSV) and 5 × 10⁻¹⁰–6 × 10⁻⁸ mol L⁻¹ by square wave adsorptive stripping voltammetry (SW AdSV). Repeatability, precision and accuracy of the developed methods were checked. The detection and quantification limits were found to be 1.8 × 10⁻¹⁰ and 6.2 × 10⁻¹⁰ mol L⁻¹ for LS AdSV and 4.9 × 10⁻¹¹ and 1.6 × 10⁻¹⁰ mol L⁻¹ for SW AdSV, respectively. The method was applied for the determination of famotidine in urine.     

Rates of virtually self-exchange energy transfer processes of ruthenium(II) polypyridine complexes

The rate constants of electronic energy transfer from the lowest excited state of Ru(bpy)₂(L)²⁺ or Ru(bpy)(L)₂²⁺ 10 Ru(L)₃²⁺ (b     

Simultaneous potentiometric determination of ClO(3)(-)-ClO(2)(-) and ClO(3)(-)-HClO by flow injection analysis using Fe(III)-Fe(II) potential buffer

A rapid potentiometric flow injection technique for the simultaneous determination of oxychlorine species such as ClO₃⁻–ClO₂⁻ and ClO₃⁻–HClO has been developed, using both a redox electrode detector and a Fe(III)–Fe(II) potential buffer solution containing chloride. The analytical method is based on the detection of a large transient potential change of the redox electrode due to chlorine generated via the reaction of the oxychlorine species with chloride in the potential buffer solution. The sensitivities to HClO and ClO₂⁻ obtained by the transient potential change were enhanced 700–800-fold over that using an equilibrium potential. The detection limit of the present method for HClO and ClO₂⁻ is as low as 5×10⁻⁸ M with use of a 5×10⁻⁴ M Fe(III)–1×10⁻³ M Fe(II) buffer containing 0.3 M KCl and 0.5 M H₂SO₄. On the other hand, sensitivity to ClO₃⁻ was low when a potential buffer solution containing 0.5 M H₂SO₄ was used, but could be increased largely by increasing the acidity of the potential buffer. The detection limit for ClO₃⁻ was 2×10⁻⁶ M with the use of a 5×10⁻⁴ M Fe(III)–1×10⁻³ M Fe(II) buffer containing 0.3 M KCl and 9 M H₂SO₄. By utilizing the difference in reactivity of oxychlorine species with chloride in the potential buffer, a simultaneous determination method for a mixed solution of ClO₃⁻–ClO₂⁻ or ClO₃⁻–HClO was designed to detect, in a timely manner, a transient potential change with the use of two streams of potential buffers which contain different concentrations of sulfuric acid. Analytical concentration ranges of oxychlorine species were 2×10⁻⁵–2×10⁻⁴ M for ClO₃⁻, and 1×10⁻⁶–1×10⁻⁵ M for HClO and ClO₂⁻. The reproducibility of the present method was in the range 1.5–2.3%. The reaction mechanism for the transient potential change used in the present method is also discussed, based on the results of batchwise experiments. The simultaneous determination method was applied to the determination of oxychlorine species in a tap water sample, and was found to provide an analytical result for HClO, which was in good agreement with that obtained by the o-tolidine method and to provide a good recovery for ClO₃⁻ added to the sample.     

Sensitive determination of phenylephrine and chlorprothixene at poly(4-aminobenzene sulfonic acid) modified glassy carbon electrode

Phenylephrine (i.e. PHE) and chlorprothixene (i.e. CPT), two effective and important antipsychotic drugs with low redox activity, were found generating an irreversible anodic peak at about +0.89 V (vs. SCE) and +1.04 V in 0.05 M HAc–NaAc (pH 5.0) or NH₂CH₂COOH–HCl (pH 2.4) buffer solution at poly(4-aminobenzene sulfonic acid) modified glassy carbon electrode (i.e. poly(4-ABSA)/GC), respectively. Sensitive and quantitative measurement for them based on the anodic peaks was established under the optimum conditions. The anodic peak current was linear to PHE and CPT concentrations from 1 × 10⁻⁷ to 1.5 × 10⁻⁵ M and 2 × 10⁻⁶ to 4.5 × 10⁻⁵ M, the detection limits obtained were 1 × 10⁻⁸ and 1 × 10⁻⁷ M, separately. The modified electrode exhibited some excellent characteristics including easy regeneration, high stability, good reproducibility and selectivity. The method proposed was successfully applied to the determination of PHE and CPT in drug injections or tablets and proved to be reliable compared with ultraviolet spectrophotometry. The modified electrode was characterized by electrochemical methods.