Chemiluminescence determination of sulfite in sugar and of sulfur dioxide in air using the tris(2,2′-bipyridyl)ruthenium-KIO4 system

The chemiluminescence (CL) detection for the determination of sulfite using the reaction of Ru(bipy)₃ ²⁺(bipy=2,2′-bipyridyl)-SO₃ ^2–-KIO₄ is described. The concentration of sulfite is proportional to the CL intensity from 1.0 × 10^–7 to 1.0 × 10^–4 mol/L. The limit of detection is 2.0 × 10^–8 mol/L and the relative standard deviation is 4.4% for a 2 × 10^–5 mol/L sulfite solution (n = 9). This method has successfully been applied to the determination of sulfite in powdered sugar (sucrose) and of sulfur dioxide in air by using triethanolamine (TEA) as absorbent material.     

Tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence

This paper critically reviews analytical applications of the chemiluminescence from tris(2,2'-bipyridyl)ruthenium(II) and related compounds published in the open literature between mid-1998 and October 2005. Following the introduction, which summarises the reaction chemistry and reagent generation, the review divides into three major sections that focus on: (i) the techniques that utilise this type of detection chemistry, (ii) the range of analytes that can be determined, and (iii) analogues and derivatives of tris(2,2'-bipyridyl)ruthenium(II).     

Tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence enhanced by silver nanoparticles

Mixtures of silver(I) and citrate that are used to produce silver nanoparticles evoke intense chemiluminescence with tris(2,2'-bipyridyl)ruthenium(II) and cerium(IV), which can be exploited for the determination of citrate ions and other analytes over a wide concentration range.     

Flow Injection Chemiluminescence Method for Nalbuphine Hydrochloride in Pharmaceutical Formulations Using Tris(2,2'-bipyridyl)ruthenium(II) Chloride-diperiodatocuprate(III) Reaction

Asensitive and selective method employing chemiluminescence(CL) coupled with flow injection(FI) is reported for nalbuphine hydrochloride(NAL) assay in pharmaceutical formulations. The enhancement effect of NAL on the CL reaction between tris(2,2'-bipyridyl)ruthenium(II) chloride-diperiodatocuprate(III) {Ru[(bpy)₃]²⁺-Cu(III) complex} in acidic medium is used as analytical measurement. The optimal conditions of the CL reaction were sulfuric acid 1.0×10^-3 mol/L, Ru[(bpy)₃]²⁺ 7.5×10^-5 mol/L, Cu(III)/Ag(III) complexes 4.0×10^-4/5.0×10^-4 mol/L, sample loop volume of 120 μL and flow rate of 2.5 mL/min. The sensitivities of the method in terms of detection(S/N=3) and quantification(S/N=10) limits are 5×10^-4 and 0.001 ppm(1 ppm=1 mg/L), respectively. The linear response of the instrument in the form of CL intensity with respect to NAL concentration is over the range 0.001-15.0 ppm(R²=0.9999) with relative standard deviation from 0.8% to 3.2% and injection throughput of 120 injection/h. The applications of the method include the quantitative analysis of NAL in pharmaceutical injection samples. Variations and the average results of the proposed method are not signi-ficantly different from the results of a reported method by applying F- and paired student t-test. The most likely CL reaction mechanism is written in accordance with spectrophotometric and CL studies.     

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^·.     

Tris(2,2'-bipyridyl)ruthenium(II)-zirconia-Nafion composite films applied as solid-state electrochemiluminescence detector for capillary electrophoresis

The major goal of this work was to develop a new solid-state electrochemiluminescence (ECL) detector suitable for capillary electrophoresis (CE). The detector was fabricated by coating a sol-gel derived zirconia (ZrO(2))-Nafion composite film on a graphite electrode, then the zirconia-Nafion modified electrode was immersed in tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3) (2+)) solution to immobilize this active chemiluminescence reagent. The voltammetric and ECL behaviors of the detector were investigated and optimized in tripropylamine solution. The ratio of 53% for zirconia in the zirconia-Nafion composite provided the highest luminescence intensity of immobilized Ru(bpy)(3) (2+). The ECL can maintain its stability very well in the phosphate solution in the period of 5-90 h when the solid-state ECL detector was immersed in the solution all the time. The optimum distance of capillary outlet to the solid-state ECL detector has been found to be ca. 50-80 microm for a 75 microm capillary. The effects of ionic strength and pH of ECL solution on peak height were investigated. The CE with solid-state ECL detector system was successfully used to detect tripropylamine, lidocaine, and proline. The detection limits (S/N = 3) were 5 x 10(-9) mol.L(-1) for tripropylamine, 1 x 10(-8) mol.L(-1) for lidocaine and 5 x 10(-6) mol.L(-1) for proline, and the linear ranges were from 1.0 x 10(-8) to 1.0 x 10(-5) mol.L(-1) for tripropylamine, 5.0 x 10(-7) mol.L(-1) to 1.0 x 10(-5) mol.L(-1) for lidocaine and 1.0 x 10(-5) to 1.0 x 10(-3) mol.L(-1) for proline, respectively.     

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.     

Flow-injection chemiluminescence determination of enalapril maleate in pharmaceuticals and biological fluids using tris(2,2'-bipyridyl)ruthenium(II).

A chemiluminescence (CL) method using flow injection (FI) has been investigated for the rapid and sensitive determination of enalapril maleate. The method is based on the CL reaction of the drug with tris(2,2'-bipyridyl)ruthenium(II), Ru(bipy)3(2+) and acidic potassium permanganate. After selecting the best operating parameters, calibration graphs were obtained over concentration ranges of 0.005-0.2 microg/ml and 0.7-100 microg/ml with a detection limit (S/N=2) of 1.0 ng/ml. The average % found was 99.9 +/- 0.7 and 100.2 +/- 0.3 for the two concentration ranges respectively. %RSD (n=10) for 5.0 microg/ml was 0.44. The method was successfully applied to the determination of enalapril maleate in dosage forms and biological fluids without interferences.     

Indirect spectrophotometric determination of sulfur dioxide (sulfite)

Sodium sulfite/sulfur dioxide reacts with iron(III) in acidic range (pH 2–3.5) to form iron(II) which is complexed with 1,10-phenanthroline to form a stable orange-red complex with maximum absorption at 510 nm. Beer's Law is obeyed over the concentration range of 0.5–10 ppm of sulfur dioxide.     

Controlling the helicity of 2,2'-bipyridyl ruthenium(II) and zinc(II) hemicage complexes

Two enantiomers of a new 4,5-pineno-2,2'-bipyridine ligand were synthesized and subsequently incorporated into hemicage ligands through a phenyl linker to yield ligands (+)-L1 and (-)-L1 or through a mesityl linker to yield ligands (+)-L2 and (-)-L2. Complexation of these ligands to Ru(II) afforded diastereomerically pure Delta and Lambda isomers, as verified through circular dichroism and circularly polarized luminescence spectroscopy. Ligands (+)-L2 and (-)-L2 were further coordinated to Zn(II) to form a complex with intriguing photophysical properties. Whereas Zn(bpy)32+ was shown to be a fluorescent emitter outside the visible spectrum, the caging process provided an unprecedented enhancement of intersystem crossing and subsequent switching to the phosphorescent emission of blue light. Additionally, the chiroptical properties of the Zn(II) complexes were also studied.     

Confirmation of the classic tris(2,2'-bipyridyl)ruthenium(II) and oxalate electrochemiluminescence mechanism using EPR spectroscopy

A chemically initiated adaptation of the classic [Ru(bipy)(3)](2+)/oxalate electrochemiluminescence coreactant system has revealed the elusive radical intermediates of the light-producing pathway. Oxalyl (HC(2)O(4)˙) and hydroxyformyl (HCO(2)˙) radicals have been captured on a quartz surface and characterised using EPR spectroscopy.     

Enhancing the electrochemiluminescence of tris(2,2'-bipyridyl)ruthenium(II) by ionic surfactants

The dependence of the electrochemiluminescence of Ru(bpy)3(2+) (bpy = 2,2'-bipyridine) with tri-n-propylamine as co-reactant on the anionic surfactant SDS (sodium dodecyl sulfate) and the cationic surfactants CTAX (CTA = cetyltrimethylammonium cation, X = bromide, chloride and hydrogensulfate) was studied. Both SDS and CTAX, at low surfactant concentrations below the critical micelle concentrations, enhance the electrochemiluminescence at a platinum working electrode. A further enhancement of the light emission intensity by bromide ions was observed when CTAB (B = bromide) was used-an overall 30-fold increase in electrochemiluminescence efficiency was obtained at a CTAB concentration of 0.08 mM. Voltammetric data support adsorption of surfactant molecules on the electrode surface as the cause of the enhancement of electrochemiluminescence by ionic surfactants.     

Flow-injection determination of thyroxine using immobilized enzyme with tris(2,2'-bipyridyl)ruthenium(III) chemiluminescence detection.

A flow-injection method is reported for the determination of thyroxine based on its enhancement effect on the tris(2,2'-bipyridyl)ruthenium(III) chemiluminescence reaction in the presence of NADH using immobilized alcohol dehydrogenase purified from baker yeast. The limit of detection (3 sigma blank) was 5.0 x 10(-8) M with a sample throughput of 80 h(-1). The calibration graph was linear over the range 0.5 - 10 x 10(-7) M (r2= 0.9988) with the relative standard deviation in the range 1.4 - 3.5% (n = 4). The effect of common excipients used in pharmaceutical preparations, some organic compounds and metal ions was studied. The method was applied to pharmaceutical thyroxine tablets, and the obtained results were not significantly different from the amount quoted.     

Determination of proline in wine using flow injection analysis with tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence detection

Flow injection methodology is described for the determination of proline in red and white wines using tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection. Selective conditions were achieved for proline at pH 10, while other amino acids and wine components did not interfere. The precision of the method was less than 1.00% (R.S.D.) for five replicates of a standard (4 × 10⁻⁶ M) and the detection limit was 1 × 10⁻⁸ M. The level of proline in white and sparkling wines using the developed methodology was equivalent to those achieved using HPLC-FMOC amino acid analysis. SPE removal of phenolic material was required for red wines to minimize Ru(bipy)₃³⁺ consumption and its associated effect on accuracy.     

Flow injection fluorimetric determination of chromium(VI) in electroplating baths by luminescence quenching of tris(2,2'-bipyridyl) ruthenium(II)

A sensitive and selective luminescence quenching method is developed and used for manual and flow injection analysis (FIA) of chromium(VI) by reaction with [Ru(bpy)₃]²⁺. The emission peak of ruthenium(II) at 595 nm is linearly decreased as a function of Cr(VI) concentration. This permits determination of chromium(VI) ion over the concentration range 0.1-20 μg ml⁻¹ with a detection limit of 33 ng ml⁻¹. The quenching process is due to an electron transfer from the luminescent [Ru(bpy)₃]²⁺ complex ion to Cr(VI) resulting in the formation of the non-luminescent [Ru(bpy)₃]³⁺ complex ion. Selectivity for Cr(VI) over many anions and transition, alkali and alkaline earth metal cations is demonstrated. High concentration levels of sulphate, chloride, borate, acetate, phosphate, nitrate, cyanide, Pb²⁺, Zn²⁺, Hg²⁺, Cu²⁺, Cd²⁺, Ni²⁺ and Mn²⁺ ions are tolerated. The effects of solution pH and [Ru(bpy)₃]²⁺ reagent concentration are examined and the reaction conditions are optimized. Validation of the method according to the quality assurance standards show suitability of the proposed method for use in the quality control assessment of Cr(VI) in complex matrices without prior treatment. The method is successfully applied to determine chromium(VI) in electroplating baths using flow injection analysis. Results with a mean standard deviation of ±0.6% are obtained which compare fairly well with data obtained using atomic absorption spectrometry.     

Solid-supported chemiluminescence and electrogenerated chemiluminescence based on a tris(2,2'-bipyridyl)ruthenium(II) derivative

We report a simple and efficient technique for the covalent immobilisation of a tris(2,2'-bipyridyl)ruthenium(II) derivative suitable for both chemiluminescence and electrochemiluminescence detection.