Flow-injection chemiluminescence simultaneous determination of cobalt(II) and copper(II) using partial least squares calibration

A flow-injection chemiluminescence (CL) system is proposed for simultaneous determination of Co²⁺ and Cu²⁺ using partial least squares (PLS) calibration. This method is based on the fact that both Co²⁺ and Cu²⁺ catalyse the CL reaction of luminol-H₂O₂, and that their kinetic characteristics of Co²⁺ and Cu²⁺ are significantly different in the luminol-H₂O₂ system. The CL intensity was measured and recorder at different reaction times of luminol-H₂O₂Co²⁺Cu²⁺, and the obtained data were processed by the chemometric approach of partial least squares. The experimental calibration set was composed of 16 sample solutions using an orthogonal calibration design for two component mixtures. The proposed method offers the potential advantages of high sensitivity, simplicity and rapidity for Co²⁺ and Cu²⁺ determination, and was successfully applied to the simultaneous determination of both analytes in real water sample. The present paper demonstrated that the simultaneous determination of two metal ions without any prior separation has been possible using flow-injection CL system.     

1-Ethyl-3-methylimidazolium ethylsulfate/copper(II) as catalyst for lucigenin chemiluminescence and its application to glucose detection

The present study reports the effect of an ionic liquid (IL), 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO ₄]), on the Cu2+-catalyzed lucigenin/H₂O₂ chemiluminescence system in the range of pH 6.5?10. At pH 8.0, the greatest enhancement on light emission is observed, related to a strong interaction between Cu²⁺ and the imidazolium ring at this pH. Furthermore, the formation of IL microdomains in the aqueous solution enhances in solubility of N-methylacridone, an insoluble emitter that can be very effective in lucigenin chemiluminescence (Luci-CL). The mentioned findings encouraged us to suggest a novel and simple method for the determination of glucose with the detection limit of 7 μM at pH 8.0 based on the detection of H₂O₂ liberated in enzymatic reaction between glucose oxidase and glucose by the [Emim][EtSO ₄]/Cu²⁺-catalyzed Luci-CL system. Also, the developed method was successfully applied to the determination of glucose in real plasma and urine samples of diabetic patients and validated against colorimetric spectroscopy method.     

Promotion of the fenton reaction by Cu2+ ions: Evidence for intermediates

The promotion of the Fenton reaction by Cu²⁺ ions has been investigated using a wide range of [Cu²⁺]. Both the disappearance of Fe²⁺ and the evolution of O₂ were followed as a function of time by quenching the reaction mixture with o‐phenanthroline or with excess Fe^{2 +} ions, respectively. Two series of experiments were performed. In one series [H₂O₂] was 5 × 10⁻⁴ mol dm⁻³, and in the other [H₂O₂] was reduced to 5 × 10⁻⁵ mol dm ⁻³. By stopping the reaction with excess Fe²⁺ ions, significant differences in the measured absorbance in the two series were observed. In the higher [H₂O₂] range, the absorbance decreased monotonically in time, due to O₂ formation during the reaction. In the lower range, an initial transient rise of the absorbance was observed, indicating the formation of spectroscopically distinct intermediates in the system. A mechanism involving the intermediates FeOCu⁴⁺ and FeOCu⁵⁺ has been set up. Rate constants of the mechanism have been determined. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 725–736, 2006     

Detection of Metal Ions (Cu2+, Hg2+) and Cocaine by Using Ligation DNAzyme Machinery

The Cu²⁺‐dependent ligation DNAzyme is implemented as a biocatalyst for the colorimetric or chemiluminescence detection of Cu²⁺ ions, Hg²⁺ ions, or cocaine. These sensing platforms are based on the structural tailoring of the sequence of the Cu²⁺‐dependent ligation DNAzyme for specific analytes. The tethering of a subunit of the hemin/G‐quadruplex DNAzyme to the ligation DNAzyme sequence, and the incorporation of an imidazole‐functionalized nucleic‐acid sequence, which acts as a co‐substrate for the ligation DNAzyme that is tethered to the complementary hemin/G‐quadruplex subunit. In the presence of different analytes, Cu²⁺ ions, Hg²⁺ ions, or cocaine, the pretailored Cu²⁺‐dependent ligation DNAzyme sequence stimulates the respective ligation process by combining the imidazole‐functionalized co‐substrate with the ligation DNAzyme sequence. These reactions lead to the self‐assembly of stable hemin/G‐quadruplex DNAzyme nanostructures that enable the colorimetric analysis of the substrate through the DNAzyme‐catalyzed oxidation of 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid), ABTS^2?, by H₂O₂ into the colored product ABTS^.?, or the chemiluminescence detection of the substrate through the DNAzyme‐catalyzed oxidation of luminol by H₂O₂. The detection limits for the sensing of Cu²⁺ ions, Hg²⁺ ions, and cocaine correspond to 1 nM , 10 nM and 2.5 μM , respectively. These different sensing platforms also reveal impressive selectivities.     

Zur Kinetik des durch Cu2+-Äthylendiamin katalysierten H2O2-Zerfalls: Metallionen und H2O2, 14. Mitteilung

Kinetic studies of the Cu²⁺-ethylenediamine catalysed decomposition of H₂O₂ show the initial rate v₀ of H₂O₂ decomposition to be proportional to [H+]^?1, [H₂O₂], and [Cu²⁺-en]². Maximal velocity is found at a ratio of [Cu²⁺]_tot:[en]_tot = 1:1,5. It is suggested that the active complex has a binuclear structure. This structure and probable mechanisms of the reaction are discussed. The kinetic measurements of the Cu²⁺-diethylenetriamine-H₂O₂ system are difficult to interprete because of degradation of the ligand by H₂O₂.     

Determination Co2+ in vitamin B12 based on enhancement of 2-(4-substituted-phenyl)-4,5-di(2-furyl) imidazole and H2O2 chemiluminescence reaction

In this paper, three kinds of imidazole derivatives, 2-(4-methylphenyl)-4,5-di(2-furyl) imidazole (MDFI), 2-(4-nitrophenyl)-4,5-di(2-furyl) imidazole (NDFI), and 2-(4-tert-butylphenyl)-4,5-di(2-furyl) imidazole (t-BDFI) were synthesized. In an alkaline medium, the chemiluminescence (CL) reaction of imidazole derivatives with H₂O₂ has been investigated. It was also found that MDFI/H₂O₂ and t-BDFI/H₂O₂ systems gave strong CL. When Co²⁺ was added into the two CL systems, the CL intensity was remarkably enhanced. In the optimum conditions, the CL intensity is linearly related to the logarithm of concentration of Co²⁺. The linear ranges are 5 × 10⁻⁹–2.5 × 10⁻⁷ mol/L for MDFI/H₂O₂ system and 5 × 10⁻⁹–2.5 × 10⁻⁷ mol/L for t-BDFI/H₂O₂ system, and the corresponding detection limits are 1.2 × 10⁻⁹ mol/L and 1.1 × 10⁻⁹ mol/L, respectively. The method was applied to the determination of Co²⁺ in vitamin B₁₂ injection. Furthermore, the CL mechanism was also discussed.     

Valence‐to‐Core X‐ray Emission Spectroscopy as a Probe of O−O Bond Activation in Cu2O2 Complexes

Valence‐to‐Core (VtC) X‐ray emission spectroscopy (XES) was used to directly detect the presence of an O?O bond in a complex comprising the [Cu^II₂(μ‐η²:η²‐O₂)]²⁺ core relative to its isomer with a cleaved O?O bond having a [Cu^III₂(μ‐O)₂]²⁺ unit. The experimental studies are complemented by DFT calculations, which show that the unique VtC XES feature of the [Cu^II₂(μ‐η²:η²‐O₂)]²⁺ core corresponds to the copper stabilized in‐plane 2p π peroxo molecular orbital. These calculations illustrate the sensitivity of VtC XES for probing the extent of O?O bond activation in μ‐η²:η²‐O₂ species and highlight the potential of this method for time‐resolved studies of reaction mechanisms.     

Improved sensitivity for some [corrected] metal ions by use of sulfide in the Belousov-Zhabotinskii oscillating reaction

A highly sensitive method for the determination of trace amounts of transition metal ions by use of sulfide in the Belousov-Zhabotinskii (B-Z) oscillating chemical reaction is proposed. The use of sulfide increased strongly the sensitivity of the B-Z reaction for transition metal ions, such as Ag⁺, Pb²⁺, Hg²⁺, Cd²⁺, Cu²⁺,and Bi³⁺. Results showed that the variational ratio of oscillating period (P_R) is linearly proportional to the negative logarithm of concentration of metal ions. The detection limit is down to 10⁻¹² mol L⁻¹. Various influencing factors on the determination were also examined.     

Nonlinear chemical reaction between Na2S2O3 and Peroxide compound

Kinetics of reaction between Na₂S₂0₃ and peroxide compound (H₂0₂ or Na₂S₂O₃) in a batch reactor and in a continuous stirring tank reactor (CSTR) were studied. Steady oscillations in uncatalyzed reactions in a CSTR were first discovered. In Na₂S₂0₃-H₂O₂-H₂S0₄ reaction system, Pt potential and pH of higher and lower flow rates beyond oscillation flow rates were in around the same extreme values. The reaction catalyzed by Cu²⁺ consists of the catalyzed oscillation process and the uncatalyzed osciliation one. On the basis of experiment, a reaction mechanism consisting of three stages was put forward. The three stages are H⁺ positive-feedback reactions, proton negative-feedback (uncatalyzed negative-feedback and catalyzed negative-feedback) reactions and transitional reactions. The mechanism is able to explain reasonably the nonlinear chemical phenomena appearing in the thiosulfate oxidation reaction by peroxide compounds. Project supported by the National Natural Science Foundation of China.     

A simple chemiluminescence method for determination of chemical oxygen demand values in water

In this paper, a low cost chemiluminescence detector with a photodiode instead of photo-multiplier tube (PMT) was developed for environmental monitoring of water quality. Based on the chemiluminescent reaction of luminol-H₂O₂-Cr³⁺ system, light emission caused by luminol-H₂O₂-Cr³⁺ system was detected by the photodiode, and its intensity caused by the appearance of Cr³⁺ after samples digestion was proportional to the chemical oxygen demand (COD). Effects for COD determining such as pH, concentrations, interference, and digestion procedures were investigated. The experimental results show that this suggested method uses an instrument that is simpler and cheaper than the previous ones used for the same purpose. The data obtained by the present method were fairly in good agreement with those obtained by the standard reflux titrimetric method. It has been applied to determine real samples with satisfactory results.     

Quenching effect of some heavy metal ions on the fast peroxyoxalate-chemiluminescence of 1-(dansylamidopropyl)-1-aza-4,7,10-trithiacyclododecane as a novel fluorophore

The fast chemiluminescence (CL) arising from the reaction of bis(2,4,6-trichlorophenyl)oxalate (TCPO) with hydrogen peroxide in the presence of 1-(dansylamidopropyl)-1-aza-4,7,10-trithiacyclododecane (L) as a novel fluorophore, and imidazole as catalyst, has been studied in ethyl acetate solution. The relationships between the chemiluminescence intensity and concentrations of TCPO, imidazole, hydrogen peroxide and L are reported. In the presence of imidazole as catalyst, the entire CL signal was completed in less than 3 s. The quenching effect of Cu²⁺, Pb²⁺, Cd²⁺, Hg²⁺ and Ag⁺ ions on the chemiluminescent system was investigated, the resulting Stern–Volmer plots were obtained and the K_Q values were calculated. It was found that the quenching effect of metal ions on the chemiluminescence of L decreases in the order Cu²⁺ > Pb²⁺ > Cd²⁺ > Hg²⁺ > Ag⁺.     

Thermal analysis and epr studies of carbon black oxidation in the presence of copper loaded Y2O3-CeO2-ZrO2 catalyst

The activity of copper-free and copper-loaded 10Y₂O₃-10CeO₂-80ZrO₂ solid solutions towards carbon black combustion was studied using simultaneous thermogravimetric analysis and differential thermal analysis techniques coupled with gas chromatography. It was demonstrated that all studied catalysts lower the temperature of carbon black combustion. The selectivity of the catalytic reaction in CO₂ formation was 100%. The comparison of electron paramagnetic resonance (EPR) spectra of pure catalysts with those of the samples (catalysts mixed with carbon black) after catalysis allowed to evidence, despite of the strong oxidizing atmosphere, a thermal reduction by carbon of Fe³⁺ (impurities), Cu²⁺ and Zr⁴⁺ during the reaction. Moreover a new EPR signal appeared after catalytic test and was attributed to the presence of paramagnetic metal-carbon or/and metal-sulphur complexes. This revised version was published online in August 2006 with corrections to the Cover Date.     

A thermodynamic study of the Cu-Cr-O system by the EMF method

The equilibrium oxygen pressures of the three-phase regions [Cu, Cr₂O₃, Cu₂Cr₂O₄], [Cu, Cu₂O, Cu₂O₂O₄] and [CuO, Cu₂O, Cu₂Cr₂O₄] were measured as a function of temperature by the solid oxide electrolyte electromotive force method. The measured Gibbs energy of the reaction Cu₂O+ Cr₂O₂ = Cu₂Cr₂O₄ (ΔG°) was found to be −46608 + 7.8328 T J mol⁻¹ (1075–1275 K). The evaluated Gibbs energy of formation of Cu₂Cr₂O₄ (ΔG°(inf,Cu₂Cr₂O₄)) was found to be −1332900 + 332.761 T J mol⁻¹ (900–1350 K).     

Determination of Ascorbic Acid Using a New Oscillating chemical System of Lactic Acid—Acetone—BrO3^— —Mn^2 —H2SO4

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Direct kinetics study of the temperature dependence of the CH2O branching channel for the CH3O2 + HO2 reaction

A direct kinetics study of the temperature dependence of the CH₂O branching channel for the CH₃O₂ + HO₂ reaction has been performed using the turbulent flow technique with high‐pressure chemical ionization mass spectrometry for the detection of reactants and products. The temperature dependence of the CH₂O‐producing channel rate constant was investigated between 298 and 218 K at a pressure of 100 Torr, and the data were fitted to the following Arrhenius expression: 1.6 × 10^?15 × exp[(1730 ± 130)/T] cm³ molecule^?1 s^?1. Using the Arrhenius expression for the overall rate of the CH₃O₂ + HO₂ reaction and this result, the 298 K branching ratio for the CH₂O producing channel is measured to be 0.11, and the branching ratio is calculated to increase to a value of 0.31 at 218 K, the lowest temperature accessed in this study. The results are compared to the analogous CH₃O₂ + CH₃O₂ reaction and the potential atmospheric ramifications of significant CH₂O production from the CH₃O₂ + HO₂ reaction are discussed. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 363–376, 2001     

The rate constant of NO + O3 → NO2 + O2 in the temperature range of 283–443 K

The reaction NO + O₃ → NO₂ + O₂ has been studied in a 220-m³ spherical stainless steel reactor under stopped-flow conditions below 0.1 mtorr total pressure. Under the conditions used, the mixing time of the reactants was negligible compared with the chemical reaction time. The pseudo-first-order decay of the chemiluminescence owing to the reaction of ozone with a large excess of nitric oxide was measured with an infrared sensitive photomultiplier. One hundred twenty-nine decays at 18 different temperatures in the range of 283–443 K were evaluated. A weighted least-squares fit to the Arrhenius equation yielded k = (4.3 ± 0.6) × 10^?12 exp[-(1598 ± 50)/T] cm³/molecule sec (two standard deviations in brackets). The Arrhenius plot showed no curvature within experimental accuracy. Comparison with recent results of Birks and co-workers, however, suggests that a nonlinear fit, as proposed by these authors, is more appropriate over an extended temperature range.     

Imidazolium-based ionic liquid derivative/Cu<Superscript>II</Superscript> complexes as efficient catalysts of the lucigenin chemiluminescence system and its application to H<Subscript>2</Subscript>O<Subscript>2</Subscript> and glucose detection

The effects of six synthetic imidazolium-based ionic liquids (ILs) on the Cu^II-catalyzed chemiluminescence of lucigenin (Luc-CL) in the pH range 6.0–11 were investigated. Preliminary experiments found that the CL emission was strongly enhanced or inhibited in the presence of the ILs. The degree of enhancement or inhibition of the CL intensity in the presence of each IL was related to the molecular structure of the IL, the medium used, and the pH. The maximum enhancement of the CL intensity was observed at pH 9.0 (amplification factor?=?443). This decrease in the pH at which maximum CL enhancement occurred and the substantial signal amplification of the Luc-CL may be related to a strong interaction between Cu^II and the imidazolium ring of superior ILs at this pH. Additionally, the formation of IL microdomains in semi-aqueous media permitted more solubility of the product yielded by the Luc-CL reaction (N-methylacridone), which could increase the CL intensity. To obtain consistent data on the catalytic efficiency of Cu^II in the presence of various ILs as well as the corresponding CL emission intensities, fluorescence quantum yields (Φ _F) of lucigenin were measured under the same conditions. Comparison of the data pointed to the mechanism that controls the properties of Luc-CL in the presence of the Cu^II/IL complexes. Based on the catalytic effect of the Cu^II/IL complex and the measurement of the enzymatically generated H₂O₂, a novel, simple, and sensitive CL method for determining glucose with a detection limit (LoD) of 6.5 μM was developed. Moreover, this method was satisfactorily applied to the determination of glucose in human serum and urine samples.

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Graphical Abstract The lucigenin chemiluminescence assay for H₂O₂ and glucose using imidazolium–based ionic liquid derivatives/Cu^II complexes as efficient catalysts at pH 9.0

     

A direct fluorescence-on chemo-sensor for selective recognition of Zn(II) by a lower rim 1,3-di-derivative of calix[4]arene possessing bis-{N-(2-hydroxynaphthyl-1-methylimine)} pendants

The bis-{N-(2-hydroxynaphthyl-1-methylimine)} anchored 1,3-di-derivative of lower rim p-tert-butyl-calix[4]arene possessing a N₂O₂, N₂O₄ or N₂O₆ binding core was found to be selective for Zn(II) ions even at ?60 ppb by eliciting fluorescence-on behaviour while the other ions, viz., Ti⁴⁺, VO²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Mg²⁺, Cd²⁺ and Hg²⁺ caused no change in the fluorescence. The reaction between 1 and Zn²⁺ was found to be stoichiometric with the formation of a 1:1 complex; while H⁺ quenched the fluorescence of the complex, OH⁻ restored it. The studies of the 1:1 isolated complexes of Zn²⁺, Ni²⁺ and Cu²⁺ augmented the results.     

Mechanism of the oxidation reaction of Cu with N2O via nonadiabatic electron transfer

We treat the present work as an attempt to elucidate the mechanism of the oxidation reaction of the Cu atom by nitrous oxide based on our recent work (Kryachko, E. S.; Vinckier, C.; Nguyen, M. T. J Chem Phys 2001, 114, 7911) on the electron attachment to this molecule. We suggest that the title reaction in its Arrhenius regime occurs via the nonadiabatic electron transfer from Cu to the oxygen atom at the crossing of the potential energy surfaces Cu(4s ²S_1/2) + N₂O(X ¹Σ⁺) and Cu⁺ + N₂O^?, where the latter is linked to the complex N₂O^? originated from the higher‐energy T‐shape N₂O molecule and discovered in the aforementioned work. The calculations performed in the present work using a variety of quantum chemical methods support the proposed model. We also show the existence of other reaction pathways of the title reaction that, we believe, contribute to its non‐Arrhenius behavior observed experimentally at T > 1190 K. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002     

Thiourea based conjugated polymer fluorescent chemosensor for Cu+ and its use for the detection of hydrogen peroxide and glucose

A novel conjugated polymer, poly(1), containing thiourea moieties in main chain is synthesized via Suzuki coupling reaction. The addition of cuprous ion quenches the fluorescence of poly(1), whereas the fluorescence changes slightly upon addition of other metal ions, exhibiting the fluorescent almost turn-off sensing ability towards Cu⁺. When hydrogen peroxide was added to the solution containing poly(1) and Cu⁺, Cu⁺ was oxidized into Cu²⁺, resulting in the fluorescence recovery. The H₂O₂ released from glucose oxidation by glucose oxidase (GOD) also recovered the fluorescence of poly(1)/Cu⁺ solution. The results indicated that the poly(1)/Cu⁺ solution could serve as a sensing platform for hydrogen peroxide and glucose.