Chemiluminescent lipase determination based on the enhanced luminol/H2O2/horseradish peroxidase/fluorescein diacetate energy transfer system

A methodology for the determination of lipase, based on the coupled processes of energy transfer and enhancement of the chemiluminescence of the luminol-H₂O₂-horseradish peroxidase (HRP) system has been developed. Fluorescein diacetate (FDA) was hydrolyzed to fluorescein by the action of the enzyme lipase, and this compound acted as an enhancer of the chemiluminescent process and acceptor of the chemiluminescent emission from the luminol-H₂O₂-HRP system. By measuring the transferred emission to fluorescein at 525 nm, lipase (range 0.2–1.5 U/mL, RSD 2.3%) was determined. This methodology permited the determination of every compound of the system, thus, H₂O₂ (range 0.5–2 mM, RSD 6.9%) and HRP (range 5.5–49.5 U/mL, RSD 3.6%) could also be determined. Lipase was determined in rabbit serum with 96.7 ± 3.3% and 102.9 ± 5.4% recoveries for two different lipase concentrations. Besides, H₂O₂ was determined in the disinfectant solution for contact lenses. Received: 1 March 1999 / Revised: 6 May 1999 / Accepted: 12 May 1999     

Chemiluminescent ion-molecule reactions in the system C+ + H2

The optical emission resulting from collisions between C⁺ ions and H₂ gas was measured in the energy range 2 to 20 eV_c.m.. The observed spectrum consists mainly of the CH⁺ A ¹Π → X ¹Σ⁺ band system; CH⁺ (A ^fΠ) is shown to be formed in the chemiluminescent reactio: C⁺(²P⁰) + H₂ → CH⁺(A ¹Π) + H(²S). The energy dependence of the emission cross section was measured. The occurrence of this reaction is discussed in terms of a electronic state correlation diagram for the system.     

Epoxidation with the H2O2/vilsmeier reagent system

Alkenes $\text{1}$ a–d interact at ?80°C in 15 min. with the Vilsmeier reagent $\text{I}$ (Me₂N=CHCl)⁺PO₂Cl₂^? in presence of 30% H₂O₂ to yield the corresponding epoxides $\text{3}$ a–d. The reaction could involve the formation of the highly reactive hydroperoxymethylenedimethylammonium salt (Me₂N=CHOOH)⁺PO₂Cl^?₂$\text{II}$.     

Graphene enhanced electrochemiluminescence of CdS nanocrystal for H2O2 sensing

Graphene-CdS (G-CdS) nanocomposites were successfully prepared by CdS nanocrystals (CdS NCs) formed in situ on the surface of graphene sheets, using graphene oxide (GO) sheets with rich negatively charged carboxylic acid groups as starting materials. Compared with pure CdS NCs, the presence of the graphene doped in G-CdS nanocomposites could facilitate the electrochemical redox process of CdS NCs; further, the as-prepared G-CdS nanocomposite can react with H₂O₂ to generate strong and stable electrochemiluminescent (ECL) emission, which not only enhances its ECL intensity by about 4.3-fold but also decreases its onset potential for about 320 mV. The as-prepared solid-state ECL H₂O₂ sensor shows acceptable linear response from 5 μM up to 1 mM with a detection limit of 1.7 μM (S/N = 3). The ECL H₂O₂ sensor exhibits excellent reproducibility and long-term stability. Such a property would promote the potential application of the graphene as enhanced materials in fabricating sensors for chemical and biochemical analysis.     

Vibrational energy transfer in H2 + He

A semiclassical approach is developed to study vibrational energy transfer in H₂ + He by use of the a priori interaction potential including all nonzero impact parameter collisions. The calculated values of the rate coefficient are found to be in excellent agreement with experimental data which are available in the temperature ranges 60–450 K and 1350-3000 K. The temperature dependence is shown to seriously deviate from the Landau-Teller prediction below 1000 K. The calculation was carried out over the temperature range of 30 to 10000 K.     

Voltammetric method for the determination of H2O2 in rainwater

Summary Presented below is an electrochemical method for the determination of hydrogen peroxide levels in the atmospheric liquid water. The hydrogen peroxide concentration is determined by a voltammetric method involving a rotating disk electrode. The oxidation limiting current at +0.4 V/SCE is proportional to the concentration of hydrogen peroxide found in 1 mol/l KNO₃ containing a phosphate buffer, pH 7.5. An analytical blank is prepared in situ by addition of catalase enzyme to avoid interferences. The detection limit obtained is 5×10^–9 mol/l.     

Amperometric biosensor based on reductive H2O2 detection using pentacyanoferrate-bound polymer for creatinine determination

Pentacyanoferrate-bound poly(1-vinylimidazole) (PVI[Fe(CN)₅]) was selected as a mediator for amperometric creatinine determination based on the reductive H₂O₂ detection. Creatinine amidohydrolase (CNH), creatine amidohydrolase (CRH), sarcosine oxidase (SOD), peroxidase (POD), and PVI[Fe(CN)₅] were crosslinked with poly(ethylene glycol) diglycidyl ether (PEGDGE) on a glassy carbon (GC) electrode for a creatinine biosensor fabrication. Reduction current was monitored at −0.1 V in the presence of creatinine and O₂. It is revealed that PVI[Fe(CN)₅] is suitable as a mediator for a bioelectrocatalytic reaction of POD, since PVI[Fe(CN)₅] neither reacts with reactants nor works as an electron acceptor of SOD. The amounts of PVI[Fe(CN)₅], PEGDGE, and enzymes were optimized toward creatinine detection. Nafion as a protecting film successfully prevented the enzyme layer from interferences. The detection limit and linear range in creatinine determination were 12 μM and 12–500 μM (R² = 0.993), respectively, and the sensitivity was 11 mA cm⁻² M⁻¹, which is applicable for urine creatinine tests. The results of the creatinine determination for four urine samples measured with this proposed method were compared with Jaffe method, and a good correlation was obtained between the results.     

Intramolecular epoxidation with the H2O2/ortho ester system

Intramolecular epoxidation is shown to occur when trimethyl ortho oleate is treated with H₂O₂.     

H2O2-鲁米诺-荧光素钠-K2CO3高灵敏化学发光法测定二氧化碳

在碱性介质中, CO₃^2－对H₂O₂氧化鲁米诺化学发光反应具有重要作用, 荧光素钠对该反应具有很强的增敏作用. 据此, 建立了化学发光法测定二氧化碳的新方法. 方法的线性范围为1.0×10^－10～5.0×10^－6 mol•L^－1 CO₃^2－, 检出限为 1.2×10^－11 mol•L^－1 CO₃^2－ (相当于5.3×10^－10 g•L^－1 CO₂). 该方法用于室内外空气中二氧化碳含量的测定, 相对标准偏差1.8%～2.1% (n＝11), 加标实验回收率97.6%～101.4%. 论文还探讨了反应的发光机理, 发光反应很可能是由溶液中的CO₃^2－与H₂O₂作用而产生的活性自由基引发, 荧光素钠对发光的增敏作用为化学能量转移过程.     

离子液体/H_2O_2体系脱硫实验研究

选取四种不同种类离子液体(ILs),1-丁基-3-甲基咪唑溴化物([Bmim]Br)、1-丁基-3-甲基咪唑四氟硼酸盐([Bmim]BF_4)、1-丁基-3-甲基咪唑硫酸氢盐([Bmim]HSO_4)、1-丁基-3-甲基咪唑磷酸二氢盐([Bmim]H_2PO_4)与30%H_2O_2溶液在温和条件下对两种高硫脱灰煤样(LS、QX)进行脱硫实验研究。用化学法测定脱硫前后煤样形态硫含量,并利用傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)及热重(TG)对脱硫前后的煤样进行表征。结果表明,离子液体的加入使H_2O_2氧化脱硫能力增强,煤中硫铁矿硫和有机硫化物硫被显著脱除;经ILs/H_2O_2体系作用后的煤样中小粒径的颗粒减少,颗粒间的缝隙增大,煤表面的凹坑明显,热重实验结果表明,ILs/H_2O_2体系作用后的煤样相对于原煤热失重增大,部分挥发性物质释放峰温提前。     

A model study of proton transfer in the H5O2 complex on a bidimensional potential energy surface

We have studied the hydrogen-bonded complex H₃O⁻-H₂O as a model for proton transfer in water. Quantum mechanical computations have been performed in two dimensions (the coordinates are the position of the hydrogen atom and the O-O distance, for a linear geometry), for investigating static and dynamical properties. The validity of the adiabatic separation of the O-O and O-H … O motions has been tested, showing that it holds only in a very restricted range of O-O distances. An initial wavepacket (created by an external perturbation), localized close to one of the two minima, is propagated in time. The proton flux is divided into two contributions, one along the reaction path and the other mainly due to tunnelling.     

The catalytic oxidation of phenol with H2O2 by metalloporphyrins as peroxidase mimics

Summary Three metalloporphyrin complexes are used as peroxidase mimics in the oxidation of phenol by hydrogen peroxide.A kinetic model for the titled reaction is constructed.     

Catalytic decomposition of H2O2 on Co3O4 doped with MgO and V2O5

The effects of doping of Co₃O₄with MgO (0.4–6 mol%) and V₂O₅ (0.20–0.75 mol%) on its surface and catalytic properties were investigated using nitrogen adsorption at −196°C and decomposition of H₂O₂ at 30–50°C. Pure and doped samples were prepared by thermal decomposition in air at 500–900°C, of pure basic cobalt carbonate and basic carbonate treated with different proportions of magnesium nitrate and ammonium vanadate. The results revealed that, V₂O₅ doping followed by precalcination at 500–900°C did not much modify the specific surface area of the treated Co₃O₄ solid. Treatment of Co₃O₄ with MgO at 500–900°C resulted in a significant increase in the specific surface area of cobaltic oxide. The catalytic activity in H₂O₂ decomposition, of Co₃O₄ was found to suffer a considerable increase by treatment with MgO. The maximum increase in the catalytic reaction rate constant (k) measured at 40°C on Co₃O₄ due to doping with 3 mol% MgO attained 218, 590 and 275% for the catalysts precalcined at 500, 700 and 900°C, respectively. V₂O₅-doping of Co₃O₄ brought about a significant progressive decrease in its catalytic activity. The maximum decrease in the reaction rate constant measured at 40°C over the 0.75 mol% V₂O₅-doped Co₃O₄ solid attained 68 and 93% for the catalyst samples precalcined at 500 and 900°C, respectively. The doping process did not modify the activation energy of the catalyzed reaction but much modified the concentration of catalytically active constituents without changing their energetic nature. MgO-doping increased the concentration of CO³⁺–CO²⁺ ion pairs and created Mg²⁺–CO³⁺ ion pairs increasing thus the number of active constituents involved in the catalytic decomposition of H₂O₂. V₂O₅-doping exerted an opposite effect via decreasing the number of CO³⁺–CO²⁺ ion pairs besides the possible formation of cobalt vanadate.     

Copper nanoclusters as peroxidase mimetics and their applications to H2O2 and glucose detection

Copper nanoclusters (Cu NCs) are found to possess intrinsic peroxidase-like activity for the first time. Similar to nature peroxidase, they can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine by H₂O₂ to produce a nice blue color reaction. Compared with horseradish peroxidase, Cu NCs exhibits higher activity near neutral pH, which is beneficial for biological applications. The increase in absorbance caused by the Cu NCs catalytic reaction allows the detection of H₂O₂ in the range of 10 μM to 1 mM with a detection limit of 10 μM. A colorimetric method for glucose detection was also developed by combining the Cu NCs catalytic reaction and the enzymatic oxidation of glucose with glucose oxidase. Taking into account the advantages of ultra-small size, good stability, and high biocompatibility in aqueous solutions, Cu NCs are expected to have potential applications in biotechnology and clinical diagnosis as enzymatic mimics.     

过氧化氢合成方法研究进展*

汇总了近年来H₂O₂的合成方法的主要研究进展,着重介绍了开发的在更温和的反应条件下实现H₂O₂合成的新方法,包括它们的基本原理、优越性和局限性等。推荐将此部分内容在基础无机化学教材中进行更新和补充,这不仅可以丰富元素化学教学内容、拓宽本科生认识范围、增强其环保意识,还可以起到激发学生探索科学、提高创新思维和能力的作用。     

Correlation effects on energy curves for proton transfer. The cation [H5O2]+

Potential curves for proton transfer in [H₅O₂]⁺ and for the dissociation of one OH bond in [H₃O]⁺ were calculated by both ab initio and semi-empirical LCAO MO SCF CI methods. The energy barrier of the symmetric double minimum potential in [H₅O₂]⁺ is very sensitive to electron correlation. At an OO distance of 2.74 Å it decreases from the HF value of 9.5 kcal/mole to about 7.0 kcal/mole. The results of the semi-empirical calculations agree well with the ab initio data as long as only relative effects are regarded. The partitioning of correlation energy into contributions of individual electron pairs is very similar for proton transfer in [H₅O₂]⁺ and for the dissociation of one OH bond in [H₃O]⁺. In this example the proton transfer appears as a superposition of two “contracted ionic dissociation” processes. An interpretation of the behaviour of correlation during these processes is presented.     

NiCo2O4对H2O2在碱性溶液中电化学还原反应的催化行为

利用溶胶-凝胶法合成纳米NiCo2O4,并利用X射线衍射和透射电镜分析其结构和表面形貌. 结果表明NiCo2O4具有尖晶石结构, 平均粒径约为15 nm. 利用电势线性扫描和恒电势法测定了其对H2O2在碱性溶液中电化学还原反应的催化性能. 发现NiCo2O4对H2O2电化学还原具有高的催化活性和稳定性, 在H2O2浓度低于0.6 mol·L-1时, 其电化学还原反应主要通过直接还原途径进行. 以NiCo2O4为阴极催化剂的Al-H2O2半燃料电池在室温下的开路电压达1.6 V; 在1.0 mol·L-1 H2O2溶液中, 峰值功率密度达209 mW·cm-2, 此时电流密度为220 mA·cm-2.     

Na4H3[SiW9Al3(H2O)3O37]·12H2O/H2O: a new system for selective oxidation of alcohols with H2O2 as oxidant

This work describes a catalytic system consisting of both Na₄H₃[SiW₉Al₃(H₂O)₃O₃₇]·12H₂O(SiW₉Al₃) and water as solvents (a small quantity of organic solvents were used as co-solvent for a few substrates) that can be good for selective oxidation of alcohols to ketones (aldehydes) using 30% H₂O₂ without any phase-transfer catalyst under mild reaction conditions. The catalyst system allows easy product/catalyst separation. Under the given conditions, the secondary hydroxyl group was highly chemoselectively oxidized to the corresponding ketones in good yields in the presence of primary hydroxyl group within the same molecule, and hydroxides are selectively oxidized even in the presence of alkene. Benzylic alcohols were selectively oxidized to the corresponding benzaldehydes in good yields without over oxidation products in solvent-free conditions. Nitrogen, oxygen, sulfur-based moieties, at least for the cases where these atoms are not susceptible to oxidation, do not interfere with the catalytic alcohol oxidation.     

Near-infrared H2O2 production via dual pathways of O2 reduction and H2O oxidation

<正>Hydrogen peroxide(H₂O₂) is a chemical that is widely of interest in both environmental and energy fields. On the one hand, as a clean oxidant, H₂O₂ has been commonly used in the field of bleaching, disinfection, and advanced oxidation processes. On the other hand, H₂O₂ has also been explored as a liquid fuel alternative to H₂ or fossil fuels in fuel cells due to its high energy density. However, the current ind...     

Resonance energy transfer from Al2O3 to adsorbed N2O

Radiolysis of adsorbed N₂O is shown to occur due to both the dissociative capture of electrons and direct energy transfer from the excited states of alumina to N₂O. One excited state ensures the decomposition of three N₂O molecules.

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, N₂O , N₂O, N₂O.