Enhanced chemiluminescence for the oxidation of luminol with m-chloroperoxybenzoic acid catalyzed by microperoxidase 8

The use of m-chloroperoxybenzoic acid (mCPBA) in stead of hydrogen peroxide causes an increase in chemiluminescence (CL) of luminol oxidation catalyzed by microperoxidase 8 (MP8) by an order of magnitude. The accelerated formation of an intermediate plays a major role in the CL enhancement, which also leads to a significant reduction in CL duration. The presence of guanidine hydrochloride, sodium carbonate, or sodium chloride further increases the CL emission drastically. The CL emission enhancement is strongly pH dependent. The enormous enhancement of the CL signal is due to an accelerated CL cycle and an improved CL efficiency in the presence of the enhancer. The CL signal covers several orders of magnitude over a wide range of concentrations of luminol and mCPBA. The intense CL of MP8-luminol-mCPBA in the presence of the enhancer will have great potential for extremely sensitive CL assays.     

Enhancement in Chemiluminescence by Carbonate for Cobalt(II)‐catalyzed Oxidation of Luminol with Hydrogen Peroxide

Chemiluminescence (CL) from the cobalt(II)‐catalyzed oxidation of luminol with hydrogen peroxide was dramatically enhanced by the presence of carbonate. The CL signal increases by several orders of magnitude over a wide range of concentrations of Co(II), luminol, or hydrogen peroxide. A limit of detection of 10^?12 M for Co(II) and luminol and 10^?8 M for hydrogen peroxide can be achieved. The CL emission spectrum exhibits a maximum at 425 nm, indicating that the excited 3‐aminophthalate is the emitting species. ESR spin‐trapping experiments revealed a large increase in the production of hydroxyl and carbonate radicals by the presence of carbonate, which is responsible for the enormous CL enhancement. Uric acid, ascorbic acid, acetaminophen, and p‐hydroxyphenyl acetic acid are capable of scavenging the radicals, thereby inhibiting the CL emission. The inhibition of CL intensity can be used to determine these substances at the sub‐micromolar level.     

Chemiluminescent Determination of Vitamin B12 Using Charge Coupled Device (CCD)

A method was developed for the determination of vitamin B₁₂ based on the enhancement of cobalt (II) on the chemiluminescence (CL) reaction between luminol and percarbonate (powerful source of hydrogen peroxide). The release of cobalt (II) from the vitamin B₁₂ was reached by a simple and fast microwave digestion (20 s microwave digestion time and a mix of nitric acid and hydrogen peroxide). A charge coupled device (CCD) photodetector, directly connected to the cell, coupled with a simple continuous flow system was used to obtain the full spectral characteristics of cobalt (II) catalyzed luminol-percarbonate reaction.

The optima experimental conditions were established: 8.0 m mol L^?1 luminol in a 0.075 mol L^?1 carbonate buffer (pH 10.0) and 0.15 mol L^?1 sodium percarbonate, in addition to others experimental parameters as 0.33 mL s^?1 flow rate and 2 s integration time, were the experimental conditions which proportionate the optimum CL emission intensity. The emission data were best fitted with a second-order calibration graph over the cobalt (II) concentration range from 4.00 to 300 µ g L^?1 (r² = 0.9990), with a detection limit of 0.42 µ g L^?1. The proposed method was successfully applied to the determination of vitamin B₁₂ in pharmaceuticals.     

β−cyclodextrins-based inclusion complexes of CoFe2O4 magnetic nanoparticles as catalyst for the luminol chemiluminescence system and their applications in hydrogen peroxide detection

β−cyclodextrins (β−CD)-based inclusion complexes of CoFe₂O₄ magnetic nanoparticles (MNPs) were prepared and used as catalysts for chemiluminescence (CL) system using the luminol-hydrogen peroxide CL reaction as a model. The as-prepared inclusion complexes were characterized by XRD (X-ray diffraction), TGA (thermal gravimetric analysis) and FT-IR. The oxidation reaction between luminol and hydrogen peroxide in basic media initiated CL. The effect of β−CD-based inclusion complexes of CoFe₂O₄ magnetic nanoparticles and naked CoFe₂O₄ magnetic nanoparticles on the luminol-hydrogen peroxide CL system was investigated. It was found that inclusion complexes between β−CD and CoFe₂O₄ magnetic nanoparticles could greatly enhance the CL of the luminol-hydrogen peroxide system. Investigation on the kinetic curves and the chemiluminescence spectra of the luminol-hydrogen peroxide system demonstrates that addition of CoFe₂O₄ MNPs or inclusion complexes between β−CD and CoFe₂O₄ MNPs does not produce a new luminophor of the chemiluminescent reaction. The luminophor for the CL system was still the excited-state 3-aminophthalate anions (3-APA*). The enhanced CL signals were thus ascribed to the possible catalysis from CoFe₂O₄ MNPs or inclusion complexes between β−CD and CoFe₂O₄ nanoparticles. The feasibility of employing the proposed system for hydrogen peroxide sensing was also investigated. Experimental results showed that the CL emission intensity was linear with hydrogen peroxide concentration in the range of 1.0 × 10⁻⁷ to 4.0 × 10⁻⁶ mol L⁻¹ with a detection limit of 2.0 × 10⁻⁸ mol L⁻¹ under optimized conditions. The proposed method has been used to determine hydrogen peroxide in water samples successfully.     

Determination of Four Active Oxygen Species Such as H2O2, •OH, •O2 −, and 1O2 by Luminol and CLA-Chemiluminescence Methods and Evaluation of Antioxidative Effects of Hydroxybenzoic Acids

Abstract

Simple and rapid chemiluminescence (CL) assays for H₂O₂, ?OH, ?O₂ ^? and ¹O₂ using 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol) or 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-α]pyrazin-3-one (CLA) as CL reagents were developed. The means of the intra-assay relative standard deviations of ten replicate measurements of H₂O₂ (25-120 μM), ?OH generated from Fe(II) ion (2.5-10 μM) in the presence of 980 μM H₂O₂, ?O₂ ^? generated from hypoxanthine (HX) (7-50 μM) in the presence of 9 × 10^?3 units xanthine oxidase (XO) and ¹O₂ generated from NaOCl (3-12 mM) in the presence of 97.6 μM H₂O₂ were found to be 4.0%, 2.8%, 2.4% and 8.7%, respectively. To validate the proposed methods, the scavenging abilities of three standard antioxidative compounds, such as L-ascorbic acid, (±)-α-tocopherol and superoxide dismutase (SOD) were examined for four active oxygen species and compared with those by anelectron spin resonance (ESR) spin-trapping method. In addition, the CL methods were also applied to establish the relationships between the decrease of CL intensity and the structures as well as redox characters of syringic acid, 3-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid. From the obtained results, the scavenging effects to H₂O₂, ?OH, ?O₂ ^? and ¹O₂ of other dihydroxybenzoic acids were also evaluated.     

Modulated potential electrogenerated chemiluminescence of luminol and Ru(bpy) 3 2+

Chemiluminescence emission intensity is modulated by modulating the potential of a working electrode which is used to generate a key species in the electrogenerated Chemiluminescence (ECL) reaction. The emission is monitored synchronously using a lock-in amplifier. The reactions used in the characterization are luminol with hydrogen peroxide and tris(2,2-bipyridyl)ruthenium (II) (or Ru(bpy) ₃ ²⁺ ) with oxalate. Modulation widths of ± 50 mV yield maximum signals for luminol when centered at 0.45 V (vs Ag/AgCl) and for Ru(bpy) ₃ ²⁺ when centered at 1.05 V. The resulting signal decreases with increasing modulation frequency and shows that luminol/H₂O₂ is a faster ECL system than Ru(bpy) ₃ ²⁺ /oxalate. Working curves for luminol and for oxalate have essentially the same linear range and slope with the modulated potential approach as with a DC electrode potential. This approach provides capability for differentiating the analytical signal from constant background emission or stray light.     

Multifunctional gold nanoparticles as signal transducers for fabrication of 1:2 molecular demultiplexer

A label-free and enzyme-free demultiplexer system for the fabrication of 1:2 molecular demultiplexer with luminol functionalized gold nanoparticles (Lum-AuNPs) as signal transducers was developed for the first time. The Lum-AuNPs had both chemiluminescence (CL) activity and surface plasmon resonance property. It was found that organothiols (RSH) could easily induce the aggregation of AuNPs via strong Au–S covalent interactions in the absence of hydrogen peroxide (H₂O₂), generating a red shift in the absorption band of AuNPs. However, the presence of H₂O₂ would readily oxidize RSH to disulfide (RS-SR), and the aggregation of Lum-AuNPs did not occur due to lack of the sulfhydryl group. Meanwhile, H₂O₂ could react with Lum-AuNPs, producing a strong CL emission owing to the enhancement effect of RSH on AuNPs-luminol-H₂O₂ CL system. Thus, RSH, H₂O₂, absorbance ratio, and CL intensity served as the signal input, address input, and two different signal outputs of the 1:2 molecular demultiplexer, respectively.     

Determination of NH(3) gas by combination of nanosized LaCoO(3) converter with chemiluminescence detector

Combination of a novel NH₃ converter based on nanosized materials with chemiluminescence (CL) detector for the determination of NH₃ gas was demonstrated in this paper. NH₃ gas is oxidized on different nanosized catalysts to produce NO_x, which can react with luminol to generate CL emission. Eight nanosized materials were investigated as catalyst, and CL was detected from seven of them. The nanosized LaCoO₃ was chosen as the catalyst for preparing the converter because of its higher activity than others. Under the optimized conditions, the linear range of CL intensity versus concentration of NH₃ gas is 0.04-10 ppm (r=0.9951, n=14) with the detection limit of 0.014 ppm. The method offers advantages of long lifetime of the converter, fast response and high selectivity to NH₃. There was no response while the foreign substances, such as hydrogen, oxygen, nitrogen, formaldehyde, acetone and gasoline passing through the CL detection system, and the interference of CCl₄, ethanol, ethylene and toluene was insignificant.     

Host-sensitized emission of LiInW2O8 wolframites: From red-Eu to white-Dy phosphors

The LiInW₂O₈:Eu³⁺, LiInW₂O₈:Dy³⁺ and LiInW₂O₈:Eu³⁺/Dy³⁺ phosphors were synthesized by solid-state reaction and their photoluminescence properties were studied. Under UV excitation, the LiInW₂O₈:Eu³⁺ phosphor exhibits an intense red emission whereas the LiInW₂O₈:Dy³⁺ and LiInW₂O₈:Dy³⁺/Eu³⁺ phosphors show a white emission. The WO₆ octahedra play a major role in the luminescence of the host lattice, characterized by a blue emission under UV excitation. The emission of activator ion results from an efficient energy transfer from the LiInW₂O₈ host lattice to the Eu³⁺ and Dy³⁺ ions. The LiIn_0.97Dy³⁺_0.03W₂O₈ and LiIn_0.965 Dy³⁺_0.03Eu³⁺_0.005W₂O₈ samples, optimized for white emission, are interesting candidates for solid-state lighting applications.     

Diimine ligand as a novel chemiluminescence enhancer of luminol-containing compounds

A series of diimine ligands (DLs) have been synthesized and evaluated for their non-enzymatic chemiluminescence (CL) enhancement of isoluminol or luminol-containing compounds. Of the DLs, N,N’-bis(m-hydroxylbenzylidene)propylenediamine (DL 10) was found to greatly enhance their CLs approximately 40 folds for isoluminol, 10 folds for luminol and 6 folds for a luminol-containing polymer. The CL enhancement of the compounds was observed in the presence of CH₃CN, H₂O₂, tetra-n-propylammonium hydroxide (TPA), and Fe (III) ion. The possible mechanism of this CL enhancement was discussed on the basis of the chelate formation of the ligand and the metal ions.     

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.     

Luminescent dual sensor for time-resolved imaging of pCO2 and pO2 in aquatic systems

An optical dual sensor for the two-dimensional detection of pCO₂ and pO₂ is described. Tris(tetraoctylammonium)-8-hydroxypyrene-1,3,6-trisulfonate ((TOA)₃HPTS) acting together with the lipophilic buffer tetraoctylammonium hydrogen carbonate ((TOA)HCO₃) as pCO₂-sensing system along with the oxygen indicator tris(4,7-diphenyl-1,10-phenanthroline) ruthenium(II) bis(3-(trimethylsilyl)-1-propanesulfonate) (Ru(dpp)₃TMS₂) are incorporated into a single layer ethyl cellulose matrix. A second layer of black silicone rubber served as an optical isolation. The two indicators were simultaneously excited with a 460-nm LED, and a fast-gateable CCD camera was used as the detector. The time-gated imaging scheme enables the mapping of pCO₂ and pO₂ within one measurement, where images in three different time windows during and after a series of square-shaped excitation pulses are recorded. A numerical evaluation method for the resolution of the single parameter maps from these three overall images is described. The response of the sensor has been optimized for use in aquatic systems.     

Effect of eluent composition and pH and chemiluminescent reagent pH on ion chromatographic selectivity and luminol-based chemiluminescence detection of Co, Mn and Fe at trace levels

The alkaline-luminol/H₂O₂-based chemiluminescent (CL) detection of Fe²⁺, Co²⁺, and Mn²⁺, separated with a Dionex CS5A ion chromatographic phase was studied by means of a multi-pump flow system allowing the variation of the post-column solution composition. A perchlorate gradient at pH 1.9 (with HCl) was used to separate cations partially complexed with 5.6 mM oxalate present in the eluent and necessary for the chosen separation phase. A 0.91 mM luminol, 3.3 mM H₂O₂ in 0.25 M carbonate buffer at pH 10.5 composition was chosen as CL reagent solution. The chosen pH value warrants signal repeatability and wider linearity range although absolute signal is not maximum. The CL signal was related to the pH of the two post-column mixing solutions. Calibration plots of Co²⁺ and Fe²⁺ were linear in the chosen concentration range whilst a parabolic model was the best fit for Mn²⁺. Detection limits were 0.24, 0.50 and 375 nM for Co²⁺, Fe²⁺ and Mn²⁺, respectively. The method was used to determine Co²⁺ at trace level in commercial copper chelates used for animal feeding. A comparison with a chromatographic method with spectrophotometric detection was made giving results comparable both in absolute values and accuracy.     

A nanosized Y(2)O(3)-based catalytic chemiluminescent sensor for trimethylamine

The development of a catalytic chemiluminescent trimethylamine (TMA) sensor is demonstrated in the present paper. Intensive chemiluminescence (CL) is detected when TMA is introduced over the surface of nanosized catalysts and subsequently catalytically oxidized by O₂ from the air, and four catalysts are investigated with the strongest CL intensity obtained on nanosized Y₂O₃. This effect is utilized to develop a novel nanosized Y₂O₃-based catalytic CL sensor for TMA which under optimal conditions exhibits a wide linear range of 60-42,000 ppm and a detection limit of 10 ppm. An attractive advantage of this novel CL sensor is its high selectivity to TMA with negligible responses to many other gases such as NH₃ and organic vapors. This CL sensor has a short response time of less than 3 s, and shows good stability when examined by continual introduction of TMA into the sensor for 96 h. The applicability of this sensor to actual fish samples is also demonstrated in the paper.     

Enhanced chemiluminescence of the luminol–KIO4 system by ZnS nanoparticles

The chemiluminescence (CL) intensity of the luminol–KIO₄ system is strongly enhanced by addition of zinc sulfide nanoparticles (ZnS-NPs) capped with 3-mercaptopropionic acid. On injection of fluoroquinolones into the luminol–KIO₄–ZnS–NP system, CL intensity is substantially increased. The CL emission peaks at 430 nm, thus indicating that the luminophore is 3-aminophthalate. The enhancement effect is attributed to a catalytic effect of the ZnS-NPs, which is assumed to accelerate the electron transfer process and to facilitate radical generation. Based on theses findings, a sensitive CL assay was developed for several fluoroquinolones.     

Evaluation of peroxide value of olive oil and antioxidant activity by luminol chemiluminescence

Three procedures are developed and investigated for the simple and fast determination of peroxide value of olive oil by luminol chemiluminescence. The procedure using hemin as catalyst in carbonate alkaline solution allows the determination of hydrogen peroxide within the range 0.014-50 μM. The method can be used for the determination of peroxide value within the range 2.00-30.0 mequiv. O₂/kg oil and results correlate very well (r² = 0.99) with those of the official method. All reagents are aqueous solutions and olive oil is dissolved in acetone:ethanol mixed solution and, hence, the method is using minimal amounts of organic solvents and can be successfully applied to field analysis. Antioxidant activity of five common compounds found in natural products was determined by using luminol CL with Co(II) as EDTA complex as catalyst at pH 9.00.     

Simultaneous quantification of catecholamines in rat brain by high‐performance liquid chromatography with on‐line gold nanoparticle‐catalyzed luminol chemiluminescence detection

A new method based on high‐performance liquid chromatography (HPLC) coupled with on‐line gold nanoparticle‐catalyzed luminol chemiluminescence (CL) detection was developed for the simultaneous quantitation of catecholamines in rat brain. In the present CL system, gold nanoparticles were produced by the on‐line reaction of H₂O₂, NaHCO₃?Na₂CO₃ (buffer solution of luminol) and HAuCl_4. Norepinephrine (NE), epinephrine (EP) and dopamine (DA) could strongly enhance the CL signal of the on‐line gold nanoparticle‐catalyzed luminol system. The UV?visible absorption spectra and transmission electron microscopy studies were carried out, and the CL enhancement mechanism was proposed. Catecholamines promoted the on‐line formation of more gold nanoparticles, which better catalyzed the luminol–H₂O₂ CL reaction. The good separation of NE, EP and DA was achieved with isocratic elution using a mixture of methanol and 0.2% aqueous phosphoric acid (5:95, v/v) within 8.5 min. Under the optimized conditions, the detection limits, defined as a signal‐to‐noise ratio of 3, were in the range of 1.32–1.90 ng/mL, corresponding to 26.4?38.0 pg for 20 μL sample injection. The recoveries of catecholamines added to rat brain sample were >94.6%, with the precisions <5.5%. The validated HPLC?CL method was successfully applied to determine NE and DA in rat brain without prior sample purification. Copyright © 2014 John Wiley & Sons, Ltd.     

Sensitive chemiluminescence method for the determination of glutathione, l-cysteine and 6-mercaptopurine

Glutathione (GSH), l-cysteine (l-Cys) and 6-mercaptopurine (6-MP) inhibit the CL reaction of luminol–H₂O₂ catalyzed by gold colloids. In order to explore this, GSH, l-Cys and 6-MP were injected into the chemiluminescence system of luminol and H₂O₂ catalyzed by gold colloids. The results showed that gold colloids interact with GSH, l-Cys and 6-MP and decrease the CL emission. Based on this phenomenon, a simple, sensitive and convenient flow injection CL method was developed for the determination of GSH, l-Cys and 6-MP. This method provides a novel, and effective CL assay for GSH, l-Cys and 6-MP that has been applied to the determination of GSH in human serum.     

Sol hydrolysis and condensation reaction time influence the sensitivity of class II xerogel-based sensing materials

Simplicity of preparation, a wide variety of precursors, and numerous processing variables (e.g., pH, time, temperature) are often described as attractive aspects of sol–gel derived materials. In the current work we create a series of O₂-responsive xerogel-based sensor films by simultaneously co-hydrolyzing and co-condensing tetramethylorthosilane and n-octyltriethoxysilane. Tris(4,7′-diphenyl-1,10′-phenanthroline) ruthenium(II) ([Ru(dpp)₃]²⁺) is used as the O₂-responsive luminophore. We determine the effects of [Ru(dpp)₃]²⁺ addition time to the sol and the sol hydrolysis and condensation reaction time (H&C) on the xerogel film O₂ sensitivity. [Ru(dpp)₃]²⁺ addition time has no significant effect on the O₂ sensitivity; H&C effects the O₂ sensitivity. The highest O₂ sensitivity is seen at early H&C (0.5 h). This behavior arises because TMOS and C8-TMOS react at different rates to form sols. At early H&C the co-hydrolysis and co-condensation reactions are not complete and the so formed sols are rich in C8-TMOS in comparison to their composition at longer H&C. At longer H&C, the TMOS and C8-TMOS co-hydrolyze and co-condense more completely. SEM images show that xerogel films formed at early H&C is more porous in comparison to those formed a longer H&C. The results of these experiments: (a) highlight the importance of documenting how sols are processed and xerogels formed and (b) demonstrate the use of a single sol formulation and H&C to create suites of sensor materials with different responses.     

Chemiluminescence of Colloidal MnO2 with Luminol and Determination of Polyhydroxyl Compounds

The reaction between luminol and colloidal MnO₂ (prepared by chemical reduction of KMnO₄ with Na₂S₂O₃ under neutral aqueous condition) produced an intense chemiluminescence (CL) emission in alkaline medium. The CL reaction conditions were carefully optimized and the CL reaction mechanism was thoroughly discussed. Manganese(III) was suggested to be involved in the reaction and 3‐aminophthalate anion was the luminophor. Moreover, the effects of 23 compounds on the colloidal MnO₂‐luminol CL system were investigated to explore its possible analytical applications. Polyhydroxyl compounds were observed to inhibit the signal significantly, whereas sulfhydryl compounds enhance it slightly. The analytical figures for five polyhydroxyl compounds, namely ascorbic acid, rutin, pyrogallol, quercetin, and L‐adrenaline, were presented. As a preliminary application, the method was applied to the determination of rutin in pharmaceutical formulations.