Stopped-flow study of the enhanced chemiluminescence for the oxidation of luminol with hydrogen peroxide catalyzed by microperoxidase 8

The presence of carbonate or Tris causes a dramatic enhancement in the cheminluminescence (CL) for the oxidation of luminol with hydrogen peroxide catalyzed by microperoxidase 8 (MP8). A nearly constant enhancement in CL was observed over a wide range of H₂O₂ and luminol concentrations. The enhancement in CL is strongly pH-dependent, varying from 1.3 to 22.2 for carbonate and 1.6 to 10.2 for Tris. The CL enhancement is much more prominent at pH 9-10 than at high pH (>10.5) because of the extremely weak CL emission at pH below 10 when no enhancer is present. The CL enhancement is attributed to an accelerated CL cycle and the existence of alternative routes for luminol CL, possibly involving the carbonate, or Tris radicals. The dramatic enhancement in CL of the MP8-luminol-H₂O₂ system by the readily available reagents, sodium carbonate or Tris, will have general applications for sensitive CL assays. As an example, the presence of antioxidant results in a diminished and delayed CL emission, allowing the determination of its concentration at sub-micromolar level.     

Determination of hydrogen peroxide in a flow system with microperoxidase as catalyst for the luminol chemiluminescence reaction

Hydrogen peroxide is determined by a chemiluminescence method with a reagent containing 100 μM luminol and 3 μM microperoxidase at pH 10 (carbonate buffer). Microperoxidase is superior to hematin as a catalyst. The method uses an automated flow injection system with a throughput of 2 samples per minute. The log—log calibration plot is linear (slope 1.3) from the detection limit, 3 × 10^-9 M up to 10^-5 M H₂O₂. The background emission is low. Impurities in the carrier stream and from some plastics may cause elevated background unless precautions are taken.     

Evaluation of ferryl formation by electrocatalytic oxidation of alkene using luminol chemiluminescence

Electrochemical formation of ferryl porphyrin was examined by electrocatalytic oxidation of alkene by measuring luminol chemiluminescence using a flow-injection method. Emission was observed both below the reduction potential of Fe(III)TMPyP (-0.08 V at pH 11, -0.02 V at pH 7 and 0.15 V at pH 3) and above the oxidation potential (0.6 V at pH 11, 0.75 V at pH 7 and 1.1 V at pH 3). However, both anodic and cathodic emissions were inhibited significantly by the addition of alkene (cyclopent-2-ene-1-acetic acid) solutions downstream of the working electrode. Further, the spectra at both anodic and cathodic sides shifted to the longer wavelength (>424 nm) compared to the original spectrum of Fe(III)TMPyP (422 nm), which was not observed with the addition of alkene solution. Therefore, the results suggest that the electrochemically generated oxo-ferryl species have been engaged in catalytic oxidation of alkene before the flow reaches the observation cell.     

Determination of thyroxine hormone by luminol chemiluminescence

A chemiluminescence (CL) flow system for determination of thyroxine (Thy) is presented. It is based on the catalytic effect of cobalt(II) on the CL reaction between luminol and hydrogen peroxide. The iodinated chemical structure of Thy causes a heavy atom effect. The luminol CL signals show significant quenching by Thy. The calibration graph for Thy is linear for 15-70 μg ml⁻¹ and the 3σ detection limits are 27 μg ml⁻¹ for d-Thy and 23 μg ml⁻¹ for l-Thy.     

Photographic homogeneous immunoassay based on luminol chemiluminescence catalyzed by hemoglobins leaked from complement-hemolyzed red blood cells

Summary Human serum albumin (HSA) and complement were photographically assayed. The complement activated by the formed antigen-antibody complex causes the hemolysis of red blood cells. Leaked hemoglobins catalyze the chemiluminescent reaction of luminol and hydrogen peroxide (H₂O₂). The resulting emission was recorded on instant film.     

Enhancement of luminol chemiluminescence by cysteine and glutathione

Cysteine enhancement of cobalt(II)-catalysed chemiluminescence of hydrogen peroxide and luminol occurs in carbonate buffer (but not in borate buffer), whether cysteine mixes with hydrogen peroxide before it mixes with luminol-cobalt(II) or vice versa. Enhancement was measured by the ratio of the signals in the presence and absence of cysteine; standard errors were generally < 5% of the mean ratio. Cystine in sufficiently acidic solution also enhances the chemiluminescence but otherwise diminishes the emission. The emission is also inhibited by glutathione. A mixed solution of cysteine and cystine gives rise to enhanced signals. In all the above cases, enhancement occurs only in the presence of a cobalt(II) catalyst. Luminol-peroxynitrite chemiluminescence is enhanced by cysteine and by glutathione without the presence of a catalyst.     

Chemiluminescence of luminol catalyzed by silver nanoparticles

Silver nanoparticles (AgNPs) are synthesized by chemical reduction method and characterized by UV-vis spectra, transmission electron microscopy, and high performance particle sizer. We have found that AgNPs could enhance the chemiluminescence (CL) intensity of luminol-H(2)O(2) system. In this reaction, luminol intermediate is generated under alkaline condition on the surface of AgNPs in luminol-H(2)O(2) system and enhances CL intensity. To validate the reaction mechanism, AgNPs are bound with thioglycolic acid (Ag-HSCH(2)COOH) and then joined to BSA protein (Ag-BSA). We investigate the CL intensity in the presence of Ag-HSCH(2)COOH or Ag-BSA comparing with that in the presence of AgNPs and conclude the catalytic reaction take place on the surface of AgNPs.     

Peroxidase-catalysed luminol chemiluminescence method for the determination of glutathione

A luminol chemiluminescence (CL) method was developed for the determination of glutathione (GSH). GSH was indirectly determined by measuring the amount of hydrogen peroxide formed during the Cu(II)-catalysed oxidation of GSH with oxygen. The amount of hydrogen peroxide formed was continuously measured using the Arthromyces ramosus peroxidase-catalysed luminol CL reaction. The CL intensities at maximum light emission were linearly correlated with the concentration of GSH over the range 7.5 x 10(-7)-3.0 x 10(-5) M. The detection limit for GSH was about 10 times better than that of the spectrophotometric method using Ellman reagent.     

Determination of carbaryl by flow injection with luminol chemiluminescence inhibition detection

A flow-injection procedure is described for the determination of carbaryl based on its inhibition effect on luminol-cobalt(II) chemiluminescence reaction in alkaline medium in the presence of hydrogen peroxide. The calibration data over the range 5.0?×?10^?7 to 20?×?10^?6?M give a correlation coefficient (r ²) of 0.9972 with relative standard deviations (RSD; n?=?4) in the range of 1.0–2.1% with a limit of detection (3?×?blank noise) of 2.37?×?10^?7?M for carbaryl. The sample throughput was 120?h^?1. The effects of some carbamates, anions, and cations were studied on luminol CL system for carbaryl determination. The proposed method has been applied to determine carbaryl in natural waters.     

A flow injection chemiluminescence method for the determination of fluoroquinolone derivative using the reaction of luminol and hydrogen peroxide catalyzed by gold nanoparticles

Based on the enhancement of chemiluminescence (CL) of luminol-hydrogen peroxide-gold nanoparticles system by fluoroquinolones (FQs), a novel and rapid CL method is reported for the determination of FQs derivatives. Under the optimum conditions, the CL intensity is proportional to the concentration of FQs derivative in solution. The corresponding linear regression equations are established over the range of 0.08-1.28 μg/mL for norfloxacin, 0.013-1.32 μg/mL for ciprofloxacin, 0.014-1.4 μg/mL for lomefloxacin, 0.029-1.46 μg/mL for fleroxacin, 0.02-1.0 μg/mL for ofloxacin and 0.01-1.44 μg/mL for levofloxacin, respectively. The limits of detection (S/N = 3) are 3.2, 9.5, 7.0, 9.0, 8.0, and 8.0 ng/mL with the relative standard deviation (n = 11) 4.3, 1.5, 1.9, 1.3, 1.6 and 2.1% for norfloxacin, ciprofloxacin, lomefloxacin, fleroxacin, ofloxacin and levofloxacin, respectively. This proposed method has been applied to detect FQs derivatives in human urine successfully.     

Silicon-hybrid carbon dots strongly enhance the chemiluminescence of luminol

We report on a 4-min microwave pyrolytic method for the preparation of fluorescent and water-soluble silicon-hybrid carbon dots (C-dots) with high fluorescent quantum yield. The material is prepared by preheating aminopropyltriethoxysilane and ethylene diamine tetraacetic acid for 1 min, then adding a mixture of poly(ethylene glycol) and glycerin to the solution and heating for another 3 min. It is found that the hybrid carbon dots strongly enhance the chemiluminescence (CL) of the luminol/N-bromosuccinimide system. A study on the enhancement mechanism via CL, fluorescence and electron paramagnetic resonance spectroscopy showed that the effect most probably is due to electrostatic interaction between the C-dots and the luminol anion which facilitates electron transfer from luminol anion to the N-bromosuccinimide oxidant. CL intensity is linearly related to the concentration of the C-dots in the range between 1.25 and 20 μg mL^?1. The detection limit is 0.6 μg mL^?1 (at an S/N of 3).

鲁米诺-铁氰化钾化学发光体系测定左旋多巴

铁氰化钾在碱性条件能氧化鲁米诺而发光,左旋多巴能大大增强该发光强度。基于此现象并结合流动注射技术,建立起一种直接测定左旋多巴的流动注射化学发光分析法。方法检出限为1.2×10-10g mL,左旋多巴质量浓度在5 0×10-10～5.0×10-8g mL范围内与发光强度呈良好的线性关系。相对标准偏差为2.9%(左旋多巴5.0×10-9g mL,n=11)。该方法可用于片剂中左旋多巴量的测定。     

Enhanced enantioselective oxidation of olefins catalyzed by Mn-porphyrin immobilized on graphene oxide

An efficient enantioselective heterogeneous catalyst, GO-[Mn(TPyP)tart], was prepared by covalent attachment of Mn(III) complex of H₂TPyP via the propyl linkage to graphene oxide (GO) nanosheet and using chiral tartrate counter ion. The catalyst was characterized by Fourier transform infrared (FT-IR), diffuse reflectance ultraviolet–visible (DR UV–Vis) spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and thermogravimetric analysis (TGA). The graphene-supported Mn-porphyrin showed higher activity for the enantioselective epoxidation of unfunctionalized olefins with molecular oxygen in the presence of isobutyraldehyde. It could be recovered easily and reused in asymmetric oxidation of styrene precursor in a five-step sequence without any considerable loss of its catalytic activity and selectivity. The obtained optically epoxide selectivities were achieved in 86% to 100%.     

Apparatus for mechanistic and analytical studies of the electrogenerated chemiluminescence of luminol

A new apparatus based on the rotating ring—disc electrode system is described. The symmetric double-step potential is connected to the ring electrode to oxidize luminol, while the disc electrode is maintained at a negative potential to reduce oxygen to hydrogen peroxide. Because of the electrode rotation, hydrogen peroxide is immediately transported to the ring electrode at which it reacts with luminol oxidation product to emit light. Preliminary electrogenerated chemiluminescence measurements indicate that the intensity of the chemiluminescence of luminol is highly dependent on the ring and disc electrode materials and that some metal ions have a catalytic or inhibitive effect on this luminescence reaction of luminol.     

Photodegradation and flow-injection determination of simetryn herbicide by luminol chemiluminescence detection

A novel and simple flow injection chemiluminescence method is reported for the determination of simetryn, a common herbicide. The method is based on the direct oxidation of luminol by the photoproducts of the simetryn in alkaline medium in the absence of catalyst/oxidant. The linear concentration range was 0.01 - 2 microg mL(-1) simetryn with a correlation coefficient (r(2)) of 0.9997 and relative standard deviations (RSD; n = 4) in the range of 0.9 - 2.3%. The limit of detection (S/N = 3) was 7.5 ng mL(-1) with a sample throughput of 100 h(-1). The proposed method has been applied to determine simetryn in natural waters using Sep-Pak C(18) cartridges for solid phase extraction (SPE) procedure. The recoveries were in the range of 97 +/- 1 to 104 +/- 2%. The mechanism of chemiluminescence reaction has also been discussed briefly.