Updating the Chemiluminescence Oxygen‐Aftereffect Method for Determining the Rate Constant of the Peroxy‐Radical Self‐Reaction: Oxidation of Cyclohexene

Updating the facile chemiluminescence oxygen‐aftereffect method, most suitable for determining the rate constant (k_t) of the peroxy‐radical self‐reaction (main chemiluminescence channel), pertained to considering the sensitivity of such a method toward a disturbing influence of the peroxy radicals of the initiator of the chain oxidation process. Such a disturbance may derive from the side chemiluminescent reaction, which involves peroxy radicals of both hydrocarbon and initiator. To examine the applicability and limitations of the chemiluminescence method under present scrutiny, cyclohexene was used as the model oxidizable hydrocarbon substrate. Computer simulations of the reaction and chemiluminescence kinetics have demonstrated the validity of the considered methodology at the value of the rate constant of the propagation of the overall chain process by peroxy radicals of the initiator higher than 1 m ^?1 s^?1. Despite that the chemiluminescence time profile and the stationary level of the total chemiluminescence intensity depend on the kinetics of the side chemiluminescence channel and on the ratio of the excited‐state generation yields in the mentioned reaction channel and in the main chemiluminescence process, the value of k_t assessed by the oxygen‐aftereffect method has been found independent of variation of these characteristics.     

Enhanced Sensitivity of the Tris(Bipyridine)Ruthenium(II) Chloride Electrogenerated Chemiluminescence Sensor with Porous Silica Nanoparticles

Mass transfer in electrogenerated chemiluminescence affects the sensitivity of sensors involving this technique. Herein, the characteristics of the porous Ru(bpy)₃²⁺/silica nanoparticles were investigated by transmission electron microscopy, fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, and electrogenerated chemiluminescence. The results showed that the pores inside the porous nanoparticles provided efficient mass transfer, resulting in significant enhancement of electrogenerated chemiluminescence. Consequently, a novel electrogenerated chemiluminescence sensor was developed and is reported herein. The sensitivity for tripropylamine was more than one order of magnitude higher compared to previously reported similar sensors, with a limit of detection of 3.3 × 10^?12 moles per liter.     

Enhancing effect of DNA on chemiluminescence from the decomposition of hydrogen peroxide catalyzed by copper(II)

In the absence of any special luminescence reagent, emission of weak chemiluminescence has been observed during the decomposition of hydrogen peroxide catalyzed by copper(II) in basic aqueous solution. The intensity of the chemiluminescence was greatly enhanced by addition of DNA and was strongly dependent on DNA concentration. Based on these phenomena, a flow-injection chemiluminescence method was established for determination of DNA. The chemiluminescence intensity was linear with DNA concentration in the range 2×10^–7–1×10^–5 g L^–1 and the detection limit was 4.1×10^–8 g L^–1 (S/N=3). The relative standard deviation was less than 3.0% for 4×10^–7 g L^–1 DNA (n=11). The proposed method was satisfactorily applied for determination of DNA in synthetic samples. The possible mechanism of the CL reaction is discussed.     

Chemiluminescence system of Ce(IV)-RhB-bismerthiazol

A novel chemiluminescence system for the determination of bismerthiazol is first described in this paper. It is based on the chemiluminescence reaction of bismerthiazol and Ce(IV) in nitric acid solution. The emission intensity could be enhanced greatly by Rhodamine B. The chemiluminescence intensity was proportional to bismerthiazol concentration over the range 30–1000 μg/L. The detection limit was 12 μg/L (3σ) and the relative standard deviation is 2.4% for 500 μg/L of bismerthiazol (n = 11). The proposed method was successfully applied to the determination of bismerthiazol in water and in rice. The recovery was 96.4%–104.1%. __________ Translated from Chinese Journal of Applied Chemistry, 2007, 24(5): 593–595     

Rapid Flow-Injection Method for the Determination of Colistin by Sensitized Chemiluminescence Using the Acidic Permanganate–Sulfite System

Abstract

A simple, rapid, and sensitive chemiluminescence method for the determination of colistin (Polymyxin E), a cyclic polypeptide with antibiotic effect produced by certain strains of Bacillus polymyxa, has been developed by combining a flow-injection technique and the bacteria's sensitizing effect on the chemiluminescence reaction between sulfite and acidic permanganate. The optimum conditions for chemiluminescence emission were established. The chemiluminescence was proportional to the log of concentration of colistin over the range 4–100 µg mL^?1 (3.5–87 µM). The detection limit was 1.2 µg mL^?1 (1.0 µM) of colistin. The method has been satisfactorily used for the determination of colistin in pharmaceuticals.     

Quantification of fenfluramine with a molecularly imprinted chemiluminescence sensor and sulfonophenylazo rhodanine

Fenfluramine-imprinted polymer was prepared by self assembly with acrylic amide as functional monomer and ethylene glycol dimethacrylate as crosslinker. The binding characteristics of the imprinted polymer to fenfluramine were evaluated by equilibrium binding experiments and the morphology was studied by SEM. Taking the imprinted polymer as recognition material, using the new 3-p-nitrylphenyl-5-(4′-methyl-2′-sulfonophenylazo)rhodanine (M4NRASP) synthesized by the authors as chemiluminescence reagent, a new highly selective flow injection chemiluminescence sensor for trace fenfluramine with good sensitivity was established which utilized the chemiluminescence reaction between fenfluramine, M4NRASP, and potassium permanganate in hydrochloric acid. The traditional flow-through cell was replaced with a polymethyl methacrylate module, with Y-shaped flow path, through which the above three reactants were injected simultaneously. Under optimum conditions the relative chemiluminescence intensity shows a linear relationship with the concentration of fenfluramine over the range of 5×10^–7 to 8×10^–6 g/mL with a lower detection limit of 3.4×10^–8 g/mL. The relative standard deviation for the determination of 1.0×10^–6 g/mL fenfluramine solution was 2.4% (n = 11). This proposed sensor could be satisfactorily applied to the determination of fenfluramine in weight-reducing capsules.     

A Chemiluminescence Reaction Between Hydroxyl Radical and Rhodamine 6G and its Applications

Abstract

A novel chemiluminescence (CL) reaction between hydroxyl radical and ascorbic acid is described in this paper. Hydroxyl radical generated on line by the reaction between Fe³⁺ solution and H₂O₂ solution in HCl medium could oxidize rhodamine 6G to produce weak chemiluminescence. It was found that ascorbic acid could enhance the chemiluminescence and the excited rhodamine 6G was the emitter of the chemiluminescence reaction. The possible mechanism of the CL system was also discussed. Ascorbic acid can be determined in the range of 2.0×10^?6?8.0×10^?4 mg/ml with a detection limit of 1×10^?6 mg/ml (3σ). A complete analysis could be done in 1 minute with the relative standard deviation of 3.1% for 5.0×10^?5 mg/ml (n=11). In order to study the chemiluminescence reaction further, the application to the determination of ascorbic acid in food using the chemiluminescence reaction combined with flow injection is investigated.     

Larval Tenebrio molitor (Coleoptera: Tenebrionidae) Fat Body Extracts Catalyze Firefly D-Luciferin- and ATP-Dependent Chemiluminescence: A Luciferase-like Enzyme*

Ultraweak light emission was detected upon injection of firefly luciferin into live Tenebrio larvae. A chemilumi-nescent enzymatic activity dependent on molecular oxygen, D-luciferin and MgATP was then isolated from larval fat body extracts by precipitation with 70% ammonium sulfate. D-Luciferin and ATP can be replaced by luciferyl-adenylate. Pyrophosphate is a main product from the chemiluminescent reaction. The in vitro chemiluminescence intensity was not affected by peroxidase inhibitors such as N₃^?_- (0.5 mM) and CN^? (1 mM), attesting to its nonperoxidatic nature but was strongly inhibited by AMP (1 mM), luciferin 6′-ethyl ether (1 mM) and sodium pyrophosphate (2 mM), well-known firefly lucifer-ase inhibitors. Some physical-chemical properties of this enzymatic activity were similar to those of firefly lucif-erase (K_MATP = 195 μM; K_0.5 luciferin - 0.8 mM; optimum pH 8.5; δ_max= 610 nm at pH 8.5; firefly lucifer-ase: δ_max= 565 nm at pH 8.0 and 619 mm at pH 6.0), but the chemiluminescence was not affected by addition of polyclonal antibodies raised against Photinus pyralis luciferase. These data suggest that this chemiluminescence results from a ligase with luciferase activity.     

Determination of superoxide dismutase and SOD-mimetic activities by a chemical system: Co2/H2O2/lucigenin

The bright chemiluminescence has been observed in the system: Co²⁺/hydrogen peroxide/lucigenin. The chemiluminescence intensity was directly proportional to either cobalt, hydrogen peroxide, or lucigenin concentrations. A procedure of determination of superoxide dismutase (SOD) activity by the chemiluminescence method in the cobalt–hydrogen peroxide–lucigenin system at pH 8.5 is suggested. A linear dependence was established between a relative chemiluminescence intensity and SOD concentration in the range of SOD concentrations between 0 and 4.5 nM, c _1/2 = 0.8 nM. The determination of SOD activity was performed in several tissue samples (rat plasma, erythrocyte hemolysate, and liver mitochondria). A technique of tissue sample preparation with the use of thermal inactivation of interfering proteins at 60 °C was used. The method was successfully applied for comparison of the efficiency of SOD mimetics.     

CHEMILUMINESCENCE and EPR STUDIES ON THE EXCITATION SITE OF FERRIC-HEME-OXO COMPLEXES OF NATURAL and MODEL HEME SYSTEMS

Chemiluminescence was detected both in the reaction system of H₂O₂ plus heme proteins such as methemo- and metmyoglobin and ferric-protoheme complexes used as a model system. The intensity of chemiluminescence was found to be mediated by ligand binding to the sixth coordination site of the ferric-protoheme compounds, e.g. chemiluminescence was not observed with the bisimidazole ferric-protoheme complex. On the other hand the pentacoordinated histidine ferric-protoheme complex exhibited strong light emission. Comparative studies with various ligand-heme compounds elucidated that light emission was inversely correlated with the binding strength of the respective ligand at the sixth coordination site. The basic reaction mechanism causing the establishment of an excited state was studied by monitoring chemiluminescence and EPR signal formation of ligand-modified heme proteins in the presence of different electron donors. External electron donors such as Trolox C, TMPD and ascorbic acid affected a strong reduction in the development of chemiluminescence suggesting the essential involvement of an inner-molecular electron transfer process. Our results allow the conclusion that chemiluminescence is generated from the decay of an excited state of oxo-heme compounds established as a result of a one electron transfer step from a ligand group to heme iron.     

Determination of Antioxidant Activity of Hibiscus Flowers by Flow Injection Analysis with Chemiluminescence Detection

This study reports a simple and rapid method for the determination of the antioxidant activity of the phenolics present in plants of the Hibiscus genus. The protocol is based on the ability of the phenolic compounds to inhibit luminol chemiluminescence through the inactivation of free radicals in a flow injection system. Using the optimized operational conditions, the antioxidant activities of several phenolics were measured. The results were explained on the basis of structure–reactivity relationships. The antioxidant activities of dried flowers of Hibiscus rosa-sinensis and Hibiscus sabdariffa were evaluated. The protocol was validated by the 2,2-diphenyl-1-picrylhydrazyl-hydrate free radical assay. The differences in the antiradical activities were explained based on the concentrations of total polyphenol and flavonoid concentrations determined by spectrophotometric methods. It was concluded that the chemiluminescence method was complementary for the evaluation of hydrophilic antioxidants in plants.     

Rapid determination of levofloxacin in pharmaceuticals and biological fluids using a new chemiluminescence system

A novel chemiluminescence method for the determination of levofloxacin is presented, which is based on the inhibitory effect of levofloxacin on the chemiluminescence reaction between luminol and myoglobin in a flow-injection system. The decrement of chemiluminescence intensity is linear with the logarithm of levofloxacin concentration over the range from 0.07 to 100.0 ng/mL (r ² = 0.9994), with the detection limit of 0.02 ng/mL (3σ). At a flow rate of 2.0 mL/min, a complete analytical process could be performed within 0.5 min, including sampling and washing, with a relative standard deviation of less than 3.0% (n = 5). The proposed procedure was applied successfully to the determination of levofloxacin in pharmaceutical preparations, human urine and serum without any pretreatment procedure.     

Chemiluminescence mechanisms of cerium-norfloxacin and its application in urine analysis

In this article, novel chemiluminescence mechanisms between norfloxacin and cerium(IV) in an acidic medium were studied. Chemiluminescence spectra of the present system were recorded observing three maximum emissions at about 475 nm, 550 nm, and 620 nm, respectively. The results indicate that the chemiluminescence peaks located at 475 nm and 620 nm can be ascribed to the emission of a singlet oxygen, while the chemiluminescence emission at 550 nm occurred in course of the reaction between acidic cerium(IV) and the phenolic intermediate. Under optimum conditions, the chemiluminescence intensity was linear with the concentration of norfloxacin over the range of 2.0 × 10⁻⁸−1.0 × 10⁻⁵ g mL⁻¹ and the detection limit of 1.0 × 10⁻⁸ g mL⁻¹ (S/N = 3). The relative standard deviation was 1.94 % for a 4.0 × 10⁻⁷ g mL⁻¹ norfloxacin solution considering eleven repeated measurements. The present chemiluminescence system was successfully applied in the determination of norfloxacin in pharmaceutical preparations and concentration-time profiles in urine.     

Assay of femtogram level nitrite in human urine using luminol–myoglobin chemiluminescence

In this paper, a sensitive flow injection chemiluminescence system luminol–myoglobin was described for determining femtogram nitrite. Nitrite bound myoglobin producing the ferric heme nitrite complexes, which catalyzed the electron transfer of luminol to myoglobin leading to fast chemiluminescence. The chemiluminescence intensity in the presence of nitrite was remarkably enhanced compared with that in the absence of it. Under the optimum reaction conditions the chemiluminescence increment produced was proportional to the concentration of nitrite in the range of 0.05 pg ml^− 1–1.0 ng ml^− 1 (R² = 0.9991), with a detection limit (3σ) of 20.0 fg ml^− 1. At the flow rate of 2.0 ml min^− 1, the whole process including sampling and washing could be completed in 0.5 min offering the sampling efficiency of 120 h^− 1 accordingly, and the relative standard deviation (RSD) was less than 2.60% (n = 5). It was satisfactory for the application to determine nitrite in human urine samples, and the possible mechanism was proposed.     

Determination of arsenic(V) in freshwaters by flow injection with luminol chemiluminescence detection

A simple and rapid flow injection (FI) method is reported for the determination of arsenic(V) based on luminol chemiluminescence (CL) detection. The molybdoarsenic heteropoly acid formed by arsenic and ammonium molybdate in the presence of ammonium vanadate in acidic conditions generated chemiluminescence emission via the oxidation of luminol. The limit of detection was 0.15 μg L^?1, with a sample throughput 120 h^?1. A linear calibration graph was obtained over the range 0.15 to 7.5 μg L^?1 (r ² = 0.9989; n = 9) with relative standard deviation (n = 4) in the range 0.8 to 2.5%. Interfering cations were removed by passing the sample through an in-line iminodiacetate chelating column and phosphate (at 0.6 mg L^?1) was removed off-line by magnesium-induced coprecipitation (MAGIC) method. The method was applied to freshwater samples and the results obtained were in reasonable agreement with the results obtained using HGAAS as the reference method.     

Chemiluminescence determination of <Emphasis Type="Italic">o</Emphasis>-chlorobenzylidenemalonic acid dinitrile in extracts

A chemiluminescence method was developed for determining o-chlorobenzylidenemalonic acid dinitrile (o-CBMA DN) in extracts. The method is based on chemiluminescence developed in a strong alkaline solution upon the interaction between 3-aminophthalic hydrazide (luminol) with the superoxide radical formed in the reaction of atmospheric oxygen activated by hemin with the products of the alkaline hydrolysis of o-chlorobenzylidenemalonic acid dinitrile and with the products of their condensation with p-nitrobenzaldehyde. The luminescence intensity of luminol was proportional to the concentration of o-CBMA DN in the range 1 × 10⁻⁶−1 × 10⁻¹ mg/mL. The determination limit for o-CBMA DN was (1 ± 0.3) × 10⁻⁶ mg/mL (p = 95%, n = 5, RSD = 29%) at 293 K.     

Stopped-flow microarray immunoassay for detection of viable <Emphasis Type="Italic">E. coli</Emphasis> by use of chemiluminescence flow-through microarrays

Rapid multiplexed analysis of microorganisms is important in water analysis to control bacterial contamination for health and safety reasons. Direct quantification of bacteria by means of flow-through microarray immunoassays requires new analysis strategies for optimising sensitivity and the analysis time. For bacteria and for particles, hydrodynamic forces and sedimentation are the dominating effects for binding on surfaces in a flow-through system, whereas diffusion is insignificant. Therefore, we have implemented a stop and flow technique for quantification of viable E. coli cells. The method, with alternation of resting volume elements and pumping the elements forward, was more effective than continuous-flow approaches for analysis of bacteria. For quantification of viable E. coli cells, a chemiluminescence sandwich immunoassay test format was performed by means of antibody microarrays and flow-injection-based microarray analysis. Antibodies, which served as selective capture molecules, were immobilised on polymer-modified glass surfaces serving as microarray substrate. For the bacteria recognition step, a second detection antibody was used, forming a sandwich immunoassay at each spot of the microarray. Detection was carried out with a horseradish peroxidase catalysed chemiluminescence reaction. All assay steps were conducted with an automated flow-through chemiluminescence microarray readout system. Living E. coli cells could be detected in 67 min with a detection limit of 4 × 10⁵ cells mL⁻¹. By introduction of the stopped-flow technique and optimisation of interaction time and interaction steps the achieved detection of E. coli was faster and two orders of magnitude more sensitive than with a conventional ELISA technique in microplates.     

Application of Pulsed Flow Analysis for Chemiluminescent Screening of Fluoxetine Counterfeit Pharmaceuticals

Abstract

A chemiluminometric methodology for fluoxetine determination based on its antioxidant scavenger effect on the fast chemiluminescence reaction between luminol and hypochlorite, is proposed. The developed procedure was implemented in a fully automated multi‐pumping flow system, combining the excellent mixing characteristics of the pulsed flow with chemiluminescence detection, resulting on a sensitive, simple, and fast procedure for fluoxetine determination in pharmaceutical formulations. Linear calibration plots for fluoxetine hydrochloride concentrations of up to 10 mg l^?1 (r=0.9995, n=7) were obtained, with an r.s.d<2% (n=10). Detection limit (3 σ) was 0.31 mg l^?1 and the sampling rate was about 136 determinations per h.     

Inertness of C<Subscript>60</Subscript> fullerene toward RO<Subscript>2</Subscript><Superscript>·</Superscript> peroxy radicals

The reactivity of fullerene C₆₀ toward peroxy radicals RO₂ ^· was tested by the chemiluminescence method. A comparison of the influence of C₆₀ and known inhibitors on the kinetics of liquid-phase chemiluminescence (CL) during oxidation of a series of hydrocarbons (ethyl-benzene, cyclohexane, n-dodecane, and oleic acid) shows that the fullerene does not react with the RO₂ ^· radicals. A sharp decrease in the CL intensity observed upon C₆₀ addition is caused by the quenching of CL emitters with fullerene but not by inhibition of hydrocarbon oxidation. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1808–1811, August, 2005.     

Determination of cefetamet pivoxil in human urine and serum using flow injection chemiluminescence procedure

A sensitive chemiluminescence method based on enhancing the effect of cefetamet pivoxil on the chemiluminescent reaction between luminol and dissolved oxygen in a flow injection system was proposed for the determination of cefetamet pivoxil. The increment of the chemiluminescence intensity was proportional to the concentration of cefetamet pivoxil, which yields a calibration graph that is linear over the concentration from 0.4 to 100.0 ng/mL (r ² = 0.991) with the detection limit of 0.1 ng/mL (3σ). At a flow rate of 2.0 mL/min complete determination of cefetamet pivoxil, including sampling and washing, could be accomplished in 40 s with the RSD of less than 0.03 (n = 5). The proposed method was applied successfully to the determination of cefetamet pivoxil in human urine and human serum. The text was submitted by the authors in English.