Enhanced chemiluminescence of cerium(IV)–Tween 85 system and the analytical application

The oxidation reaction between cerium(IV) and Tween 85 in sulfuric acid medium produced weak chemiluminescence (CL). In this paper, it was found that citrate could strongly enhance the CL of cerium(IV)–Tween 85–polyphenol system. Based on studies of ultraviolet–visible spectra and CL spectra, the CL enhancement mechanism had been proposed. It was surmised that the light emission was from an excited oxygen molecular pair O₂(¹Δ_g)O₂(¹∑_g^–). The maximum emission wavelength was about 478 nm. The effects of 17 amino acids and 29 organic compounds on cerium(IV)–Tween 85–citrate CL were investigated by a flow injection procedure. This study showed the present system had a wide application for the determination of these compounds. Copyright © 2012 John Wiley & Sons, Ltd.     

Chemiluminescence selectivity enhancement in the on‐chip Ru(bpy)32+ system: The potential role of buffer type and pH in the determination of hydrochlorothiazide in combined formulations and human plasma

A simple and highly selective on‐chip Ru(bpy)₃²⁺–oxidant chemiluminescence (CL) approach for estimation of a diuretic drug, hydrochlorothiazide (HCZ), in biological fluids was realized in the presence of other fixed‐dose combination drugs by manipulating simultaneously the method of active species (Ru(bpy)₃³⁺) production and type of carrier buffer with pH used for the CL reaction. Chemical oxidation processes involved in the Ru(bpy)₃²⁺–Ce(IV) CL system have been successfully miniaturised in this study using a microfabricated device to generate Ru(bpy)₃³⁺ instantaneously. The proposed system was then screened using HCZ and other drugs in the presence of various buffers and pH to explore the difference in CL emission. Ammonium formate buffer (0.15 M) at pH 4.5 exhibited excellent selectivity towards HCZ when Ru(bpy)₃³⁺ was produced by chemical oxidation using Ce(IV). The newly developed conditions do not involve any kind of prior separation or isolation procedure to remove other combination therapy drugs in formulation and biological samples. The method under fully optimised conditions exhibited wide linearity over the concentration range 0.5–1000 ng ml^?1 and low detection and quantification limits of 0.13 and 0.47 ng ml^?1 respectively for HCZ. Acceptable levels of recoveries were obtained for HCZ from human plasma using the proposed method (98.9–100.8%) in the presence of other antihypertensive combination therapy drugs. This study postulates that such miniaturised devices may find applications especially for on‐site analysis, such as doping control examinations.     

Mechanism of alcohol‐enhanced lucigenin chemiluminescence in alkaline solution

The chemiluminescence (CL) of lucigenin (Luc²⁺) can be enhanced by different alcohols in alkaline solution. The effect of different fatty alcohols on the CL of lucigenin was related to the carbon chain length and the number of hydroxyl groups. Glycerol provides the greatest enhancement. UV/Vis absorption spectra and fluorescence spectra showed that N‐methylacridone (NMA) was produced in the CL reaction in the presence of different alcohols. The peak of the CL spectrum was located at 470 nm in all cases, indicating that the luminophore was always the excited‐state NMA. The quenching of lucigenin CL by superoxide dismutase (SOD) and the electron spin resonance (ESR) results with the spin trap of 5,5‐dimethyl‐1‐pyrroline N‐oxide (DMPO) demonstrated that superoxide anions (O₂^?–) were generated from dissolved oxygen in the CL reaction and that glycerol and dihydroxyacetone (DHA) can promote O₂^?? production by the reduction of dissolved oxygen in alkaline solution. It was assumed that the enhancement provided by different alcohols was related to the solvent effect and reducing capacity. Glycerol and DHA can also reduce Luc²⁺ into lucigenin cation radicals (Luc^?+), which react with O₂^?? to produce CL, and glycerol can slowly transform into DHA, which is oxidized quickly in alkaline solution. Copyright © 2015 John Wiley & Sons, Ltd.     

Chemiluminescence determination of sulphite using a cyclometalated iridium complex as chemiluminescence reagent

A simple, fast and accurate chemiluminescence (CL) method for the determination of sulphite has been developed, based on its sensitizing effect on the CL reaction between a novel water‐soluble iridium complex, [(dpci)₂Ir(bvbbi)](PF₆) (dpci = 3,4‐diphenylcinnoline; bvbbi = N,N′‐bivinylester‐¹H,^1′H‐[2,2′] bibenzimidazole) and cerium(IV). Under the optimal experimental conditions, the increased CL response was linear, with the concentration of sulphite over the range 5.0 × 10^–7–5.0 × 10^–4 mol/L. The detection limit of the method was 1.6 × 10^–7 mol/L, with a relative standard deviation (RSD) of 2.7% for nine repetitive determination of 1.0 × 10^–4 mol/L sulphite. The method was successfully applied to the quantitative analysis of sulphite in sugar samples. The possible reaction mechanism of sulphite on the [(dpci)₂Ir(bvbbi)](PF₆)–cerium(IV) system is also briefly discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

Simple chemiluminescence determination of ketotifen using tris(1,10 phenanthroline)ruthenium(II)‐ Ce(IV) system

A new method using chemiluminescence (CL) detection has been developed for the simple determination of ketotifen fumarate (KF). The method is based on the catalytic effect of KF in the CL reaction of tris(1,10 phenanthroline)ruthenium(II), Ru(phen)₃²⁺, with Ce(IV) in sulfuric acid medium. The CL response was detected using a lab‐made chemiluminometer. Effects of chemical variables were investigated and under optimum conditions, the CL intensity was proportional to the concentration of the drug over the range 0.34‐34.00 µg mL^?1 KF. The limit of detection (S/N=3) was 0.09 µg mL^?1. Effects of common ingredients were investigated and the method was applied successfully for determining KF in pharmaceutical formulations and human plasma. The percent of relative standard deviation (n=11) at level of 3.4 µg mL^?1 of KF was 4.6% and the minimum sampling rate was 70 samples per hour. The possible CL mechanism is proposed based on the kinetic characteristic of the CL reaction, CL spectrum, UV‐Vis and phosphorescence spectra. Copyright © 2015 John Wiley & Sons, Ltd.     

1,10‐Phenanthroline–H2O2–KSCN–CuSO4–NaOH oscillating chemiluminescence system

In this paper, oscillating chemiluminescence (CL), 1,10‐phenanthroline H₂O₂–KSCN–CuSO₄–NaOH system, was studied in a batch reactor. The system described is a novel, slowly damped oscillating CL system, generated by coupling the well‐known Epstein–Orban, H₂O₂–KSCN–CuSO₄–NaOH chemical oscillator reaction with the CL reaction involving the oxidation of 1,10‐phenanthroline by hydrogen peroxide, catalyzed by copper(II) in alkaline medium. In this system, the CL reaction acts as a detector or indicator system of the far‐from‐equilibrium dynamic system. Narrow and slightly asymmetric light pulses of 1.2 s half‐width are emitted at 440 nm with an emitted light time of 200–1000 s, induction period of 3.5–357 s and oscillation period of 28–304 s depending on the reagent concentrations. In this report the effect of the concentration variation of components involved in the oscillating CL system on the induction period, the oscillation period and amplitude was investigated and the parameters were plotted with respect to reagent concentrations. Copper concentration showed a significant effect on the oscillation period. The possible mechanism for the oscillating CL reaction was also discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

A blue chemiluminescence in the reaction of umbelliferone with hypochlorite

A strongly fluorescing 7-hydroxycoumarin (umbelliferone, U) oxidized in dilute (10 μmol/L-0, 1 mol/L) aqueous solution with CIO^? or CIO^? + H₂O₂ (but not with H₂O₂ alone) produces a strong chemiluminescence (CL). Light emission kinetics depends on the pH of solution (4.0–10.5) and the reaction has a low activation energy E_a = 31 ± 2 kJ/mol (285–310 K). The spectrum covers the fluorescence of umbelliferone (400–550 nm, λ_max 460nm). No red emission typical of ¹Δg, ¹Σ⁺g (O₂)₂ is observed either in the umbelliferone +CIO^? or the umbelliferone +CIO^? + H₂O₂ solution. The possible mechanism of CL and concomitant degradative oxidation of umbelliferone is discussed.     

Pyrophosphate as substrate for alkaline phosphatase activity: A convenient flow‐injection chemiluminescence assay

A sensitive and convenient flow‐injection chemiluminescence (FI‐CL) turn‐on assay for alkaline phosphatase (ALP) activity without any label and synthesis is developed. Cu²⁺ can catalyze the luminol–H₂O₂ CL reaction. Pyrophosphate (PPi) can chelate Cu²⁺ and therefore the Cu²⁺‐mediated luminol‐H₂O₂ CL reaction is inhibited. The addition of ALP can catalyze the hydrolysis of PPi into phosphate ions, Cu²⁺ is released and the chemiluminescence recovers. A detection limit of 1 mU/mL ALP is obtained.     

A flow injection chemiluminescence method for the determination of lincomycin in serum using a diperiodato-cuprate (III)-luminol system

In this paper, the novel trivalent copper–periodate complex {K₅[Cu(HIO₆)₂], DPC} has been applied in a luminol‐based chemiluminescence (CL) reaction. Coupled with flow injection (FI) technology, the FI‐CL method was proposed for the determination of lincomycin hydrochloride. The CL reaction between luminol and DPC occurred in an alkaline medium. The CL intensity could be greatly enhanced by lincomycin hydrochloride. The relative CL intensity was proportional to the concentration of lincomycin hydrochloride in the range of 1 × 10^?8 to 5 × 10^?6 g mL^?1 and the detection limit was at the 3.5 × 10^?9 g mL^?1 level. The relative standard deviation at 5 × 10^?8 g mL^?1 was 1.7% (n = 9). The sensitive method was successfully applied to the direct determination of lincomycin hydrochloride (ng mL^?1) in serum. A possible mechanism of the lumonol–DPC CL reaction was discussed by the study of the CL kinetic characteristics and the spectra of CL reaction. The oxidability of DPC was studied by means of its electrochemical response. Copyright © 2010 John Wiley & Sons, Ltd.     

Large enhancement of oscillating chemiluminescence with [Ru(bpy)3]2+‐catalyzed Belousov–Zhabotinsky reaction in the presence of tri‐n‐propylamine

Oscillating chemiluminescence enhanced by the addition of tri‐n‐propylamine (TPrA) to the typical Belousov–Zhabotinsky (BZ) reaction system catalyzed by ruthenium(II)tris(2.2'‐bipyridine)(Ru(bpy)₃²⁺) was investigated using a luminometry method. The [Ru(bpy)₃]²⁺/TPrA system was first used as the catalyst for a BZ oscillator in a closed system, which exhibited a shorter induction period, higher amplitude and much more stable chemiluminescence (CL) oscillation. The effects of various concentrations of TPrA, oxygen and nitrogen flow rate on the oscillating behavior of this system were examined. In addition, the CL intensity of the [Ru(bpy)₃]²⁺/TPrA–BZ system was found to be inhibited by phenol, thus providing a way for use of the BZ system in the determination of phenolic compounds. Moreover, the possible mechanism of the oscillating CL reaction catalyzed by [Ru(bpy)₃]²⁺/TPrA and the inhibition effects of oxygen and phenol on this oscillating CL system were considered. Copyright © 2012 John Wiley & Sons, Ltd.     

Sulfur and nitrogen co‐doped graphene quantum dot‐assisted chemiluminescence for sensitive detection of tryptophan and mercury (II)

A simple one‐step thermal treatment to prepare strong fluorescent sulfur and nitrogen co‐doped graphene quantum dots (SN‐GQD) using citric acid and l ‐cysteine as precursors was developed. The ultra‐weak chemiluminescence (CL) from the reaction of hydrogen peroxide (H₂O₂) and periodate (IO₄^?) was significantly enhanced by SN‐GQD in acidic medium. The enhanced CL was induced by excited‐state SN‐GQD (SN‐GQD*), which was produced from the transfer energy of (O₂)₂* and ¹O₂ to SN‐GQD and recombination of oxidant‐injected holes and electrons in SN‐GQD. In the presence of tryptophan (Trp), the CL intensity of the SN‐GQD–H₂O₂–KIO₄ system was greatly diminished. This finding was used to design a novel method for determination of Trp in the linear range 0.6–20.0 μM, with a limit of detection (LOD) of 58.0 nM. Furthermore, Hg²⁺ was detectable in the range 0.1–9.0 μM with a LOD of 64.0 nM, based on its marked enhancement of the SN‐GQD–H₂O₂–KIO₄ CL system. The proposed method was successfully applied to detect Trp in milk and human plasma samples and Hg²⁺ in drinking water samples, with recoveries in the range 95.7–107.0%.     

Kinetic simulation studies on the transient formation of the oxo‐iron(IV) porphyrin radical cation during the reaction of iron(III) tetrakis‐5,10,15,20‐(N‐methyl‐4‐pyridyl)‐porphyrin with hydrogen peroxide in aqueous solution

High‐valent oxo‐iron(IV) species are commonly proposed as the key intermediates in the catalytic mechanisms of iron enzymes. Water‐soluble iron(III) tetrakis‐5,10,15,20‐(N‐methyl‐4‐pyridyl)porphyrin (Fe(III)TMPyP) has been used as a model of heme‐enzyme to catalyse the hydrogen peroxide (H₂O₂) oxidation of various organic compounds. However, the mechanism of the reaction of Fe(III)TMPyP with H₂O₂ has not been fully established. In this study, we have explored the kinetic simulation of the reaction of Fe(III)TMPyP with H₂O₂ and of the catalytic reactivity of FeTMPyP in the luminescent peroxidation of luminol. According to the mechanism that has been established in this work, Fe(III)TMPyP is oxidized by H₂O₂ to produce (TMPyP)^·+Fe(IV)=O (k1 = 4.5 × 10⁴/mol/L/s) as a precursor of TMPyPFe(IV)=O. The intermediate, (TMPyP)^·+Fe(IV)=O, represented nearly 2% of Fe(III)TMPyP but it does not accumulate in suf?cient concentration to be detected because its decay rate is too fast. Kinetic simulations showed that the proposed scheme is capable of reproducing the observed time courses of FeTMPyP in various oxidation states and the decay pro?les of the luminol chemiluminescence. It also shows that (TMPyP)^·+Fe(IV)=O is 100 times more reactive than TMPyPFe(IV)=O in most of the reactions. These two species are responsible for the initial sharp and the sustained luminol emissions, respectively. Copyright © 2003 John Wiley & Sons, Ltd.     

Development of a novel chemiluminescence method for the determination of cefazolin sodium in injectable powder and human urine based on a luminol‐Cu(III) complex reaction in alkaline medium

A novel chemiluminescence (CL) method was developed for the determination of cefazolin sodium based on the CL reaction between the [Cu(HIO₆)₂]^5‐Cu(III) complex and luminol in alkaline solution. Results showed that CL emission of Cu(III) complex–luminol in alkaline medium was significantly different from that in acidic medium. A possible mechanism of the enhanced effect of cefazolin on CL emission of the [Cu(HIO₆)₂]^5‐‐ luminol system was proposed. The effect of the reaction conditions on CL emissions was examined. Under optimized conditions, a good linear relationship was obtained between CL intensity and concentrations of cefazolin sodium in the range of 2.0 x 10^‐8 to 2.0 x 10^‐6 g/mL with a correlation coefficient of R² = 0.9978. The limit of detection was 4.58 x 10^‐9 g/mL. The proposed method was applied for the determination of cefazolin sodium in real samples with recoveries of 82.0‐109% with an RSD of 0.7‐2.1%. The proposed method was successfully used for the determination of cefazolin sodium in injectable powder preparations and human urine with satisfactory results. Copyright © 2012 John Wiley & Sons, Ltd.     

Determination of ampicillin sodium using the cupric oxide nanoparticles–luminol–H2O2 chemiluminescence reaction

A simple and sensitive chemiluminescence (CL) method has been developed for the determination of ampicillin sodium at submicromolar levels. The method is based on the inhibitory effect of ampicillin sodium on the cupric oxide nanoparticles (CuO NPs)–luminol–H₂O₂ CL reaction. Experimental parameters affecting CL inhibition including concentrations of CuO NPs, luminol, H₂O₂ and NaOH were optimized. Under optimum conditions, the calibration plot was linear in the analyte concentration range 4.0 × 10^‐7–4.0 × 10^‐6 mol/L. The limit of detection was 2.6 × 10^‐7 mol/L and the relative standard deviation (RSD) for six replicate determinations of 1 × 10^‐6 mol/L ampicillin sodium was 4.71%. Also, X–ray diffraction (XRD) and transmission electron microscopy (TEM) analysis were employed to characterize the CuO NPs. The utility of the proposed method was demonstrated by determining ampicillin sodium in pharmaceutical preparation. Copyright © 2013 John Wiley & Sons, Ltd.     

Application of optimized chemiluminescence assay for determination of the antioxidant capacity of herbal extracts

A chemiluminescence (CL) assay for the determination of antioxidant capacity (AOC) has been optimized and applied to analyses of herbal extracts in the present study. The optimal concentrations of reagents (luminol, H₂O₂, horseradish peroxidase) have been determined, as well as the optimal reaction conditions (wavelength, pH, temperature, sample volume). All of the measurements were performed at the emission maximum of the oxidized form of luminol (425 nm). The optimal concentrations of the reagents were determined as follows: 1.6 mmol/L luminol, 7.5 mmol/L H₂O₂ and 0.14 U/mL horseradish peroxidase activity in the reaction mixture. Analyses were carried out in phosphate buffer, pH 7.4, at room temperature. With the optimized CL assay, the AOCs of various water and methanol herbal extracts were determined (dog rose hips, plantain leaves and coltsfoot and thyme flowers) and the results were compared to those obtained by other classical methods for the evaluation of antioxidants. Strong correlations (r > 0.9) with the Folin–Ciocalteau assay and the 2,2‐diphenyl‐1‐picrylhydrazyl radical (DPPH)^● assay are confirmed, although there is no correlation between AOC and the concentration of ascorbic acid in the samples analysed. This optimized CL assay is simple, rapid and reliable, and it represents a good alternative to classical methods (Folin–Ciocalteau, DPPH^●) for the determination of AOC of herbal extracts and other food samples. Copyright © 2012 John Wiley & Sons, Ltd.     

Turn‐off–on chemiluminescence determination of cyanide

A flow injection chemiluminescence (FI–CL) method was developed for the determination of cyanide (CN⁻) based on the recovered CL signal by Cu²⁺ inhibiting a glutathione (GSH)‐capped CdTe quantum dot (QD) and hydrogen peroxide system. In an alkaline medium, strong CL signals were observed from the reaction of CdTe QDs and H₂O₂, and addition of Cu²⁺ could cause significant CL inhibition of the CdTe QDs–H₂O₂ system. In the presence of CN⁻, Cu²⁺ can be removed from the surface of CdTe QDs via the formation of particularly stable [Cu(CN)_n]^(n‐1)– species, and the CL signal of the CdTe QDs–H₂O₂ system was efficiently recovered. Thus, the CL signals of CdTe QDs–H₂O₂ system were turned off and turned on by the addition of Cu²⁺ and CN⁻, respectively. Further, the results showed that among the tested ions, only CN⁻ could recover the CL signal, which suggested that the CdTe QDs–H₂O₂–Cu²⁺ CL system had highly selectivity for CN⁻. Under optimum conditions, the CL intensity and the concentration of CN⁻ show a good linear relationship in the range 0.0–650.0 ng/mL (R² = 0.9996). The limit of detection for CN⁻ was 6.0 ng/mL (3σ). This method has been applied to detect CN⁻ in river water and industrial wastewater with satisfactory results. Copyright © 2014 John Wiley & Sons, Ltd.     

Development of chemiluminescence method for determination of 10‐hydroxycamptothecin based on luminol–[Ag(HIO6)2]5− reaction in alkaline solution

A novel chemiluminescence (CL) method was developed for the determination of 10‐hydroxycamptothecin(HCPT) based on the CL reaction between [Ag(HIO₆)₂]^5? and luminol in alkaline solution. CL emission of Ag(III) complex–luminol in alkaline medium was very different from that in acidic medium. A possible mechanism of enhanced CL emission was suggested. The enhanced effect of HCPT on CL emission of the [Ag(HIO₆)₂]^5?–luminol system was found. The enhanced degree of CL emission was proportional to HCPT concentration. The effect of the reaction conditions on CL emission was examined. Under optimal conditions, the limit of detection was 6.5 × 10^?9 g mL^?1. The proposed method was applied for the determination of HCPT in real samples with the recoveries of 93.2–109% with the RSD of 1.7–3.3%. Copyright © 2010 John Wiley & Sons, Ltd.     

Enhanced chemiluminescence of the luminol–AgNO3 system by Ag nanoparticles

The oxidation reaction of luminol with AgNO₃ can produce chemiluminescence (CL) in the presence of silver nanoparticles (NPs) in alkaline solution. Based on the studies of UV‐vis absorption spectra, photoluminescence (PL) spectra and CL spectra, a CL enhancement mechanism is proposed. The CL emission spectrum of the luminol–AgNO₃–Ag NPs system indicated that the luminophore was still 3‐aminophthalate. On injection of silver nanoparticles into the mixture of luminol and AgNO₃, they catalysed the reduction of AgNO₃ by luminol. The product luminol radicals reacted with the dissolved oxygen, to produce a strong CL emission. As a result, the CL intensity was substantially increased. Moreover, the influences of 18 amino acids, e.g. cystine, tyrosine and asparagine, and 25 organic compounds, including gallic acid, tannic acid and hydroquinone, on the luminol–AgNO₃–Ag NPs CL system were studied by a flow‐injection procedure, which led to an effective method for detecting these compounds. Copyright © 2011 John Wiley & Sons, Ltd.     

Ultrasensitive chemiluminescence assay for cimetidine detection based on the synergistic improving effect of Au nanoclusters and graphene quantum dots

A novel and sensitive chemiluminescence (CL) procedure based on the synergetic catalytic effects of gold nanoclusters (Au NCs) and graphene quantum dots (GQDs) was developed for the reliable measurement of cimetidine (CM). The initial experiments showed that the KMnO₄‐based oxidation of alkaline rhodamine B (RhoB) generated a very weak CL emission, which was intensively enhanced in the simultaneous presence of Au NCs and GQDs. CL intermediates can be adsorbed and gathered on the surface of Au NCs, becoming more stable. GQDs participate in the energy transferring processes and facilitate them. These improving effects were simultaneously obtained by adding both Au NCs and GQDs into the RhoB‐KMnO₄ reaction. Consequently, the increasing effect of the Au NCs/GQDs mixture was more than that of pure Au NCs or GQDs, and a new nano‐assisted powerful CL system was achieved. Furthermore, a marked quenching in the emission of the introduced CL system was observed in the presence of CM, so the system was examined to design a sensitive sensor for CM. After optimization of influencing parameters, the linear lessening in CL emission intensity of KMnO₄‐RhoB‐Au NCs/GQDs was verified for CM concentrations in the range 0.8–200 ng ml^?1. The limit of detection (3S_b/m) was 0.3 ng ml^?1. Despite being a simple CL method, good sensitivity was obtained for CM detection with reliable results for CM determination in human urine samples.