Determination of tannic acid in industrial wastewater based on chemiluminescence system of KIO4–H2O2–Tween40

The oxidation reaction of H₂O₂ with KIO₄ can produce chemiluminescence (CL) in the presence of the surfactant Tween40 and the CL intensity of the CL system KIO₄–H₂O₂–Tween40 can be strikingly enhanced after injection of tannic acid. On this basis, a flow injection method with CL detection was established for the determination of tannic acid. The method is simple, rapid and effective to determine tannic acid in the range of 7.0 × 10^?9 to 1.0 × 10^?5 mol/L with a determination limit of 2.3 × 10^?9 mol/L. The relative standard deviation is 2.6% for the determination of 5.0 × 10^?6 mol/L tannic acid (n = 11). The method has been applied to determine the content of tannic acid in industrial wastewater with satisfactory results. It is believed that the CL reaction formed singlet oxygen ¹O₂* and the emission was from an excited oxygen molecular pair O₂(¹Δ_g)O₂(¹∑^?_g) in the KIO₄–H₂O₂–Tween40 reaction. Tween40 played an important role in enhancing stabilization of the excited oxygen molecular pair O₂(¹Δ_g)O₂(¹∑^?_g) and in increasing CL intensity. Copyright © 2010 John Wiley & Sons, Ltd.     

Near infrared emission of singlet oxygen generated in the dark

Singlet oxygen generation is reported from (1) enzymatic reaction and (2) electron transfer reactions of the superoxide anion measured directly with an ultrasensitive near-IR emission spectrophotometer by monitoring the O₂(¹Δ_g) → O₂ (³Σ_g^?) transition at 1268 nm. Near-IR emission spectra from the myeloperoxidase and lactoperoxidase enzymatic systems show only emission of singlet oxygen at 1268nm. The lipoxygenase/Na–linoleate enzymatic reaction exhibits two emissions, 1268 nm and 1288 nm. The latter emission is identified as originating from a peroxy radical. Spectral and kinetic data giving evidence of singlet oxygen generation is obtained from the reaction of potassium superoxide solubilized by 18-crown-6-ether in acetonitrile with a series of organometallic coordination compounds.     

Chemiluminescence of cereal products. II. Chemiluminescence spectra

Spectra of ultraweak chemiluminescence (CL) accompanying auto-oxidation and hydration of cereal products have been measured using single photon counting and cut-off filters. The spectra cover the 380–880 nm spectral range with maxima centred around 600 nm. Analytically pure air-dried carbohydrates like agar, cellulose and nitrocellulose give emission too weak for spectral measurements. The emission from water pure carbohydrates is on average 4–12 times higher and emission spectra are similar to those from cereal products. The effect of free radical scavengers, SOD and O*₂ (¹Δ_g)-quenchers on CL spectra indicates a contribution of radical reactions with the participation of excited carbonyls, O₂⁻ and excited molecular oxygen dimoles. Moreover, possible mechanisms of chemi-excitation due to a cooperative H-bond formation during the hydration of carbohydrates and/or recombination of trapped radicals and electron-holes are discussed. It is also postulated that the excitation energy transfer to natural sensitizers occuring in cereal products may account for non-specific broad spectra and differences in the intensity of CL. © 1998 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.     

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.     

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

The reaction of iron(III) tetrakis‐5,10,15,20‐(N‐methyl‐4‐pyridyl)porphyrin (Fe(III)TMPyP) with hydrogen peroxide (H₂O₂) and the catalytic activity of the reaction intermediates on the luminescent peroxidation of luminol in aqueous solution were studied by using a double‐mixing stopped‐flow system. The observed luminescence intensities showed biphasic decay depending on the conditions. The initial flashlight decayed within <1 s followed by a sustained emission for more than 30 s. Computer deconvolution of the time‐resolved absorption spectra under the same conditions revealed that the initial flashlight appeared during the formation of the oxo–iron(IV) porphyrin, TMPyPFe(IV) = O, which is responsible for the sustained emission. The absorption spectra 0.0–0.5 s did not reproduce well by a simple combination of the two spectra of Fe(III)TMPyP and TMPyPFe(IV) = O, indicating that transient species was formed at the initial stage. Addition of uric acid (UA) caused a significant delay in the initiation of the luminol emission as well as in the formation of the TMPyPFe(IV) = O. Both of them were completely diminished in the presence of UA equimolar with H₂O₂, while mannitol had no effect at all. The delay of the light emission as well as the appearance of TMPyPFe(IV) = O was directly proportional to the [UA]₀ but other kinetic profiles were not changed significantly. Based on these observations and the kinetic analysis, we confirmed the involvement of the oxo–iron(IV) porphyrin radical cation, (TMPyP)^·+Fe(IV) = O, as an obligatory intermediate in the rate‐determining step of the overall reaction, Fe(III)TMPyP + H₂O₂ → TMPyPFe(IV) = O, with a rate constant of k = 4.3 × 10⁴/mol/L/s. The rate constants for the reaction between the (TMPyP)^·+Fe(IV) = O and luminol, and between the TMPyPFe(IV) = O and luminol were estimated to be 3.6 × 10⁶/mol/L/s and 1.31 × 10⁴/mol/L/s, respectively. Copyright © 2003 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.     

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.     

Chemiluminescence investigations of antioxidative activities of some antibiotics against superoxide anion radical

A chemiluminescent technique was applied to determine antioxidative activities of adriamycin, farmorubicin, mitomycin C and bleomycin against superoxide anion radical (O₂^?) in aprotic medium. The antioxidant capacity was expressed as the decrease in light emission from the O₂^? solution by and antibiotic. A KO₂ solution in dimethyl sulphoxide (DMSO) and 18‐crown‐6 ether were used for the generation of O₂^?. The results showed that the examined compounds decreased the chemiluminescence (CL) sum from the O₂^?‐generating system in a dose‐dependent manner. Among the antibiotics examined, adriamycin, farmorubicin and bleomycin exhibited antioxidant activity almost comparable to that of 1,2‐dihydroxy benzene‐3,5‐disulphonic acid (tiron), an efficient of the O₂^? inhibitor. Mitomycin C was two‐times less effective as tiron in decreasing the initial CL intensity. The proposed assay with usage of ultraweak CL technique and the KO₂–DMSO–crown ether system was useful for the evaluation of antioxidant activity in aprotic solvents. Copyright © 2011 John Wiley & Sons, Ltd.     

Luminol–silver nitrate chemiluminescence enhancement induced by cobalt ferrite nanoparticles

CoFe₂O₄ nanoparticles (NPs) could stimulate the weak chemiluminescence (CL) system of luminol and AgNO₃, resulting in a strong CL emission. The UV–visible spectra, X‐ray photoelectron spectra and TEM images of the investigated system revealed that AgNO₃ was reduced by luminol to Ag in the presence of CoFe₂O₄ NPs and the formed Ag covered the surface of CoFe₂O₄ NPs, resulting in CoFe₂O₄–Ag core–shell nanoparticles. Investigation of the CL reaction kinetics demonstrated that the reaction among luminol, AgNO₃ and CoFe₂O₄ NPs was fast at the beginning and slowed down later. The CL spectra of the luminol ? AgNO₃ ? CoFe₂O₄ NPs system indicated that the luminophor was still an electronically excited 3‐aminophthalate anion. A CL mechanism has been postulated. When the CoFe₂O₄ NPs were injected into the mixture of luminol and AgNO₃, they catalyzed the reduction of AgNO₃ by luminol to produce luminol radicals and Ag, which immediately covered the CoFe₂O₄ NPs to form CoFe₂O₄–Ag core–shell nanoparticles, and the luminol radicals reacted with the dissolved oxygen, leading to a strong CL emission. With the continuous deposition of Ag on the surface of CoFe₂O₄ NPs, the catalytic activity of the core–shell nanoparticles was inhibited and a decrease in CL intensity was observed and also a slow growth of shell on the nanoparticles. Copyright © 2011 John Wiley & Sons, Ltd.     

Chemiluminescence determination of bromhexine hydrochloride with morin as chemiluminescent reagent

A new chemiluminescence (CL) reaction was observed when cerium(IV) solution was injected into bromhexine hydrochloride–morin solution. Based on this, a flow‐injection CL method for the determination of bromhexine hydrochloride was established. A possible mechanism of the CL reaction was proposed via the investigation of the CL kinetic characteristics, the CL spectrum and the fluorescence spectra of some related substances. Under optimum conditions, the CL signal was correlated linearly with concentration of bromhexine hydrochloride over the range 2.0 × 10^–9–2.0 × 10^–7 g/mL, with a linear correlation of 0.9995. The detection limit was 9 × 10^–10 g/mL bromhexine hydrochloride and the relative standard deviation was 1.0% (c = 2.0 × 10^–8 g/mL bromhexine hydrochloride, n = 11). The method was applied to the determination of bromhexine hydrochloride in pharmaceutical preparations and human urine samples with satisfactory results. Copyright © 2008 John Wiley & Sons, Ltd.     

Luminescence study and dosimetry approach of Ce on an α‐Sr2P2O7 phosphor synthesized by a high‐temperature combustion method

We report synthesis of a cerium‐activated strontium pyrophosphate (Sr₂P₂O₇) phosphor using a high‐temperature combustion method. Samples were characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), photoluminescence (PL) and thermoluminescence (TL). The XRD pattern reveals that Sr₂P₂O₇ has an α‐phase with crystallization in the orthorhombic space group of Pnam. The IR spectrum of α‐Sr₂P₂O₇ displays characteristic bands at 746 and 1190 cm^‐1 corresponding to the absorption of (P₂O₇)^‐4. PL emission spectra exhibit a broad emission band around 376 nm in the near‐UV region due to the allowed 5d–4f transition of cerium and suggest its applications in a UV light‐emitting diode (LED) source. PL also reveals that the emission originates from 5d–4f transition of Ce³⁺ and intensity increases with doping concentration. TL measurements made after X‐ray irradiation, manifest a single intense glow peak at around 192°C, which suggests that this is an outstanding candidate for dosimetry applications. The kinetic parameters, activation energy and frequency factor of the glow curve were calculated using different analysis methods. Copyright © 2014 John Wiley & Sons, Ltd.     

A stopped‐flow study of the dual chemiluminescence for the luminol–KIO4–Mn2+ system in strong alkaline solutions

A novel phenomenon of dual chemiluminescence (CL) was observed for the KIO₄–luminol–Mn²⁺ system in strong alkaline solutions using the stopped‐flow technique. Scavenging study of the reactive oxygen species (ROS) suggested that the two CL peaks originated from different CL pathways precipated by distinct ROS (O₂^? and ^?OH for the first peak, mainly ¹O₂ for the second peak). Generation of these ROS at different time intervals from the reactions involving IO₄^?, O₂, and Mn²⁺ and their subsequent reactions with luminol induced the intense CL emission. The relative intensity of the two CL peaks can be tuned over a wide range by varying the concentrations of Mn^2?, luminol and KIO₄. Because of the involvement of different ROS in each pathway, the two CL peaks could respond quite differently to various substances. Moreover, variation of the intensity ratio of the two CL peaks altered the relative proportions of the corresponding ROS, thereby changing their responses to a given substance. The dual CL emission acts like a pair of tunable probes and it is believed that this CL system has great potential in analytical applications. Copyright © 2010 John Wiley & Sons, Ltd.     

Chemiluminescence of copper nanoclusters and its application for trihexyphenidyl hydrochloride detection

Chemiluminescence (CL) of copper nanoclusters (CuNCs) induced by cerium (IV) (Ce(IV)) or potassium permanganate (KMnO₄) in acidic medium was observed. The potential application of CuNCs CL in analytical chemistry was also demonstrated using trihexyphenidyl hydrochloride (THP) as an example based on its enhancing CL intensity for the CuNCs–Ce(IV)/KMnO₄ systems. The excited state of the CuNCs acted as a luminophore in the CuNCs–Ce(IV) system, while CuNCs played the role of reductant in the CuNCs–KMnO₄ system. The increased CL intensity for Ce(IV)–CuNCs system was proportional to the THP concentrations in the range of 0.1 to 10.0 μM. The detection limit was 49.0 nM and the relative standard deviation was 2.2% for 2.0 μM THP (n = 11). The proposed method was applied to detect THP in pharmaceutical formulations and human plasma samples.     

Eco-friendly nonconjugated polymer dots for chemiluminometric determination of 4-nitrophenol

Polymer dots (PDs) are a new family of quantum dots for which their behavior and potential applications have not yet been completely explored. In this study, nonconjugated PDs were synthesized using a simple pyrolysis method and used for the chemiluminescence (CL) assay of 4-nitrophenol (4-NP). PDs increased the CL signal of the Ce(IV)–Na₂SO₃ reaction 39-fold. Using the CL spectrum, it was concluded that the emission at 434 nm was generated by excited PDs (PDs*), which are produced by energy transfer from SO₂* to PDs. Our experiments showed that 4-NP enhanced the CL signal of the Ce(IV)–Na₂SO₃–PDs reaction. The mechanism of this effect was explored by obtaining CL, ultraviolet–visible, and Fourier transform infrared spectra. Due to the high sensitivity and selectivity of the CL system for 4-NP, a probe was designed to determine 4-NP in the linear range 1.0–500 nmol/L with a detection limit of 0.33 nmol/L. Different spiked real samples were successfully analyzed using this probe.     

Flow‐injection chemiluminescence of the luminol–potassium periodate system enhanced by TGA–capped CdTe quantum dots for the determination of theophylline

The chemiluminescence (CL) behaviour of the luminol–potassium periodate system enhanced by CdTe quantum dots capped with thioglycolic acid (TGA–CdTe QDs) was studied using kinetic experiments, CL spectra, UV–vis absorption spectra and fluorescence spectra. The production of oxygen‐containing reactant intermediates (O₂^?? and OH^?) in the present CL system was verified by CL. The possible CL mechanism was discussed in detail. Furthermore, theophylline (THP) was determined based on its enhancement of the CL intensity of the CdTe QDs–luminol–potassium periodate system coupled with a flow‐injection technique. Under these optimized conditions, the linear range was found to be from 1.0 × 10^?8 to 1.0 × 10^?5 g/mL with a detection limit of 2.8 × 10^?9 g/mL (3σ). The recoveries for the determination of THP in tablets were from 98.2 to 99.6%.     

Prospects for using a new sequential chemiluminescence strategy for monitoring the caffeine content in soft and energy drinks via the catalytic activities of different nano‐metal oxides

This article suggests a new sequential injection analysis chemiluminescence (SIA‐CL) strategy for monitoring the caffeine (CAF) content in soft and energy drinks using the catalytic activities of different nano‐metal oxides. The present study describes three different SIA‐CL systems (luminol–ferricyanide (III) coupled with Fe₂O₃ or ZnO nanoparticles (NPs), and luminol–H₂O₂ coupled with CuONPs. All experimental conditions were optimized and the linear concentration ranges of pure CAF were evaluated using the calibration graphs. The selectivity of the developed SIA‐CL systems was studied under the influence of various interfering species that may be present in soft or energy drinks such as sodium ions, sucrose, glucose, sodium benzoate, sodium citrate, riboflavin, niacin, citric, phosphoric and ascorbic acids. International Council for Harmonization (ICH) guidelines were obeyed for the validation of the suggested CL methods. The developed SIA‐CL systems displayed linear relationships over the concentration ranges 1.0–350, 5.0–400 and 10.0–400 μg ml^?1 with Fe₂O₃ NPs, ZnO NPs and CuO NPs, respectively. The recorded lower limits of detection and quantification were 0.7, 2.7 and 7.8 μg ml^?1, and 1.0, 5.0 and 10.0 μg ml^?1 for the previously mentioned SIA‐CL systems. The results revealed high selectivity for CAF determination and were in good agreement with those obtained by other reported methods.     

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.     

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.     

Development of a benzene vapour sensor utilizing chemiluminescence on Y2O3

Chemiluminescence (CL) was observed when benzene vapour passed through the surface of Y₂O₃, TiO₂, Y₂O₃–V₂O₅, TiO₂–Y₂O₃, Y₂O₃–Cr₂O₃, Y₂O₃–Al₂O₃ and TiO₂–Al₂O₃, with air as the carrier gas. The strongest CL intensity was found with Y₂O₃ as the catalyst. A novel benzene sensor based on this kind of CL was developed. Quantitative analysis was performed at the wavelength of 425 nm. Under optimal conditions, CL intensity was directly proportional to the concentration of benzene vapour. The linear range was 4–7018 mg/m³ (r = 0.9981, n = 11), with a detection limit of 1 mg/m³ (the signal:noise ratio was 3). This gas sensor can work continuously for >80 h and has been successfully applied to the real‐time determination of benzene vapour. Copyright © 2008 John Wiley & Sons, Ltd.