A kinetic treatment of stopped‐flow time courses for multiple chemiluminescence of the KIO4‐luminol‐Mn2+ system

Stopped‐flow time courses for chemiluminescence (CL) of the KIO₄‐luminol‐Mn²⁺system showed an instantaneous jump in initial signal followed by two distinct bands. A kinetic model of the form with ten adjustable parameters was proposed to account for CL intensity (I) versus time (t) profiles. The three terms in the model represent the three CL bands. Each band was comprised of a rise part and an exponential decay corresponding to the formation and deactivation of the CL emitter. CL bands could have originated from different CL pathways with the participation of reactive species such as O₂^?, ^?OH and ¹O₂ generated in the reactions involving IO₄^?, O₂ and Mn²⁺. Subsequent reactions of these reactive species with luminol induced CL emissions. Simulation parameters together with peak positions and intensities of the three CL bands were found to vary in different manners by changing conditions such as reagent concentration, pH and temperature. The temperature‐dependence of the rate constants yielded activation energies of 73.2 ± 2.8, 70.1 ± 2.4 and 67.2 ± 1.2 kJ?mol^‐1 for the three decay processes. Moreover, different substances exhibited a significant influence on the three CL bands and their simulation parameters. The numerous parameters and characteristics of CL emissions could serve as multiple probes for detecting analytes, making this system promising for potential analytical applications. Copyright © 2012 John Wiley & Sons, Ltd.     

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.     

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.     

Enhancement of chemiluminescence of the KIO4–luminol system by gallic acid,acetaldehyde and Mn2+: application for the determination of catecholamines

Chemiluminescence (CL) from the oxidation of luminol with potassium periodate in strong alkaline solutions was greatly enhanced by the combined effect of gallic acid, acetaldehyde and Mn²⁺. The CL spectra exhibited only one emission band at 425 nm, indicating 3‐aminophthalate as the emitting species. Various scavengers for superoxide anion, hydroxyl radical and singlet oxygen quenched the CL emission very efficiently (74–100%), suggesting the possible involvement of these reactive oxygen species (ROS) in the CL reactions. It is postulated that oxidation of gallic acid and acetaldehyde by periodate catalyzed by Mn²⁺ generates these ROS, which then react with luminol to enhance the CL emission. We also found that the enhanced CL emission was strongly inhibited by catecholamines, probably because of their effective scavenging of ROS. Based on this observation, a simple, rapid and sensitive new CL method was developed for the determination of catecholamines. The detection limits (3σ) for dopamine, l‐ dopa, norepinephrine and epinephrine were 0.63, 1.37, 0.56 and 14.3 nmol/L, respectively. The linear range was 1–10 nmol/L; relative standard deviations were 0.71–1.34% for 0.1 µmol/mL catecholamines. This CL method was applied to the determination of catecholamines in pharmaceutical injections with satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd.     

Flow injection chemiluminescence determination of naphazoline hydrochloride in pharmaceuticals

A simple and sensitive flow injection chemiluminescence (FI‐CL) method was developed for the determination of naphazoline hydrochloride (NPZ). The method is based on the enhancing effect of NPZ on the weak CL signal from the reaction of KIO₄ with H₂O₂. Experimental parameters that affected the CL signal, including the pH of the KIO₄ solution, concentrations of KIO₄, H₂O₂ and disodium‐EDTA and flow rate were optimized. Under the optimum conditions, the increment of CL intensity was linearly proportional to the concentration of NPZ in the range 5.0 × 10^?6 to 70 × 10^?6 mol/L. The detection limit was 1.0 × 10^?6 mol/L and the relative standard deviation for 50 × 10^?6 mol/L NPZ solution was 2.8% (n = 11). In addition, a high throughput of 120 samples/h was achieved. The utility of this method was demonstrated by determining NPZ in pharmaceuticals. Copyright © 2013 John Wiley & Sons, Ltd.     

Chemiluminescence from luminol solution after illumination of a 355 nm pulse laser

Chemiluminescence (CL) on the time scale of microseconds to milliseconds from luminol solution after illumination of a 355 nm pulse laser is reported. It was found that the CL is the emission from 3‐aminophthalate ion (AP*). In CL decay after the pulse laser illumination, a peak was observed from about 200 to 30 µs depending on the laser power and the luminol concentration. It seemed that there was a fast and slow decay process; their kinetics were greatly dependent on the laser power and the luminol concentration. Dissolved oxygen was involved in the CL and played the same role on the whole time scale of microseconds to milliseconds. Involvement of reactive oxygen species such as H₂O₂, ¹O₂, O₂^?? and OH in the CL was examined by adding their scavengers. Experimental results suggested that the possibility of involvement of H₂O₂ and ¹O₂ in the CL was low. The CL in time periods less than 50 µs might be related to ?OH. The ^?O₂^??‐induced CL increased with time after 50 µs and became dominant on the time scale of milliseconds. The CL was considered to be caused by both the photoionization and type I reaction mechanisms. Copyright © 2009 John Wiley & Sons, Ltd.     

Studies of visible oscillating chemiluminescence in luminol–H2O2–KSCN–CuSO4 system using (2‐hydroxyethyl) trimethylammonium hydroxide

Visible oscillating chemiluminescence (CL) of luminol–H₂O₂–KSCN–CuSO₄ was studied using the organic base (2‐hydroxyethyl)trimethylammonium hydroxide. The effect of concentrations of luminol, H₂O₂, KSCN, CuSO₄ and the base were investigated in a batch reactor. This report shows how the concentration of components involved in the oscillating CL system influenced the oscillation period, light amplitude and total time of light emission. The oscillating CL with different bases was also investigated. Results indicated that using 2‐HETMAOH causes regular oscillating CL with nearly the same oscillating period. Copyright © 2008 John Wiley & Sons, Ltd.     

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%.     

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.     

Chemiluminescence determination of naproxen based on europium(III)‐sensitized KIO4–H2O2 reaction

A simple and sensitive chemiluminescence (CL) method combined with flow injection technique was developed for the determination of naproxen. It was based upon the weak CL signal arising from the reaction of KIO₄ with H₂O₂ being significantly increased by naproxen in the presence of europium(III) ion. The experimental conditions that affected the CL signal were carefully optimized and the CL reaction mechanism was briefly discussed. Under the optimum conditions, the increment of CL intensity was proportional to the concentration of naproxen ranging from 5.0 × 10^?8 to 5.0 × 10^?6 g/mL. The detection limit was 1 × 10^?8 g/mL naproxen and the relative standard deviation for 5.0 × 10^?7 g/mL naproxen solution was 2.1% (n = 11). The proposed method was applied to the determination of naproxen in tablets and in spiked human urine samples with satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd.     

Sensitive determination of epinephrine in pharmaceutical preparation by flow injection coupled with chemiluminescence detection and mechanism study

A novel, rapid and sensitive method was described for the determination of epinephrine (EP) using flow injection analysis coupled with chemiluminescence (CL) detection, which based on EP enhanced the weak CL emission of luminol–KIO₄ system in NaOH solution. Parameters affecting the CL intensity and reproducibility were optimized systematically. Under the optimized experiment conditions, the net CL intensity was proportional to the concentration of EP in the range of 5.0 × 10^?8 to 1.5 × 10^?6 mol/L with a detection limit of 1.9 × 10^?9 mol/L. The relative standard deviation (RSD) was found to be 0.7% for 13 replicate determinations of 3.0 × 10^?7 mol/L EP. The applicability of the proposed method was illustrated in the determination of EP in pharmaceutical preparation. The recoveries of EP at different levels in EP hydrochloride injection were between 95.4 and 104.7%. One assay procedure takes only 27 s, and the sampling rate was calculated about to be 130 samples/h. The possible mechanism of the enhanced CL intensity was studied by examining CL spectra and UV–vis spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Amino acids as novel nucleophiles for silver nanoparticle‐luminol chemiluminescence

The use of noble metal nanoparticles (NPs) as reductants in chemiluminescence (CL) has been reported only rarely owing to their high oxidation potentials. Interestingly, nucleophiles could dramatically lower the oxidation potential of Ag NPs, such that in the presence of nucleophiles Ag NPS could be used as reductants to induce the CL emission of luminol, an important CL reagent widely used in forensic analysis for the detection of trace amounts of blood. Although nucleophiles are indispensible in Ag NP‐luminol CL, only inorganic nucleophiles such as Cl^‐, Br^‐, I^‐ and S₂O₃^2‐ have been shown to be efficient. The effects of organic nucleophiles on CL remain unexplored. In this study, 20 standard amino acids were evaluated as novel organic nucleophiles in Ag NP‐luminol CL. Histidine, lysine and arginine could initiate CL emission; the others could not. It is proposed that the different behaviors of 20 standard amino acids in the CL reactions derive from the interface chemistry between Ag NPs and these amino acids. UV/vis absorption spectra were studied to validate the interface chemistry. In addition, imidazole and histidine were chosen as a model pair to compare the behavior of the monodentate nucleophile with that of the corresponding multidentate nucleophile in Ag NP‐luminol CL. Copyright © 2014 John Wiley & Sons, Ltd.     

Studies of visible oscillating chemiluminescence with a luminol–H2O2–KSCN–CuSO4–NaOH system in batch reactor

Oscillating chemical reactions are complex systems involving a large number of chemical species. In oscillating chemical reactions some species, usually reaction intermediates, exhibit fluctuation in concentration. Visible oscillating chemiluminescence, produced by the addition of luminol (3‐aminophthalhydrazide) to the oscillating system H₂O₂–KSCN–CuSO₄–NaOH, was investigated. In this study the effect of varying the concentration of H₂O₂, KSCN, CuSO₄, NaOH and luminol was investigated in a batch reactor. We showed that the concentration of all components involved in the oscillating chemilumenscent reaction influenced the light intensity and the oscillation period. Copyright © 2002 John Wiley & Sons, Ltd.     

Employment of 4‐(1,2,4‐triazol‐1‐yl)phenol as a signal enhancer of the chemiluminescent luminol–H2O2–horseradish peroxidase reaction for detection of hepatitis C virus in real samples

Highly sensitive detection of hepatitis C virus (HCV) in serum is a key method for diagnosing and classifying the extent of HCV infection. In this study, a p‐phenol derivative, 4‐(1,2,4‐triazol‐1‐yl)phenol (4‐TRP), was employed as an efficient enhancer of the luminol–hydrogen peroxide (H₂O₂)–horseradish peroxidase (HRP) chemiluminescence (CL) system for detection of HCV. Compared with a traditional enhancer, 4‐TRP strongly enhanced CL intensity with the effect of prolonging and stabilizing light emission. The developed CL system was applied to detecting HCV core antigen (HCV‐cAg) using a sandwich structure inside microwells. Our experimental results showed that there was good linear relationship between CL intensity and HCV‐cAg concentration in the 0.6–3.6 pg/mL range (R = 0.99). The intra‐ and inter‐assay coefficients of variation were 4.5–5.8% and 5.0–7.3%, respectively. In addition, sensitive determination of HCV‐cAg in serum samples using the luminol–H₂O₂–HRP–4‐TRP CL system was also feasible in clinical settings. Copyright © 2015 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.     

Chemiluminescence of off‐line and on‐line gold nanoparticle‐catalyzed luminol system in the presence of flavonoid

It was found that flavonoids could remarkably inhibit the chemiluminescence (CL) intensity of an off‐line gold nanoparticle (AuNP)‐catalyzed luminol–H₂O₂ CL system. By contrast, flavonoids enhanced the CL intensity of an on‐line AuNP‐catalyzed luminol–H₂O₂ CL system. In the off‐line system, the AuNPs were prepared beforehand, whereas in the on‐line system, AuNPs were produced by on‐line mixing of luminol prepared in a buffer solution of NaHCO₃ ? Na₂CO₃ and HAuCl₄ with no need for the preliminary preparation of AuNPs. The on‐line system had prominent advantages over the off‐line system, namely a lowering of the background noise and improvements in the stability of the CL system. The results show that differences in the signal suppression effect of flavonoids on the off‐line AuNP‐catalyzed CL system are influenced by the combined action of a free radical scavenging effect and occupy‐sites function; the latter was proved to be predominant using controlled experiments. Enhancement of the on‐line system was ascribed to the presence of flavonoids promoting the on‐line formation of AuNPs, which better catalyzed the luminol–H₂O₂ CL reaction, and the enhancement activity of the six flavonoids increased with the increase in reducibility. This work broadens the scope of practical applications of an AuNP‐catalyzed CL system.     

Investigations of different chemiluminescent peaks in H2O2–SCN−–Cu2+–OH−–luminol flow system

In the H₂O₂–SCN^?–Cu²⁺–OH^?–luminol oscillatory system of chemiluminescence, the effects of the ingredient concentrations, temperature, flow rate and complexing agent on the oscillatory dynamics were investigated in a continuous‐flow stirred tank reactor (CSTR). The dynamical structure of two peaks during a period was discussed in detail. By addition of EDTA to the oscillating system, the peak I height decreased sharply while the peak II height was little affected, and the period kept constant. This may be due to the fast reaction between Cu(II) and EDTA and the highly stable complex Cu(II)–EDTA. From the experimental study and mechanism analysis, the chemiluminescent peak I corresponds to Cu(II) → Cu(I) transformation and the peak II corresponds to the Cu(I) → Cu(II) transformation process. The key species involving in the two‐transformation process are inferred to be superoxide radical and hydroxyl radical. Copyright © 2010 John Wiley & Son, 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%.     

Comparison of chemiluminescence from luminol solution and luminol–TiO2 suspension after illumination of a 355 nm pulse laser

Chemiluminescence (CL) from luminol solution and luminol–TiO₂ suspension after illumination of a 355 nm pulse laser is compared. Both the CL systems showed the CL spectra with maximum wavelength of 430 nm, suggesting that the emission was from the excite state of 3‐aminophthalate ion. The TiO₂ photocatalytically induced luminol CL could be separately detected either when the pulse laser power was smaller than 0.15 mJ/pulse or a slit was placed beyond ?2–2 mm in the vertical direction of the laser beam. The TiO₂ photocatalytically induced luminol CL intensity was linear to the laser power, while that of the 355 nm pulse laser‐induced was nonlinear. A log–log plot between the 355 nm pulse laser‐induced luminol CL intensity and laser power showed a near‐linear regression fit with a slope of 2.11, suggesting that a two‐photon absorption process of luminol was present in the 355 nm pulse laser‐induced luminol CL. Adsorbed oxygen on the surface of TiO₂ seemed to greatly contribute to the photocatalytically induced CL. Copyright © 2010 John Wiley & Sons, Ltd.     

Optimization of peroxynitrite–luminol chemiluminescence system for detecting peroxynitrite in cell culture solution exposed to carbon disulphide

We established a peroxynitrite–luminol chemiluminescence system for detecting peroxynitrite in cell culture solution exposed to carbon disulphide (CS₂). Three factors, including exposure time to ozone (Factor A), volume of peroxynitrite (ONOO^?) solution (Factor B) and luminol concentrations (Factor C) at three levels were selected and the combinations were in accordance with orthogonal design L₉ (3⁴). Peroxynitrite was generated from the reaction of ozone and 0.01 mol/L sodium azide (NaN₃) dissolved in carbonic acid buffer solution (pH 11), and it was reacted with luminol to yield chemiluminescence. The peak value, peak time and kinetic curve of the light emission were observed. The selected combination conditions were 50 s ozone, 800 µL peroxynitrite and 0.001 mol/L luminol solution. Cell culture solution with CS₂ enhanced the emission intensity of chemiluminescence (F = 8.38, p = 0.018) and shortened the peak time to chemiluminescence (F = 139.00, p = 0.0001). The data demonstrated that this luminol chemiluminescence system is suitable for detecting peroxynitrite in cell culture solutions for evaluating the effect of CS₂ on endothelial cells. Copyright © 2003 John Wiley & Sons, Ltd.