Flow-injection chemiluminescence determination of fluoroquinolones by enhancement of weak chemiluminescence from peroxynitrous acid

A flow-injection chemiluminescence (CL) method is described for the determination of fluoroquinolones including ciprofloxacin, norfloxacin and ofloxacin. The method is based on the enhancement by these compounds of the weak CL from peroxynitrous acid. The linear ranges are 1.0×10⁻⁷ to 1.0×10⁻⁵ mol l⁻¹ for ciprofloxacin and norfloxacin, and 3.0×10⁻⁷ to 3.0×10⁻⁵ mol l⁻¹ for ofloxacin, respectively. The detection limits (S/N=3) are 4.5×10⁻⁸ mol l⁻¹ ciprofloxacin, 5.9×10⁻⁸ mol l⁻¹ norfloxacin and 1.1×10⁻⁷ mol l⁻¹ ofloxacin, respectively. The proposed method was applied to the determination of fluoroquinolones in pharmaceutical preparations.     

Silver nanoparticle-initiated chemiluminescence reaction of luminol-AgNO3 and its analytical application

Ag⁺ has been regarded as an inert chemiluminescent oxidant. In this work, it was found that in the presence of silver nanoparticles (AgNPs), AgNO₃ could react with luminol to produce strong chemiluminescence (CL). The AgNPs with smaller size could initiate stronger CL emission. To investigate the CL mechanism of the AgNPs–luminol–AgNO₃ system, the UV–visible spectra and the CL spectrum of the CL system were obtained. The CL reaction mechanism involving catalysis was proposed. Compared with the reported nanoparticles–luminol–H₂O₂ CL system, the AgNPs–luminol–AgNO₃ CL system has the advantages of low background and good stability. Moreover, the new CL system was used in immunoassay for IgG.     

Sensitivity enhancement of liquid chromatographic-direct chemiluminescence detection by on-line post-column solvent mediated pre-oxidative chemiluminescence

The compatibility of liquid chromatography solvents with oxidizing reagents frequently employed in direct chemiluminescence reactions is examined in this study. Various oxidizing reagents were examined for their response in hydro-organic and micellar mobile phases in both isocratic and gradient elution modes. Mild oxidants like hydrogen peroxide, periodate, cerium and hypochlorite were found to be completely compatible with common reversed phase HPLC solvents posing as no threat to the detection procedure. On the other hand, stronger oxidants like acidic permanganate were found to oxidize organic solvents towards the production of an intense light signal. Although several analytical applications can emerge from this finding, the conjunction of this system with reversed phase HPLC is impractical owing to a significant baseline increase which deteriorates the sensitivity of the analysis. A convenient solution to this problem is proposed based on the regulated on-line post-column pre-oxidation of the organic solvent (SPOC) with mild oxidants that have no influence on the final signal. The analytical utility of this new approach in the determination of organic compounds after chromatographic separation is demonstrated.     

Silver nanoparticle-based chemiluminescence enhancement for the determination of norfloxacin

A chemiluminescence (CL) method is presented for the flow injection determination of norfloxacin (NFLX). It is based on the fact that the weak CL of the Ce(IV)-Na₂SO₃ redox system is strongly enhanced in the presence of silver nanoparticles. UV-visible and fluorescence spectroscopy was carried out and showed that the energy of the intermediate SO₂*, originating from the reaction of Ce(IV) with Na₂SO₃, was transferred to Tb³⁺ via NFLX, and that the silver nanoparticles (AgNPs) accelerate the process due to the electric activity of AgNPs. Norfloxacin was detected by measuring the CL intensity which increases linearly with the concentration of NFLX in the range from 10 nM to 50 μM. The detection limit is lowered to 2.0 nM. The method was successfully applied to the determination of NFLX in eyedrops.     

Rapid determination of subnanogram urapidil using flow injection enhancement chemiluminescence

A sensitive flow-injection (FI) chemiluminescence (CL) for the determination of urapidil is described in this paper. It is based on the enhancement effect of urapidil on the CL reaction between luminol and hydrogen peroxide. The increment of CL intensity is proportional to the concentration of urapidil in the range 0.1−10 ng/mL (R ²=0.9986), with a detection limit (3σ) of 0.03 ng/mL. The whole process, at a flow rate of 2.0 mL/min, including sampling and washing, could be completed in 0.5 min, and the relative standard deviation (RSD) at the concentration of 0.1, 1.0, and 10.0 ng/mL was less than 3.0% (n = 5). The proposed method has been successfully applied for the determination of urapidil in pharmaceutical preparation, human urine, and serum. The text was submitted by the authors in English.     

Peroxide-related chemiluminescence of cellulose and its self-absorption

In chemiluminometry, we measure the very faint light as a consequence of chemical reactions. During oxidation of cellulose, several reaction pathways lead to light production and in the present work we investigated chemiluminescence as a consequence of peroxide formation.With ¹³C-1 labelled glucose we studied oxidation of the end groups by following the emission of ¹³CO₂ using gas chromatography-mass spectrometry. A mechanism of peroxyacyl radical formation is suggested. Its proposed decomposition is a first-order reaction, which is reflected in chemiluminometric experiments. From these, we calculated the activation energy of the process, which depends on the temperature and is approximately 75 kJ mol⁻¹ at T > 100 °C and ∼55 kJ mol⁻¹ at T < 100 °C.Evidence is also presented on self-absorption of chemiluminescence in cellulose, suggesting that the phenomenon may account for up to 50% intensity loss.     

Determination of diethylstilbestrol by enhancement of luminol-hydrogen peroxide-tetrasulfonated cobalt phthalocyanine chemiluminescence

The ability of diethylstilbestrol to enhance the chemiluminescence reaction of luminol-H₂O₂, catalyzed by tetrasulfonated cobalt phthalocyanine in an alkaline medium, has been exploited to develop a new flow injection chemiluminescence method for the determination of diethylstilbestrol. Under the optimum conditions, the linearity of the calibration graph for the determination of diethylstilbestrol was in the range from 1.00×10⁻⁷ to 4.00×10⁻⁶ mol/l. The assay was sensitive (the detection limit was 6.42×10⁻⁸ mol/l, S/N=3), reproducible (the relative standard deviation was 2.6%, n=11), and accurate (recovery up to 92%). The method has been successfully applied to the determination of diethylstilbestrol in the pharmaceutical formulations. Dienestrol and hexestrol were specifically alkylphenols, which are similar to diethylstilbestrol, could be detected by this method. Furthermore, the enhanced mechanism of estrogen-like compounds was also discussed in this paper.     

Procedures for the enhancement of selectivity in liquid phase chemiluminescence detection

An overview of liquid phase chemiluminescence (CL) processes is presented and the potential for CL detection in liquid chromatography (LC) is discussed, with particular reference to the luminol and peroxyoxalate reactions. Post column ion displacement from a solid phase reagent [a cation exchange resin in the copper(II) form] followed by catalysis of the luminol reaction is used for the quantification of mixtures of weak acids after separation by ion-exclusion chromatography. Polyaromatic hydrocarbons (PAHs) released during the combustion of biomass fuels are separated by reversed-phase chromatography and quantified by their sensitizing effect on the peroxyoxalate reaction. This procedure is also used for the determination of carboxylic acids in non-aqueous media after selective pre-column derivatization with a fluorescent label (9-anthracenemethanol).     

Metal-nanoparticle-involved chemiluminescence and its applications in bioassays

Chemiluminescence-based bioassays have become increasingly important in clinical, pharmaceutical, environmental, and food safety fields owing to their high sensitivity, wide linear range, and simple instrumentation. During the past decade, it has been found that metal nanoparticles can initiate various liquid-phase chemiluminescence reactions as catalysts, reductants, energy acceptors, and nanosized reaction platforms owing to their unique optical, catalytic, and surface properties and chemical reactivity, which are very important for chemiluminescence bioassays based on metal nanoparticles as nanoprobes or a nanointerface. In this article, we summarize recent progress in metal-nanoparticle-initiated liquid-phase chemiluminescence, including reaction systems, mechanisms, and their applications in chemiluminescence-based bioassays, especially for immunoassays, DNA assays, aptamer-based assays, high-performance liquid chromatography or capillary electrophoresis analysis, and flow injection analysis. Figure

Comprehensive summary of metal nanoparticle (NP)-involved chemiluminescence (CL) systems and their applications. CE capillary electrophoresis, HPLC highperformance liquid chromatography     

Fluorescence enhancement of coumarin-6-sulfonyl chloride amino acid derivatives in cyclodextrin media.

Coumarin-6-sulfonyl (6-CS) amino acid derivatives form inclusion complexes with a- and /-cyclodextrins (CD) in aqueous solution. The stoichiometry of the inclusion complex and the equilibrium constant were investigated. Using a fluorescence technique and alanine-beta-CD as a model, a 1:2 guest-host complex was established, and K = 4.7 x 10(5) mol(-2) l(2) was obtained. Fluorescence enhancement was observed for all derivatives studied, with glycine exhibiting a greater enhancement, and tyrosine showing the least. The stability of the inclusion complex was found to depend on the respective sizes of the guest-host complex and their interaction.     

Electrogenerated chemiluminescence. XXIV. Electrochemistry and electrogenerated chemiluminescence of 9,10-dichloro-9,10-dihydro-9,10-diphenylanthracene

A study of the electrochemistry and electrogenerated chemiluminescence (e.c.l.) of 9,10-dichloro-9,10-dihydro-9,10-diphenylanthracene (DPACl₂) in acetonitrile solutions using rotating ring—disk electrode and stationary electrode techniques is described. The measured e.c.l. efficiency was about 0.1 to 0.8%, smaller than that observed for the corresponding DPA radical ion annihilation e.c.l. The emission is independent of applied external magnetic field, supporting the mechanism involving direct formation of emitting singlet. The e.c.l. emission and the electroreduction of DPACl₂ depend on the chloride concentration in the solution; the results suggest that this dependence is an electrode surface effect.     

Subnanogram determination of aniracetam in pharmaceutical preparations and biofluids by flow injection analysis with chemiluminescence detection based on its enhancement of the myoglobin-luminol reaction

A novel flow injection chemiluminescence method with a myoglobin-luminol system is described for determining aniracetam. Myoglobin-bound aniracetam produced a complex that catalyzed the chemiluminescence reaction between luminol and myoglobin, leading to fast chemiluminescence. The chemiluminescence intensity in the presence of aniracetam was remarkably enhanced compared with that in the absence of aniracetam. Under the optimum reaction conditions the chemiluminescence increment produced was proportional to the concentration of aniracetam in the range of 0.1-1000.0 ng/mL (R2 = 0.9992), with a detection limit of 0.03 ng/mL (3delta). At a flow rate of 2.0 mL/min, the whole process, including sampling and washing, could be completed in 0.5 min, offering a sampling efficiency of 120/h; the RSD was less than 3.0% (n = 5). The method was satisfactory for determination of aniracetam in pharmaceutical preparations and human urine and serum samples. A possible mechanism of the reaction is also discussed.     

The importance of chain length for the polyphosphate enhancement of acidic potassium permanganate chemiluminescence

Sodium polyphosphate is commonly used to enhance chemiluminescence reactions with acidic potassium permanganate through a dual enhancement mechanism, but commercially available polyphosphates vary greatly in composition. We have examined the influence of polyphosphate composition and concentration on both the dual enhancement mechanism of chemiluminescence intensity and the stability of the reagent under analytically useful conditions. The average chain length (n) provides a convenient characterisation, but materials with similar values can exhibit markedly different distributions of phosphate oligomers. There is a minimum polyphosphate chain length (∼6) required for a large enhancement of the emission intensity, but no further advantage was obtained using polyphosphate materials with much longer average chain lengths. Providing there is a sufficient average chain length, the optimum concentration of polyphosphate is dependent on the analyte and in some cases, may be lower than the quantities previously used in routine detection. However, the concentration of polyphosphate should not be lowered in permanganate reagents that have been partially reduced to form high concentrations of the key manganese(III) co-reactant, as this intermediate needs to be stabilised to prevent formation of insoluble manganese(IV).     

流动注射化学发光免疫分析研究II. 偶合反应测定HRP及其标记 物

本文详细考查了壳质胺,多孔玻璃和粗孔硅胶作为流动注射免疫分析免疫反应器基质的可行性,在此基础上将HRP催化H~2O~2氧化K~4Fe(CN)~6生成K~3Fe(CN)~6的反应,与H~2O~2和K~3Fe(CN)~6对luminol的共氧化化学发光反应相偶合首次提出了一种新的流动注射免疫分析的最终检测手段,由于酶促反应与化学发光反应在检测系统的不同位置进行,因而这种方法克服了已报道的流动注射化学发光免疫分析不能协调酶催化和化学发光反应的最佳pH,底物与酶不能充分接触及载体对光的散射等缺点,具有灵敏度高、精密度好等优点,该方法测定HRP及其标记物检测限均可达fmol级,测定时间为1-2min,相对标准偏差为3.9%。     

Strong enhancement of the chemiluminescence of the cerium(IV)-thiosulfate reaction by carbon dots,and its application to the sensitive determination of dopamine

We show that the very weak chemiluminescence (CL) of the Ce(IV)-thiosulfate system is enhanced by a factor of ~150 in the presence of fluorescent carbon dots (C-dots). The C-dots were prepared by a solvothermal method and characterized by fluorescence spectra and transmission electron microscopy. Possible mechanisms that lead to the effect were elucidated by recording fluorescence and CL spectra. It is found that dopamine at even nanomolar levels exerts a diminishing effect on the enhancement of CL. This was exploited to design a method for the determination of dopamine in the concentration range from 2.5 nM to 20 μM, with a limit of detection (at 3 s) of 1.0 nM. Dopamine was determined by this method in spiked human plasma samples with satisfactory results.