Sensitive determination of synephrine by flow-injection chemiluminescence.

It was found that light emission produced by the oxidation of luminol by potassium ferricyanide in basic medium was enhanced by synephrine, an anti-obesity drug. The optimum conditions for this chemiluminescent reaction were studied in detail in a flow injection system and employed in a new, simple and rapid method for the determination of synephrine. A mechanism for this reaction is proposed, based on the chemiluminescence reaction spectra. In the optimum conditions, CL intensity is proportional to concentration of synephrine in the 0.008-1 microg/mL range. The limit of detection is 1.6 ng/mL for synephrine (3sigma), and the relative standard deviation (n = 11) is 2.6% for 0.5 microg/mL synephrine. The method was applied to the determination of synephrine in herbal products, citrus fruit and biological fluids. The recoveries were satisfactory (90-102%). The results given by the proposed method are in good agreement with those given by HPLC-UV.     

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.     

High-performance liquid chromatography methods for the analysis of adrenergic amines and flavanones in Citrus aurantium L. var. amara

Reverse-phase HPLC coupled with photodiode array detection was used for the simultaneous separation and determination of naturally occurring adrenergic amines (octopamine, synephrine and tyramine) in fruits and dry extracts of Citrus aurantium L. var. amara and in herbal medicines derived therefrom. Synephrine was the main component in fruits (0.10-0.35%) and in dry extracts (3.00-3.08%) and was present in the range 0.25-0.99% in herbal medicines. Flavanones were analysed in the same samples using a reverse-phase HPLC technique which allowed the identification and quantification of neoeriocitrin, narirutin, naringin, hesperidin, neohesperidin, naringenin and hesperetin. C. aurantium fruits and derivatives contained mainly glycosylated flavanones: in particular, naringin and neohesperidin were found to be the major flavonoids and their concentrations ranged from 1.80 to 26.30 and from 3.90 to 14.71 mg/g, respectively. The levels of aglycones were very low in all samples tested.     

Sensitive flow-injection method with peroxyoxalate chemiluminescence detection combined with preparative high-performance liquid chromatography for determination of choline-containing phospholipids in human serum

A sensitive and rapid flow-injection analysis (FIA) of total choline-containing phospholipids (PLs) and a selective FIA method for the class assay of choline-containing PLs combined with preparative HPLC were described. The FIA method is based on peroxyoxaxalate chemiluminescence (PO-CL) detection of hydrogen peroxide enzymatically formed from choline-containing PL. The linear standard curves were obtained up to 1 nmol/20-μl injection (r>0.999) with the detection limits of 1.3–1.6 pmol at a signal-to-noise ratio of 2. The total amounts of choline-containing PLs in human serum were ranged from 1.63 to 3.19 mg/ml. The HPLC separation of choline-containing PLs was achieved with an aminopropyl-modified silica gel column using a mixture of acetonitrile-methanol-10 mM ammonium phosphate buffer pH 5.8 as eluent. The eluate corresponding to each choline-containing PL was collected, evaporated, dissolved in 0.1% Triton X-100 aqueous solution, and then injected into FIA system. The FIA method combined with preparative HPLC was applied to the assay of human serum.     

Amines for detection of dopamine by generation of hydrogen peroxide and peroxyoxalate chemiluminescence

A range of nitrogen-containing compounds (alkyl amines, piperazines, cyclohexylamines and nitrogen heterocyclics) were investigated for generation of hydrogen peroxide from dopamine and detection by peroxyoxalate chemiluminescence. Imidazole, ethyleneurea and allantoin among the nitrogen heterocyclic compounds tested generated hydrogen peroxide from dopamine following incubation at 60°C, pH 9.5–10.5, for 0–30 min. Imidazole was the most effective for generation of hydrogen peroxide, but imidazole derivatives with a primary amine side chain (histamine) or thiol (ethylenethiourea) were not effective. The presence of a ketone group (ethyleneurea, allantoin) did not hinder the reaction. Under optimal conditions (30 min incubation, 50 mmol/L imidazole) 10.5 nmol of dopamine could be detected. The cyclohexylamines tested produced low amounts of hydrogen peroxide (0.09–2.74% of light intensity with imidazole), and the piperazines and the alkyl amines tested produced no detectable hydrogen peroxide. Imidazole reacts with the phenolic groups of dopamine in a different manner from monoamine oxidase, and a reagent containing imidazole, ethyleneurea or allantoin was useful for non-enzymatic detection of dopamine by peroxyoxalate chemiluminescence.© John Wiley & Sons, Ltd.     

Antibacterial activity of wine phenolic compounds and oenological extracts against potential respiratory pathogens

Aims: To investigate the effect of seven wine phenolic compounds and six oenological phenolic extracts on the growth of pathogenic bacteria associated with respiratory diseases (Pseudomonas aeruginosa, Staphylococcus aureus, Moraxella catarrhalis, Enterococcus faecalis, Streptococcus sp Group F, Streptococcus agalactiae and Streptococcus pneumoniae). Methods and Results: Antimicrobial activity was determined using a microdilution method and quantified as IC₅₀. Mor. catarrhalis was the most susceptible specie to phenolic compounds and extracts. Gallic acid and ethyl gallate were the compounds that showed the greatest antimicrobial activity. Regarding phenolic extracts, GSE (grape seed extract) and GSE‐O (oligomeric‐rich fraction from GSE) were the ones that displayed the strongest antimicrobial effects. Conclusions: Results highlight the antimicrobial properties of wine phenolic compounds and oenological extracts against potential respiratory pathogens. The antimicrobial activity of wine phenolic compounds was influenced by the type of phenolic compounds. Gram‐negative bacteria were more susceptible than Gram‐positive bacteria to the action of phenolic compounds and extracts; however, the effect was species‐dependent. Significance and Impact of Study: The ability to inhibit the growth of respiratory pathogenic bacteria as shown by several wine phenolic compounds and oenological extracts warrants further investigations to explore the use of grape and wine preparations in oral hygiene.     

Nickel oxide hollow microsphere for the chemiluminescence determination of tuberculostatic drug isoniazid

In this article, nickel(II) oxide (NiO) hollow microspheres (HMSs) were fabricated and used to catalyze chemiluminescence (CL) reaction. The studied CL reaction is the luminol-oxygen reaction that was used as a sensitive analytical tool for measuring tuberculostatic drug isoniazid (IND) in pharmaceutical formulations and water samples. The CL method was established based on the suppression impact of IND on the CL reaction. The NiO HMSs were produced by a simple hydrothermal method and characterized by several spectroscopic techniques. The result of essential parameters on the analytical performance of the CL method, including concentrations of sodium hydroxide (NaOH), luminol, and NiO HMSs were investigated. At the optimum conditions, the calibration curve for IND was linear in the range of 8.00 × 10⁻⁷ to 1.00 × 10⁻⁴ mol L⁻¹ (R² = 0.99). A detection limit (3S) of 2.00 × 10⁻⁷ mol L⁻¹ was obtained for this method. The acceptable relative standard deviation (RSD) was obtained for the proposed CL method (2.63%, n = 10) for a 5.00 × 10⁻⁶ mol L⁻¹ IND solution. The mechanism of the CL reaction was also discussed.     

New luminol chemiluminescence reaction using diperiodatoargentate as oxidate for the determination of amikacin sulfate

A new chemiluminescence (CL) reaction between luminol and diperiodatoargentate {K₂ [Ag (H₂IO₆) (OH) ₂]} was observed in alkaline medium. The CL intensity could be greatly enhanced by amikacin sulfate. Therefore a new CL method for the determination of amikacin sulfate was built by combining with flow injection technology. A possible mechanism of the CL reaction was proposed via the investigation of the CL kinetic characteristics, the CL spectrum and the UV absorption spectra of some related substance. The concentration range of linear response was 5.1 × 10^?8 to 5.1 × 10^?6 mol L^?1 with a detection limit of 1.9 × 10^?8 mol L^?1 (3σ). The proposed method had good reproducibility with a relative standard deviation of 2.8% (n = 7) for 5.1 × 10^?7 mol L^?1 of amikacin sulfate. It was successfully applied to determine amikacin sulfate in serum. Copyright © 2009 John Wiley & Sons, Ltd.     

Flow‐injection chemiluminescence and electrogenerated chemiluminescence determination of escitalopram oxalate in tablet form

Rapid, simple and highly sensitive flow‐injection (FI) chemiluminescence (CL) and flow‐injection electrogenerated chemiluminescence (ECL) methods were developed for the determination of escitalopram oxalate (ESC), a selective serotonin reuptake inhibitor used as an antidepressant drug. The CL method was based on the CL reaction of ESC with acidic cerium(IV) and tris(2,2'‐bipyridyl)ruthenium(II) (Ru). Various experimental parameters affecting CL intensity were carefully studied and optimised. The method enabled the determination of 0.001‐50 µg/mL of ESC in bulk form with a correlation coefficient r = 0.9999. The limit of detection (LOD) was 0.01 ng/mL (S/N = 3). The ECL method was based on the ECL reaction of Ru with the drug in an acidic medium, permitting the determination of ESC in the range of 0.00001‐70 µg/mL with r = 0.9999 and LOD of 1 x 10^‐4 ng/mL. The proposed methods were applied to the determination of ESC in commercial tablets. The results were compared statistically with those obtained from a published method using t‐ and F‐tests. Copyright © 2012 John Wiley & Sons, Ltd.     

Photographic detection of fluorescent-labelled oligodeoxynucleotide in the blotting format by peroxyoxalate chemiluminescence

The preparation of a fluorescent labelled oligonucleotide and its photographic detection by peroxyoxalate chemiluminescence (PO-CL) are described. Fluorescent labelling of an oligonucleotide (15-mer) was performed with naphthalene-2,3-dicarboxaldehyde to give an N-substituted 1-cyanobenz[f]isoindole (CBI) derivative (CBI-15-mer). For the photographic detection of CBI-15-mer, the bis(2,6-difluorophenyl) oxalate (DFPO)-dimethyl phthalate (DMP) system was selected to obtain a long-lived CL emission. After optimizing the conditions for the CL reaction, the system was applied to the photographic detection, and as little as 250 fmol per spot of CBI-15-mer on a membrane were detected as a visible spot with an instant photographic film. © 1998 John Wiley & Sons, Ltd.     

Flow‐injection chemiluminescence determination of haemoglobin in the blood

In this study, a sensitive and simple flow‐injection chemiluminescence (CL) method was developed for the quantitative analysis of haemoglobin. The method is based on the ability of haemoglobin to enhance the CL signal generated by a H₂O₂–K₄Fe(CN)₆–fluorescein alkaline system enhanced by CdTe quantum dots. Under the optimized conditions, haemoglobin can be detected in concentration range 7.35 × 10^–9–2.5 × 10^–6 mol/L, with a detection limit (3σ) of 1.8 × 10^–9 mol/L and a relative standard deviation (RSD; for 5 × 10^–7 mol/L haemoglobin) of 2.06% (n = 11). The present CL method was successfully applied for the determination of haemoglobin in three kinds of blood samples taken from an infant, an adult man, an adult woman and two reference samples. Compared with previous reports, the CL method described in this work is simple and rapid, with high sensitivity. Copyright © 2012 John Wiley & Sons, Ltd.     

A novel chemiluminescence system for the determination of daidzein and its hydroxyl radical-scavenging capacity

A novel chemiluminescence (CL) system was established for the determinations of daidzein in pharmaceutical preparations and to assess its ability to scavenge hydroxyl radicals. It was shown that a strong CL signal generated when eosin Y was mixed with Fenton reagent was decreased significantly when daidzein was added to the reaction system due to partial scavenging of the hydroxyl radicals in the solution. The extent of decrease in the CL intensity had a good stoichiometric relationship with the daidzein concentration. Based on this, we developed a new method for the determination of daidzein, using a flow‐injection chemiluminescence (FI–CL) technique. Under the optimal conditions, the linear range of daidzein concentration was 8.0 × 10^–8–3.0 × 10^–6 mol/L (R = 0.9982), with a detection limit of 9.0 × 10^–9 mol/L (S:N = 3), and the RSD was 5.8% for 1.0 × 10^–6 mol/L daidzein (n = 11). This method was successfully used in the determination of daidzein in tablets and for evaluation of the hydroxyl radical‐scavenging capacity of daidzein. The possible reaction mechanism of the CL system is discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

Flow‐injection chemiluminescence method for the determination of naphazoline hydrochloride and oxymetazoline hydrochloride

A sensitive and simple flow‐injection chemiluminescence (FI‐CL) method, which was based on the CL intensity generated from the redoxreaction of potassium permanganate (KMnO₄)–formaldehyde in vitriol (H₂SO₄) medium, has been developed, validated and applied for the determination of naphazoline hydrochloride and oxymetazoline hydrochloride. Besides oxidants and sensitizers, the effect of the concentration of H₂SO₄, KMnO₄ and formaldehyde was investigated. Under the optimum conditions, the linear range was 1.0 × 10^?2–7.0 mg/L for naphazoline hydrochloride and 5.0 × 10^?2–10.0 mg/L for oxymetazoline hydrochloride. During seven repeated inter‐day and intra‐day precision tests of 0.1, 1.0 and 10.0 mg/L samples, the relative standard deviations all corresponded to reference values. The detection limit was 8.69 × 10^?3 mg/L for naphazoline hydrochloride and 3.47 × 10^?2 mg/L for oxymetazoline hydrochloride (signal‐to‐noise ratio ≤3). This method has been successfully implemented for the determination of naphazoline hydrochloride and oxymetazoline hydrochloride in pharmaceuticals. Copyright © 2009 John Wiley & Sons, Ltd.     

Potassium permanganate–acridine yellow chemiluminescence system for the determination of fluvoxamine,isoniazid and ceftriaxone

Based on the oxidation of acridine yellow by permanganate in basic medium, a new chemiluminescence system was developed for the sensitive determination of some important drugs. The remarkable inhibiting effect of fluvoxamine, ceftriaxone and isoniazid on this reaction was applied to their detection. A possible mechanism was proposed for this system based on chemiluminescence emission wavelengths and experimental observations. Under optimum conditions, calibration graphs were obtained for 1 × 10^?9 to 1 × 10^?6 mol/L of fluvoxamine; 2 × 10^?8 to 8 × 10^?6 mol/L of ceftriaxone and 5 × 10^?8 to 4 × 10^?5 mol/L of isoniazid. This proposed method was satisfactorily used in the determination of these drugs in pharmaceutical samples and human urine and serum. Copyright © 2014 John Wiley & Sons, Ltd.     

Comparison of the performance of the borax buffer-based HRP-enhanced reagent and the ‘Lumi-Phos 530’ chemiluminescence systems in the detection of biotinylated DNA

A comparison of two chemiluminescence methods, the borax buffer-based HRP-enhanced reagent and Lumi-Phos 530, applied to the detection of a biotinylated 30-mer DNA slot blotted onto a nylon membrane, is presented. A streptavidin–HRP and streptavidin–ALP mediated detection system was used. The HRP-enhanced system is up to 15-fold greater with respect to the signal/background ratios than the Lumi-Phos 530 system at 0.5 μg biotinylated DNA with at least a two-fold improvement in detection sensitivity for 0.5 ng biotinylated DNA.     

Enhanced chemiluminescence enzyme‐linked immunoassay for the determination of DNA methyltransferase 1 in human serum

The occurrence of many diseases is closely related to the high expression of DNA methyltransferase 1 (DNMT1). However, most studies are focused on the detection of DNMT1 activity, a few are concerned with the detection of DNMT1 content. In this study, we developed a simple and highly sensitive chemiluminescence (CL) assay for the detection of DNMT1 content. In this method, anti‐DNMT1 monoclonal antibody was coated on a polystyrene microplate to capture DNMT1. Then anti‐DNMT1 polyclonal antibody and goat anti‐rabbit immunoglobulin G with horseradish peroxidase (IgG‐HRP) were respectively added to combine with captured DNMT1 to form a sandwich structure. Finally, the HRP could catalyze CL substrate and achieve CL signal response. Based on this novel sensitive strategy, the recovery percents were in the ranges from 71.5% to 91.0%. The precision of intra‐assays and inter‐assays were 5.45%–11.29% and 7.03%–11.25%, respectively. The method was successfully applied for the determination of DNMT1 in human serum. The detection results of serum samples showed that the proposed assay had a high correlation with enzyme‐linked immunosorbent assay (ELISA) kit. Compared with the ELISA kit (limit of detection = 0.1 ng/mL), the method has a lower limit of detection of 0.042 ng/mL. Therefore, our method has the potential for the detection of DNMT1 content in clinical diagnosis.     

CdS nanoparticles‐ enhanced chemiluminescence and determination of baicalin in pharmaceutical preparations

CdS nanoparticles (CdS NPs) of different sizes were synthesized by the citrate reduction method. It was found that CdS NPs could enhance the chemiluminescence (CL) of the luminol‐potassium ferricyanide system and baicalin could inhibit CdS NPs‐enhanced luminol‐potassium ferricyanide CL signals in alkaline solution. Based on this inhibition, a flow‐injection CL method was established for determination of baicalin in pharmaceutical preparations and human urine samples. Under optimized conditions, the linear range for determination of baicalin was 5.0 x 10^?6 to 1.0 x 10^?3 g/L. The detection limit at a signal‐to‐noise ratio of 3 was 1.7 x 10 ^?6 g/L. CL spectra, UV‐visible spectra and transmission electron microscopy (TEM) were used to investigate the CL mechanism. The method described is simple, selective and obviates the need of extensive sample pretreatment. Copyright © 2012 John Wiley & Sons, Ltd.     

Flow‐injection chemiluminescence determination of melamine in urine and plasma

A novel flow‐injection chemiluminescence method for the determination of melamine in urine and plasma was developed. It was found that melamine can remarkably enhance chemiluminescence emission from the luminol–K₃Fe(CN)₆ system in an alkaline medium. Under the optimum conditions, chemiluminescence intensity had a good linear relationship with the concentration of melamine in the range 9.0 × 10^–9–7.0 × 10^–6 g/mL, with a correlation coefficient of 0.9992. The detection limit (3σ) was 3.5 ng/mL. The method has been applied to determine the concentration of melamine in samples using liquid–liquid extraction. Average recoveries of melamine were 102.6% in urine samples and 95.1% in plasma samples. The method provided a reproducible and stable approach for the sensitive detection of melamine in urine and plasma samples. Copyright © 2011 John Wiley & Sons, Ltd.     

A new sensitive flow-injection chemiluminescence method for the determination of H(2)-receptor antagonists.

Based on the chemiluminescence (CL) intensity generated from the potassium ferricyanide [K(3)Fe(CN)(6)]-rhodamine 6G system in sodium hydroxide (NaOH) medium, a new sensitive flow-injection chemiluminescence (FI-CL) method has been developed, validated and applied for the determination of three kinds of H(2)-receptor antagonists: cimetidine (CIMT), ranitidine (RANT) hydrochloride and famotidine (FAMT). Under the optimum conditions, the linear range for the determination was 1.0 x 10(-9)-7.0 x 10(-5) g/ml for CIMT, 1.0 x 10(-9)-5.0 x 10(-5) g/mL for RANT hydrochloride and 5.0 x 10(-9)-7.0 x 10(-5) g/mL for FAMT. During 11 repeated measurements of 1.0 x 10(-6) g/mL sample solutions, the relative standard deviations (RSDs) were all <5%. The detection limit was 8.56 x 10(-10) g/mL for CIMT, 8.69 x 10(-10) g/mL for RANT hydrochloride and 2.35 x 10(-9) g/mL for FAMT (S:N = 3). This method has been successfully implemented for the analysis of H(2)-receptor antagonists in pharmaceuticals.     

Carbon dots-modified paper-based chemiluminescence device for rapid determination of mercury (II) in cosmetics

Here, a simple and portable paper-based analytical device (PAD) based on the inherent capability of carbon quantum dots (CQDs) to serve as a great emitter for the bis(2,4,6-trichlorophenyl)oxalate (TCPO)–hydrogen peroxide (H₂O₂) chemiluminescence (CL) reaction is introduced for the detection of harmful mercury ions (Hg²⁺). The energy is transferred from the unstable reaction intermediate (1,2-dioxetanedione) to CQDs, as acceptors, and an intensive orange-red CL emission is generated at ~600 nm, which is equal to the fluorescence emission wavelength of CQDs. The analytical applicability of this system was examined for the determination of Hg²⁺. It was observed that Hg²⁺ could significantly quench the produced emission, which can be attributed to the formation of a stable and nonluminescent Hg²⁺–CQDs complex. Accordingly, a simple and rapid PAD was established for monitoring Hg²⁺, with a limit of detection of 0.04 μg ml⁻¹. No interfering effect on the signal was found from other examined cations, indicating the acceptable specificity of the method. The designed assay was appropriately utilized to detect Hg²⁺ ions in cosmetic samples with high efficiency. It was characterized by its low cost, ease of use, and was facile but accurate and high selective for the detection of Hg²⁺ ions. In addition, the portability of this probe makes it suitable for on-site screening purposes.