Light emitting diode induced chemiluminescence and its application as a detector for high performance liquid chromatography

Some categories of compounds, including quinones, coumarins, flavins, and xanthene dyes, were found to produce strong chemiluminescence (CL) signals with luminol in sample solution under the irradiation of light emitting diodes (LED) with proper wavelengths. Based on this phenomenon, a compact photochemical reactor was constructed to develop a novel LED induced CL detector for high performance liquid chromatography (HPLC). The effects of related parameters including LED wavelength, luminol concentration, flow rate, pH, and eluents of HPLC were investigated in detail. Under the optimized conditions, the limits of detections (LODs) were in the range of 0.2–80 ng mL⁻¹. The applications and accuracy of the proposed method were validated by analyzing food samples such as milk powder, beer, candy and beverage with satisfactory results.     

Chemiluminescence determination of carbofuran at trace levels in lettuce and waters by flow-injection analysis

A simple, fast chemiluminescence (CL) flow-injection (FI) method based on the reaction of luminol with KMnO₄ in alkaline medium has been described for the direct determination of carbofuran. The method is based on the enhancing effect in the emission light from the oxidation of luminol produced in presence of carbofuran. The optimisation of instrumental and chemical variables influencing the CL response of the method has been carried out by applying experimental design, using the proposed flow-injection manifold. Under the optimal conditions, the CL intensity was linear for a carbofuran concentration over the range of 0.06-0.5 μg ml⁻¹, with a detection limit of 0.02 μg ml⁻¹. The method has been successfully applied to the determination of carbofuran residues in spiked water and lettuce samples.     

Determination of bromide ions in seawater using flow system with chemiluminescence detection

A simple flow-based procedure with chemiluminescence (CL) detection is proposed for bromide ion determination in seawater. The procedure was based on the oxidation of bromide to bromine by chloramine-T followed by the reaction of bromine with luminol resulting in CL emission. Since no significant reaction within chloramine-T and luminol was observed, the detection was carried out without bromine extraction from the oxidant medium. The proposed flow system had a sampling rate of 40 determinations per hour, reagents consumption of 100 μg luminol and 60 μg chloramine-T per determination, a limit of detection of 0.5 mg l⁻¹ bromide ions, a linear concentration range (r = 0.999 and n = 7) between 0 and 100 mg l⁻¹, and a coefficient of variance better than 2.5% (for 10 measurements of a 10 mg l⁻¹ Br⁻ solution) were achieved. The analytical system was applied for the determination of bromide in seawater and estuarine-water samples, obtaining an analyte recovery ranging from 94 to 102% and comparing the results with a reference spectrophotometric method no significant difference was observed in 95% confidence level.     

Gold nanorod-catalyzed luminol chemiluminescence and its selective determination of glutathione in the cell extracts of Saccharomyces cerevisiae

In this study, gold nanorods were firstly found to exhibit a tremendously higher catalytic activity towards luminol chemiluminescence (CL) than spherical gold nanoparticles. More importantly, ultra-trace aminothiols can cause a great CL decrease in the gold nanorod-catalyzed luminol system by the formation of Au-S covalent bonds on the ends of gold nanorods. Aminothiols can occupy the active sites of gold nanorods, and further interrupt the generation of the active oxygen intermediates. Other biomolecules including 19 standard amino acids, alcohols, organic acids and saccharides have no effect on gold nanorod-catalyzed luminol CL signals. Moreover, in order to evaluate the applicability and reliability of the proposed method, it was applied to the determination of glutathione in the cell extracts of Saccharomyces cerevisiae. Good agreements were obtained for the determination of glutathione in the cell extracts of S. cerevisiae between the present approach and a standard Alloxan method. The recoveries of glutathione were found to fall in the range between 96 and 105%. The calibration curve for glutathione was found to be linear from 0.05 to 100 nM, and the detection limit (S/N = 3) was 0.01 nM. The relative standard deviation (RSD) for five repeated measurements of 5.0 nM glutathione was 2.1%.     

Chemiluminescence assay for quinones based on generation of reactive oxygen species through the redox cycle of quinone

A sensitive and selective chemiluminescence assay for the determination of quinones was developed. The method was based on generation of reactive oxygen species through the redox reaction between quinone and dithiothreitol as reductant, and then the generated reactive oxygen was detected by luminol chemiluminescence. The chemiluminescence was intense, long-lived, and proportional to quinone concentration. It is concluded that superoxide anion was involved in the proposed chemiluminescence reaction because the chemiluminescence intensity was decreased only in the presence of superoxide dismutase. Among the tested quinones, the chemiluminescence was observed from 9,10-phenanthrenequinone, 1,2-naphthoquinone, and 1,4-naphthoquinone, whereas it was not observed from 9,10-anthraquinone and 1,4-benzoquinone. The chemiluminescence property was greatly different according to the structure of quinones. The chemiluminescence was also observed for biologically important quinones such as ubiquinone. Therefore, a simple and rapid assay for ubiquinone in pharmaceutical preparation was developed based on the proposed chemiluminescence reaction. The detection limit (blank + 3SD) of ubiquinone was 0.05 μM (9 ng/assay) with an analysis time of 30 s per sample. The developed assay allowed the direct determination of ubiquinone in pharmaceutical preparation without any purification procedure. Figure Chemiluminescence generated through the redox cycle of quinone     

Determination of N-methylcarbamate pesticides in water and vegetable samples by HPLC with post-column chemiluminescence detection using the luminol reaction

In this paper we proposed a reverse high performance liquid chromatography method for the simultaneous determination of three N-methylcarbamates (NMCs) named carbofuran, carbaryl and methiocarb, using the post-column chemiluminescence (CL) detection with the luminol reaction. This method is based on the enhancing effect of these analytes on the CL emission generated by the oxidation of luminol with potassium permanganate in alkaline medium. The separation was reached in less than 14 min using a C18 column and an isocratic binary mobile phase consisting of acetonitrile:water (50:50, v/v) pumped at a flow rate of 1 mL min⁻¹. CL reagents (luminol and KMnO₄) were incorporated by means of a peristaltic pump and were firstly mixed using a three-way connector. Then this stream was mixed with the eluate using another three-way connector just before reaching the detection cell. The optimization of variables affecting the CL reaction (reaction medium, concentration, flow rate of reagents and distance between both connectors) were optimized by means of experimental designs. Ethiofencarb, a NMC which has nowadays fallen into disuse was used as internal standard. For the analysis of theses pesticides in real water samples a pre-treatment step consisting of solid phase extraction (SPE) was conducted in order to reach sensitivity levels below the legal maximum concentration permitted. In the case of vegetable sample, SPE was used for matrix cleaning purpose.     

Sensitive determination of phenothiazines in pharmaceutical preparation and biological fluid by flow injection chemiluminescence method using luminol-KMnO4 system

A flow injection chemiluminescence method was described for the determination of four phenothiazine drugs, namely, chlorpromazine hydrochloride, perphenazine hydrochloride, fluphenazine hydrochloride and thioridazine hydrochloride. Strong Chemiluminescence (CL) signal was produced when above-mentioned drug was injected into the mixed stream of luminol with KMnO₄. The linear ranges of the method were 0.0020-1.0 μg/mL chlorpromazine hydrochloride, 0.0040-3.0 μg/mL perphenazine hydrochloride, 0.0020-5.0 μg/mL fluphenazine hydrochloride and 0.0050-1.0 μg/mL thioridazine hydrochloride. The detection limits were 0.4 ng/mL chlorpromazine hydrochloride, 0.7 ng/mL perphenazine hydrochloride, 2 ng/mL fluphenazine hydrochloride and 0.7 ng/mL thioridazine hydrochloride. The proposed method was applied to the determination of chlorpromazine hydrochloride in injections and in mental patient's urine samples and the satisfactory results were achieved. The possible CL reaction mechanism was also discussed briefly.     

Effect of gold nanoparticle as a novel nanocatalyst on luminol-hydrazine chemiluminescence system and its analytical application

In this work the catalytic role of unsupported gold nanoparticles on the luminol–hydrazine reaction is investigated. Gold nanoparticles catalyze the reaction of hydrazine and dissolved oxygen to generate hydrogen peroxide and also catalyze the oxidation of luminol by the produced hydrogen peroxide. The result is an intense chemiluminescence (CL) due to the excited 3-aminophthalate anion. In the absence of gold nanoparticles no detectable CL was observed by the reaction of luminol and hydrazine unless an external oxidant is present in the system. The size effect of gold nanoparticles on the CL intensity was investigated. The most intensive CL signals were obtained with 15-nm gold nanoparticles. UV–vis spectra and transmission electron microscopy studies were used to investigate the CL mechanism. The luminol and hydroxide ion concentration, gold nanoparticles size and flow rate were optimized. The proposed method was successfully applied to the determination of hydrazine in boiler feed water samples. Between 0.1 and 30 μM of hydrazine could be determined with a detection limit of 30 nM.     

Determination of thyroxine hormone by luminol chemiluminescence

A chemiluminescence (CL) flow system for determination of thyroxine (Thy) is presented. It is based on the catalytic effect of cobalt(II) on the CL reaction between luminol and hydrogen peroxide. The iodinated chemical structure of Thy causes a heavy atom effect. The luminol CL signals show significant quenching by Thy. The calibration graph for Thy is linear for 15-70 μg ml⁻¹ and the 3σ detection limits are 27 μg ml⁻¹ for d-Thy and 23 μg ml⁻¹ for l-Thy.     

Sensitive determination of captopril by flow injection analysis with chemiluminescence detection based on the enhancement of the luminol reaction

This work reports a novel flow injection (FI) method for the determination of captopril, 1-[(2S)-3-mercapto-2-methylpropionyl]-l-proline (CPL), based on the enhancement CPL affords on the chemiluminescence (CL) reaction between luminol and hydrogen peroxide. For this purpose alkaline luminol and hydrogen peroxide solutions were mixed online, the sample containing CPL was injected into an aqueous carrier stream, mixed with the luminol-hydrogen peroxide stream and pumped into a glass flow cell positioned in front of a photomultiplier tube (PMT). The increase in the CL intensity was recorded in the form of FI peaks, the height of which was related to the CPL mass concentration in the sample. Different chemical and instrumental parameters affecting the CL response were investigated. Under the selected conditions, the log-log calibration curve was linear in the range 5-5000 μg l⁻¹ of CPL, the limit of detection was 2 μg l⁻¹ (at the 3σ level), the R.S.D., s_r was 3.1% at the 100 μg l⁻¹ level (n=8) and the sampling rate was 180 injections h⁻¹. The method was applied to the determination of CPL in pharmaceutical formulations with recoveries in the range 100±3%.     

A Sensitive Photoinduced Chemiluminescence Method for the Determination of Riboflavin with Flow Injection Analysis

ABSTRACT

A sensitive chemiluminescence (CL) induced by light for the determination of riboflavin with flow injection analysis is developed. Riboflavin shows a strong enhancement effect on the CL reaction of luminol oxidized by periodate after the photochemical reaction of riboflavin in alkaline solution, and the enhancing effect of riboflavin disappears under dark conditions. Oxygen can further improve the enhancing effect of the riboflavin in this CL system, and the effects were also investigated. And based on this phenomenon, a very sensitive method of various surfactants, β-cyclodextrin and organic solvents on this CL system for the determination of riboflavin was described. The range of the linear response for riboflavin using this method is ca. 2.4×10^?8 ~ 1.0 × 10^?6 mol/L, and the detection limit (S/N = 3) is l.0×10^?8 mol/L. The applicability of the method was demonstrated by the determination of riboflavin in pharmaceutical preparation.     

Flow injection determination of cationic surfactants by using N-bromosuccinimide and N-chlorosuccinimide as new oxidizing agents for luminol chemiluminescence

Two highly sensitive chemiluminescence (CL) systems are described. The method is based on the CL generated during the oxidation of luminol by N-bromosuccinimide (NBS) and N-chlorosuccinimide (NCS) in alkaline medium. The emission intensity is reduced by the presence of some surfactants at concentrations lower than critical micelle concentration (cmc).A new, simple, rapid and selective flow injection CL method for the determination of cationic surfactants such as dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC) is proposed. Their determinations are based on the reducing effect on the emission intensity of NBS-luminol and NCS-luminol chemiluminescent reactions. The effect of analytical and flow injection analysis (FIA) variables on these CL systems and on the determination of the cationic surfactants are discussed. The optimum parameters for the determination of cationic surfactants were studied and were found to be the following: luminol, 1×10⁻⁶ M; NBS and NCS both, 5×10⁻² M; NaOH, 5×10⁻² M and flow rate, 3.5 ml min⁻¹.     

Sub-picogram determination of Vitamin B12 in pharmaceuticals and human serum using flow injection with chemiluminescence detection

A sensitive chemiluminescence (CL) method, based on the enhancive effect of cobalt(II) on the CL reaction between luminol and dissolved oxygen in a flow injection (FI) system, was proposed for determination of Vitamin B₁₂. The increment of the CL intensity was proportional to the concentration of Vitamin B₁₂, giving a calibration graph linear over the concentration from 2.0×10⁻¹⁰ to 1.2×10⁻⁶ g l⁻¹ (r²=0.9992) with the detection limit of 5.0×10⁻¹¹ g l⁻¹ (3σ). At a flow rate of 2.0 ml min⁻¹, a complete determination of Vitamin B₁₂, including sampling and washing, could be accomplished in 0.5 min with the relative standard deviations (R.S.D.) of less than 5.0%. The proposed method was applied successfully to the determination of Vitamin B₁₂ in pharmaceuticals, human serum, egg yolk and fish tissue.     

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.     

Selective chemiluminescence method for monitoring of vitamin K homologues in rheumatoid arthritis patients

Vitamin K is a fat-soluble vitamin involved in blood coagulation and bone metabolism. The detection and monitoring of vitamin K homologues in rheumatoid arthritis (RA) patients is a challenging problem due to the smaller concentrations of vitamin K and the presence of several interfering medications. Therefore, this study aimed to develop a new highly sensitive and selective chemiluminescence (CL) method designated to quantify vitamin K homologues in plasma of RA patients including phylloquinone (PK, vitamin K₁), menaquinone-4 (MK-4, vitamin K₂) and menaquinone-7 (MK-7, vitamin K₂). The method was based on the unique photochemical properties of vitamin K homologues that were exploited for selective luminol CL reaction. The correlation coefficients of 0.998 or more were obtained in the concentration ranges of 0.1-100 ng mL⁻¹ vitamin K homologues. The detection limits were 0.03-0.1 ng mL⁻¹ in human plasma for vitamin K homologues. The developed HPLC-CL system was successfully applied for selective determination of vitamin K homologues in plasma of RA patients. The developed method may provide a useful tool for monitoring vitamin K homologues in different clinical studies such as RA, osteoporosis and hepatocellular carcinoma in which vitamin K is intervented.     

Determination of levodopa by capillary electrophoresis with chemiluminescence detection

A rapid and simple method using capillary electrophoresis (CE) with chemiluminescence (CL) detection was developed for the determination of levodopa. This method was based on enhance effect of levodopa on the CL reaction between luminol and potassium hexacyanoferrate(III) (K₃[Fe(CN)₆]) in alkaline aqueous solution. CL detection employed a lab-built reaction flow cell and a photon counter. The optimized conditions for the CL detection were 1.0 × 10⁻⁵ M luminol added to the CE running buffer and 5.0 × 10⁻⁵ M K₃[Fe(CN)₆] in 0.6 M NaOH solution introduced postcolumn. Under the optimal conditions, a linear range from 5.0 × 10⁻⁸ to 2.5 × 10⁻⁶ M (r = 9991), and a detection limit of 2.0 × 10⁻⁸ M (signal/noise = 3) for levodopa were achieved. The precision (R.S.D.) on peak area (at 5.0 × 10⁻⁷ M of levodopa, n = 11) was 4.1%. The applicability of the method for the analysis of pharmaceutical and human plasma samples was examined.     

Sensitive determination of sub-nanogram amounts of rutin by its inhibition on chemiluminescence with immobilized reagents

An interesting inhibitory effect of rutin on the chemiluminescence (CL) reaction between luminol and periodate was reported, and this effect was used for the determination of rutin in medicine and human urine. The CL reagents, luminol and periodate, were both immobilized on an anion-exchange column. The CL signal produced by the reaction between luminol and periodate, which were eluted from the column through water injection, was decreased in the presence of rutin. Rutin was sensed by measuring the decrement of CL intensity, and which was observed to be linear over the logarithm of 0.1-30 ngml(-1) rutin concentration range, and the limit of detection was 0.03 ngml(-1) (3sigma). At a flow rate of 2.0 mlmin(-1), both sampling and washing could be performed in 0.5 min with a relative standard deviation of less than 3.0%. The method proposed offered reagent-less procedures and remarkable stability in the determination of rutin, and could be easily reused over 80 h. The method proposed was applied successfully in the determination of rutin in pharmaceutical preparations and monitoring the excretion of rutin in human urine.     

Determination of methimazole and carbimazole by flow-injection with chemiluminescence detection based on the inhibition of the Cu(II)-catalysed luminol-hydrogen peroxide reaction

This paper reports an indirect flow-injection (FI) method for the determination of the anti-hyperthyroid drugs methimazole and carbimazole in pharmaceuticals. The method was based on the inhibition that these thioimidazole drugs caused on the Cu(II)-catalysed chemiluminescence (CL) reaction between luminol and H₂O₂. The CL reaction was induced on-line and injection of the sample produced negative peaks as a result of the Cu(II) complexation by the analytes. The height of the FI peaks was proportional to the drug concentration in the sample. The linear range was 2-100 and 3-120 mg l⁻¹ for methimazole and carbimazole, respectively. The relative standard deviation was 1.9% for methimazole and 2.1% for carbimazole at the 50 mg l⁻¹ level (n=10). Common excipients present in pharmaceutical tablets were found not to interfere with the analysis. The method was applied to the determination of methimazole and carbimazole in pharmaceutical formulations with recoveries in the range 100±4%.     

Chemiluminescence of Colloidal MnO2 with Luminol and Determination of Polyhydroxyl Compounds

The reaction between luminol and colloidal MnO₂ (prepared by chemical reduction of KMnO₄ with Na₂S₂O₃ under neutral aqueous condition) produced an intense chemiluminescence (CL) emission in alkaline medium. The CL reaction conditions were carefully optimized and the CL reaction mechanism was thoroughly discussed. Manganese(III) was suggested to be involved in the reaction and 3‐aminophthalate anion was the luminophor. Moreover, the effects of 23 compounds on the colloidal MnO₂‐luminol CL system were investigated to explore its possible analytical applications. Polyhydroxyl compounds were observed to inhibit the signal significantly, whereas sulfhydryl compounds enhance it slightly. The analytical figures for five polyhydroxyl compounds, namely ascorbic acid, rutin, pyrogallol, quercetin, and L‐adrenaline, were presented. As a preliminary application, the method was applied to the determination of rutin in pharmaceutical formulations.     

Flow-injection chemiluminescence determinations for human blood lead using controlled reagent release technology

A flow-through CL method for the determination of lead combined with controlled-reagent-release technology has been developed. Chemiluminescence (CL) reagents luminol and potassium permanganate were immobilized on anion exchange resin by electrostatic interaction. Lead ion was determined by its enhancing effect on the CL reaction between luminol and potassium permanganate. Both luminol and potassium permanganate were eluted from the anion exchange resin column by sodium phosphate solution. The linear range of the system was 10 μg mL^?1, and the detection limit was 5?×?10^–9 g mL^?1 lead (3σ). A complete analysis could be performed in 1 min with a relative SD 3.2% (1.0?×?10^–7 g mL^?1, n?=?9). The column shows remarkable stability and can be reused over 350 times and 21 days. The method has been applied to determine lead in human blood samples.