CL Emission Research Articles

A microfluidic system for evaluation of antioxidant capacity based on a peroxyoxalate chemiluminescence assay

A microfluidic system incorporating chemiluminescence detection is reported as a new tool for measuring antioxidant capacity. The detection is based on a peroxyoxalate chemiluminescence (PO-CL) assay with 9,10-bis-(phenylethynyl)anthracene (BPEA) as the fluorescent probe and hydrogen peroxide as the oxidant. Antioxidant plugs injected into the hydrogen peroxide stream result in inhibition of the CL emission which can be quantified and correlated with antioxidant capacity. The PO-CL assay is performed in 800-microm-wide and 800-microm-deep microchannels on a poly(dimethylsiloxane) (PDMS) microchip. Controlled injection of the antioxidant plugs is performed through an injection valve. Of the plant-food based antioxidants tested, beta-carotene was found to be the most efficient hydrogen peroxide scavenger (SAHP of 3.27x10(-3) micromol-1 L), followed by alpha-tocopherol (SAHP of 2.36x10(-3) micromol-1 L) and quercetin (SAHP of 0.31x10(-3) micromol-1 L). Although the method is inherently simple and rapid, excellent analytical performance is afforded in terms of sensitivity, dynamic range, and precision, with RSD values typically below 1.5%. We expect our microfluidic devices to be used for in-the-field antioxidant capacity screening of plant-sourced food and pharmaceutical supplements.

Optical sensors based on III-nitride photodetectors for flame sensing and combustion monitoring

Combustion control requires visible photodetectors to sense the CH* CL emission at 430 nm that combined with a visible-blind UV photodetector allows us to obtain the OH*/CH* ratio. UV-visible P-InGaN/GaN multiple quantum well-N photodiodes with 15-18 mm2 areas were fabricated to conduct OH* (308 nm) and CH* CL detection without external filters. Bandpass detectors at 230-390 nm and 360-450 nm presented linear responses over five decades and rejection ratios >10(3) at 430 and 308 nm, respectively. A full optical sensor system was built and detectors operated at 120 degrees C in a combustion chamber, showing linear responses within the dynamic range, maximum signal-to-noise ratios of 103 and response times of <1 s. An exponential association dependence between the optical OH*/CH* CL signals and the gas/air ratios was found.

Luminescence Characterisation of the Reaction System Histidine–KBrO3–Tb(III)–H2SO4

Chemiluminescence of the system containing Tb(III) ions, histidine and bromate ions in acid solution was studied. The kinetic curves and CL emission spectra of the system were discussed. The emission spectrum of the histidine-Tb(III)-KBrO3-H2SO4 system revealed two emission maxima at approximately 490 and 550 nm, characteristic of Tb(III) ions. Values of lifetimes of the Eu(III) excited states in Eu(III)-histidine system have shown that the histidine formed ML and ML2 complexes in neutral solution and did not make them in acidic environment. On the basis of the results, a possible mechanism of reaction system: histidine-Tb(III)-KBrO3-H2SO4 is presented.

Real-time chemiluminescent imaging and detection of reactive oxygen species generated in the UVB-exposed human skin equivalent model

The objective of this study is to image and detect reactive oxygen species (ROS) generated in the UVB-exposed three-dimensional human skin equivalent model (HSEM), EpiDerm™ 200, because the alternative system needs to be urgently established as a replacement for the skin of experimental animals. Evidence that the ROS generation is enhanced in the skin of live animals after the UVB exposure was already obtained, by using the real-time chemiluminescent (RT-CL) method consisting of a sensitive CL probe (CLA) and an ultra-low light imaging apparatus. In this study, CL emission due to the reaction of CLA with endogenously generated ROS increased significantly in the UVB-treated HSEM compared with that in the intact HSEM, the maximum level being observed at a dose of 27 mJ/cm 2. ROS under UVB exposure was identified to be O 2 - and 1O 2 as observed by suppressive effects of SOD and β-carotene topically applied on sample surface before the UVB exposure. The results for UVB-induced ROS generation in HSEM were consistent with those observed in the skin of live animals. HSEM combined with the RT-CL method was shown to be useful system not only to predict UVB-induced ROS-related skin responses in human but also to find protective agents against UVB-stimulated oxidative stress in place of animals and ex vivo human skin.

Antibacterial and antioxidant activities in Sideritis italica (Miller) Greuter et Burdet essential oils

Sideritis italica (Miller) Greuter et Burdet is a widespread Lamiacea in the Mediterranean region used in traditional medicine. Essential oils were antibacterial against nine ATCC and as many clinically isolated Gram-positive and Gram-negative bacterial strains. Antibacterial activity was also found against Helicobacter pylori: a dose-dependant inhibition was shown between 5 and 25 μg/ml. The antibacterial activity of the oils was expressed as MICs (minimum inhibitory concentrations) and MBCs (minimum bactericidal concentrations). At a concentration between 3.9 and 250 μg/ml the oils showed a significant antibacterial effect against both Gram-negative and Gram-positive bacteria. In particular the ATCC strains Pseudomonas aeruginosa (MIC = 3.9 μg/ml and 7.8 for flowerheads and leaves, respectively) , Proteus mirabilis (MIC = 15.6 and 7.8 μg/ml) , Salmonella typhi (MIC = 7.8 μg/ml) and Proteus vulgaris (MIC = 15.6 μg/ml) were the most inhibited. Only Pseudomonas aeruginosa showed MBC at a concentration between 62.6 and 125 μg/ml. The antioxidant activity of the essential oils was evaluated by two cell free colorimetric methods: ABTS and DMPD; leaf oil is more active (4.29 ± 0.02 trolox equivalents and 4.53 ± 0.67 ascorbic acid equivalents by ABTS and DMPD, respectively). Finally the antioxidant activity of the essential oils was also evaluated by their effects on human whole blood leukocytes (WB) and on isolated polymorphonucleate (PMN) chemiluminescence. Comparing the effects of the oils from leaves and flowerheads on both PMN and WB chemiluminescence emission, we found no significant differences. Essential oils showed a dose-dependent and linear inhibitory activity on isolated PMN as well as on WB CL emission when PMA-stimulated. On the contrary, the inhibitory activity on resting cells was nonlinear. Our data represent an answer to the continual demand for new antibiotics and antioxidants for the continuous emergence of antibiotic-resistant strains and the growing interest in the substitution of synthetic antioxidants with natural ones. Furthermore, our finding of antibacterial and antioxidant activities in the essential oils from Sideritis italica flowerheads and leaves validated the use of the plant for medical purposes.

Flow-injection enhanced chemiluminescence method for determination of ciprofloxacin in pharmaceutical preparations and biological fluids

A novel rapid and sensitive analytical method, enhanced chemiluminescence with flow-injection sampling, is described for determination of ciprofloxacin. The method is based on the chemiluminescence reaction of the potassium permanganate-sodium thiosulfate-ciprofloxacin system. An enhanced chemiluminescence reaction was developed, and optimum conditions for CL emission were investigated. The chemiluminescence intensity was linearly dependent on ciprofloxacin concentration in the range 1.0 x 10(-8)-1.0 x 10(-5) g mL(-1). The detection limit was 4 x 10(-9) g mL(-1). The relative standard deviation was 1.8% for eleven measurements of 2.0 x 10(-7) g mL(-1) ciprofloxacin standard solution. The new method enables simple, sensitive, and rapid determination of ciprofloxacin and has been successfully used for determination of ciprofloxacin in biological fluids and in ciprofloxacin hydrochloride tablet and injection.

Determination of gentamicin in pharmaceutical formulations using peroxyoxalate chemiluminescent detection in flow-injection analysis

A simple and sensitive procedure for the determination of gentamicin is presented, based on the use of the peroxyoxalate chemiluminescent (PO-CL) system in presence of imidazole as a catalyst. The gentamicin has to be previously derivatized with o-phthaladehyde (OPA) in order to obtain a fluorophore, which participates in the PO reaction, producing a CL emission proportional to the gentamicin concentration. The method is developed by using a particular flow-injection analysis (FIA) manifold, employing sodium dodecyl sulfate (SDS) micellar medium as a carrier in order to avoid the degradation of PO in water. The optimization of the instrumental and chemical variables affecting the CL reaction was rigorously carried out by using experimental design methodology. The method has been successfully applied to pharmaceutical formulations.

Simultaneous determination of quercetin, kaempferol, and isorhamnetin in phytopharma-ceuticals ofHippophae rhamnoides L. by high-performance liquid chromatography with chemiluminescence detection

A novel method based on reversed-phase high-performance liquid chromatography with chemiluminescence detection has been developed for the simultaneous determination of three flavonols including quercetin, kaempferol, and isorhamnetin. The procedure was based on the chemiluminescent enhancement by flavonols of the cerium(IV)-rhodamine 6G system in sulfuric acid medium. The effects of several parameters on the HPLC resolution and CL emission were studied systematically. Good separation was achieved with isocratic elution using a mixture of methanol and aqueous 1.0% acetic acid (37:63, v/v) within 25 min. Under optimized conditions, the linear working range covers 3 orders of magnitude with relative standard deviations below 4.5% for 11 replicate injected flavonol samples, and detection limits (S/N= 3) were 1.6 x 10(-8), 3.5 x 10(-9), and 6.5 x 10(-9) g mL(-1) for quercetin, kaempferol, and isorhamnetin, respectively. The chemiluminescence reaction was compatible with the mobile phase of high-performance liquid chromatography. The proposed method has been successfully applied to the determination of three active flavonols in phytopharmaceuticals of Hippophae rhamnoides L. After a simple extraction procedure, the repeatability and recovery were satisfactory.

Formation of Well-Aligned ZnGa2O4 Nanowires from Ga2O3/ZnO Core−Shell Nanowires via a Ga2O3/ZnGa2O4 Epitaxial Relationship

Formation of well-aligned and single-crystalline ZnGa(2)O(4) nanowires on sapphire (0001) substrates has been achieved via annealing of the Ga(2)O(3)/ZnO core-shell nanowires. Ga(2)O(3)/ZnO core-shell nanowires were prepared using a two-step method. The thickness of the original ZnO shell and the thermal budget of the annealing process play crucial roles for preparing single-crystalline ZnGa(2)O(4) nanowires. Structural analyses of the annealed nanowires reveal the existence of an epitaxial relationship between ZnGa(2)O(4) and Ga(2)O(3) phases during the solid-state reaction. A strong CL emission band centered at 360 nm and a small tail at 680 nm are obtained at room temperature from the single-crystalline ZnGa(2)O(4) nanowires.

Sensitive determination of captopril by time-resolved chemiluminescence using the stopped-flow analysis based on potassium permanganate oxidation

The chemiluminescent behaviour of captopril when reacted with a common oxidant, potassium permanganate in different acidic media is described, using the stopped-flow technique in a continuous-flow system. A 22 bit analogue-to-digital converter that acquires analogue signals at −10 and +10 V and allows the power supply to the peristaltic pump to be interrupted is used in the time-resolved chemiluminescence manifold to ensure rapid, efficient mixing of chemiluminescent reagent and sample immediately before reaching the detector; this results in high precision and detectability, particularly with fast, short-lived emissions. The optimum chemical conditions for the chemiluminescence emission were investigated. It was found that a weak CL emission was emitted during the oxidation of this drug with potassium permanganate in acidic solution. The effect of common emission enhancers such as formic acid, formaldehyde, glutaraldehyde, acetaldehyde, quinine, fluorescein, rhodamine B and rhodamine 6G was studied. The parameters selected were 4.0 mol L −1 sulphuric acid, 0.25 mmol L −1 permanganate and 0.75 mol L −1 formaldehyde. Four quantitative parameters adjustable via software settings, two of them typically kinetic parameters, such as rate of the light-development reaction and rate of the light-decay reaction, and the other conventional parameters, such as maximum emission intensity and total emission area, were used to obtain linear calibration graphs with each measurement parameter. The detection limits ranged from 0.011 to 0.026 μg mL −1 and R.S.D. values ( n = 10) of 1.21–3.93 at a 0.50 μg mL −1 and 2.01–3.41 at a 1.60 μg mL −1 concentration levels were obtained. The method was satisfactorily applied to the determination of captopril in pharmaceutical preparations.

Determination of Phenol by Preconcentration‐Direct Chemiluminescence in a FIA Assembly

The determination of phenol in water samples is proposed with the aid of a flow‐injection system. The analytical procedure is based on the direct chemiluminometric emission by oxidation of the analyte with potassium permanganate in acidic medium. The flow assembly is provided with a solid‐phase reactor filled with a resin type XAD‐4 for analyte preconcentration. A large study of potential interferences, namely, amino acids reaching water through degradation of organic matter; metals and inorganic metal ions typically present in water interfering with the CL emission of the parent compound, was performed. The calibration graph was linear over the phenol concentration range 1.0–20.0 ng mL−1; the LOD was 5.0 ng mL−1. Finally, the method was applied to the determination of phenol in waste‐ and groundwater.

A new strategy for the chemiluminescent screening analysis of total N-methylcarbamate content in water

A new procedure for the screening of total N-methylcarbamate (NMCs) content in water at different concentration levels is here presented. It is based on a previous off-line alkaline hydrolysis of the NMCs, for the production of methylamine (MA), and its subsequent derivatisation with o-phthalaldehyde (OPA). After that, the obtained derivative is involved in the peroxyoxalate chemiluminescent (PO-CL) reaction using imidazole as a catalyst being the CL emission proportional to the total NMC content. The chemiluminescent reaction is carried out in a flow injection analysis (FIA) manifold, employing sodium dodecyl sulphate micellar medium as carrier, which avoids the rapid degradation of POs in water solution. The applicability of the screening method is shown for the monitoring of NMCs in natural waters. Analytical features, as specification limit signal, screening uncertainty, sensitivity and specificity, are calculated.

Animal tissue-based chemiluminescence sensing of uric acid

A new flow injection analysis method based on animal tissue as recognition element for chemiluminescence sensing of uric acid is proposed in this paper. The liver of the large white pig was used as molecular recognition element. Uric acid is oxidized by oxygen under the catalysis of urate oxidase in the tissue column to produce hydrogen peroxide, which can react with luminol in the presence of potassium hexacyanoferrate(III) to generate a CL signal. The experimental results show that the CL emission intensity was linear with uric acid concentration in the range of 0.001–3 μg mL −1 and the detection limit (3 σ) for uric acid was 4 × 10 −4 μg mL −1. The biosensor detection system could be used continuously for 4 h with less than 10% decrease in the response. More than 200 measurements were carried out during this time. A complete analysis, including sampling and washing, could be performed in 1 min with a relative standard deviation of 4.47% for 1 μg mL −1 uric acid. The biosensor detection system has been applied successfully to the analysis of uric acid in plasma and urine samples.

Development of a sensitive flow injection-chemiluminescence detection method for the indirect determination of propranolol

A highly sensitive flow injection-chemiluminescence detection (FI-CL) method based on pyrogallol (Pg) chemiluminescent reagent (CL-reagent) oxidized by periodate for the determination of propranolol is presented. The presented method is an indirect CL detection method based on the CL emission generated during the oxidation of Pg with the excess of periodate that remains after oxidation of propranolol within the time period of 10 min. The obtained propranolol calibration curve is linear up to 1.0 mg l −1 with a sensitivity of −0.95 V mg −1 l. At higher than 1.0 mg l −1 propranolol concentrations the propranolol calibration curve is still linear up to 20.0 mg l −1 with a sensitivity of −0.05 V mg −1 l. The detection limit is restricted from the noise level and at S/N = 3 was found to be 37.4 μg l −1 (3.74 ng) with R.S.D.% = 0.34 for seven replicate measurements.

Cathodoluminescent characteristics of Sm‐doped ZnAl2O4 nanostructured powders

AbstractCathodoluminescent (CL) powders of zinc aluminate activated with samarium ions have been prepared by a co‐precipitation chemical process. Different doping concentrations in the start mixture and sintering temperatures for the precipitated powder were studied. It was observed that the crystalline characteristics of the powders depend upon the sintering temperature. For temperatures higher than 450 °C, the powders presented the cubic spinel phase with a lattice parameter value of 8.0756 Å, and grain sizes from 50 to 100 nm with semispherical shape. The CL emission spectra showed broad bands localized at 564, 602, 644, and 703 nm associated with 4G5/2 → 6H5/2, 4G5/2 → 6H7/2, 4G5/2 → 6H9/2, and 4G5/2 → 6H11/2 transitions in the Sm3+ ions, respectively. Concentration quenching of the cathodoluminescence occurred at about 4.26 at% of the activator (Sm) concentration inside the sintered powders. (© 2005 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Chemiluminescence biosensor system for lactic acid using natural animal tissue as recognition element

A new method based on natural animal tissue porcine kidney as recognition element for chemiluminescence sensing of lactic acid is proposed in this paper. The principle for lactic acid sensing is that lactic acid is oxidized by oxygen under the catalysis of alpha-hydroxy acid oxidase in the tissue column to produce hydrogen peroxide, which can react with luminol in the presence of potassium ferricyanide to generate a CL signal. The experimental results show that the CL emission intensity was linear with lactic acid concentration in the range of 1-1000 micromol/L and the detection limit (3sigma) for lactic acid was 0.2 micromol/L. The biosensor could be used continuously for 6h with no significant changes in the response. More than 240 measurements were carried out during this time. A complete analysis, including sampling and washing, could be performed in 1.5 min with a relative standard deviation of 1.12% for 100 micromol/L lactic acid. The reproducibility among tissue columns was satisfactory (RSD among columns is less than 5%). The biosensor has been applied successfully to the analysis of lactic acid in plasma and milk samples.

Etching properties of ZnS thin films in Cl 2/CF 4/Ar plasma

The manganese-doped zinc sulfide (ZnS:Mn) films were investigated in terms of etch rates and selectivity with inductively coupled plasma (ICP). The changes of volume density of etching species in Cl 2/CF 4/Ar plasma were investigated with optical emission spectroscopy (OES). OES analysis indicated that the maximum Cl emission intensity was obtained with the gas mixture of 10% addition to CF 4(20%)/Ar(80%) plasma. The changes of chemical states on the surface were analyzed with X-ray photoelectron spectroscopy (XPS). XPS study indicated that Zn was formed non-volatile etch by products and remained on the surface after etching of ZnS:Mn (0.39 wt.%) in Cl 2/CF 4/Ar plasma. The etch rate of ZnS was gradually increased up to 10% addition of Cl 2 then decreased furthermore with increasing Cl 2 contents from 20 to 30%. The increase of etch rate can be explained by the effect of chemical and physical etching process.

GaN etch enhancement in inductively coupled BCl3 plasma with the addition of N2 and SF6 gas

Etching of GaN using BCl3/N2, BCl3/SF6 and BCl3 by inductively coupled plasma (ICP) was performed and the effects of N2 and SF6 were examined using optical emission spectroscopy. With the addition of 40% N2 and 20% SF6 to BCl3, the etch rate of GaN was increased from 600 to 2800 and 2000 Å min−1 at 700 W ICP power, respectively. There was a clear relationship between the increase of GaN etch rate and reactive Cl with the addition of N2 and SF6 gas to BCl3. In addition, B emission intensity was increased also with Cl emission intensity and negligible BN emission was observed. This means that N2 and SF6 reduce the recombination probability of B and reactive Cl and result in higher concentration of reactive Cl and higher etch rate with the addition N2 and SF6 to BCl3 plasma.

Trace elements in quartz - a combined electron microprobe, secondary ion mass spectrometry, laser-ablation ICP-MS, and cathodoluminescence study

We present electron microprobe, secondary ion mass spectrometry, and laser ablation inductively coupled mass spectrometry data for common trace elements (Li, Al, Ti, Na, K, Fe) in quartz. Our samples from both magmatic and hydrothermal environments all show heterogeneity at the single grain scale. ConcentrationsofAlandTi determinedbyEPMA,SIMS,andLA-ICP-MSareinroughagreementandconfirmtherobustnessof these analytical methods. The highest precision data were obtained from SIMS, but this is outweighed by the lack of a high quality quartz reference sample for calibrating this technique. Due to its large sampling volume, laser ablation analyses gave only average values for trace elements in zoned quartz. Because of its better spatial resolution in conjunction with the ability to combine spot analyseswithcathodoluminescenceimaging EPMAprovedthemost reliable insitu methodfor obtainingquantitativetraceelement dataofquartzatconcentrationsinexcessof afew10' sofppmandatthe<10µ mscale.However,oursamplecontainedfewelements at such high concentration levels. We found in our samples a positive correlation between CL signature and the observed Ti contents for the samples investigated. In particular, blue luminescing zones were found to have elevated Ti concentrations as compared to other nearby domains. Using a mathematical spectral deconvolution weshow thehighlycomplex natureof CL emission- it appearsthat other trace elementmight play a less pronounced role in this process. Our examples demonstrate the value of CL for documenting multi-phase alteration in quartz. In agreement with previously proposed models, we confirm a significant correlation between mono- and tri-valent cation concentrations in quartz. A very strong correlation in alkali metal contents is particularly obvious. Ti was found to be universally present in magmatic quartz, but at much lower abundance in hydrothermal quartz.

Flow Injection Chemiluminescence Method for Determination of Ribavirin Based on Enhancement of Luminol-Persulfate Reaction

A novel flow injection chemiluminescence (FI-CL) method for the determination of ribavirin is developed based on the enhancing effect of the analyte on CL emission of luminol oxidized by sodium persulfate in alkaline solution. The CL emission is correlated with the ribavirin concentration in the range from 0.01 to 1.0 µg mL−1, and the detection limit (3σ) is 0.004 µg mL−1. The relative standard deviation is 2.8% (n = 11, 0.1 µg mL−1 ribavirin). The method was successfully applied to the determination of ribavirin in pharmaceutical preparations.