Bioluminescence and Chemiluminescence: Current Articles
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On this page considered biochemistry journals:
Journal of Bioluminescence and Chemiluminescence - published by
Wiley Interscience -
Current research articles of the mentioned
journals:
Application of a lanthanide composite nanoparticle-sensitized luminescence method for the determination of salicylic acid in pharmaceutical formulations and human plasma
Terbium-acetylacetone (Tb-acac) composite nanoparticles were synthesized using the ultrasonic method. The nanoparticles are water-soluble, stable and have extremely narrow emission bands and high internal quantum efficiencies. They were used as fluorimetric probes in the determination of salicylic acid (SA), based on the fluorescence enhancement of nanoparticles through fluorescence resonance energy transfer (FRET). The influence of buffer solution was investigated. Under the optimum conditions, a linear calibration graph was obtained over the SA concentration range 5 × 10-7-1 × 10-4 mol/L. The limit of detection was found to be 2.5 × 10-8 mol/L. The relative standard deviation (RSD) for six repeated measurements of 1 × 10-4 mol/LSA was 1.75%. The method was applied to the determination of SA in pharmaceutical formulations and human plasma. We believe that the proposed approach has great potential for clinical purposes. Copyright © 2008 John Wiley & Sons, Ltd.
Study on the interaction between nitroxide free radical and conjugated polyelectrolytes by fluorimetry
In this work, we studied the fluorescence quenching of the anionic conjugated polyelectrolyte PPE-SO3 by the paramagnetic species 2,2,6,6-tetramethylpiperidine-N-oxide free radical (TEMPO) in aqueous solution. At low quencher concentration the Stern-Volmer constant is 94 mol/L; as the quencher concentration increases the Stern-Volmer plots become superlinear. Ascorbic acid is used to reduce TEMPO to the corresponding hydroxylamine and the PPE-SO3 fluorescence is fully recovered. Under a large excess of ascorbic acid over TEMPO, the rise of fluorescence followed pseudo-first-order kinetics. The second-order rate constant calculated from this time course is 0.7 mol/L/s. Copyright © 2008 John Wiley & Sons, Ltd.
A critical evaluation of a flow-cell based on a liquid core waveguide for chemiluminescence measurements
Liquid-core waveguides (LCWs), devices that constrain the emitted radiation minimizing losses during the transport, are an alternative to maximize the amount of detected radiation in luminescence. In this work, the performance of a LCW flow-cell was critically evaluated for chemiluminescence measurements, by using as model the oxidation of luminol by hydrogen peroxide or hypochlorite. An analytical procedure for hypochlorite determination was also developed, with linear response in the range 0.2-3.8 mg/L (2.7-51 µmol/L), a detection limit estimated as 8 µg/L (0.64 µmol/L) at the 99.7% confidence level and luminol consumption of 50 µg/determination. The coefficients of variation were 3.3% and 1.6% for 0.4 and 1.9 mg/L ClO-, respectively, with a sampling rate of 164 determinations/h. The procedure was applied to the analysis of Dakin's solution samples, yielding results in agreement with those obtained by iodometric titration at the 95% confidence level. Copyright © 2008 John Wiley & Sons, Ltd.
Luminescent properties of a novel fluorene organic material
The photo-physical properties of 6,6[prime]-(9H-fluoren-9,9-diyl)bis(2,3-bis(9,9-dihexyl-9H-fluoren-2-yl)quinoxaline) (BFLBBFLYQ) and its blend doped with N[prime]-biphenyl-N,N[prime]-bis-(3-methylphenyl)-1,1[prime]-biphenyl-4,4[prime]-diamine (TPD) were investigated. The absorption, photoluminescence (PL) and electroluminescence (EL) properties of pristine BFLBBFLYQ and blend in solution and spin-coated film are outlined, including a discussion of charge-transfer (CT) exciplex emission of BFLBBFLYQ:TPD blend in the solid state. The luminescent properties of BFLBBFLYQ films using different deposition processes were studied. It was found that the low-energy emission bands at 530-570 nm appeared in the PL spectra of BFLBBFLYQ evaporated films in ultra-high vacuum. Also, the low-energy band was the exclusive emission in the EL spectra of BFLBBFLYQ films. Copyright © 2008 John Wiley & Sons, Ltd.
Highly sensitive spectrofluorimetric determination of trace amounts of prulifloxacin using the aluminium(III)-prulifloxacin system
The fluorescence of the prulifloxacin (PUFX)-Al(III) system was investigated . Experiments indicated that the fluorescence intensity of prulifloxacin could be greatly enhanced by Al(III) and sensitized by sodium dodecylbenzene sulphonate (SDBS). Accordingly, a sensitive spectrofluorimetric method for the determination of prulifloxacin was established. While excited at 275 nm, the enhanced fluorescence intensity at 412 nm of the system ([Delta]F) showed a good linear relationship with the concentration of prulifloxacin within the range 4.0 × 10-8-3.0 × 10-6 mol/L. The regression equation was [Delta]F = 9.83 + 10.8 × 107c (mol/L); the correlation coefficient and detection limit (3[sigma]/k) were 0.99901 and 2.0 × 10-8 mol/L, respectively. The proposed method has been successfully applied to determine prulifloxacin in real pharmaceutical samples. The luminescence mechanism of the system is also discussed in detail. Copyright © 2008 John Wiley & Sons, Ltd.
Resonance light scattering study on the interaction of benproperine phosphate with eriochrome blue black R in the presence of sodium dodecylbenzene sulphonate and its analytical application
The interaction of benproperine phosphate (BPP) with eriochrome blue black R (EBBR) in the presence of sodium dodecylbenzene sulphonate (SDBS) was studied using resonance light scattering (RLS) technology and ultraviolet-visual (UV-vis) spectrophotometry. Under optimum conditions, BPP reacts with EBBP and SDBS to form a three-component complex, which results in strong RLS signal and a new RLS peak. The enhanced RLS intensities are proportional to the concentration of BPP over the range 0.6-28.0 µg/mL, with a detection limit of 0.053 µg/mL. The affecting factors as well as the influence of coexisting substances were investigated. The results indicate that this assay method could be applied to the determination of BPP in pharmaceuticals, serum and urine samples with satisfactory results. Copyright © 2008 John Wiley & Sons, Ltd.
Development of a novel capillary electrophoresis chemiluminescence system for amino acid analysis
In the present study, a novel peroxyoxalate CE-CL system was developed to achieve high signal stability and sensitivity based on a design of a new interface including a new mixing mode and a new grounding electrode mode. Amino acids fluorescently tagged with dansyl chloride and naphthalene-2,3-dicarboxaldehyde(NDA) were used for the study. Experiment results show this new system is quite effective to separate and detect amine acid with high stability and resolute. The detection limits were 1.1 nmol/L for dansyl-leucine (Leu) and 2.0 nmol/L for dansyl-aspartic acid (Asp). The relative standard deviations of peak height and migration time were in the ranges of 2.3-3.8% and 1.2-1.5%, respectively. Copyright © 2008 John Wiley & Sons, Ltd.
Disorganization of the Mn4Ca complex of photosystem II by ruthenium red: a thermoluminescence study
Ruthenium red (RR) is known to be an inhibitor that binds to Ca2+ sites. It releases Ca2+ and Cl- together with the extrinsic polypeptide of 17 kDa associated with the oxygen evolving complex of photosystem II. In this work we used thermoluminescence to study S2/3QB- and S2QA- charge recombination. It is shown that RR produced a deeper inhibition of oxygen evolution compared with the effect of extrinsic polypeptide or Ca2+/Cl- depletion. Even though Mn is not released, the Mn cluster is disorganized by RR and the S1 [rarr] S2 transition is inhibited. Copyright © 2008 John Wiley & Sons, Ltd.
Fluorescence quenching and bonding properties of some hydroxamic acid derivatives by iron(III) and manganese(II)
Spectrophotometric investigations of highly fluorescent metal chelating molecules are of relevance due to their potential application in novel, selective fluorescence-based sensors. Benzene and naphthalene chromophores are highly fluorescent while hydroxamic acids are widely used as ligands for complexation of transition metals. In order to develop fluorescence probes, several phenyl derivatives of N-phenylbenzohydroxamic acid and an aminodihydroxamic acid linked with a naphthalene chromophore were synthesized and their selective ionophoric properties towards iron(III) and manganese(II) ions were investigated using fluorescence and absorption spectroscopy. Both methods confirm the formation of 1:1 and 1:2 complexes for iron(III) and a 1:1 complex for manganese(II). The complex that is formed depends on the concentration of the ligand and pH of the medium. The amino dihydroxamic acid exhibits a prominent selectivity towards iron(III) with a two-step 1:1 and 1:2 quenching mechanism at pH 3 and towards manganese(II) with a 1:1 quenching mechanism at a probe concentration of 1 × 10-5 mol dm-3 at pH 9.5 The logarithm of overall formation constants of 1:1 and 1:2 complexes of iron(III) were estimated as 3.30 and 9.05, respectively. Copyright © 2008 John Wiley & Sons, Ltd.
Study on the interaction between palladium(II)-lincomycin chelate and erythosine by absorption, fluorescence and resonance Rayleigh scattering spectra and its analytical applications
In pH 5.0-5.4 HAc-NaAc buffer solution, lincomycin (Linco) reacted with Pd(II) to form 1:1 cationic chelate, which could further react with erythrosine (Ery) to form 1:1 ion-association complexes (Pd-Linco)Ery. As a result, not only were the absorption and fluorescence spectra changed, but also the resonance Rayleigh scattering (RRS) intensity was greatly enhanced. These phenomena offered useful means for the determination of Linco by spectrophotometry, fluorescence and RRS methods. The linear range and detection limit of Linco were 0.20-3.00 µg/mL and 0.057 µg/mL, 0.20-4.80 µg/mL and 0.061 µg/mL, 0.05-2.70 µg/mL and 0.015 µg/mL for the spectrophotometric, fluorescence quenching and RRS methods, respectively. Among these, the RRS method obtained the highest sensitivity. Therefore, the optimum reaction conditions and the influences of coexisting substances were investigated using the RRS method. A simple, sensitive and rapid method has been developed for the determination of Linco in either the pharmaceutical form or human body fluids, and the reasons for RRS enhancement are discussed. Copyright © 2008 John Wiley & Sons, Ltd.
A novel biosensor for bovine serum albumin based on fluorescent self-assembled sandwich bilayers
Fluorescent dyes butyl rhodamine B were assembled via a dl-cystenine intermediate onto quartz wafers whose surface had first adsorbed gold nanoparticles. Hence self-assembled sandwich bilayers with nanocomposite structure were constructed which can be used as a biosensor for bovine serum albumin. The biosensor-based self-assembled monolayers (SAMs) are regenerable and have high sensitivity, five orders of magnitude higher than that of bulk solution phase sensing. The effects of existing forms of dyes on the fluorescence spectra of bilayers in the presence of bovine serum albumin were investigated. Copyright © 2008 John Wiley & Sons, Ltd.
Humic acid-cetyltrimethylammonium bromide interaction: a fluorimetric study
Synchronous and excitation emission matrix fluorescence (EEMF) characteristics of humic acid-surfactant interaction have been studied. The variation of synchronous and EEMF spectral maxima and intensities with humic acid (HA)-cetyltrimethylammonium bromide (CTAB) composition sensitively reflects the extent of flocculation of HA. It was found that the concentration range for co-precipitation of HA-CTAB was similar for all concentrations (60 p.p.m., 80 p.p.m. and 100 p.p.m.) of humic acid studied. In the concentration range 60-150 p.p.m. of humic acid, the EEMF maximum is found at 460/540 nm, indicating the presence of ligneous materials. Fluorescence intensity measurement at this contour excitation/emission wavelength (460/540 nm) is suggested as a convenient and a sensitive method for studying the physical state of humic acid in the presence of cationic surfactants. No significant interaction of HA with sodium dodecylsulphate (SDS) and TX-100 was found. Copyright © 2008 John Wiley & Sons, Ltd.
Selectivity and potential interference from phenolic compounds in chemiluminescence methods for the determination of synephrine
Three recently reported chemiluminescence methods (based on reactions with alkaline luminol and hexacyanoferrate(III); acidic cerium(IV) and rhodamine B; and acidic permanganate with polyphosphates) for the determination of synephrine were re-evaluated in terms of their selectivity towards this analyte in comparison to other phenolic compounds. A fourth reagent system, acidic soluble manganese(IV) and formaldehyde, was also examined. Each set of reagents was sensitive towards synephrine (limits of detection were 3 × 10-9, 5 × 10-8, 1 × 10-8 and 1 × 10-8 mol/L, respectively) but also responded with numerous other phenolic compounds, including some that are present in citrus fruit extracts, dietary supplements and/or biological fluids. It is therefore recommended that the determination of synephrine in these matrices should incorporate physical separation of sample components (e.g. chromatography or electrophoresis). In more general terms, this study illustrates that accurate percentage recoveries for an analyte in spiked samples (without validation against another analytical method) are insufficient to confirm the analytical utility of new flow-injection analysis (FIA) procedures. Copyright © 2008 John Wiley & Sons, Ltd.
Hydroxyl and superoxide radical scavenging abilities of chromonyl-thiazolidine-2,4-dione compounds
The oxygen free radical scavenging activities of 15 chromonyl-thiazolidine-2,4-dione compounds (CTDs) were examined in chemical systems producing superoxide anion radicals, O-[bull]2 (potasium superoxide-18-crown-6 ether-DMSO), and hydroxyl radicals, HO[bull] (a Fenton reaction: Fe(II)-H2O2-sodium trifluoroacetate, pH 6.15). Chemiluminescence and electron spin resonance (ESR) spectroscopy using 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) as spin trap were applied to evaluate antioxidant behaviour of CTDs towards the oxygen radicals. The results indicated that 11 of the 15 tested compounds showed a significant inhibitory effect on the chemiluminescence generated from the O-[bull]2-generating system, ranging from 41 to 86%, and 13 CTDs quenched the ESR signal of the DMPO-OH spin adduct by 33-86%, at a concentration of 1 mmol L-1. Our findings demonstrate that CTDs could be good free radical scavengers. Copyright © 2008 John Wiley & Sons, Ltd.
Study of the enhancement of a new chemiluminescence reaction and its application to determination of [beta]-lactam antibiotics
An enhanced thiosemicarbazide(TSC)-H2O2 chemiluminescence (CL) system was established and proposed as a new analytical method for determination of [beta]-lactam antibiotics, ampicillin sodium and amoxicillin at microgram levels. The method is based on the inhibition of CL emission accompanying oxidation of TSC by H2O2 in alkaline medium. The effect of anionic, cationic, and non-ionic surfactants on the CL emission of the system was studied. Both N-cetyl-N,N,N-trimethylammonium bromide (CTMAB) and Triton X-100, unlike sodium dodecyl sulfate (SDS), reinforced the CL intensity and were efficient to approximately the same level. The effect of the presence of eight non-aqueous solvents on the CL system was also investigated. Upon addition of both of the non-ionic surfactant, Triton X-100, and the non-aqueous solvent, N,N-dimethyl formamide (DMF), the intensity of the CL reaction was increased 100-fold. This method allows the measurement of 25-545 µg amoxicillin, and 35-350 µg ampicillin sodium. The detection limits are 8 µg for amoxicillin and 9 µg for ampicillin sodium. The relative standard deviations of six replicate measurements of 200 µg amoxicillin and 200 µg ampicillin sodium were 1.9 and 2.1%, respectively. The effect of foreign species on the determination of amoxicillin and ampicillin sodium was also examined. The proposed method was successfully applied to the determination of ampicillin sodium and amoxicillin in some pharmaceutical dosage forms. Copyright © 2008 John Wiley & Sons, Ltd.
1,10-Phenanthroline-H2O2-KSCN-CuSO4-NaOH oscillating chemiluminescence system
In this paper, oscillating chemiluminescence (CL), 1,10-phenanthroline H2O2-KSCN-CuSO4-NaOH system, was studied in a batch reactor. The system described is a novel, slowly damped oscillating CL system, generated by coupling the well-known Epstein-Orban, H2O2-KSCN-CuSO4-NaOH chemical oscillator reaction with the CL reaction involving the oxidation of 1,10-phenanthroline by hydrogen peroxide, catalyzed by copper(II) in alkaline medium. In this system, the CL reaction acts as a detector or indicator system of the far-from-equilibrium dynamic system. Narrow and slightly asymmetric light pulses of 1.2 s half-width are emitted at 440 nm with an emitted light time of 200-1000 s, induction period of 3.5-357 s and oscillation period of 28-304 s depending on the reagent concentrations. In this report the effect of the concentration variation of components involved in the oscillating CL system on the induction period, the oscillation period and amplitude was investigated and the parameters were plotted with respect to reagent concentrations. Copper concentration showed a significant effect on the oscillation period. The possible mechanism for the oscillating CL reaction was also discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Determination of propafenone hydrochloride by flow-injection analysis coupled with resonance light scattering detection
A simple, sensitive and rapid flow injection analysis (FIA) method with resonance light scattering (RLS) was described for the determination of propafenone (PPF). The method was based on the ion-association reaction of 12-tungstophosphoric acid (TP) with propafenone. In pH 1.0 acidic medium, TP reacted with PPF to form an ion-associate complex, which resulted in a significant enhancement of RLS intensity. The maximum scattering peak was located at 340 nm, the RLS intensity was proportional to the concentration of PPF in the range 0.003-9.0 µg/mL, and the detection limit (3[sigma]) of 1.0 ng/mL was obtained at a sampling rate of 60 samples/h. The feasible reaction conditions and FIA parameters for the system were optimized. The method proposed in this paper shows satisfactory reproducibility with a relative standard deviation (RSD) of 2.1% for 10 successive determinations of 2.0 µg/mL PPF. The present method had been successfully applied to the determination of PPF in serum samples and pharmaceutical samples. The results obtained were in agreement with the method used in the Chinese Pharmacopoeia. Copyright © 2008 John Wiley & Sons, Ltd.
Chemiluminescence determination of chlorpheniramine using tris(1,10-phenanthroline)-ruthenium(II) peroxydisulphate system and sequential injection analysis
A sequential injection (SI) method was developed for the determination of chlorpheniramine (CPA), based on the reaction of this drug with tris(1,10-phenanthroline)-ruthenium(II) [Ru(phen)32+] and peroxydisulphate (S2O82-) in the presence of light. The instrumental set-up utilized a syringe pump and a multiposition valve to aspirate the reagents [Ru(phen)32+ and S2O82-] and a peristaltic pump to propel the sample. The experimental conditions affecting the chemiluminescence reaction were systematically optimized, using the univariate approach. Under the optimum conditions linear calibration curves of 0.1-10 µg/ml were obtained. The detection limit was 0.04 µg/ml and the relative standard deviation (RSD) was always < 5%. The procedure was applied to the analysis of CPA in pharmaceutical products and was found to be free from interferences from concomitants usually present in these preparations. Copyright © 2008 John Wiley & Sons, Ltd.
Spectrofluorimetric determination of vitamin B1 using horseradish peroxidase as catalyst in the presence of hydrogen peroxide
In this work a new spectrofluorimetric method for the determination of vitamin B1, based on the catalytic activity of horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H2O2), has been developed. Non-fluorescent vitamin B1 was easily converted through catalytic oxidation in alkaline medium into a fluorescent compound, even without exposure to light. The linear range for vitamin B1 observed was 0.026-16.83 µg/mL (RSD = 1.75%). The correlation coefficient for the calibration curve and limit of detection were found to be 0.9964 and 0.015 µg/mL, respectively. The developed method is practical, simple, sensitive and relatively free from interference by coexisting substances and has been successfully applied for the determination of vitamin B1 in pharmaceutical preparations. Copyright © 2008 John Wiley & Sons, Ltd.
Luminescent and hydrophilic LaF3-polymer nanocomposite for DNA detection
Luminescent LaF3-Ce3+/Tb3+ nanocrystals have been successfully prepared via a simple wet chemical technique. For the next bioapplication, these nanoparticles dispersed in cyclohexane have also been functionalized with poly(St-co-MAA), based on a designed oil-in-water microemulsion system. These polymer-coated nanospheres are water-soluble and bioconjugable. Unlike semiconductor quantum dots, the as-prepared lanthanum fluoride nanocrystals possess non-size-dependent emissions and completely stable photocycles. With functionalized LaF3 nanospheres as fluorescence probes, a fluorescence method was developed for the rapid quantitative analysis of DNA, due to the quenching effect of fluorescence by the DNA. Under optimum conditions, the fluorescence intensity was proportional to the concentration of the introduced DNA over the range 2.5-35 µg/mL for calf thymus DNA (ctDNA) and 2.5-30 µg/mL for fish sperm DNA (fsDNA), respectively. Copyright © 2008 John Wiley & Sons, Ltd.
Extended-release PEG-luciferin allows for long-term imaging of firefly luciferase activity in vivo
Bioluminescence has gained favour in the last decade as an approach for observing tumours in vivo in a non-destructive manner. This very sensitive technique is based on light emission by the reaction of luciferin with the enzyme luciferase, as measured by a photodetector. Ever since the development of recombinant tumour cell lines that have been engineered to produce luciferase, a vast number of experiments have been carried out examining tumour growth, tumour metastasis and the effect of therapeutic regimens in such cases. A primary stumbling block, however, is the relatively short circulatory half-life of luciferin. In this paper, we propose the PEGylation of 6-amino-d-luciferin to extend its in vivo circulatory half-life, thus making the possibility of long-term observations in animals possible. The covalent attachment was through a carbamate linker that is known to hydrolyse in vivo, releasing the parent compound. Based on our studies, longer emission of the PEGylated luciferin was observed, as compared to free luciferin in mice bearing PC3 prostate tumours expressing luciferase. This result suggests that this reagent can be used in applications requiring extended monitoring of luciferase activation in vivo. Copyright © 2008 John Wiley & Sons, Ltd.
Development of a chemiluminescent imaging assay for the detection of anti-erythropoietin antibody in human sera
Measuring low amounts of anti-erythropoietin antibodies (anti-EPO Abs) is important to evaluate the therapeutic safety of recombinant human erythropoietin (rhEPO). In this work, a simple, sensitive and high-throughput chemiluminescent (CL) imaging assay was developed for the detection of anti-EPO Abs in human sera. The influence of several physicochemical parameters, such as coating conditions, incubation time, detergent concentration and exposure time, were investigated. A calibration curve was established and the range of quantitative detection was 0.12-13.91 ng/mL. The limit of detection (LOD, 3[sigma]) for the CL-imaging assay was 0.033 ng/mL. Compared to conventional colorimetric enzyme-linked immunosorbent assay (ELISA), the LOD of the CL-imaging assay is 50-fold lower. The recoveries of anti-EPO Abs in the fortified serum were in the range 87.1-116.9% using the present method, which highlighted the validity of the CL-imaging assay system to accurately determine the anti-EPO Abs in serum samples. CL-imaging assay was used to evaluate the presence of anti-EPO Abs in serum samples obtained from chronic renal failure (CRF) patients treated with rhEPO. Contrary to what was expected, the sera from CRF patients did not contain anti-EPO Abs. Copyright © 2008 John Wiley & Sons, Ltd.
Determination of trace [alpha]-fetoprotein variant by affinity adsorption solid substrate-room temperature phosphorimetry
The 3.5-generation dendrimers (3.5G-D)-porphyrin (P) dual luminescent molecule (3.5G-D-P) was used to label concanavalin agglutinin (Con A); the product of the reaction is 3.5G-D-P-Con A. A new method for the determination of trace AFP-V by affinity adsorption solid substrate-room temperature phosphorimetry (AA-SS-RTP) was established, based on the room temperature phosphorescence (RTP) property of the product on polyamide membrane (PAM) substrate and the specific affinity adsorption (AA) reaction between 3.5G-D-P-Con A and [alpha]-fetoprotein variant (AFP-V), which caused the RTP of the system to be sharply enhanced, the [Delta]Ip was linearly correlated to the content of AFP-V. The sensitivity of the method was obviously high. It could accurately detect the content of AFP-V in serum. The results were tallied well with those obtained by the ELISA method. Copyright © 2008 John Wiley & Sons, Ltd.
Rapid chemiluminometric determination of gabapentin in pharmaceutical formulations exploiting pulsed-flow analysis
In this study, a straightforward and automated pulsed flow-based procedure was developed for the chemiluminometric determination of gabapentin [1-(aminomethyl)cyclo-hexaneacetic acid], a new generation antiepileptic drug, in different formulated dosage forms. The software-controlled time-based injection method capitalizes on the decrease of the background chemiluminescence (CL) readout of the luminol-hypochlorite reaction in the presence of gabapentin. In short, gabapentin works as a hypochlorite scavenger. The analytical procedure was implemented in a multi-pumping flow network furnished with a suite of microdispensing solenoid-actuated pumps. The diaphragm-type micropumps might be configured to operate as fluid propellers, commutation units and metering injectors. A dynamic linear working range for gabapentin concentrations in the range 60-350 µmol/L was obtained, with an estimated detection limit of 40 µmol/L. The flow analyser handles about 41 injections/h and yields precise results (RSD < 2%). The miniaturized flow analyser thus has potential to be exploited for in-line monitoring of drug manufacturing within the quality assurance framework of modern pharmaceutical companies. Copyright © 2008 John Wiley & Sons, Ltd.
Luminescent sensor for Cd2+, Hg2+ and Ag+ in water based on a sulphur-containing receptor: quantitative binding-softness relationship
A water-soluble, high-output fluorescent sensor, based on a lumazine ligand with a thiophene substituent for Cd2+, Hg2+ and Ag+ metal ions, is reported. The sensor displays fluorescence enhancement upon Cd2+ binding (log [beta] = 2.79 ± 0.08) and fluorescence quenching by chelating with Ag+ and Hg2+ (log [beta] = 4.31 ± 0.15 and 5.42 ± 0.1, respectively). The mechanism of quenching is static and occurs by formation of a ground-state non-fluorescent complex followed by rapid intersystem crossing. The value of the Stern-Volmer quenching rate constant (kq) by Ag+ ions is close to 6.71 × 1012 mol/L/s at 298 K. The thermodynamic parameters ([Delta]G, [Delta]H and [Delta]S) were also evaluated and indicated that the complexation process is spontaneous, exothermic and entropically favourable. The quantitative linear relationship between the softness values of Klopman ([sigma]K) or Ahrland ([sigma]A) and the experimental binding constants ([beta]) being in the order of Hg2+ > Ag+ > Cd2+ suggests that soft-soft interactions are the key for the observed sensitivity and selectivity in the presence of other metal ions, such as: Pb2+, Ni2+, Mn2+, Cu2+, Co2+, Zn2+ and Mg2+ ions. Copyright © 2008 John Wiley & Sons, Ltd.
Luminescence experiments involved in the mechanism of streptozotocin diabetes and cataract formation
Streptozotocin (STZ)-induced diabetes is linked to excessive nitric oxide (NO), and possibly peroxynitrite (OONO-) and/or other nitrogen oxides, e.g. nitrogen trioxide (N2O3), which damages DNA of pancreatic [beta] cells, causing death and loss of insulin. Simultaneous injection of carboxy-PTIO (CPTIO) and STZ prevents diabetes and cataract formation in rats, whereas 4-hydroxy-Tempo (4HT) does not. CPTIO oxidizes nitric oxide to nitrite, which prevents production of the diabetogenic toxin. Peroxynitrite may not be involved, since 4HT (converts O2- to H2O2) injected with STZ produces diabetes. All six of the control rats injected with STZ became diabetic and developed cataracts after 3 months. Eight rats injected with STZ and CPTIO were non-diabetic with no cataracts up to a year. This work establishes the idea that excessive nitric oxide is a primary initiator in STZ diabetes. Luminescence experiments using OONO- generation from SIN-1 with L-012 indicates that 4HT is an effective inhibitor, while CPTIO is ineffective. Experiments with dilute solutions of nitrogen trioxide added to ladder or plasmid DNA reveal extensive nicking of DNA, thereby raising the possibility that other oxides of nitrogen could be involved with the damage to DNA. It can be concluded that diabetes can be prevented by oxidizing excessive NO from STZ. Copyright © 2008 John Wiley & Sons, Ltd.
Development of a benzaldehyde sensor utilizing chemiluminescence on nanosized Y2O3
A chemiluminescence sensor has been proposed for sensitive determination of benzaldehyde, with nanosized Y2O3 as the sensing material. Under optimized conditions, the linear range of the CL intensity vs. the concentration of benzaldehyde vapour is 1.8 ng/mL-10.8 µg/mL (r2 = 0.9996), with a detection limit of 0.90 ng/mL (signal:noise ratio = 3:1). The sensor also exhibits high selectivity to benzaldehyde because no or weak CL signals have been detected when foreign substances are introduced into the sensor. In addition, the sensor also shows good stability and longer lifetime within 100 h. The results indicate that the proposed sensor, which has high sensitivity and selectivity, shows great potential for the detection of benzaldehyde. Copyright © 2008 John Wiley & Sons, Ltd.
Ground- and excited-state proton transfer and antioxidant activity of 3-hydroxyflavone in egg yolk phosphatidylcholine liposomes: absorption and fluorescence spectroscopic studies
Excited-state intramolecular proton transfer (ESIPT) and dual luminescence behaviour of 3-hydroxyflavone (3-HF) have been utilized to monitor its binding to liposomal membranes prepared from egg yolk phosphatydilcholine (EYPC). Additionally, absorption spectrophotometric assay has been performed to evaluate the antioxidant activity of 3-HF against lipid peroxidation in this membrane system. When 3-HF molecules are partitioned into EYPC liposomes, a weak long-wavelength absorption band with [lambda]absmax [sim]410 nm appears in addition to the principal absorption at [sim][lambda]absmax = 345 nm. Selective excitation of the 410 nm band produces the characteristic emission ([lambda]emmax[sim]460 nm) of the ground-state anionic species, whereas excitation at the higher energy absorption band leads to dual emission with predominatly ESIPT tautomer fluorescence ([lambda]emmax = 528 nm). Both ESIPT tautomer and the anionic species exhibit fairly high fluorescence anisotropy (r) values (r = 0.122 and 0.180, respectively). Biexponential fluorescence decay kinetics are observed for the ESIPT tautomer as well as the ground-state anionic forms, indicating heterogeneity in the microenvironments of the corresponding emitting species. Furthermore, we demonstrate that lipid peroxidation of EYPC liposomes is significantly inhibited upon 3-HF binding, suggesting that 3-HF can be potentially useful as an inhibitor of peroxidative damage of cell membranes. Copyright © 2008 John Wiley & Sons, Ltd.
Resonance light-scattering enhancement effect of the protein-Y3+-TTA-SLS system and its analytical application
In this paper, a sensitive resonance light scattering (RLS) method for the determination of protein is reported. In the Tris-HCl (pH 7.50) buffer, protein enhanced the RLS intensity of the Y3+-2-thenoyltrifluoroacetone (TTA)-sodium dodecyl sulphate (SLS) system. The enhanced RLS intensities were in proportion to the concentrations of proteins in the range 8.0 × 10-9-1.0 × 10-5 g/mL for BSA, 1.0 × 10-8-1.0 × 10-5 g/mL for HSA and 1.0 × 10-8-1.0 × 10-6 g/mL for EA, and their detection limits were 5.0, 5.4 and 6.7 ng/mL, respectively. Actual samples were satisfactorily determined. The interaction mechanism was also studied. Copyright © 2008 John Wiley & Sons, Ltd.
Preparation of aminated core-shell fluorescent nanoparticles and their application to the synchronous fluorescence determination of [gamma]-globulin
Amino-modified silica nanoparticles (FSNPs) doped with fluorescein isothiocyanate (FITC) were synthesized by using an aqueous core of reverse-micelle microemulsion as the nanoreactor in an easy one-pot method. Due to the FITC conjugating with (3-aminopropyl)triethoxysilane (APTS), the nanoparticles prevent the FITC from leaching from the silica matrix when immersed in aqueous solution. SEM, FTIR, fluorescence lifetime, a photobleaching experiment and synchronous fluorescence spectra were used to characterize the FSNPs. The synchronous fluorescence signal of FSNPs was enhanced when trace amounts of [gamma]-globulin ([gamma]-G) were added. Under the optimal experimental conditions, the enhanced fluorescence intensity ([Delta]F) was linear with the concentration of [gamma]-G (c) in the range 0.3-4.8 µg/mL, with a detection limit of 0.04 µg/mL. The proposed method is simple, sensitive for the determination of trace amounts of [gamma]-G and used to determine the content of [gamma]-G in synthetic samples with satisfactory results. Copyright © 2008 John Wiley & Sons, Ltd.
Enhanced electrochemiluminescence of Ru(bpy)32+ by flavone compounds
Flavones such as morin, rutin, quercitrin, quercetin and wogonin were found to be able to strongly enhance the electrochemiluminescence (ECL) of the Ru(bpy)32+ system. Based on this, a novel ECL method with good stability and reproducibility could be developed for determination of flavones. Under the optimum conditions, the enhanced ECL intensity was linear with the flavones concentration in a wide range. The detection limits (defined as S:N = 3) for morin, rutin, quercitrin, quercetin and wogonin were 3.2 × 10-7 mol/L, 4.3 × 10-7, 1.8 × 10-7, 8.0 × 10-8 and 1.0 × 10-7 mol/L, respectively. In addition, the possible mechanism for the Ru(bpy)32+ ECL system in the presence of flavones is also discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Flow-injection chemiluminescence determination of enrofloxacin using the Ru(phen)32+-Ce(IV) system and central composite design for the optimization of chemical variables
The main purpose of this study was to develop an inexpensive, simple, rapid and sensitive chemiluminescence (CL) method for the determination of enrofloxacin (ENRO) using a flow-injection system. This method is based on rapid reduction of Ru(phen)33+, which is produced in the reaction between Ru(phen)32+ and acidic Ce(IV) by ENRO, producing strong CL. A central composite design (CCD) was used for optimization of the chemical variables. Regression analysis of the data from the CCD demonstrated that a second-order polynomial model is an adequate description of the surface over the factor limits studied. Optimization using CCD gave approximately four-fold better results than the single-factor-at-a-time method. Under optimal experimental conditions, the CL response was proportional to the concentration of ENRO over a wide range (0.008-3.6 µg/mL) with a correlation coefficient of 0.9986 and a detection limit of 0.003 µg/mL (3[sigma]). The relative standard deviation for 11 repeated determinations of 0.14 µg/mL ENRO was 4.2%. This method was successfully applied to the analysis of commercial formulations, spiked plasma and spiked poultry tissue. Sample analyses showed good recovery percentages for drugs and spiked plasma (95.1-103.9%). Recovery percentages for spiked poultry tissue were in the range 77.6-87.3%. The minimum sampling rate was 100 samples/h. Copyright © 2008 John Wiley & Sons, Ltd.
Electrogenerated chemiluminescence of ruthenium complex immobilized in a highly cross-linked polymer and its analytical applications
Electrogenerated chemiluminescence (ECL) of a ruthenium complex polymer modified carbon paste electrode and its analytical applications were investigated. The ruthenium complex polymer was prepared using bis(2,2-bipyridine) (4,4-dicarboxy-2,2-bipyridine) ruthenium(II). The ECL behaviours of ruthenium complex polymer modified carbon paste electrode were investigated in the absence and presence of tripropylamine (TPA). The modified carbon paste electrode exhibited long-term stability and fine reproducibility. The ECL intensity of the modified carbon paste electrode was linear with the concentration of TPA in the range 2.0 × 10-6-3.8 × 10-3 mol/L, with a detection limit (S:N = 3) of 6 × 10-7 mol/L. It was also found that raceanisodamine could enhance the ECL intensity of the modified electrode. The ECL intensity of the modified carbon paste electrode was linear with the concentration of raceanisodamine in the range 1.1 × 10-5-6.0 × 10-4 mol/L, with a detection limit (S:N = 3) of 6 × 10-6 mol/L. This work demonstrates that the entrapment of ruthenium complex in a highly cross-linked polymer is a promising approach to construct an ECL modified electrode with long-term stability and fine reproducibility. The modified electrode designed has a potential application in the ECL detector. Copyright © 2008 John Wiley & Sons, Ltd.
