Determination of resveratrol in red wine by solid phase extraction-flow injection chemiluminescence method

A sensitive flow injection chemiluminescence method has been developed for the detection of resveratrol in red wine based on the fact that resveratrol can greatly enhance chemiluminescence reaction between KMnO_4 and HCHO in sulfuric acid medium. Analytes were pre-concentrated on solid sorbents (C_(18) solid-phase extraction cartridges).Under the optimum conditions,the proposed method allows the measurement of resveratrol over the range of 1.32×10~(-8) to 1.32×10~(-5) mol/L with a detection limit of 3.30×10~(-9) mol/L,and the relative standard deviation for 1.32×10~(-5) mol/L resveratrol (n=11) is 3.8%.This method has been successfully applied for the determination of the resveratrol in red wine.Furthermore,the possible reaction mechanism was also discussed.     

Origin of the red shifts in the optical absorption bands of nonplanar tetraalkylporphyrins

The view that the large red shifts seen in the UV-visible absorption bands of peripherally crowded nonplanar porphyrins are the result of nonplanar deformations of the macrocycle has recently been challenged by the suggestion that the red shifts arise from substituent-induced changes in the macrocycle bond lengths and bond angles, termed in-plane nuclear reorganization (IPNR). We have analyzed the contributions to the UV-visible band shifts in a series of nickel or zinc meso-tetraalkylporphyrins to establish the origins of the red shifts in these ruffled porphyrins. Structures were obtained using a molecular mechanics force field optimized for porphyrins, and the nonplanar deformations were quantified by using normal-coordinate structural decomposition (NSD). Transition energies were calculated by the INDO/S semiempirical method. These computational studies demonstrate conclusively that the large Soret band red shifts ( approximately 40 nm) seen for very nonplanar meso-tetra(tert-butyl)porphyrin compared to meso-tetra(methyl)porphyrin are primarily the result of nonplanar deformations and not IPNR. Strikingly, nonplanar deformations along the high-frequency 2B(1u) and 3B(1u) normal coordinates of the macrocycle are shown to contribute significantly to the observed red shifts, even though these deformations are an order of magnitude smaller than the observed ruffling (1B(1u)) deformation. Other structural and electronic influences on the UV-visible band shifts are discussed and problems with the recent studies are examined (e.g., the systematic underestimation of the 2B(1u) and 3B(1u) modes in artificially constrained porphyrin structures that leads to a mistaken attribution of the red shift to IPNR). The effect of nonplanar deformations on the UV-visible absorption bands is then probed experimentally with a series of novel bridled nickel chiroporphyrins. In these compounds, the substituent effect is essentially invariant and the amount of nonplanar deformation decreases as the length of the straps connecting adjacent meso-cyclopropyl substituents decreases (the opposite of the effect observed for conventional strapped porphyrins). Several spectroscopic markers for nonplanarity (UV-visible bands, resonance Raman lines, and (1)H NMR resonances) are found to correlate with time-averaged deformations obtained from an NSD analysis of molecular dynamics snapshot structures. These results suggest that UV-visible band shifts of tetrapyrroles in proteins are potentially useful indicators of changes in nonplanarity provided other structural and electronic factors can be eliminated.     

Coupling chemiluminescence with capillary electrophoresis to analyze single human red blood cells

In this paper, we describe a new method for determination of hemoglobin of single red blood cells by coupling chemiluminescence with capillary electrophoresis (CL-CE). The chemiluminescent detection is based on the catalytic effects of hemoglobin on the luminol-hydrogen peroxide reaction. The conditions of chemiluminescent reaction and capillary electrophoresis were investigated. Hemoglobin in human blood samples was detected with the present method, the linear range from 1.7 μg mL⁻¹ to 6.8 μg mL⁻¹ was tested, and the correlation coefficient of 0.997 and low detection limit of 0.17 μg mL⁻¹ (approximately 2.2 pg, S/N = 3) were obtained. Cell injection procedure was improved, and the method was successfully used to determine hemoglobin of single red blood cells and the statistical result of the average content of hemoglobin in 26 human red blood cells was 23.6 pg. Compared to other current methods, CE with CL system is simple, sensitive and will become an attractive alternative method for single cell analysis.     

NaHg: A variant of the cesiumchloride structure structural relations and electronic structure

The crystal structure of the gold-bronce coloured, metallic NaHg, which was already determined earlier, is characterized by nearly square planar Hg₄ clusters condensed to zig-zag chains via common edges. We discuss the hitherto unknown relation of the orthorhombic NaHg structure to the CsCl type (B2). and present calculations of the electronic structures for the hypothetical B2 structure as well as for the real orthorhombic structure by means of the relativistic LMTO method. A clear tendency is observed towards a population of the mercury 6 p-states, which are empty in the free atom in its ground state. This population is the most important contribution to the bonding between the mercury atoms in the cluster chains. Thus the simple chemical picture, whereafter a partial electron transfer should take place from the electropositive sodium to mercury, is in accordance with the calculation results.     

Highly sensitive chemiluminescence flow-injection detection of the red tide phytoplankton Heterosigma carterae

Two chemiluminescent flow-injection analysis systems for the detection of the red tide Phytoplankton Heterosigma carterae (formerly known as Heterosigma akashiwo) have been developed. In one system, the superoxide (O⁻₂) released by H. carterae reacts with 2-methyl-6-(p-methoxyphenyl)-3,7-dihydroimidazo[1,2-a]-pyrazin-3-one (MCLA), a superoxide specific probe. In the other system, the hydrogen peroxide released by H. carterae reacts with luminol catalyzed by Arthromyces ramosus peroxidase (ARP). The chemiluminescence is detected by a photomultiplier tube. This system is capable of the rapid determination of H. carterae; the time required for one measurement cycle is ca. 2 min using MCLA-dependant luminescence or 1 min in luminol/ARP luminescence. A linear response was observed from 10² to 10⁵ cells ml⁻¹ H. carterae. Several other species of phytoplankton gave no response using this system. The detection limit of this method is suitable for detecting H. carterae in the early stage of red tide formation.     

Photographic homogeneous immunoassay based on luminol chemiluminescence catalyzed by hemoglobins leaked from complement-hemolyzed red blood cells

Summary Human serum albumin (HSA) and complement were photographically assayed. The complement activated by the formed antigen-antibody complex causes the hemolysis of red blood cells. Leaked hemoglobins catalyze the chemiluminescent reaction of luminol and hydrogen peroxide (H₂O₂). The resulting emission was recorded on instant film.     

NaK chemiluminescence

The gas phase reaction between a mixture of K and Na and CBr₄ produces, under low-density conditions, emission from high-lying vibrational levels (υ′ > 9) of the B ¹ Π state of NaK.     

Indigo chemiluminescence

Indigotin in basic solutions of polar aprotic solvents reacts with atmospheric oxygen yielding isatin. The reaction is accompanied by emission of light with a quantum yield equal to 2.6×10^?4 Einstein/mol. The spectral distribution of the indigotin chemiluminescence is that of the isatin fluorescence. Addition of equimolar amounts of isatin to the reaction mixture raises the chemiluminescence quantum yield to 5.3×10^?4 Einstein/mol. A mechanism involving the intermediate formation of indigotin dioxetan is proposed.     

Clinical applications of chemiluminescence

This article reviews the clinical applications of chemiluminescence in routine testing and surveys the diverse applications of chemiluminescence in clinical research. In routine clinical testing, chemiluminescent labels (acridinium ester, acridinium sulfonamide) and detection reactions for peroxidase and alkaline phosphatase enzyme labels (luminol and adamantyl 1,2-dioxetane-based reactions, respectively) are widely used in immunoassay and nucleic acid probe assays (e.g. hybridization protection assay, Hybrid Capture^® assay). In clinical research the sensitivity, dynamic range and diversity of chemiluminescent assays has led to a vast range of applications, notably in protein and nucleic acid blotting, microarray-based assays, monitoring reactive oxygen species, and as detection reactions for substances separated by HPLC, capillary electrophoresis (CE), and flow-injection analysis.     

Laser chemiluminescence of LiCa

Emission from diatomic LiCa molecules was obtained upon pumping a mixture of Li and Ca vapors with an Ar⁺ion laser. The excited LiCa molecules were formed via reactions of excited Li₂ dimers with Ca atoms. The LiCa emission was analyzed spectroscopically and found to be in good agreement with a synthetic spectrum derived from ab initio calculations of the LiCa potential-energy curves     

Electronic structure of excimer molecular lasers

The electronic structure, potential energy curves, and radiative transition probabilities of excimer systems have been examined using quantum mechanical methods. These molecules are characterized by repulsive or weakly bound ground state potential curves and by bound, strongly ionic, or Rydberg, excited states. They constitute a very interesting class of molecules which offer the possibility for high power, high efficiency UV laser operation. Calculations have been carried out using the density functional SCF -X_α method, modified extensively to correct for well known errors arising from approximations to the potential and exchange terms. A limited number of ab initio calculations were also carried out for comparison purposes. For the ArF system we find that the lowest excited ionic state has symmetry ²∑${}_{\text{½}}^{\text{+}}$ , and that the dominant laser transition observed at 1933 Å should be assigned to B ²∑${}_{\text{½}}^{\text{+}}$ → X ²∑${}_{\text{½}}^{\text{+}}$ . The C ²Π_3/2 → X ²∑${}_{\text{½}}^{\text{+}}$ transition is calculated to be two orders of magnitude smaller in emission intensity than the dominant transition, thus ruling out this assignment for the observed laser line in ArF. Preliminary calculations carried out for Ar₂F indicate that the bound upper ionic state has ²B₂ symmetry and that the most probable ground state also has ²B₂ symmetry. This polyatomic system is predicted to exhibit a broadband emission spectrum with a relatively long radiative lifetime.     

Perylene excimer fluorescence in cyclohexane

The blue monomer fluorescence of perylene in cyclohexane is replaced by an orange excimer fluorescence emission upon freezing the solution with increasing pressure. The temperature dependence of the excimer decay is characterized by a radiative lifetime of 80 nsec and an activation energy of 670 cm_?1.     

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

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

Structure in excimer line shape

Recently monomer-like structured emission has been observed in the spectra of excimers both in solids and in solution. In a two-dimensional model potential an intramolecular mode is considered in addition to the relative degree of freedom. It is shown that under certain conditions structured line shapes are obtained.