A FLASH-PHOTOLYSIS INVESTIGATION OF FLAVIN PHOTOSENSITIZATION OF PURINE NUCLEOTIDES

Evidence for the existence of a reactive triplet excited state of lumiflavin has been obtained by the flash-photolysis technique. The triplet state is formed in high yield on the irradiation of flavin solutions in water or chloroform by visible light, and it has been demonstrated that it can transfer its energy to a second molecular species. The flavin-sensitised oxidation of two purine nucleotides, adenylic and guanylic acids, has been studied by flash-photolysis and by long-term irradiation, and the results suggest a triplet-triplet mechanism for the transfer of energy from the excited flavin to the nucleotide. Approximate absorption spectra of the triplet state and of a semiquinone of the flavin have been calculated from the complex transient absorption curves observed on flashing the flavin solution. The triplet decays by a first-order process where k₁= 1·1 × 10^-3. The chemiluminescence spectrum of skatole is identical with the fluorescence spectrum of o-formamidoacetophenone in the same environment Similar results for 2,3-dimethylindole lead to the identification of the acylamide anion as the emitter in indole chemiluminescence. A peroxide ring cleavage excitation mechanism is proposed. 10⁴ sec^-1 and the semiquinone by a second-order process where k₂= 0·75 × 10⁹ 1.m^-1 sec^-1. The rate constants and extinction coefficients obtained enable decay curves to be calculated which fit satisfactorily those measured with the kinetic-flash apparatus.     

Determination of Gallic Acid by Flow Injection Analysis Based on Luminol‐AgNO3‐Ag NPs Chemiluminescence System

A novel flow injection procedure has been developed for the determination of gallic acid based on the enhancement function for luminol‐AgNO₃‐Ag NPs chemiluminescence (CL) system by gallic acid. The enhancement mechanism was proposed for the reinforcing effect of the gallic acid on the CL system. The UV‐vis absorption spectrum and CL emission spectrum were applied to confirm the mechanism. The method is simple, rapid and sensitive with a detection limit of 5×10^?10 g·mL^?1 and a linear range of 8.0×10^?10–1.0×10^?7 g·mL^?1. The relative standard deviation (RSD) is 1.3% for eleven measurements of 5×10^?8 g·mL^?1 gallic acid. The method has been successfully applied to the determination of gallic acid in Chinese proprietary medicine–Jianmin Yanhou tablets and synthesized samples.     

Determination of Puerarin in Pharmaceutical Injection by Flow Injection Analysis with Acidic Potassium Permanganate–Glyoxal Chemiluminescence Detection

Abstract

A simple flow injection chemiluminescence method with synergistic enhancement has been investigated for the rapid and sensitive determination of puerarin. The method is based on the enhancing effect of puerarin on the chemiluminescence emission generated by the oxidation of glyoxal with potassium permanganate in a sulfuric acid medium. The optimization of chemical variables influencing the chemiluminescence response of the method has been carried out by applying experimental design, using the proposed flow?injection manifold. Under the optimal conditions, the enhanced chemiluminescence intensity was linear with the concentration of puerarin over the range from 10.0 ng · ml^?1 to 7.0 µg · ml^?1 (R²=0.9972) with a detection limit (3σ) of 3.0 ng · ml^?1. At a flow rate of 3.0 ml · min^?1, a complete analytical process could be performed within 0.5 min, including sampling and washing, with a relative standard deviation of less than 3.0%. The proposed method was applied successfully in the assay of puerarin in pharmaceutical injection and human urine. The mechanism of chemiluminescence reaction was discussed briefly.     

Flow Injection Chemiluminescence Sensor with Novel Rhodanine Ramification for Determination of Fenfluramine Based on Molecularly Imprinted Polymer

Abstract

Flow injection chemiluminescence (FI-CL) with molecularly imprinted polymer (MIP) was applied to determine fenfluramine. The fenfluramine-imprinted polymer was prepared with acrylamide (AM) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linker. Methyl and sulfonic group were introduced to rhodanine matrix, and a novel rhodanine ramification 3MORASP was synthesized by the author, and it was used as chemiluminescence reagent. 3-(3′-Methoxyphenyl)-5(2′-sulfonylphenylazo)-rhodanine (3MORASP), first synthesized by the authors, was used as chemiluminescence (CL) reagent. The novel flow path of FI-CL was designed, which made three merged streams of reactants injected into MIP column move through different pathways simultaneously. Fenfluramine was detected based on the reaction of fenfluramine, 3MORASP, and potassium permanganate in an acidic medium. The CL intensity was correlated linearly with the concentration of fenfluramine over the range of 1.0 × 10^?7 to 5.0 × 10^?6 g · mL^?1, and the detection limit was 9.48 × 10^?9 g · mL^?1. The relative standard deviation (RSD) was 2.4% for determination of 1.0 × 10^?6 g · mL^?1 fenfluramine (n = 11). This method was successfully applied to the determination of fenfluramine in weight-reducing tonic.     

Chemiluminescence arising from the decomposition of 1,4-dimethylnaphthalene endoperoxide applied to silica gel in the presence of NdIII,YbIII, and EuIII β-diketonates

Visible and near-IR chemiluminescence was observed upon the decomposition of 1,4-dimethylnaphthalene endoperoxide applied to silica gel in the presence of the β-diketonate complexes Nd(L)3·nH₂O, Yb(L)3·nH₂O, and Eu(L)3·nH₂O (L is 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyloctane-3,5-dionate, 1,1,1-trifluoro-3-thenoylacetonate, and acetylacetonate). Excited lanthanide ions serve as luminescent emitters with emission maxima at λ = 870 and 1060 nm for Nd^III, 990 nm for Yb^III, and 615 nm for Eu^III. Singlet oxygen generated by decomposing endoperoxide was found to play a key role in the chemiluminescence mechanism.     

A chemiluminescence photometer for trace chromium(III) determinations

The design of a simple chemiluminescence photometer is described. The sample is injected into a spectrophotometric cell containing the reagents, and the resultant chemiluminescence peak is recorded along with the peak height and peak area. The instrument includes a temperature-controlled cell holder with stirring capabilities. The determination of p.p.b. levels of chromium(III) is described. Chromium(III) enhances the chemiluminescence reaction of luminol and hydrogen peroxide in basic solutions. Useful calibration curves are obtained from 4 · 10^-9 to 10^-4 M Cr(III); 5 · 10^-10 M is the detection limit. Chromium(III) is determined in natural water samples and NBS Orchard leaves.     

Determination of Baicalin by High Performance Liquid Chromatography Coupling with Flow Injection Chemiluminescence Detection

A new method for the determination of baicalin in Scutellariae Radix extract and its preparations by high performance liquid chromatography (HPLC) coupling with flow injection chemiluminescence detection (FIA‐CL) has been developed. The method was based on the chemiluminescence reaction of potassium permanganate with baicalin in nitric acid medium; the CL intensity can be enhanced by formaldehyde. In this study, the conditions of chemiluminescence and chromatography were examined, and the schematic diagram of the HPLC‐FIA‐CL analyzer was optimized. The analytes were separated on Hypersil RP‐C18 columns (100 × 4.6 mm, I.D., 5 μm) by equality elution with 47:53 (v/v) methanol‐0.3% phosphoric acid as a mobile phase at a flow rate of 0.8 mL·min^?1 and a column temperature of 40 °C. Under the optimum condition, the CL intensity was proportional to the concentration of baicalin over the range of 4.10 × 10^?7 ? 6.15 × 10^?5mol·L^?1. The limit of detection (S/N = 3) was 2.79 × 10^?7mol·L^?1 with the relative standard deviation 2.5% (Cs = 6.15 × 10^?6 mol·L^?1, n = 5). The method has been applied to the determination of baicalin in Scutellariae Radix extract and its preparations, and satisfactory results were obtained.     

银（III）配合物-鲁米诺流动注射化学发光新体系测定肾上腺素

儿茶酚胺是一类非常重要的神经递质,在人体的心血管系统、神经系统、内分泌腺、肾脏、平滑肌等组织系统的生理活动中起着广泛的调节作用。肾上腺素为儿茶酚胺的一种,建立灵敏、高效的肾上腺素检测技术具有重要的临床意义。本文将银（Ⅲ）配合物与鲁米诺组成新的流动注射化学发光体系,利用碱性介质中肾上腺素对三价银配合物－鲁米诺化学发光体系有明显的增强效应来测定肾上腺素的含量,并据此建立了高效测定肾上腺素的流动注射化学发光新方法。在优化的条件下,该方法测定肾上腺素的线型范围为1.0×10－9～1.0×10－7 mol L-1,检出限为8.0×10－10 mol L-1,对1.5×10－8 mol L-1肾上腺素11次平行测定,其相对标偏差为2.9％。利用建立的分析方法测定了药物肾上腺素,并对三价银－鲁米诺化学发光新体系测定肾上腺素的反应机理进行了讨论。     

Molecular Imprinting-Chemiluminescence Sensor for the Determination of Amoxicillin

The amoxicillin-imprinted polymer was synthesized with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross-linker. The binding characteristic of the imprinted polymer to amoxicillin was evaluated by equilibrium binding experiments. Using the imprinted polymer as recognition material, 3-(3′-nitrophenyl)-5(2′-sulfonylphenylazo)-rhodanine (4NRASP) was synthesized by the authors and was used as chemiluminescence (CL) reagent. A novel chemiluminescence (CL) sensor for the determination of amoxicillin was developed based on the CL reaction of amoxicillin with potassium permanganate in an acidic medium. The sensor displayed excellent selectivity and high sensitivity. The linear response range of the sensor was from 5.0 × 10^?9 to 1.0 × 10^?6 g · mL^?1 (r = 0.9985) and the detection limit was 1.3 × 10^?9 g · mL^?1. The relative standard deviation for the determination of 1.0 × 10^?7 g · mL^?1 amoxicillin solution was 1.7% (n = 11). The sensor was applied to the determination of amoxicillin in urine samples with satisfactory results.     

Study on Chemiluminescence Assay of Surfactant PEG-400 Using Luminol–Hydrogen Peroxide System

Abstract

Based on the fact that nonionic surfactant polyethylene glycol-400 (PEG-400) catalyzed the chemiluminescence of luminol-H₂O₂ system, a novel and simple chemiluminescence method has been developed for the determination of PEG-400. Under the optimal conditions, the standard curve was Y = 198835X–2091.8, where the correlation coefficient (R) was 0.9999. The detection limit was 4 × 10^?5 g·ml^?1 PEG-400 and the linear range was 1.0 × 10^?4–4.0 × 10^?2g·ml^?1. The relative standard deviation was 3.2% at 2.0 × 10^?3 g·ml^?1 PEG-400 (n = 7). This method has been applied to the determination of PEG-400 in cosmetic samples with satisfactory results. Furthermore, the dynamics characteristic curve of PEG-400 in luminol-H₂O₂ system was compared to typical metallic ion and other surfactants. Moreover, the mechanism of the luminol-H₂O₂-PEG-400 chemiluminescence system was studied, assisted by fluorescence spectra and UV spectra.     

Peroxyoxalate Chemiluminescence Based on Fluorescent Conjugated Polymer for the Determination of Triton X-100

A novel peroxyoxalate chemiluminescence system has been designed for the determination of Triton X‐100 (TX‐100), in which a hydrophobic fluorescent conjugated polymer, poly[2,5‐bisnonyloxy‐1,4‐phenylene‐ethynylene‐9,10‐anthrylene] (PPEA) was employed as a fluorophor. A strong enhanced intensity of chemiluminescence (CL) was observed in the presence of TX‐100, due to the improved emission efficiency of PPEA in the presence of TX‐100. Under optimum conditions, the detection range of Triton X‐100 is between 1.0×10^?7 and 1.0× 10^?4 mol·L^?1, with a detection limit at 6.0×10^?8 mol·L^?1. The relative standard deviation is 2.4% (n=6) for 1.0×10^?6 mol·L^?1 Triton X‐100. This method provides satisfying results in the detection of TX‐100 in nature water and biological samples with high sensitivity and wide linear range.     

N-bromosuccinimide-fluorescein system for the determination of protein by flow injection chemiluminescence

A method for flow injection with chemiluminescence (CL) detection has been developed for the determination of proteins. It is based on the luminescence of the N-bromosuccinimide-fluorescein-protein system, where fluorescein is used as an energy transfer reagent in alkaline medium. The CL of the system is strongly enhanced by hexadecyl trimethyl ammonium bromide. Optimum conditions and possible mechanisms have been investigated. Under optimum experimental conditions, the linear range is from 0.4 to 40 µg·mL^?1 for egg albumin, 0.2 to 20 µg·mL^?1 for bovine serum albumin, and from 1 to 100 µg·mL^?1 for bovine hemoglobin. The detection limits are 37, 62, and 240 ng·mL^?1, respectively.     

Lanthanide(<Emphasis Type="SmallCaps">III</Emphasis>) ion as a luminescent and catalytically active reaction center of aniline condensation with butyraldehyde

A new type of chemiluminescence catalytic conversion in which the lanthanide(III) ion is a luminescent and highly efficient catalytically active center was found. Chemiluminescence (CL) is generated in the condensation reaction of aniline with butyraldehyde in DMF to form 3-ethyl-2-propylquinoline. The reaction is catalyzed by LnCl₃·6H₂O (Ln = Eu, Tb, and Ho). When EuCl₃·6H₂O and TbCl₃·6H₂O salts are used as catalysts, the CL emitters are the Eu³⁺* and Tb³⁺* excited ions. In the case of HoCl₃·6H₂O, the emitter is 3-ethyl-2-propylquinoline in the triplet-excited state. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 429–431, March, 2007.     

Electrosynthesis of Poly(azure B) from Sulfuric Acid Solution

Electrochemical polymerization of azure B from sulfuric acid solution was carried out by using cyclic voltammetry. The electrolytic solution consisted of 5.0 mmol · dm^?3 azure B and 0.3 mol · dm^?3 H₂SO₄. The temperature for polymerization was controlled at 20°C. A blue film, i.e., poly(azure B) was formed on a platinum foil and had a electrochemical reversibility, stability and a fast charge transfer ability in the 0.5 mol · dm^?3 Na₂SO₄ with pH ≤4.0 solution. The currents of both anodic and cathodic peaks are proportional to υ^1/2 at the scan rate (υ) region of 25 and 600 mV · s^?1 on the cyclic voltammograms. The conductivity of poly(azure B) is 2.8×10^?6 S · cm^?1 at 20°C. The UV‐visible spectrum and Raman spectrum of the polymer are different from those of the monomer. A possible polymerization mechanism of azure B was also proposed.     

Complicated weak interactions in a hybrid material containing tetra(isothiocyanate)cobalt(II) and 1,1′-ethylene-2,2′-dipyridinium: synthesis,crystal structure,and magnetic properties

A new inorganic–organic hybrid material, [EtdiPy][Co(NCS)₄] (1) ([EtdiPy]²⁺?=?1,1′-ethylene-2,2′-dipyridinium), was synthesized and characterized by elemental analysis, IR spectrum, UV-Vis spectrum, ESI-MS, and single-crystal X-ray diffraction. Compound 1 is monoclinic, space group P2₁/n, with a?=?21.691(5)?Å, b?=?8.639(2)?Å, c?=?21.748(5)?Å, β?=?90.124(3)°, V?=?4075.1(16)?ų, D _c?=?1.550?g cm^?3, Z?=?8, F(000)?=?1928, and R ₁?=?0.0435. The C–H···S hydrogen bond, short S···C, S···N interactions, p···π, and π···π interactions observed in the solid state of 1 give a 3-D structure. Magnetic measurements from 2 to 300?K have shown weak antiferromagnetic exchange with θ?=??0.892?K in 1.     

Complete assignment of the 13C n.m.r. spectrum of mutarotated D-ribose by integration and specific deuteration

The ¹³C n.m.r. spectrum of mutarotated D -ribose is completely assigned by using 2- and 3-deuterio-D -ribose as reference compounds. The signal intensities of the largely relaxed ¹³C n.m.r. spectrum are evaluated, and the equilibrium mixture of mutarotated D -ribose is found to consist of 6·1% α-furanose, 11·6% β-furanose, 20·3% α-pyranose and 62% β-pyranose.     

Reactions of hydroxyl radical (·OH) and oxide radical anion (O·−) with 2-aminopurine in aqueous medium

Pulse radiolysis has been used to investigate the reaction of hydroxyl radical (^·OH) and oxide radical anion (O^·−) with 2-aminopurine (2AP), a fluorescent analogue of adenine, in aqueous medium. The second-order rate constant for the reaction of ^·OH with 2AP was determined to be 3 × 10⁹ dm³ mol⁻¹s⁻¹ and for the reaction of O^·− it was 7.1 × 10⁸ dm³ mol⁻¹s⁻¹. The transient absorption spectrum obtained in the reaction of ^·OH at pH 7 has absorption maxima at 370 and 470 nm. The spectrum undergoes a time-dependent transformation at higher time-scale. The intermediate species was found to react with N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD). The yield of TMPD^·+ was calculated in terms of G(TMPD^·+) to be 3.3 × 10⁻⁷ mol J⁻¹ at pH 7. The ^·OH reactions were also carried out at pH 10 and the transient absorption spectra have λ _max at 400 and 480 nm. The transient spectra obtained in the reaction of O^·− at pH ≈14 have maxima at 400 and 480 nm. The transient intermediate species at pH 7 are assigned to the formation of 2AP-4-OH^· (54%), 2AP-5-OH^· (7%) and 2AP-8-OH^· (39%) based on the spectral evidence and TMPD^·+ build-up. Both 2AP-4-OH^· and 2AP-5-OH^· undergo OH⁻ elimination to form a radical cation. At higher pH (pH 10), the dehydration reaction of these OH-adducts leads to a N-centered radical (2AP-N(9)^·, 71%). Formation of 2AP-8-OH^· (29%) is also proposed at this pH. In the reaction of O^·− with 2AP, it is proposed that a similar nitrogen centered 2AP-N(9)^· radical is formed by an electron-transfer reaction at N(9).     

An unusually intense effect of the medium acidity on the rate of oxidation of U4+ and the yield of chemiluminescence in aqueous solutions of HClO4 containing K2S2O8

Light emission from aqueous solutions of HClO₄ containing U⁴⁺ and S₂O₈ ^2? has been observed. The emitter of chemiluminescence (CL) is the electron-excited uranyl ion (^*UO ₂ ²⁺ ), the product of U⁴⁺ oxidation. A hundredfold decrease in the HClO₄ concentration (from 1 to 0.01 mol L^?1) results in a 250-fold increase in the reaction rate constant, a 5000-fold increase in the initial CL (from 4·10⁵ to 2·10⁹ photon s^?1), a more than tenfold increase in the CL yield (from 5.6·10^?8 to 1.6·10^?6), and a 200-fold increase in the excitation yield of UO ₂ ²⁺ (from 6·10^?6 to 1.3·10^?3). The kinetic isotope effect of the reaction has been studied. The value for the ratio of the rate constantsk _H/k _D=2.1 has been determined by extrapolation to the 100% degree of deuteration of 0.1M perchloric acid. The peculiarities of the chemiluminescence stage in the reaction of U⁴⁺ oxidation in solutions of potassium persulfate were explained by the participation of the products of hydrolysis of the U⁴⁺ aqua ion (UOH³⁺ and U(OH) ₂ ²⁺ ), whose relative fraction increases as the HClO₄ concentration decreases.     

Determination of Rifampicin by Peroxomonosulfate‐Cobalt(II) Chemiluminescence System

Rifampicin can enhance the chemiluminescence (CL) of peroxomonosulfate‐cobalt(II) system, and the CL intensity is strongly dependent on the rifampicin concentrations. Based on this phenomenon, a rapid and sensitive flow injection CL method was developed for the determination of rifampicin. The relative CL intensity was linear with the rifampicin concentration over the range of 5×10^?8 to 1×10^?6 g·mL^?1 (r=0.9991), the detection limit was 7×10^?9 g·mL^?1 (S/N=3), and the relative standard deviation was 2.7% for 6×10^?7 g·mL^?1 rifampicin (n=11). Furthermore, this method was successfully applied to the determination of rifampicin in real eye drop and capsules sample.     

Rotational isomerism: XVII—solvent effects on the NMR spectra and rotamer energies of some tetrahaloethanes

The NMR spectra of 1,1-dichloro-2,2-difluoroethane ( 1 ), 1,1-dibromo-2,2-difluoroethane ( 2 ), meso and dl 1,2-dichloro-1,2-difluoroethane ( 3 ) and 1,1,2,2-tetrachloroethane ( 4 ) have been analysed in a number of solvents. The ¹⁹F spectrum of 3 in L-bornyl acetate at 56·4 and 94·1 MHz allows an unambiguous identification of the meso and dl isomers. The spectra of the d and l isomers consist of two AA′XX′ spectra with a small chemical shift difference between the d and l forms, whilst that of the meso form is an apparent AA′XX′ spectrum at 56·4 MHz but an ABXX′ spectrum at 94·1 MHz, the ¹⁹F nuclei in this isomer being anisochronous in this solvent. The observed solvent and temperature dependence of the couplings of 1, 2 , meso 3 and 4 when combined with the calculated solvation energies, allow the determination of the rotamer energies and couplings in these molecules. The rotamer energy differences (E_g – E_t) in the liquid and vapour states are 0·6 and ?0·2 kcal/mol ( 1 ); 0·4 and ?0·5 kcal/mol ( 2 ); 0·9 and 0·2 kcal/mol meso ( 3 ) and ?0·1 and ?0·8 kcal/mol ( 4 ). The ³J(HH), ³J(HF) and ³J(FF) couplings for the distinct rotamers are considered together with those of similarly constituted molecules. The general agreement demonstrates that the solvation theory may be applied to multisubstituted ethanes without any basic modifications. The trans oriented HH couplings show a linear substituent electronegativity dependence, which differs appreciably from that obtained for disubstituted ethanes, however. The gauche couplings show the influence of dihedral angle variations as well as substituent electronegativity. The rotamer ³J(FF) couplings in meso 3 are ?38·2 Hz (J_t) and ?17·4 Hz (J_g).