A Simple and Sensitive Spectrofluorimetric Method for Analysis of Some Nitrofuran Drugs in Pharmaceutical Preparations

A simple, rapid, selective and sensitive spectrofluorimetric method was described for the analysis of three nitrofuran drugs, namely, nifuroxazide (NX), nitrofurantoin (NT) and nitrofurazone (NZ). The method involved the alkaline hydrolysis of the studied drugs by warming with 0.1 M sodium hydroxide solution then dilution with distilled water for NX or 2-propanol for NT and NZ. The formed fluorophores were measured at 465 nm (λ _Ex 265 nm), 458 nm (λ _Ex 245 nm) and 445 nm (λ _Ex 245 nm) for NX, NT and NZ, respectively. The reaction pathway was discussed and the structures of the fluorescent products were proposed. The different experimental parameters were studied and optimized. Regression analysis showed good correlation between fluorescence intensity and concentration over the ranges 0.08–1.00, 0.02–0.24 and 0.004–0.050 μg ml⁻¹ for NX, NT and NZ, respectively. The limits of detection of the method were 8.0, 1.9 and 0.3 ng ml⁻¹ for NX, NT and NZ, respectively. The proposed method was validated in terms of accuracy, precision and specificity, and it was successfully applied for the assay of the three nitrofurans in their different dosage forms. No interference was observed from common pharmaceutical adjuvants. The results were favorably compared with those obtained by reference spectrophotometric methods.     

Second-derivative Synchronous Fluorometric Method for the Simultaneous Determination of Cinnarizine and Domperidone in Pharmaceutical Preparations. Application to Biological Fluids

A rapid, simple and highly sensitive second derivative synchronous fluorometric method has been developed for the simultaneous analysis of binary mixture of cinnarizine (CN) and domperidone (DOM). The method is based upon measurement of the native fluorescence of these drugs at Δλ = 80 nm in aqueous methanol (50% V/V). The different experimental parameters affecting the native fluorescence of the studied drugs were carefully studied and optimized. The fluorescence-concentration plots were rectilinear over the range of 0.1 to 1.3 μg mL⁻¹ and 0.1–3.0 μg mL⁻¹ for CN and DOM, respectively with lower detection limits of 0.017 and 5.77 × 10⁻³ μg mL⁻¹ and quantification limits of 0.058 and 0.02 μg mL⁻¹ for CN and DOM. The proposed method was successfully applied for the determination of the studied compounds in synthetic mixtures and in commercial tablets. The results obtained were in good agreement with those obtained with reference methods. The high sensitivity attained by the synchronous fluorometric method allowed the determination of CN in real and spiked human plasma. The mean % recoveries in case of spiked human plasma (n = 3) were 96.39 ± 1.18 while that in real human plasma (n = 3) was 104.67 ± 4.16.     

Visualization of scavenging flow in the design of small two-stroke engines

An experimental test rig is presented, which enables visual examination of the internal flow of piston ported two-stroke cylinders. Similarity laws are applied to design the layout of the set-up. The reasons to use a liquid to represent the scavenging fluid are explained. Experiments are carried out which visualize the scavenging flow inside the cylinder. Colours play an important role in the visualization of flows. Careful selection of the dyes and the particular arrangement of different colours produce features of the three-dimensional and unsteady flow under investigation. The potential for future investigations to become an integrated part of the design process of small two-stroke engines is demonstrated.     

Parameter Recovery in Frequency-Domain Time-Resolved Fluorescence Spectroscopy; Resolution of the Prototropic Forms of 5-Carboxyfluorescein in the Physiological pH Range

In time-resolved fluorescence spectroscopy, the resolution of fluorescence species becomes increasingly difficult as their respective lifetimes get closer. For a biexponential decay, a factor of 1.4 between the two decay times is commonly accepted as the practical resolution limit. The goal of the present contribution is to characterize the fluorescence probe 5-carboxyfluorescein using frequency-domain time-resolved fluorescence spectroscopy (FD-TRFS). To resolve the different prototropic forms of this probe, the limit above had to be overcome. For this purpose, the standard global analysis method was used, and special emphasis was put on the errors associated with the recovered parameters. In particular, a Monte Carlo simulation was performed to estimate these errors and the results of this analysis were compared with those delivered by software packages widely used in the field. The lifetimes of the trianionic and dianionic forms of 5-carboxyfluorescein were 4.01 ± 0.06 and 3.03 ± 0.09 ns, respectively, and the pK _a for this acid–base equilibrium was determined to be 6.9 ± 0.3.     

Laser-induced fluorescence spectroscopy of FeS in the visible region

The laser-induced fluorescence excitation spectra of jet-cooled FeS molecules have been recorded in the energy range of 18 900-21 600 cm⁻¹, in which four parallel and one perpendicular transitions were identified for the first time. Spectroscopic constants of the observed excited states of FeS were determined by analyzing their rotationally resolved spectra. In addition, the lifetimes of most observed bands were also measured.     

不同产地的螺旋藻粉中元素含量分析

采用X射线荧光光谱分析法(XRF)测定了5个不同产地的螺旋藻粉中钾、钠、钙、镁、铁、锌、锰等元素的含量。螺旋藻含有丰富的人体所必需的矿质元素,不同产地的螺旋藻粉的主要元素谱基本相同,但各种元素的含量存在一定的差异。钾的含量最高,平均为5.00%,钠含量为0.352%,平均钠/钾比为0.070。探讨了钾、钠/钾比与螺旋藻的医疗保健作用的关系,较低的钠/钾比有利于高血压患者恢复健康。所用测定方法具有简便、快捷、准确、灵敏度高、适用元素多和含量范围广等特点。研究结果为提高螺旋藻矿质元素的品质以及进一步开发利用螺旋藻提供了新的科学依据。     

Anomalies in oxygen-induced quenching of electronically excited states of 4,4′-bis[2-(1,3)-benzoxazol-2-yl)ethenyl]biphenyl in the vapor phase

From oxygen-induced quenching of polarized fluorescence of 4,4′-bis[2-(1,3-benzoxazol-2-yl)ethenyl]biphenyl, we have observed structural transformation in electronically excited molecules with retention of fluorescent capability, initiated by collisions with oxygen. Replacing two hydrogen atoms with fluorine in the ortho positions of the diphenyl moiety of the molecule leads to absence of quenching upon collisions with oxygen molecules, owing to the electronegative properties of fluorine atoms. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 902–905, November–December, 2008.     

Metal-enhanced fluorescence of graphene oxide by palladium nanoparticles in the blue-green part of the spectrum

Graphene oxide(GO) has a wide fluorescence bandwidth,which makes it a prospective candidate for numerous applications.For many of these applications,the fluorescence yield of GO should be further increased.The sp~2-hybridized carbons in GO confine the π-electrons.Radiative recombination of electron-hole pairs in such sp~2 clusters is the source of fluorescence in this material.Palladium nanoparticles are good catalysts for sp~2 bond formations.We report on the preparation of GO,palladium nanoparticles and their nanocomposites in two different solvents.It is shown that palladium nanoparticles can considerably enhance the intrinsic fluorescence of GO in the blue-green part of the visible light spectrum.Fluorescence enhancement has been attributed to the catalytic role of palladium nanoparticles in increasing the number of sp2 bonds of GO with the molecules of the surrounding media.It is shown that palladium nanoparticles could be the nanoparticle of choice for fluorescence enhancement of GO because of their catalytic role in sp2 bond formation.     

Effect of low radiation doses on the content of endogeneous porphyrins in the living organism

Investigations of urinary excretion of copro- and uroporphyrins from the organism of healthy humans and humans exposed to low radiation doses (children and adolescents, adults and pregnant females) have been performed with the use of the high-sensitivity fluorescence method of determination of endogeneous porphyrins in the living organism. The ranges of the most probable concentrations of copro- and uroporphyrins in the morning portion of urine were determined for three control groups of healthy humans and six test groups of humans exposed to low radiation doses. It was established that the concentration of endogeneous porphyrins excreted from the organism of adults subjected to the action of ionizing radiation is significantly decreased as compared with the norm and that living for a long time in radionuclidecontaminated territories leads to steady disturbances of porplyrin excretion from the organism. It was also established that the concentration of endogenous porphyrins excreted from the organism of children and adults evacuated from the radionuclide-contaminated zone is significantly increased as compared with the norm. Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belaus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 545–548, July–August, 1999.     

激光诱导荧光水体污染遥测数据定量分析方法

在紫外光的激发下,污染水体中的溶解有机物(DOM)会产生特定的荧光光谱,因此利用激光诱导荧光(LIF)可对水体中的溶解有机物的含量进行定量分析,从而可估计出水体富营养化的程度。提出了一种用于对水质遥测数据进行定量分析的方法,这是一种基于遗传算法(GA)的光谱分离算法。首先确定拉曼散射信号和溶解有机物的荧光在404nm波段的信号强度,然后再利用拉曼散射信号对DOM荧光光谱进行归一化处理。根据浓度校准曲线可得到水体中的溶解有机物的浓度。     

Collisional Depolarization of the Luminescence of Asymmetric Top Molecules in the Gas Phase

To describe the collisional depolarization of the luminescence of asymmetric top polyatomic molecules, integral and integrodifferential forms of master equations, in which the effect of collisions is determined by the conditional probabilities of an instantaneous error of rotational phase variables, have been obtained. A symmetry analysis of the master equations has been performed, and it has been shown that in the general case the evolution of optically induced anisotropy is given by five independent relaxation components. The kinetic equations derived are initial equations for specific calculations of the anisotropy relaxation in various collisional models. They make it possible to study the influence of the angular momentum transfer efficiency on the orientational relaxation of anisotropy in a wide range of buffer medium densities: from free rotation to binary collisions in the gas and then to rotational diffusion.     

NO2 在第二电子吸收带的光解

运用单光子激光诱导荧光方法 ,研究了NO2 分子在第二吸收带的光解反应动力学 .首次报道了NO2(B2 B2 态 )光解初生态产物NO自由基的v″ =1,2的转动分布 .发现了NO自由基v″ =1的明显双模式分布 .进而提出了可能有两种竞争机理控制该反应     

有机溶剂中C_(60)荧光的研究

本文研究了C6 0 溶于有机溶剂时 ,荧光能级的变化和荧光强度的大幅度增强。通过拉曼光谱结果显示 ,发现C6 0 分子与溶剂分子之间没有发生显著的化学反应。     

双光子成像观测衰老对小鼠卵母细胞内DNA甲基转移酶表达的影响

量子点(QD)具有抗漂白能力强、量子产率高、激发谱宽和发射谱窄等优点,在生物荧光标记领域有较广泛的应用。利用QD 585和Hoechst 33342 (H342)双标记小鼠卵母细胞中DNA甲基转移酶(Dnmt)和染色体,通过双光子成像同时双通道探测它们的荧光图像,获得了Dnmt蛋白表达的三维空间分布。发现老龄小鼠卵母细胞不适合体外培养成熟：该成熟方式不仅引起老龄小鼠卵母细胞Dnmt蛋白含量的变化,而且还改变了它们在胞质中的空间分布。这些改变可能与异常的甲基化修饰有关。     

Femtosecond Dynamics of Optically Induced Anisotropy of Complex Molecules in the Gas Phase

The evolution of optically induced anisotropy in an equilibrium ensemble of free asymmetric tops under collisionless conditions has been investigated theoretically and experimentally. The dynamics of the orientation correlation functions has been studied, the results of femtosecond experiments on measurement of relaxation of the optically induced anisotropy for perylene in the gas phase are presented, and their interpretation within the framework of the theory developed is given. It is shown that in contrast to stationary anisotropy, its time kinetics has more complete characteristic information about the dynamics of vector correlations in a molecular ensemble.     

平面激光诱导荧光技术在交错电极介质阻挡放电等离子体研究中的初步应用

利用平面激光诱导荧光技术对交错电极介质阻挡放电过程中产生的痕量组分NO进行了检测. 通过数值模拟对实验结果进行了分析说明,并对介质阻挡放电等离子体流动控制原理进行了简要分析. 此外还通过平面激光诱导荧光技术对等离子体诱导流动进行了直观显示. 关键词： 平面激光诱导荧光 等离子体 介质阻挡放电     

Application of Atomic Fluorescence Spectrometry to the Determination of Sulfide Ion in Sewage Waters

Atomic fluorescence spectrometry and direct flame photometry are evaluated as alternative methods for the determination of inorganic sulfide in municipal sewage. The sulfide is volatilized as H₂S from the sewage influent or effluent sample, which has been stabilized by a 0.05 M sodium ascorbate buffer. Both flame spectrometric methods are more sensitive than the standard colorimetric method, but quantification is easier for the atomic fluorescence method. The latter technique has a wide linear dynamic range and is unaffected by a gradual increase in the residual H₂S level in the system. The atomic fluorescence signal is also unaffected by the presence of volatile hydrocarbons in the sewage. The results obtained with the fluorescence method agree well with those obtained with the standard method, while the flame photometric results are low. Studies on the effect of metal ions on the fluorescence signal indicate that the method determines “total sulfide”.     

Delayed Luminescence of 8-Aza-D-Homogone-1,3,5(10),13-Tetraene-12,17a-Dione in the Gas Phase and Solid Solutions

It is shown that the delayed-luminescence spectrum of 8-aza-D-homogone-1,3,5(10),13-tetraene-12,17a-dione (8-aza-D-homogonane) in the gas phase comprises a band of thermally activated delayed fluorescence and a band of annihilation delayed fluorescence that are respectively due to the C- and D-centers representing products of photo-and thermotransformations of the initial steroid for which we failed to detect delayed luminescence. The triplet-triplet energy transfer from the C-centers to the D-centers has been detected and its efficiency has been determined. It has been established that, in a frozen hexane solution (T = 77 K) of the substance taken from a vacuum cuvette after the investigation of initial 8-aza-D-homogonane in the gas phase, only the C- and D-centers phosphoresce. For a frozen solution of the initial steroid in a vitrifying mixture of tetrahydrofuran and toluene, a phosphorescence of both the steroid itself (λ _max ^phos = 415 nm) and the C- and D-centers (λ _max ^phos = 498 and 532 nm, respectively) was detected. This indicates that even the initial steroid kept at room temperature contains products of its transformation whose concentration increases on irradiation and heating. The C- and D-centers are stable molecules.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 2, pp. 192–197, March–April, 2005.     

Davydov Splitting in Spectra of Cyanine Dye J-Aggregates, Formed on the Polynucleotides

It was found in our previous work (T. Y. Ogul'chansky et al. (2001) Spectrochimica Acta Part A 57, 2705–2715) that the carbocyanine dye Cyan iPr forms J-aggregates in the groove of poly(dA)-poly(dT). In the present paper we study in detail the spectral properties and energy levels structure of the Cyan iPr J-aggregates by means of absorption and fluorescence spectroscopy and polarization measurements. The energy structure of an aggregate consists of at least two exciton zones, and dipole moments of the absorption transitions to these zones are oriented at an angle of about 90° one to another. It was supposed that the transition moment of the lower zone is parallel to the polynucleotide axis and the moment of the upper zone is perpendicular. The fluorescent transitions are possible only from the lower exciton zone, while the excitations of higher zone undergo nonradiative transitions to the lower one.