fluorescence analysis
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Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 206
Mariia Nesterkina ◽  
Serhii Smola ◽  
Nataliya Rusakova ◽  
Iryna Kravchenko

Hydrazones based on mono- and bicyclic terpenoids (verbenone, menthone and carvone) have been investigated in vitro as potential biomembrane penetration enhancers. In this regard, liposomes composed of lecithin or cardiolipin as phospholipid phase components with incorporated fluorescence probes have been prepared using the thin-film ultrasonic dispersion method. The mean particle size of the obtained liposomes, established using laser diffraction, was found to be 583 ± 0.95 nm, allowing us to categorize them as multilamellar vesicles (MLVs) according to their morphology. Pursuant to fluorescence analysis, we may assume a reduction in microviscosity and, consequently, a decrease in the packing density of lecithin and cardiolipin lipids to be the major mechanism of action for terpenoid hydrazones 1–15. In order to determine the molecular organization of the lipid matrix, lipids were isolated from rat strata cornea (SCs) and their interaction with tested compounds was studied by means of Fourier transform infrared spectroscopy. FT-IR examination suggested that these hydrazones fluidized the SC lipids via the disruption of the hydrogen-bonded network formed by polar groups of SC constituents. The relationship between the structure of terpenoid hydrazones and their ability to enhance biomembrane penetration is discussed.

2021 ◽  
Vol 12 (1) ◽  
pp. 179
Alice Dal Fovo ◽  
Sara Mattana ◽  
Antonina Chaban ◽  
Diego Quintero Balbas ◽  
João Luis Lagarto ◽  

Fluorescence analysis of materials used as binders and coatings in artworks is often hampered by numerous factors, leading to uncertainties in data interpretation. Fluorescence lifetime (FL) measurements enable improvement of the specificity with respect to steady-state measurements by resolving the decay dynamics of the fluorophore emissions. In this work, layers of natural resin, oil, and wax—in pure form, pigmented, in mixtures, and spread on different substrates—were analyzed using a compact, portable, fiber-based FL instrument. FL data were processed via the phasor method and integrated with Raman spectroscopy to obtain complementary chemical information on the different substances. It was observed that the τ-phase of the mixtures is affected by both the pigments and the dispersing medium, and that the presence of the metal substrate contributes to changes in the FL of mixtures. The results obtained with our portable FL system combined with Raman spectroscopy pave the way for a systematic study of a larger number of materials for future in situ applications on works of art.

2021 ◽  
Vol 6 (4) ◽  
pp. 147-153
Sergey V. Lakhtionov ◽  
Ivan S. Chumakov ◽  
Sergey G. Filinkov ◽  
Dmitry M. Chukin ◽  
Evgeny  N. Ishmetyev

Background. The authors investigate the problems arising from the lack of information on the chemical composition of the drilled rocks during the construction of a well. Aim. The aim of this study is to determine the possibilities and efficient application of the streaming XRF method for determining the elemental composition of unwashed drill cuttings. The contribution of the paper lies in the lack of experience in the world practice of using streaming XRF analyzers. Materials and methods. Furthermore, the authors evaluate the possibility to use the streaming XRF method for analyzing the chemical composition of drill cuttings for the development of the oil industry. At the same time, the application of the proposed method is justified. The basis of this study are the results of the application of the streaming XRF method using the CON-X 02 streaming spectrometer for analyzing the chemical composition of drill cuttings not washed from drilling mud. This project has been implemented according the technological project between Gazpromneft — NNGGF LLC in cooperation with Nosov Magnitogorsk State Technical University and Gazpromneft — STC LLC. Result. The article presents the results of determined main elements of the composition of drill cuttings. The authors have carried out the analysis of changes in the intensity of the characteristic lines of the main components from the sampling depth. Simultaneously, the authors show the possibilities to derive correlation curves for various elements characteristic of certain rocks in the geological section of a particular field. Moreover, the study reveals the identification and characteristics of geochemical signs of specific target layers. Conclusions. Based on the results of the study, authors may conclude that to obtain the correct results on the intensity of spectral lines of various chemical elements during streaming XRF analysis, there is no need to flush the cuttings from the drilling fluid. Finally, it is possible to qualitatively control the main elements of the composition of the drill cuttings.

Nina Merezhko ◽  
Yuliia Vovk ◽  
Volodymyr Indutnyi ◽  
Kateryna Pirkovich ◽  
Valentyna Davydiuk ◽  

This paper reports the results of studying the chemical composition of the surface of 4 objects of cold weapons of the 19th and early 20th centuries, made of iron – bayonet knives and sabers. This makes it possible to establish the signs of authenticity of cold weapon samples made of iron in that chronological period. An authentic procedure has been proposed for examining the chemical composition of the surface of historical objects of cold weapons by rubbing the samples with cotton wool swabs and their subsequent investigation. This makes it possible to explore objects of cold weapons, whose size is large, as well as simplify the very procedure for studying objects of historical and cultural value. Using the X-ray fluorescent chemical analyzer Expert Mobile, chemical elements were found at the surface of samples of cold weapons made of iron. The presence of such elements is the result of the process of re-crystallization and self-purification of metal during a long history of its life. Elements found in almost every rubbing sample were identified: calcium, ferrum, zinc, cuprum, and chlorine. The studies of cold weapons samples testify to the heterogeneity of the composition of patina formations on their surface, which confirms the authenticity of ancient objects. In addition, the studies have shown a difference in the chemical composition of surface layers of different parts of individual samples of antique cold weapons, which may indicate different times or different technology for their manufacture. The fluorescence spectra of the obtained rubbing of individual samples of cold weapons were compared with "pure" material, which made it possible to identify elements removed from the surface of objects. The study results are important indicators to confirm the authenticity of cultural monuments and the technology of their manufacture in the past.

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7892
Servando Chinchón-Payá ◽  
Julio E. Torres Martín ◽  
Antonio Silva Toledo ◽  
Javier Sánchez Montero

A correct assessment of the pathologies that can affect a reinforced concrete structure is required in order to define the repair procedure. This work addresses the challenge of quantifying chlorides and sulphates directly on the surface of concrete. The quantification was carried out by means of X-ray fluorescence analysis on the surface of concrete specimens at different points with portable equipment. Concrete prisms were made with different amounts of NaCl and Na2SO4. To avoid the influence of coarse aggregate, a qualitative estimate of the amount of coarse aggregate analyzed has been made, although the results show that there is no significant influence. Monte Carlo simulations were carried out in order to establish the necessary number of random analyses of the mean value to be within an acceptable range of error. In the case of quantifying sulphates, it is necessary to carry out six random analyses on the surface, and eight measurements in the case of quantifying chlorides; in this way, it is ensured that errors are below 10% in 95% of the cases. The results of the study highlight that a portable XRF device can be used in situ to obtain concentrations of chlorides and sulphates of a concrete surface with good accuracy. There is no need to take samples and bring them to a laboratory, allowing lower overall costs in inspection and reparation works.

2021 ◽  
Vol 7 (9(63)) ◽  
pp. 22-24

В работе рассматриваются факторы, влиющие на максимальное выделение концентрата лантана и церия из отработанного катализатора крекинга по фторидной технологии. Их содержание в отработанном катализаторе крекинга сопоставимо в содержанием в промышленно перерабатываемых рудах. Используются в качестве вскрывающих агентов серной кислоты и фторида аммония. Использованы такие методы, как ИК-спектроскопия, рентгенофлуоресцентный анализ, сканирующая электронная микроскопия. В результате получен концентрат лантаноидов, которые содержатся в виде фторидов. Концентрация лантаноидов возрастает в несколько раз. The article discusses the factors influencing the maximum release of lanthanum and cerium concentrate from a spent cracking catalyst using fluoride technology. Their content in the spent cracking catalyst is comparable to the content in industrially processed ores. They are used as the opening agents of sulfuric acid and ammonium fluoride. Methods such as IR spectroscopy, X-ray fluorescence analysis, scanning electron microscopy were used. As a result, a concentrate of lanthanides was obtained, which are contained in the form of fluorides. The concentration of lanthanides increases several times.

Catalysts ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1539
Dmitry Mauer ◽  
Sergey Belenov ◽  
Vladimir Guterman ◽  
Anatoly Nikolsky ◽  
Alexey Kozakov ◽  

The composition, structure, catalytic activity in the ORR and stability of PtCo/C materials, obtained in two stages and compared with commercial Pt/C analogs, were studied. At the first stage of the synthesis performed by electrodeposition of cobalt on a carbon support, a CoOx/C composite containing 8% and 25 wt% cobalt oxide was successfully obtained. In the second step, PtCoOx/C catalysts of Pt1.56Co and Pt1.12Co composition containing 14 and 30 wt% Pt, respectively, were synthesized based on the previously obtained composites. According to the results of the composition and structure analysis of the obtained PtCoOx/C catalysts by X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) methods, the formation of small bimetallic nanoparticles on the carbon support surface has been proved. The resulting catalysts demonstrated up to two times higher specific catalytic activity in the ORR and high stability compared to commercial Pt/C analogs.

2021 ◽  
Michela Marcatti ◽  
Anna Fracassi ◽  
Mauro Montalbano ◽  
Chandramouli Natarajan ◽  
Balaji Krishnan ◽  

Abstract Background. Alzheimer’s Disease (AD) is characterized by progressive cognitive decline due to accumulating synaptic insults by toxic oligomers of amyloid beta (AβO) and tau (TauO). There is growing consensus that preventing these oligomers from interacting with synapses might be an effective approach to treat AD. However, recent clinical trial failures suggest low effectiveness of targeting Aβ in late-stage AD. Researchers have redirected their attention toward TauO as the levels of this species increase later in disease pathogenesis. Here we show that AβO and TauO differentially target synapses and affect each other's binding dynamics. Methods. Binding of labeled, pre-formed Aβ and tau oligomers onto synaptosomes isolated from the hippocampus and frontal cortex of mouse and postmortem cognitively intact elderly human brains was evaluated using flow-cytometry and western blot analyses. Binding of labeled, pre-formed Aβ and tau oligomers onto mouse primary neurons was assessed using immunofluorescence assay. The synaptic dysfunction was measured by fluorescence analysis of single-synapse long-term potentiation (FASS-LTP) assay. Results. We demonstrated that higher TauO concentrations effectively outcompete AβO and become the prevailing synaptic-associated species. Conversely, high concentrations of AβO facilitate synaptic TauO recruitment. Immunofluorescence analyses of mouse primary cortical neurons confirmed differential synaptic binding dynamics of AβO and TauO. Moreover, in vivo experiments using old 3xTgAD mice ICV injected with either AβO or TauO fully supported these findings. Consistent with these observations, FASS-LTP analyses demonstrated that TauO-induced suppression of chemical LTP was exacerbated by AβO. Finally, predigestion with proteinase K abolished the ability of TauO to compete off AβO without affecting the ability of high AβO levels to increase synaptic TauO recruitment. Thus, unlike AβO, TauO effects on synaptosomes are hampered by the absence of protein substrate in the membrane.Conclusions. These results introduce the concept that TauO become the main synaptototoxic species at late AD, thus supporting the hypothesis that TauO may be the most effective therapeutic target for clinically manifest AD.

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