Search results for "Spectroscopy"
showing 10 items of 10293 documents
A Colorimetric Membrane-Based Sensor with Improved Selectivity towards Amphetamine
2021
Due to their simplicity, speed and low cost, chemical spot tests are increasingly demanded for the presumptive identification of illicit drugs in a variety of contexts such as point-of-care assistance or prosecution of drug trafficking. However, most of the colorimetric reactions used in these tests are, at best, drug class selective. Therefore, the development of tests based on chemical reactions with improved discrimination power is of great interest. In this work, we propose a new colorimetric assay for amphetamine (AMP) based on its reaction with solutions of alkaline gold bromide to form an insoluble yellow–orange derivative. The resulting suspensions are then filtered onto nylon membr…
The Effectiveness of Vitamin E Treatment in Alzheimer’s Disease
2019
Vitamin E was proposed as treatment for Alzheimer’s disease many years ago. However, the effectiveness of the drug is not clear. Vitamin E is an antioxidant and neuroprotector and it has anti-inflammatory and hypocholesterolemic properties, driving to its importance for brain health. Moreover, the levels of vitamin E in Alzheimer’s disease patients are lower than in non-demented controls. Thus, vitamin E could be a good candidate to have beneficial effects against Alzheimer’s. However, evidence is consistent with a limited effectiveness of vitamin E in slowing progression of dementia; the information is mixed and inconclusive. The question is why does vitamin E fail to tre…
Multi frequency phase fluorimetry (MFPF) for oxygen partial pressure measurement: ex vivo validation by polarographic clark-type electrode.
2013
BACKGROUND: Measurement of partial pressure of oxygen (PO2) at high temporal resolution remains a technological challenge. This study introduces a novel PO2 sensing technology based on Multi-Frequency Phase Fluorimetry (MFPF). The aim was to validate MFPF against polarographic Clark-type electrode (CTE) PO2 measurements. METHODOLOGY/PRINCIPAL FINDINGS: MFPF technology was first investigated in N = 8 anaesthetised pigs at FIO2 of 0.21, 0.4, 0.6, 0.8 and 1.0. At each FIO2 level, blood samples were withdrawn and PO2 was measured in vitro with MFPF using two FOXY-AL300 probes immediately followed by CTE measurement. Secondly, MFPF-PO2 readings were compared to CTE in an artificial circulatory s…
Advances in the analysis of legal and illegal drugs in the aquatic environment
2013
We review the current methods developed for the analysis of legal and illegal drugs (LIDs) and their metabolites in environmental samples. We discuss the advantages and the pitfalls of multi-class methods with emphasis on new strategies for sample preparation and recent technical developments. Finally, we present the applicability of these methods to the analysis of LIDs in protected environmental areas.
Multi-residue determination of 47 organic compounds in water, soil, sediment and fish—Turia River as case study
2017
A sensitive and reliable method based on solid-liquid extraction (SLE) using McIlvaine-Na2EDTA buffer (pH = 4.5)-methanol and solid-phase extraction (SPE) clean up prior to ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS) was applied to determine 47 organic contaminants in fish, soil and sediments. The SPE procedure to clean-up the extracts was also used as extraction method to determine these compounds in water. Recoveries ranged from 38 to 104% for all matrices with RSDs 50% for 36 compounds in front of 9, matrix effect < 20% for 31 compounds against 21, and LOQs <25 ng g−1 for 38 compounds against 22) indicates that the proposed method is mor…
Intramolecular charge transfer and dual fluorescence of 4-(dimethylamino)benzonitrile: ultrafast branching followed by a two-fold decay mechanism.
2011
International audience; In this contribution we present new experimental and theoretical results for the intramolecular charge transfer (ICT) reaction underlying the dual fluorescence of 4-(dimethylamino) benzonitrile ( DMABN), which indicate that the fully twisted ICT (TICT) state is responsible for the time-resolved transient absorption spectrum while a distinct partially twisted ICT (pTICT) structure is suggested for the fluorescent ICT state.
High resolution CARS spectrum and analysis of the v1bandQ-branch of carbon dioxide
1988
High resolution coherent anti-Stokes Raman spectroscopy (CARS) has been applied to the study of the Q-branch of the fundamental vibrational v 1 band of CO2 in the Fermi resonance region near 1285·5 cm-1. Thanks to the use of high spectral quality (linewidth = 6 MHz) injection-locked flashlamp-pumped dye lasers, it was possible to resolve this band for the first time. The spectrum was recorded at a pressure of 5 kPa (37·5 Torr) at room temperature. We measured the line positions and collisional widths for the transitions with J values from 8 to 38. Our experimental line positions are in excellent agreement with those derived from molecular constants given on the literature. The observed line…
Spectroscopic properties of pure and Coumarin 153-doped thin films of sol-gel silica xerogels
1999
Abstract Thin-films doped with Coumarin 153, an important laser dye, have been prepared by the sol-gel method. Spectroscopic properties of the entrapped dye are studied by electronic absorption, diffuse reflectance, electronic excitation, emission and time-resolved emission techniques. The obtained results indicate that the entrapment of the dye results in formation of molecular aggregates having absorption and emission characteristics different from those of the monomeric dye. The blue matrix emission band (at approx. 450 nm) is relatively short-lived while the red band (at approx. 700 nm) displays a very long lifetime. Electronic excitation spectra of the sol-gel thin-films suggest that t…
An efficient excitation scheme for resonance ionization of tin in a laser ion source
1992
An efficient three-colour, three-step resonant excitation/ionization scheme has been found for tin that leads from the 5p23P2 level of the ground-state multiplet via two excited atomic levels (λ1 = 317.51 nm and λ2 = 811.40 nm) to an autoionizing state 9s3P2(λ3 = 823.49 nm) at 59375.9 cm−1. This excitation path permits the saturation of all transitions with the limited power available from a copper vapour laser pumped dye laser system (Esat ≈ 1.5 mJcm2 for λ3). The high repetition rate of such a laser system is essential for a highly efficient laser ion source.
The ground electronic state of KCs studied by Fourier transform spectroscopy
2008
We present here the first analysis of laser induced fluorescence (LIF) of the KCs molecule obtaining highly accurate data and perform a direct potential construction for the X (1)Sigma(+) ground state in a wide range of internuclear distances. KCs molecules were produced by heating a mixture of K and Cs metals in a heat pipe at a temperature of about 270 degrees C. KCs fluorescence was induced by different laser sources: the 454.5, 457.9, 465.8, and 472.7 nm lines of an Ar(+) laser, a dye laser with Rhodamine 6G dye (excitation at around 16 870 cm(-1)), and 850 and 980 nm diode lasers (11 500-11 900 and 10 200-10 450 cm(-1) tuning ranges, respectively). The LIF to the ground state was recor…