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Spectroscopic Methods
Published in Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus, Environmental Chemical Analysis, 2018
Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus
Emission by excited atoms in the vapor state is measured in atomic emission spectroscopy, used most often for the determination of metals. In molecular fluorescence molecules are excited by UV radiation and emit at longer wavelengths. In chemiluminescence measurements, emission is stimulated by a chemical reaction.
Analytical Chemistry
Published in W. M. Haynes, David R. Lide, Thomas J. Bruno, CRC Handbook of Chemistry and Physics, 2016
W. M. Haynes, David R. Lide, Thomas J. Bruno
radiation by molecules that undergo a change in polarizability during the vibration. This is in contrast to infrared spectrophotometry, in which a change in the dipole moment occurs during the vibration. When radiation (typically light from a laser in the visible, near-infrared, or near-ultraviolet range) is scattered, a small fraction of the scattered radiation is observed to have a different frequency (the Raman effect). The variations of Raman spectroscopy are used to locate functional groups or chemical bonds in molecules. There are several variations in the approach to Raman spectroscopy. In resonance Raman spectroscopy, the excitation wavelength is matched to an electronic transition of the molecule, enhancing the vibrational modes. In coherent antiStokes Raman spectroscopy (CARS), two laser beams are used to generate a coherent anti-Stokes frequency beam. In surfaceenhanced Raman spectroscopy (SERS), surface plasmons (a quantum of plasma oscillation) on a silver or gold colloid on a surface (such as a mirror) are excited by the laser, resulting in an increase in the electric fields surrounding the metal. Atomic Absorption Spectroscopy (AAS) and Atomic Emission Spectroscopy (AES): Two related spectroscopic methods applied primarily to the analysis of inorganic compounds. Atomic absorption procedures use the absorption of optical radiation (light) by free atoms in the gaseous state. The light can be produced by a hollow cathode lamp, an electrodeless discharge lamp, or a deuterium lamp. The light is absorbed by the analyte during an electronic transition, the wavelength of which corresponds to only one element in the analyte, and the width of an absorption line is of the order of only a few picometers. This method can be used for the quantitative determination (on the basis of a calibration curve) of approximately 70 different elements in solution or directly in solid samples. Atomic emission spectroscopy (AES) uses the light emitted by a vaporized sample in a flame, plasma, arc, spark, or laser, at a particular wavelength, to determine the atomic spectrum (for determination of the elemental composition) and to determine the quantity of an element in a sample. The wavelength of the atomic spectral line gives the identity of the element while the intensity of the emitted light is proportional to the number of atoms of the element. No single source, as described above, is optimal for a given sample, and it is the choice of source that distinguishes the various techniques.
Development of an Activity Transport Model and In Situ Measurements on Deposited Radionuclides in the Primary Coolant Pipelines of the Chinshan Nuclear Power Plant
Published in Nuclear Science and Engineering, 2023
Yu-Hung Shih, Mei-Ya Wang, Tsuey-Lin Tsai, Tsung-Kuang Yeh
There are three feedwater sampling ports at Chinshan-1, as indicated in Fig. 1, and the sampling system operating at 240°C uses stainless steels as the structural materials, the same as those in the coolant piping and components. The technology of integrated filtration with cellulose particulate filters of 47 mm in diameter and 0.45 μm in pore size is adopted. Insoluble corrosion products are generally collected from the 1000 to 2000 L of water that are drawn from the feedwater sampling ports. Prior to passing through the filters, the feedwater would be cooled down and depressurized. The scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) techniques are used for morphology and phase analyses on the corrosion products, respectively. The filtered samples are dried at 120°C and dissolved in an HNO3 and HCl (1:1) mixed solution. An elemental analysis is then performed with inductively coupled plasma-atomic emission spectroscopy (ICP-AES).
A novel magnetic starch nanocomposite as a green heterogeneous support for immobilization of Cu nanoparticles and selective catalytic application in eco-friendly media
Published in Inorganic and Nano-Metal Chemistry, 2021
Atefeh Nasiri, Mohammad A. Khalilzadeh, Daryoush Zareyee
Industrial applications of heterogeneous catalyst related strongly to the stability and recyclability as application parameters.[88,89] The reusability of the catalyst was studied in the reduction of various dyes with NaBH4 and the oxidation of benzyl alcohol to benzaldehydes. At the final step of the reaction, the catalyst was collected magnetically from the mixture and washed several times with ethanol and water which reused for five successive runs later after drying with no significant loss of catalytic activity with a conversion efficiency of about 100%, confirming the stability and high recyclability of [Cu NPs@Fe3O4-nanostarch]. The SEM and TEM images of of [Cu NPs@Fe3O4-nanostarch] after the reaction was not different in shape and size (Figure 13 and Figure 14). Similarly, EDS analysis indicates that the chemical composition of the reused catalyst remained almost unchanged. Afterward, the leaching of metal from the [Cu NPs@Fe3O4-nanostarch] magnetic nanocatalyst was checked. Following the separation, the filtrate was tested by the ICP-AES (Inductively Coupled Plasma Atomic Emission Spectroscopy) technique. The results showed that only a minimal amount (less than 1%) of Cu metal was leached into the solution after five cycles.
Geochemical, mineralogical and macroscopic facies of the Fongo-Tongo bauxite deposit western Cameroon
Published in Applied Earth Science, 2021
Franck Wilfried Nguimatsia Dongmo, Rose Yongue Fouateu, Roger Firmin Donald Ntouala, Yanick Brice Lemdjou, Dongmo Chirstophe Ledoux, Anthony Temidayo Bolarinwa
Geological mapping and systematic sampling of bauxite was carried out in the Fongo-Tongo area (Figure 6). The representative samples selected were pulverised and subjected to mineralogical and geochemical analyses. Major oxides, trace and rare-earth elements (REE) composition were determined at the ALS Chemex laboratories, South Africa. The bauxite major oxides composition was determined by weighing 0.2 g of the powdered bauxite sample into which a solution of 0.9 g lithium metaborate (LiBO2) and lithium tetraborate (Li2B4O7) was added, homogenised and melted in an oven at 1000°C. The product obtained was cooled and dissolved respectively in 100 ml of 4% and 2% nitric and hydrochloric acid. This solution was then analysed using the inductively coupled plasma-atomic emission spectroscopy (ICP-AES).