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Ultraviolet Electromagnetic Radiation
Published in Dave Birtalan, William Nunley, Optoelectronics, 2018
The medical analytical instrument market also utilizes UV light sources in fluorescence spectroscopy and ultraviolet-visible spectroscopy. Fluorescence spectroscopy is a type of electromagnetic spectroscopy that analyzes the fluorescence emitted from a sample being irradiated and evaluated. The light source is generally UV to excite the electrons in the specimen to emit light of a lower energy level, usually in the visible spectrum. In fluorescence spectroscopy, the sample is excited, by absorbing the higher-energy UV light, causing the sample to move from its ground electronic state to one of the various vibrational states in the excited electronic state. Analysis of the emission spectrum will permit the identification of the substance (chemical compound, food processing, cancer tumor, etc.). Fluorescence spectroscopy is also used in forensics and chemical research fields. Ultraviolet-visible spectroscopy (UV/VIS) uses multiple wavelengths of light in the visible, ultraviolet, and near-infrared ranges. The absorbance of light in a solution is directly proportional to the solution’s concentration (Beer–Lambert law).
Spectroscopic Methods
Published in Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus, Environmental Chemical Analysis, 2018
Somenath Mitra, Pradyot Patnaik, Barbara B. Kebbekus
The excitation energy can be supplied by raising the sample to a high temperature, by irradiating it with electromagnetic radiation, or by exposing it to an electrical arc or spark. The energy emitted corresponds to the energy difference between the initial and final states. Radiation of a specific wavelength (Equation 3.1) is generated. An emission spectrum is a plot of the intensity of the emitted radiation as a function of wavelength. The wavelength of this radiation contains information about the type of atom or molecule undergoing the energy transition, and so provides qualitative identification. The intensity of emission is proportional to the number of atoms and molecules undergoing the transition and provides quantitative information.
Analytical Chemistry for Industrial Hygienists
Published in Martin B., S.Z., of Industrial Hygiene, 2018
Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) is another analytical technique used for the determination of metals. This method is used when multi-element determinations are desired. The principle is the reverse of atomic absorption spectroscopy. Radiation is emitted at specific wavelengths by excited atoms corresponding to the energy released for an electronic transition from the excited state to ground state. With a focus on specific wavelengths, up to 30 elements can be measured in a single sample. ICP can be used in the sequential (one metal analyzed after another) or in the simultaneous (several metals analyzed simultaneously) detection mode. In this method, samples must also be solubilized. The instrument measures the characteristic emission spectra by optical spectroscopy. Samples are nebulized and the resulting aerosol is transported to the plasma torch produced by a radio frequency-induced coupled plasma with a temperature range of 5000 to 10,000°C. The emission spectra produced are element specific. The spectra are dispersed by a grating spectrometer, and the intensities of the emission lines are monitored by photosensitive devices. The radiation is in the ultraviolet, visible, and near infrared regions of the electromagnetic spectrum. Most applications of ICP operate in the 190–800 nm region.
An Analysis of Sediment Quality from the Perspective of Land Use in the Catchment and Pond Management
Published in Soil and Sediment Contamination: An International Journal, 2020
Štěpán Marval, Tomáš Hejduk, Antonín Zajíček
The samples used to measure the content of risk elements were prepared by aqua regia extraction and the measurement itself was carried out with the Agilent 5110 ICP-OES Instrument, which is based on detecting photons generated in the transition of valence electrons from higher to lower energy levels. The radiation emitted by atoms in an excited state is measured. Samples in a liquid state are inserted into a cloud chamber and subsequently into plasma, where atomization, ionization and excitation of the elements takes place. A detector then indicates the radiation emitted by atoms and ions in an excited state. The emission spectrum is a line spectrum, where the position of a line indicates the qualitative composition of the sample, whereas the intensity of the line indicates the quantitative composition of the sample.
Coherence-enhanced diffusion filtering applied to partially-ordered fluids
Published in Molecular Physics, 2020
Perry W. Ellis, Jyothishraj Nambisan, Alberto Fernandez-Nieves
Fluorescence is an inelastic process where a material absorbs and then re-emits light; the initial absorption excites a singlet state in the material which then decays via photon emission [17]. The absorption and emission are characterised by their respective spectra, with the peak in the emission spectrum occurring at a longer wavelength than the peak in the absorption spectrum. As a historical aside, the realisation that this process consists of both absorption and emission of light is attributed to Stokes, as is the name ‘fluorescence’ itself [18,19]. This is the reason that the difference in the peak of the excitation and emission spectra for a given fluorophore is known as the ‘Stokes shift’ [17]. A standard epifluoresence setup takes advantage of this with a dichroic mirror and pair of band-pass filters centred on the peaks in the excitation and emission spectra, with no overlap in the transmitted wavelengths of the filters. Consequently, the light passed by these filters is referred to as the excitation light and emission light, respectively. The dichroic mirror typically reflects the excitation light and passes the emission light. Thus, the sample can be illuminated by the excitation light, exciting the fluorophores in the sample, with only the emission light collected on the detector, typically a CCD camera. Imaging the active nematic with such a setup results in signal coming from only the fluorescently labelled microtubules, clearly revealing the nematic structure, as shown in the example image in Figure 1(D). This is a wide-field technique, meaning that even though only a specific plane in the sample is in focus, light from out of focus planes can still reach the detector.
Quantification of anhydrous ethanol and detection of adulterants in commercial Brazilian gasoline by Raman spectroscopy
Published in Instrumentation Science & Technology, 2019
Andressa Cristina de Mattos Bezerra, Danieli de Oliveira Silva, Gustavo Henrique Machado de Matos, Josuel Pereira dos Santos, Claudio Neves Borges, Landulfo Silveira, Marcos Tadeu Tavares Pacheco
Raman spectroscopy is based on the inelastic scattering of the incident light through the molecule, involving the changes in the polarizability of the irradiated molecule and the emission of a photon, carrying information of the energy vibrational bonds of the molecule. The emission spectrum is characterized by bands at frequencies referred to the energy levels of the molecule. Since the vibrational energy levels are unique to each molecule, the Raman spectrum provides a fingerprint of a particular molecule. The spectra may provide information on molecular structure, dynamics, and environment.[14]