Introduction on Spectroscopy and Absorption Spectroscopy
Spectroscopy is the study of how matter interacts with electromagnetic radiation due to its frequency or wavelength of radiation. It originated from researchers’ interest in wavelength on the absorption of light by gas, something that can be seen when a prism disperses light acoustic and matter waves can also be as gravitational and radioactive forms of waves. It is, therefore, the study of matter in its relationship with light or electromagnetic radiation.
Spectroscopy has played a significant role in studying the composition and structure of matter, both physical and electronic structures to be investigated at the macro, molecular and atomic structures over large distances, whose first application was in medical imaging, tissue analysis in biomedical spectroscopy. It is mainly used in qualitative and quantitative studies of organic and inorganic compounds and in the elucidation of molecular structure.
On the other hand, absorption spectroscopy is the technique used in the measurement of the absorption of radiation as a function of its wavelength or frequency due to its interaction with matter. This absorption occurs across an electromagnetic spectrum, and its intensity depends on its variation or frequency. It is mainly applied in analytical chemistry in determining the presence of a particular substance in a sample. The major absorption spectroscopy types include IR for infrared, UV-vis for ultraviolet-visible electromagnetic radiation, X-ray absorption, and microwave absorption (Khalili, 2020).
Explain and Define UV-Visible, IR and Florescence Spectroscopy
Ultraviolet-visible of UV-Vis is the absorption of ultraviolet light in the adjacent and visible range, and this reflectance or absorption affects the perception of the colour of the chemical used. This is due to the electronic transitions that the molecules, atoms, and the electromagnetic spectrum undergoes.
This is contemporary to the atoms, molecules, and electromagnetic spectrum transition from an excited to ground state in fluorescent spectroscopy. Molecules containing n-electrons, bonding and nonbonding, can absorb visible light, exciting them to a higher antibonding molecular orbital. The lower the energy required to excite the electrons, the longer the range’s wavelength can be absorbed. Vibrational or infrared spectroscopy measures the relationship between functional groups or chemical substances and is measured using an infrared spectrometer. How the molecules absorb the frequencies characterizes their structure (Zhang et al., 2019). A graph with light absorbance on the Y-axis and wavelength or frequency on the X-axis. This energy is affected by the vibronic coupling, the atom’s mass, and molecular potential energy’s shape.
Fluorescence spectroscopy analyses the use of light to excite the electrons in a compound and is concerned with vibrational and electronic states. When the molecules absorb a photon, they get excited from a ground electronic to a vibrational state. The molecule can drop through the various vibrational levels, thus emitting a photon that is used to analyse the frequencies of the light emitted and its relative intensity (Khalili, 2020).
Discuss the Difference Between These Three Methods, Principles and Instrumentation
With the same range of wavelength, causing different phenomena in UV-visible spectroscopy, the absorption of light by a molecule is measured as a function of its wavelength. The absorption of a photon by a molecule causes it to transition from the grounded to excited state; thus, the electron is promoted from a low-energy Unoccupied Molecular Orbital (LUMO) to a Higher-energy Occupied Molecular Orbital (HOMO), and the smaller the energy required to make this transition, the larger the wavelength. Both fluorescence and ultraviolet-visible spectrum analysis are used to detect and quantify a sample’s components (Zhang et al., 2019). Florence analyses can detect smaller volumes of a substance in a sample due to its higher sensitivity, as it can detect the slightest changes in the state’s change, thus being more sensitive than infrared and ultraviolet-visible light.
Florescence has a more dynamic range than the ultraviolet-visible spectrum. The amount can measure the measurement of the absorbance of ultraviolet spectroscopy without dilution. Florescence has more accuracy in detecting contaminations in various samples as it is able the measurement absorbance. In terms of instrumentation, there are two types of instruments: the filter fluorometer and spectrofluorometers used to isolate the incidence of the florescent from incident light. Fluorescence is complementary to ultraviolent absorbance; thus, the same wavelength causes the molecule’s excitement from the grounded to an excited state in a shorter time ultra-violent spectroscopy, something that allows its application of aqueous solutions at low concentrations. It is also more quantitative than fluorescence and infrared spectroscopy (Khalili, 2020).
Application (One Application of the Technique)
Infrared spectroscopy is a reliable and straightforward technique applied in organic and inorganic chemistry in quality control, monitoring equipment and dynamic measurement. It is also used to measure the concentration of Carbon (IV) Oxide and other greenhouse gases in the air. In civil and criminal forensic analysis, infrared is used to identify polymer degradation, and the most popular application is the detection of the amount of alcohol consumed by a person to detect people driving under the influence of alcohol. It is also used to identify the pigments in paint to detect a piece of art (Khalili, 2020).
On the other hand, Florence is used in chemical, biochemical, and medical research to analyze various organic compounds. For example, in the detection of a benign skin tumor. Atomic fluorescent spectroscopy is used to measure a given compound in water or air, for example, heavy metals like mercury. It can be absorbed at the microscopic level using microfluorimetry. In water research, it is used to detect organic pollutants, thus monitoring the quality of water. The integration of machine learning into fluorescence spectroscopy has the detection of bacterial contaminants in water. It can also be used to redirect photons, for example, in the fluorescent solar collection (Andersen et al., 2018).
Ultraviolet spectroscopy is used in analytical chemistry to determine various analytes like highly-coagulated organic compounds and in biological macromolecules transitional metal ions. It can also be used in the detection of HPLC, thus measuring the presence of an analyte. It is also applied in measuring the optical property and thickness of thin water films and measuring reluctance. In quantitative analysis, ultraviolet spectroscopy is used to determine whether a compound can absorb ultraviolet light. Kinetic reactions are also studied unit ultraviolet spectroscopy by passing ultraviolet light through a reaction, thus causing absorbance changes (Andersen et al., 2018).
Andersen, P. V., Wold, J. P., Gjerlaug-Enger, E., & Veiseth-Kent, E. (2018). Predicting post-mortem meat quality in porcine longissimus lumborum using Raman, near infrared and fluorescence spectroscopy. Meat science, 145, 94-100.
Khalili, H. (2020). Lecture Week 7 Molecular Fluorescence Spectroscopy. Presentation, BS4103 Fundamentals of Analytical Chemistry.
Zhang, B., Huang, Q. R., Jiang, S., Chen, L. W., Hsu, P. J., Wang, C., … & Kuo, J. L. (2019). Infrared spectra of neutral dimethylamine clusters: An infrared-vacuum ultraviolet spectroscopic and anharmonic vibrational calculation study. The Journal of chemical physics, 150(6), 064317.