Infrared radiation spectrophotometry

The selective absorption of ultraviolet, visible and infrared radiation by molecules is explained in a descriptive manner that stresses how the noncontinuous energy requirements of chemical substances can only be satisfied by photons that have energy values equivalent to that of the differences in energy levels of the molecule in question. The meaning and quantitative significance of Beer s Law is briefly discussed. The components of a simple spectrophotometer are illustrated, accompanied by a demonstration of the operation of a spectrophotometer in the laboratory. Actual applications of the techniques of spectrophotometry are described during the presentation of relevent topics, for example, in drug identification. 

Infrared spectrophotometry is a powerful tool for identifying pure organic and inorganic compounds because, with the exception of a few homonuclear molecules such as O2, N2, and CU, all molecular species absorb infrared radiation. In addition, with the exception of chiral molecules in the crystalline state, each molecular species has a unique infrared absorption spectrum. Thus, an exact match between the spectrum of a compound of known structure and the spectrum of an analyte unambiguously identifies the analyte. 

Infrared (or I.) spectrophotometry - spek-tro-fo- ta-mo-tor n. An analytical instrumental technique based on selective absorption of infrared radiation by organic and inorganic materials, which helps identify them. An example of an infrared spectrum of toluene is shown. Stuart BH (2004) Infrared spectroscopy. John Wiley and Sons, New York. 

PHOTOMETRIC ANALYSIS. Chemical analysis by means of absorption or emission of radiation, primarily in the near UV, visible, and infrared portions of the electromagnetic spectrum. It includes such techniques as spectrophotometry, spectrochemical analysis, Raman spectroscopy, colorimetry, and fluorescence measurements. 

Infrared Spectrophotometry (IR). Atoms are in constant motion within molecules, and associated with these motions are molecular energy levels that correspond to the energies of quanta of IR radiation. These motions can be resolved into rotation of the whole molecule in space and into motions corresponding to the vibration of atoms with... 

Nowadays, spectrophotometry is regarded as an instrumental technique, based on the measurement of the absorption of electromagnetic radiation in the ultraviolet (UV, 200-380 nm), visible (VIS, 380-780 nm), and near infrared region. Inorganic analysis uses UV-VIS spectrophotometry. The UV region is used mostly in the analysis of organic compounds. Irrespective of their usefulness in quantitative analysis, spectrophotometric methods have also been utilized in fundamental studies. They are applied, for example, in the determination of the composition of chemical compounds, dissociation constants of acids and bases, or stability constants of complex compounds. 

Blinn and Gunther (1963) have reviewed the use of infrared and ultraviolet spectrophotometry in the field of pesticide residue chemistry. Spectrophotometric measurements offer several unique advantages to the analytical chemist the radiation which is absorbed is characteristic of the material doing the absorbing the degree of absorption of radiation is directly proportional to the concentration of the material in solution and spectrophotometric methods are usually essentially nondestructive to the absorbing material and therefore allow recovery for further scrutiny by other types of instrumentation when applicable. 

The spectrophotometry is a technique based on Lambert-Beer law, which is the math support for measurement of the absorption of radiation by solid, liquid, or gaseous samples. The absorption can occur in the ultraviolet, visible, and infrared regions of the electromagnetic spectrum [21]. 

Infrared (IR) spectrophotometric analysis is based on the fact that the characteristic wavelengths at which radiation is absorbed or emitted by minerals in the IR region can be related to the inter-atomic vibrations in the molecules or crysals [72]. No two minerals give exactly the same pattern when transmission of radiation is plotted against wavelength. By combining quantitative and qualitative capabilities, IR spectrophotometry provides a powerful tool for crystal chemical studies. Cerussite (PbC03) was one of several carbonates studied by Alder and Kerr [1]. 

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