Chemistry
Infrared Spectroscopy
Infrared spectroscopy is a technique used to analyze the chemical composition of a substance by measuring the absorption of infrared radiation. It provides information about the functional groups present in a molecule, allowing for identification and characterization of organic compounds. By measuring the energy absorbed by different chemical bonds, infrared spectroscopy can be used to determine molecular structure and composition.
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12 Key excerpts on "Infrared Spectroscopy"
eBook - ePub- Simonpietro Agnello(Author)
- 2021(Publication Date)
- Wiley(Publisher)
5 Infrared Absorption Spectroscopy Tiziana Fiore and Claudia Pellerito Department of Physics and Chemistry – Emilio Segrè, University of Palermo, Palermo, Italy 5.1 Fundamentals Infrared (IR) absorption spectroscopy is one of the most important analytical techniques available to study different kinds of samples including solids, semisolids, powders, polymers, biological materials, films, liquids, solutions, and gases. One of the great advantages is that IR spectroscopy is a nondestructive technique commonly applied to characterize the chemical structure and identify the chemical bonds in unknown materials. Qualitative identification of organic and inorganic compounds is a primary purpose of IR spectroscopy, even if IR absorption can also be used to provide quantitative measurements of compounds. The infrared range of the electromagnetic spectrum covers the wavelength region from 0.7 μm to 1 mm, which conforms to the wavenumber range 14,285–10 cm −1. The entire IR region can be divided into the near IR region (0.7–2.5 μm, 14,285–4000 cm −1), the mid‐IR region (2.5–50 μm, 4000–200 cm −1), and the far‐IR region (50–1000 μm, 200–10 cm −1). Chemists most often work in the mid‐IR region where many molecules have strong absorbances and specific vibrational frequencies corresponding to discrete vibrational energy levels, which characterize the infrared spectrum of each compound. IR spectroscopy became widely used after the development of dispersive infrared spectrometers in the 1940s [1]. The basic components of a dispersive IR spectrometer included a radiation source, monochromator, and detector. This type of instrument helped to spread the use of IR spectroscopy as a common analytical technique for organic compounds characterization in basic and industrial research
eBook - PDFInfrared Spectroscopy
Life and Biomedical Sciences
- Theophile Theophanides(Author)
- 2012(Publication Date)
- IntechOpen(Publisher)
16 FT-IR Spectroscopy in Medicine Vasiliki Dritsa National Technical University of Athens, NTUA Greece 1. Introduction Infrared Spectroscopy has been widely applied for the characterisation of various substances. Due to its sensitivity to the chemical information and architecture of the molecule, Infrared Spectroscopy can play an important role in new applications such as in the life-science field and not only in the traditional fields of physics and chemistry. Spectroscopic techniques are simple, reproducible, non-destructive without particular sample preparation. As a result, they provide information for the functional groups, bonds and molecular structure. Herschel discovered the existence of infrared radiation when he tried to measure the heat produced by separate colors of a rainbow spectrum in 1800. He noted that the highest temperature fell beyond the red end of the spectrum, implying the existence of invisible light beyond the red. Herschel termed this light calorifi c rays . Infrared spectra originate on the vibrational motions of atoms in chemical bonds within molecules. When a beam of light containing the IR radiation band is passed through a sample, light energy from the photons is absorbed by the chemical bonds and excites the vibrational motions. As a molecule absorbs radiation at a specific frequency, it produces a band in the infrared spectrum at the corresponding wavenumber. The approximate position of an infrared absorption band is determined by the vibrating masses and the chemical bonds (single, double, triple). Τ he exact position of the band depends also on electron withdrawing or donating effects of the intra- and intermolecular environment and coupling with other vibrations. The strength of absorption increases with increasing polarity of the vibrating atoms. The modes of vibration in a molecule that can absorb infrared radiation are many and increase with increasing complexity of the molecule.
- Kenneth Williamson, Katherine Masters(Authors)
- 2016(Publication Date)
- Cengage Learning EMEA(Publisher)
221 The types and molecular environment of functional groups in organic molecules can be identified by infrared (IR) spectroscopy. Like nuclear magnetic resonance (NMR) and ultraviolet (UV) spectroscopy, IR spectroscopy is nondestructive. More-over, the small quantity of sample needed, the speed with which a spectrum can be obtained, the relatively low cost of the spectrometer, and the wide applicability of the method combine to make IR spectroscopy one of the most common structural elucidation tools used by organic chemists. IR radiation consists of wavelengths that are longer than those of visible light. It is detected not with the eyes but by a feeling of warmth on the skin. When ab-sorbed by molecules, radiation of these wavelengths (typically 2.5–5 μ m) increases the amplitude of vibrations of the chemical bonds joining atoms. IR spectra are measured in units of frequency or wavelength. The wavelength is measured in micrometers 1 or microns, μ (1 μ m 5 1 3 10 2 6 m). The positions of absorption bands are measured in frequency units called wavenumbers ν , which are expressed in reciprocal centimeters, cm 2 1 , corresponding to the number of cy-cles of the wave in each centimeter. Infrared Spectroscopy CHAPTER 11 PRE-LAB EXERCISE: When an infrared (IR) spectrum is run, it is possible that the chart paper is not properly placed or that the spectrometer is not mechanically adjusted. Describe how you could calibrate an IR spectrum. Examine the scale carefully. Unlike UV and NMR spectra, IR spectra are inverted, with the strongest ab-sorptions at the bottom (called “peaks” although they look like valleys), and are not always presented on the same horizontal scale. Some spectrometers record the spectra on an ordinate linear in microns, but this compresses the low-wavelength region.
eBook - PDF- J.H. Richardson(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
C H A P T E R 9 Infrared Spectrometry A. Lee Smith Dow Coming Corporation Midland, Michigan Introduction 255 Scope of the Technique 255 Limitations 256 Uses in Materials Analysis 256 Theory 257 1.1 The Vibrations of Molecules 257 1.2 Normal Modes 258 1.3 Group Frequencies 259 1.4 Interaction between Radiation and Molecules 259 Instrumentation 259 2.1 Dispersive Spectrometers 260 2.2 Fourier Transform Spectrometers 266 Sampling 271 3.1 Effect of Sample State 271 3.2 Sample Requirements 272 3.3 Techniques for Solid and Liquid Samples 272 3.4 Gases and Vapors 284 Applications 284 4.1 Qualitative Analysis 284 4.2 Quantitative Analysis 288 4.3 Applications to Materials Analysis 292 References 297 Introduction SCOPE OF THE TECHNIQUE Of the many disciplines in chemistry, none has changed more strikingly in the past 30 years than has analytical chemistry. From an essentially chemical approach which used only simple physical measurements, a pre-255 1 2 3 4 256 A. LEE SMITH dominantly physical approach has evolved which often uses chemical re-actions only to prepare the specimen for physical analysis. Spectroscopy in one form or another is involved in many of the physical analysis tech-niques, and of the spectroscopic methods, Infrared Spectroscopy is unsur-passed in its application to a wide variety of problems and materials, and in the information content of the resulting spectrum. It is a test that is rapid, nondestructive of the sample, highly definitive, and useful for both qualitative and quantitative analyses. Infrared Spectroscopy has for years been the method of choice for quali-tative analysis of organic materials, and it has wide application to inorganic substances as well. The infrared spectrum of a material has aptly been called its fingerprint—a unique property of that material and of its physical state.
eBook - PDF- John H. Lawrence, Cornelius A. Tobias, John H. Lawrence, Cornelius A. Tobias(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
Infrared Spectrometry BY NORMAN K . FREEMAN Donner Laboratory of Biophysics and Medical Physics, University of California, Berkeley, California Page I. Introduction 167 II. Interpretation of Infrared Spectra 172 1. General Remarks, and the Use of Structural Correlations 172 2. Other Aids to Interpretation 178 3. Cataloging of Spectra 180 III. Instrumentation 182 1. Commercial Spectrometers 182 2. Special Devices 183 3. The Far Infrared 185 4. Nondispersive Analyzers 186 IV. Infrared Microspectrometry 187 1. The Reflecting Microscope 187 2. The Silver Chloride Beam Condenser 192 V. Experimental Techniques 192 1. Sample Preparation 192 2. The Pressed Pellet Technique 193 3. Aqueous Solutions 196 4. Quantitative Analysis 198 VI. Applications in Biological Chemistry 199 1. Proteins, Polypeptides, and Amino Acids 199 2. Nucleic Acids 204 3. Lipides 205 4. Steroids 210 5. Carbohydrates 211 6. Bacteriology 212 7. Tissues 213 VII. Conclusion 215 References 217 I. I N T R O D U C T I O N Among the specialized branches of spectroscopy, the study of infra-red absorption has proven to be one of the most versatile as a tool of modern research. Its fields of application include such diverse areas as clay technology, perfumery, and the elucidation of protein structure. If one seeks the common denominator for this exceptional versatility, it is not difficult to find. It resides in the intimate relationship between infrared spectra and molecular structure. This relationship provides a 167 168 NORMAN Κ. FREEMAN foundation for potential usefulness in almost all branches of chemistry, both pure and applied, and consequently in other sciences where inter-pretations are being sought in chemical terms. In biology there are numerous manifestations of increasing emphasis on studies of the detailed structures of key participating substances in relation to their behavior in life processes.
eBook - PDFChemical Analysis
Modern Instrumentation Methods and Techniques
- Francis Rouessac, Annick Rouessac, John Towey(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
Chemical Analysis: Modern Instrumentation Methods and Techniques , Third Edition. Francis Rouessac and Annick Rouessac, translated by John Towey. © 2022 John Wiley & Sons Ltd. Published 2022 by John Wiley & Sons Ltd. Companion Website: www.wiley.com/go/Rouessac/Analysis3e Infrared and Raman Spectroscopy Chapter 10 I nfrared absorption spectroscopy is based on the study of electromagnetic radiation between 1 and 50 micrometres. This spectral range, divided into near, mid, and far infrared, is used to identify or quantify chemical compounds present in all sorts of samples. Raman spectroscopy is based on the scattering of a very small part of the light used to excite the sample. It provides comparable and additional information to that obtained from the mid or far infrared range, but the very low intensity of the Chapter 10: Infrared and Raman Spectroscopy 248 observed signals prevented the spread of this technique for a long time. These two nondestructive methods are accessible with a variety of versatile spectrometers and analysers designed to study target compounds. Many fields use these two techniques widely, ranging from industrial process analyses to field analyses as well as multipurpose laboratories. 10.1 THE ORIGIN OF LIGHT ABSORPTION IN THE INFRARED REGION In the near and the mid-infrared, the absorption of light by matter originates from the interaction between the radiation from a light source and the chemical bonds in the sample. More precisely, if the atoms situated at the two ends of a bond are animated by vibrational movement with respect to each other and are different from each other, they form an electric dipole that oscillates at a specific frequency. If such a nonsymmetrical bond is irradiated by a monochromatic light source whose frequency is the same as the dipole, then an interaction will occur with the dipole moment of the bond.
eBook - ePubProblems of Instrumental Analytical Chemistry
A Hands-On Guide
- JM Andrade-Garda, A Carlosena-Zubieta;MP Gómez-Carracedo;MA Maestro-Saavedra;MC Prieto-BlancoRM Soto-Ferreiro(Authors)
- 2017(Publication Date)
- WSPC (EUROPE)(Publisher)
CHAPTER 4
INFRARED SPECTROMETRY
José Manuel Andrade-Garda andMaría Paz Gómez-Carracedo
OBJECTIVES AND SCOPE
The objective of this chapter is to present students the very basics of the chemical interpretation of an infrared (IR) spectrum. Explanations will be restricted to typical functional groups and relatively simple structures. Also, only the medium IR region and organic molecules will be considered. Quantitation issues are commented briefly since the multivariate statistical treatment is out of the scope of this book and classical calibration will be treated deeply in the other chapters. Therefore, the chapter focuses on the basics of IR spectra interpretation, something that somehow is not considered in many textbooks in analytical chemistry.1.INTRODUCTION
1.1.Basic concepts
Infrared (IR) spectrometry (or spectrometry in the infrared region, IR) is a molecular analysis technique of paramount importance in chemistry. Not in vain it is a powerful, ubiquitous workhorse to study and ascertain the main characteristics of molecular structures. Further, and in addition to this classical application, its use has fostered in the last two decades, thanks to its combination with multivariate chemometric techniques (mainly full-spectrum regression techniques like partial least squares, PLS). This conferred on IR spectrometry an unprecedent power to quantitate one or several species of interest in the analyzed aliquots. In conjunction with nuclear magnetic resonance (NMR) and mass spectrometry (MS), it constitutes a basic tool for most studies on organic and inorganic materials performed nowadays.Frequently, references to the ‘infrared region’ assume implicitly that work is performed at the medium IR range (MIR or mid-IR, 4000–600 cm−1 ), which is considered to offer a spectral ‘fingerprint’ of a substance [1 , 2 ]. However, nowadays the near infrared range (NIR, 13300–4000 cm−1 ) has become a very powerful and popular tool. The NIR range is used to study, mainly, harmonic vibrations of the functional groups. Practical applications using the far infrared region (FIR, 400–20 cm−1 ) are still pretty scarce, although they are increasing, thanks to the so-called terahertz spectroscopy [3 ], a term which somehow supersedes the FIR one. A relevant advantage of this region is that plastics, cloth and semiconducting materials are transparent, opening up ways to in situ
eBook - PDF- Donald Pavia, Gary Lampman, George Kriz, James Vyvyan, Donald Pavia, Gary Lampman, George Kriz, James Vyvyan(Authors)
- 2014(Publication Date)
- Cengage Learning EMEA(Publisher)
Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 26 Infrared Spectroscopy 2.7 WHAT TO LOOK FOR WHEN EXAMINING INFRARED SPECTRA An infrared spectrometer determines the positions and relative sizes of all the absorptions, or peaks, in the infrared region and plots them on a piece of paper. This plot of absorption intensity versus wavenumber (or sometimes wavelength) is referred to as the infrared spectrum of the compound. Figure 2.4 shows a typical infrared spectrum, that of 3-methyl-2-butanone. The spectrum exhibits at least two strongly absorbing peaks at about 3000 and 1715 cm − 1 for the C I H and C J O stretching frequencies, respectively. The strong absorption at 1715 cm − 1 that corresponds to the carbonyl group (C J O) is quite intense. In addition to the characteristic position of absorption, the shape and intensity of this peak are also unique to the C J O bond. This is true for almost every type of absorption peak; both shape and intensity characteristics can be described, and these characteristics often enable the chemist to simply places a small amount of a liquid or solid directly on the diamond without any previous preparation. The diamond is cut and mounted at precise angles so that the incoming beam of in-frared radiation bounces back and forth off the internal surfaces of the crystal. When the beam re-flects off the surface where the sample has been applied, it penetrates the sample slightly, and the vibrational frequencies of the sample are somewhat absorbed, thereby “attenuating” the beam. The ATR accessory has revolutionized the ease of infrared spectral analysis of solids. For example, it is often unnecessary to make use of KBr pellets and Nujol mulls. The spectrum ob-tained with an ATR FT-IR is nearly identical to that obtained with an FT-IR operating in the transmittance mode.
- Prakash Saudagar, Timir Tripathi, Prakash Saudagar, Timir Tripathi(Authors)
- 2022(Publication Date)
- Academic Press(Publisher)
Chapter 6: Applications of Infrared Spectroscopy to study proteins
Riya Sahua ; Banesh Soorama ; Santanu Sasidharana ; Niharika Nagb ; Timir Tripathib , c ; Prakash Saudagaraa Department of Biotechnology, National Institute of Technology Warangal, Warangal, Indiab Molecular and Structural Biophysics Laboratory, Department of Biochemistry, North-Eastern Hill University, Shillong, Indiac Regional Director's Office, Indira Gandhi National Open University (IGNOU), Regional Center Kohima, Kohima, IndiaAbstract
Owing to its sensitivity to chemical makeup and structure, one of the most used approaches to analyze the structure of small molecules is infrared (IR) spectroscopy. In addition to its sensitivity, IR spectroscopy provides extensive data to study protein structure, biological systems, molecular and chemical processes, and mechanisms of protein misfolding, folding, and unfolding. The use of information received from the IR spectrum is not only limited to the analysis of proteins but also used to explore other biological systems such as the classification of microbes and the identification of bacterial strains. IR spectroscopy has a wide range of applications ranging from small soluble proteins to large membrane proteins. The method requires less effort, is economical, and gives high time resolution within a short span of measurement time and with a low amount of sample requirement. This article discusses the applicability of the middle region of the IR spectra for studying protein reactions utilizing reaction-driven IR difference spectroscopy.Keywords
Infrared Spectroscopy; FTIR; Protein structure; Protein function; Secondary structures1: Introduction
Owing to its sensitivity to chemical makeup and structure, one of the most used approaches to analyze the structure of small molecules is infrared (IR) spectroscopy. In addition to its sensitivity, IR spectroscopy provides extensive data to study protein structure [1 –11 ], biological systems, molecular and chemical processes [1 ,2 ,9 ,12 –31 ], and mechanisms of protein misfolding, folding, and unfolding [8 ,9 ,11 ,23 ,28 ,32 –38
eBook - ePubInstrumental Analytical Chemistry
An Introduction
- James W. Robinson, Eileen M. Skelly Frame, George M. Frame II(Authors)
- 2021(Publication Date)
- CRC Press(Publisher)
If now we were to measure the extent of absorption at the same frequency by a sample solution of unknown concentration, the results could be compared. We could determine the sample's concentration using Beer's Law. Thus, as a quantitative tool, IR spectroscopy enables us to measure the concentration of analytes in samples. The introduction and widespread use of FTIR has resulted in considerable extension of the uses of IR in analytical chemistry. With regard to wavelength assignment, speed of analysis, and sensitivity, FTIR has opened new fields of endeavor. Some of these uses are described. Typical analyses include the detection and determination of paraffins, aromatics, olefins, acetylenes, aldehydes, ketones, carboxylic acids, phenols, esters, ethers, amines, sulfur compounds, halides, and so on. From the IR spectrum, it is possible to distinguish one polymer from another, or determine the composition of mixed polymers, or identify the solvents in paints. Atmospheric pollutants can be identified while still in the atmosphere. Another interesting application is the examination of old paintings and artifacts. It is possible to identify the varnish used on the painting and the textile comprising the canvas, as well as the pigments in the paint. From this information, fake “masterpieces” can be detected. Modern paints and textiles use materials that were not available when many masterpieces were painted. The presence of modern paints or modern synthetic fabrics confirms that the painting must have been done recently. In a similar manner, real antiques can be distinguished from modern imitations. Forensic science makes use of Infrared Spectroscopy and IR microscopy, not only for paint analysis but for analysis of controlled substances. IR can be used to detect the active compounds in hallucinogenic mushrooms, for example. IR is often used to confirm the identity of controlled substances such as cocaine
eBook - ePub- Thomas J. Bruno, James W. Robinson, George M. Frame II, Eileen M. Skelly Frame(Authors)
- 2023(Publication Date)
- CRC Press(Publisher)
Standard Methods for the Examination of Water and Wastewater, 18th edn. American Public Health Association: Washington, DC, 1992.- Gremlich, H.-U.; Yan, B. (eds.)
Infrared and Raman Spectroscopy of Biological Materials. Marcel Dekker, Inc.: New York, 2001.- Griffiths, P.R.; de Haseth, J.A.
Fourier Transform Infrared Spectrometry. Chemical Analysis, Vol. 83. Wiley-Interscience: New York, 1986.- Heil, C. Rapid, multi-component analysis of soybeans by FT-NIR spectroscopy. Thermo Fisher Scientific application note, www.thermo.com , ©2010 Thermo Fisher Scientific, Madison, WI (www.thermofisher.com ).
- Herrero, A.M.; Carmona, P.; Careche, M. Raman spectroscopic study of structural changes in Hake (Merluccius merluccius L.) muscle proteins during frozen storage.
J. Agric. Food Chem., 52(8), 2147, 2004.- Hsu, C.-P.S. Infrared Spectroscopy. In Settle, F.A. (ed.),
Handbook of Instrumental Techniques for Analytical Chemistry. Prentice Hall PTR: Upper Saddle River, NJ, 1997.- Humecki, H.J. (ed.)
Practical Guide to Infrared Microspectroscopy. Practical Spectroscopy Series, Vol. 19. Marcel Dekker, Inc.: New York, 1995.- Ingle, J.D., Jr.; Crouch, S.R.
Spectrochemical Analysis. Prentice Hall, Inc.: Englewood Cliffs, NJ, 1988.- Kawai, N.; Janni, J.A. Chemical identification with a portable Raman analyzer and forensic spectral database.
Spectroscopy, 15(10), 32, 2000.- Kneipp, K.; Moskvits, M.; Kneipp, H. (eds.)
Surface-Enhanced Raman Scattering: Physics and Applications. Topics in Applied Physics, Vol. 103. Springer: New York, 2006.- Lambert, J.B.; Shurvell, H.F.; Lightner, D.; Cooks, R.G.
Introduction to Organic Spectroscopy. Macmillan Publishing Company: New York, 1987.- Lowry, S.
Using FT-IR Spectroscopy to Analyze Gemstones: Application Note 51123. Thermo Fisher Scientific: Madison, WI, 2006.- Marbach, R.; Kosehinsky, T.; Gries, F.A.; Heise, H.M. Noninvasive blood glucose assay by NIR diffuse reflectance spectroscopy of the human inner lip.
Appl. Spectrosc., 47(7), 875, 1983.- McLain, B.L.; Hedderich, H.G.; Gift, A.D.; Zhang, D.; Jallad, K.; Haber, K.S.; Ma, J.; Ben-Amotz, D. Fast chemical imaging.
Spectroscopy
- Robert M. Silverstein, Francis X. Webster, David J. Kiemle, David L. Bryce(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
The absorption band positions are identi- cal; however, the relative intensities of corresponding bands are often different. 2.5 INTERPRETATION OF SPECTRA There are no rigid rules for interpreting an IR spectrum. Certain requirements, however, must be met before an attempt is made to interpret a spectrum: 1. The spectrum must be adequately resolved and of adequate intensity. 2. The spectrum should be that of a reasonably pure compound. 3. The spectrometer should be calibrated so that the bands are observed at their proper frequencies or wavelengths. Proper calibration can be made with reliable standards, such as polystyrene film. 4. The method of sample handling must be specified. If a solvent is employed, the solvent, concentration, and the cell thickness should be indicated. 2.5 INTERPRETATION OF SPECTRA 79 A precise treatment of the vibrations of a complex molecule is not feasible; thus, the IR spectrum must be interpreted from empirical comparison of spectra and extrap- olation of studies of simpler molecules. Many questions aris- ing in the interpretation of an IR spectrum can be answered by data obtained from the mass (Chapter 1) and NMR spectra (Chapters 3 to 6). Infrared absorption of organic molecules is summa- rized in the chart of characteristic group absorptions in Appendix B. Many of the group absorptions vary over a wide range because the bands arise from complex interact- ing vibrations within the molecule. Absorption bands may, however, represent predominantly a single vibrational mode. Certain absorption bands, for example, those arising from the C⏤H, O⏤H, and C ⏤ ⏤O stretching modes, remain within fairly narrow regions of the spectrum. Important details of structure may be revealed by the exact position of an absorp- tion band within these narrow regions. Shifts in absorp- tion position and changes in band contours, accompanying changes in molecular environment, may also suggest impor- tant structural details.
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