Infrared spectroscopy solved problems

Lewis, E. N., Lee, E., and Kidder, L. H. (2004), Combining imaging and spectroscopy Solving problems with near infrared chemical imaging, Microscopy Today, 12, 8-12. 

Applied Infrared Spectroscopy Fundamentals, Techniques, and Analytical Problem-solving. By A. Lee Smith... 

Finally, it should be kept in mind that quantification is often problematic in surface analysis and characterization. Firstly because some techniques are not really suited for quantification, but also in cases such as infrared spectroscopy where one does not really know precisely how deep into the material one is probing. Although, there are many good examples of semi-quantitative applications that involve measuring relative band intensities that relate to changes in a surface property. However, for problem solving revealing qualitative differences is often sufficient information to be able to identify cause and move on to look for a potential solution. 

A.L. Smith, Applied Infrared Spectroscopy Fundamentals, Techniques and Analytical Problem-Solving, John Wiley Sons, New York, NY, USA, 1979,... 

The Infrared Region 515 12-4 Molecular Vibrations 516 12-5 IR-Active and IR-lnactive Vibrations 518 12-6 Measurement of the IR Spectrum 519 12-7 Infrared Spectroscopy of Hydrocarbons 522 12-8 Characteristic Absorptions of Alcohols and Amines 527 12-9 Characteristic Absorptions of Carbonyl Compounds 528 12-10 Characteristic Absorptions of C—N Bonds 533 12-11 Simplified Summary of IR Stretching Frequencies 535 12-12 Reading and Interpreting IR Spectra (Solved Problems) 537 12-13 Introduction to Mass Spectrometry 541 12-14 Determination of the Molecular Formula by Mass Spectrometry 545... 

Cyanide is also an effective infrared probe (Yoshikawa et al., 1985). A drawback of this reagent as an infrared probe is its infrared intensity, which is much weaker than that of CO. However, as given in Fig. 10, the recent development in the infrared technique has solved this problem with the introduction of a mercury/cadmium/tellurium (MCT) detector (Fig. 10) (Yoshikawa et al., 1995). The C-N stretch vibrational band is sensitive to many factors, such as the oxidation state and species of the coordinating metal, the structures of porphyrin ring substituents, and the ligand trans to the cyanide and protein structure (Yoshikawa et al., 1985). This technique can be quite effectively applied for determination of the protonation state of the cyanide bound at a metal site. Possible binding modes of cyanide to a ferric iron are shown by Structures (1), (11), and (HI). Infrared spectroscopy is the best method for identihcation of these... 

The widespread use of synthetic polymers has led to the development of a considerable number of analytical tools for polymer characterization and analysis. Analytical pyrolysis, consisting of pyrolysis coupled with an analytical technique, is one of these tools. The technique can be invaluable in solving many practical problems in polymer analysis. It can be used alone or can provide complementary information to other techniques such as thermal analysis, infrared spectroscopy, or even nuclear magnetic resonance. 

When tackling a complex chemical problem in many areas of chemistry, it is advisable to adopt a variety of methodologies, both chemical and instrumental, in combination, rather than relying on a single approach in attempting to solve the problem. In this context, the utilization of infrared spectroscopy in conjunction with chemical derivatization methods has proven to be a fruitful marriage in the solution of many chemical problems in the past. This is particularly true in the case of humic substances—the utility of infrared spectroscopy has been expanded considerably when used in conjunction with chemical derivatization as will be discussed later. 

Infrared spectroscopy (IR) is a fairly simple in situ method. Since the absorption coefficients of molecular vibrations are rather low, it is impossible to detect the IR absorption of a molecule adsorbed or bonded to the semiconductor surface, merely by an ordinary vertical transmission measurement. This problem was solved by using attenuated total reflection (ATR) spectroscopy, as introduced by Harrick [17], and first applied to semiconductor-liquid junctions by Beckmann [18,19]. In this technique, the incident IR light beam is introduced via a prism into a semiconductor, at such an angle that total internal reflection occurs at the semiconductor-liquid interface, as illustrated... 

Conclusions from the Case Study. Exercises such as these are quite common in the characterization of complex solids and do indeed require the combined expertise of a group of specialists. The set of techniques required varies from case to case, but the more or less standard combination of two or more complementary techniques as part of the arsenal is very useful. In retrospect, we were able to identify the techniques which were crucial to solving this problem XPS/TEM, LEIS, XRD and EXAFS. A number of others (Magic-Angle-Spinning NMR (MAS-NMR), Raman Spectroscopy and FTIR (Fourier Transform Infrared Spectroscopy) were applied, but did not add significantly to the final result. The study of various samples which were synthesized in different ways and which showed different catalytic activities did prove relevant, but is not described in detail here. 

Pattacini, S. Solving Analytical Problems Using Infrared Spectroscopy Internal Reflectance Sampling Techniques, Pattacini Associates, LLC Danbury, CT. 

We introduced nuclear magnetic resonance (NMR) in Chapter 3 as part of a three-pronged attack on the problem of determining molecular structure. We showed that mass spectrometry weighs the molecules, Infrared spectroscopy tells us about functional groups, and and Iff NMR tell us about the hydrocarbon skeleton. We concentrated on NMR because it s simpler, and we were forced to admit that we were leaving the details of the most important technique of all—proton ( H) NMR—until a later chapter because it is more complicated than NMR. This is that chapter and we must now tackle those complications. We hope you will see NMR for the beautiful and powerful technique that it surely is. The difficulties are worth mastering for this is the chemist s primary weapon in the battle to solve structures. 

One of the most commonly applied IR techniques developed to overcome these problems is the external reflectance technique. In this method, the shong solvent absorption is minimized by simply pressing a reflective working electrode against the IR transparent window of the electrochemical cell. The sensitivity problem, that is, the enhancement of the signal/noise ratio in the case of external reflectance techniques is solved by various approaches. These are, for instance, electrochemically modulated infrared spectroscopy (EMIRS), in situ FTIR (which use potential modulation), and polarization modulation infrared reflection absorption spectroscopy (PM-IRAS, FTIR) [86,117-123]. 

Acid Halides and Anhydrides Acid halides and anhydrides are rarely isolated as unknown compounds but they are commonly used as reagents and intermediates, and PROBLEM-SOLVING infrared spectroscopy can confirm that an acid has becai converted to a pure acid chlo-... 

Due to the complexity of food matrices several advanced spectroscopic techniques have recently been successfully employed to solve authenticity problems, including near infrared spectroscopy (NIR), mid infrared spectroscopy (MIR), low- and high-field nuclear magnetic resonance (NMR), site-specific natural isotopic fiactionation (SNIF-NMR) and... 

The importance of surface and chemical analysis techniques in electronics corrosion testing cannot be overstated. These powerful tools contribute to solving problems and elucidating corrosion mechanisms in simple and complex systems. Chemical analysis techniques include infrared (IR), ultraviolet (UV), and RAMAN spectroscopy X-ray diffraction atomic adsorption emission and mass spectroscopy gas and liquid chromatography and optical and transmission electron microscopy. Surface analytical techniques include electron spectroscopy for chemical analysis (ESCA), Auger, secondary ion mass spectroscopy (SIMS), and ion scattering spectroscopy (ISS). These important techniques used in conjunction with corrosion tests are described in another section of this manual. 

---