IV. ANALYTICAL TECHNIQUES

6. Infrared Spectroscopy (IR, including FTIR)

  1. Knowledge of the principle/theory of IR in drug analysis.
  2. Knowledge of the electromagnetic spectrum.
  3. What are the common units used in IR spectroscopy.
  4. How are IR results displayed?
  5. Explain the theory and mechanism of absorption involving vibrational and rotational spectroscopy
  6. What happens when a molecule absorbs IR radiation?
  7. What effects does water have on the absorption spectrum of another substance?
  8. Can you analyze solids, liquids and gases by IR?
  9. What differences would you expect to see in the different phases?
  10. What is a dipole moment and why is it important in IR spectroscopy?
  11. Why does a compound absorb infrared radiation?
  12. Why is the common FTIR spectrometer not appropriate for conclusive identification of many inorganic compounds?
  13. What significance does the Beer-Lambert law have to infrared radiation?
  14. What must you consider when performing a quantification using IR?
  15. Identify the major functional group absorption areas within an IR spectrum.
  16. Be able to relate key functional areas to specific drug classes.
  17. What region of the IR spectrum is described as the fingerprint region?
  18. Why is the fingerprint region so characteristic of the molecule?
  19. What are the limitations of the IR technique?
  20. What are extraneous peaks?
  21. What is FTIR? How is it different from dispersive IR?
  22. Describe the different sample preparation for transmittance, reflectance and ATR.
  23. What are the various instrumental components of an FTIR spectrometer and their function?
  24. How many moving parts are there in an FTIR spectrometer?
  25. What are common IR radiation sources?
  26. What are common operational problems that can occur in using the FT/IR?
  27. What common preventive maintenance is performed on the FT/IR spectrometer?
  28. Why is it important to run a blank when using the ATR?
  29. What standards can be used to perform a performance check on this unit?
  30. What does LASER stand for?
  31. What does the laser do?
  32. At what wavelength does the laser emit energy?
  33. What will happen if the laser fails?
  34. When does the infrared spectrum provide more discrimination of compounds than a mass spectrum?
  35. What effect does being a volatile base have on your spectrum?
  36. What types of compounds are more readily distinguished by infrared spectroscopy?
  37. What are some common adulterants and diluents present in samples frequently seen in your area?
  38. Can mixtures of compounds be identified by FTIR spectrometry? Explain
  39. What problems occur in trying to identify drugs of abuse using FTIR when they are commonly adulterated with other substances?
  40. How can mixtures affect the qualitative and quantitative FTIR analyses?
  41. What different sample preparation techniques are used in your lab?
  42. Can FT IR be used in quantitative analysis of drugs of abuse? Explain
  43. Describe when you would use a spectral manipulation feature (e.g. subtraction, baseline correction, library searching)
  44. Describe the problems or limitations associated with spectral subtraction.
  45. What limitations exist in doing library searches?
  46. How is baseline correction applied?
  47. Using simple, non-technical terms, explain what an interferometer does?
  48. What is the difference between an IR spectrum and an interferogram?
  49. What is the difference between a dispersive/grating IR spectrometer and an FT-IR spectrometer?
  50. Explain Fourier transform (FT) in layman terms.
  51. What is an evanescent wave?
  52. In what region would you expect a carbonyl group to show absorbance?
  53. What is the typical range of mid IR?
  54. What does ATR stand for?
  55. Describe how IR radiation is converted into a spectrum.
  56. What is necessary for a molecule to be IR active?
  57. Which of the following techniques would not be effective for the analysis of iodine: UV/Vis, Raman, IR? Why not?
  58. Which of the following techniques would not be effective for the analysis of red phosphorus: UV/Vis, Raman, IR? Why not?
  59. In what region of the IR spectrum would you expect to see an -OH stretch?
  60. Why should you run a background with a single beam FT-IR instrument?
  61. Is vapor phase IR suitable for identification of solvents?
  62. Is the basis of the theory for both condensed and vapor phase IR the same?
  63. According to your protocols, how often should the resolution and wavelength accuracy of the infrared spectrometer be checked?
  64. What is the difference in how IR spectra and Raman spectra are plotted?
  65. What is the fundamental difference between IR and Raman?
  66. What is a disadvantage of Raman?
  67. What types of compounds are amenable to Raman analysis?
  68. What part of the EM spectrum does IR involve?
  69. What is the Beer-Lambert Law? How is it applicable to IR analysis?
  70. Why is KBr used in transmittance mode in IR spectroscopy?
  71. What is an ATR sampling accessory?
  72. Could ATR be used for quantitative analysis?
  73. Why are aqueous solutions a poor choice for IR analysis?
  74. What types of samples would not lend themselves to IR analysis?
  75. What do the initials FT-IR stand for?
  76. Who is Michelson? What did he invent?
  77. What is a beam splitter?
  78. What is a beam splitter composed of?
  79. Draw a diagram of an interferometer to show the path that incident IR radiation takes through the instrument and sample to the detector.
  80. What occurs when the beam paths are equidistant?
  81. What occurs when the beam paths vary by ¼ wavelength? By ½ wavelength?
  82. What is the graph of intensity vs. displacement called?
  83. Are all FT-IR single beam instruments?
  84. What is an apodization function? What does it do?
  85. Name 5 factors that affect the resolving power of FT-IR.
  86. Describe 6 advantages of FT-IR over dispersive IR.
  87. What type of laser is used in the FT-IR.
  88. What detectors are commonly used in FT-IR?
  89. What two criteria are used to evaluate detectors?
  90. What detector is used with an FT-IR microscope and why?
  91. What is a corner cube reflector?
  92. What advantages does the corner cube reflector have?
  93. Which types of vibrations occur at shorter wavelengths, stretching or bending? Why?
  94. Stretching vibrations require _______ energy than bending vibrations.
  95. The longer the wavelength, the lower the energy. ( T or F)
  96. Why do we not see a C=C symmetrical stretching vibration in the IR region?
  97. What is the standard range (in wavenumbers) used for an IR spectrum?
  98. Draw an example of scissoring, rocking and wagging deformations. Use CO 2 as your model.
  99. The process in which IR energy is transferred to a molecule is called __________________.
  100. What is the relationship between absorption and transmittance?
    • For the functional groups: (A) C-C (B) C=C (C) C≡C
  101. Which would absorb at higher energy?
  102. Which would absorb at higher wavenumber?
  103. Which would absorb at longer wavelength?
  104. What is a fundamental vibration?
  105. What is an overtone vibration?
  106. What is a combination vibration?
  107. Draw an energy diagram of all types of molecular transitions.
  108. What is meant by the term wave length degeneracy?

Last Update June 2018

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