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Questions and Answers
What is the typical transmittance range for a C triple bond (alkyne) signal in IR spectrum?
What is the typical transmittance range for a C triple bond (alkyne) signal in IR spectrum?
- 80% or more (correct)
- 100% transmittance only
- Less than 20%
- Between 20% to 50%
What is the function of the beam splitter in a Michelson interferometer?
What is the function of the beam splitter in a Michelson interferometer?
- To split the light and direct it towards fixed and movable mirrors (correct)
- To split the light into different wavelengths
- To absorb the light and reduce noise
- To reflect the light towards the detector
What is the main advantage of FT-IR over dispersive IR spectrometer?
What is the main advantage of FT-IR over dispersive IR spectrometer?
- Simultaneous measurement of all wavelengths (correct)
- Sequential measurement of each wavelength
- Higher signal to noise ratio
- Faster measurement time
What is the purpose of the He-Ne laser beam in a Michelson interferometer?
What is the purpose of the He-Ne laser beam in a Michelson interferometer?
What is the first step in getting a sample's FT-IR spectrum?
What is the first step in getting a sample's FT-IR spectrum?
What is the main advantage of FT-IR in terms of signal to noise ratio?
What is the main advantage of FT-IR in terms of signal to noise ratio?
What is the primary objective of dividing the FT spectrum of a sample by the reference spectrum?
What is the primary objective of dividing the FT spectrum of a sample by the reference spectrum?
What is the main advantage of FT-IR spectroscopy over dispersive IR spectrometers?
What is the main advantage of FT-IR spectroscopy over dispersive IR spectrometers?
What is the range of protein concentration that can be measured using FT-IR spectroscopy?
What is the range of protein concentration that can be measured using FT-IR spectroscopy?
What is the primary limitation of FT-IR spectroscopy in analyzing protein samples?
What is the primary limitation of FT-IR spectroscopy in analyzing protein samples?
What is the primary application of FT-IR spectroscopy in protein characterization?
What is the primary application of FT-IR spectroscopy in protein characterization?
What is the primary advantage of FT-IR spectroscopy in terms of sample preparation?
What is the primary advantage of FT-IR spectroscopy in terms of sample preparation?
What principle of IR spectroscopy allows for the identification of functional groups in a sample?
What principle of IR spectroscopy allows for the identification of functional groups in a sample?
What frequency range is typically measured in wave numbers in FTIR?
What frequency range is typically measured in wave numbers in FTIR?
What does FTIR rely on to generate spectra?
What does FTIR rely on to generate spectra?
What is a key advantage of FTIR over dispersive IR spectrometer?
What is a key advantage of FTIR over dispersive IR spectrometer?
How can a sample's FT-IR spectrum be obtained?
How can a sample's FT-IR spectrum be obtained?
What specific absorption corresponds to in FTIR spectroscopy?
What specific absorption corresponds to in FTIR spectroscopy?
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Study Notes
Infrared (IR) Spectroscopy
- IR spectrum measures absorption of IR radiation by molecules
- Atoms are in continuous motion, and bonds are rotating, resulting in different types of motions occurring in bonded atoms
- Each motion occurs at a specific energy, which is utilized to generate IR spectrum
IR Spectrum Measurement
- IR source: Mid IR (Nernst glower, Globar source), Near IR (Tungsten halogen), Far IR (High pressure Mercury vapour lamp)
- Traditional dispersive IR spectrometer: IR source, diffraction grating, light is directed towards diffraction grating, and each beam is mechanically directed towards the sample
- FT-IR spectrometer: Michelson interferometer, beam splitter, fixed and movable mirrors, and simultaneous measurement of all wavelengths
Advantages of FT-IR
- Improved signal to noise ratio
- Fast
- Accurate wavenumber
FT-IR Spectrum Application
- Identify and verify samples
- Characterize new materials
- Useful in manufacturing, chemical synthesis, R&D, and pharma sector
- Analyze chemical reactions, including those with functional groups
- Protein characterization, including secondary structure, and ligand screening
FT-IR Spectrum of Proteins
- Amide I: C=O stretching, characteristic of secondary structure
- Amide II: N-H bending and C-N stretching
- Shape and location of Amide I are characteristic of secondary structure
Protein Characterization using FT-IR
- Application 1: Protein secondary structure characterization, particularly sensitive to β sheets
- Application 2: Proteins structural transitions, stability
- Application 3: Protein concentration estimation, accurate and precise, requires pre-calibration
- Application 4: Identification and characterization of impurities, distinct peaks than proteins
Additional Benefits of FT-IR
- Analyze sample as it is
- Results within minutes
- Not limited by buffer components
- Liquids or solids can be analyzed, even opaque
Limitations of FT-IR
- Water: Temperature sensitive, strong signal masks amide I band
- Low concentration: Low signal
- Atmospheric interferences: Water vapour, CO2, require high-end IR spectrometer
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