Fourier Transform Infrared Spectroscopy (FTIR)

This experiment was developed by S.E. Van Bramer for Chemistry 465 at Widener University.


Fourier Transform InfraRed (FTIR) spectroscopy is a useful technique for identifying organic functional groups and for high resolution experiments. This instrument has some significant advantages over dispersive instruments. The Michelson interferometer used for most FTIR instruments increases S/N and resolution. In this experiment you will use the Nicolet Avatar 320 FTIR. Using the gas cell you will aquire the spectrum of HCl using different instrument settings. Using the diffuse reflectance accessory and the Horizontal Attenuated Total Reflectance (HATR) accessory you will identify several unknown pharmacuticals and plastics. This experiment will introduce the major instrument parameters to demonstrate how they effect the spectrum, and demonstrate several different sampling techniques used for FTIR.


  1. Introduction to FTIR.
    1. Beginners Guide to FTIR. Run the online tutorial with the Omnic software.
    2. ARK Multibounce HATR. Learn about the HATR accessory with the online tutorial in the Omnic software (Help, Sampling).
    3. Avatar diffuse reflectance. Learn about diffuce reflectance with the online tutorial in the Omnic software (Help, Sampling).
    4. Take off all the instrument covers (with your instructor) and review how the instrument operates.

  2. The goal of the next part of this experiment is to determine how several different instrument settings effect the spectra obtained with an FTIR instrument. These settings are adjusted in the Omnic software (Collect, Experiment Setup). Using the gas cell and HCL vapor, obtain spectra with various settings to demonstrate:
    1. Resolution
    2. Number of Scans (set to 1 cm-1 resolution)
    3. Zero Fill (set to 1 cm-1 resolution)
    4. Apodization (set to 1 cm-1 resolution)

    Use the software help menues, your textbook, and the articles provided to find what each of these settings is doing. Look carefully at your data to be certain that you can show what is happening when you writeup your lab report.

  3. Your instructor will provide tablets for several over the counter medications. Using the appropriate sample accessory, obtain spectra that will allow you to identify these unknowns.

  4. Your instructor will provide several pieces of plastic. Using the appropriate sample accessory, obtain spectra that will allow you to identify these unknowns.

Laboratory Write-up:

Your Laboratory write-up should include the following information
  1. (5 pts) An abstract for this experiment.

  2. (20 pts) Data acquisition. Use clearly labeled spectra to discuss the following:
    1. How does the number of scans effect the spectrum?
    2. How does the resolution effect the spectrum?
    3. How does the zero fill effect the spectrum?
    4. How does the apodization effect the spectrum?

  3. (20 pts) Identify the unknowns. Annotate the spectrum and provide references to explain your interpretation.

  • (5 pts) The Carbon pages from your laboratory manual.

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    Scott Van Bramer
    Department of Chemistry
    Widener University
    Chester, PA 19013

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    Last Updated Thursday, September 02, 1999 12:40:49 PM