Chem 211 - Infrared Spectroscopy

Infrared Spectroscopy (FT-IR)
Infrared spectroscopy is a technique used to identify various functional groups in unknown substances through the identification of different covalent bonds that are present in the compound. By identifying the different covalent bonds that are present in a compound, you can establish the types of functional groups present. By comparing the absorptions seen in an experimental spectrum to the literature absorptions of various functional groups, you can determine a list of possible identities for the bonds present.

Apparatus

Procedure
FT-IR spectra may be run from 8 AM to 6 PM Monday-Friday ONLY. If you want to run one during another lab, please get the Instructor's approval.

1. If the software is not already running, double click on the Spectrum icon to start the acquisition program. When prompted, log in as chem211 with the password org211.

The instrument is 1. Spectrum One. Do not activate IR assistant. Press Return or click OK.

2. The program will open and check the hardware. Then you will see a message which is titled Accessory Ready Check. It should say System Ready for Use. You may click the Cancel button.

2A. If you are not the first user and there is a spectrum already displayed, click on the Delete icon to clear the window for you.

3. Run a background spectrum.

A. Make sure the sample area is clean and empty.

B. Choose Scan from the Instrument menu drop down list. A window titled Spectrum One Scan and Instrument Setup will open. It has several pages accessed by clicking on the tabs. Choose the Sample tab and type the name background for Name. Next click on the Scan tab and, under Options in the middle of the page, select Background as the Scan type. All other settings can be left with their default values.

C. Click the Apply button and then the Scan button. The window will refresh, and soon you will see your background scan as it is running. A bar in the lower left corner of the screen shows the progress of the scan. WAIT UNTIL THE SCAN FINISHES. When the scan is complete, you may be asked if you want to overwrite the old background scan. Answer Overwrite.

D. Click the Delete icon to clear the spectrum window. The background scan is not lost!

4. Run a spectrum of your sample.

A. Place a small quantity of your sample on the center of the sample plate. Swing the pressure arm over the sample and adjust until it touches the sample. Do not apply pressure yet.

B. Choose Scan from the Instrument menu drop down list.

C. The Spectrum One Scan and Instrument Setup window will open. Choose the Sample tab and enter a filename for your sample in the Name line. Fill in the description and comments as you choose. Then click the Apply button.

D. If you have a liquid, go to E. For a solid, click on the Monitor icon (it looks like a fuel gauge)in the upper left corner of the window. Then choose the Sample icon (the second from the left of the three or four blue-ringed icons) and adjust the pressure by turning the knurled knob on the pressure arm. You will see a green bar appear in the Force Gauge area. Adjust the pressure until the green bar almost fills the window. You should have a reading of 100-120 (above the right end of the bar). Click the Stop button to stop monitoring, then click the Scan button to start your scan. You will be able to monitor the progress of your scan as it runs.

E. For a liquid, click the Scan button to start your scan. You will be able to monitor the progress of your scan as it runs.

5. Analyze and print your data.

A. You can click on the Peaks icon to automatically label your peaks. Clicking a second time removes the labels. To label peaks in another way , click on the vertical cursor icon, Vcursr, then drag the green line over the peak and double click. (If you need to adjust the threshold, choose Peak Table from the Process menu drop down list and set a new threshold. Close Peak Table, then click on peaks twice, (once to remove the old labels and again to show the new) then click on the box to enlarge the image.)

B. You may zoom a region of the spectrum by dragging a box around the region of interest and then double clicking inside the box. The AutoX and AutoY icons will resize the spectrum to full scale.

C. Click on the Text icon to add text to your spectrum. You have control of the font, and you can drag the text to a new position after it is written.

D. Click on the Print icon to print a copy of your spectrum.

E. Click the Delete icon to clear the screen for the next user, or logout if that is appropriate.