1. Fourier Transform Infrared Spectroscopy
November 15, 2006
CH EN 4903
Chad Wilding

2. Outline What is Fourier Transform Infrared (FTIR) Spectroscopy?
Why use FTIR?
The importance of a good baseline
The analysis of aqueous sugar solutions
Conclusions
References

3. What is FTIR? Passes infrared (IR) light through an interferometer
IR light passes through a sample and an interferogram is obtained
A Fourier Transform is performed on the interferogram and a spectrum is defined for the sample

4. Diagram of a FTIR

5. Why Use the FTIR? Identify constituents of organic compounds
Determine the existence of light hydrocarbon gases
Analyze the concentration of aqueous sugar solutions

6. Obtaining the Baseline
Spectra were referenced against the baseline
Distilled water was used as the background
Baseline needs to have virtually zero absorbance or minimal error

7. Analysis of Sugar Solutions
D-Fructose crystals dissolved in distilled water
Sucrose crystals dissolved in distilled water
Sucrose is a combination of a glucose ring bonded to a fructose ring

8. Fructose Spectra

9. Sucrose Spectra

10. Calibration Graphs

11. Calibration Equations
Fructose
Conc.= (log(1/R) )/0.0004
Sucrose
Conc.= (log(1/R) )/0.0003

12. Unknown Spectrum

13. Results Sucrose concentration-79.0 ± 11.7 g/L.
Fructose concentration ± 11.7 g/L.
Actual sucrose concentration-60 g/L.
Actual fructose concentration-240 g/L.

14. Conclusions

15. What is a Good Baseline?
σ1 = 0.226
σ2 = 0.015
σ3 = 0.015

16. References
Schwedt, Georg. The Essential Guide to Analytical Chemistry. New Jersey: Wiley and Sons, 1997.
Crocker, Betty. “Chemical Engineering and Brownies,” 1971.
Wikipedia. Fourier Transform Infrared Spectroscopy

17. Questions and Answers