Communication pubs.acs.org/jchemeduc
A Convenient and Cost-Effective Fourier Transform Infrared (FTIR) Spectrometer Purging Setup for the Undergraduate Teaching Laboratory Ying Sun, Ye Zou, and Gang Ma* College of Chemistry and Environmental Science, Hebei University, Baoding 071002, China S Supporting Information *
ABSTRACT: The construction of a convenient FTIR spectrometer purging setup for the undergraduate teaching laboratory is described. This simple setup consists of an inexpensive aquarium air pump and a drying-tube assembly. This setup can efficiently suppress atmospheric water-vapor interference, thus producing good-quality FTIR spectra.
KEYWORDS: First-Year Undergraduate/General, Second-Year Undergraduate, Upper-Division Undergraduate, Analytical Chemistry, Organic Chemistry, Physical Chemistry, IR Spectroscopy, Laboratory Equipment/Apparatus
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built-in compartment inlet on the back of the FTIR spectrometer. Details of the purging setup used in our lab are provided in the Supporting Information. To illustrate the efficiency of the proposed purging setup, the FTIR spectra of a protein sample in a KBr pellet taken with purging (top spectrum) and without purging (bottom spectrum) are shown in Figure 2. The shaded areas indicate the spectral regions affected by water-vapor absorption. The smoothness of the top spectrum in the shaded regions clearly demonstrates the suppression of water-vapor interference.
earning and practicing Fourier transform infrared (FTIR) spectroscopy has become an integral part of analytical, organic, and physical chemistry laboratories in undergraduate chemistry curriculum.1−3 In FTIR spectroscopy, atmospheric water-vapor interference is notorious due to its significant effect on spectral quality. Purging the FTIR spectrometer with dry gas can be an effective approach to suppress water-vapor interference. There are two widely used approaches to suppress watervapor interference in FTIR spectroscopy in a research laboratory. One approach is to use a commercial IR purge generator, which can produce dry air with negligible water content and the other approach is to use an ultrapure nitrogen gas cylinder as the dry gas source. These two approaches result in satisfactory purging efficiency and can be considered “research-grade” purging systems. Yet, neither of the two approaches is suitable for an undergraduate teaching laboratory as they are either too expensive or inconvenient. Here a simple FTIR purging setup that is more suitable for teaching is described.
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DISCUSSION Both the aquarium air pump and the plastic drying tube are commercially available and can be purchased for less than 100 U.S. dollars. A common glass drying tower is not recommended due to safety concerns. In addition, when the teaching lab is equipped with house nitrogen (as is the case in many U.S. universities), the air pump is unnecessary and the house nitrogen can be used as the gas source. Purging the FTIR spectrometer is common practice in research involving FTIR spectroscopy, yet such purging equipment is often lacking in undergraduate teaching laboratories. We believe incorporating a purging setup such as the one described in an undergraduate FTIR teaching laboratory will be beneficial to the future research careers of the undergraduate students.
CONSTRUCTION OF THE PURGING SETUP
Purging an FTIR spectrometer is conceptually simple and only requires a flow of dry gas. The combination of an air pump and a drying-tube assembly is a convenient way to achieve this goal. Figure 1 illustrates the concept of such a purging setup. The air pump is an inexpensive aquarium pump. The four tubes of the drying-tube assembly are filled with desiccants that absorb water vapor. This purging setup is directly connected to the © XXXX American Chemical Society and Division of Chemical Education, Inc.
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dx.doi.org/10.1021/ed300788z | J. Chem. Educ. XXXX, XXX, XXX−XXX
Journal of Chemical Education
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Communication
REFERENCES
(1) Schuttlefield, J. D.; Grassian, V. H. J. Chem. Educ. 2008, 85, 279. (2) Ault, A. P.; Robert, P. J. Chem. Educ. 2012, 89, 243. (3) Feng, Z. V.; Buchman, J. T. J. Chem. Educ. 2012, 89, 1561.
Figure 1. Purging setup: (A) air pump, (B) tubing, (C) drying assembly, (D) FTIR spectrometer (Vertex 70, Bruker, Germany), and (E) gas inlets on the back of spectrometer.
Figure 2. FTIR spectra of a protein sample in a KBr pellet: (top) with purging and (bottom) without purging. Shaded areas indicate spectral regions affected by water-vapor absorption. Peaks around 2350 cm−1 are due to CO2 absorption. Acquisition parameter: 32 scans and 4 cm−1 resolution.
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ASSOCIATED CONTENT
S Supporting Information *
Specifications of the purging setup, use of the purging setup, and single-beam spectrum of air. This material is available via the Internet at http://pubs.acs.org.
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected],
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS We acknowledge supports from Hebei University (2010-184) and National Natural Science Foundation of China (21075027). G.M. also acknowledges Kandice Harper for language editing. B
dx.doi.org/10.1021/ed300788z | J. Chem. Educ. XXXX, XXX, XXX−XXX
