第35卷：第9期 2015年9月
光谱学与光谱
分
析
Spectroscopy and Spectral Analysis
Vol. 35,No. 9 , pp2540-2543 September, 2015
AMethodtoObtainaGoodInfraredSpectrumoftheWet Acetone Gas Samplewithout AnyDryingPretreatment
LIU Qing',CHEN Yu-jing',WANG Hai-shuil+,ZENG Qiangl*,OZAKI Yukihiro
1. School of Chemistry and Chemical Engineering - South China University of Technology, Guangzhou510640, China
2. Department of Chemistry, School of Seience and Technology, Kwansei Gakuin University, 21 Gakuen, Sanda, Hyogo 669-1337, Japan
Abstract
Water vapor in the beam of a Fourier transform infrared (FTIR) spectrometer or/and in a gas cell is
a major source of interference in the infrared measurement of a gas sample. In general, in order to eliminate the effect of water vapor, we have to completely remove these molecules before the measurement of any spectrum. Herein, we provide an approach to collect an IR spectrum of a gas (wet acetone) sample free from water vapor interference without any drying pretreatment. After dozens of scans, the air atmosphere in the sample com Partment of the FTIR spectrometer will be slightly adjusted by small amounts of dry air or wet air (room air) depending on the property of water vapor lines (absorbance>0 or absorbance o). Water vapor lines will then gradually disappear when the ensuing collection process is continued. The experiment results demonstra ted that this method is a facile and very effective way to remove water vapor interference. Moreover, this method works still well for the measurement at 0. 5 cm1 resolution, typically used in the gas infrared meas urement.
Keywords
Water vapor interference; Elimination; Infrared spectrum; High resolution; Gas sample
中图分类号：0657.3
Introduction
文献标识码：A
DOI: 10. 3964/j. issn. 10000593(2015 )o9-254004
compartment normally fluctuates. In the previous study"I , in fluctuating humidity atmosphere (it is not necessary to purge the spectrometer with dry air), we successfully obtained a
Water vapor shows intense and complicated vibration-ro-tation lines in the mid-infrared region. Therefore, analysis of an IR spectrum of a gas sample is often hampered by IR ab-
Usually, the optical bench of the
sorptions of water vapor.
spectrometer should ideally be either purged with dry air or e-vacuated completely and the wet gas sample is also necessary to be dried before the measurement[1-s]. However, both dr-ying processes of the entire spectrometer and the gas cell are time consuming.
During a routine measurement, the sample compartment in the IR spectrometer has to be opened to the atmosphere to allow the exchange between an IR sample and an IR back-
Therefore, the humidity of the air in the sample
ground.
Received: 2015-03-19; accepted: 2015-06-11
Foundation item: Natural Science Foundation of China (20873136)
qualified infrared spectrum of stearic acid film without water vapor interference. One of advantages of our method is that it can exactly match the level of water vapor in the sample and background spectra. In such a measurement, stearic acid film itself does not contain any water vapor molecules. What about the wet sample, can we obtain a desired and qualified IR spec-trum of the wet sample without any drying pretreatment? The general answer to this question will be achieved in the present paper.
The absorbance and full width at half-height (FWHH) of water vapor lines will be changed drastically when the spec-tral resolution becomes higher. For high resolution analysis of gas molecules, water vapor interference will cause more seri-
Biography : LIU Qing, (1986—), Ph. D. Candidate of South China University of Technology
* Corresponding authors
e-mail: wanghsh@scut, edu. cn; ceqzeng@seut, edu, cn