Open-Path FTIR Gas Detection Method Based on Two-Dimensional Correlation Infrared Spectroscopy
WANG Na1, 3, DONG Da-ming1, 3*, JIAO Lei-zi2，3
1. Guilin University of Electronic Technology，Guilin 541004，China
2. Guangxi Key Laboratory of Optoelectronic Information Processing (Guilin University of Electronic Technology), Guilin 541004, China
3. National Engineering Research Center for Information Technology in Agriculture，Beijing Academy of Agriculture and Forestry Sciences, Beijing 100097，China
Abstract：Open-Path Fourier Transform infrared spectroscopy (OP-FTIR) enables fast, flexible, and quantitative detection of gas, but OP-FTIR signal is weak compared to gas pool extraction methods, and its ability to detect gas is restricted. In order to improve its detecting capacity of gas, two-dimensional correlation analysis is performed on the measured infrared spectrum data of the gas with natural gas flow disturbance. The ethanol gas and two kinds of Chinese spirits’ volatiles were used as the verification objects. The infrared absorption spectra of ethanol gas and the volatiles of Luzhouteniang and Fenjiu were measured by OP-FTIR method. In the untreated infrared absorption spectrum of ethanol gas, no obvious characteristic peak of ethanol was observed. The two-dimensional correlation analysis of the infrared absorption spectrum data showed that there was an obvious autopeak centered at 1 050 cm-1 in the two-dimensional correlation synchronous spectrum, and the autopeak came from ethanol. The results verified that the gas detection ability of the OP-FTIR method which is combined with two-dimensional correlation infrared spectroscopy was improved. The infrared absorption spectrum data of different concentrations of ethanol gas were processed by synchronous two-dimensional correlation. It was found that the autopeak intensity centered at 1 050 cm-1 in the two-dimensional correlation synchronous spectrum increased with the increase of ethanol gas concentration, indicating that OP-FTIR gas detection method based on two-dimensional correlation spectrum has a certain quantitative analysis capability. When detecting the volatiles of Luzhouteniang and Fenjiu by OP-FTIR method, the ethanol gas in the volatile matter was detected in the region of 820～1 480 cm-1, and the gas content was measured by the intensity of the auto peak at (1 050, 1 050 cm-1) in the two-dimensional correlation synchronous spectrum. The results showed that the ethanol gas content in the volatiles of the Luzhouteniang is higher than that in Fenjiu; the aroma components in the volatile matter were detected by the region of 1 700～1 820 and 1 400～1 600 cm-1, by comparing the two-dimensional asynchronous spectrum of the volatiles of the Luzhouteniang and Fenjiu, it found that there are more cross peaks in the two-dimensional asynchronous spectrum of the volatiles of Luzhouteniang, so Luzhouteniang showed more abundant aroma substances information compared to the volatiles of Fenjiu, this difference can be used to identify the volatiles of Fenjiu and Luzhouteniang. The research proved that the OP-FTIR gas detection method based on two-dimensional correlation infrared spectroscopy realized the improvement of the gas detection ability of OP-FTIR method, and has certain quantitative analysis ability. At the same time, combined with two-dimensional correlation infrared spectroscopy, OP-FTIR also has further research significance for identifying different volatile matter.
Key words：Two-dimensional correlation infrared spectroscopy; Open-path FTIR; Gas detection
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