Exploratory Research on Quantitative Analysis of Gaseous Mixtures by AOTF-NIR Spectrometer
HAO Hui-min1, 2, CAO Jian-an1, YU Zhi-qiang2, Ken Jia3, LIU Jun-hua1
1. Department of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China 2. Taiyuan Iron & Steel (Group) Company Ltd., Taiyuan 030003, China 3. Department of Research and Development, Brimrose Corporation of America, Baltimore 21152-9201, USA
摘要： 探索了以声光可调滤波器(acousto-optic tunable filter，AOTF)为分光器件的新一代近红外(NIR)光谱仪用于气体检测的可行性，并提出一种多组分混合气体近红外光谱分析的新方法。将一个自制的气室与AOTF-NIR光谱仪配接，从而实现了当前仅限于固体和液体检测的AOTF-NIR光谱仪对气体的检测。实验首先获取并比较了甲烷在不同浓度下的近红外光谱。结果显示，当浓度大于0.1%时，甲烷的吸光度明显地随其浓度的增加而增加。随后参照仪器对甲烷的检测低限设计了甲烷、乙烷和丙烷三组分混合气体样本，并采集了它们的近红外光谱。三种组分气体的定量分析模型由核偏最小二乘(kernel partial least squares，KPLS)回归法建立，模型的预测能力采用检验集的预测均方根误差(root mean square error of prediction，RMSEP)评定。与偏最小二乘(PLS)回归分析效果的对比研究表明，KPLS回归较PLS回归在NIR光谱数据的分析上更具优越性。
关键词：声光可调滤波器;近红外光谱;核偏最小二乘回归;气体混合物;定量分析
Abstract：Due to its many advantages, such as miniaturization, high accuracy, high resolution, fast scanning speed, increased robustness and good stability, acousto-optic tunable filter (AOTF)-near infrared (NIR) spectrometer has been successfully applied in many fields. However, up to now, the commercial AOTF-NIR spectrometers can only be used for liquid and solid detection, but not for the detection of gaseous samples. In the present paper, the feasibility of quantitative analysis of gaseous mixtures by using AOTF-NIR spectrometer was investigated. A homemade gas cell was assembled to an AOTF-NIR spectrometer with probe for liquid detection to obtain NIR spectra of detected gas samples. The gas samples were composed of two groups: single-component CH4 and ternary component gaseous mixture of CH4, C2H6, and C3H8. The detection ability of fitted AOTF-NIR spectrometer was tested firstly. Comparing the absorption spectra of various concentrations, the absorbance of CH4 in absorption bands obviously increased with concentration increasing when the concentration was over 0.1%. According to the detection results, the lower limit of detection (LLD) of the AOTF-NIR spectrometer with gas cell was estimated to be 898 μL·L-1. Subsequently, the NIR spectra of ternary mixtures were collected. The kernel partial least squares (KPLS) regression was employed to create the quantitative analysis model of three components gases. To evaluate the analysis ability of KPLS model, the PLS model was also created. The prediction results of the identical testing set show that the root mean square error of prediction (RMSEP) of three components predicted by KPLS model was 1.08%, 0.87%, and 0.79%, respectively, less than the RMSEP by PLS model. The exploratory work indicates that accurate quantitative analysis of ternary component alkane gaseous mixtures can be achieved by fitted AOTF-NIR spectrometer despite of some limitations, and KPLS regression is an excellent approach to NIR spectra analysis.
郝惠敏1, 2,曹建安1,于志强2,Ken Jia3,刘君华1 . AOTF-NIR光谱仪用于混合气体定量分析的探索[J]. 光谱学与光谱分析, 2009, 29(08): 2087-2091.
HAO Hui-min1, 2, CAO Jian-an1, YU Zhi-qiang2, Ken Jia3, LIU Jun-hua1 . Exploratory Research on Quantitative Analysis of Gaseous Mixtures by AOTF-NIR Spectrometer . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2009, 29(08): 2087-2091.
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