气体样品傅立叶变换红外光谱定量分析的误差研究

Investigating Quantitative Errors of Fourier Transform Infrared Spectra of Gas Samples

通过分析牧场附近的大气傅立叶变换红外（FT-IR）光谱中NH3的浓度,系统研究了气体样品FT-IR光谱定量分析的误差;分析了不同精度要求下的定量方法及其实现。选择63个实测光谱作为分析对象,其中NH3的浓度分布在0~1400 mmol.mol-1.m。定量分析采用3个NH3参考光谱,浓度分别为40,700和1300 mmol.mol-1.m。结果表明,基于单一参考光谱的定量分析在精度要求不高（如相对误差小于5%）时仍有实用价值,而且简单易行,但其适用范围会随定量精度要求的提高而变窄,直到无效。借助一个高光谱分辨率（0.125 cm-1）的参考光谱,通过迭代求得待测组分较准确的浓度。研究表明,FT-IR光谱分析的优越性在于只需要一个高分辨率的参考光谱即可得到一系列不同浓度的低分辨率参考光谱,方便在定量分析中使用多个参考光谱。本研究为气体样品FT-IR定量分析的规范提供了一定的思路和参考。

Open-path Fourier transform infrared spectra were measured around animal farms.By analyzing those spectra for the concentrations of NH3,a systematic investigation was carried out on the quantitative errors.63 spectra were chosen as the targets in which the concentrations of NH3 vary significantly,from 0 to 1400 mmol·mol-1·m.In the quantitative analysis of the 63 spectra,three reference spectra were used.The concentrations of NH3 in the reference are 40,700 and 1300 mmol·mol-1·m,respectively.The results indicated that the quantitative method based on single reference is practically applicable when the accuracy requirement is not high（e.g.less than 5%）.However,as the accuracy requirement increases,the applicability of the single reference spectrum is gradually limited.When the single reference spectrum is ineffective,the quantification was implemented by an iterative process in which a reference spectrum of high resolution（0.125 cm-1） was used.The results also showed an advantage of FT-IR spectrometry,i.e.multiple reference spectra at low resolution could be obtained without actual measurements if a single reference spectrum at high resolution was available.