Zhao An-xin, Tang Xiao-jun, Zhang Zhong-hua, Liu Jun-hua
Guang Pu Xue Yu Guang Pu Fen Xi. 2016 May;36(5):1340-4.
In the smoothing pretreatment for the quantitative analysis of hydrocarbon mixed gases by Fourier transform infrared analysis (FTIR), the Savitzky- Golay filter is usually used as one of the smoothing preprocessing methods in the Fourier transform infrared spectrum data smoothing pretreatment. However, the parameters of the Savitzky-Golay filter such as the polynomial order and frame size are not easy to decide. There is no one unified choice basis. Users usually adopt multiple sets in the special data set to try, and then select a set of relatively optimal data as the optimizing parameters of the Savitzky-Golay filter. The optimal selection method of the Savitzky-Golay filter parameters was explored, and the concrete calculation equations were deduced according to the relation among the normalized cut-off frequency, the normalized beginning frequency of the stopband, the normalized first side lobe peak frequency of the stopband, the normalized first side lobe peak amplitude with the polynomial order and frame size of the Savitzky-Golay filter parameters. Then when the polynomial order and frame size are set as 8 and 11 respectively according the above conclusion and the characteristics of the actual spectral data, the Savitzky - Golay filter smoothing effect is optimum. Through the acquisition the concentration of 0.1%, 0.2%, 0.5%, 1%, 2%, 5% for the actual CH4 spectra, the relative maximum and minimum error of the raw spectra converted absorbance were 17.230 5% and 0.243 0% respectively, and the relative maximum and minimum error of the smooth spectra converted absorbance were 0.088 0% and 0.088 0% respectively in the second absorption peak. The relative error of converted absorbance was basically stable through the Savitzky-Golay filter after the spectral data preprocessing and it was relatively low, so, it laid a foundation for the late spectral data accurate qualitative and quantitative analysis.
在利用傅里叶变换红外分析（FTIR）对烃类混合气体进行定量分析的平滑预处理中，Savitzky-Golay滤波器通常作为傅里叶变换红外光谱数据平滑预处理的平滑预处理方法之一。然而，Savitzky-Golay滤波器的参数，如多项式阶数和帧大小不易确定。没有统一的选择依据。用户通常在特定数据集中采用多组进行尝试，然后选择一组相对最优的数据作为Savitzky-Golay滤波器的优化参数。探索了Savitzky-Golay滤波器参数的最优选择方法，并根据Savitzky-Golay滤波器参数的归一化截止频率、阻带归一化起始频率、阻带归一化第一旁瓣峰值频率、归一化第一旁瓣峰值幅度与多项式阶数和帧大小之间的关系推导了具体的计算公式。然后根据上述结论和实际光谱数据的特点，当多项式阶数和帧大小分别设置为8和11时，Savitzky-Golay滤波器的平滑效果最佳。通过采集实际CH4光谱浓度为0.1%、0.2%、0.5%、1%、2%、5%的数据，原始光谱转换吸光度的相对最大和最小误差分别为17.230 5%和0.243 0%，平滑光谱转换吸光度在第二个吸收峰处的相对最大和最小误差分别为0.088 0%和0.088 0%。光谱数据预处理后经Savitzky-Golay滤波器转换吸光度的相对误差基本稳定且相对较低，为后期光谱数据的准确定性和定量分析奠定了基础。
