太赫兹光谱法检测面粉中过氧化苯甲酰含量

摘要

检测40个不同过氧化苯甲酰含量的面粉样品的太赫兹时域谱,获得其在0.2～2.0 THz频段内的频域谱、折射谱及吸收谱.时域谱表明,与参考信号相比,添加过氧化苯甲酰的面粉样品,其太赫兹波幅值出现了不同程度的降低,面粉样品的频域信号出现了不同程度的延迟现象.频域谱表明面粉样品中过氧化苯甲酰的含量越高,其频域谱的幅值越大,对太赫兹波的吸收强度越小,过氧化苯甲酰在一定程度上降低了面粉样品对太赫兹波的吸收.折射谱表明随着频率的增加,折射率逐渐降低,随着面粉中过氧化苯甲酰的含量增加,面粉样品的折射率随之增大.吸收谱表明面粉样品中的过氧化苯甲酰在1.6 THz处存在一个较为明显的特征吸收峰.因此,太赫兹光谱可用于面粉中过氧化苯甲酰的特征识别.利用40个面粉样品的吸收谱数据作为输入变量,分别采用偏最小二乘(partial least squares,PLS)、支持向量回归(support vector regression,SVR)及最小二乘支持向量回归(least squares support vector regression,LS-SVR)建立校正模型,其中PLS和SVR模型得到的决定系数(R2)都低于0.9,相对标准偏差(relative standard deviation,RSD)都大于10％,而LS-SVR模型的R2为0.986,RSD为4.30％,结果表明太赫兹光谱分析技术可以用于检测面粉中过氧化苯甲酰含量.%Terahertz time domain spectra for 40 flour samples with different contents of benzoyl peroxide were measured,and frequency domain spectra,refractive spectra and absorption spectra were obtained in the range of 0.2-2.0 THz.The time domain spectra indicated that the terahertz wave amplitude value of the flour samples with benzoyl peroxide was reduced as compared to reference signal,and the frequency domain signal was delayed to different degrees.The frequency domain spectra indicated larger amplitude and lower intensity of terahertz wave absorption for flour samples with higher content of benzoyl peroxide,demonstrating that benzoyl peroxide could reduce terahertz wave absorption in flour.The refractive spectra indicated that refractive index decreased gradually with the increase in frequency,but it increased with increasing content of benzoyl peroxide in flour.The absorption spectra indicated that benzoyl peroxide in flour samples had a significant characteristic absorption peak at 1.6 THz.Therefore,terahertz spectrum can be used for the identification of benzoyl peroxide in flour.Partial least squares (PLS),support vector regression (SVR) and least squares support vector regression (LS-SVR) were used separately to establish a calibration model by using the absorption spectral data of 40 flour samples as input variables.The determination coefficients (R2) of both the PLS and SVR models were lower than 0.9,with relative standard deviations (RSD) greater than 10％,while the R2 of the LS-SVR model was 0.986,with RSD of 4.30％,indicating that terahertz spectroscopy can be used to detect the content of benzoyl peroxide in flour.