小麦粉中偶氮甲酰胺的太赫兹时域光谱检测

利用太赫兹时域光谱(terahertz time-domain spectroscopy,THz-TDS)技术对偶氮甲酰胺(小麦粉添加剂)、小麦粉及两者混合物进行测试,获得其在0.20~2.00 THz波段的吸收谱与折射率谱。结果显示,偶氮甲酰胺在1.93THz处存在1个明显的特征吸收峰,可用于物质识别。此外,随着混合物中偶氮甲酰胺含量的减少,样品的吸收系数逐渐上升,折射率逐渐下降。通过偏最小二乘法(partial least squares,PLS)对小麦粉中偶氮甲酰胺的含量进行定量分析。结果表明,混合物中偶氮甲酰胺含量与吸收系数、折射率都有良好的线性关系,其中基于吸收系数PLS模型相关系数可达到0.999 9,标准误差为0.06%,检出极限可达0.11%,最大绝对偏差小于0.19%。

Detection of azodicarbonamide in flour based on terahertz time-domain spectroscopy

The characteristic of azodiformamide, flour and their mixtures was investigated within 0.20~2.00 THz region using terahertz time-domain spectroscopy (THz-TDS) technology. The refractive index and absorption spectrum were obtained. Experimental results showed that there was distinct absorption feature for azodiformamide at around 1.93 THz, which can be used as fingerprint for its material recognition. Furthermore, absorption coefficient of mixtures was increased with fewer azodiformamide in mixture, while the refractive index was decreased gradually. The partial least squares (PLS) regression was taken to quantitatively analyse the content of azodiformamide in flour. The result showed that there was a good linear relationship between the content of azodiformamide in the mixture and both parameters of absorption coefficient and refractive index. The correlation factor from PLS model based on absorptioncoefficient was 0.9999, and the root mean square error was 0.06%. The detection limit of azodiformamide concentration in mixture was 0.11% and the maximum absolute deviation error was less than 0.19%. The results indicate that THz-TDS technology can be used to detect the content of additives like azodiformamide in food fields.