近红外光谱法间接测定白酒酒精度

白酒是深受消费者喜爱的一种日常含酒精饮品，酒精度是衡量其品质的关键指标之一。简单、快速的酒精度分析方法有助于提升白酒的检验效率。光谱法具有响应快速、无损分析的优点，可为酒精度的分析提供较好的帮助。水分子对红外光具有较好的吸收效果，基于此特征探究了利用近红外光谱间接分析白酒中酒精度的方法。研究发现光程对水和乙醇分子的紫外-可见-近红外吸收光谱有影响，水分子在1 448 nm附近有一个独立的吸收峰，此吸收峰在光程10 mm条件下出现突跃，但当光程降低为1 mm时，峰形变为对称且平滑状态，可用于定量分析。乙醇水溶液在1 000～1 800 nm范围内的吸收峰随着乙醇含量的增大呈规律性递减，乙醇和水分子间的作用力未对二者的吸收光谱产生显著影响。提取1 448 nm处的吸光度，得出吸光度与酒精含量的线性方程：A=1.38-0.013m%（R2=0.996 7），酒精度低于20%或高于80%时的拟合效果存在较大的相对偏差。20%～80%范围获得拟合效果优良的线性拟合方程：A=1.40-0.014m%(R2=0.999 3)。并通过购置的部分市售散装白酒和品牌瓶装白酒检验了该方法的可靠性，本方法对品牌瓶装白酒的检测与瓶身标记的酒精度的相对偏差较小，符合吸收光谱的允许误差范围，而对部分散装白酒的检测结果与其标注的酒精度相差较大，鉴于散装白酒在品质控制方面弱于品牌瓶装白酒，在一定程度上说明本方法在检测白酒酒精度方面具有较好的准确度，且具有方便、快速、无需辅助试剂、线性范围宽的优点，可作为一种快速分析白酒酒精度的测试手段。

Indirect Determination of Liquor Alcohol Content Based on Near-Infrared Spectrophotometry

Alcohol is a key technical indicator of liquor, a favorite of consumers as a daily drinking. A simple and fast detection method for ethanol in liquor can help to improve the efficiency of a liquor inspection. Spectroscopy with the advantages of rapid and non-destructive can provide help for the analysis of ethanol content. Based on the good absorption effect of water molecules on infrared light, this paper explored the feasibility of indirect analysis of ethanol content in liquor by near-infrared spectrophotometry. By studying the effect of the optical path on the UV-VIS-NIR absorption spectra of water and ethanol, it is found that water molecules have an independent absorption peak at 1 448 nm. This absorption peak has a mutational point under the optical path of 10 mm. However, when the optical path is reduced to 1 mm, the shape of the absorption peak becomes symmetric and smooth, bringing the possibility of quantitative analysis. The absorption peak of aqueous ethanol solution in the range of 1 000~1 800 nm regularly decreases with the increase of ethanol content. It shows that the force between ethanol and water molecules do not affect their absorption spectrum. The linear equation between absorbance and alcohol content is obtained: A=1.38-0.013m% (R2=0.996 7) by extracting the absorbance at 1 448 nm. However, the fitting effect has a large relative deviation when the alcohol content is lower than 20% or higher than 80%. A better linear fitting equation with an excellent fitting effect is obtained: A=1.40-0.014m% (R2=0.999 3) after adjusting the fitting range to 20%~80%. The reliability of this method was tested through some purchased bulk and brand liquors. The results obtained by this method show a small relative deviation with the alcohol content marked on brand bottles, which is within the allowable error range of absorption spectrum analysis. Moreover, there are large relative deviations in the test measurement results of part of bulk liquors, which may be caused by the weaker quality control of bulk liquor. To some extent, this method has good accuracy and precision in detecting the alcohol content of liquor. This method has the advantages of convenience, rapid, no auxiliary reagent and wide linear range. It can be used as a test method for quickly analyzing the alcohol content of liquor.