ATR-FTIR快速测定食醋总酸的研究

Rapid determination of total acid in vinegar by ATR-FTIR spectroscopy

传统的测定食醋总酸质量浓度的方法为滴定法,该方法操作复杂、费时、对操作人员要求较高,针对传统方法的缺陷,建立了衰减全反射-傅里叶变换红外光谱(ATR-FTIR)快速测定方法。食醋中的酸性物质为羧酸,羧酸中的羰基在1710 cm-1附近有特征吸收峰,该峰强度与食醋总酸质量浓度间存在良好的线性关系,利用这种线性关系测定了15种食醋样品的总酸质量浓度。结果显示:建立的ATR-FTIR分析方法与国家标准方法(GB/T 12456—2008)的测定结果一致,两者间的相关系数为0.9976;9次平行测定结果的相对标准偏差小于1%,方法的检出限(s=3)为0.042%。表明ATR-FTIR光谱法可以用于食醋总酸质量浓度的快速测定,具有操作简便、耗时短、适用范围广泛等优势,可用于实验室研究、食醋生产、储运和生产企业的大规模跟踪测试。

The traditional method for determining the total acid content of vinegar is the titration method,which is complicated,time-consuming,and has high requirements for operators. A rapid method of the determination of total acid content in vinegar by Attenuated total reflection-Fourier transform infrared spectroscopy( ATR-FTIR) was established. The acid substance in vinegar was carboxylic acid,and the carbonyl groups in carboxylic acid had a characteristic peak around 1 710 cm-1. There was a good linear relationship between the peak intensity and the total acid content of vinegar. The total acid content of 15 kinds of vinegar samples was determined. The results determined from the established ATR-FTIR method was consistent with those from the national standard method( GB/T 12456-2008),and the correlation coefficient( R)between them was 0. 997 6;the relative standard deviation( RSD) among the results of 9 replicate determinations was less than 1%( n = 9),and the limit of detection( LOD,s = 3) was 0. 042%,which indicated that ATR-FTIR method could be used for the rapid determination of total acid content in vinegar. Meanwhile,the method is easy to operate,fast,and has a wide range of applications. It can be used for laboratory research,vinegar production,storage and transportation,and large-scale follow-up testing of production enterprises.