傅里叶变换红外光谱法测定油脂碘价的方法研究

DETERMINATION OF IODINE VALUES OF OILS BY FOURIER TRANSFORMATION INFRARED SPECTROSCOPY

提出将石英比色皿用于油脂碘价(IV)的傅里叶红外变换光谱法(FTIR)测定的方法。油脂四氯化碳溶液的FTIR谱图中,油脂分子中碳碳双键上的C—H在3 010 cm-1附近有特征吸收峰,该峰峰高A和样品质量浓度c的比值A/c与油脂IV间存在良好线性关系。利用椰子油和亚麻籽油按一定比例配制的油脂标准样品,建立了IV测定的标准曲线:A/c=2.026 2×IV-30.37,R2=0.999 5。10种不同油脂样品的碘价测定结果显示,所建方法测定的碘价(IVIR)与国家标准方法(IVGB)的结果一致,二者相关关系为IVIR=1.004×IVGB-1.39,R2=0.997 8,表明该方法可以用于食用油碘价的快速测定。

The absorption band of majority inorganic compounds,organic compounds and fundamental surface adsorbate are appeared in the middle-infrared region of infrared spectra,which is suitable for the qualitative and quantitative analysis of various compounds. A method for the determination of iodine values(IV) of oils by Fourier transform infrared spectroscopy(FTIR) combined with a quartz cell was presented in this study. In FTIR spectra of oils/carbon tetrachloride solution,the characteristic absorption peak of C-H stretching in the olefinic double bond was near 3 010 cm-1. There was a good linear relationship between the ratio of A/c(A,peak height;c,concentration of oil) and IV of oil sample. The standard curve of IV determination was established using the standard samples prepared by coconut oil and linseed oil in a certain proportion,and the equation was A/c=2.026 2 ×IV-33.07 with the correlation coefficient of 0.999 5. IV determination results of 10 oil samples showed that iodine values measured by the proposed method(IVIR) were in accordance with those examined by the national standard method(IVGB). The relationship between IVIRand IVGBwas IVIR=1.004 ×IVGB-1.39 with a correlation coefficient of 0.997 8,which indicating the presented method could be used for the rapid determination of IVs of edible oils.