建立了基于负二阶导数红外光谱的反式脂肪酸的快速测定方法.以三反油酸甘油酯和三油酸甘油酯混合标样系列为校正集,使用带有水平衰减全反射(HATR)附件的傅里叶变换红外光谱仪采集校正集样品在1 050～900 cm-1波段范围的吸收光谱,求二阶导数,乘以-10 000,得负二阶导数谱(- 2D - HATR -FTIR).以970～ 960 cm -1波段范围的最大峰高为X轴,以三反油酸甘油酯含量为Y轴,构建定标方程为y=0.348 8X-0.918 5,相关系数0.999 5.在0.5％～60％范围,验证集样品反式脂肪酸含量预测值与实际指定值显著相关,验证相关系数0.999 0,相对残差的绝对值小于10％,表明方法定标模型预测性能良好.方法检测下限达0.5％,改善了现有红外光谱法的灵敏度,适用于较低含量反式脂肪酸的快速测定.%A rapid method was developed to determine trans fatty acids in foods using negative second derivative horizontal attenuated total reflection Fourier transform infrared spectroscopy ( - 2D - HATR - FTIR). Mixtures of trie-laidin and triolaidin were prepared as a calibration set, the spectra in the region from 1 050 to 900 cm -1 was collected by the Fourier transform infrared spectroscopy with HATR accessory, to obtain a second derivative procedure, which was then multiplied with - 10 000. Calibration plot and regression equation of - 2D - HATR - FTIR band heights versus TFAs were obtained as ( Y = 0. 348 SX - 0. 918 5 ) , with the correlation coefficient of 0. 999 5 , which was thereafter validated by a validation set. Predicted concentrations were significantly correlated with specified concentrations for the TFAs levels in validation set samples at the TFAs levels from 0.5% to 60%. The correlation coefficient reached 0.999 5, while the relative residual was below 10%. It was suggested that calibration model predicted the TFAs levels in samples accurately. The enhanced spectral features of a negative second derivative resolved issues that traditionally limited the sensitivity of the previous infrared methodology. Low levels of TFAs in foods could be rapidly determined with the present method.
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