建立衰减全反射-傅里叶变换红外光谱法测定食用油的过氧化值

Establish determination of peroxide values of edible oils by ATR-FTIR spectroscopy

为减少食用油过氧化值(POV)测定过程中化学试剂的使用量,基于油脂中的过氧化物与三苯基膦(TPP)间的定量反应,通过测定反应产物三苯基氧膦(TPPO)位于542 cm^(-1)处的红外特征吸收峰,建立简单的POV测定方法。将1 mL食用油与40μL TPP的丙酮溶液振荡混合,使用衰减全反射-傅里叶变换红外光谱仪测定样品反应后的红外光谱,确定TPPO在542 cm^(-1)处的特征吸收峰的峰高,计算油脂的POV。结果表明:TPPO在542 cm^(-1)处的特征吸收峰的峰高D(542)与油脂过氧化值间存在良好的线性关系,28种食用油POV的红外光谱测定结果与国标碘量法测定结果一致,11次平行测定结果的相对标准偏差为2.91%,方法的检出限为0.61 mmol/kg。建立的测定方法具有操作简单、有机试剂使用量小、对实验人员的技术要求低等优点,适合油脂POV的快速筛查。

In order to reduce the amount of chemical reagents used for determining the peroxide value(POV)of edible oil,attenuated total reflection Fourier transform infrared spectroscopy was adopted to determine POV of edible oil.The peroxides in oil react with triphenylphosphine(TPP)to produce triphenylphosphine oxide(TPPO)and there is a characteristic absorption peak at 542 cm^(-1)in the infrared spectrum of TPPO.In this work,1 mL edible oil was mixed with 40μL TPP solution in acetone and the infrared spectrum of the sample was measured by an attenuated total reflection-Fourier transformation infrared spectrometer equipped with a diamond single-bounce ATR accessory.The peak height of the characteristic absorption peak of TPPO at 542 cm^(-1),A(542),was determined,and POV of the edible oil was calculated.The results showed that the prepared TPP solution remained stable within 48 hours and was not oxidized by air,which would not cause a wrong result.There was a good linear relationship between A(542)and POV with a correlation coefficient(R^(2))of 0.9962.The peroxide values of 28 edible oils determined by ATRFTIR and national standard methods were consistent and the correlation coefficient(R^(2))between POV determined by ATR-FTIR method and iodometric method was 0.9860,indicating that the present method can be used as an alternative to iodometric method for a rapid determination of POVs of edible oils.The relative standard deviation of the predicted values of 11 replicates was estimated to be 2.91%,and the detection limit of the method was 0.61 mmol/kg.The proposed method has the advantages of simple oper-ation,low amount of organic reagent and low technical requirements for laboratory personnel,which is suitable for fast screening of POV.