红外光谱与化学计量学结合成为植物油鉴定的热门方法, 这种结合目前都基于植物油红外光谱, 提取了植物油主成分可皂化物的红外光谱信息未有效提取植物油微量成分不皂化物的信息, 所构建的植物油鉴定模型的敏感性仍有待提高。 不皂化物特征性强, 为有效获取其红外光谱, 需要预先分离富集, 现有的植物油不皂化物分离富集方法操作过程繁琐、 耗时, 批量样本基本无法采用这种方法。 采用增加皂化液碱度、 超声加热皂化的方法提高植物油皂化效率, 缩短皂化时间。 在提高皂化速度的基础上, 通过①合理配置正己烷、 乙醇及水的比例形成易分层体系; ②将有机溶剂多次提取改为一次提取; ③特别是采用首次研制的专用固相萃取小柱, 一次性快速去除有机相中残余碱性物质和水, 大大缩短不皂化物提取时间。 不皂化物分离富集时间从国标法的约2～3 h缩短至本法的约20 min。 新建的不皂化物分离富集方法有很好的稳定性, 同一样本不同人员分别制样, 得到的不皂化物红外光谱相同, 可以保证一个样品一种光谱。 该方法的建立不仅解决了基于不皂化物红外光谱结合化学计量学构建植物油鉴定模型的关键技术问题, 还为色谱与色质联用技术测定植物油不皂化物的快速样品前处理创造前景。 采用所建立的植物油不皂化物快速分离富集方法, 提取五个不同品牌的芝麻油和五个不同品牌玉米油不皂化物, 并采集它们的红外光谱, 实验数据表明: 红外光谱几乎完全相同的芝麻油与玉米油其不皂化物红外光谱有非常大的差异。 可以预测, 在植物油红外光谱基础上, 结合其不皂化物红外光谱数据, 将可以大大提高某些植物油(如芝麻油)红外光谱鉴定方法的敏感性。

Infrared spectroscopy combined with chemometrics, has become a popular method for the identification of vegetable oil. However, this combination is currently based on the infrared spectra of vegetable oil. Although the infrared spectra information of the saponifiable of vegetable oil is extracted, the information of unsaponifiable is not effectively extracted. The sensitivity of the constructed vegetable oil identification model still needs to be improved. Unsaponifiable is important characteristic components. In order to effectively obtain their infrared spectra, it is necessary to separate and concentrate it in advance. However, the existing separation and enrichment method is cumbersome and time-consuming, and can’t be adopted for the batch samples of vegetable oil. In this paper, under high alkalinity, instead of reflux heating ultrasonic heating, was used to shorten the saponification time. On this basis, through ① the reasonable ratio of n-hexane, ethanol and water to form an easy layering system; ② one extraction replacing multiple extractions; ③ designing and developing a dedicated solid phase extraction small column to rapid remove residual alkaline substance and water in the organic phase at one time, the extraction time of unsaponifiable was shortened greatly. The time of separation and enrichment was shortened from about 2~3 hours with the national standard method to about 20 minutes with the newly established method. The new method has good stability. The same sample was prepared by different people, and their infrared spectra were the same, which could ensure the same infrared spectra for one sample. The establishment of this method not only solves the key technical problems of constructing a model of vegetable oil identification based on infrared spectra of unsaponifiable combined with chemometrics but also creates a prospect for rapid sample preparation of unsaponifiable by chromatography/hyphenated chromatography. Using the rapid separation and enrichment method to unsaponifiable of five different brands of sesame oil and five different brands corn oil were extracted, and their spectra were collected. The experimental result shows that there is a great difference between infrared spectra of unsaponifiable of sesame oil and that of corn oil, although infrared spectra of sesame oil and corn oil are almost the same. It can be predicted that the infrared spectra of vegetable oils can be combined with their unsaponifiable infrared spectra to greatly improve the sensitivity of identification methods for some kinds of vegetable oil such as sesame oil.