The Study Of Mass Spectrometry In The Rapid Screening Of Low-quality Edible Oil

Oil analysis is of increasing importance in recent years. Many analytical techniqueshave been applied to oil analysis. Among the techniques available, massspectrometry-based methods are of paramount significance due to the unparallelsensitivity, excellent specificity and the capability to yield rich information. However,time-consuming and laborious sample pretreatments are normally required by theconventional mass spectrometric methods. This is essentially incompatible with the highthroughput demands of inferior quality oils screening.Herein novel methods based on surface desorption atmospheric pressure chemicalionization mass spectrometry (DAPCI-MS) and extractive electrospray ionization massspectrometry (EESI-MS) have been developed in the current studies for direct analysis ofviscous oil samples. Besides of other merits derived from classic mass spectrometry, theremarkable features of the novel techniques developed here are high throughput analysisfor different types of oil (edible oil, illicit oil, adulterated oil and expired oil) samplesdetection and requiring no sample pretreatment, presenting advantages over other massspectrometry-based methods for oil samples analysis. More systematically, the contentsof this thesis mainly include the following aspects:1. Development of novel techniques for oil samples analysis. In our lab, DAPCIsource and EESI source have been fabricated to develop a mass spectrometryplatform for oil samples analysis. The principles, instrumentation andcharacterization of the DAPCI/EESI source have been illustrated with details inall the aspects, building a solid base for fast analysis of oil samples withoutpretreatments.2. By using a home-made surface desorption atmospheric pressure chemicalionization source, different types of oil (edible oil, illicit oil, adulterated oil andexpired oil) samples were directly analyzed by mass spectrometry without any sample pretreatment. The results show that DAPCI-MS can desorbs/ionize thesurface of viscous oil samples, and DAPCI-MS fingerprints of different types ofoil samples were difference. With the application of PCA, illicit oils weresuccessfully differentiated from normal oils. The method developed here isattractive by showing the advantages of no need for sample pretreatment, highsensitivity and high analytical speed (1.0min per sample), and thus provides afast and effective method to screen illicit oils for the sake of food safety.3. For the studying of different types of oil (edible oil, illicit oil, adulterated oil andexpired oil) samples were directly analyzed by extractive electrospray ionizationmass spectrometry. The results showed that EESI-MS is sensitive and capable ofobtaining most of imformation when the optimized spray solvent was selected,and it can ionize viscous oil samples. With the application of PCA, illicit oilswere successfully differentiated from normal oils, oil samples could be withhigh-throughput analysis. It provides a fast, effective and high-throughput methodto screen illicit oils for the field of food safety.4. Mass spectra rapidly recorded by DAPCI-MS were subjected to data processingfor classification mode by back propagation artificial neural networks (BP-ANN)and Chaos Entropy Index (CEI). Neither need time consuming sample separation,nor base on expensive tandem mass spectrometry. As simple operation and highaccuracy, it provides a new idea for the fast ionization massspectrometry(DAPCI、EESI) apply in the field of food safety and public health.