Surface Desorption Atmospheric Pressure Chemical Ionization Mass Spectrometry For Raw Meat Quality And Decayed Tooth Analysis

Developing a fast, green,non-destructive and in-situ detecting technique is now a new trend in analytical industry. Mass spectrometry is widely used as an analytical characterization technique due to its high sensitivity, high throughput, and high selectivity, especially after the emergence of ambient mass spectrometry, which has the ability to record mass spectra directly from natural complex samples, without corresponding processing of sample pretreatment. Surface desorption atmospheric pressure chemical ionization(DAPCI), as one of the ambient ionization technique, is of interest for complex samples due to its non-pollution, low destruction, gasless and solvent free, can analyze samples without any processing of pretreatments directly. In this study, the novel methods based on DAPCI-MS are established for the direct analysis of raw meat and tooth samples.The main research contents of this thesis includes as follows:1. The analysis of freshness evaluation for pork using DAPCI-MS. DAPCI has been established for fast identification of pork freshness. The degration chemicals, representative for freshness, in pork samples were determined directly. PCA and CA were applied to probe the differentiation for pork freshness and reproducibility of the analytical method. The results show that the 8 days’ mass spectral fingerprints of the sample set was divided into three categories, the first class is the mass spectra of the first two days, the second class is the mass spectra of 3~6 days, and the third class is the mass spectra of after two days. The experimental results show that DAPCI-MS is an important tool for rapid analysis of highly complex viscous samples such as raw meat samples, providing potential applications in food safety analysis.2. The analysis of adulteration meat using DAPCI-MS. 4 raw meat samples and 3 adulteration meat samples were selected for the DAPCI-MS analysis, and the MS data of them were analyzed by PCA, results show that the adulteration meat can be discriminated succesfully. Then test the accuracy of the three-dimensional model by unknown raw meat samples. The experimental results show that DAPCI-MS is a fast analytical technique for complex samples.3. Micro-area analysis of tooth surface using DAPCI-MS. A novel analytical platform based on a nanoliter needle for sampling and DAPCI-MS for analysis was developed for the direct, fast, and micro-area analysis of different parts of a human tooth, including cavity, cavity edge, tooth cusp, and tooth sulcus. The results showed that the mass spectra from the four sampling spots on the same tooth were different, and that DAPCI-MS detected lactic acid, phenylacetic acid, pyruvic acid, and propanoic acid which were confirmed using MS/MS. PCA of the mass spectral data successfully differentiated the different sampling spots, levels of tooth decay, and levels of gum disease. Therefore, our nano-DAPCI-MS approach provides a promising way for micro-area analysis with fast, minimal pretreatment sampling, enabling rapid, simple, and reliable surface MS investigation.