Direct analysis of micro area on tooth surface by surface desorption atmospheric pressure chemical ionization mass spectrometry

A novel analytical platform based on a nanoliter needle for sampling and surface desorption atmospheric pressure chemistry ionization mass spectrometry(SDAPCI-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 SDAPCI-MS detected lactic acid, pyruvic acid, phenylacetic acid and propanoic acid were confirmed using tandem mass spectrometry(MS/MS). Principal component analysis(PCA) of the mass spectral data successfully differentiated the different sampling spots, levels of tooth decay and levels of gum disease. Therefore, our nano-SDAPCI-MS approach provides a promising way for micro-area analysis with fast, minimal pretreatment sampling, enabling rapid, simple and reliable surface MS investigation.