Mass spectrometry in combination with chemometric data processing has secured a central role in the study of biological systems to comprehensively and simultaneously determine the global metabolite levels in whole organisms and their changes as a consequence of stimuli. With unmatched mass resolution, mass accuracy, and detection sensitivity, linear ion trap -Fourier Transform Orbitrap Mass Spectrometry (LTQ-Orbitrap-MS) has the potential for high throughput metabolomic analysis. Chemometric

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... ls like principal component analysis (PCA) and partial least squares (PLS) have vi Acknowledgements I would like to express my sincere gratitude and deep indebtedness to Dr Dave Watson for offering me the opportunity to carry out research and for his enthusiastic encouragement, invaluable advice and the free academic environment throughout the course of the work. From the first day I started until the last minutes of completion, Dave has been spending a lot of efforts and time on supervising me. Also a tremendous appreciation for support from Markus Bieri of Lonza Ltd, Switzerland. Many appreciations are due to my teachers and collaborators: RuAngelie Edrada-Ebel for her professional mass spectrometry and chemistry knowledge; Blair Johnston for his advanced mathematical and computer knowledge; Prof.