Date: 2009. 4. 9, 5:00 PM Place: Mogam Hall, Bldg 500 - Abstract - The first mass spectrometer (MS) invented by Sir J. J. Thomson in 1907 was built with superimposed electric and magnetic field, which produced parabolic mass spectra. Later, it was further developed by physicists like F. W. Aston, A. J. Dempster, A. O. Nier, E. G. Johnson, J. Mattauch, and R. Herzog to finally see sector-based high resolution MS’s. The year 1953 saw the introduction of quadrupole mass spectrometer (QMS), a type of MS relying on oscillating electric field at radio frequency (RF). This instrument by Paul and Steinwedel has limited resolution but well suited for practical analytical necessities in combination with chromatographic techniques and that it is affordable yet with superb sensitivity. In 1946 Stephens added another way of measuring mass of ionized chemical components from their time-of-flight through a field-free zone after high voltage acceleration, viz., time-of-flight mass spectrometer (TOF-MS). Ions with thermal kinetic energy oscillate at characteristic frequencies, of which the time domain data transform into the mass values after Fourier transformation. This kind of instrumentation was first realized for the ions captured in strong magnetic field by Sommer et. al., in 1949 and is called Fourier transform ion cyclotron resonance MS (FT-ICR MS). Orbitrap, brought in the field by Makarov in 2000, records the intrinsic frequencies of the ions orbiting in strong DC electric field to obtain the mass values. An ion mobility spectrometer (IMS) separates ions in the gas phase based on the difference in the collisional cross-section and boosts up the strength of the MS if combined with it. Electron ionization (EI) developed by Bleakney in 1929 later made it possible to establish standardized 70 eV EI spectral database after decades of research, which has transformed MS into one of the best analytical means both in qualitative and quantitative measures as was foretold by J. J. Thomson in early 20th century. MS is different in that it relies on gas phase chemical reactions unlike the other spectral instruments depending on linear combination of quantum chemical transitions between states whose energy difference is represented by the energy of the photons given off. Therefore, the spectral interpretation requires matching pieces of the analytes. This presentation briefly summarizes this puzzle-like nature of MS both in the hardware and data interpretation with examples.