化学分析和仪器分析.PPT

Raman spectra are molecule specific Spectra contain information about vibrational modes of the molecule Spectra have sharp features, allowing identification of the molecule by its spectrum Raman Spectrum of Cholesterol Magnetic Resonance Imaging: MRI An MR image is (usually) a map of water protons, with intensity determined by local physical environment Contrast and image quality are determined by Pulse sequence Field strength Shim quality Acquisition time What is a Mass Spectrometer? A Mass Spectrometer is a machine that weighs molecules ! What is a Mass Spectrometer? A Mass Spectrometer is a machine that weighs molecules ! What is a Mass Spectrometer? A Mass Spectrometer is a machine that weighs molecules ! What is a Mass Spectrometer? A Mass Spectrometer is a machine that weighs molecules ! Multiple Charged Spectrum of ESI Tandem Mass Spectrometry MS, MS/MS, and MS/MS/MS of TBZ QITMS: Low Cost permits unique applications Note MS/MS might be satisfactory on some columns but the small amount of 174 from the interfering compound will interfere as the column ages. Multiple charging means heavier ions can be analyzed by analyzers with a lower range; also, charge states can be deconvoluted to get a rather good mass for the uncharged species. * 12 units 12 units 8 9 10 11 12 13 14 15 16 Number of counts mass/charge 14 units 8 9 10 11 12 13 14 15 16 Number of counts mass/charge 12 units 8 9 10 11 12 13 14 15 16 Number of counts mass/charge JJ Thomson’s cathode ray tube, 1897 Joseph John Thomson 1906 Physics Nobel Laureate Gas Phase/ Ionize Detector Separate Based on Mass/Charge Sample Why Ionize ? Difficult to manipulate neutral particles on molecular scale. If they are charged, then we can use electric fields to move them around. Mass spectrometry studies ions Mass spectrometers determine mass-to-charge ratio of ions The analysis is performed in the gas phase not in solution Structure can be elucidate