Tiêu đề Edited final New Mass Spectroscopy 22012018.pdf ✅

Dr Nileshkumar Vala Mass Spectroscopy Shree P M Patel college of PG Studies & Research in Science, Anand. 1 Mass Spectroscopy Theory & Applications in Structure assignment to Organic Compounds By Dr. Nileshkumar Vala Shree P M Patel college of PG Studies & Research in Science, Anand
Dr Nileshkumar Vala Mass Spectroscopy Shree P M Patel college of PG Studies & Research in Science, Anand. 2 Mass Spectroscopy Spectroscopy – Associated with absorption of electromagnetic radiation (IR, UV, NMR). In Mass Spectroscopy – No such absorption of electromagnetic radiation, hence it is not true spectroscopy. However Mass spectrum is a plot of different peaks with their position (m/z value) vs their intensities (relative abundance). Therefore it is similar to other spectral study (IR, UV, NMR – position and intensity). Use of Mass Spectroscopy: What is studied by Mass Spectroscopy? 1. Determination of accurate molecular weight. 2. Fragmentation in organic molecules – determination of structural features in organic compounds. 3. Determination of molecular formula. Production of Mass Spectra: How Mass spectrum is obtained? 1. Electron Impact (EI) ionization 2. Chemical Ionization (CI) 3. Field Desorption (FD) 4. Fast Atom Bombardment (FAB) 5. Electronspray Ionization (ESI) 6. Matrix Assisted Laser Desorption/Ionization (MALDI) EI is most frequently used.
Dr Nileshkumar Vala Mass Spectroscopy Shree P M Patel college of PG Studies & Research in Science, Anand. 3 1. Electron Impact (EI) ionization EI method: M e - beam 70 ev M Radical ion Molecular ion M Fragmentation Mixture of ions with different m / z values Magnetic Field variation Separated out m / z high comes first increase in Bo m / z 1000 comes later A scan of spectrum from mass 12-500 performed in seconds. EI instruments: Two types : Single focusing (only magnetic field) Double focusing (electric field and magnetic field) Low resolution : Unit resolution accurately measures mass up to 1 unit. High resolution : measures mass up to four decimal points accurately.