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Queen's University
ENCH 213
Diane Beauchemin

Atomic spectroscopy • Flame atomic absorption spectroscopy (FAAS) • Graphite furnace atomic absorption spectroscopy (GFAAS) • Inductively coupled plasma atomic emission spectroscopy (ICP-AES) • ICP mass spectrometry (ICP-MS) Basic principles • everything is first atomized • lowest allowed excited state is called resonance transition ◦ most probable In atomic emission spectroscopy, it is desirable to have a high concentration of the element in the form of a) atoms in the ground state. b) atoms in the excited state. c) ions. A higher temperature in the atomizer would a) be a benefit in atomic absorption. b) be a benefit in atomic emission. c) have a negative effect on both atomic absorption and atomic emission. Implications of atomisation • no vibrational level involved • narrow line peaks (<0.01 nm) result from transition between electronic levels • less interference than in molecular spectroscopy • elemental spectrum (fingerprint of each element) ◦ atomic spectrum can be used to identify the elements present Line spectra are emitted by a) Hot solids b) Excited polyatomic molecules c) Molecules in the ground electronic state d) Excited atoms and monatomic ions Basic components for AES Most common:ICP Heat ← → most commonis nebuliser spray chamber:transforms sltninto aerosol → usuallyinsolution Basic components for AAS Most common:flame or graphite furnace → usuallyinsolution Basic components for AFS o → at 90 to atomizer b/c onlyneed to excite, not go through Processes involved and effect of residence time in atomizer Ca +(g)+ Cl-(g)-heat- Achille’s heel of atomic spectroscopy • conversion of a solution into an aerosol using a thin capillary ◦ easy to clog (dust, particles,…) ◦ difficult to unclog ->FILTER SOLUTIONS • aerosol = mixture of droplets of various sizes ◦ only droplets with dia < 10 µm (ideally 1-2 µm) r
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