C30J_2010_lecture_5 - C30J Chemical Analysis II Analytical...

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Unformatted text preview: C30J Chemical Analysis II Analytical Atomic Spectrometry Lecture 5 March 26, 2010 Practical AAS: Instrumental Components External Radiation Source Atomizer Wavelength Selector Detector Sample Introduction System 1 2 3 4 5 Detectors Photomultiplier Tube (PMT) • Photoemissive cathode produces electrons when struck by electromagnetic radiation • Additional electrodes called dynodes held at increasingly more positive potential than cathode • Electric pulse recorded at anode for each incident photon Detectors Photomultiplier Tube (PMT) Anode current α Intensity window Newer Photon Detectors: Charge Transfer Devices • Charge Coupled Devices (CCDs) • Charge Injection Devices (CIDs) • Multichannel devices • Two dimensional array of individual transducers (pixels) • Photons generate charge which is collected and read Practical AAS: Instrumental Components External Radiation Source Atomizer Wavelength Selector Detector Sample Introduction System 1 2 3 4 5 • Emitted radiation from atomizer • Non-analyte absorption of external source radiation Two problems in AAS • Source Modulation • Background Correction Two corrective measures Interference from emitted radiation...
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This note was uploaded on 02/23/2011 for the course CHEMISTRY C30J taught by Professor Vaugnrattray during the Spring '11 term at University of the West Indies at Mona.

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C30J_2010_lecture_5 - C30J Chemical Analysis II Analytical...

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