by RD Beaty · 1993 · Cited by 257 — The science of atomic spectroscopy has yielded three techniques for analytical use: atomic emission, atomic absorption, and atomic fluorescence. In order to un-.
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Copyright © 1993 by The Perkin-Elmer Corporation, Norwalk, CT, U.S.A. Allrights reserved. Printed in the United States of America. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, with-out the prior written permission of the publisher.ii

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ABOUT THE AUTHORSRichard D. BeatySince receiving his Ph.D. degree in chemistry from the University of Missouri-Rolla, Richard Beaty has maintained an increasing involvement in the field of laboratory instrumentation and computerization. In 1972, he joined Perkin-Elmer, where he held a variety of technical support and marketing positions in atomicspectroscopy. In 1986, he founded Telecation Associates, a consulting companywhose mission was to provide formalized training and problem solving for the analytical laboratory. He later became President and Chief Executive Officer of Telecation, Inc., a company providing PC-based software for laboratory automat-ion and computerization.Jack D. KerberJack Kerber is a graduate of the Massachusetts Institute of Technology. He hasbeen actively involved with atomic spectrometry since 1963. In 1965 he becamePerkin-Elmer™s first field Product Specialist in atomic absorption, supporting ana-lysts in the western United States and Canada. Since relocating to Perkin-Elmer™scorporate headquarters in 1969, he has held a variety of marketing support and sales and product management positions. He is currently Director of Atomic Ab-sorption Marketing for North and Latin America.iii

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ACKNOWLEDGEMENTThe authors gratefully acknowledge the contributions and assistance they have re-ceived from their colleagues in preparing this book. We are particularly indebtedto Glen Carnrick, Frank Fernandez, John McCaffrey, Susan McIntosh, CharlesSchneider and Jane Sebestyen of The Perkin-Elmer Corporation for the hours theyspent proofreading the several revisions and to Jorn Baasner, Horst Schulze, Ger-hard Schlemmer, Werner Schrader and Ian Shuttler of BodenseewerkPerkin-Elmer GmbH for their invaluable input on Zeeman-effect background cor-rection and graphite furnace atomic absorption techniques. iv

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TABLE OF CONTENTS1 Theoretical Concepts and Definitions The Atom and Atomic Spectroscopy . . . . . . . . . . . . . . . 1-1Atomic Absorption Process . . . . . . . . . . . . . . . . . . . . 1-3 Quantitative Analysis by Atomic Absorption . . . . . . . . . . . 1-4 Characteristic Concentration and Detection Limits . . . . . . . . 1-6Characteristic Concentration . . . . . . . . . . . . . . . . . 1-7Detection Limits . . . . . . . . . . . . . . . . . . . . . . . . 1-72 Atomic Absorption InstrumentationThe Basic Components . . . . . . . . . . . . . . . . . . . . . . . 2-1 AA Light Sources . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2 The Hollow Cathode Lamp . . . . . . . . . . . . . . . . . . 2-3The Electrodeless Discharge Lamp . . . . . . . . . . . . . . 2-6Optical ConsiderationsPhotometers . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7Single-beam Photometers . . . . . . . . . . . . . . . . . . . 2-7Double-beam Photometers . . . . . . . . . . . . . . . . . . 2-8Alternative Photometer Designs . . . . . . . . . . . . . . . 2-9Optics and the Monochromator System . . . . . . . . . . . 2-10The Atomic Absorption AtomizerPre-mix Burner System . . . . . . . . . . . . . . . . . . . . 2-14Impact Devices . . . . . . . . . . . . . . . . . . . . . . . . 2-15Nebulizers, Burner Heads and Mounting Systems . . . . . . 2-16ElectronicsPrecision in Atomic Absorption Measurements . . . . . . . 2-17Calibration of the Spectrometer . . . . . . . . . . . . . . . 2-18Automation of Atomic AbsorptionAutomated Instruments and Sample Changers . . . . . . . . 2-19Automated Sample Preparation . . . . . . . . . . . . . . . . 2-20The Stand-alone Computer and Atomic Absorption . . . . . 2-203 Control of Analytical InterferencesThe Flame Process . . . . . . . . . . . . . . . . . . . . . . . . . 3-1Nonspectral Interferences . . . . . . . . . . . . . . . . . . . . . 3-3Matrix Interference . . . . . . . . . . . . . . . . . . . . . . 3-3 Method of Standard Additions . . . . . . . . . . . . . . . . 3-4Chemical Interference . . . . . . . . . . . . . . . . . . . . . 3-5v

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3 Control of Analytical Interferences (continued)Ionization Interference . . . . . . . . . . . . . . . . . . . . 3-6Spectral InterferencesBackground Absorption . . . . . . . . . . . . . . . . . . . . 3-7Continuum Source Background Correction . . . . . . . . . 3-8Introduction to Zeeman Background Correction . . . . . . . 3-11Other Spectral Interferences . . . . . . . . . . . . . . . . . 3-14Interference Summary . . . . . . . . . . . . . . . . . . . . . . . 3-144 High Sensitivity Sampling SystemsLimitations to Flame AA Sensitivity . . . . . . . . . . . . . . . 4-1The Cold Vapor Mercury TechniquePrinciple . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2Advantages of the Cold Vapor Technique . . . . . . . . . . 4-2Limitations of the Cold Vapor Technique . . . . . . . . . . 4-3The Hydride Generation TechniquePrinciple . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3Advantages of the Hydride Technique . . . . . . . . . . . . 4-4Disadvantages of the Hydride Technique . . . . . . . . . . 4-4 Graphite Furnace Atomic AbsorptionPrinciple . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5Advantages of the Graphite Furnace Technique . . . . . . . 4-55 Introduction to Graphite Furnace Atomic AbsorptionConsiderations in Ultra Trace AnalysisPerformance Criteria . . . . . . . . . . . . . . . . . . . . . 5-1Graphite Furnace Applications . . . . . . . . . . . . . . . . 5-2Components of the Graphite Furnace SystemThe Graphite Furnace Atomizer . . . . . . . . . . . . . . . 5-2The Graphite Furnace Power Supply and Programmer . . . 5-5Summary of a Graphite Furnace Analysis . . . . . . . . . . . . . 5-5Sample Size . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6 The Drying Step . . . . . . . . . . . . . . . . . . . . . . . . 5-7The Pyrolysis Step . . . . . . . . . . . . . . . . . . . . . . 5-8The Pre-atomization Cool Down Step . . . . . . . . . . . . 5-8The Atomization Step . . . . . . . . . . . . . . . . . . . . . 5-8The Clean Out and Cool Down Step . . . . . . . . . . . . . 5-9Fast Furnace Analysis . . . . . . . . . . . . . . . . . . . . . . . 5-9vi

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