Espectrofotometria

Concepts, Instrumentation and Techniques in Atomic Absorption Spectrophotometry
Richard D. Beaty and Jack D. Kerber

Second Edition

THE PERKIN-ELMER CORPORATION

Copyright © 1993 by The Perkin-Elmer Corporation, Norwalk, CT, U.S.A. All rights reserved. Printed in the United States of America. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, inany form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher.

ii

ABOUT THE AUTHORS Richard D. Beaty
Since receiving his Ph.D. degree in chemistry from the University of MissouriRolla, Richard Beaty has maintained an increasing involvement in the field of laboratory instrumentation and computerization. In1972, he joined Perkin-Elmer, where he held a variety of technical support and marketing positions in atomic spectroscopy. In 1986, he founded Telecation Associates, a consulting company whose 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 forlaboratory automation and computerization.

Jack D. Kerber
Jack Kerber is a graduate of the Massachusetts Institute of Technology. He has been actively involved with atomic spectrometry since 1963. In 1965 he became Perkin-Elmer’s first field Product Specialist in atomic absorption, supporting analysts in the western United States and Canada. Since relocating to Perkin-Elmer’s corporateheadquarters in 1969, he has held a variety of marketing support and sales and product management positions. He is currently Director of Atomic Absorption Marketing for North and Latin America.

iii

ACKNOWLEDGEMENT
The authors gratefully acknowledge the contributions and assistance they have received from their colleagues in preparing this book. We are particularly indebted to Glen Carnrick, FrankFernandez, John McCaffrey, Susan McIntosh, Charles Schneider and Jane Sebestyen of The Perkin-Elmer Corporation for the hours they spent proofreading the several revisions and to Jorn Baasner, Horst Schulze, Gerhard Schlemmer, Werner Schrader and Ian Shuttler of Bodenseewerk Perkin-Elmer GmbH for their invaluable input on Zeeman-effect background correction and graphite furnace atomic absorptiontechniques.

iv

TABLE OF CONTENTS
1 Theoretical Concepts and Definitions

The Atom and Atomic Spectroscopy . . . . . . . Atomic Absorption Process . . . . . . . . . . . . Quantitative Analysis by Atomic Absorption . . . Characteristic Concentration and Detection Limits Characteristic Concentration . . . . . . . . . Detection Limits . . . . . . . . . . . . . . . .
2 Atomic AbsorptionInstrumentation

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

. . . . . .

1-1 1-3 1-4 1-6 1-7 1-7

The Basic Components . . . . . . . . . . . . . . . . . . AA Light Sources . . . . . . . . . . . . . . . . . . . . . The Hollow Cathode Lamp . . . . . . . . . . . . . The Electrodeless Discharge Lamp . . . . . . . . . OpticalConsiderations Photometers . . . . . . . . . . . . . . . . . . . . . Single-beam Photometers . . . . . . . . . . . . . . Double-beam Photometers . . . . . . . . . . . . . Alternative Photometer Designs . . . . . . . . . . Optics and the Monochromator System . . . . . . The Atomic Absorption Atomizer Pre-mix Burner System . . . . . . . . . . . . . . . Impact Devices . . . . . . . . . . . . . . . . . . .Nebulizers, Burner Heads and Mounting Systems . Electronics Precision in Atomic Absorption Measurements . . Calibration of the Spectrometer . . . . . . . . . . Automation of Atomic Absorption Automated Instruments and Sample Changers . . . Automated Sample Preparation . . . . . . . . . . . The Stand-alone Computer and Atomic Absorption
3 Control of Analytical Interferences

. . . . . . . . .

. ....