Analytical Chemistry for Technicians Third Edition PDF

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L1519_Frame_FM Page 3 Monday, November 3, 2003 11:26 AM Analytical Chemistry for Technicians Third Edition by John Kenkel Copyright © 2003 CRC Press, LLC L1519_Frame_FM Page 4 Monday, November 3, 2003 11:26 AM Library of Congress Cataloging-in-Publication Data Kenkel, John. Analytical chemistry for...

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Analytical Chemistry for Technicians Third Edition

by John Kenkel

Copyright © 2003 CRC Press, LLC

Library of Congress Cataloging-in-Publication Data Kenkel, John. Analytical chemistry for technicians / by John V. Kenkel. — 3rd ed. p. cm. Includes index. ISBN 1-56670-519-3 (alk. paper) 1. Chemistry, Analytic. 1. Title. QD75.22 .K445 2002 543—dc21

2002029654

This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use. Neither this book nor any part may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, microfilming, and recording, or by any information storage or retrieval system, without prior permission in writing from the publisher. The consent of CRC Press LLC does not extend to copying for general distribution, for promotion, for creating new works, or for resale. Specific permission must be obtained in writing from CRC Press LLC for such copying. The United States Federal Government retains a nonexclusive, nontransferable, irrevocable, royalty-free license to exercise or have exercised for or on behalf of the United States throughout the world all the exclusive rights provided by copyright. Such license does not include the right to see copies or photocopies of this work. This material is based upon work supported by the National Science Foundation under Grant Nos. DUE9751998 and DUE9950042. Direct all inquiries to CRC Press LLC, 2000 N.W. Corporate Blvd., Boca Raton, Florida 33431. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe.

Visit the CRC Press Web site at www.crcpress.com © 2003 by CRC Press LLC Lewis Publishers is an imprint of CRC Press LLC No claim to original U.S. Government works International Standard Book Number 1-56670-519-3 Library of Congress Card Number 2002029654 Printed in the United States of America 2 3 4 5 6 7 8 9 0 Printed on acid-free paper

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Dedication

To my wife, Lois, and daughters Sister Emily, Jeanie, and Laura. For your love, joy, faith, and eternal goodness. May God’s graces and blessings be forever yours.

Copyright © 2003 CRC Press, LLC

Preface

This third edition of Analytical Chemistry for Technicians is the culmination and final product of a series of four projects funded by the National Science Foundation’s Advanced Technological Education Program and two supporting grants from the DuPont Company. The grant funds have enabled me to utilize an almost limitless reservoir of human and other resources in the development and completion of this manuscript and to vastly improve and update the previous edition. A visible example is the CD that accompanies this book. This CD, which was not part of the previous editions, provides, with a touch of humor, a series of real-world scenarios for students to peruse while studying the related topics in the text. One very important resource has been the Voluntary Industry Skill Standards for entry-level chemistry laboratory technicians published by the American Chemical Society in 1997. These standards consist of a large number of competencies that such technicians should acquire in their educational program prior to employment as technicians. While many of these competencies were fortuitously addressed in previous editions, many others were not. It was a resource that I consulted time and time again as the writing proceeded. The grant funds enabled me to enroll in ten American Chemical Society and Pittcon short courses since 1995. Often taught by industrial chemists, these courses were key resources in the manuscript’s development. Another important resource was simply the communications I have had with my colleagues in both industry and academe. Early on, for example, I was able to spend several days at two different DuPont industrial plants to see firsthand what chemical laboratory technicians in these plants do in their jobs. I came away with written notes and mental pictures that were very insightful and useful. I also communicated more regularly with chemists and technicians in my local area, especially when I had specific questions concerning the use of various equipment and techniques in their laboratories. Finally, I have had a network of field testers and reviewers (enabled through the grant funding) for this work. This was a resource that was not available to such an in-depth degree for the previous editions. Some major changes resulted from all of this. New chapters on physical testing methods and bioanalysis, both written by individuals more suited than I am for this task, are perhaps the most noticeable changes. In addition, we provide in this new edition a series of over 50 workplace scenes, sideboxes with photographs of technicians and chemists working with the equipment or performing the techniques discussed in the text at that point. In addition, a laboratory information management system (LIMS) has been created for students to use when they perform the experiments in the text. Besides these, there have been numerous consolidations, additions, expansions, and deletions of many other topics. I am confident that the product you now hold in your hands and the accompanying support material is the most up-to-date and appropriate tool that I am personally capable of providing for your analytical chemistry educational needs.

John Kenkel Southeast Community College Lincoln, Nebraska

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Acknowledgments

Partial support for this work was provided by the National Science Foundation’s Advanced Technological Education (ATE) Program through grant DUE9950042. Partial support was also provided by the DuPont Company through their Aid to Education Program. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation (NSF) or the DuPont Company. This book is the major product of the ATE project funded by NSF. The following individuals were fully dedicated to assisting with this project, often in two or more categories, and contributed significantly and untiringly to the book and associated products: Paul Kelter, University of North Carolina–Greensboro (UNCG) John Amend, Montana State University Kirk Hunter, Texas State Technical College–Waco Onofrio Gaglione, New York City Technical College (CUNY), retired Don Mumm, Southeast Community College–Lincoln Ken Chapman, Cardinal Workforce Developers, LLC Paul Grutsch, Athens Area Technical College Susan Marine, Miami University Middletown Karen Wosczyna-Birch, Tunxis Community College Janet Johannessen, County College of Morris Bill McLaughlin, University of Nebraska–Lincoln Connie Murphy, The Dow Chemical Company Sue Rutledge, Southeast Community College The following gave some assistance to one or more of the aspects of the project, including field testing, reviewing, workshop participation, experiment development, serving on the National Visiting Committee, etc.: Ildy Boer, County College of Morris David Baker, Delta College Gunay Ozkan, Community College of Southern Nevada Ray Turner, Roxbury Community College Pat Cunnif, Prince George’s Community College Fran Waller, Air Products and Chemicals Dan Martin, LABSAF Consulting Joe Rosen, New York City Technical College (CUNY) Robert Hofstader, formerly of the American Chemical Society Marc Connelly, formerly of the American Chemical Society Naresh Handagama, Pellissippi State Technical College

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Linda Sellers-Hann, Del Mar College Jon Schwedler, ITT Technical Institute A special acknowledgment goes to my artist David Jané, whose expertise was very important to the project. Students at the University of North Carolina–Greensboro and at the University of Nebraska–Lincoln also assisted with the project, and students at Southeast Community College endured drafts of the book as a course textbook and offered corrections and inspired content revisions and additions. Many people, too numerous to name, assisted with the acquisition of the workplace scenes, including those pictured in the scenes and others. The personnel at the National Science Foundation deserve particular recognition. These include Frank Settle, who influenced the direction of the project early on; Vicki Bragin, program officer for most of the grant period; Iraj Nejad, who served during the final year of the project; and Liz Teles, who has directed the ATE Program from the beginning. Special acknowledgment also goes to the personnel at CRC Press/Lewis Publishers for their support and hard work on behalf of this and past projects. Finally, the author wishes to acknowledge his family, to whom the book is dedicated, for the love and understanding so graciously given during the entire writing period and the Divine Master for the gifts and talents so freely bestowed.

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The Author

John Kenkel is a chemistry instructor at Southeast Community College (SCC) in Lincoln, Nebraska. Throughout his 25-year career at SCC, he has been directly involved in the education of chemistry-based laboratory technicians in a vocational program presently named Laboratory Science Technology. He has also been heavily involved in chemistry-based laboratory technician education on a national scale, having served on a number of American Chemical Society (ACS) committees, including the Committee on Technician Activities and the Coordinating Committee for the Voluntary Industry Standards project. In addition to these, he has served a 5-year term on the ACS Committee on Chemistry in the Two-Year College, the committee that organizes the two-year college chemistry consortium conferences. He was the chair of this committee in 1996. Mr. Kenkel has authored several popular textbooks for chemistry-based technician education. Two editions of Analytical Chemistry for Technicians preceded this current edition, the first published in 1988 and the second in 1994. In addition, he has authored four other books: Chemistry: An Industry-Based Introduction and Chemistry: An Industry-Based Laboratory Manual, both published in 2000–2001; Analytical Chemistry Refresher Manual, published in 1992; and A Primer on Quality in the Analytical Laboratory, published in 2000. All were published through CRC Press/Lewis Publishers. Mr. Kenkel has been the principal investigator for a series of curriculum development project grants funded by the National Science Foundation’s Advanced Technological Education Program, from which four of his seven books evolved. He has also authored or coauthored four articles on the curriculum work in recent issues of the Journal of Chemical Education and has presented this work at more than twenty conferences since 1994. In 1996, Mr. Kenkel won the prestigious National Responsible Care Catalyst Award for excellence in chemistry teaching, sponsored by the Chemical Manufacturer’s Association. He has a master’s degree in chemistry from the University of Texas in Austin (1972) and a bachelor’s degree in chemistry from Iowa State University (1970). His research at the University of Texas was directed by Professor Allen Bard. He was employed as a chemist from 1973 to 1977 at Rockwell International’s Science Center in Thousand Oaks, California.

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Safety in the Analytical Laboratory

The analytical chemistry laboratory is a very safe place to work. However, that is not to say that the laboratory is free of hazards. The dangers associated with contact with hazardous chemicals, flames, etc., are very well documented, and as a result, laboratories are constructed and procedures are carried out with these dangers in mind. Hazardous chemical fumes are, for example, vented into the outdoor atmosphere with the use of fume hoods. Safety showers for diluting spills of concentrated acids on clothing are now commonplace. Eyewash stations are strategically located for the immediate washing of one’s eyes in the event of accidental contact of a hazardous chemical with the eyes. Fire blankets, extinguishers, and sprinkler systems are also located in and around analytical laboratories for immediately extinguishing flames and fires. Also, a variety of safety gear, such as safety glasses, aprons, and shields, is available. There is never a good excuse for personal injury in a well-equipped laboratory where well-informed analysts are working. While the pieces of equipment mentioned above are now commonplace, it remains for the analysts to be well informed of potential dangers and of appropriate safety measures. To this end, we list below some safety tips of which any laboratory worker must be aware. This list should be studied carefully by all students who have chosen to enroll in an analytical chemistry course. This is not intended to be a complete list, however. Students should consult with their instructor in order to establish safety ground rules for the particular laboratory in which they will be working. Total awareness of hazards and dangers and what to do in case of an accident is the responsibility of the student and the instructor. 1. Safety glasses must be worn at all times by students and instructors. Visitors to the lab must be appropriately warned and safety glasses made available to them. 2. Fume hoods must be used when working with chemicals that may produce hazardous fumes. 3. The location of fire extinguishers, safety showers, and eyewash stations must be known. 4. All laboratory workers must know how and when to use the items listed in number 3. 5. There must be no unsupervised or unauthorized work going on in the laboratory. 6. A laboratory is never a place for practical jokes or pranks. 7. The toxicity of all the chemicals you will be working with must be known. Consult the instructor, material safety data sheets (MSDSs), safety charts, and container labels for safety information about specific chemicals. Recently, many common organic chemicals, such as benzene, carbon tetrachloride, and chloroform, have been deemed unsafe. 8. Eating, drinking, or smoking in the laboratory is never allowed. Never use laboratory containers (beakers or flasks) to drink beverages. 9. Shoes (not open-toed) must always be worn; hazardous chemicals may be spilled on the floor or feet. 10. Long hair should always be tied back.

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11. Mouth pipetting is never allowed. 12. Cuts and burns must be immediately treated. Use ice on new burns and consult a doctor for serious cuts. 13. In the event of acid spilling on one’s person, flush thoroughly with water immediately. Be aware that acid–water mixtures will produce heat. Removing clothing from the affected area while water flushing may be important, so as to not trap hot acid–water mixtures against the skin. Acids or acid–water mixtures can cause very serious burns if left in contact with skin, even if only for a very short period of time. 14. Weak acids (such as citric acid) should be used to neutralize base spills, and weak bases (such as sodium carbonate) should be used to neutralize acid spills. Solutions of these should be readily available in the lab in case of emergency. 15. Dispose of all waste chemicals from the experiments according to your instructor’s directions. 16. In the event of an accident, report immediately to your instructor, regardless of how minor you perceive it to be. 17. Always be watchful and considerate of others working in the laboratory. It is important not to jeopardize their safety or yours. 18. Always use equipment that is in good condition. Any piece of glassware that is cracked or chipped should be discarded and replaced. It is impossible to foresee all possible hazards that may manifest themselves in an analytical laboratory. Therefore, it is very important for all students to listen closely to their instructor and obey the rules of their particular laboratory in order to avoid injury. Neither the author of this text nor its publisher assumes any responsibility whatsoever in the event of injury.

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Contents

1

Introduction to Analytical Science

2

Sampling and Sample Preparation

1.1 1.2 1.3 1.4 1.5 1.6 1.7

Analytical Science Defined ......................................................................................................... 1 Classifications of Analysis........................................................................................................... 2 The Sample .................................................................................................................................. 3 The Analytical Strategy ............................................................................................................... 4 Analytical Technique and Skills ................................................................................................. 4 The Laboratory Notebook .......................................................................................................... 7 Errors, Statistics, and Statistical Control ................................................................................... 9 1.7.1 Errors ............................................................................................................................... 9 1.7.2 Elementary Statistics ..................................................................................................... 10 1.7.3 Normal Distribution..................................................................................................... 11 1.7.4 Precision, Accuracy, and Calibration........................................................................... 12 1.7.5 Statistical Control ......................................................................................................... 13 Experiments ......................................................................................................................................... 14 Experiment 1: Assuring the Quality of Weight Measurements.............................................. 14 Experiment 2: Weight Uniformity of Dosing Units................................................................ 15 Questions and Problems ..................................................................................................................... 15

2.1 2.2 2.3 2.4

2.5

2.6

Introduction .............................................................................................................................. 17 Obtaining the Sample ............................................................................................................... 17 Statistics of Sampling ................................................................................................................ 19 Sample Handling....................................................................................................................... 20 2.4.1 Chain of Custody .......................................................................................................... 20 2.4.2 Maintaining Sample Integrity ...................................................................................... 20 Sample Preparation: Solid Materials........................................................................................ 22 2.5.1 Particle Size Reduction ................................................................................................. 23 2.5.2 Sample Homogenization and Division........................................................................ 23 2.5.3 Solid–Liquid Extraction...