BOOKS
Chemometrics and NMR Spectroscopy Chemometrics. Muhammad A. Sharaf, Deborah Illman, and Bruce R. Kowalski. xi + 332 pp. John Wiley & Sons, 605 Third Ave., New York, N.Y. 10016.1986. $49.95 Reviewed by Roland F. Hirsch, Divi sion of Chemical Sciences, U.S. De partment of Energy, Station G-236, Washington, D.C. 20545
In this monograph the authors survey a cross section of mathematical tech niques used to extract information from measurements. The authors themselves have made substantial con tributions to the development of a subdiscipline of chemistry dealing with this subject, often called chemome trics. Special emphasis is given to those areas with which the authors have been most closely associated, and many of the examples in the book are drawn from their prior publications. Multivariate statistical analysis is the main focus of the book, although other important topics such as experi ment design, signal-to-noise ratio en hancement, calibration, and sampling are not neglected. Considering that the book is just over 300 pages long, the authors were wise not to attempt to cover every topic with equal thorough ness. This means, however, that the treatment of the subject is not as bal anced as could be expected from a fulllength textbook. The authors concentrate on exam ples in analytical chemistry and give illustrations from the other branches of chemistry only infrequently. Quantita tive structure-activity relationships, graph theory, maximum likelihood in ference, and topological analysis are some examples of topics that should be in a book that provides full coverage of chemometrics. The authors provide more than 200 literature references, although unfor
tunately 75% of them are pre-1980. For example, they have noted the often overlooked paper of Steinier, Termonia, and Deltour (Anal. Chem. 1972, 44, 1906), which corrects some of the coefficients in the original widely refer enced paper by Savitzky and Golay on digital filtering (Anal. Chem. 1964, 36, 1627). On the other hand, in chapter 6, "Exploratory Data Analysis," they do not refer to the pioneering work of John Tukey. The book is generally free from typo graphical errors. In one outstanding ex ample of how to lie with statistics it is claimed that a waste treatment process
"The authors themselves have made substantial contributions to the development of (this) subdiscipline of chemistry"
that reduces the mercury content from 18.5 to 18.3 ppm is effective because the ί-test indicates that the "after" mercury content is significantly differ ent from the "before" figure (as indi cated on pp. 35-36). This book can be recommended as a very personal overview of the topic. It is succinct and well written. The reader should recognize, however, that it is not a comprehensive text and that its cov erage of the literature must be supple mented by another more recent compi lation. One such example would be the "Fundamental Reviews" surveys of chemometrics in ANALYTICAL CHEM ISTRY, which are published in evennumbered years.
338 A · ANALYTICAL CHEMISTRY, VOL. 60, NO. 5, MARCH 1, 1988
Modern NMR Spectroscopy: A Guide for Chemists. Jeremy Κ. Μ. Sanders and Brian K. Hunter, xii + 308 pp., Oxford University Press, 200 Madison Ave., New York, N.Y. 10016. $60 Reviewed by Cynthia J. Jameson, De partment of Chemistry, The Universi ty of Illinois at Chicago, 4500 Science and Engineering South, Chicago, III. 60680 The aim of the authors of Modern NMR Spectroscopy is to bridge the communication gap between the chem ist and the spectroscopist. The ap proach is nonmathematical, descrip tive, and pictorial. To illustrate the ideas introduced in the text, the au thors provide original spectra obtained specially for this purpose. Examples in clude spectroscopy of protons, carbon, and less receptive nuclei of interest to inorganic chemists. The authors suc ceed in making high-resolution NMR spectroscopy comprehensible for the average student or chemist. Modern NMR Spectroscopy serves well as a primer, for the authors start from the very beginning, assuming no previous background; they carefully in troduce the language and provide the theoretical basis in descriptive form. The book also includes a large enough repertoire of chemistry problem-solv ing tools for the professional chemist. Out of the bewildering array of pulse sequences and special techniques con tained in the literature, Sanders and Hunter select a working subset of tech niques that are forgiving of the novice in their execution and direct in reveal ing the chemical information carried by the nuclei. Chemists who use NMR spectrosco py need to have an understanding of the theoretical ideas that make NMR techniques work. Cotton's book opened up the world of group theory to chem ists. In a similar way, Sanders and
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Nuclear Magnetic Resonance: General Concepts and Applications. William W. Paudler. xi + 291 pp. John Wiley & Sons, 605 Third Ave., New York, N.Y. 10016.1987. $35
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Paudler states that the purpose of this book is to introduce the reader to NMR without quantum mechanics and "to provide sufficiently detailed informa tion to familiarize the reader with not only the theoretical foundation but the numerous applications of this most powerful technique." This was also the purpose of his earlier book, Nuclear Magnetic Resonance, which was pub lished in 1971. The new book is a re vised and expanded version of the ear lier one. The scope is ambitious and covers all aspects of NMR spectroscopy: highresolution multinuclear NMR of solu tions; chemical exchange and rate pro cesses; NMR relaxation theory; all as pects of Fourier transform (FT)-NMR, including sensitivity enhancement ex periments; two-dimensional FT-NMR; NMR of solids, both wide-line and high-resolution, magic angle spinning experiments; and NMR imaging. The book provides a number of problems and a list of references at the end of each chapter. Given the wide range of material and the fact that the book is only 290 pages long, it is not surprising that the topics are all treated superfi cially. This book is apparently intended as an introductory text for undergraduate students or beginning graduate stu dents, but I cannot recommend it to anyone looking for a clear introduction to NMR spectroscopy. I found the book to be confusing, poorly organized, and, in many places, erroneous. It is possible to cite several examples of confusion and inaccuracy. For in stance, in chapter 1 the concept of spin-lattice relaxation is introduced abruptly with the following equation, ^
Section - ACS. For information contact: Dr. Joseph Zirrolli (303)394-8961 Abstract Deadline March 21, 1988
Reviewed by Thomas C. Farrar, De partment of Chemistry, University of Wisconsin, 1101 University Ave., Madison, Wis. 53706
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340 A · ANALYTICAL CHEMISTRY, VOL. 60, NO. 5, MARCH 1, 1988
= -2W(n
- neq)
where η is defined as the population of nuclei in different spin states. In fact, for a sample of identical nuclei, all with spin 1/2, there are two energy levels and η is the difference in the popula-
BOOKS tions in the two energy levels. The term neq is never defined. Paudler then states that the difference (n — neq) is temperature-dependent and that this temperature dependence may be ac counted for by modifying the given equation to obtain — = -2W(n - neq)0 X e This is nonsensical. No explanations of the quantities (n — neq)o, i, or T\ are given. Also, no explanation is given of how the equation incorporates infor mation about the temperature depen dence of (n — neq). A brief discussion of the various spin-lattice relaxation mechanisms then follows. In the section on dipolar relaxation, Paudler accurately states that carbon nuclei attached to protons relax relatively rapidly. He then tells us that "The adjacency of an atom with a lone pair of electrons (such as a nitro gen atom) is even more efficient in im proving T\ than a bonded proton." This statement is simply wrong, and it exemplifies the many errors that occur throughout the book, demonstrating that Paudler apparently does not un derstand the difference between T\ and T2. The result is a vague and con fusing explanation of relaxation pro cesses. The spin-lattice relaxation time, Γχ, for a carbon bonded solely to a nitrogen is 100 times longer than that of a carbon bonded solely to a single proton because the gyromagnetic ratio for nitrogen, 7N, is 10 times smaller than that for protons, 7 H . This follows because Ti(C) is proportional to Ί\. Ί\, where X is the nucleus bonded to the carbon. The spin-spin relaxation time, Ti, for the carbon may be quite short because of scalar relaxation by a spincoupled nucleus (such as nitrogen) with a small T\ value. In the brief description of chemical shift anisotropy (CSA), we are told, "This contributor to the spin-lattice relaxation process is a readily averaged minimal contributor when the mole cule being examined can rotate freely." Then he says that CSA is effective as a relaxation process in the solid state where molecular motions are slower. Paudler apparently is confused about the difference between the line widths arising from the CSA interaction in liq uids and solids and the CSA as a relax ation mechanism. At fields of 10 Tesla (400-MHz proton frequency) and high er, the CSA relaxation mechanism for carbon usually makes a significant con tribution to the relaxation for liquid samples. The combination of dipolar and CSA relaxation results in some very interesting and useful interfer
ence effects. Numerous reports of these CSA/dipolar interference effects have been reported recently in the chemical literature. The confusion and inaccuracies be come even worse than those cited above when more modern aspects of NMR, such as selectivity enhance ment, two-dimensional FT-NMR, and NMR imaging are discussed. An expla nation of the INEPT experiment is very confusing; the experiment that Paudler apparently is trying to de scribe is the refocused INEPT (or ERNST) experiment. The editor has done a fine job in catching most of the spelling and gram matical errors, but apparently no one bothered to check on the accuracy or clarity of most of the technical discus sions. No check was made on notation. For example, it is customary to use 13C or 15 N; Paudler uses C 13 and N 15 . It is now customary to use B\ and Bo for the rf and dc magnetic fields, respectively; Paudler uses H\ and Ho in the early parts of the book and sometimes switches to Βγ and Br, in the latter part of the book. Most of the references in the book are 20-30 years old. The index is a curi ous collection of items. DEFT is listed twice in the index but is mentioned only in one sentence in the book. Relax ation processes are discussed in many sections of the book, but no listing of T\ or Γ2 is given in the index. There is a single reference in the index to "relax ation time" on page 195. On that page, the only relaxation time mentioned is a quantity, T exp , which is not a relaxation time but a parameter introduced to ac count for the inhomogeneity of the dc magnetic field. One reference is made to spin-lattice relaxation on page 22, and again the author is seen to be con fused about the difference between the terms T\ and T2.
Books Received Chromatography '85. Huba Kalasz and Leslie Ettre, Eds. xv + 695 pp. Akademiai Kiado, P.O. Box 36, Budapest, Hungary. 1986. $66 Analysis of Surface Waters. Hubert Hellmann. 275 pp. Ellis Horwood Lim ited, Market Cross House, Cooper St., Chichester, West Sussex, P019 1EB, England. 1987. $89.95 Bioluminescence and Chemiluminescence: New Perspectives. J. Scholmerich et al. xv + 600 pp. John Wiley & Sons, 605 Third Ave., New York, N.Y. 10016.1987. $110
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ANALYTICAL CHEMISTRY, VOL. 60, NO. 5, MARCH 1, 1988 · 341 A
