Letters
An Exchange of Comments on "Introduction to Analytical Gas Chromatography" Sir: The following is offered in re sponse to the review by Leslie Ettre ( A N A L Y T I C A L C H E M I S T R Y , October
1981, ρ 1393 A) of my book, "Intro duction to Analytical Gas Chromatog raphy." Errors of fact The review states incorrectly that several important discussions are missing from the book. This is surpris ing: The topic of each discussion is listed in the subject index, which is elaborate, and each discussion is ex tensive. In the following paragraphs, an incorrect statement from the re view is followed by the location and nature of the indicated discussion. " . . . there is no discussion of the meaning of the fundamental equation relating resolution, efficiency, capacity ratio, and relative retention . . . " The truth is, in chapter 4, after the equa tion is derived, the rest of the chapter is devoted to explaining the meaning of this equation. The first two of these pages are very explicit; the rest are il lustrative. " . . . there is no discussion . . . on the question of how the phase ratio influ ences the capacity ratio and resolution . . . " The fact is, pp 100-107 are given to just this topic. "The retention index is not ex plained." The Kovats Retention Index is described on pp 60 and 61 as a tool in stationary phase characterization and on pp 298 and 299 as a means of qualitative analysis. "There is no discussion on the role of the carrier gas as such." Such dis cussions occur on pp 11,19-20, 10710,180, 237-41, and 246. Further dis cussions related primarily to the ef fects of the carrier gas on detector re sponse occur on pp 147-49,152-62, 168, and 174.
" . . . there is no discussion pertain ing to the van Deemter equation in the spirit of Giddings's random walk theo ry." In fact, van Deemter-related ref erences to and quotations from Gid dings's "Dynamics of Chromatogra phy" occur in both of the "van Deem ter" chapters: pp 77 and 80 in chapter 6, and pp 109, 110, and 111 in chapter 7. Special features of this book There are several features, singular to this book, that should have been re viewed but were not even mentioned. Among these are, for instance, three dedicated chapters: chapter 4, devoted to resolution—the problem of selectiv ity vs. plate number; chapter 10, to the column, including elaborate treat ments of open tubular columns and of the evaluation of column performance; and chapter 11, to column tempera ture. The book also contains extended treatments of subjects that, although new, will nevertheless have enduring importance: treatments of fused silica columns (pp 216-18) and gas chromatography-mass spectrometry (pp 301-4 and 317-36); and a 24-page de scription of the algorithms on which all modern integrators are based. The book: its origin and design The book evolved from lecture notes for a graduate course in gas chromatography and from the com ments of the students. In the author's judgment, it states what every practi tioner of gas chromatography should either know or have at hand. Without exception, the students welcomed the "unnecessarily detailed mathematical treatments." Indeed, in response to their comments, which I constantly solicited, the treatments were occasionally made still more de tailed. As stated in the preface, "Because the treatment is cumulative, the book should be read from front to back."
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The reader, by design, then sees only material for which he or she has been carefully prepared. The reviewer found this approach "confusing"; the students said they found it helpful. By the same design, the technical level of the book rises only slowly at first. The technical level of the last chapters consequently is much higher than that of the first. Accordingly, dif ferent parts of the book may seem to have been written for different audi ences; but in fact the true audience is merely an increasingly sophisticated one. Accordingly also, the book, if dipped into at random for the first time, may seem "uneven"; but it is not uneven if read from front to back, and it is certainly not unsystematic. John A. Perry Regis Chemical Company 8210 Austin Ave. Morton Grove, 111. 60053
Reply: Dr. Perry refers to the fact that his book evolved from lecture notes for a course in gas chromatogra phy and hence, follows the didactics of a course. But this is exactly what my review criticized! In my opinion the didactics of a course and those of a book are different. In a course, one often mentions something first briefly, to lay the foundations for future treat ment, and then returns to the same question later to discuss it in depth. On the other hand, in a book, one sys tematically discusses the various top ics in individual chapters. Dr. Perry claims that, if read from front to back, the discussion would not sound uneven and unsystematic. Nov els are indeed read from front to back, but monographs and textbooks are seldom read that way; they are used by chemists when they are interested in a particular question, and they don't like to jump from chapter to chapter when looking for a single topic.
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Dr. Perry also claims that I was wrong in referring to the lack of some basic discussions. For example, I men tioned that the retention index is not explained, and his answer is that it is discussed in four pages. However, no where is its meaning explained, that it corresponds to the carbon number (X 100) of a hypothetical η -paraffin with the same retention characteristics. Also, while the fundamental equation is treated in detail, the conclusions are not drawn. For example, in pp 43-53, the variation in liquid loading is dis cussed historically but is not related at all to the last term of equation 4.8. If the capacity factor (k) is small, ways must be found to increase it, while if k is large, one tries to reduce it. Such a discussion is much more important than showing how equations are rear ranged, moving a term from the righthand side to the other or vice versa, which is elementary mathematics.
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Dr. Perry complains that I did not mention some features that are "sin gular to this book" such as an elabo rate treatment of open tubular col umns or of fused-silica columns. But these are self-evident in a general book on gas chromatography pub lished in 1981. Would you praise a book dealing with basic mathematics because it also discusses multiplica tion? I could continue and present a re buttal of each point in Dr. Perry's let ter; however, I feel that this is unnec essary. Rather, permit me to make a general statement. A book review is not promotional material extolling the virtues of the particular book. Rather it represents the personal opinion of the reviewer who is selected by the editor of the journal because of his familiarity with the topics. Also, a review is not a sci entific paper in which every statement must be explained and proven. The author may or may not agree with the reviewer. However, the author can be sure that the reviewer had good rea sons for every statement in the review, even if he did not elaborate in detail; after all, only summary conclusions can be given in 500-600 words. In my review of Dr. Perry's book I characterized it as a useful general text for GC training courses and ex pressed my opinion that, in spite of a number of shortcomings, it fills many of the requirements for a serious, modern general textbook on gas chro matography. There is nothing I can add to this opinion.
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