A Historic Collaboration July marked the 25th anniversary of the publication in ANALYTICAL CHEMISTRY of Abraham Savitzky and Marcel Golay's landmark paper describing a smoothing algorithm for the reduction of random noise from measured spectra (Anal. Chem. 1964,36,1627-39). The digital smoothing filters they described have been used extensively in data analysis because they are versatile and easy to implement. When the paper was published, both scientists were employed by the Perkin-Elmer Corporation; Savitzky as an instrumentation specialist in the research department of the Instrument Division and Golay as a senior research scientist. Golay, an electrical engineer, retired in 1955 from the U.S. Signal Corps Engineering Laboratories (Fort Monmouth, NJ) and began a second career as a consultant to P-E. This 34year association lasted until his death (see p. 922 A). Savitzky met Golay when he was a graduate student at Columbia University working GOLAY on the development of a double-beam spectrophotometer that used a Golay IR detector. After receiving his Ph.D. in physical chemistry in 1949, Savitzky was employed by P-E as an engineer developing IR process control instrumentation. Later he was involved in P-E's initial GC research and in building P-E's earliest prototype GC instrument. In 1960 he became involved in the emerging field of computerassisted instruments and, as a principal scientist, led programming teams in the development of P-E's IR software for the microcomputer. Savitzky retired in 1985 to form his own consulting firm for software development and information services (Silvermine Resources, Inc.). On the occasion of the 25th anniversary of this classic work, Savitzky looks back at the genesis of the publication. SAVITZKY
Abraham Savitzky Silvermine Resources, Inc. 3 Mail Coach Court Wilton, CT 06897
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n late 1959 or early 1960, John Atwood, then director of research for the Perkin-Elmer Instrument Division, Norman Adams, Marcel Golay, and I discussed the analysis and interpretation of IR spectra untouched by human hands. Our first problem was the recognition of spectral characteristics such as peaks, valleys, and shoulders. It appeared that these features could be determined from changes in
sign in the first and second derivatives. We asked Golay to look into a simple and fast method for calculating the derivatives. My notebooks show that in September and October 1960 he provided me with sets of first- and secondderivative convoluting integers for parabolas. We used those on synthetic spectra to prove our ability to find spectral features. This method worked well enough for spectra without noise but worked poorly when we added synthetic noise. A summary of this work, with a table of the criteria for recognition of spectral features, was published in ANALYTICAL CHEMISTRY in December 1961 (Vol. 33, No. 13, p. 25 A). This
article discussed averaging of adjacent points for noise reduction but still did not recognize the smoothing algorithm. (This paper, incidentally, also mentioned determination by multiple instruments, one of the key methods of today's chemometrics.)
FOCUS By early 1962 we had efficient routines for first and second derivatives, but a notebook entry for March 1962 reads: "I need a general purpose convolution program" and defines its characteristics.
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FOCUS Earlier, I had committed to presenting a paper titled "Some Numerical Operations on Analytical Data" at the 15th annual summer symposium of the Division of Analytical Chemistry. The symposium was held in June 1962 at the University of Maryland. In January I wrote to Golay, who was at the Technische Hogeschool in Eindhoven, The Netherlands: It would be very helpful if you could join me as co-author. I would plan to call on you primarily for the development and elegant explanation of the derivative functions as well as for some guidance on the type of filtering functions to study.
I am not as concerned about the oral presentation as I am about the material which will be published in Analytical Chemistry. There are some very few references to the method in the literature, but it is apparently not well enough known, especially by analytical chemists. At about this time, my reading and work with the generalized program and real data prompted me to look more closely at smoothing as well as derivatives. In April 1962 I wrote to Golay: The objective of this paper is to extend the application of the methods you suggested for determination of the first and second
derivatives into other areas. The class of methods which should be discussed is characterized by a convolution of the experimental data with a set of integers, followed by normalization. The importance of these methods is that for the smoothing functions and for the derivative functions, the computer program is essentially the same. Thus a single general purpose program which provides for entry of the set of convolution integers and the normalizing factor can handle a very broad class of problems. One of the basic differences
Marcel G o l a y — A Memorial Marcel Jules Edouard Golay, inventor of the open-tubular (capillary) column, died suddenly on April 27, shortly before his 87th birthday. The entire chromatographic community mourns the passing of this active and vital member. At the time of his death, Golay was preparing a plenary lecture on chromatography under turbulent flow conditions for the May meeting of the International Symposium on Capillary Chromatography in Riva del Garda, Italy. This work described how chromatographic measurements can provide information on the properties of the turbulent flow that is otherwise inaccessible. He was also conducting a very difficult experiment on the design of improved open columns and was advising scientists at the Perkin-Elmer Corporation in various high-technology areas. Marcel Golay was born on May 3, 1902, in Neuchâtel, Switzerland. He graduated in 1924 as an electrical engineer from the Eidgenôssische Technische Hochschule (ΕΤΗ), the Swiss Technical University in Zu rich, and joined Bell Telephone Laboratories in the United States. He left Bell in 1928 to pursue gradu ate studies at the University of Chi cago, where he received a Ph.D. in physics in 1931. After graduation he joined the U.S. Signal Corps Engi neering Laboratories in Fort Mon
mouth, NJ. He retired in 1955 as chief scientist of the Components Division and became a consultant to Philco (Philadelphia, PA) in net work and information theory and to the Perkin-Elmer Corporation (Norwalk, CT) in scientific instru mentation. During 1961-1962 he was a professor at the University of Technology in Eindhoven (The Netherlands), and from 1963 until his death he was a senior research scientist at P-E. Although the invention of the open-tubular column was Golay's best-known achievement in the field of chromatography, it was only one of his many contributions to science. Indeed, the immense scientific and technical knowledge of the man was fascinating. His accomplishments span a variety of areas that at first glance appear unrelated but that all include the acquisition, transfer, and processing of information. In radio communications he is well known for the invention of the dispersionless Golay delay line, a device for detecting the presence of a certain pattern of information in a signal that is passing through a de lay line. In information theory and pattern recognition he invented the perfect binary and ternary codes, the only two multierror correction codes ever found. He created the concept of complementary codes that are used worldwide in the Lo-
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ran C precision radio navigation sys tem and that are still broadcast con stantly by countless radio beacons throughout the world. He also de veloped a number of image signalprocessing analysis algorithms. One of these is a complete image-pro cessing language used in an instru ment that can successfully identify 17 different normal and abnormal human white blood cells. In the field of instrumentation Golay made many landmark contri butions. In IR spectroscopy the Golay detector is the most sensitive room-temperature detector avail able and performs essentially to the oretical limits over a wide spectral range. This is a pneumatic detector in which the IR signal heats a small gas volume whose expansion is de tected by the motion of a flexible mirror membrane. In NMR spec troscopy, he invented a very elegant system to tune the spectrometer and rapidly achieve the minimum bandwidth. This system decom poses the nonuniform magnetic field in the sample space into its or thogonal spherical harmonics; it is then possible to cancel each func tion independently. Together with Abraham Savitzky (see p. 921 A of this issue), he developed a smooth ing algorithm that permits the re duction of random noise from mea sured spectra. In chromatography, besides the invention of open-tubu-
between using the digital computer rather than an analog device for performing the function is that a symmetrical set of data around the central point allows the use of functions which are a reasonable fit to the experimental function. What I would like to have is a "cookbook" procedure (for mathematically unsophisticated chemists like myself, rather than for mathematicians) for generating the set of integers for any desired function and for derivatives of any degree from zero on up. The useful thing, for the paper, would be to have a simple set of rules for
lar columns, Golay contributed to the investigation of high-speed GC and LC, the influence of instrumental contributions to column performance, and the development of sampling methods. It is remarkable that this scientist, an electrical engineer by training, received two major awards of the American Chemical Society: the ACS Award in Chemical Instrumentation (1961) and the ACS Award in Chromatography (1981). He was also the recipient of the Distinguished Award of the Instrument Society of America, t h e Tswett Chromatography Award of the International Symposium on Advances
obtaining the integers and normalizing function, plus a simple, elegant proof in the appendix. Golay's reply to this letter became the basis for the appendix. The paper was submitted to A N A L Y T I C A L C H E M ISTRY in February 1964 and received a
quick review. Of the two reviewers, one said essentially, "nothing new, don't publish" and the other said, "interesting, publish." My reply was that the previously published work had discussed applications in statistical analysis of small numbers of observations. No one, apparently, had applied the techniques to the large numbers of sampled data points that we saw with the newly computerized instruments.
in Chromatography, the Chromatography Anniversary Medal of the Academy of Sciences of the USSR, and the Dal Nogare Award in Chromatography of the Chromatography Forum of the Delaware Valley, as well as many other awards. In 1977 Golay received an honorary doctorate from the Ecole Polytechnique Fédérale of Lausanne, Switzerland. He was the author of more than 90 scientific papers, and he obtained 41 patents. Golay's legacy in high-resolution chromatography will be maintained by t h e newly established Marcel Golay Medal. The first recipients of this award, presented at the recent International
Fortunately the Editor, Lawrence Hallett, agreed. In thinking about why the technique has been so widely used, I've come to the following conclusions. First, it solves a common problem—the reduction of random noise by the well-recognized least-squares technique. Second, the method was spelled out in detail in the paper, including tables and a sample computer subroutine. Third, the mathematical basis for the technique, although explicitly and rigorously stated in the article, was separated from a completely nonmathematical explanation and justification. Finally, the technique itself is simple and easy to use, and it works.
Symposium on Capillary Chromatography, were R. E. Kaiser, R. D. Dandeneau, and E. H. Zerenner. Discussions with Golay were unusual and exciting experiences. He always went right to the center of the problem, analyzing it at the most profound level, drawing on the necessary contributions of physical chemistry and information theory. Using the required mathematics, he was able to clearly state a model and to derive the consequences of the abstraction in a straightforward manner. The conclusion was a beautiful description of the experiment that had to be performed. Making the device work was rarely easy, but it was always worthwhile. The early papers of Golay on the open-tubular column give an excellent idea of this process and the results. Few major contributions that can be traced to a single man have, at the same time, had such a profound influence on so many people. How many thousands of chemists have used a capillary column? (It is estimated that in 1987 60% of all GC analyses were carried out on opentubular columns.) How many have been saved by a diagnosis based on the results of GC/MS analysis? What is the impact on our society of the environmental regulations based on information collected by capillary GC/MS analyses? These contributions reflect the enduring and immeasurable scientific and technical legacy of Marcel Golay. Georges Guiochon Leslie Ettre
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