Tony Davies

An introduction to near infrared spectroscopy

When you hold your hand out to a burning fire you “feel” the heat being emitted by the fire but what is happening? The fire gives out light and infrared (IR) radiation; from a fire most of this is near infrared (NIR) radiation. Some of the NIR radiation is absorbed by water molecules in your skin. This raises the temperature of the water and results in an increase in temperature in the surrounding tissue which is detected by nerves in your skin. This radiation was discovered in 1800 by William Herschel, a musician and very successful amateur astronomer (he discovered the planet Uranus) because he wanted to know if any particular colour was associated with heat from sunlight. He found that the heat maximum was beyond the red end of the spectrum. Herschel could not believe that light and his “radiant heat” were related but he was wrong. By 18 5 Ampere had demonstrated that the only difference between light and what he named “infrared radiation” was their wavelength. Then in 1864 James Maxwell wrote “This velocity [of electromagnetic force] is so nearly that of light that it seems we have strong reason to conclude that light itself (including radiant heat and other radiations) is an electromagnetic disturbance in the form of waves propagated through the electromagnetic field according to electromagnetic laws”. What we now call the electromagnetic spectrum is shown in Figure 1.

Calibration Problem. Is the end of the "Calibration Problem" in sight?

The “Calibration Problem” is the real or perceived difficulty in introducing near infrared (NIR) methods because of the complexity of the calibration procedure. It was most graphically demonstrated by Rosenthal and Williams1 at NIR-95 in Montréal, Canada in 1995. Bob Rosenthal sent out a questionnaire to two groups of NIR spectroscopic practitioners in the NIR community: users and researchers and he and Phil Williams analysed the answers. One of the questions was: “What do you think are the major current limitations of NIR instruments?” There was then a list of five possible answers (summarised as speed, sensitivity, calibration, versatility, expense and other [specify]). The two groups gave very similar answers. Size of instruments was the only “other” to be suggested by a few correspondents and expense and calibration were the two factors highlighted by the majority with calibration scoring almost twice that of expense. If more instruments were sold they would undoubtedly be less expensive, which leaves “Calibration” as the most significant problem preventing the more rapid spread of NIR technology.

Book Reviews: A User-Friendly Guide to Multivariate Calibration and Classification, An Academic Addition to the NIR BookshelfA User-Friendly Guide to Multivariate Calibration and Classification Tormod NæsIsakssonTomasFearnTomDaviesTonyNIR Publications, Chichester, UK, 2002, ISBN 0 9528666 25, price: £45.00,

Chichester: NIR Publication, 2002. User Friendly Guide to Multivariate Calibration and Classification. Martens H, Martens M: Multivariate analysis of quality. Publication as an International Standard requires approval by at least 75 % of the Note 2 to entry: It is possible to develop and validate NIR methods for other T., Davies, T. A user-friendly guide to multivariate calibration and classification.

75.00Near-Infrared Spectroscopy Principles, Instruments, Applications, Edited by SieslerH.W.OzakiY.KawataS. and HeiseH.M.ISBN 3-527-30149-6, pp. xiii + 348, Wiley-VCH, Weinheim, Germany (2002)

By European standards the New Atlantic City Convention Center is a large building! The Exhibition Hall (one of several) was vast and was not filled by the EAS exhibitors. The public areas were also very large so I expect this helped to make the lecture rooms appear even smaller than they were. The ones I went into seated about 50 or 100 people. There may have been larger ones used by sessions I did not attend. This is a multi-parallel session Symposium with up to ten concurrent streams. This did cause problems. I was a few minutes late for the beginning of a Chemometrics session and found a queue at the door. I tried again after the tea-break and found many available seats so that Svante Wold’s EAS Chemometrics Award lecture was given to a rather small audience. Those not present missed a very good session. Mats Josefson gave a very good lecture titled “Chemometrics shapes Spectroscopy, Spectroscopy shapes Chemometrics”. Among other things he explained how artefacts could be created in spectra of moving streams caused by particle movements. These can

Eastern Analytical Symposium. The conference

THIS YEAR, FOR THE FIRST TIME IN HALF A CENTURY, THE FIRST DAY OF HANUKAH AND CHRISTMAS DAY converged—good news for my family mix. But just before that day, the Science family found itself absorbed in a different temporal convergence, one that brought both good news and bad to us and to our readers in the scientific community. The troubling story of Professor Woo Suk Hwang and his colleagues appeared everywhere, as questions about a paper they had published in this journal unfolded amid a welter of charges, countercharges, proposed retractions, and two investigations. At about the same time, on the front page above the fold in the New York Times, appeared Judge John Jones’opinion in the Dover, Pennsylvania, school board case. For most of the scientific community, this second story relieved a longstanding concern. Some school boards (famously in Kansas and Pennsylvania, but also in many other U.S. states) had voted either to limit the teaching of evolution in science classes or to introduce it along with alternative explanations that were essentially religious in character. The rising tide of evangelical Christianity and its alliance with a conservative political movement seemed to foreshadow a national suspicion of science or a deep confusion about what science is or isn’t, or possibly both. The Dover decision was a decisive, elegantly crafted resolution of the question before the court. Was intelligent design (ID) a new proposal, generated by the school board for consideration by students and teachers as an alternative to evolution, based on scientific grounds? Or was it instead a Trojan Horse proxy for the older notion of creationism? Judge Jones said, in no uncertain terms, that ID was not science, but rather creationism redux, and that it did not belong in a science classroom. He added that its advocates, “who so staunchly and proudly touted their religious convictions in public, would time and again lie . . . to disguise the real purpose behind the ID Policy.” The decision, in which the losers were charged attorneys’fees, can be found at http://www2.ncseweb.org/wp/. It’s worth reading. The other story is a deeply disappointing one: for the scientists who did the work; for the scientific community (and especially those who have been excited by the therapeutic prospects of stem cell science); and for this journal. At this writing, we don’t have a final report from an investigation now underway at Seoul National University. But preliminary findings and admissions by Hwang point to considerable fraud, leaving open only the question of whether some of the findings published in Science and other journals by Hwang’s research group may survive. A journal cannot go into authors’ laboratories in search of fraud. But we can and do encourage appropriate authorities to conduct investigations, and we supply information freely as investigations proceed. More actively, we are committed to examining our processes and ourselves in an effort to extract lessons for the future. In examining the reports by reviewers of the Hwang papers, we saw no reason to lack confidence in the authenticity of the data. But there is more to do, and at the end of this process we will be able to report to our readers and others what we have learned about how we might modify our treatment of papers with unusual potential impact. One question we have been asked by mainstream journalists is whether this is an indictment of the peer review system. Not at all; we believe strongly in the peer review system, but we have never thought it infallible. Carefully reviewed studies sometimes turn out to be wrong because later attempts at repetition fail. But peer review requires authors to provide more data and more confirming material, making it likelier that careful efforts at confirmation will follow. Fraud is something quite different, and very hard to detect. Of course, reviewers or editors might be sent to the authors’ labs to look at the notebooks, imposing costly and offensive oversight on the vast majority of scientists in order to catch the occasional cheater. That’s a bad idea. The reporting of scientific results is based on trust. It’s better to trust our colleagues, despite the fact that on rare occasions one of them might disappoint other scientists and those hoping for cures. –Donald Kennedy