This is Tony’s last column for Spectroscopy Europe. It is explores an idea that he has been developing for over 30 years, although as Tony points out the story starts around 3500 years ago.
Tony (A.M.C.) Davies looks at Multiple Linear Regression (MLR) this issue, as well as expressing his opinions about Principal Components Regression (PCR) and Partial Least-Squares (PLS).
Report on the The Seventh International Conference of Advanced Vibrational Spectroscopy (ICAVS-7) held in Kobe, Japan.
Tony (A.M.C.) continues down the last furlong of his series of Tony Davies Column articles. This issue, he considers principal component analysis (PCA). Using research recently published in the Journal of Near Infrared Spectroscopy, he explains that PCA is a very useful tool but it will not solve all our problems. Two old articles on PCA, including Tony’s concept of the “Data Cake” have been added to the website, are referenced in Tony’s article and can be freely downloaded by readers.
Tony (A.M.C.) Davies starts a review of the chemometric ideas that have most excited him over the last 30 years. In this column, he looks at the use of Fourier transformation for data compression. FT can also provide the side benefit of reducing high-frequency noise.
Tony (A.M.C.) Davies and Tom Fearn describe an enhancement of the popular partial least squares (PLS) technique, powered partial least squares (PPLS), that has shown significantly better results.
Tony Davies makes sure we understand “What IS and what is NOT chemometrics” and why it matters.
Examining diffuse reflection and transmission spectra more thoroughly: Part 2. Sample temperature and sample composition
The Tony Davies Column once again contains a contribution from Karl Norris, who is widely regarded as the “father of NIR spectroscopy”. Karl continues to produce innovative ideas about the field and this article is no different. Building on the previous article concerning fourth derivatives, Karl has investigated the effect of varying gap sizes with some remarkable results.
This Tony Davies Column is contributed by Karl Norris, known to many as “The father of near infrared spectroscopy”. He introduces his calculation method for fourth derivatives and shows how it can be used to extract instrument noise.
Tony (A.M.C.) Davies is again telling us to “Always look at the spectrum”. This time he uses an example from the development of a NIR spectrometer to demonstrate that one doesn’t really know what’s going on until one has “looked at the spectrum”.
Anaerobic digestion is a good solution to the joint problems of dealing with organic waste and producing “clean” energy. However, running the digesters at optimum performace is a complex business. NIR spectroscopy offers a solution to monitor a number of analytes within the reactor and in real time.
This second Product Focus is on Molecular Spectroscopy, and a number of companies have provided information on their key products, their applications and features.
Tony (A.M.C.) Davies stresses the importance of always looking at the spectrum, even if you [think you] know there’s nothing to learn. He relates his experience with noise in NIR spectra and what he has learnt from it. He would like us all to examine spectra for abnormality before relying on automated methods.
Tony Davies and Tom Fearn present “A digression on regression”. They turn their attention to one of the simpler regression techniques, Classical Least Squares (CLS). As well as an explanation of the basics, they explain why it is not often used in spectroscopy, and give the pros and cons of various regression techniques.
I recently “discovered” a very interesting radio programme on BBC Radio 4. It is “devoted to the powerful, sometimes beautiful, often abused but ever ubiquitous world of numbers”. A few weeks ago we were asked to say what we were doing while listening to the programme. The next week we were told that nearly 2000 e-mails had been received and this data had been given to information designer David McCandless to turn into a graphic. When this was trailed I got the impression that something new and exciting was going to be displayed and I thought that the graphic would include sound. The graphic is good but rather “ordinary” and I was disappointed. This got me thinking about how we display information. Have we made any advance in the last 25 years? Could sound be used!
Patrik Johanssona and A.M.C. DaviesbaApplied Physics, Chalmers University of Technology, SE-41296 Göteborg, SwedenbNorwich Near Infrared Consultancy, 75 Intwood Road, Cringleford, Norwich NR4 6AA, UK. E-mail: email@example.com
In last year’s August/September issue of Spectroscopy Europe1 I wrote a column about my “discovery” of computational chemistry and asked if anyone was interested. A satisfying number of readers answered the on-line survey with very positive comments but none more so than Patrik Johansson who e-mailed me about his delight with the column and to assure me that there was “indeed a bunch of scientists out there that do work on IR (and Raman) using both experimental and computational techniques—I am one of them”! This column is the first result of the ensuing e-mail conversation and is due to Patrik. I remain excited by the possibilities of computational chemistry particularly as Patrik thinks that an approach to NIR spectroscopy is indeed possible.Tony Davies
Something has happened to my data: potential problems with standard normal variate and multiplicative scatter correction spectral pre-treatments
A.M.C. DaviesNorwich Near Infrared Consultancy, 75 Intwood Road, Cringleford, Norwich NR4 6AA, UK. E-mail: firstname.lastname@example.orgTom FearnDepartment of Statistical Science, University College London, Gower Street, London WC1E 6BT, UK. E-mail: email@example.com
It is common practice in near infrared (NIR) calibration to apply pre-treatments designed to correct for the scatter effects usually seen in absorbance data. These pre-treatments can interfere with interpretation of the spectra. This is illustrated here with the aid of two rather extreme artificial examples.
Where there’s muck there’s brass! A look at anaerobic fermentation monitoring using molecular spectroscopy
A.N. Davies,a H.M. Heiseb and D.F. IhrigcaProfessor, SERC, University of Glamorgan, UK, Director, ALIS Ltd, and ALIS GmbH—Analytical Laboratory Informatics SolutionsbISAS—Institute for Analytical Sciences at Dortmund University of Technology, Bunsen-Kirchhoff-Str. 11, D-44139 Dortmund, GermanycUniversity of Applied Sciences of South-Westphalia, Frauenstuhlweg 31, D-58644 Iserlohn, Germany
OK... I know... for the majority of the readers of Spectroscopy Europe a phrase which comes from Yorkshire probably makes a pretty poor title for an article. However, if in “Where There’s Muck There’s Brass” you simply translate Muck as Dirt or Waste and understand that Brass is a Yorkshire term for Money, then you might get a little closer to our subject, Spectroscopy in Anaerobic Bioreactor Monitoring and Control.
At the Sustainable Environmental Research Centre (SERC), which has carried out research in AD systems for more than 30 years,1 we have initiated a new knowledge transfer organisation to help, advise and promote Anaerobic Digester technology. Led by Dr Sandra Esteves the AD centre has the explicit aim of helping early adopters overcome some of the common hurdles they may encounter (www.walesadcentre.org.uk).
Tony Daviesa and Tom FearnbaNorwich Near Infrared Consultancy , 75 Intwood Road, Cringleford, Norwich NR4 6AA, UKbDepartment of Statistical Science, University College London, Gower Street, London WC1E 6BT, UK
Bankers’ pensions, Government borrowing or Spectroscopy Europe columnists, the watchword for 2009 appears to be controversial! In the previous version of this column, Tony Davies (the younger) was being controversial about education and in this issue I am being controversial about one of the current applications of chemometrics to the use of spectroscopy in industry.
Tags: Near infrared
Christopher BurgessBurgess Analytical Consultancy Limited, “Rose Rae”, The Lendings, Startforth, Barnard Castle, Co. Durham, DL 12 9AB, UKJohn HammondStarna Scientific Ltd, 52–54 Fowler Road, Hainault Business Park, Hainault, Essex, IG6 3UT, UK
Following on from our previous foray into the UV-visible area of the spectrum, in this article we discuss its nearest neighbour in the spectral scale, namely near infrared (NIR) spectrometry. The NIR spectral region lies between 780 nm and 2500 nm (4000 cm–1 to 12,800 cm–1) bridging the more well-known and analytically used regions of the UV-visible (190–780 nm) and the infrared (4000–600 cm–1).
Tags: Near infrared