Articles
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”.
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.
1H NMR spectra are usually interpreted by hand, which is very time consuming, and can become a process bottleneck in fields such as high-throughput NMR. Greater automation of the spectral analysis process has become essential if NMR is to be of value as a high-throughput analytical method in the future.
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.
Time for a good whinge (“complain persistently and in a peevish or irritating way”—Oxford Dictionaries Online) and to get a little controversial. Having had a year to look at the resources available to us to help educate our budding spectroscopists, I have been disappointed that much of the educational resources available online appear incomplete or outdated. For a generation of students brought up in schools with interactive whiteboards, good quality spectroscopic teaching materials of this nature are almost non-existent.
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!
Analytical Information Mark-up Language, better known as AnIML, has been around as a concept for a number of years, but how does an analytical chemist use it in the real lab? A team of R&D scientists at LGC has been finding out.
A.M.C. Davies
Norwich Near Infrared Consultancy, 75 Intwood Road, Cringleford, Norwich NR4 6AA, UK. E-mail: [email protected]
Tom Fearn
Department of Statistical Science, University College London, Gower Street, London WC1E 6BT, UK. E-mail: [email protected]
Tony Davies
Norwich Near Infrared Consultancy, 75 Intwood Road, Cringleford, Norwich NR4 6AA, UK
Fans of “Monty Python’s Flying Circus” will realise that what follows is not likely to be my usual column (and they might be hoping that it will be amusing).
Introduction
This column is about “Computational Chemistry”.
I would like to thank everybody who has taken the trouble to respond to my last column on Educating Spectroscopists.1 I am very happy that Ian has allowed me space to reproduce some of them in this edition.
This short review shows that UV/visible spectroscopy plays a key role in the discrimination of colour in the forensic analysis of fibres and inks. The application of chemometrics, however, is vital in many cases to enhance such discrimination and to put it on a quantitative basis so providing objective justification for the conclusions of the analyst.
In our previous column we introduced CVA, one of the very early applications of multivariate analysis (1930s). In this column we will discuss SIMCA (officially it is Soft Independent Modelling of Class Analogies, but no one uses the long form!). SIMCA was invented 30 years later by another pioneer, Svante Wold (the man who coined the word “chemometrics”).
A.M.C. Daviesa and Tom Fearnb
aNorwich Near Infrared Consultancy, 75 Intwood Road, Cringleford, Norwich NR4 6AA, UK. E-mail: [email protected]
bDepartment of Statistical Science, University College London, Gower Street, London WC1E 6BT, UK. E-mail: [email protected]
A.M.C. Davies and Tom Fearn
Norwich Near Infrared Consultancy, 75 Intwood Road, Cringleford, Norwich NR4 6AA, UK. E-mail: [email protected]
Department of Statistical Science, University College London, Gower Street, London WC1E 6BT, UK. E-mail: [email protected]
A.N. Davies
External Professor, University of Glamorgan, UK, Director, ALIS Ltd, and ALIS GmbH – Analytical Laboratory Informatics Solutions
“The man who gets the most satisfactory results is not always the man with the most brilliant single mind, but rather the man who can best coordinate the brains and talents of his associates.”—W. Alton Jones
The starting point for this column is the last one from last year! In that column TD began what was intended to be a two-part story but has, with this column, become a story in four parts. There were required topics we had not covered and we need to begin this column by completing the discussion of removing multiplicative effects by describing what the two most popular methods do to NIR spectra.
When we set up ALIS GmbH one of the first major “discoveries” was probably the most embarrassing for me. Having worked on analytical data standards for so long, I seem to have successfully generated a blind spot for the developments which have taken place in the structure, standardisation and functionality of the Portable Document Format (PDF).2 Maybe it’s due to a subconscious aversion to what I had for a long time seen as a simplistic “get out” solution for those too lazy to convert data into a long-term, stable, vendor-neutral format. How often have we heard the “well... we just print to PDF” as an excuse for not having in place a properly thought through analytical data storage and archiving policy taking no account of the future use to which that data may well be put within an organisation.
Anyway, it has been pretty difficult for me to admit that my knowledge of the available functionality lay somewhere back in the early 1990s (see Figure 1) but I hope in this column to make some amends!
The last TD column showed the effect of calculating second derivatives on a set of 100 spectra, which will be the starting point for this column.
This column is about the most basic of pre-treatments, which has been used in spectroscopy well before the word "Chemometrics" was invented.
A.N. Davies
External Professor, University of Glamorgan, UK, Director, ALIS Ltd., Analytical Laboratory Informatics Solutions
