Statistics chemometrics

For many applications, quantitative band shape analysis is difficult to apply. Bands may be numerous or may overlap, the optical transmission properties of the film or host matrix may distort features, and features may be indistinct. If one can prepare samples of known properties and collect the FTIR spectra, then it is possible to produce a calibration matrix that can be used to assist in predicting these properties in unknown samples. Statistical, chemometric techniques, such as PLS (partial least-squares) and PCR (principle components of regression), may be applied to this matrix. Chemometric methods permit much larger segments of the spectra to be comprehended in developing an analysis model than is usually the case for simple band shape analyses. 

Chapter 7 (by H. Ishida and A Ishitani) review microscopic and surface analytical techniques. Chapter 8 (by D. M. Haaland) reviews developments in statistical chemometrics for data analysis. 

A total of 185 emission lines for both major and trace elements were attributed from each LIBS broadband spectrum. Then background-corrected, summed, and normalized intensities were calculated for 18 selected emission lines and 153 emission line ratios were generated. Finally, the summed intensities and ratios were used as input variables to multivariate statistical chemometric models. A total of 3100 spectra were used to generate Partial Least Squares Discriminant Analysis (PLS-DA) models and test sets. 

The skills needed to master NIR are physics, statistics, chemometrics, and optics. 

The distribution of data plays an important role in statistics chemometrics is not so happy with this concept because the number of available data is often small or the... 

Pattern Recognition. The application of computers to build descriptive or predictive models (i.e., find patterns) of information from input datasets. The techniques of pattern recognition overlap those used in statistics, chemometrics, and data mining, and include data display, description, and reduction, unsupervised methods such as cluster analy-... 

Some basic concepts and definitions of statistics, chemometrics, algebra, graph theory, similarity/diversity, which are fundamental tools in the development and application of molecular descriptors, are also presented in the Handbook in some detail. More attention has been paid to information content, multivariate correlation, model complexity, variable selection, and parameters for model quality estimation, as these are the characteristic components of modern QSAR/QSPR modelling. 

Miller, J.N. and Miller. J.C. (2005) Statistics Chemometrics for Analytical Chemistry (5th edn), Prentice Hall Ptr ISBN 0-13-1291920. 

By the way, chemometric techniques are applied using statistical/chemometric software packages that work as black boxes for final users. Sometimes the blindly use of "intelligent problem solvers" or similar wizards with a lot of hidden options as default may lead to misleading results. Accordingly, it should be advisable to use software packages with full control on parameters and options, and obviously, this software should be used by a chemometric connaisseur. 

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