Chemometric approach

Note These equations are from Doming, S. N. Morgan, S. L. Experimental Design A Chemometric Approach. Elsevier Amsterdam, 1987, and pseudo-three-dimensional plots of the response surfaces can be found in their figures 11.4, 11.5, and 11.14. The response surface for problem (a) also is shown in Color Plate 13. 

Deming, S. N. Morgan, S. L. Experimental Design A Chemometric Approach. Elsevier Amsterdam, 1987. 

S. N. Denting and S. L. Morgan, Experimental Design A Chemometric Approach Elsevier Science Publishing Co., Inc., Amsterdam, The Netherlands, 1987. D. D. Wolff and M. L. Parsons, Pattern Recognition Approach to Data Interpretation Plenum Press, New York, 1983. 

The identification of synthetic colorants (pure or mixtures) in foods is usually carried out using spectrophotometry but the resolution of complex mixtures in food requires a previous separation of extract components by SPE and chromatographic techifiques. Dual wavelength, solid phase, and derivative spectrophotometric methods combined with chemometric approaches have been used. ... 

Because of peak overlappings in the first- and second-derivative spectra, conventional spectrophotometry cannot be applied satisfactorily for quantitative analysis, and the interpretation cannot be resolved by the zero-crossing technique. A chemometric approach improves precision and predictability, e.g., by the application of classical least sqnares (CLS), principal component regression (PCR), partial least squares (PLS), and iterative target transformation factor analysis (ITTFA), appropriate interpretations were found from the direct and first- and second-derivative absorption spectra. When five colorant combinations of sixteen mixtures of colorants from commercial food products were evaluated, the results were compared by the application of different chemometric approaches. The ITTFA analysis offered better precision than CLS, PCR, and PLS, and calibrations based on first-derivative data provided some advantages for all four methods. ... 

Betti et al. [85] present a chemometric approach for the analysis of flavonoids and related compounds by planar chromatography. 

While principal components models are used mostly in an unsupervised or exploratory mode, models based on canonical variates are often applied in a supervisory way for the prediction of biological activities from chemical, physicochemical or other biological parameters. In this section we discuss briefly the methods of linear discriminant analysis (LDA) and canonical correlation analysis (CCA). Although there has been an early awareness of these methods in QSAR [7,50], they have not been widely accepted. More recently they have been superseded by the successful introduction of partial least squares analysis (PLS) in QSAR. Nevertheless, the early pattern recognition techniques have prepared the minds for the introduction of modem chemometric approaches. 

Volume 3 Experimental Design A Chemometric Approach, by S.N. Deming and S.L. Morgan... 

Meglen RR (1990J Analytical problem solving, reference materials, and multivariate quality control A chemometrics approach. Fresenius J Anal Chem 338 363-367. 

R. Kaliszan, Structure and Retention in Chromatography. A Chemometric Approach, Harwood Academic Publishers, Amsterdam (1997). 

Deming SN, Morgan SL (1993) Experimental design a chemometric approach, 2nd edn. Elsevier, Amsterdam... 

The NIR spectra contain less structural information than the corresponding IR spectra, since only the overtone absorptions of X-Fl (X = C, N, O) are detected. Using chemometric approaches has, however, enlarged the applications of this method, particularly for quantitative and classification analyses. 

Experimental Design A Chemometric Approach, by S.N. Deming and S.L. Morgan Advanced Scientific Computing in BASIC with Applications in Chemistry, Biology and Pharmacology, by P. Valko and S. Vajda PCs for Chemists, edited by J. Zupan... 

A. Cichelli and G.P. Pertesana, High-performance liquid chromatographic analysis of chlorophylls, pheophytins and carotenoids in virgin olive oils chemometric approach to variety classification. J. Chromatogr.A 1046 (2004) 141-146. 

Despite the broad definition of chemometrics, the most important part of it is the application of multivariate data analysis to chemistry-relevant data. Chemistry deals with compounds, their properties, and their transformations into other compounds. Major tasks of chemists are the analysis of complex mixtures, the synthesis of compounds with desired properties, and the construction and operation of chemical technological plants. However, chemical/physical systems of practical interest are often very complicated and cannot be described sufficiently by theory. Actually, a typical chemometrics approach is not based on first principles—that means scientific laws and mles of nature—but is data driven. Multivariate statistical data analysis is a powerful tool for analyzing and structuring data sets that have been obtained from such systems, and for making empirical mathematical models that are for instance capable to predict the values of important properties not directly measurable (Figure 1.1). 

In this chapter we report recent advantages in analytical method hyphenation and chemometric approach applied to drag development. 

In this chapter we report recent advantages in analytical method hyphenation and chemometric approach applied to drug development, especially related to last trends in pharmaceutical field and to advantages in terms of high-throughputs procedure and instrumentations. 

In terms of computer-based and chemometric approach, additional improvements were also needed in mathematical models for chromatography and in method development, in order to help identifying the correct type of model and the adequate experimental parameters then, application to high volume of generated data is possible. 

With the appearance of chemometric approach, novel hyphenation instrument configurations and the improvement of limit of detections and quantifycations, analyte description and characterization are usually not the rate-limiting step in bioanalysis. 

In the end of the chapter it is also evident how the chemometric approach can be successfully applied in all stages, in particular in order to focus the right tests for method development and to elaborate the large data volume in order to extrapolate the right and principal information and to delete redundant information. 

Similar work was performed by Shaw et al.3 in 1999 when they used FT-Raman, equipped with a charge coupled device (CCD) detector (for rapid measurements) as an on-line monitor for the yeast biotransformation of glucose to ethanol. An ATR (attenuated total reflectance) cell was used to interface the instrument to the fermentation tank. An Nd YAG laser (1064 nm) was used to lower fluorescence interference and a holographic notch filter was employed to reduce Rayleigh scatter interference. Various chemometric approaches were explored and are explained in detail in their paper. The solution was pumped continuously through a bypass, used as a window in which measurements were taken. 

Experimental design a chemometric approach / Stanley N. Deming and Stephen L. Morgan. — 2nd rev. and expanded ed. 

From the outset acoustic chemometrics is fully dependent upon the powerful ability of chemometric full spectrum data analysis to elucidate exactly where in the spectral range (which frequencies) the most influential information is found. The complete suite of chemometric approaches, for example PCA, PLS regression, SIMCA (classification/discrimination) are at the disposition of the acoustic spectral data analyst there is no need here to delve further into this extremely well documented field. (See Chapter 12 for more detail.)... 

The acoustic chemometric approach can also be used to monitor industrial production processes involving particles and powders and to provide a complementary tool for process operators for more efficient process control, or to monitor particle movement in a fluidized bed [7] for example. Below we illustrate the application potential by focusing on two applications process monitoring of a granulation process and monitoring of ammonia concentration. 

A comparison of Figures 9.18 and 9.19 shows that the acoustic chemometric approach is much more sensitive to changes in the process state(s) of the fluidized bed than the traditional process data alone. Of course an industrial implementation of this process monitoring facility would include both acoustic data and process data, together with relevant chemometric data analysis (PCA, PLS) and the resulting appropriate plots. 

Frake et al. compared various chemometric approaches to the determination of the median particle size in lactose monohydrate with calibration models constrncted by MLR, PLS, PCR or ANNs. Overall, the ensuing models allowed mean particle sizes over the range 20-110/tm to be determined with an error less than 5 pm, which is comparable to that of the laser light diffraction method nsed as reference. Predictive ability was similar for models based on absorbance and second-derivative spectra this confirms that spectral treatments do not suppress the scattering component arising from differences in particle size. 

P. Frake, I. Gill, C.N. Luscombe, D.R. Rudd, J. Waterhouse and U.A. Jayasooriya, Near-infrared mass median particle size determination of lactose monohydrate, evaluating several chemometric approaches. Analyst, 123, 2043-2046 (1998). 

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