Calibration partial least squares

Fig. 17 Carbon monoxide concentration traces for IM16 reference cigarette smoke runs a with 3-m multipass and b HWG gas cells (dashed line nondispersive IR (NDIR) analyzer, solid line FT-IR spectrometer using partial least-squares calibrations) [43]...

Brekke, T, (1989). Prediction of Physical Properties of Hydrocarbons Mixtures by Partial-Least-Squares Calibration of Carbon-13 Nuclear Magnetic Resonance Data. Anal.Chim.Acta, 223, 123-134. 

A. Safavi, H. Abdollahi, and R. Mirzajani. Simultaneous spectrophotometric determination of Fe(III), Al(III) and Cu(II) by partial least-squares calibration method. Spectrochimica Acta Part A 63 196-199, 2006. 

Partial least-squares calibration uses the covariance between the data matrix X and another matrix Y (property matrix). Here, the score vectors are orthogonal, but the loading vectors become oblique. 

Partial least-squares calibration plots of olive oil adulterated by four adulterants (sunflower oil, soya oil, hazelnut oil, and walnut oil) are shown in Figure 6.3. The statistics of these calibrations are given in Table 6.2. The figures and the table reveal excellent correlations between the measured and predicted values of the adulterants in olive oil. 

Hidajat, K Chong, S.M., Quality Characterization of Crude Oils by Partial Least Square Calibration of NIR Spectral profiles , J. Near Infrared Spectrosc., 2000, 8, 53-59. 

N Everall, K Davis, H Owen, MJ Pelletier, J Slater. Density mapping in poly(ethylene terephthal-ate) using a fiber-coupled Raman microprobe and partial least-squares calibration. Appl Spectrosc 50 388-393, 1996. 

NJ Everall, JM Chalmers, R Ferwerda, JH van der Maas, PJ Hendra. Measurements of poly (aryl ether ether ketone) crystallinity in isotropic and uniaxial samples using Fourier transform-Raman spectroscopy a comparison of univariate and partial least-squares calibrations. J Raman Spectrosc 35 43-51, 1994. 

KPJ Williams, NJ Everall. Use of micro Raman spectroscopy for the quantitative determination of polyethylene density using partial least squares calibration, J Raman Spectrosc 26 427-433,... 

Li, B., D. Wang, J. Lv et al. 2006. Flow-injection chemiluminescence simultaneous determination of cobalt(II) and copper(II) using partial least squares calibration. Talanta 69 160-165. 

Simultaneous determination of AA and L-cysteine (Cys) with partial least squares calibration. This method is based on the fact that both analytes can quantitatively reduce Fe + to Fe +, and that the reaction rates of AA and Cys with Fe + are different. The reduced product, Fe, is detected with the luminol-Fe -02 chemiluminescent system 0.17 No data 3.2 Pharmaceuticals, urine 2005 126... 

Based on that AA could inhibit the chemiluminescent reaction of glyoxal and potassium permanganate in hydrochloric acid Simultaneous determination of AA and rutin (RT) using partial least squares calibration. Method based on the fact that AA and RT can reduce Fe to Fe + at different reaction rates... 

B. Li, D. Wang, C. Xu, Z. Zhang. 2005. Flow-injection simultaneous chemiluminescence determination of ascorbic acid and L-cysteine with partial least squares calibration. Microchim. Acta 149(3-4) 205-212. 

Diaz G. T., Meras I. D., Cabanillas, A. G. Alexandre F. M. F. (2004). Voltammetric behavior and determination of tocopherols with partial least squares calibration Analysis in vegetable oil samples. Anal. Chim. Acta, 511,231-238. 

Details are given of the effects of sterilisation methods on the wear and changes in physical properties of ultra-high molecular weight PE acetabular cups. The crystallinity of the cups was evaluated by micro-Raman spectroscopy as a function of the inner surface position. The partial least square calibration was used to correlate the Raman spectra with the crystallinity of the polymer measured by DSC. 52 refs. 

Mancozeb is a dithiocarbamate pesticide with a very low solubility in organic and inorganic solvent. In this work we have developed a solvent free, accurate and fast photoacoustic FTIR-based methodology for Mancozeb determination in commercial fungicides. The proposed procedure was based on the direct measurement of the solid samples in the middle infrared region using a photoacoustic detector. A multivariate calibration approach based on the use of partial least squares (PLS) was employed to determine the pesticide content in commercially available formulations. 

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. 

Haaland, D.M., Thomas, E.V., "Partial Least-Squares Methods for Spectral Analysis 1. Relation to Other Quantitative Calibration Methods and the Extraction of Qualitative Information" Anal. Chem. 1988 (60) 1193-1202. 

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. ... 

Capitan-Vallvey, L.F. et al.. Simultaneous determination of the colorants tartrazine, ponceau 4R and sunset yellow FCF in foodstuffs by solid phase spectrophotometry using partial least square multivariate calibration, Talanta, 47, 861, 1998. 

Bozdogan, A., Ozgur, U.M., and Koyuncu, L, Simultaneous determination of sunset yellow and Ponceau 4R in gelatin powder by derivative spectrophotometry and partial least-squares multivariate spectrophotometric calibration, Anal. Lett., 33, 2975, 2000. 

We will see that CLS and ILS calibration modelling have limited applicability, especially when dealing with complex situations, such as highly correlated predictors (spectra), presence of chemical or physical interferents (uncontrolled and undesired covariates that affect the measurements), less samples than variables, etc. More recently, methods such as principal components regression (PCR, Section 17.8) and partial least squares regression (PLS, Section 35.7) have been... 

E. Vigneau, D. Bertrand and E.M. Qannari, Application of latent root regression for calibration in near-infrared spectroscopy. Comparison with principal component regression and partial least squares. Chemometr. Intell. Lab. Syst., 35 (1996) 231-238. 

Manne R (1987) Analysis of two partial-least-squares algorithms for multivariate calibration. Chemom Intell Lab Syst 2 187... 

In their day, Principal Components and Partial Least Squares were each considered almost as the magic answer to all calibration problems . It took a long time for the realization to dawn that they contain no magic and are subject to most of the... 

Always based on the use of IR spectrophotometry, a novel attenuated total reflection-Fourier-transform infrared (ATR-FTIR) sensor [42] was proposed for the on-line monitoring of a dechlorination process. Organohalogenated compounds such as trichloroethylene (TCE), tetrachloroethylene (PCE) and carbon tetrachloride (CT) were detected with a limit of a few milligrams per litre, after extraction on the ATR internal-reflection element coated with a hydro-phobic polymer. As for all IR techniques, partial least squares (PLS) calibration models are needed. As previously, this system is promising for bioprocess control and optimization. 

The application of near-IR spectroscopy for real-time monitoring of glucose, lactic acid, acetic acid and biomass in liquid cultures of microorganisms of the genera Lactobacillus and Staphylococcus has been recently published [76]. The NIR spectrum acquired by the optical-fibre probe immersed in the culture is exploited using a partial least squares (PLS) calibration step, a classical method for IR techniques. 

The infrared technique has been described in numerous publications and recent reviews were published by Davies and Giangiacomo (2000), Ismail et al. (1997) and Wetzel (1998). Very few applications have been described for analysis of additives in food products. One interesting application is for controlling vitamin concentrations in vitamin premixes used for fortification of food products by attenuated total reflectance (ATR) accessory with Fourier transform infrared (FTIR) (Wojciechowski et al., 1998). Four vitamins were analysed - Bi (thiamin), B2 (riboflavin), B6 (vitamin B6 compounds) and Niacin (nicotinic acid) - in about 10 minutes. The partial least squares technique was used for calibration of the equipment. The precision of measurements was in the range 4-8%, similar to those obtained for the four vitamins by the reference HPLC method. 

This chapter ends with a short description of the important methods, Principal Component Regression (PCR) and Partial Least-Squares (PLS). Attention is drawn to the similarity of the two methods. Both methods aim at predicting properties of samples based on spectroscopic information. The required information is extracted from a calibration set of samples with known spectrum and property. 

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