Multiplicative signal correction

In the previous section, it was noted that the MSC method is expected to perform poorly in cases where spectral offset and multiplicative variations are very small relative to those obtained from chemistry-based variations. In response to this, several methods were developed to enable more accurate multiplicative corrections through better modeling of chemistry-based variations in the data [34-35]. One such method is an extension of the MSC method, appropriately called extended multiplicative signal correction (EMSC) [35-37]. 

H. Martens and E. Stark, Extended multiplicative signal correction and spectral interference subtraction new preprocessing methods for near infrared spectroscopy, J. Pharm. Biomed. Anal, 9, 625-35 (1991). 

H. Martens, J.P. Nielsen and S.B. Engelsen, Light scattering and light absorbance separated by extended multiplicative signal correction. Application to near-infrared transmission analysis of powder mixtures, Anal Chem., 75, 394 (2003). 

Kohler, A., Zimonja, M., Segtnan, V., and Martens, H. (2009). Standard normal variate, multiplicative signal correction and extended multiplicative signal correction preprocessing in biospectroscopy. In "Comprehensive Chemometrics", (S. D. Brown, R. Tauler, and B. Walczak, Eds), Vol. 2, pp. 139-162. Elsevier, Amsterdam. 

Martens, H. and Stark, E., Extended Multiplicative Signal Correction and Spectral Interference Subtraction New Preprocessing Methods for Near Infrared Spectroscopy /. Pharm. Biomed. 

Multiplicative signal correction (MSC) A mathematical treatment of spectra used prior to regression to correct for baseline and offset shifts caused by e.g., a difference in particle size or in colour between samples. Based on a standard spectrum (usually a mean of several good spectra) every sample is corrected for a slope and an offset calcnlated by least squares regression on the standard spectrum. 

Spectral filters The mathematical treatments of NIR spectra prior to regression used to remove variance that only adds to the error term in the calibration model, (i.e., variance not containing systematic information on the sample). Common spectral filters are multiplicative signal correction (MSC), derivatives and smoothing algorithms. 

Figure 6 (A) Reflectance spectra in the near-IR of a number of ethyl celluloses obtained from two vendors. (B) Principal component projection of the spectra in (A) after multiplicative signal correction. The left cluster is from vendor A and the right one from vendor B. (With thanks to Mats Josefson, Astra Hassle/AstraZeneca, Moindal, Sweden.)...

Melting point Mass spectrometry Multiplicative signal correction Microspecular reflectance Molecular weight Neutron activation analysis Nickel oxide... 

Multiplicative signal correction, also known as multiplicative scatter correction (Martens and Naes), was developed to correct for light scattering in reflectance measurements (or measurements containing a strong multiplicative component). Offset and scaling are performed for this algorithm (Fig. 5). 

This resonant Mie scattering effect is the cause of the phenomenon previously referred to as the dispersion artefact , which was an inaccurate description because the effect was not solely due to dispersion and it is not an artefact because it can be explained fully. With an understanding of the physics behind resonant Mie scattering, preliminary algorithms based on the extended multiplicative signal correction (EMSC) have been developed. The EMSC... 

Resonant Mie Scattering Correction using the Extended Multiplicative Signal Correction (RMieS-EMSC)... 

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