Indirect hard modeling

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Indirect Hard Modeling (IHM) is a non-linear multivariate analysis method for the quantitative investigation of spectra or, in general, of peak- shaped data, for example chromatograms .

IHM can be used to determine a measured variable from the measurement data of a sample, i. d. Usually the concentration of the constituents of the sample. In contrast to the classic data-driven linear processes, IHM uses a deterministic non-linear model, which corresponds to a rigorous mathematical formulation of the physical relationships between the measured variable and the measured data. It consists of two sub-models. The model of the spectrum (or chromatogram) results as a weighted sum of so-called hard models of the spectra of the individual components of the sample. Each hard model in turn corresponds to a weighted sum of parameterized peak functions. The second partial model is a functional relationship between the weights determined in the first partial model and the measured variable sought, which can often be assumed to be linear for physical reasons. The name of the method is explained by the fact that the measurement signal of a mixture is not modeled directly by adapting bands, but based on the hard models of the components.

background

history

The IHM procedure was developed at RWTH Aachen University and first published in 2004. Extensions for the identification of unknown partial models (Complemental Hard Modeling, CHM, and Hard Modeling Factor Analysis, HMFA, which takes up ideas from the main component analysis ) took place in 2008.

Until 2010, IHM and related hard modeling methods were further developed at RWTH in a software called PEAXACT. At the end of 2011, the RWTH licensed the PEAXACT exploitation rights to the Aachen-based company S-PACT GmbH, which has been following developments since then.

application

Due to the use of a deterministic model, the application of IHM is not universally suitable for multivariate statistical questions, but is specifically geared towards the analysis of peak-shaped data. Their field of application is therefore within instrumental analytical chemistry , especially spectroscopy and chromatography.

Scientific publications currently exist dealing with the application of IHM to infrared and Raman spectra .

literature

Web links