title: Speciation of adsorbates on surface of solids by infrared spectroscopy and chemometrics.
abstract: Speciation, i.e. identification and quantification, of surface species on heterogeneous surfaces by infrared spectroscopy is important in many fields but remains a challenging task when facing strongly overlapped spectra of multiple adspecies. Here, we propose a new methodology, combining state of the art instrumental developments for quantitative infrared spectroscopy of adspecies and chemometrics tools, mainly a novel data processing algorithm, called SORB-MCR (SOft modeling by Recursive Based-Multivariate Curve Resolution) and multivariate calibration. After formal transposition of the general linear mixture model to adsorption spectral data, the main issues, i.e. validity of Beer-Lambert law and rank deficiency problems, are theoretically discussed. Then, the methodology is exposed through application to two case studies, each of them characterized by a specific type of rank deficiency: (i) speciation of physisorbed water species over a hydrated silica surface, and (ii) speciation (chemisorption and physisorption) of a silane probe molecule over a dehydrated silica surface. In both cases, we demonstrate the relevance of this approach which leads to a thorough surface speciation based on comprehensive and fully interpretable multivariate quantitative models. Limitations and drawbacks of the methodology are also underlined.
authors.affiliation: Laboratoire Catalyse et Spectrochimie, ENSICAEN-Université de Caen-CNRS, 6 Boulevard Maréchal Juin, 14050 Caen, France; Manufacture Française des Pneumatiques Michelin, Place des Carmes, 63040 Clermont Ferrand Cedex 9, France. Electronic address: franck.vilmin@fr.michelin.com.
authors.forename: Franck
authors.initials: F
authors.lastname: Vilmin
authors.affiliation: Laboratoire Catalyse et Spectrochimie, ENSICAEN-Université de Caen-CNRS, 6 Boulevard Maréchal Juin, 14050 Caen, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Bazin
authors.affiliation: Laboratoire Catalyse et Spectrochimie, ENSICAEN-Université de Caen-CNRS, 6 Boulevard Maréchal Juin, 14050 Caen, France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Thibault-Starzyk
authors.affiliation: Laboratoire Catalyse et Spectrochimie, ENSICAEN-Université de Caen-CNRS, 6 Boulevard Maréchal Juin, 14050 Caen, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Travert
mesh_terms: D000327:Adsorption; D015999:Multivariate Analysis; D012821:Silanes / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods*; D013499:Surface Properties; D014867:Water / Q000737:chemistry*
chemical_list: D012821:Silanes; D014867:Water; D012822:Silicon Dioxide
keywords: Adsorption; Multivariate calibration; Multivariate curve resolution; Silica; Water