title: Micro-Raman spectroscopy and chemometrical analysis for the distinction of copper phthalocyanine polymorphs in paint layers.
abstract: In art analysis, copper phthalocyanine (CuPc) is often identified as an important pigment (PB15) in 20th century artworks. Raman spectroscopy is a very valuable technique for the detection of this pigment in paint systems. However, PB15 is used in different polymorphic forms and identification of the polymorph could retrieve information on the production process of the pigment at the moment. Raman spectroscopy, being a molecular spectroscopic method of analysis, is able to discriminate between polymorphs of crystals. However, in the case of PB15, spectral interpretation is not straightforward, and Raman data treatment requires some improvements concerning the PB15 polymorphic discrimination in paints. Here, Raman spectroscopy is combined with chemometrical analysis in order to develop a procedure allowing us to identify the PB15 crystalline structure in painted layers and in artworks. The results obtained by Linear Discriminant Analysis (LDA), using intensity ratios as variables, demonstrate the ability of this procedure to predict the crystalline structure of a PB15 pigment in unknown paint samples.
authors.affiliation: Centre Européen d'Archéometrie and Institut de Physique Nucléaire, Atomique et de Spectroscopie, Universié de Liège, B-4000 Liège, Belgium. Catherine.defeyt@ulg.ac.be
authors.forename: C
authors.initials: C
authors.lastname: Defeyt
authors.forename: J
authors.initials: J
authors.lastname: Van Pevenage
authors.forename: L
authors.initials: L
authors.lastname: Moens
authors.forename: D
authors.initials: D
authors.lastname: Strivay
authors.forename: P
authors.initials: P
authors.lastname: Vandenabeele
mesh_terms: D001154:Art; D004396:Coloring Agents / Q000032:analysis; D062126:Databases, Chemical; D016002:Discriminant Analysis; D007211:Indoles / Q000032:analysis*; D015591:Microspectrophotometry / Q000379:methods*; D009942:Organometallic Compounds / Q000032:analysis*; D010150:Paint / Q000032:analysis*; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D004396:Coloring Agents; D007211:Indoles; D009942:Organometallic Compounds; C015445:copper phthalocyanine
keywords: Chemometrics; Copper phthalocyanine polymorphs; PB15; Raman spectroscopy