title: Characterization of synthetic dyes by comprehensive two-dimensional liquid chromatography combining ion-exchange chromatography and fast ion-pair reversed-phase chromatography.
abstract: In the late 19th century, newly invented synthetic dyes rapidly replaced the natural dyes on the market. The characterization of mixtures of these so-called early synthetic dyes is complicated through the occurrence of many impurities and degradation products. Conventional one-dimensional liquid chromatography does not suffice to obtain fingerprints with sufficient resolution and baseline integrity. Comprehensive two-dimensional liquid chromatography (LC×LC) is employed in this study, with ion-exchange chromatography in the first dimension and fast ion-pair liquid chromatography in the second. Retention in the first dimension is largely determined by the number of charges, while the selection of a small ion-pair reagent (tetramethylammonium hydroxide) in the second dimension causes retention to be largely determined by the molecular structure of the dye. As a result, there is a high degree of orthogonality of the two dimensions, similar to the values typically encountered in GC×GC. The proposed LC×LC method shows a theroretical peak capacity of about 2000 in an analysis time of about three hours. Clear, informative fingerprints are obtained that open a way to a more efficient characterization of dyes used in objects of cultural heritage.
authors: University of Amsterdam, van 't Hoff Institute for Molecular Sciences, Analytical-Chemistry Group, Science Park 904, 1098 XH Amsterdam, The Netherlands; TI-COAST, Science Park 904, 1098 XH Amsterdam, The Netherlands. Electronic address: B.W.J.Pirok@uva.nl.
authors: Bob W J
authors: BW
authors: Pirok
authors: University of Amsterdam, van 't Hoff Institute for Molecular Sciences, Analytical-Chemistry Group, Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors: Jitske
authors: J
authors: Knip
authors: University of Amsterdam, van 't Hoff Institute for Molecular Sciences, Analytical-Chemistry Group, Science Park 904, 1098 XH Amsterdam, The Netherlands; University of Amsterdam, Faculty of Humanities, Conservation and Restoration of Cultural Heritage, Johannes Vermeerplein 1, 1071 DV, Amsterdam, The Netherlands.
authors: Maarten R
authors: MR
authors: van Bommel
authors: University of Amsterdam, van 't Hoff Institute for Molecular Sciences, Analytical-Chemistry Group, Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors: Peter J
authors: PJ
authors: Schoenmakers
mesh_terms: D002852:Chromatography, Ion Exchange / Q000379:methods; D056148:Chromatography, Reverse-Phase / Q000379:methods; D004396:Coloring Agents / Q000032:analysis*
chemical_list: D004396:Coloring Agents
keywords: Art conservation; Comprehensive two-dimensional liquid chromatography; Early synthetic dyes; Fast ion-pair LC; LC×LC