Characterization of synthetic dyes by comprehensive two-dimensional liquid chromatography combining ion-exchange chromatography and fast ion-pair reversed-phase chromatography

J Chromatogr A. 2016 Mar 4:1436:141-6. doi: 10.1016/j.chroma.2016.01.070. Epub 2016 Jan 30.

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.

Keywords: Art conservation; Comprehensive two-dimensional liquid chromatography; Early synthetic dyes; Fast ion-pair LC; LC×LC.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatography, Ion Exchange / methods
  • Chromatography, Reverse-Phase / methods
  • Coloring Agents / analysis*

Substances

  • Coloring Agents