An improved dye and lake pigment analysis method for high-performance liquid chromatography and diode-array detector

Abstract

A new analytical method for characterizing a wide range of organic colorants is described. Using a high-performance liquid chromatograph (HP LC) equipped with a diode-array detector (DAD), this method uses a water/acetonitrile gradient with 0·1% trifluoroacetic acid. This system has been used to analyze a wide variety of colorants, including Indian yellow and gamboge, as well as traditional lake pigments and dyes. Dye extracts of fibers taken from Gobelins furniture tapestries (National Gallery of Art, Washington DC) and lake pigments from Winslow Homer's watercolor box (Portland Museum of Art) were successfully analyzed using this technique. Cochineal and indigo were identified in both dye and lake pigment samples. Gamboge was found as a watercolor pigment, while weld and at least two types of madder dyestuff were present in the Gobelins samples. Novel lines of investigation into artists' materials and techniques are proposed based on the high sensitivity of this HPLC-DAD method.