The introduction of synthetic dyes completely changed the industrial production and use of colorants for art materials. From the synthesis of the first synthetic dye, mauveine, in 1856 until today, artists have enjoyed a wider range of colors and selection of chemical properties than was ever available before. However, the introduction of synthetic dyes introduced a wider variety and increased the complexity of the chemical structures of marketed dyes. This work looks towards the analysis of synthetically dyed objects in heritage collections, applying an extraction protocol based on the use of ammonia, which is considered favorable for natural anthraquinone dyes but has never before been applied to acid synthetic dyes. This work also presents an innovative cleanup step based on the use of an ion pair dispersive liquid–liquid microextraction for the purification and preconcentration of historical synthetic dyes before analysis. This approach was adapted from food science analysis and is applied to synthetic dyes in heritage science for the first time in this paper. The results showed adequate recovery of analytes and allowed for the ammonia-based extraction method to be applied successfully to 15 samples of suspected azo dyes from the Azienda Coloranti Nazionali e Affini (ACNA) synthetic dye collection, identified through untargeted HPLC-HRMS analyses.

The anthraquinoid vat dyes, first discovered in 1901, represent a culturally and scientifically important dye class. Their stable, low polarity, polycyclic aromatic structures provide them with excellent light- and wash-fastness properties, which impacted twentieth-century textile design, manufacture, and use. These chemical properties differentiate them from other early synthetic dyes. As a result, liquid chromatography methods designed for other historical dyes have been unable to detect them in historical textiles. Their impact on twentieth-century textile production has therefore been under-recognised. This article presents a novel method for the characterisation of anthraquinoid vat dyes on historical textiles using ultra-high performance liquid chromatography coupled with photodiode array detection and mass spectrometry (uHPLC-DAD-MS). This work represents the first known uHPLC study into this historically significant group of dyes and offers new absorbance spectra and mass spectrometric data about these little-researched molecules. The method is validated through application to historical dyed yarn samples from Vat Colors on Cotton, a commercial pattern book published by DuPont (ca. 1940). Across 15 samples, 10 distinct anthraquinoid vat dyes were successfully characterised using the novel method. This method facilitates the identification of these dyes in historical textiles, offering new insights into textile history and artefact conservation.