On the reliability of historic books as sources of reference samples of early synthetic dyes – The case of “The Coal Tar Colours of the Farbwerke vorm. Meister, Lucius & Brüning, Höchst on the Main, Germany – A General Part” (1896)

Abstract

• The swatches present in the popular book “The Coal Tar Colours of the Farbwerke vorm. Meister Lucius & Brüning, Höchst on the Main, Germany – A General Part”, published in 1896, were analysed by high performance liquid chromatography coupled to diode array detector and high-resolution tandem mass spectrometry (HPLC-DAD-MS/MS) with the aim to identify the synthetic dyes and reveal the correspondences and discrepancies between the information reported in the labels and the actual chemical composition of the samples. The research resulted in guidelines to be followed to connect commercial dye names with Colour Index (C.I.) constitution numbers and produced a molecular database of more than 250 molecules, whose high-resolution mass spectrometric details are reported here for the first time in some cases. Out of 120 samples analysed, ca. 40% did not exactly correspond to the expected dye(s) according to the labels, thus raising awareness of the challenges related to the reliability of historic sources of reference materials and the need to study the composition of these historic samples before using them for chemical research purposes. Furthermore, molecular databases of synthetic dyes are fundamental for the correct identification of these materials in historic textiles, objects and works of art. Thus, the results of this research are extremely useful to all researchers studying dyed objects produced from the second half of the 19th century onwards.