Analysis of early synthetic dyes with HPLC-DAD-MS: an important database for analysis of colorants used in cultural heritage

Presented thesis at Faculdade de Ciências e Tecnologias, Universidade de Lisboa, to obtain the Master Degree in Conservation and Restoration of Textiles

The analysis of 62 early synthetic dyes from the Smithsonian‟s Helmut Schweppe Collection with High Performance Liquid Chromatography – Diode Array Detection – Mass Spectrometry (HPLC-DAD-MSn) was performed. Several chromatographic and mass parameters were optimized in order to characterize the 62 dyes. This approach was also applied to selected natural dyes because early synthetic dyes were known to be dyed together with dyes from natural biological sources. Prior to the HPLC-DAD-MSn analysis, soft extraction methods were tested on dyed textiles. In the present study it was possible to characterize the 62 dyes from 11 chemical families as well as selected natural dyes using the same methodology. Also the soft extraction methods were successful in both synthetic and natural dyes recovery. This HPLC-DAD-MSn database was compared with samples from a Persian carpet, from 20th century. It was possible to conclude that the carpet was dyed with synthetic dyes. The yellow and beige colours were obtained with a mixture of azo flavine 3R (CI 13090) and orange IV (13080,) and the red colours were obtained with scarlet n for silk (CI 15635) and cotton scarlet (CI 27290). The blue colours were obtained with synthetic dyes probably from the tryarilmethane family. The green colour was obtained with a mixture of the yellow and blue synthetic dyes mentioned previously.