2/23/2023 0 Comments Tyrian 2000 special inputDespite their historical significance, icons of the Cretan School have been rarely studied through modern chemical techniques and therefore very few information is available on the materials used by the Cretan painters. The Cretan School of iconography is the last great flowering of the traditional Byzantine painting manner, which is however influenced by different schools and western art. The results achieved open an absolutely new way in Tyrian purple analysis in cultural heritage by non invasive spectroscopic techniques attesting their convergence with HPLC and giving them a semi-quantitative value. To validate this model, archaeological textile fragments dating from the Roman period were successfully examined. snails from those prepared with further mollusc species. The studied correlation also highlights that, independently of the dyeing method and nature of the textile fibre used, the relative content of 6,6′-dibromindigotin may be used as a parameter to distinguish samples prepared with Hexaplex trunculus L. This indicates that the spectral features of Tyrian purple on textile fibre is strictly related to the amount of this indigoid component whose content may be non invasively predicted from reflectance spectrum. A cross-validated PLS model, based on the quantity of 6,6′-dibromoindigotin, displays an excellent correlation factor (R2Y = 0.987) between values determined by chromatography and those predicted from reflectance spectra. This original approach for the study of organic dyes in the cultural heritage field, is based on the correlation of spectrophotometric (UV–Visible) and chromatographic (Fast-HT-HPLC-PDA) data from an extensive set of textiles prepared with different snail species according to historical recipes. In this paper, partial least square (PLS) regression is innovatively applied for a semi-quantitative non invasive study of the most precious dye of Antiquity: Tyrian purple. trunculus in historical objects and increases our knowledge about the dye biosynthesis and technology of Tyrian purple production. Identification of these compounds facilitates the detection of dyestuffs from H. ![]() The unknown compounds appeared to be analogues of indirubin and its mono- and dibrominated derivatives with one CO group in the indirubin backbone substituted by a CNH group. Identification of these compounds was made based on isotopic patterns and accurate mass measurements of protonated molecular ions and their high collision energy fragments obtained in LC-MS/MS experiments. Here, we describe the identification of minor indigoids found in extracts of the pigment obtained from one of the Tyrian purple species, Hexaplex trunculus. In all of these species, indigotin, indirubin and their brominated analogues are the main colouring compounds. Tyrian purple is one of the oldest dyes known to man and derives from different species of marine molluscs. Identification of a particular dye is usually made based on the presence of its main components, while consideration of minor components is important for differentiating between dyes originating from closely related species. Consequently, for the first time, the new analogues of brominated and unbrominated indirubins were found in the shellfish purple from Hexaplex trunculus.Īnalysis of natural dyes in historical objects is important for both conservation purposes and to determine the origin and culture that produced it. Using them, the detection and quantification of trace Tyrian purple components (less than 0.15%) aside from major indigoids becomes possible. The upper quantification limit for 6,6'-dibromoindigotin was improved by over 350%, between standard and optimised systems. The best results were obtained using highly retentive, but moderately bonded ODS stationary phases (about 2.8 μmol m(-2)), percolated with gradient of acetonitrile with acidified aqueous mobile phases (0.1% strong acid) at elevated temperatures (70☌). The influence of various factors was evaluated: stationary phase characteristics, mobile phase composition, elution gradient parameters and temperature on the peak shape of the main components of Tyrian purple. ![]() Our study focused on improving both symmetry and peak height for more precise quantification. ![]() This is due to the low solubility of the indigoids and their brominated derivatives in the mobile phase, especially 6,6'-dibromoindigotin, which is soluble in only few, particular solvents. Attempts at identification of mollusc species producing Tyrian purple from archaeological material are usually done with high performance liquid chromatography in the reversed-phase system, but the peaks obtained are often wide and asymmetric.
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