Chromatographic Investigations of Purple Archaeological Bio-Material Pigments Used as Biblical Dyes
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Chromatographic Investigations of Purple Archaeological Bio-Material Pigments Used as Biblical Dyes Zvi C. Koren The Edelstein Center for the Analysis of Ancient Artifacts, Department of Chemical Engineering, Shenkar College of Engineering and Design, 12 Anna Frank St., 52526 Ramat-Gan, Israel. e-mail: [email protected]
ABSTRACT This article discusses recent scientific research performed by the author in understanding the composition of archaeological purple pigments and dyes from molluskan sources, which were primarily used for the dyeing of royal and priestly textiles, as also cited in the Bible. Towards this end, the high-performance liquid chromatography (HPLC) method has been applied to the qualitative and quantitative multi-component fingerprinting of purple pigments extracted from various Muricidae mollusks inhabiting the Mediterranean waters. The results show that the colorants in these purple pigments belong to three chemical groups: the indigoids (of major importance), the indirubinoids, and the isatinoids. Application of this analytical method to purple pigments and dyes on archaeological artifacts from the ancient Near and Middle East has lead to a number of breakthroughs and discoveries made by this laboratory. These include the following: decipherment of the optimal method by which the ancients practiced purple-dyeing by completely natural means; first HPLC analysis of a raw unprocessed purple archaeological snail pigment and the resulting identification of a dibrominated indirubin in this pigment; discovery of the purple pigment as the sole paint pigment on a 2,500 royal marble jar from the Persian King Darius I; and the discovery that a 2,000 year old miniscule fabric found atop the Judean Desert palatial fortress of Masada belonged to the royal purple mantle of King Herod I and is the first Biblical Argaman dye found in ancient Israel. INTRODUCTION The analysis of cultural heritage textile dyes and pigments from organic sources – flora and fauna – requires the use of micro-sampling in order to extract the maximum information regarding these colorants. Non-destructive investigations have been shown to be excellent for the identification of inorganic pigments. However, they are at best limited in their ability to produce a full scientific fingerprinting of natural organic dyestuffs, which contain numerous components. The optimal technique for studying organic dyes and pigments requires a separation method, especially HPLC (high-performance liquid chromatography) followed by spectrometric detection of the visible- and UV-absorbing components. The latter is best performed with a photodiode array (PDA) detector, which can then be linked to a mass spectrometer (MS) for the identification of hitherto unknown colorants. This paper will address the recent discoveries of purple pigments produced from various molluskan sources found in textiles and objects from more than two millennia ago. The purple of the ancients is undoubtedly the most fascinating and mystifyingly complex pigment of all the natural colora
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