Leona Marco
Department of Scientific Research, The Metropolitan Museum of Art, 1000 Fifth Avenue, New York, NY 10028, USA.
Proc Natl Acad Sci U S A. 2009 Sep 1;106(35):14757-62. doi: 10.1073/pnas.0906995106. Epub 2009 Aug 10.
Scientific studies of works of art are usually limited by severe sampling restrictions. The identification of organic colorants, a class of compounds relevant for attribution and provenance studies, is further complicated by the low concentrations at which these compounds are used and by the interference of the protein-, gum-, or oil-binding media present in pigment and glaze samples. Surface-enhanced resonance Raman scattering (SERRS) was successfully used to identify natural organic colorants in archaeological objects, polychrome sculptures, and paintings from samples smaller than 25 microm in diameter. The key factors in achieving the necessary sensitivity were a highly active stabilized silver colloid, obtained by the reproducible microwave-supported reduction of silver sulfate with glucose and sodium citrate, and a non-extractive hydrolysis sample treatment procedure that maximizes dye adsorption on the colloid. Among the examples presented are the earliest so far found occurrence of madder lake (in a 4,000 years old Egyptian object dating to the Middle Kingdom period), and the earliest known occurrence in Europe of the South Asian dyestuff lac (in the Morgan Madonna, a 12th century polychrome sculpture from Auvergne, France).
对艺术作品的科学研究通常受到严格的抽样限制。有机着色剂是一类与艺术品归属和出处研究相关的化合物，由于其使用浓度低以及颜料和釉料样品中存在的蛋白质、树胶或油基介质的干扰，对其进行鉴定变得更加复杂。表面增强共振拉曼散射（SERRS）已成功用于鉴定考古文物、彩色雕塑和直径小于25微米的绘画样本中的天然有机着色剂。实现所需灵敏度的关键因素包括：通过用葡萄糖和柠檬酸钠对硫酸银进行可重复的微波辅助还原获得的高活性稳定化银胶体，以及使染料在胶体上的吸附最大化的非萃取水解样品处理程序。所举例子包括迄今为止发现的最早的茜草湖（在一件可追溯到中王国时期的4000年前的埃及文物中），以及欧洲已知最早出现的南亚染料虫胶（在摩根圣母像中，这是一件来自法国奥弗涅的12世纪彩色雕塑）。
