微量天然蚕丝样品的锶同位素组成高精度测定及产地溯源

High-Precision Determination of Strontium Isotopic Composition in Trace-Level Natural Silk Samples and Geographic Origin Traceability

  • 摘要: 丝绸作为古代丝绸之路最具代表性的贸易载体,其产地溯源研究长期依赖艺术史学方法,缺乏基于自然科学的精准判别技术。放射性锶同位素(87Sr/86Sr)因具有鲜明的地域特征,被认为是最具潜力的溯源技术之一,其应用已从传统地质学领域广泛拓展至文物考古领域。蚕丝是丝绸的主要纺织材料,具有高有机质(>95%)、低锶含量(~1μg/g)等特性。然而,现有地质样品分析方法通常需消耗整个或多个蚕茧(数百毫克),难以满足珍贵丝绸文物的微损耗分析要求。本文研究建立了一种微量蚕丝样品高精度锶同位素分析技术。通过强氧化剂(浓硝酸-双氧水)消解结合锶特效树脂柱纯化,在高效去除有机质的同时,实现高锶回收率(>99%)和超低流程本底(≤35pg)。纯化后的样品采用热电离质谱仪(TIMS)进行测定,结合“三明治”点样法和钨硅酸发射剂,将电离效率提升至10%,对低至0.5ng的NBS987锶同位素标准物质进行测定,获得87Sr/86Sr比值为0.710251±0.000033(n=31,2SD),与参考值一致。该方法仅需消耗大约10mg蚕丝样品,较传统方法耗样量降低1~2个数量级。应用该技术对我国五大主产区不同品种蚕茧进行测定,发现蚕丝的锶同位素呈现地域与品种双重控制特征,其中地域因素起主导作用,证实锶同位素指纹作为丝绸产地溯源指标的可行性。本研究突破了微量蚕丝样品的锶同位素分析技术瓶颈,为丝绸文物微损溯源提供了技术支撑。

     

    Abstract: As one of the most representative trade commodities along the ancient Silk Road, silk artifacts have long been studied for provenance using art historical methodologies, yet lack scientifically rigorous analytical techniques grounded in the natural sciences. Radiogenic strontium (Sr) isotopes (87Sr/86Sr), known for their distinct geographical signatures, have emerged as a promising tracing tool for tracing provenance, with applications extending from geology into archaeology. Silkworm cocoons, the primary textile material for silk, exhibit high organic content (>95%) and low Sr concentrations (~1μg/g). Conventional geological analysis methods typically require large sample sizes (entire or multiple cocoons or several hundred milligrams), making them unsuitable for minimally destructive analysis of precious silk artifacts. In this study, we developed a high-precision Sr isotope analysis technique tailored for trace amounts of silk. By combining strong oxidant digestion (HNO3-H2O2) with Sr-specific resin purification, we achieved efficient organic matrix removal while maintaining high strontium recovery (>99%) and ultra-low procedural blanks (≤35pg). Purified samples were analyzed using thermal ionization mass spectrometry (TIMS) with a “sandwich” loading technique and silicotungstic acid emitter, enhancing ionization efficiency to 10%. The method reliably measured as little as 0.5ng of the NBS987 standard, yielding a mean 87Sr/86Sr ratio of 0.710251±0.000033 (n=31, 2SD), consistent with certified values. This approach reduces sample consumption to approximately 10mg per analysis, representing a 1–2 order of magnitude improvement over conventional methods. This technique was then applied to cocoons of various silkworm breeds from China’s five major silk-producing regions. The results revealed that Sr isotopic signatures of silk are influenced by both geographic origin and silkworm variety, with regional factors playing a dominant role. This confirms the viability of Sr isotopes as silk provenance indicators. Our technical breakthroughs in Sr isotope analysis of trace silk samples, providing a foundational analytical framework for minimally invasive provenance studies of silk artifacts.

     

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