Supercritical Fluid Extraction: A Non-Destructive Pre-Treatment Method for Plasma Oxidation & AMS Radiocarbn Dating

超临界流体萃取：等离子体氧化的无损预处理方法

• 批准号: 1006001
• 负责人: Karen Steelman
• 金额: $ 19.36万
• 依托单位: University of Central Arkansas
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-10-01 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1006001&HistoricalAwards=false
• 关键词: Supercritical; Fluid; Extraction; Non; Destructive

With National Science Foundation support, Drs. Karen Steelman and Kyle Felling of the University of Central Arkansas and Dr. Jerry King of the University of Arkansas at Fayetteville will investigate the use of supercritical fluids to remove organic contamination from archaeological artifacts. This will further develop non-destructive radiocarbon dating methods. The research conducted will bring together faculty and undergraduate students from diverse areas of chemistry and chemical engineering, as well as strengthening collaboration with archaeologists across the globe.When an archaeological artifact is radiocarbon dated, it typically undergoes three separate steps: (1) chemical pre-treatment to remove contamination or isolation of sample-specific chemical compounds; (2) conversion of the carbon to a measurable form; and (3) measurement of 14C to determine age. The most widely used methods for steps 1 and 2 are acid-base-acid treatments (ABA) followed by combustion of the sample, both of which are destructive. Plasma oxidation provides the ability to collect microscopic amounts of carbon from an artifact surface non-destructively. A need for an equally non-intrusive pre-treatment method to remove organic contamination is also essential.Supercritical fluid extraction, specifically with the use of carbon dioxide (scCO2), has advantages over a traditional solvent extraction in that it is clean, has a lack of surface tension effects which minimizes distortion of treated samples, and diffuses rapidly through materials. Through manipulation of pressure and temperature, the solvating strength of the fluid can be adjusted to preferentially dissolve different contaminants both on the artifact surface and those that are absorbed throughout the material. The combined use of scCO2 extraction and plasma oxidation has the potential to resolve one of the major problems facing archaeologists working with rare, unique, or sacred objects - the need to place artifacts in a secure chronological context is often offset by a reluctance to destroy even the small part that must be removed for combustion using current dating methods. Furthermore, by exploring non-traditional chemical pre-treatments for radiocarbon dating, a deeper understanding of separations of organic matter from a variety of matrices will be achieved. The initial project outlined in this proposal will give a knowledge base upon which to apply to future studies, such as the conservation or cleaning of artifacts and removal of pesticides from Native American items for repatriation.Undergraduate students in the researchers' laboratories will benefit from exposure to these advanced technologies and research. Promoting science and archaeology within the state of Arkansas is crucial to developing trained professionals in these fields, especially at a university where ~18% of students come from counties in the lowest quartile of per capita income and from the historically depressed Mississippi Delta region of the state. More scientists with interests in applying chemical knowledge to archaeological and cultural applications are needed.

在国家科学基金会的支持下，中阿肯色大学的凯伦·斯蒂尔曼博士和凯尔·费林博士以及阿肯色大学费耶特维尔分校的曾傑瑞·金博士将研究使用超临界流体去除考古文物中的有机污染。这将进一步发展非破坏性放射性碳测年方法。这项研究将汇集来自化学和化学工程不同领域的教职员工和本科生，并加强与全球各地考古学家的合作。当考古文物被放射性碳测年时，它通常经历三个独立的步骤：(1)化学前处理，以去除污染或分离特定样本的化合物；(2)将碳转化为可测量的形式；以及(3)测量14C以确定年代。步骤1和步骤2最广泛使用的方法是酸碱-酸处理(ABA)，然后燃烧样品，这两种方法都是破坏性的。等离子体氧化提供了从人工制品表面非破坏性地收集微量碳的能力。超临界流体萃取，特别是使用二氧化碳(ScCO2)，与传统的溶剂萃取相比具有优势，因为它是清洁的，没有表面张力效应，最大限度地减少了处理样品的扭曲，并在材料中快速扩散。通过控制压力和温度，可以调整流体的溶解强度，以优先溶解人工制品表面上的不同污染物和被整个材料吸收的污染物。结合使用scCO2提取和等离子体氧化，有可能解决考古学家在处理稀有、独特或神圣物品时面临的主要问题之一--将文物放在安全的年代背景下的必要性往往被不愿销毁的一小部分所抵消，而使用目前的测年方法，这些文物必须被移除以燃烧。此外，通过探索放射性碳测年的非传统化学前处理，将实现对有机质从各种基质中分离的更深层次的理解。这项建议中概述的最初项目将提供一个知识基础，用于未来的研究，如文物的保护或清洁，以及从美洲原住民物品中移除杀虫剂以供遣返。研究人员实验室的本科生将受益于接触到这些先进的技术和研究。在阿肯色州推广科学和考古学对于培养这些领域训练有素的专业人员至关重要，特别是在一所大学，大约18%的学生来自人均收入最低四分之一的县和该州历史上经济低迷的密西西比三角洲地区。需要更多对将化学知识应用于考古和文化应用感兴趣的科学家。