• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >Understanding the Mechanisms Enabling an Ultra-high Efficiency Moving Wire Interface for Real-time Carbon 14 Accelerator Mass Spectrometry Quantitation of Samples Suspended in Solvent.
【24h】

Understanding the Mechanisms Enabling an Ultra-high Efficiency Moving Wire Interface for Real-time Carbon 14 Accelerator Mass Spectrometry Quantitation of Samples Suspended in Solvent.

机译：了解实现超高效率动线接口的机制，以实现实时碳14加速器质谱定量分析溶剂中悬浮的样品。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Carbon 14 (14C) quantitation by accelerator mass spectrometry (AMS) is a powerfully sensitive and uniquely quantitative tool for tracking labeled carbonaceous molecules in biological systems. This is due to 14C's low natural abundance of 1 ppt, the nominal difference in biological activity between an unlabeled and a 14C-labeled molecule, and the ability of AMS to measure isotopic ratios independently of a sample's other characteristics. To make AMS more broadly accessible, a moving wire interface for real-time coupling of high pressure liquid chromatography (HPLC) to AMS and high throughput AMS quantitation of minute single samples has been developed. Prior to this work, samples needed to be converted to solid carbon before measurement. This conversion process has many steps and requires that the sample size be large enough to allow precise handling of the resulting graphite. These factors make the process susceptible to error and time consuming, as well as requiring 0.5 ug of carbon. Samples which do not contain enough carbon, such as HPLC fractions, must be bulked up. This adds background and increases effort. The moving wire interface overcomes these limitations by automating sample processing. Samples placed on the wire are transported through a solvent removal stage followed by a combustion stage after which the combustion products are directed to a gas accepting ion source. The ion source converts the carbon from the CO2 combustion product into C ions, from which an isotopic ratio can be determined by AMS. Although moving wire interfaces have been implemented for various tasks since 1964, the efficiency of these systems at transferring fluid from an HPLC to the wire was only 3%, the efficiency of transferring combustion products from the combustion oven to ion source was only 30%, the flow and composition of the carrier gas from the combustion oven to the ion source needed to be optimized for coupling to an AMS gas accepting ion source and the drying ovens were not designed to contain volatile samples. In addressing these issues we were able to use a moving wire interface to reduce minimal 14C-AMS sample sizes from 0.5ug to 10's of ng, reduce measurement times from days to minutes, measure 8 HPLC traces in a day instead of 1 HPLC trace in 3 days, measure HPLC traces with temporal resolution of seconds instead of that limited by fraction size, and detect 14C in HPLC traces with greater sensitivity.;This work covers the understanding of how the mechanisms that enable these improvements function. This includes a model of how altering the texture of the wire may be used to control fluid applied to the wire; a novel approach to applying a continuous flow of fluid to the wire in either droplets or a coherent jet and the necessary understanding of fluid dynamics to design a system to produce droplets of the desired size or jet of the desired flow rate; a description of the wire's vibration and the means to mitigate it; the details of an improved drying oven that removes solvent more quickly and captures volatilized material; a method of predicting sample volatility within the drying oven, based on readily available partial pressure vs. temperature data; and a method of modeling the combustion oven flow network and fluid velocities, to aid in the construction of a combustion oven that directs 100% of combustion products to the instrument.;The work was performed at the Research Resource for Biomedical AMS, which is operated at LLNL under the auspices of the U.S. Department of Energy under contract DEAC52-07NA27344. The Research Resource is supported by the National Institutes of Health, National Institute of General Medical Sciences under Grant P41 GM103483.
机译：通过加速器质谱（AMS）进行的碳14（14C）定量是一种功能强大且灵敏的独特定量工具，可用于跟踪生物系统中标记的碳质分子。这是由于14C的自然丰度低至1 ppt，未标记分子与14C标记分子之间的生物学活性的标称差异以及AMS能够独立于样品的其他特征来测量同位素比的能力。为了使AMS的使用范围更广，已经开发了一种用于实时连接高压液相色谱（HPLC）和AMS以及高通量AMS定量分析单个样品的活动金属丝接口。在进行这项工作之前，需要在测量之前将样品转换为固体碳。该转换过程有许多步骤，并且要求样本量足够大以允许精确处理生成的石墨。这些因素使该过程易于出错和耗时，并且需要0.5 ug的碳。含碳量不足的样品（例如HPLC馏分）必须堆积。这增加了背景并增加了工作量。动线接口通过自动化样品处理克服了这些限制。放置在金属丝上的样品先经过溶剂去除阶段，再经过燃烧阶段，然后将燃烧产物导向气体接受离子源。离子源将来自CO2燃烧产物的碳转化为C离子，可以通过AMS确定其同位素比。尽管自1964年以来就已经实现了用于各种任务的移动金属丝接口，但是这些系统将液体从HPLC传输到金属丝的效率仅为3％，而将燃烧产物从燃烧炉传输到离子源的效率仅为30％，需要优化从燃烧炉到离子源的载气的流量和组成，以耦合到AMS接受离子源的气体，并且干燥炉未设计为包含挥发性样品。在解决这些问题时，我们能够使用移动线接口将最小的14C-AMS样品大小从0.5ug减少到10s ng，将测量时间从几天缩短至几分钟，每天测量8条HPLC痕迹，而不是1条HPLC痕迹3天后，以秒为单位的时间分辨率测量HPLC痕迹，而不受馏分大小的限制，并以更高的灵敏度检测HPLC痕迹中的14C。该工作涵盖了对实现这些改进的机制如何起作用的理解。这包括一个模型，该模型说明如何使用改变金属丝的质地来控制施加到金属丝上的流体。一种新颖的方法，以液滴或相干射流的形式将连续的流体流施加到金属丝上，并且对流体动力学有必要的了解，以设计一种系统，以产生所需大小的液滴或所需流速的射流；电线振动的描述以及减轻振动的方法；改进的干燥箱的细节，该干燥箱可以更快地除去溶剂并捕获挥发的物料；一种基于容易获得的分压与温度数据预测干燥箱内样品挥发性的方法；以及对燃烧炉流动网络和流体速度进行建模的方法，以帮助构建将100％燃烧产物引导至仪器的燃烧炉。该工作是在生物医学AMS研究资源处进行的在美国能源部主持下的LLNL，合同号为DEAC52-07NA27344。该研究资源由美国国立卫生研究院，美国国立普通医学科学院根据Grant P41 GM103483提供支持。

著录项

  • 作者

    Thomas, Avraham Thaler.;

  • 作者单位

    University of California, Davis.;

  • 授予单位 University of California, Davis.;
  • 学科 Physics General.;Chemistry Analytical.;Engineering General.
  • 学位 Ph.D.
  • 年度 2013
  • 页码 108 p.
  • 总页数 108
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号