• 我要登录|
  • 免费注册
    |
  • 我的丁香通
    • 企业机构:
    • 成为企业机构
    • 个人用户:
    • 个人中心
  • 移动端
    移动端
丁香通 logo丁香实验_LOGO
搜实验

    大家都在搜

      大家都在搜

        0 人通过求购买到了急需的产品
        免费发布求购
        发布求购
        点赞
        收藏
        wx-share
        分享

        X-Ray Microanalysis Techniques

        互联网

        1151
        X-ray production is often the inevitable consequence of the electron irradiation of atoms, whether the atoms reside in biological or materials specimens that are either thin or infinitely thick. As long as the incident electrons are invested with sufficient kinetic energy to ionize individual atoms, X-rays will emanate from them. The technique of biological X-ray microanalysis, henceforth generically referred to as EPXMA (electron probe X-ray microanalysis), has been evolving for over 25 years, and its principles and practicalities have been described in detail on a number of occasions over that period (see [1 -5 ] for primary sources). It is a technique that detects and measures elements within structurally defined “compartments”; it cannot distinguish “bound” from “free” elemental pools; it cannot differentiate between isotopic or redox states. The spatial resolution of EPXMA is unsurpassed by any other analytical technique that combines simultaneous compositional and morphological observation. The sensitivity of EPXMA seems impressive (10-18 to 10-19 g of an element like Ca under favorable conditions), until this is converted into a concentration value for the local analyzed compartment (about 2 mmoles/kg weight, or 200 μg/g , for Ca), which is several orders of magnitude poorer than, for example, “bulk”s analytical techniques such as atomic absorption spectrophotometry and induction coupled plasma analysis. It is worth bearing these basic facts in mind before embarking on a tortuous EPXMA study, whilst also acknowledging that trace elements may not necessarily be homogeneously distributed through a biological system: they may be localized within a certain cohort of specialized cells and/or sequestered within discrete subcellular compartments. The limiting factor for EPXMA detection is local not bulk concentration.
        ad image
        提问
        扫一扫
        丁香实验小程序二维码
        实验小助手
        丁香实验公众号二维码
        扫码领资料
        反馈
        TOP
        打开小程序