Marshall A T
Scan Electron Microsc. 1980(Pt 2):395-408.
Freeze substitution can be carried out under anhydrous conditions in an acrolein-ether solvent. Embedding is done in epoxy or methacrylate resins. During this process at least some diffusible elements are virtually totally retained. Retention of elements in organ lumina and body fluid space occurs in situ. There is some evidence, as yet not unequivocal, that translocation of elements does not occur to any great extent, if at all in animal tissues. Resin embedded specimens are readily sectioned on a dry knife and good quality images are obtainable in a STEM. Sections of this type lend themselves to analysis of mass per unit volume since section thickness can be easily determined and standard are readily avilable. A method of measuring section thickness from beam current attenuation is described. Charging, drift, mass loss, contamination and beam current can all be constantly monitored by a simple method of collecting transmitted electron current. It is also possible to use transmitted electron current to determine mass thickness and to use this value as a measure of total mass in quantitative calculations. This avoids the necessity of determining the extraneous continuum contribution to background which must be done when employing peak to background ratios.
冷冻置换可在无水条件下于丙烯醛 - 醚溶剂中进行。包埋采用环氧树脂或甲基丙烯酸酯树脂。在此过程中，至少一些可扩散元素几乎能被完全保留。器官腔隙和体液空间中的元素保留是原位发生的。有一些证据（但尚不明确）表明，在动物组织中，元素的迁移即便发生也不会达到很大程度。树脂包埋的标本可用干刀轻松切片，并且在扫描透射电子显微镜（STEM）中可获得高质量图像。这类切片便于分析单位体积质量，因为切片厚度易于确定且标准品 readily avilable（原文此处有误，推测可能是“readily available”，意为“ readily 可获得”）。描述了一种通过束流衰减测量切片厚度的方法。通过一种收集透射电子电流的简单方法，可以持续监测充电、漂移、质量损失、污染和束流。还可以使用透射电子电流来确定质量厚度，并在定量计算中将该值用作总质量的度量。这避免了在采用峰背比时必须确定对背景的无关连续体贡献的必要性。
