Marshall Alan T
Analytical Electron Microscopy Laboratory, Department of Ecology,Environment and Evolution, La Trobe University, Melbourne, Victoria, 3086, Australia.
J Microsc. 2017 Jun;266(3):231-238. doi: 10.1111/jmi.12531. Epub 2017 Feb 9.
It is shown that accurate x-ray microanalysis of frozen-hydrated and dry organic compounds, such as model biological samples, is possible with a silicon drift detector in combination with XPP (exponential model of Pouchou and Pichoir matrix correction) software using 'remote standards'. This type of analysis is also referred to as 'standardless analysis'. Analyses from selected areas or elemental images (maps) were identical. Improvements in x-ray microanalytical hardware and software, together with developments in cryotechniques, have made the quantitative analysis of cryoplaned frozen-hydrated biological samples in the scanning electron microscope a much simpler procedure. The increased effectiveness of pulse pile-up rejection renders the analysis of Na, with ultrathin window detectors, in the presence of very high concentrations of O, from ice, more accurate. The accurate analysis of Ca (2 mmol kg ) in the presence of high concentrations of K is possible. Careful sublimation of surface frost from frozen-hydrated samples resulted in a small increase in analysed elemental concentrations. A more prolonged sublimation from the same resurfaced sample and other similar samples resulted in higher element concentrations.
结果表明，使用硅漂移探测器结合XPP（Pouchou和Pichoir矩阵校正指数模型）软件并采用“远程标准”，对冷冻水合和干燥的有机化合物（如模型生物样品）进行精确的X射线微分析是可行的。这种分析类型也被称为“无标样分析”。选定区域的分析结果或元素图像（图谱）是相同的。X射线微分析硬件和软件的改进，以及低温技术的发展，使得在扫描电子显微镜中对冷冻水合生物样品进行冷冻切片后的定量分析变得更加简单。脉冲堆积排斥效率的提高使得在存在来自冰的极高浓度O的情况下，使用超薄窗口探测器对Na进行分析更加准确。在高浓度K存在的情况下，对Ca（2 mmol/kg）进行准确分析是可能的。小心地从冷冻水合样品表面升华霜会导致分析的元素浓度略有增加。对同一重新暴露表面的样品和其他类似样品进行更长时间的升华会导致元素浓度更高。
