Tormey J M, Platz R M
Scan Electron Microsc. 1979(2):627-34.
Frozen sections of erythrocytes have been used to validate microprobe X-ray analysis of diffusible elements in biological samples. At this meeting last year we reported that intracellular Na concentrations measured by microprobe were much higher than those measured by bulk chemical methods. It was suggested that this might be due to the movement of extracellular material over the cells by microtomy. We now present evidence that such results are better explained by electron scattering within the sample during analysis. This evidence includes observations that the excess measured Na varies directly with section thickness and inversely with accelerating voltage. At 80 kV accelerating voltage there is excellent agreement between microprobe and chemical analysis. It may be concluded that specimen preparation techniques such as used in our laboratory are satisfactory for reliably localizing diffusible elements in small volumes, but that instrumental factors can seriously affect their quantitation.
红细胞的冷冻切片已被用于验证生物样品中可扩散元素的微探针X射线分析。在去年的这次会议上，我们报告说，通过微探针测量的细胞内钠浓度远高于通过批量化学方法测量的浓度。有人认为，这可能是由于切片过程中细胞外物质在细胞上的移动所致。我们现在提供证据表明，这些结果可以通过分析过程中样品内的电子散射更好地解释。这些证据包括观察到测得的过量钠与切片厚度成正比，与加速电压成反比。在80 kV加速电压下，微探针分析和化学分析结果非常一致。可以得出结论，我们实验室使用的标本制备技术对于在小体积中可靠地定位可扩散元素是令人满意的，但仪器因素会严重影响它们的定量分析。
