光度法最大灵敏度的应用

The Application of Maximum Sensitivity in Photometry

摘要: 以锰铁中锰测定为例，介绍了应用灵敏度概念，简化高含量光度法测定的程序：1) 根据所用光度法资料，在严格遵守“重复性测量条件”下，绘制“校准曲线”探明其吸光度上限。各个含量、吸光度的坐标点都落在同一条直线上，表明两端点连线可替代“校准曲线”，其方程为几何学的“两点式”，显示光度法的原理是ΔA = kΔC而非A = kC，灵敏度Se = ΔA/ΔC；2) 称取试样一个标准样品，制备其“母液”；3) 以“微滴”方式分取其“母液”，制备吸光度临近、但不超过的最低和最高的两个样品，实施测定；4) 以最高吸光度的含量可恰当涵盖试样最高含量为前提，选取标准样品的“母液”量，并以此为准，确定吸光度最低和最高的样品含量；5) 以吸光度最低和最高两个坐标点连线，作为样品含量的“测定线”，并根据“校准曲线”方程建立样品测定的公式；6) 根据标准样品“母液”制备方法，制备被测样品的“母液”，并以“微滴”方式分取与标准样品相同的“母液”量，制备被测样品，实施测定。以“两标准样品测定法”确定其含量。该方法简便、准确、环保。同一样品8次重复测定结果，极差为0.4%，不确定度U₉₅为0.09% (k = 2)，相对标准差RSD为0.08% (n = 8)。

Abstract: Taking the determination of manganese in ferromanganese as an example, the application of the concept of sensitivity to simplify the procedure of high-content photometric determination introduced: 1) According to the photometric data used, the “calibration curve” was drawn under strict compliance with the “repeatability measurement conditions to explore its upper limit of absorbance. The coordinate points of each content and absorbance fell on the same straight line, indicating that the line connecting the two endpoints could replace the “calibration”, and its equation was the “two-point formula” in geometry, showing that the principle of photometry was ΔA = kΔC rather than A = kC, and the sensitivity Se = ΔA/ΔC; 2) Weigh a standard sample of the test sample and prepare its “mother liquor”;3) Take the “mother liquor” in the form of “microdrop” and prepare two samples with absorbance close to but not exceeding the lowest and highest , and carry out the determination; 4) Select the “mother liquor” amount of standard sample under the premise that the highest content of the sample can be properly covered, and based on this, determine the sample content with the lowest and highest absorbance; 5) Draw a straight line between the two coordinate points with the lowest and highest absorbance, which is used as the “determination line” for sample content, and establish the formula for sample determination according to the equation of the “calibration curve”; 6) Prepare the “mother liquor” of the test sample according to the preparation method of the standard sample “mother liquor”, and prepare the test sample by dispensing the same volume of “mother liquor” as the standard sample in the form of “microdrops”, and carry out the measurement. Determine its content by “two-standard sample method”. The method is simple, accurate and environmentally friendly. The results of 8 repeated determinations of the same sample had an extreme difference of 0.4%, an uncertainty U₉₅ of 0.09% (k = 2), and a relative standard deviation RSD of 0.08% (n = 8).