Recognition of spectrophotometry

Taking the spectrophotometric determination of manganese in carbon steel, high manganese steel and ferromanganese as an example, a new understandings of spectrophotometry are introduced under the condition of strictly follows the "precision rule", i.e.“to maintain infection consistency of each factor for each sample(including standard sample) in the same measurement series ”：(1) The absorbance of chemical matter is a domain function. "In the domain of incident light, the absorbance changeΔA is proportional to the content changeΔC of the absorbs light matter: ΔA = KΔC." We call it the “law of light absorption by chemical matter”； (2) In the domain of incident light, the content C and its absorbance A of all samples must fall on the same line ofΔA = KΔC. Therefore, the connecting line of coordinate points of the two standard samples in the upper and lower limits of the domain is the "determination line" of the sample content, and it is not necessary to draw the "calibration curves" with multiple standard samples；(3) Multi-standard the "calibration curve" is only necessary for Lambert-Beer's law；(4) The beam in the absorption band is additive, so the sensitivity of non-ｍonochromatic incident light is higher；(5) The error of spectrophotometric results depends on the degree to which the "precision rule" is followed in its implementation process. It is a function of the sample range R. The maximum error ER = 0.65R， and the measured values exceeding ( ±0.65R) are the statistical outliers that should be excluded.(6) The content range given by each method is actually the domain range of the incident light of the method. Samples with different contents can be determined by the original method as long as they are made into samples with absorbance in the domain of incident light；(7) The uncertainty of photometric determination results: ＝ 、kp=2 ， ＝ 、kp=3(n is sample capacity， is sample averag ), which are simple, clear and realistic; (8) Sample range R is the best index of the quality of the determination. The new understanding has changed the traditional concept of spectrophotometry, simplifies the operation and uncertainty evaluation of spectrophotometry, determines the maximum error of spectrophotometry, expands the content determination range of spectrophotometry to any content，and provides a new idea for the development of spectrophotometer.