双波长吸光光度法只要适当选择两个波长λ_1和λ_2,就能消除背景吸收和共存干扰组份的影响;导数吸光光度法能检出二个或二个以上的重叠吸收带,能分辨出强吸收曲线“肩部”的弱吸收带,也能消除基线(背景)的影响;荧光吸光光度法由于只能得到待测物质的一个特征吸收光谱,而且它要求特定的激发波长和给出专有的荧光波长峰位,从而减少或免除共存离子干扰的机会。总之,上述三种吸光光度法对于提高分析性能改善方法选择性十分有效。另外,这三种方弦还能提高方法准确度和灵敏度,甚至比普通的光度法要高2～3个数量级。如前所述,在普通的吸光光度法中,作为显色剂 The dual-wavelength absorption spectrophotometry can eliminate the influence of background absorption and co-existence interfering components by selecting two wavelengths λ_1 and λ_2 appropriately. Derivative absorbance spectrophotometry can detect two or more overlapping absorption bands and can distinguish strong Absorption band “shoulder ” weak absorption band, but also to eliminate the baseline (background); fluorescence spectrophotometry can only get a characteristic absorption spectrum of the material to be tested, and it requires a specific excitation wavelength and given Proprietary fluorescence wavelength peak position, thereby reducing or eliminating the chance of interference of coexisting ions. In summary, these three absorptiometric methods are very effective for improving the selectivity of the analytical performance. In addition, these three kinds of square strings can also improve the method accuracy and sensitivity, even higher than the average photometric method 2 to 3 orders of magnitude. As mentioned above, it is used as a developer in the ordinary spectrophotometry