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钒(Ⅳ):MTB=1:2的红色络合物比1:1的蓝色络合物稳定,络合物形成后不被EDTA分解,且EDTA的用量对吸光度无影响。但当EDTA在显色剂前加入时,则络合物不能形成。故当在相同条件下制备参比液时,可抵消EDTA与其它金属离子络合物的影响,使方法的选择性大有提高。本文在pH5.0显色,络合物5分钟内能显色完全,并且至少稳定8小时。EDTA存在时也能稳定50分钟。钒在0.02～2.2微克/毫升范围服从比尔定律,摩尔吸光系数ελ_(max530nm)=
Vanadium (Ⅳ): The red complex with MTB = 1: 2 is more stable than the blue complex with 1: 1. The complexes are not decomposed by EDTA after forming, and the amount of EDTA has no effect on the absorbance. However, when EDTA is added before the developer, the complex can not be formed. Therefore, when the reference solution is prepared under the same conditions, the influence of EDTA and other metal ion complexes can be counteracted, and the selectivity of the method is greatly improved. Color developed at pH 5.0. The complex developed completely within 5 minutes and was stable for at least 8 hours. EDTA also stabilizes for 50 minutes in the presence of EDTA. Beer’s law is obeyed in the range of 0.02-2.2 μg / ml for vanadium. The molar absorptivity ελ_ (max530nm) =