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研究了新显色剂２－［２－（５－甲基苯并噻唑）偶氮］－５－二乙氨基苯甲酸（５－Ｍｅ－ＢＴＡＥＢ）的离解平衡及与Ｆｅ２＋形成配合物的条件。在十二烷基硫酸钠的存在下，５－Ｍｅ－ＢＴＡＥＢ与Ｆｅ２＋形成稳定的蓝紫色２∶１配合物，其最大吸收波长为６４０ｎｍ，表观摩尔吸光系数为１．０３×１０５Ｌ·ｍｏｌ－１·ｃｍ－１。Ｆｅ２＋的质量浓度在０～４８０μｇ／Ｌ时服从比尔定律。方法用于部级铝合金标样中微量铁的测定，结果与推荐值相符，对ｗ（Ｆｅ）为０．１％～０．５％的样品测定１０次，ＲＳＤ在０．８５％～１．９５％，用于测定矿泉水中ｗ（Ｆｅ）／１０－６铁的测定，ＲＳＤ＜１．５％（ｎ＝７），加标回收率９８．９％～９９．４％
The dissociation equilibrium of 2- (2- (5-methylbenzothiazolyl) azo] -5-diethylaminobenzoic acid (5-Me-BTAEB) and the conditions for the formation of the complex with Fe2 + were studied. In the presence of sodium dodecyl sulfate, 5-Me-BTAEB and Fe2 + form a stable blue-purple 2: 1 complex with a maximum absorption wavelength of 640 nm and an apparent molar absorptivity of 1.03 × 105 L · mol- 1 · cm-1. Beer’s law is obeyed when the concentration of Fe2 + is 0 ~ 480μg / L. The method was applied to the determination of trace iron in the ministerial grade aluminum alloy. The results were in accordance with the recommended values. The samples with w (Fe) of 0.1% ~ 0.5% were measured 10 times and the RSD was 0.85% ~ 1 .95% for the determination of w (Fe) / 10-6 iron in mineral water with a RSD <1.5% (n = 7) and a spiked recoveries of 98.9% to 99.4%