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在阳离子或阴阳离子混合表面活性剂存在下,以溴邻苯三酚红(BPR)作显色剂,光度法测定FeⅢ已有人研究。我们发现,非离子型表面活性剂聚乙烯醇(PVA)对FeⅢ—BPR的显色反应有强烈的增敏作用。在PH值为4的乙酸—乙酸铵缓冲液中,FeⅢ—BPR—PVA形成蓝色络合物,入max=660nm,△入=100nm,ε=4.0×10~4。FeⅢ与BPR之络合比为1:2。比之无PVA,体系络合比不变,最大吸收没有发生红移,但灵敏度提高约1倍(未加PVA时,ε=2.2×10~4)。络合物一经形成,不被EDTA破坏,极大地提高了方法的选择性。用于某些金属和合金中微量铁的测定,结果是满意的。
In the presence of cationic or cationic mixed surfactants, bromine pyrogallol red (BPR) as a chromogenic reagent, photometric determination of Fe Ⅲ has been studied. We found that the non-ionic surfactant polyvinyl alcohol (PVA) has a strong sensitizing effect on the color reaction of FeⅢ-BPR. FeⅢ-BPR-PVA forms a blue complex with pH = 4 in acetate-ammonium acetate buffer, max = 660 nm, Δin = 100 nm and ε = 4.0 × 10 -4. The complex ratio of Fe Ⅲ to BPR is 1: 2. Compared with non-PVA, the complexation ratio of the system was unchanged, and the maximum absorption did not occur redshift, but the sensitivity increased about 1 time (ε = 2.2 × 10 ~ 4 when PVA was not added). Once formed, the complex is not destroyed by EDTA, greatly increasing the selectivity of the method. For some metals and alloys in the determination of trace iron, the results are satisfactory.