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——本文研究在Be~(2+)、Cu~(2+)和Al~(3+)的铬天青S(CAS)络合物可见光度法中,表面活性剂一诱导变色的机理。在阳离子表面活性剂(溴化十六烷基三甲铵、CTAB)存在下,对所有三种金属络合物,均观察到摩尔吸光系数的增加和最大吸收波长的红移。在非离子表面活性剂(TritonX-100,即TX-100)存在下,对Be~(2+)及Cu~(2+)的络合物,也观察到相同情况。在高离子强度时,发现阴离子表面活性剂(十二烷基硫酸钠,SDS)有类似的效应。在使用TX-100和SDS时,只涉及到严格意义下的胶束相互作用。而在使用CTAB时,既观察到包括表面活性剂单体在內的三元络合物的形成,也观察到了胶束相互作用,即在低浓度CTAB时,形成具有明确组成的络合物;到临界胶束浓度以上时,则为胶束相互作用。所有“表面活性剂增敏”体系的光谱都很类似,意味着生色团在三元络合物中和在胶束中有类似的微环境。
- In this paper, the mechanism of induced discoloration of surfactants in the visible spectrophotometry of Be (2 +), Cu 2+ and Al 3+ chrome azure S (CAS) complexes was studied. In all three metal complexes, an increase of the molar extinction coefficient and a red shift of the maximum absorption wavelength were observed in the presence of a cationic surfactant (cetyltrimethylammonium bromide, CTAB). The same was observed for the complexes of Be 2+ and Cu 2+ in the presence of non-ionic surfactant (Triton X-100, ie TX-100). At high ionic strength, anionic surfactants (sodium dodecyl sulfate, SDS) were found to have similar effects. When using TX-100 and SDS, only the micellar interactions in the strict sense are involved. In the case of CTAB, both the formation of ternary complexes including the surfactant monomer and the micelle interaction were observed, that is, the formation of a complex having a definite composition at a low concentration of CTAB; Above the critical micelle concentration, micellar interactions are observed. The spectrum of all “surfactant-sensitized” systems is very similar, meaning that the chromophores have similar microenvironments in the ternary complex and in the micelles.