A new approach for the selective and sensitive colorimetric detection of ionic surfactants in water
A new approach for the selective and sensitive colorimetric detection of ionic surfactants in water
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DOI：
10.1039/b910659f
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发表时间：
2010-01-01
影响因子：
--
通讯作者：
Soto, Juan
中科院分区：
文献类型：
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作者：
Coll, Carmen;Ros-Lis, Jose V.;Soto, Juan
利用带有合适结合基团的简单二氧化硅载体，建立了一种新的两步比色检测离子表面活性剂的方法。将二氧化硅与N-甲基-N‘-丙基三甲氧基硅咪唑氯化物反应合成固体S1，得到含咪唑配位基团的固体。在第一步中，固体S1与阴离子表面活性剂溶液接触，提供表面活性剂在阳离子官能化表面上的表面自组装。这一层将是非常疏水的，长的烷基链很可能指向主体溶液，在第二步中，主体溶液能够从水中提取合适的染料(亚甲基蓝)。检测原理依赖于这样一个事实，即阴离子表面活性剂的自组装过程是选择性的，这是形成的单分子层中表面活性剂分子之间独特的强疏水相互作用的结果。表明存在阴离子表面活性剂的最后行为是染料溶液的耗尽和固体的变色，这两种情况都是肉眼可见的。阳离子表面活性剂的检测也使用了类似的方法。在这种情况下，制备了含有磺酸基的固体S2。二氧化硅与3-巯基丙基三乙氧基硅烷(MPTS)反应生成S_2，再加入H_2O_2氧化生成磺酸盐。在这种情况下，阳离子表面活性剂与S2表面的相互作用导致阳离子表面活性剂在阴离子表面上自组装。在第二步中，加入合适的阴离子染料(即专利蓝)，然后发出阳离子表面活性剂存在的信号。使用标准固态技术对S1和S2固体进行表征。研究了这些固体在不同浓度的阴离子、阳离子和中性表面活性剂以及存在强制水存在的阴阳离子的情况下的响应。染料溶液的部分脱色或固体的相应变色与表面活性剂在水溶液中的浓度有关。该方法包括一种新的无有机溶剂的方法，用于阴阳离子表面活性剂的比色检测。还开发了一个模型，能够根据(I)表面活性剂在带电表面的吸附和(Ii)相应染料的进一步提取来解释固体的比色行为。
A novel two-step protocol for the colorimetric detection of ionic surfactants was developed using simple silica supports functionalised with suitable binding groups. Solid S1 was synthesised by reaction of silica with N-methyl-N'-propyltrimethoxysilylimidazolium chloride to obtain a final solid containing imidazolium coordinating moieties. In the first step, solid S1 in contact with anionic surfactant solutions provides the superficial self-assembly organization of the surfactants on the cationic functionalised surface. This layer would be remarkably hydrophobic with the long alkyl chains most likely pointing toward the bulk solution, which in the second step is able to extract a suitable dye (Methylene Blue) from water. The detection principle depends on the fact that the self-assembly process of the anionic surfactant is selective as a consequence of unique strong hydrophobic interactions between surfactant molecules in the monolayer formed. The final behaviour signalling the presence of anionic surfactants would be depletion of the dye solution and coloration of the solid, both visible to the naked eye. A similar protocol was used for the detection of cationic surfactants. In this case solid S2 was prepared containing sulfonate groups. S2 was obtained by reaction of silica with 3-mercaptopropyltriethoxysilane (MPTS) following the oxidation of the mercapto group to sulfonate by adding H2O2. In this case the interaction of cationic surfactants with the S2 surface results in the self-assembly of the cationic surfactants on the anionic surface. In the second step, the addition of a suitable anionic dye (i.e. Patent Blue) then leads to the signalling of the presence of cationic surfactants. S1 and S2 solids were characterised using standard solid-state techniques. A study of the response of these solids was carried out on different concentrations of anionic, cationic and neutral surfactants and in the presence of compulsory water-present anions and cations. The partial decolouration of the dye solution or the corresponding colouration of the solid was related to the concentration of the surfactants in the aqueous solution. The method comprises a novel organic-solvent-free approach for the colorimetric detection of anionic or cationic surfactants. A model was also developed able to interpret the colorimetric behaviour of the solids based on (i) surfactant adsorption on the charged surface and (ii) further extraction of the corresponding dye.