Manual Direct Two-Phase Titration Method for Anionic Surface Active Agents Determination with Use of Solvatochromic Dye. The Modification Towards Toxicity Abatement

摘要

The modification of the manual direct two-phase titration method for anionic surface active agent determination is presented. The purpose was to find such organic solvent which can replace solvents applied in the method i.e. chloroform or dichloromethane since both are harmful, exhibiting carcinogenic, mutagenic and, embryotoxic properties. As a new solvent 1-butanol or isobutyl alcohol was used. The reaction in the examined alcohols caused to be acidic during the titration process. Thus the solvatochromic dye (1) i.e. 5-(3-bromo-4-hydroxy-5-methoxyphenyl)-7,7-dimethyl-7H-indolo[1,2-a]quinolinium perchlorate has been replaced with 1-phenyl-2-[2-(3-nitro-4-hydroxy-5-methoxyphenyl)ethenyl]-3,3-di-methyl-3H-indolium perchlorate (2). The pK_a (3.51) of (2) facilitates its dissociation, and has the same color change at the titration end-point. The modified method was tested on three different concentrations of sodium dodecyl sulfate solution, and the results are in good agreement with the real ones.