Determination of critical micelar concentration of anionic surfactants using surfactants - sensible electrodes [articol]

Abstract

A series of all-solid-state electrodes sensible to the ionic (anionic and cationic) surfactants were developed using silver pills coated with PVC membranes. We used cetyltrimethylammonium laurylsulfate and tricaprylmethylammonium laurylsulfate as sensing materials (active substance). The electrochemical properties of the electrodes were studied and the functions of the electrodes were tested. We selected the best membrane composition considering the best slope and the largest linear response domain. The membrane composition with the best electrochemical characteristics was that based on tricaprylmethylammonium laurylsulfate plasticized with dioctylsebaccate (nearnerstinan slope: 58,56 mV/pC and concentration range of linear response 5x10-3-2x10-6 M of laurylsulfate). The electrode function of these electrodes presents an abrupt change at critical micellar point. This property makes possible their utilization to critical micellar concentration, an important property of surfactants solution. We compared the obtained values of critical micellear concentration for sodium laurylsulfate and dodecylbezensulphonate with those obtained from conductivity measurements and we obtained good concordance. We studied also the influence of inorganic electrolytes to critical micellar concentration (CMC) values.