Metody wyznaczania krytycznego stężenia micelarnego związków powierzchniowo czynnych

Surface active agents, also known as surfactants, are a group of chemical compounds that are used in various products of the chemical industry. These compounds are components of medicines, detergents, motor oils and many others. The multitude of uses of surfactants makes it important to know their aggregation behaviour in solution. There are many methods used to analyse surfactants behaviour in liquid phase. The choice of a particular technique usually depends on the chemical structure of the surfactant. An example of a method that is used in studies of ionic surfactants is conductometry. This technique allows to study the dependence of specific conductivity on surfactant concentration, enabling determination of critical micellar concentration (CMC). Capillary electrophoresis is another example of the method used to determine the critical micellar concentration. It allows to make measurements in conditions where other methods fail, including conductometric method. Surfactant solutions differ in viscosity, which changes with the appearance of micelles in solution. Measurement of marker compound migration time through surfactant solutions of various concentrations allow to determine critical micellar concentration. Isothermal titration calorimetry (ITC) allows to study the thermal effects associated with the aggregation of surfactants into micelles. Based on the energy changes that occur during titration, the critical micellar concentration of surfactant can be precisely determined. ITC is very sensitive method, so basically it can be used to examine all types of surfactants. In addition, the ITC method allows to determine the thermodynamic parameters of the undergoing micellization process. The use of several measuring methods gives a more complete picture of the phenomena occurring in solutions. It allows to understand aggregation process more accurately. Therefore, CMC measurement are often made with the use of several complementary methods.