Automated analysis of calorimetric demicellization titrations

Determination of the critical micellar concentration of surfactants and of the heat of demicellization by means of isothermal titration calorimetry usually involves either calculation of the first derivative of the heat of demicellization with respect to surfactant concentration or application of a generic sigmoidal fit to the demicellization isotherm. Here, we show that a combination of both approaches provides an unbiased and reproducible data analysis strategy without the need for user input other than the calorimetric data proper. The approach is explained and exemplified using demicellization isotherms of the fluorinated surfactant F6OPC (3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-n-octylphosphocholine) and the zwitterionic detergent CHAPSO (3-([3-cholamidopropyl]dimethylammonio)-2-hydroxy-1-propanesulfonate).