Analysis of Demicellization Data from Isothermal Titration Calorimetry
Application Note Nov 11, 2015
Malvern Instruments Limited
To extract the CMC and the heat of demicellization of a surfactant by means of ITC, two strategies for data analysis are commonly used. Either the first derivative of the heat of demicellization with respect to surfactant concentration is calculated, or a generic sigmoidal fit is applied to the demicellization isotherm. In this paper, we outline how both approaches can be combined to provide a data-analysis strategy of superior reproducibility and without user bias, as the only user input required is the calorimetric dataset itself. Interpretation of the latter is based on a simple pseudophase separation model described in the first section of this whitepaper. In the following sections, the approach is briefly explained and illustrated with two case studies, namely, CMC determination for a nonionic alkyl maltoside detergent and a zwitterionic derivative of cholic acid.