A source of systematic errors in the determination of critical micelle concentration and micellization enthalpy by graphical methods in isothermal titration calorimetry

Mónica Corea, Rogelio Jiménez-Juárez, Gabriela Martínez-Mejía, María de Jesús Martínez-Ortiz, José Manuel Del Río

Resultado de la investigación: Contribución a una revistaArtículorevisión exhaustiva

1 Cita (Scopus)

Resumen

Isothermal titration calorimetry is frequently employed to determine the critical micelle concentration and the micellization enthalpy of surfactants in terms of geometrical characteristics of the titration curves. Previously we have shown theoretically that even for an infinitesimal injec-tion, the heat per titrant mol depends on the stock solution concentration. In this work, we explore experimentally the influence of the stock solution concentration on the geometrical characteristics of the titration curve and its effect in determining the critical micelle concentration and the micel-lization enthalpy of surfactants. The systematic study of this phenomenology involves a great number of measurements at different temperatures with several repetitions carried out using a robotic calorimeter. As surfactant hexadecyltrimethylamonium bromide was used. The magnitude and shape of the heat titration depend on the stock solution concentration. As a consequence, the inflexion-point, break-point, and step-height decrease until a limiting value. A qualitative analysis suggests that the limiting value depends only on substance. This work shows that graphical methods could not be suitable for the calculation of the critical micelle concentration and micelli-zation enthalpy because the magnitude and shape of the titration curve depend on the stock solution concentration. Micellar properties should be calculated by the application of theoretical mod-els as in the ligand-binding studies.

Idioma originalInglés
Número de artículo236
Páginas (desde-hasta)1-23
Número de páginas23
PublicaciónEntropy
Volumen23
N.º2
DOI
EstadoPublicada - feb 2021

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