Calculation of MTDSC signals, factors effecting the signals and applications in drug development

Abstract

In this paper the author emphasizes on the basic principle of Modulated Temperature Differential Scanning Calorimetry (MTDSC), advantages of MTDSC compared to conventional DSC, calculation of heat flow components and heat capacity components, factors effecting the MTDSC signals and application of MTDSC in drug development. MTDSC a sinusoidal modulation is overlaid on a conventional linear heating ramp, in which the sample temperature increases continuously with time. The linear heating rate gives the information same as the standard DSC, while the sinusoidal heating rate determines the fraction of the total heat flow corresponding to the changing heat rate. The total heat flow rate depends on heat capacity and change in heat capacity. This fraction of heat flow is called Reversing heat flow or the heat capacity component of the Total heat flow. The kinetic component is time dependent, also known as Non-reversing heat flow that does not respond to the changing heating rate. For accurate measurements of heat flow components and heat capacity components optimized experimental parameters must be chosen. MTDSC in particularly plays an preformulation studies to establish Tg, polymorphic forms, polymorphic transitions, ensure stability by drug excipient compatability studies and to determine enthalpy of polymorphic transitions.