TA

Question 1

Instrumentation basic of DSC

Answer 1

2 pans; 2 heaters; 2 sensor; a chamber to isolate from ambient environment.
Heating rate (dT/dt) is set const.
Heat flow (dQ/dt) is different.
Computer control the stoves to get the same dT/dt

Question 2

Arrhenius Equation

Answer 2

lnk = lnA - EA/(RT)
k is rate const.
A is Frequency factor or Pre-exponential factor
EA is activation energy
R is gas const. = 8.314 J/mol K
T is Kelvin temp.

Question 3

Thermal analysis study

Answer 3

Chemical reaction,
Determination of Cp, dH, Tg,...
Thermal stability,
Thermodynamic purity, polymorphism
Protein denaturation, enzymatic activity
Compatibility drug/excipient,
...

Question 4

TMDSC (Temperature modulated DSC) advantages

Answer 4

• Higher sensitivity without decreasing resolution
  + High instantaneous heating rate
  + Low underlying heating rate
• Seperation of signal in two components:
  Non-reversing (chemical reaction, crystallization)
  Reversing (Glass transition, melting)
• Quasi-isothermal Cp measurement
• Thermal conductivity measurement

Question 5

Principal of ITC

Answer 5

A macromolecule located in a measuring cell of an isothermal calorimeter is progressively saturated. at a constant Temp. by injecting amount of ligand from a syringe

Each ligand addition corresponds to the heat exchanged from the macromole-ligand interaction. The signal being proportional to the amount of complex formed.

The measured amounts of heat allow to obtain the binding isotherm, and the interaction parameters are determined using models proposed by the processing software.