Instrumentation and applications of DSC MCQs With Answer

Introduction: Differential Scanning Calorimetry (DSC) is a core thermal analysis technique for B. Pharm students, covering instrumentation, heat flow measurement, and pharmaceutical applications such as polymorphism, stability, compatibility, and purity analysis. This introduction outlines DSC principles (heat flux vs. power-compensated designs), key components (furnace, sensors, reference, sealed pans), experimental variables (heating rate, atmosphere, sample mass), and data interpretation (Tg, Tm, enthalpy, onset, peak). Understanding DSC improves formulation development, quality control, and accelerated stability testing. Familiarity with calibration, artefacts, modulated DSC, and kinetic analysis is essential for reliable results. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which fundamental quantity does DSC directly measure during a thermal scan?

• Temperature difference between sample and reference
• Heat flow into or out of the sample
• Mass loss of the sample
• Optical absorption change

Correct Answer: Heat flow into or out of the sample

Q2. Which DSC configuration uses two separate heaters and active control to maintain equal temperatures?

• Heat-flux DSC
• Power-compensated DSC
• Modulated DSC
• Thermogravimetric DSC

Correct Answer: Power-compensated DSC

Q3. In pharmaceutical DSC, which thermal event typically appears as an endothermic peak?

• Crystallization
• Glass transition
• Melting
• Exothermic curing

Correct Answer: Melting

Q4. Which parameter in a DSC thermogram defines the temperature at which a phase change begins?

• Peak temperature
• Onset temperature
• Endset temperature
• Glass transition midpoint

Correct Answer: Onset temperature

Q5. What is the common unit used to report enthalpy changes measured by DSC in pharmaceutics?

• Watt (W)
• Joule per gram (J/g)
• Kelvin (K)
• Pascal (Pa)

Correct Answer: Joule per gram (J/g)

Q6. Which sample pan type is preferred for preventing loss of volatile components during DSC?

• Open aluminum pan
• Hermetic sealed pan
• Glass crucible
• Porous ceramic cup

Correct Answer: Hermetic sealed pan

Q7. Modulated DSC (MDSC) adds a small sinusoidal modulation to the temperature to separate which two signals?

• Mass loss and heat flow
• Reversible and non-reversible heat flows
• Temperature and pressure
• Endothermic and exothermic events only

Correct Answer: Reversible and non-reversible heat flows

Q8. Which experimental factor most strongly affects peak shapes and resolution in DSC?

• Sample color
• Heating rate
• Lab humidity
• Pan lid material

Correct Answer: Heating rate

Q9. For purity determination by DSC, which principle is commonly used?

• Kirchhoff’s law
• Van’t Hoff melting point depression
• Beer–Lambert law
• Bouguer’s rule

Correct Answer: Van’t Hoff melting point depression

Q10. Which thermal event is best identified as a step change (rather than a peak) in a DSC trace?

• Melting
• Decomposition
• Glass transition (Tg)
• Crystallization peak

Correct Answer: Glass transition (Tg)

Q11. Which atmosphere is commonly used in DSC runs to prevent oxidative degradation of pharmaceutical samples?

• Air
• Nitrogen
• Oxygen
• Carbon dioxide

Correct Answer: Nitrogen

Q12. Calibration of a DSC instrument for temperature is typically done using which standards?

• Polystyrene and polyethylene
• Indium and tin (metal standards)
• Water and ethanol
• Sugar and salt crystals

Correct Answer: Indium and tin (metal standards)

Q13. Which DSC-derived parameter indicates the stability of an amorphous drug against crystallization?

• Melting enthalpy
• Glass transition temperature (Tg)
• Onset of decomposition
• Heat capacity at 0 K

Correct Answer: Glass transition temperature (Tg)

Q14. What artifact can arise in DSC if the sample mass is too large?

• Improved resolution
• Baseline noise reduction
• Peak broadening and temperature lag
• Shift to lower instrument sensitivity

Correct Answer: Peak broadening and temperature lag

Q15. Which technique is most complementary to DSC for identifying decomposition products?

• UV–Vis spectroscopy
• Thermogravimetric analysis coupled with mass spectrometry (TGA–MS)
• Polarimetry
• Gel electrophoresis

Correct Answer: Thermogravimetric analysis coupled with mass spectrometry (TGA–MS)

Q16. In DSC, recrystallization during heating of an amorphous drug appears as:

• An exothermic peak followed by an endothermic melting peak
• A single endothermic trough only
• A pure baseline shift with no peaks
• Continuous mass loss

Correct Answer: An exothermic peak followed by an endothermic melting peak

Q17. Which parameter is used to quantify crystallinity of a drug by DSC?

• Melting onset only
• Ratio of measured melting enthalpy to reference enthalpy of 100% crystalline material
• Number of peaks in the thermogram
• Glass transition width

Correct Answer: Ratio of measured melting enthalpy to reference enthalpy of 100% crystalline material

Q18. Which DSC practice reduces baseline drift and improves reproducibility?

• Use of extremely fast heating rates for all samples
• Proper instrument calibration and identical pan handling for sample and reference
• Skipping blank runs to save time
• Using samples with highly variable masses without correction

Correct Answer: Proper instrument calibration and identical pan handling for sample and reference

Q19. Which kinetic method uses DSC peak shift with heating rate to estimate activation energy of decomposition?

• Kissinger method
• Henderson–Hasselbalch method
• Arrhenius linearization of melting point
• Freundlich isotherm

Correct Answer: Kissinger method

Q20. Drug–excipient compatibility studies by DSC often look for which sign of interaction?

• Complete overlap of all peaks with pure components
• New peaks, disappearance or significant shift of melting peaks
• Only changes in color of the sample pan
• Decreased sample mass without thermal changes

Correct Answer: New peaks, disappearance or significant shift of melting peaks

Q21. Which measurement is required to calculate specific heat capacity (Cp) from DSC data?

• Sample mass and baseline-corrected heat flow change per degree
• Only the onset temperature
• Only the melting enthalpy
• Time of experiment without heat flow data

Correct Answer: Sample mass and baseline-corrected heat flow change per degree

Q22. Which statement about glass transition (Tg) determination by DSC is correct?

• Tg is observed as a sharp peak identical to melting
• Tg is a step change in heat capacity and its apparent temperature depends on heating rate
• Tg is independent of sample history and always constant
• Tg indicates decomposition temperature

Correct Answer: Tg is a step change in heat capacity and its apparent temperature depends on heating rate

Q23. When performing DSC of hydrates, which event typically appears before melting?

• Glass transition
• Dehydration (endothermic mass-loss event)
• Polymerization exotherm
• Evaporation of solvent with no thermal signal

Correct Answer: Dehydration (endothermic mass-loss event)

Q24. Which baseline correction is essential for quantitative DSC analysis?

• No baseline correction is ever needed
• Subtraction of a blank run or proper polynomial baseline fitting
• Use of an arbitrary horizontal line at zero
• Normalization by sample color

Correct Answer: Subtraction of a blank run or proper polynomial baseline fitting

Q25. Why is sample encapsulation important in DSC experiments of volatile drug substances?

• It increases the thermal conductivity of the sample
• It prevents loss of volatiles and provides controlled pressure for accurate thermal events
• It always eliminates all baseline drift
• It reduces the melting point of all materials

Correct Answer: It prevents loss of volatiles and provides controlled pressure for accurate thermal events

Q26. Which DSC observable helps distinguish between polymorphs of a drug?

• Color under microscope only
• Distinct melting points and different melting enthalpies
• Same thermal profile for all polymorphs
• Only solubility differences, not DSC

Correct Answer: Distinct melting points and different melting enthalpies

Q27. Which thermal analysis limitation should students consider when interpreting DSC for complex formulations?

• DSC directly identifies chemical structures
• Overlapping events and interactions can obscure individual transitions
• DSC always provides absolute purity values without error
• Heating rate has no effect on separation of events

Correct Answer: Overlapping events and interactions can obscure individual transitions

Q28. Which maintenance practice prolongs DSC sensor life and ensures consistent data?

• Never calibrating the instrument
• Regular cleaning of sample holder area and periodic calibration checks
• Running only room-temperature samples
• Using excessive sample mass to protect the sensor

Correct Answer: Regular cleaning of sample holder area and periodic calibration checks

Q29. Which DSC result indicates a physical mixture with no interaction between drug and excipient?

• Appearance of new exothermic peaks only
• Retention of original melting peaks of both components without significant shift
• Complete disappearance of all thermal events
• New glass transition at a single combined Tg

Correct Answer: Retention of original melting peaks of both components without significant shift

Q30. When interpreting DSC thermograms for shelf-life prediction, which combination of analyses gives the most reliable insight?

• Single DSC run at one heating rate only
• DSC coupled with kinetic analysis, TGA, and stability studies under controlled conditions
• Only visual inspection of samples after storage
• Ignoring DSC and using only HPLC

Correct Answer: DSC coupled with kinetic analysis, TGA, and stability studies under controlled conditions

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