Topics Map > SCS CORES > Microanalysis
Standard Operating Procedure for Differential Scanning Calorimeter
Measuring the amount of energy (heat) absorbed or released by a sample as it is heated, cooled or held at a constant (isothermal) temperature. This instrument is best used for studies at temperatures of 400°C and lower.
DSC is used for the calorimetric measurement, characterization, and analysis of thermal properties of materials. Types of thermal analysis measurement typically performed by DSC would be as follow: Melting, Crystallization, Glass Transition, Polymorphism, Purity, Specific Heat, Kinetic Study and Curing Reaction
The Diamond DSC is designed using the unique power compensation approach, which yields true heat flow measurements. Because of the very low mass (<1g) and independent furnace design of the power compensation approach, the Pyris Diamond DSC provides both the necessary very high sensitivity and unsurpassed resolution necessary for the measurement of polymorphism exhibited by pharmaceuticals.
Diamond DSC Key Features
- Very high sensitivity for the detection of weak transitions or small polymorphic forms
- Outstanding and unsurpassed resolution for better separation of polymorphic melting peaks
- The fastest heating and cooling (up to 500ºC/min) to better study kinetic or time dependent effects
- Use of platinum resistance thermometer (PRT) for the measurement of sample temperature which provides better accuracy and reproducibility than thermocouples
- Very stable baseline performance
- DSC Type: Power-compensation temperature null principle. Measures temperature and energy directly, rather than differential temperature (DT).
- DSC Cell: Independent dual furnaces constructed of platinum-iridium alloy with independent platinum resistance heaters and temperature sensors with furnace mass less than 1g.
- Temperature Sensor: Distributed, Platinum Resistance Thermometers for best linearity.
- Temperature Range: -70ºC to 730ºC
- Calorimetry Accuracy / Precision: < ± 1% / < ± 0.1%
- Scanning Rates Heating/Cooling: 0.01ºC to 500ºC/min
- Cooling Option: Intracooler 2P, -70ºC to 730ºC
The differential scanning calorimeter can analyze solid or liquid samples. Solid samples can be in film, powder, crystal, or granular form. Although quantities accuracy will remain the same regardless of sample shape, the qualitative appearance of run may be affected by the sample configuration. Proper sample preparation that maximizes the contact surface between the pan and the sample will reduce the resistance of the sample to heat flow though the DSC temperature sensors and will result in maximum peak sharpness and resolution. The best sample shapes for optimum performance are thin desks or film or fine granules spread in thin layer on the bottom of the pan. Materials such as polymer films can be conveniently prepared by cutting out sections of the film with a standard paper punch or cork borer. Solid materials can be sliced with a razor or knife.
1. Open N2 valve (20 psi)
2. Turn on the chiller
Log on the computer (These three items should be done on sequence and they are also arranged in sequence).
4. Start on Pyris Manager Program
A. Click Diamond DSC
B. Clear sample stage, both reference and sample
C. Let the rid open and start clean furnace function
D. Click cover heater and Deck hand buttons after cleaning
5. Sample preparation
A. Use solid (round) or liquid (narrow) pan
B. Place a cover on it
C. Press down using the Sealer Pan Crimper.
6. Sample placement
Place the sample pan on the left holder. ( Sample weight should be 0.5 and 100 mg). A nominal weight of 5 mg (about 5 microliters) is a good amount of sample for analysis.
A. Place an empty pan on the right holder
B. Make sure tooth hole cover is placed on the right position
C. Turn the sample holder counterclockwise to close
7. Programming your DSC run
1. Program your run using the method editor.
2. (Step 1) Selecting the Sample Info tab, enter Sample ID, Operator ID, Comments, and sample weight. Using the Browse button, determine the directory you wish to save your DSC run information in, and the filename.
3. (Step 2) Selecting the Initial State tab, enter the necessary information as shown below.
4. Initial temperature : temperature where your run will start. Usually 25 degC
5. Y Initial : reference value of heat flow. Usually 0.
6. Purge gas : Set as Helium @ 20 ml/min if available
7. Equilibrate temperature : Usually 0.01 degC
8. Equilibrate heat flow : Usually 0.01 mW
9. Equilibrate wait time : Usually 15 minutes
10. (Step 3) Selecting the Program tab, enter the steps your run will consist of. Your run will start with an initial isothermal condition. Decide how long it will be isothermal in minute durations.
11. (Step 4) Press Add a step to include additional steps. Choose either Temperature Scan for changing the temperature or Isothermal for maintaining a temperature.
12. (Step 5) If you choose a Temperature Scan step, input the target end temperature and the cooling/heating rate.
13. (Step 6) Select the End Condition button to set how the system should behave after the run is completed. The DSC temperature usually should return to its load temperature. You can choose to turn OFF the Cryofill and Cover heater if you plan to be absent for a long time or if it’s your last run for the day and you won’t be able to shut off the system when the run is completed. You should NOT opt to turn OFF the Cryofill if you plan to do another run. Turning OFF the cryofill will make an equilibration period necessary when you re-enable the cryofill.
14. Experiment setup
a. Write sample ID and operator name
b. Leave weight 0 mg (put real value when it is necessary)
c. Set initial state with temperature
d. Set program with operating temperatures and heating rates
e. Do baseline subtract without sample pan if necessary
g. Export file as ASKII format
h. Switch operation windows using window tab
a. Go to Pyris program and close all
b. Remove sample
c. Turn off the instrument power and chiller
d. Close N2 valve
e. Log off
A typical DSC plot looks like this.