DSC · Calibration procedure
Temperature and enthalpy calibration (indium)
Melts a certified indium standard and checks the onset temperature and heat of fusion against the certified values (onset 156.6 °C, ΔH about 28.45 J/g).
PURPOSE
Why this is checked
DSC temperature and peak area depend on the sensor calibration. Indium melts sharply at a known temperature with a known enthalpy, so it checks both the temperature axis and the heat-flow (cell constant) in one run.
Frequency
Typically a check each week or each month of use and a full calibration every 6–12 months, or after repair, as defined in your SOP.
Learn how the DSC worksYOU WILL NEED
Standards & tools
- Certified indium reference material (onset about 156.6 °C, enthalpy of fusion about 28.45 J/g; use the certificate values)
- Optional second standard for wider ranges, for example zinc (melting about 419.5 °C) or tin
- Calibrated microbalance
BEFORE YOU START
Prerequisites
- Purge gas and flow as in routine methods (for example nitrogen 50 mL/min)
- Same pan type and heating rate as routine use (for example 10 °C/min)
- Clean cell and a flat baseline
PROCEDURE
Step by step
- 1Weigh about 5–10 mg of indium accurately into an aluminium pan and crimp the lid.
- 2Place it in the cell with an empty reference pan.
- 3Heat from about 120 °C to 180 °C at the routine heating rate.
- 4Evaluate the extrapolated onset temperature and the peak area (J/g) with a linear baseline.
- 5If adjustment is needed, enter the measured values in the calibration software, then rerun to confirm.
RECORD
Example observation table
| Parameter | Certified value | Observed | Difference |
|---|---|---|---|
| Onset temperature (°C) | 156.6 | 156.8 | +0.2 °C |
| Enthalpy of fusion (J/g) | 28.45 | 28.21 | −0.84% |
CALCULATION
How to calculate the result
ΔT = Observed onset − Certified onset; % error ΔH = (Observed ΔH − Certified ΔH) ÷ Certified ΔH × 100; Cell constant K = Certified ΔH ÷ Observed ΔH
- ΔT = 156.8 − 156.6 = +0.2 °C
- % error ΔH = (28.21 − 28.45) ÷ 28.45 × 100 = −0.84%
- K = 28.45 ÷ 28.21 = 1.0085
ACCEPTANCE CRITERIA
Pass if
- Onset within about ±0.5 °C of the certified value (typical; check your SOP).
- Enthalpy within about ±2% of the certified value (some SOPs use ±1%).
IF IT FAILS
What to do
- Check the pan sits flat, the purge gas is correct and the indium is clean.
- Recalibrate the temperature and cell constant using the manufacturer's procedure and rerun indium.
- Assess the impact on results generated since the last passing calibration.
- Repeat the full calibration before returning it to use.
In LimsPulse · Calibration Management
LimsPulse schedules this calibration, records the result against limits, and blocks the instrument everywhere if it fails or goes overdue.