LimsPulse
Thermal analysis & ovens

Melting Point Apparatus

Heats a sample packed in a thin glass capillary at a slow, controlled rate and records the temperatures at which it starts and finishes melting. Used for identity and purity checks of APIs and excipients.

  • Pharmaceutical
  • Fine chemicals
  • Agrochemicals
  • Dyes and pigments
  • Academic labs
Photo of a Melting Point Apparatus
Photo: Iain George, CC BY-SA 2.0 (cropped), via Wikimedia Commons
Follow your site SOP
This is a typical operating sequence for learning. Your instrument model and approved SOP take precedence.
STAGE 1

Before you start

  1. 1Check the instrument is within its calibration due date.
  2. 2Dry the sample as stated in the monograph (for example in a desiccator) unless the method says otherwise.
  3. 3Grind the sample to a fine powder on a clean, dry watch glass.
  • Use only clean, dry capillaries of the specified size. Damp or dirty capillaries change the result.
STAGE 2

Filling the capillary

  1. 1Press the open end of the capillary into the powder.
  2. 2Tap the closed end on the bench, or drop the capillary down a long glass tube, to pack the powder tightly.
  3. 3Repeat until the packed column is about 3 mm high (as your method specifies).
  • Loose or very tall columns give wide, high melting ranges.
STAGE 3

Measurement

  1. 1Set the start temperature a few degrees below the expected melting point (for example 5–10 °C below) and wait for it to stabilise.
  2. 2Set the ramp rate as required (typically 1 °C/min) and the stop temperature.
  3. 3Insert the capillary and start the ramp.
  4. 4Record the temperature at which the column collapses or first liquid appears, and the temperature at which the sample is completely clear.
  5. 5Run at least two capillaries and report the range.
  • Never reuse a melted capillary.
  • If the melting point is unknown, do a quick fast-ramp run first to find it, then repeat at the correct rate with fresh capillaries.
STAGE 4

After use

  1. 1Let the block cool and remove used capillaries into a sharps container.
  2. 2Clean the block holes and viewing window of any spilled powder.
  3. 3Complete the instrument usage log.
In LimsPulse · Calibration Management

Keep every Melting point apparatus in control: usage logs, calibration and maintenance schedules, and automatic blocking of overdue instruments.

See how