LimsPulse
Food & proximate analysis

Soxhlet / fat extraction system

Extracts fat from a dried, ground food sample with a repeatedly recycled organic solvent. The solvent is then evaporated and the fat left behind is weighed.

  • Food & beverage
  • Animal feed
  • Oilseeds and edible oils
  • Agriculture
  • Academic research
Photo of a Soxhlet / fat extraction system
Photo: Vivi! (French Wikipedia), CC BY-SA 2.5 (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. 1Dry the extraction flasks or cups with a few boiling chips at about 100–105 °C, cool in a desiccator and weigh.
  2. 2Check the cooling water flow and the condenser seals.
  3. 3Check the solvent is the grade the method requires and is free of residue (evaporate a portion and check).
  4. 4Confirm the unit is in a fume hood or ventilated area with no ignition sources nearby.
  • Diethyl ether forms explosive peroxides on storage. Test old ether or use petroleum ether as the method allows.
STAGE 2

Extraction

  1. 1Weigh the dried, ground sample into the thimble and cover it with fat-free cotton wool.
  2. 2Place the thimble in the extractor and add the solvent volume set in the method.
  3. 3Switch on heating and adjust it to give the condensation or siphon rate in the method.
  4. 4Extract for the full time (for example several hours in classic glassware, or the boiling and rinsing times on an automated unit).
  5. 5Run a reagent blank (empty thimble) and a reference material in each batch.
  • Never leave a classic Soxhlet running unattended without a cooling water flow alarm.
  • Keep the heating rate moderate; violent boiling causes solvent loss and bumping.
STAGE 3

Solvent recovery and weighing

  1. 1Recover the solvent by distillation into the recovery tank or a separate flask.
  2. 2Dry the flask in an oven (commonly about 100–105 °C for 30–60 min) to remove the last solvent.
  3. 3Cool in a desiccator and weigh. Repeat drying until constant mass.
  4. 4Calculate fat % and record all weights.
  • Do not put flasks with visible solvent into the oven. Evaporate solvent in the fume hood first.
STAGE 4

Shutdown

  1. 1Switch off heating and let the unit cool before stopping cooling water.
  2. 2Empty and label recovered solvent.
  3. 3Clean the extraction chambers and inspect glassware for cracks.
  4. 4Complete the instrument log.
In LimsPulse · Calibration Management

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

See how