ISO 934:1980

Overview

ISO 934:1980 defines an entrainment (azeotropic distillation) method for determining the water content of animal and vegetable fats and oils. The method is applicable to products with water content greater than or equal to 0.5% (m/m). It is intended for laboratory use where reliable, repeatable measurement of water content is required for quality control, specification testing, or regulatory compliance.

Key Topics

• Scope: Applicable to fats and oils with water content ≥ 0.5% (m/m).
• Principle: Water present in a weighed test portion is entrained by azeotropic distillation with an immiscible organic solvent; the distillate collects in a graduated receiver and the water volume is read directly.
• Reagent: Commercial xylene (isomers or mixtures) is specified as the entraining solvent.
• Apparatus:
  • Short-necked flask (minimum 500 ml capacity).
  • Reflux condenser.
  • Receiver with a graduated tube of 5 ml capacity and 0.10 ml graduations.
  • Boiling aid such as pumice-stone fragments.
• Test portion and sample preparation:
  • Prepare a representative sample per ISO 661.
  • Weigh test portions to the nearest 0.01 g; recommended test portion mass: 20 to 100 g depending on expected water content.
  • Add 100 to 300 ml of xylene to the flask (volume chosen according to test portion mass), ensuring solvent plus sample do not exceed half the flask volume.
• Procedure highlights:
  • Assemble distillation apparatus and heat until xylene boils.
  • Collect the aqueous phase in the graduated tube until the distilled solvent is clear and no more water separates.
  • If frothing occurs, 1–2 g dry oleic acid or liquid paraffin may be added; clean apparatus thoroughly between runs using distilled water then acetone and dry in an air stream.
• Calculation: Water content (%) = (V × 100) / m, where V is millilitres of water collected and m is grams of test portion (assumes water density ≈ 1 g/ml).
• Repeatability: The difference between two determinations performed by the same analyst shall not exceed 0.1 ml of water; report the arithmetic mean if repeatability is met.

Applications

• Routine quality control and acceptance testing of edible and technical fats and oils.
• Laboratory verification of moisture specifications for raw materials and finished products.
• Research and method validation where direct volumetric measurement of entrained water is suitable.

Related Standards

• ISO 661: Preparation of test sample (referenced for sampling and test-sample preparation).
• This International Standard supersedes ISO Recommendation R 934-1969 and was approved by IUPAC.

This concise summary highlights the practical procedure and requirements of ISO 934:1980 for accurate, repeatable water determination in animal and vegetable fats and oils using the entrainment method.