BS EN 14112 Fat and oil derivatives - Fatty Acid Methyl Esters (FAME) - Determination of oxidation stability (accelerated oxidation test)
4 Reagents and materials
Use only reagents of recognised analytical grade, and distilled or demineralized water.
4.1 Molecular sieve, with moisture indicator, pore size 0.3 mm. The molecular sieve should be dried in an oven set at 150 °C and cooled down to room temperature in a desiccator.
4.2 Acetone.
4.3 Alkaline laboratory glass cleaning solution.
4.4 Glycerol.
5 Apparatus
Usual laboratory equipment and, in particular, the following.
5.1 Appliance for the determination of oxidation stability
See Figures 1 and 2 for diagrammatic representations.
NOTE An appliance for determining oxidation stability can be obtained commercially.
5.1.1 Air filter, comprising a tube fitted with filter paper at the ends and filled with a molecular sieve (4.1), connected to the suction end of a pump.
5.1.2 Gas diaphragm pump, with an adjustable flow rate of 10 l/h in combination with an apparatus to control the flow rate manually or automatically with a maximum deviation of +/- 1.0 l/h from the set value.
5.1.3 Reaction vessels of borosilicate glass, connected to a sealing cap.
The sealing cap shall be fitted with a gas inlet and outlet tube. The cylindrical part of the vessel shall preferably be narrower a few centimetres below the top in order to break any emerging foam. An artificial foam blocker (e.g. glass ring) may also be used for this purpose.
5.1.4 Closed measurement cells, of approximately 150 ml capacity, with a gas inlet tube extending to the bottom inside of the vessel. The cell shall be provided at the top with ventilation holes.
5.1.5 Electrodes, for measuring conductivity with a measuring range of 0 µS/cm to 300 µS/cm aligned with the dimensions of the measurement cell (5.1.4).
5.1.6 Measuring and recording apparatus, comprising:
a) an amplifier;
b) a recorder for registering the measuring signal of each of the electrodes (5.1.5).
5.1.7 Thyristor and contact thermometer graduated in 0.1 °C or Pt 100 element to measure the block temperature, with attachments for relay connection and an adjustable heating element; temperature scale 0 °C to 150 °C.
5.1.8 Heating block, made of cast aluminium, adjustable to a temperature up to (150 +/- 0.1) °C. The block shall be provided with holes for the reaction vessels (5.1.3), and an aperture for the contact thermometer (5.1.7). Alternatively, a heating bath may be used, filled with oil suitable for temperatures up to 150 °C and adjustable to the nearest 0.1 °C.
5.2 Certified and calibrated Thermometer or Pt 100 element, with a temperature range up to 150 °C, graduated in 0.1 °C.
5.3 Measuring pipettes (two), of capacity 50 ml and 5 ml.
5.4 Oven, capable of being maintained up to (150 +/- 3) °C.
5.5 Connecting hoses, flexible and made of inert material [polytetrafluoroethylene (PTFE) or silicone].
