BS EN ISO 3960:2017 pdf download

BS EN ISO 3960:2017 pdf download.Animal and vegetable fats and oils -Determinationof peroxide value —lodometric (visual) end point determination (ISO 3960:2017).
5.7 0.1 N sodium thiosulfate standard solution, c(Na2S2O1) = 0.1 maul.
Use only freshly boiled water br the preparation of this solution, possibly purged with nitrogen. This
solution can be used for one month and is stored in an amber-stained bottle.
5.8 0,01 N sodium thiosulfate standard solution, c(Na2S2O3) = 0,01 mol/l (see 9.2).
It is necessary to prepare this solution freshly from the 0,1 molfl sodium thiosulfate standard solution before use or to determine the titre daily. As experience shows, the stability is limited and depends upon the p11 value and the content of free carbon dioxide. Use only freshly boiled water for the dilution. possibly purged with nitrogen.
5.9 Starch solution, mass concentration p = 1 g/100 ml. Mix 0,5 g of starch and a small amount of cold water. Add this mixture, while stirring, to 50 ml of boiling water, boll it for a few seconds and cool immediately.
The solLition shall be freshly prepared every day.
It is recommended to use potato starch for iodometry as this starch gives a darker blue colour.
Equivalent reagents may also be used.
5.10 Potassium iodate (KlO) volumetric standard, secondary reference material, traceable to the
National Institute of Standards and Technology (NIST). Gaithersburg, Ml), USA.
5.11 Hydrochloric acid. c(HCI) = 4 mol/l.
6 Apparatus
Usual laboratory apparatus and, in particular, the following.
6.1 Erlenmeyer flask, of 250 ml capacity, with ground neck and ground glass stopper.
6.2 Burette, of 10 ml or 25 ml capacitc graduated in at leaxt 0,05 ml. preferably with automatic zero adiustment (pellet titrators).
6.3 Manual or automatic dosing unit, of 20 ml capacity, with a resolution of at least 10 il and an accuracy of ±0,15% (e.g. a piston burette).
6.4 Pipettes, of 0,5 ml, I ml, 10 ml and 100 ml capacity (or automatic pipettes).
6.5 Measuring cylinders, of 50 ml and 100 ml capadty
6.6 Analytical balance, readable to 0,000 1 g.
6.7 Magnetic stirrer, with magnetic stirring rod (of 2,5 cm) and heating plate.
6.8 Volumetric flask, of 1 000 nil capacity.
6.9 Volumetric flask, of 250 ml capacity.
6.10 Volumetric flask, of 500 ml capacity.
6.11 Microwave oven.
A microwave oven may be used to melt solid samples in an easy and quick manner. Careful and proper use of a microwave oven will not lead to any increase in the peroxide value. The suitable conditions shall be tested in advance.
7 Sampling
A representative sample should have been sent to the laboratory. It should not have been damaged or changed during transport or storage.
Sampling is not part of the method specified in this document. A recommended sampling method is given in ISO 5555.
8 Preparation of test sample
Prepare the test sample In accordance with ISO 661.
The test sample for the determination of peroxide value shall be taken first and the peroxide value shall be determined immediately.
Homogenize the sample, preferably without heating and without aeration. Avoid direct solar radiation. Heat solid samples carefully to 10 °C above their melting point. Samples with visible Impurities shall be filtered; the uiltration shall be noted in the test report.
For some products, the amount of extracted Fat/oil can be lower than 5 g. or the peroxide value of the fat/oil can be over 30 nieq of active oxygen per kilogram. In these cases, the user should choose a smaller sample mass [see Ckuc.I2 flJ.
9 Procedure
9.1 General
Carry out all steps in diffuse daylight or in artificial light. Avoid direct exposure to sunlight. Observe that all vessels are free froni oxidizing or reducing compounds.
Store the sodium thiosulfate standard solutions in amber-stained bottles.
9.2 PreparatIon and litre determination of the 0,01 N sodium thiosulfate standard solution
9.2.1 Preparation of the 0,01 N sodium thiosulfate standard solution
By means of a pipette (6.4). transfer 100 ml of the 0,1 N sodium thiosulfate standard solution (51) to a volumetric flask of 1 000 ml capacity (6.8). DiluLe to the mark with freshly boiled water (5..1). After homogenization, transfer the obtained 0,01 N sodium thiosullate standard solution to an amber. stained bottle.