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Peroxide Value Test Procedure

In this peroxide value test procedure post we briefly summarise about: principle, reagents requirements, procedure, result, application and limitations of peroxide value test.

The peroxide value test is a parameter that specifies the amount of oxygen in a substance as peroxide, particularly hydroperoxides. The peroxide value indicates how much oxidation is there. Peroxide values test for animal oils and fats, vegetable oils and fats, and flavour and fragrance compounds are determined using peroxide value test.

Principle

The material is treated in solution with acetic acid and a suitable organic solvent before being exposed to a potassium iodide solution. A standard solution of sodium thiosulfate is used to titrate the released iodine. Peroxide concentrations are measured in milliequivalents of peroxide per kilogramme or millimoles of peroxide per litre in peroxide value test.

Requirements

Materials

1. Balance

2. Burette Iodine flask

3. Erlenmeyer flask

Chemicals

1. Potassium Iodide: Saturated solution of potassium iodide in deionised water, freshly prepared. The solution must remain saturated (undissolved crystals must be present). The solution has to be kept protected from light.

2. Starch Solution 1 %: Soluble starch, 10 g is dissolved in deionised water, 1000 mL with heating. Formic acid, 3 mL is added to stabilize the solution.

3. Sodium thiosulfate: N/500 Sodium Thiosulphate Solution, Prepare N/10 solution and dilute to N/500 on the day of use for peroxide value test.

4. Solvent Mixture: Mixture might be prepared by measuring volume of glacial acetic acid and organic solvent in separated volumetric flasks prior to be blended.

Procedure

1. Add 1g of powdered potassium iodide and 20mL of solvent mixture to 1g of oil or fat in a clean dry boiling tube.

2. Place the tube in boiling water for 30 seconds or until the liquid boils vigorously, but not for more than 30 seconds.

3. Transfer the contents to a conical flask containing 20mL of 5% potassium iodide solution as soon as possible.

4. Collect into the conical flask after washing the tube twice with 25mL water each time. Titrate with sodium thiosulphate solution N/500 until the yellow hue is practically gone.

5. Add 0.5 mL starch, shake briskly, and titrate slowly until the blue hue fades completely. At the same time, a blank should be set.

Calculation

where,
S = mL Na2S2O3 (Test-Blank) and
N = normality of Na2S2O3

We hope peroxide value test post helps you understand principle, reagents requirements, procedure, result, application and limitations of peroxide value test.

Further Readings

Reference