According to AOCS CD 8b (Peroxide Value Acetic Acid-Isooctane Method); ISO (Animal and vegetable fats and oils. SAMPLING AND ANALYSIS OF COMMERCIAL FATS AND OILS AOCS Official Method Cd 8b Revised Peroxide Value Acetic. AOCS has standardized a method for. PV determination with chloroform (Cd. 8- 53) and with isooctane (Cd 8b). The latter method uses a mixture of acetic.
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The substances are generally assumed to be peroxides or other similar products of fat oxidation. This method is highly empirical, and any variation in the test procedure may result in variation of results. Replaced by Cd 8b Erlenmeyer flasks—with glass stoppers, mL. Low actinic red or amber container, about 50 mL to mL capacity. Burette—with 25 mL or 50 mL, class A, graduated in 0. Acetic acid—chloroform solution 3: Potassium iodide KI solution—saturated, prepared fresh each day analysis is performed by dissolving an excess of KI in recently boiled distilled water about Make certain the solution remains saturated during use, as indicated by the presence of undissolved KI crystals.
Store in the dark when not in use. Test the saturated KI solution by adding 2 drops of starch solution to 0. If a blue color is formed that requires more than 1 drop of 0. aocd
AOCS CD 8b – 90 Peroxido – Free Download PDF
Dissolve in 25 mL of water, add 5 mL of concentrated hydrochloric acid, 20 mL of potassium iodide solution Reagents, 2 and rotate to mix. Allow to stand for 5 min and then add mL of distilled water. Titrate with sodium thiosulfate solution, shaking continuously until yellow color has almost disappeared. Add 1—2 mL of starch indicator and 8v the titration, adding the thiosulfate solution slowly until the blue color just disappears.
The strength of the sodium thiosulfate solution is expressed in terms of its normality.
Sodium thiosulfate solution, 0. This solution may be prepared by accurately pipetting mL of 0. Starch indicator solution—tested for sensitivity, prepared by making a paste with 1 g of starch see Notes, 2 and a small amount of cold distilled water.
Add, while stirring, to mL of boiling water and boil for a few seconds. Immediately remove from heat and cool. Fresh indicator must be prepared when the end point of the titration from blue to colorless fails to be sharp.
If stored under refrigeration, the starch solution should be stable for about 2—3 weeks. Test for sensitivity—Place 5 mL of starch solution in mL of water and add 0. The deep blue color produced must be discharged by 0. Swirl to dissolve the sample. Allow the solution to stand with occasional shaking for exactly 1 min, and then immediately add 30 mL of distilled water see Notes, 3 and References, 1.
Continue the titration until the yellow iodine color has almost disappeared.
Continue the titration with constant agitation, especially near the end point, to liberate all of the iodine from the solvent layer. Add the thiosulfate solution dropwise until the blue color just disappears see Notes, 4. Conduct a blank determination of the reagents daily. The blank titration must not exceed 0. When completely melted, remove the sample from the hot plate or oven and allow to settle in a warm place until the aqueous portion and most of the milk solids have settled to the bottom.
Decant the oil into a clean beaker and filter through a Whatman no. Do not reheat for filtration unless absolutely necessary. The sample must be clear and brilliant.
Proceed as directed in Procedure for Fats and Oils, paragraphs 1—4.
AOCS CD 8b – 90 Peroxido
Fd is toxic by inhalation and has anesthetic properties. Avoid contact with the skin. Prolonged inhalation or ingestion can lead to liver and kidney damage and may be fatal. It is nonflammable, but will burn on prolonged exposure to flame or high temperature. The TLV is 10 ppm in air. A fume hood should be used at all times when using chloroform.
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Acetic acid in the pure state is moderately toxic aoxs ingestion and inhalation. It is a strong irritant to skin and tissue. The TLV in air is 10 ppm. Potassium dichromate is toxic by ingestion and inhalation. It is a strong oxidizing agent and a dangerous fire risk when in contact with organic chemicals. Isooctane has been proposed as a replacement for chloroform in this method.
The isooctane method is preferred due to the elimination of chloroform. The following are suitable starches: The test should be carried out in aoocs daylight or in artificial light shielded from aofs direct light source.
A report on a coulometric method for the measurement of peroxide value References, 2 indicates that the iodide—peroxide reaction is complete at the end of 1 min, and that the liberation of iodine is affected by light. If the titration is less than 0. Oil and Soap 9: Page 2 of 2.