Titration peroxide value

Iodine liberation is one of the oldest and most commonly used methods for assessing lipid substrate oxidation. In this method, hydroperoxides and peroxides oxidize aqueous iodide to iodine, which is then titrated with standard thiosulfate solution and starch as endpoint indicator. The peroxide value is calculated as milliequivalents of peroxide oxygen per kilogram of sample. 

This specification is for butter oil, which is butter with the water removed. The free fatty acid limit is to detect lipolytic rancidity while peroxide value specification is to limit oxidative rancidity. The copper limit arises because copper catalyses the oxidation of fats. The absence of neutralising substances is to prevent a high titration for free fatty acids being covered up by the addition of alkali. 

Oxidation indices, 656-72 peroxide determination, 762-3 peroxide value, 656, 657-64 colorimetry, 658-61 definition, 657 direct titration, 657 electrochemical methods, 663-4 IR spectrophotometry, 661-3 NIR spectrophotometry, 663 UV-visible spectrophotometry, 658-61 secondary oxidation products, 656, 665-72 tests for stability on storage, 664-5, 672 thermal analysis, 672 Oxidative amperometiy, hydroperoxide determination, 686 Oxidative cleavage alkenes, 1094-5 double bonds, 525-7 Oxidative couphng, hydrogen peroxide determination, 630, 635 Oxidative damage... 

TOCO see Thiol-olefin co-oxygenation Tocopherols, TEARS assay, 668 Torsion angles, hydroperoxides, 690 Tosylhydrazones, superoxide reactions, 1036 Total hydroperoxides see Peroxide value Total oxidative capacity, titration methods, 674 Total polar phenols, colorimetry, 664 Toxicity... 

Basic Protocol 2 Determination of Peroxide Value by lodometric Titration D2.1.4... 

The determination of peroxide value (PV) by an iodometric titration is described in Basic Protocol 2. Iodine is liberated by hydroperoxides in the oil in the presence of excess iodide in a stoichiometric ratio. The amount of iodine present is determined by titration with a standard sodium thiosulfate solution using a starch indicator, thereby reflecting how much peroxide is present in the oil or lipid extract. 

The peroxide value (PV) of an oil or fat is defined as the quantity of peroxide oxygen present in the sample. This classical iodometric method is a volumetric analysis based on the titration of iodine released from potassium iodide by peroxides in a biphasic system using a standardized thiosulfate solution as the titrant and a starch solution as the indicator (see Background Information, discussion of peroxide value). This method will detect all substances that oxidize potassium iodide under the acidic conditions of the test, therefore the purity of the reagents is critical. 

ALTERNATE PROTOCOL DETERMINATION OF PEROXIDE VALUE BY MEASUREMENT OF IRON OXIDATION The ferrous oxidation/xylenol orange (FOX) method is based on the ability of lipid peroxides to oxidize ferrous ions at low pH. The resulting oxidation is quantitated by using a dye that complexes with the generated ferric ions to produce a color that can be measured spectrophotometrically. Peroxide values (PVs) as low as 0.1 meq active oxygen/kg sample can be determined with this method, providing a distinct advantage over iodometric titration. 

Iodine, colorimetric determination of amylase using, 689-692 Iodine value, lipid composition canola oil, 474 (table) oil quality indices, 467-469, 475-477 lodometric titration, determination of peroxide value, 518-519 Ionization techniques, in mass... 

Peroxide value Peroxides liberate I2 from KI and this is titrated with sodium thiosulfate Lea453... 

Peroxide Value Accurately weigh about 10 g of sample, add 30 mL of a 3 2 mixture of glacial acetic acid chloroform, and mix. Add 1 mL of a saturated solution of potassium iodide, and mix for 1 min. Add 100 mL of water, begin titrating with 0.05 N sodium thiosulfate, adding starch TS as the endpoint is approached, and continue the titration until the blue starch color has just disappeared. Perform a blank determination (see General Provisions), and make any necessary correction. Calculate the peroxide value, as milliequiva-lents of peroxide per kilogram of sample, by the formula... 

Add 10 mL of sample to 50 mL of a 3 2 (v/v) mixture of glacial acetic acid and chloroform. Add 1 mL of a saturated solution of potassium iodide to this solution, allow to stand for exactly 1 min with gentle shaking, and then introduce 100 mL of water and a few drops of starch TS. Titrate immediately with 0.1 N sodium thiosulfate. Each milliliter of 0.1 N sodium thiosulfate, multiplied by 5, equals the peroxide value, expressed in millimoles of peroxide per liter of the sample. 

Peroxide Value Proceed as directed under Peroxide Value in the monograph for Hydroxylated Lecithin. However, after the addition of saturated potassium iodide and mixing, mix the solution for only 1 min and begin the titration immediately instead of allowing the solution to stand for 10 min. 

Allow the sample solution to stand, agitating it occasionally, for exactly 1 min, and immediately add 30 mL of water. Titrate with 0.1 A sodium thiosulfate solution, adding the solution gradually while constantly agitating until the yellow iodine color has almost disappeared. Add 0.5 mL of a 10% sodium lauryl sulfate (SDS) solution, and then add approximately 0.5 mL of Starch Indicator Solution. Continue the titration while constantly agitating, especially near the endpoint to liberate all of the iodine from the solvent layer. Add 0.1 A thiosulfate solution dropwise until the blue color just disappears. If the titration is less than 0.5 mL using 0.1 A sodium thiosulfate, repeat the determination using 0.01 A sodium thiosulfate. Conduct a blank determination, and make any necessary correction. Calculate the peroxide value by the formula... 

Peroxide value. The oxidation of oils and fats leads to the formation of hydroperoxides. The hydroperoxides readily decompose to produce aldehydes, ketones, and other volatile products, which are characteristic of oxidation rancidity. The method for determination of peroxide concentration is based on the reduction of the hydroperoxide group with HI (or KI) to liberate free iodine, which may be titrated. The... 

There are a number of analytical measures of oxidative deterioration of oils and fats. The most widely used are the peroxide value (PV) (15), which measures the hydroperoxide content by iodine titration and the anisidine value (AV) (15), which detects aldehydes by a color reaction. As an oil suffers damage because of autoxidation, the hydroperoxide content, and PV rise but do not do so indefinitely. As the hydroperoxides break down, the concentration of aldehydes and AV increase. Oxidation is better assessed by a combination of PV and AV, the Totox value... 

A measured amount of fat is dissolved in acetic acid-chloroform solvent in the presence of potassium iodide. Peroxides in the fat liberate iodine, which is titrated with 0.10 N sodium thiosulfate. A blank run is similarly treated. Peroxide value (meq peroxide oxygen/kg oil = (B — 5) x 0.10 A thiosulfate x 1000/g oU where B = titer of blank in mL and S = titer of sample in mL. 

One of the most commonly used methods for measuring rancidity is the peroxide value (POV), which is expressed in milliequivalents of oxygen per kilogram of fat or 011. This test is performed by iodometry, based on the reduction of hydroperoxide group (ROOH) with the iodide ion (I ). The concentration of the present peroxide is proportional to the amount of the released iodine (I2), which is assessed by titration against a standardized solution of sodium thiosulphate (Na2S203), using a starch indicator (Reactions 12.16 and 12.17) ... 

After removal of the flame, 50 ml of water is added at once and the mixture is titrated with a sodium thiosulphate solution, C(Na2S203) = ca. 0.05 mol/1 (for peroxide values lower than 20 a thiosulphate solution, C(Na2S203) = ca. 0.005 mol/1 should be used) using a starch solution as indicator. Simultaneously, a blank determination is carried out using all the reagents. 

This method is one of the oldest and most commonly used measurements of the extent of oxidation in oils. The standard iodometric procedures measure by titration, or colorimetric or electrometric methods, the iodine produced by potassium iodide added as a reducing agent to the oxidized sample dissolved in a chloroform-acetic acid mixture. The liberated iodine is titrated with standard sodium thiosulfate to a starch endpoint. The peroxide value (PV) is expressed as milliequivalents of iodine per kg of lipid (meq/kg), or as millimole of hydroperoxide per kg of lipid (referred to as peroxide). PV expressed as meq/ Kg = 2 X PV mmol/kg. 

Peroxide Value, The method for determination of peroxide concentration is based on the reduction of the hydroperoxide group with HI or Fe +. The result of the iodometric titration is expressed as the peroxide value. The Fe " method is more suitable for detemuning a low hydroperoxide concentration since the amount of the resultant Fe +, in the form of the ferrithiocyanate (rhodanide) complex, is determined photometrically with high sensitivity (Fe-test in Table 14.27). The peroxide concentration reveals the extent of oxidative deterioration of the fat, nevertheless, no relationship exists between the peroxide value and aroma defects, e. g. rancidity (already existing or anticipated). This is because hydroperoxide degradation into odorants is influenced by so many factors (cf. 3.7.2.1.9) which mdkc its retention by fat or oil or its further conversion into volatiles unpredictable. 

Lipid oxidation can be evaluated in a variety of ways, such as the determination of peroxide value (PV), carbonyl compounds (malondialdehyde, hexanal, etc.) diene conjugation, and oxygen consumption. Various methods may be used to quantify the lipid oxidation such as iodometric titration (IT), UV-visible spectroscopy (ferrous oxidation method, iodide oxidation method), chromatography, CL, or fluorescence (FL) methods. 

The peroxide figure is the number of ml of 0-002N thiosulphate required to titrate the liberated iodine from 1 g of oil or fat. The peroxide value at which rancidity is just perceptible is between 10 and 20. 

TLC (AOCS Ja 7-86) HPLC Titration of acetone solubles Apparent pH, 1 % in 30 70 ethanol/water viscosity, Brookfield, 80 C Gardner color peroxide value, AOCS Cd 8-53 iodine number, AOCS Cd 1-25 acid number, AOCS Ja 6-55... 

Control experiment. This is not necessary if the sodium peroxide is known to be chlorine-free. If there is any doubt on this point, the whole operation should be repeated precisely as before, but omitting the organic halogen compound. A small thiocyanate titration value may be found, and this should be deducted from all determinations in which the above quantity of the particular batch of sodium peroxide is used. 

Masking by oxidation or reduction of a metal ion to a state which does not react with EDTA is occasionally of value. For example, Fe(III) (log K- y 24.23) in acidic media may be reduced to Fe(II) (log K-yyy = 14.33) by ascorbic acid in this state iron does not interfere in the titration of some trivalent and tetravalent ions in strong acidic medium (pH 0 to 2). Similarly, Hg(II) can be reduced to the metal. In favorable conditions, Cr(III) may be oxidized by alkaline peroxide to chromate which does not complex with EDTA. 

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