Peroxide value of Oleic acid
Fat and Oil
Redox titration by
Automatic Potentiometric Titrator
Standard
Test Method for Analysis of Basic
Fatty Material
ISO
3960
1. Abstract
The oleic acid is widely distributed in plant and animal fats. Measurement of
peroxide value (POV) of oleic acid is demonstrated in this application according to the
below quoted test method. The test sample is first dissolved in mixture of chloroform
and acetic acid（2：3）. By flowing nitrogen gas through the sample to dispel residual
oxygen, add potassium iodide, and then titrate free iodine with 0.01mol/L sodium
thiosulfate.
The endpoint is determined by the maximum inflexion point on titration curve.
POV is calculated from titration volume of sodium thiosulfate.
I2 + 2Na2S2O3
→
Na2S4O6 + 2NaI
2. Reference
1) Test Method for Analysis of Basic Fatty Material by Japanese Oil Chemistry
Society; Reference material 2.4-1996 Peroxide value （Chloroform Method）
2) ISO 3960 : 2007 Animal and vegetable fats and oils – Determination of peroxide
value
3. Cautions in measurement
1) Do not use water containing carbon dioxide in preparing saturated potassium
iodide solution.
2) To confirm saturation, add excessive potassium iodide to the saturated
potassium iodide solution, and leave crystal in the solution.
3) Prepare fresh saturated potassium iodide each time.
4) If the sample does not change color to yellow due to free iodine when saturated
potassium iodide is added, add more saturated potassium iodide except when
blank test is performed or if peroxide value is very small in number.
5) Before potassium iodide is added, flow nitrogen gas through the sample to dispel
residual oxygen.
6) If potential change around EP is small, adjust Gain of Control parameter.
TIB-99309 Ver.01 1/4
4. Post-measurement care
Rinse the electrode with pure water, and keep it dipped in water to avoid drying up.
5. Test equipment
Main unit ：Automatic potentiometric titrator （Standard preamplifier: STD－）
Electrode ：
Option Combination Pt. electrode
6. Reagent
Reagent ：
Solvent ：
Additive ：
Inactive gas
0.01mol/L Sodium thiosulfate （ｆ＝1.006）
Mixture of chloroform and acetic acid (2：3)
Saturated potassium iodide
：Nitrogen gas
7. Measurement procedure
―measurement―
1) Deliver approx. 5g sample into a conical flask with stopper.
2) Add 30mL solvent and gently shake to dissolve the sample completely.
3) Gently replace the air inside flask with nitrogen to remove remaining oxygen.
4) By further flowing nitrogen gas, add 0.5mL saturated potassium iodide, and
immediately seal the flask and gently shake it for one minute.
5) Leave the flask at room temperature （15 to 20°C） in a dark room.
6) Add 30mL pure water, and seal it and stir.
7) Titrate with 0.01mol/L sodium thiosulfate to measure peroxide value.
※Likewise, obtain blank level in advance by a blank test.
8. Formula
Peroxide value ( meq / kg ) = ( EP1 － BL1 ) × TF × R / SIZE
EP1 ： Titration volume ( mL )
BL1 ： Blank level ( 0.00mL )
TF
： Factor of reagent ( 1.006 )
R
： Constant ( 10 )
SIZE ： Sample size (ｇ)
TIB-99309 Ver.01 2/4
9. Example of measurement
－Ambient condition－
Room temperature：22.5 ℃
Humidity ：
47 ％
-Titration parameterModel
: AT-510
Method No. :
11
Titr.mode : Auto
Intermit
Titr.form : EP Stop
Form
APB No.
Unit No.
Detector No.
Unit
Max.Volume
Wait Time
Direction
:
:
:
:
:
:
:
:
EP Stop
1
1
1
mV
10.0mL
0s
Auto
[Control parameter]
End Point No.
End sense
End Point Area
Separation
Over Titr.Vol.
Gain
Data samp.Pot.
Data samp.Vol.
Stability
Delay Time
Limit Time
:
:
:
:
:
:
:
:
:
:
:
1
Auto
Off
Off
0mL
10
4.0mV
0.1mL
0.5mV/s
1s
0s
Cloudy
-Titration curve*** R e s u l t ***
Sample No. : 41-01
Date : 1999/07/06 11:49
Sample ID :
[Result parameter]
[Titration parameter]
Weather ：
<Calculation>
Calc. Type
: Sample
Conc.1
: Set
CO1=(EP1-BL1)*TF*R/SIZ
E
Unit
: meq/kg
EP No.
: 1
Temp.Comp. : Off
<Constant>
R
Method No.
: 11
<Auto Intermit>
Titr. Time
: 00:10:33
Size
: 5.0794g
Conc-1
: 2.6095meq/kg
End point-1
Volume
: 1.3176mL
Potential : 213.3mV
: 10
<Titr. Constant>
Factor
: 1.006
Conc
: 0.01
<Blank>
Blank1
: 0.00
(The above printout data were obtained from titration by AT-510 unit)
≪Titration parameter≫
Form: of titration / APB No. the burette used in titration / Unit No.: APB Unit File number
Detector No.: the detector used in titration / Max Volume: of titration / Wait Time: before titration starts
Direction: of titration
≪Control parameter≫
End Point No. number of EPs detected / End sense: direction of EP / End Point Area: detection area
Separation: of potential / Over Titr.Vol. over-titration volume / Gain: sensitivity of detection signal
Data samp.Pot.: potential changes of sampling signal / Data samp.Vol.: titration volume of sampling signal
Stability: of titration / Delay Time: before stability check / Limit Time: for stability check
≪Result parameter≫
Calc.Type: of formula / Conc.1 formula 1 / Unit of result
EP No. for calculation / Temp.Comp. temperature compensation of titration liquid / R: constant
Factor: of reagent / Blank1: blank level 1
TIB-99309 Ver.01 3/4
－Measurement results－
Sample
Titration
POV
n
Peroxide value
（ g ）
（ mL ）
（meq / kg ）
1
5.0794
1.3176
2.6095
Mean
2.6267 meq/kg
2
5.0043
1.3053
2.6241
SD
0.0186 meq/kg
3
5.0095
1.3179
2.6465
RSD
0.7095 %
＊The above results were obtained by 3 tests of the same sample.
＊ Red underline shows the data from page 3/4.
10. Summary
The oleic acid reduces bad cholesterol（LDL）of monounsaturated fatty acids but does
not reduce good cholesterol（HDL）. Recently, such advantage attracts public
attention, and cooking oil like canola oil or olive oil which contains oleic acid is on
the market. Unsaturated fatty acid like oleic acid and linoleic acid are liable to be
oxidized with ambient oxygen. Its quality can be controlled by measuring POV.
The measurement results this time shows favorable repeatability with 0.7% relative
standard deviation. Precise and reliable measurement is assured by the automated
potentiometry.
POV of oleic acid can be perfectly measured by any of the following titration systems
manufactured by Kyoto Electronics (KEM).
【AT-610】
Awarded Product of Supreme
Technology from Kyoto City
• Easy key entry by touch panel of
large color LCD （8-inch wide）
• Simultaneous titration in parallel
• Both potentiometric and Karl
Fischer
moisture
titration
(coulometric・volumetric） can be
performed at a time.
【AT-510】
• Compact and cost performance
model
• PC card expands data memory for
convenience and versatility.
【AT-500N-1】
• Low cost and high performance
• Easy view with back light LCD
• GLP/GMP conformed model
TIB-99309 Ver.01 4/4