HIRANUMA APPLICATION DATA

Data No. A10

Automatic Titrator

Nov 27,2023

Peroxide value measurement for cooking oil

FOOD
1. Abstract

Degraded fats and oils include peroxide chemical species. Therefore, determination of peroxide value is aneffective analytical method to know the index of fat and oil degradation. This method is described in a variety ofofficial standards in fats, oils, health science and pharmaceutical area.
Definition of peroxide value depends on respective standard method. For example, “Method of Analysis in
Health Science” in Japan defines peroxide value as “milliequivalents of iodine generated from potassium iodide
in 1 kg of sample [meq/kg]” (Formula (1)). The generated iodine is finally titrated with sodium thiosulfate(Formula (2)).
Example of titration for peroxide value in cooking oil is introduced here. The experimental procedure
conforms to the “Japanese Agricultural Standards”.
R－OOH
I2＋＋2I- ＋

2Na2S2O3

2H+→

R－OH

→

2NaI＋＋

I2 ＋H 2O

Na2S4O6・・・(1)・・・(2)

2. Configuration of instruments and Reagents(1) Instruments
Main unit：

Automatic Titrator COM series

Electrode：

Platinum-Reference combination electrode(long type) PR-733BZ

Options：

Shaft modifications to the stirrer supplied with the unit, buret tip modifications
and modifications to the tube holder and other ancillary components are required.
(Refer to “5. Note (4)”)(2) Regents
Titrant：

0.01 mol/L Sodium thiosulfate standard solution

Additive：

Saturated potassium iodide solution
Dissolve 80 g of potassium iodide in 50 mL of DI water.

Solvent：

Mixed solvent of 2,2,4-trimethylpentane and acetic acid with 2 : 3 ratio [v/v]

Purge gas：

Nitrogen gas

3. Measurement procedure(1) Take about 10 g of the sample into 200 mL Erlenmeyer flask with stopper and weigh it accurately.
(2) Add 60 mL of mixed solvent to dissolve sample.
(3) The air in flask is purged with nitrogen gas for 1 minutes. The flow rate of nitrogen gas is 300 mL/min.
(4) Add 1 mL of saturated potassium iodide solution with pipette. Close the flask with stopper and swirl gentlyfor 1 minute.
(5) Leave the flask to stand for 5 minutes in dark place.
(6) Add 60 mL of DI water to the flask.
(7) Immerse the electrode and titrate with 0.01 mol/L sodium thiosulfate standard solution.
(8) Measure the blank value by testing of (2) ~ (7) without sample.
(9) After the measurement finished, the electrode should be immersed in mixed solvent, and additionallywashed with DI water. Besides immerse it in DI water between each measurement to activate electrode.

4. Measurement conditions and Results
Examples of titration conditions
Measurement of blankCondition No. 1
MethodMode No.

15Buret No.

Auto
1Constant No.
Size

0.00000

1gPre Int

1Amp No.

1Blank0.0000

mL

Del K

3D.UnitmVMolality

0.0100mol/L

Del Sens

0mV

S-Timer30

sec

Factor

1.00400

Int time5sec

CP mL0mLK

0.00000

Int Sens

3mVT-Timer

0sec

L

0.00000

Buret Speed

2D.P. mL

0

mL

Unit

mLPulse40

End Sens

200

FormulaD

Over mL

0mL

DigitsMax. Vol.

20mL

Auto input Parameter

sec

0.05

mL

3
None

Measurement of sample
Condition No. 2
MethodBuret No.

AutoConstant No.

2

Mode No.

201Size

0.00000g

Pre Int

1Amp No.

1Blank

0.1270mL

Del K

5D.UnitmV

Molality

0.0100mol/L

Del Sens

0mV

S-Timer30

sec

Factor

1.00400

Int time

5sec

CP mL

0mL

K

10.00000

Int Sens

3

mV

T-Timer0sec

L

0.00000

Buret Speed

2D.P. mL

0mL

Unit

meq/kg

Pulse

40

End Sens

200

Over mL

0.2

mL

DigitsMax. Vol.

20mL

Auto input Parameter

Formula(D-B)*K*F/S

0.050

4None

sec

mL

Measurement results
SampleMeasurement

Size

Titrant

Peroxide value

No.

(g)

volume (mL)(meq/kg)

1-0.122-2-0.131-110.0262

0.954

210.0213

310.0051

BLANK

SAMPLE

Statisticalresult
Avg.

0.127

mL

0.8281Avg.

0.82

meq/kg0.929

0.8035SD

0.01

meq/kg0.949

0.8219RSD

1.56%

Measurement of blank

Measurement of sample

Examples of measurement curves

5. Note(1) Please use Erlenmeyer flask with stopper to avoid sublimation of iodine and entraining of oxygen from air.
(2) Timely measure the blank because saturated potassium iodide solution is easy to degenerate. Additionally,please periodically prepare fresh solution.
(3) The type of solvent used in this measurement, the amount of solvent added, and the time left in the darkvary with each standard test methods. Please make the appropriate modifications according to the standard
test methods used.
(4) In this report, since a 200 mL Erlenmeyer flask is used as a titration vessel, platinum-reference combinationelectrode PR-733BZ (Long type) was used. The stirrer is modified to accommodate Erlenmeyer flasks asshown in Fig. 1 to attach the long type electrode.

Figure 1

A set of electrode and stirrer parts for Erlenmeyer flasks

Keywords：Cooking oil, Peroxide value, Redox titration※Some measurement would not be possible depending on the optional configuration of system.