HIRANUMA APPLICATION DATA

Data No

Automatic Titrator

A7Apr. 19,
2018

Acid value of cooking oilFOOD

1. Abstract
Acid value of oils and fats is defined as “amount (mg) of potassium hydroxide required to neutralize fatty acid in 1 g ofsample” (Formula (1)).
R-COOH + KOH → R-COOK + H2O・・・(1)

It is used for evaluation of free fatty acid content as quality index of oils and fats. This method is described in a varietyof official standards such as “Japan Agricultural Standards” and Pharmacopoeias. Example of titration for acid value incooking oil is introduced here.
Reference1) Japanese Pharmacopoeia Seventeenth Edition

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

COM series

Electrodes： Glass reference combination electrodeGR-522BZ, Connect to IE-1

Components： Buret tip (Tube Type), tubing accessories(2) Reagents
Titrant： 0.1 mol/L Pottasium hydroxide ethanolic standard solution

Titration solvent： Mixed solvent of ethanol and diethyl ether with 1 : 1 ratio [v/v]

3. Measurement procedure(1) Take 20 g* of sample into 200 ml Erlenmeyer flask and weigh it exactly.
(2) Add 100 ml of titration solvent and dissolve the sample.
(3) Immerse the electrode and start titration.
(4) Blank measurement is also performed with procedure (2) – (3).
(5) After titration finished, wash electrode with solvent and then immersed into DI water for 5 minutes to maintainresponse of glass electrode.
※ Sample size depends on expected value, and it’s described in a standard method.

4. Measurement conditions and results
Examples of titration conditions
Measurement of blank
Condition No. 1
MethodAutoConstant No.

1Mode No.

15Buret No.

1Size0 g

Pre Int

5 sec

Amp No.

1Blank

0 mL

Del K

0D.UnitmVMolality

0.1 mol/L

Del Sens

0 mV

S-Timer

180 sec

Factor0Int time

3 sec

CP mV

300 mV

K0Int Sens

3 mV

Direction↑L

0Buret Speed

2D.P. mV-100 mV

Unit

mL

End Sens

500

FormulaD

Over mL

0.1 mL

Digits3Max. Vol.

1 mL

Auto input Parameter

Pulse

200.025 mL

None

Measurement of sample
Condition No. 2
MethodAutoConstant No.

2Mode No.

20Buret No.

1Size0 g

Pre Int

5 sec

Amp No.

1Blank

0.013 mL

Del K

0D.UnitmVMolality

Del Sens

0 mV

S-Timer

180 sec

Factor

0.9999Int time

3 sec

CP mV

300 mVK

56.11

Int Sens

3 mV

Direction↑L

0Buret Speed

2

D.P. mV-100 mV

Unit

mg/g

Pulse

40

End Sens

200

Formula(D-B)*K*F*M/SOver mL

0.5 mL

DigitsMax. Vol.

20 mL

Auto input Parameter

0.1 mol/L

0.050 mL

3None

Measurement results
SampleBLANK

SAMPLE

Measurement

Size

Titrant

Acid Value

No.

(g)

volume (mL)

(mgKOH/g)

1-0.013

-

2-

0.013

-

120.2103

3.075

0.850

220.0897

3.051

320.0007

2.936

Statisticalresult
Avg.

0.013

mL

Avg.

0.839

mgKOH/g

0.848

SD0.017

mgKOH/g

0.820

RSD

2.00%

Measurement of blank

Measurement of sample

Examples of measurement curves

5. Note(1) Maintenance of electrodeAs glass electrodes continue to be used in nonaqueous solvents, sensitivity decreases. To recover the sensitivity of glass
electrode, immerse the electrode into DI water for 5 minutes after each measurement. Similarly, when referenceelectrode is used in a nonaqueous solvent, KCl tend to crystallize on the sleeve part of reference electrode. Crystals of
KCl can be easily washed off with water.
(2) Method of endpoint detection
In this report, titration curve shows clear inflection point as endpoint. When the sample is used oil, inflection points may
be unclear and cannot be detected. In that case, endpoint could be defined as fixed pH value within indicator range for
pH indicator reagent. Parameters “Method” could be set to “SET” to detect endpoint with fixed pH. And parameter“Endpoint pH” also could be set to defined pH value.
Keywords：Cooking oil, Acid value, Pharmacopoeia* Some measurement would not be possible depending on optional configuration of system.