Determination of lactic acid | Autotitrator COM-A19 - JM Science
HIRANUMA APPLICATION DATA Automatic Titrator Data No. K4 Oct. 7,2022
Organic acid Determination of lactic acid

1. Abstract

Lactic acid is oxycarboxylic acid which has carboxy group (-COOH) and alcoholic hydroxyl group (-OH). It shows acidic property when dissolved in water. Lactic acid is produced as raw material of organic compound or food additive.

“JIS (Japanese Industrial Standards) K8726” prescribes the determination method for the lactic acid by the back-titration with sodium hydroxide and sulfuric acid using phenolphthalein indicator. This report introduces an example of the potentiometric titration (formula (1)) with sodium hydroxide standard solution for the measurement of lactic acid sanitizer solution for raw noodles.

2. Configuration of instruments and Reagents

(1) Configuration
  Main unit : Hiranuma Automatic Titrator COM series
    Electrode : Glass electrode GE-101B
Reference electrode RE-201Z
*Instead of the above electrodes, the following electrodes are usable.
・Glass reference combination electrode GR-501BZ…Fixed sleeve type
・Glass reference combination electrode GR-511BZ…Moveable sleeve type
(2) Reagents    
  Titrant : 0.1 mol/L Sodium hydroxide standard solution

3. Measurement procedure

(1) Dispense 20 mL of sample into a 100 mL beaker with volumetric pipette.
(2) Add 40 mL of carbon dioxide-free DI water.
(3) Immerse electrodes and start titration with 0.1 mol/L sodium hydroxide standard solution.

4. Measurement conditions and results

Examples of titration conditions

Cndt No 1
Method Auto
Buret No. 1
Amp No. 1
D. Unit pH
S-Timer 5 sec
C.P. mL 0 mL
T Timer 0 sec
D.P. mL 0 mL
End Sens 1000
Over mL 0.2 mL
Max Vol. 20 mL
Constant No. 1
Size 20 mL
Blank 0 mL
Molarity 0.1 mol/L
Factor 1.0004
K 90.08
L 0
Unit %
Formula
(D-B)*K*F*M/(S*10)
Decimal Places 4
Auto input Param.
Non
Mode No. 20
Pre Int 0 sec
Del K 5
Del Sens 0 mV
Int Time 2 sec
Int Sens 3 mV
Brt Speed 2
Pulse 40

Measurement results

Number of
measurement
Size
(g)
Titrant
volume(mL)
Concentration (%)
1 20 8.193 0.3692
2 20 8.221 0.3704
3 20 8.221 0.3704
Statistic
calculation
Avg. 0.370 %
SD 0.001 %
RSD 0.187 %

Examples of titration curves

5. Note

Oxycarboxylic acid has both properties of carboxylic acid and alcohol. Hydroxyl group enhances the acidic property, and it gets weaker as the position goes farther from COOH.

Keywords: Lactic acid, Neutralization titration,

*Some measurement would not be possible depending on optional configuration of system.

Hiranuma aquacounter autotitrator com-a19Organic acid

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