| 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.
