| HIRANUMA APPLICATION DATA | Automatic Titrator | Data No. | A5 | Oct.7,2022 |
| FOOD | Continuous measurement of citric acid and vitamin C in soft drink |
1.Abstract
Example of sequential titration for vitamin C and citric acid in a soft drink is introduced here.
(1) Firstly, perform neutralization titration for citric acid with sodium hydroxide standard solution.
(2) After the titration, add acetic acid to adjust to acidic pH. Perform redox titration for vitamin C (ascorbic acid) by iodine standard solution.
The sequential titration of citric acid and vitamin C will be possible by additional option (buret and simplified dispenser).
2. Configuration of instruments and reagents
| (1) | Configuration | ||
| Main unit | : | Hiranuma Automatic Titrator COM series | |
| Option | : | One buret, One dispenser (Peristaltic pump type) | |
| Electrodes | : | ・Glass reference electrode GR-501BZ (for measurement of citric acid and vitamin C), Connect to IE-1. ・Platinum electrode PT-301 (for measurement of vitamin C), Connect to IE-2. |
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| (2) | Reagents | ||
| Titrant | : | 0.1 mol/L Sodium hydroxide standard solution (for citric acid) 0.05 mol/L Iodine standard solution (for vitamin C) |
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| Additive solution | : | 10 % Acetic acid solution 5 mL (for pH adjustment) |
3. Measurement procedure
| (1) | Dispense 5 mL of sample into a 100 ml beaker with volumetric pipet. |
| (2) | Add 40 mL of pure water. |
| (3) | Immerse the electrodes and start titration with sodium hydroxide standard solution. |
| (4) | After the above titration, dispense 5 mL of 10 % acetic acid solution automatically (option: simplified dispenser). |
| (5) | Titrate with 0.05 mol/L iodine standard solution (option; buret). |
4. Measurement conditions and results
Examples of titration conditions
(1) Titration of citric acid with sodium hydroxide standard solution
(2) Dispense of 10 % acetic acid
(3) Titration of vitamin C with iodine standard solution
Measurement results
| Number of measurement |
Size (mL) |
Titer (mL) |
Citric acid (%) |
Titer (mL) |
Vitamin C (mg/100mL) |
|---|---|---|---|---|---|
| 1 | 5 | 6.826 | 0.878 | 0.190 | 33.630 |
| 2 | 5 | 6.821 | 0.877 | 0.182 | 32.214 |
| 3 | 5 | 6.823 | 0.878 | 0.191 | 33.807 |
| Average | 0.878% | Average | 33.2mg/100mL | ||
| Statisically | Standard deviation | 0.001% | Standard deviation | 0.9mg/100mL | |
| Coefficient of variant | 0.066% | Coefficient of variant | 2.6% | ||
Examples of titration curve
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5. Note
This method will be quite effective to a labor-saving, because it is possible to measure two target analyte successively by using two different indicator electrodes and titrants.
The measuring method with using iodine (Iodimetry) was introduced here. The measurement of vitamin C by indophenol method is also possible. Please note that the measurement method would be designated depending on the sample when measuring vitamin C.
Keyword: Food, Soft drink, Citric acid, Vitamin C, Neutralization titration, Redox titration, Iodine standard solution
*Some measurement would not be possible depending on optional configuration of system.
