Continuous measurement of citric acid and vitamin C in soft drink | Autotitrator - JM Science
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.

sequential titration for vitamin C and citric acid in a soft drink

(1) Firstly, perform neutralization titration for citric acid with sodium hydroxide standard solution.

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.

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.
(2) Reagents
Titrant : 0.1 mol/L Sodium hydroxide standard solution (for citric acid)
0.05 mol/L Iodine standard solution (for vitamin C)
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

(1) Titration of citric acid with sodium hydroxide standard solution

 (2) Dispense of 10 % acetic acid

Dispense of 10 % acetic acid

(3) Titration of vitamin C with iodine standard solutionTitration 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

 

  • Measurement of citric acid

  • Measurement of vitamin C

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.

 

Food

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