Quantitative determination of sodium citrate | Autotitrator - JM Science
HIRANUMA APPLICATION DATA Automatic Titrator Data No. B21 Nov. 14,2018
Drugs and Medicines Quantitative determination of sodium citrate

1.Abstract

Sodium citrate is used as anticaking agent for blood in pharmaceutical field. Quantitative determination method for sodium citrate is stipulated in Japanese Pharmacopoeia.
This report introduces an example of potentiometric titration for sodium citrate that well-dried sample is dissolved in acetic acid, then it is titrated with perchloric acid – acetic acid standard solution.

C₆H₅Na₃O₇ + 3HClO₄ → C₆H₈O₇ + 3NaClO₄

 

2. Configuration of instruments and Reagents

(1) Configuration of instruments
  Main unit : Hiranuma Automatic Titrator COM Series
  Electrodes : Glass electrode GE-101B**
    : Reference electrode RE-201Z*
*Inner solution has to be changed to saturated sodium perchlorate in acetic acid.
**Glass-reference combination electrode GR-511BZ is also usable.
(2) Reagents    
  Titrant : 0.1 mol/L perchloric acid – acetic acid standard solution
  Titration solvent : 50 mL of acetic acid (reagent grade)

3. Measurement procedure

(1) Take about 0.1 g of sodium citrate hydrate (C₆H₅Na₃O₇・2H₂O) and dry it at 180 °C for 2 hours.
(This procedure removes the hydrates.)
(2) Take about 0.2 g of the above dried sample into 100 mL tall beaker and weigh accurately.
(3) Add 30 mL of acetic acid and dissolve sample by stirring.
(4) Immerse the electrodes and titrate with 0.1 mol/L perchloric acid – acetic acid standard solution.
Additionally, perform the blank test with the same procedure of sample measurement.

4. Measurement conditions and results

Examples of titration conditions

Measurement of blank

Measurement of blank

Measurement of sodium citrate

Measurement of sodium citrate

Measurement results

Measurement of blank
Number of
Measurement
Size
(g)
Titrant
volume (mL)
1 0.010
2 0.010
Avg.
(Blank)
0.010 mL

 

Measurement of sample
Number of
Measurement
Size
(g)
Titrant
volume (mL)
Concentration
(%)
1 0.2029 23.419 99.640
2 0.2052 23.675 99.601
3 0.2052 23.670 99.580
Statistic
calculation
Avg.
SD
RSD
99.61 %
0.0304 %
0.03 %

 

Examples of measurement curves

  • Measurement of blank

 

  • Measurement of sample

 

5. Note

(1) Effect of water on perchloric acid titration
 Water mixed in a measurement system affects to the reaction system of perchloric acid titration because of the leveling effect, which results in a negative effect such as lowered quantitative performance or getting less sensitivity around the end point. Therefore please take care not to mix water in the measurement system. Reference electrode for non-aqueous titration should be prepared as described in the following item (2), because water of KCl solution commonly used as inner solution for reference electrode could be mixed in the measurement system.
(2) Preparation of inner solution for reference electrode
 The inner solution of the reference electrode RE-201Z is filled with 4 M KCl aqueous solution when purchased. This inner solution have to be replaced to saturated sodium perchlorate in acetic acid solution for this measurement. Replacement procedure is described below.
i) Prepare the saturated solution of sodium perchlorate in acetic acid with reagent grade.
ii) Discharge inner solution from reference electrode RE-201Z and wash inside it with water and then acetic acid.
iii) Fill the prepared inner solution into reference electrode from the supply port.
iv) Cure the electrode for one day before use.
(3) Influence of experiment temperature on perchloric acid titration
 Acetic acid used as a solvent for the titrant has a relatively large thermal expansion coefficient. When the temperature changes by 1 °C, the titrant causes a volume change of 0.1 %. Factor titration and sample measurement should be performed at the same room temperature as much as possible for accurate measurement. (Please refer to application data B19 in regards to factor correction.)

 

Keywords: Sodium citrate, Perchloric acid titration, Non-aqueous titration

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

Drugs and medicines

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