Ethers and Esters | Karl Fischer titrator AQ-300/MOICO-A19 - JM Science
HIRANUMA APPLICATION DATA Karl Fischer Titrator Data No. KF5 Jun.6. 2017
Water contents Ethers and Esters

1. Abstract

Water content of Ethers and Esters are determined by Karl Fischer coulometric titrator. In coulometric titration, iodine of Karl Fischer reagent is generated by electrolysis and generated iodine quantitatively reacts with water. Reaction formula is described below.

 H₂O + I₂ + SO₂ + 3RN + CH₃OH → 2RN・HI + RN・HSO₄CH₃

 2RN・HI → I₂ + 2RN + 2H⁺ + 2e⁻

Ethers and esters do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected from General-use or Oil in accordance with sample solubility. General-use anode solution contains methanol as solvent. When the sample has low solubility in methanol, the use of anode solution for oil is appropriate. One exception is a sample containing vinyl group, which reacts with KF reagent and interferes the titration. When fritless cell is used, cathode solution is not necessary.

2. Apparatus and Reagents

(1) Apparatus    
  Titrator : HIRANUMA Karl Fischer Coulometric titrator AQ-series or MOICO-A19
  Electrolytic cell : Standard Cell
Fritless Cell
(2) Reagents    
  Anode solution : Hydranal coulomat AG (for general use, nonhalogenated)
  Cathode solution : Hydranal coulomat CG

3. Procedure

(1) Fill 100 mL of anode solution and one ampoule of cathode solution into the electrolytic cell as shown in Fig.3.1.
(2) Start blanking to attain stable background.
(3) Wash the syringe with sample.
(4) Draw the sample into syringe and then weigh the syringe.
(5) Inject sample from rubber septum of electrolytic cell as shown in Fig.3.2.
(6) Start titration. Measurement parameter is shown in Table 4.1.
(7) Weigh the syringe again and then set the difference of weight to sample size.

Fig.3.1. Preparation of the reagents.



Fig.3.2. Injection of sample.

4. Parameters and results

Table 4.1. Parameters

Condition File    
Cal Mode 0:Sample weight(net)  
  X=(H₂O-BLANK)/SIZE  
Interval Time 20 sec
Current SLOW  
S-Timer 0 min
Blank Value 0 ug
Unit Mode AUTO  
Auto Interval 0 g
Minimum Count 5 ug
Back Ground ON  
Sample Size Input Every Time  
Cell Type Standard/Fritless  

 

Table 4.2. Results of water content measurement in ethers and esters

Sample Apparatus Cell Reagent Sample
Size (g)
Water
(μg)
Water
Content
Anisole AQ Standard AG 2.0827 341.4 163.9 ppm
      CG 1.9764 323.9 163.9
        2.0089 329.1 163.8
             
    Fritless AG 2.0984 341.8 162.9 ppm
        1.9812 323.3 163.2
        1.9649 321.9 163.8
Ethyl acetate AQ Standard AG 0.8797 395.0 449.0 ppm
      CG 1.0007 449.8 449.5
        1.0423 470.4 451.3
             
    Fritless AG 0.9985 451.7 452.4 ppm
        1.1310 512.8 453.4
        1.0082 456.6 452.9
Diethyl ether AQ Standard AG 0.7746 567.1 732.1 ppm
      CG 0.7844 573.4 731.0
        0.8011 585.9 731.4
             
    Fritless AG 0.8379 608.9 726.7 ppm
        0.9185 672.9 732.6
        0.8504 626.0 736.1
1,4-dioxane AQ Standard AG 0.3480 330.8 950.6 ppm
      CG 0.5230 493.2 943.0
        0.3995 381.5 954.9
             
    Fritless AG 0.4492 425.1 946.3 ppm
        0.5779 547.7 947.7
        0.5552 525.0 945.6
4-butyrolactone AQ Standard AG 0.9274 61.2 66.0 ppm
      CG 1.19304 70.8 59.3
        1.22069 72.3 59.2
             
    Fritless AG 1.13511 79.2 69.8 ppm
        1.10311 70.2 63.6
        0.81464 51.3 63.0
Propylene carbonate AQ Standard AG 1.27881 230.2 180.0 ppm
      CG 0.90269 159.9 177.1
        1.17183 204.3 174.3
             
    Fritless AG 1.29844 229.5 176.8 ppm
        1.27775 224.7 175.9
        1.18092 210.5 178.3

5. Note

(1) Use dried syringe and syringe vial for preventive of contamination by atmospheric water.
(2) Put appropriate anode solution in use according to the solubility of the sample. For example, Hydranal Coulomat AG-H and Oil are suitable for oils.
Note : these reagents does not correspond to Fritless cell.
Hiranuma aquacounter aq-300 coulometric karl fischer titratorHiranuma aquacounter coulometric karl fischer titrator moico-a19Water contents

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