Alcohols | Karl Fischer titrator AQ-300/MOICO-A19 - JM Science
HIRANUMA APPLICATION DATA Karl Fischer Titrator Data No. KF2 Jun.6. 2017
Water contents Alcohols

1. Abstract

 Water content of Alcohols is 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⁻

 Alcohols do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected in accordance with sample solubility. General-use anode solution contains methanol as solvent. Alcohols with long carbon chain have low solubility in methanol. In that case, use of anode solution for oil is appropriate.
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 alcohols

Sample Apparatus Cell Reagent Sample
Size (g)
Water
(μg)
Water
Content
Methanol AQ Standard AG 0.5988 672.9 1124 ppm
      CG 0.8890 991.6 1115
        0.8710 973.6 1118
             
    Fritless AG 0.9415 1047.4 1112 ppm
        0.8964 996.7 1112
        0.8739 972.3 1113
2-propanol AQ Standard AG 1.5078 138.9 92.1 ppm
      CG 1.6015 145.7 91.0
        1.6574 152.6 92.1
             
    Fritless AG 1.5623 142.7 91.3 ppm
        1.5496 139.4 90.0
        1.5832 142.9 90.3
2-methoxyethanol AQ Standard AG 0.86583 156.4 180.6 ppm
      CG 1.36865 243.5 177.9
        0.83448 150.1 179.9
             
    Fritless AG 1.0574 188.2 178.0 ppm
        0.95761 172.1 179.7
        1.02781 185.3 180.3
n-hexylalcohol AQ Standard AG 0.87698 132.1 150.6 ppm
      CG 0.92031 138.0 149.9
        0.81105 124.0 152.9
             
    Fritless AG 0.80510 122.9 152.7 ppm
        0.85949 131.1 152.5
        0.97448 148.7 152.6

5. Note

(1) Use dried syringe and syringe vial in Fig.5.1, 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.


Fig.5.1. Draw the sample from syringe vial.

Hiranuma aquacounter aq-300 coulometric karl fischer titratorHiranuma aquacounter coulometric karl fischer titrator moico-a19Water contents

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