Hydrocarbon, Halogenated hydrocarbon | Karl Fischer titrator AQ-300/MOICO-A19 - JM Science
HIRANUMA APPLICATION DATA Karl Fischer Titrator Data No. KF1 Mar. 8 2018
Water contents Hydrocarbon, Halogenated hydrocarbon

1. Abstract

Water content of hydrocarbon and halogenated hydrocarbon could be 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⁻

Hydrocarbon and halogenated hydrocarbon do not interfere the Karl Fischer reaction and direct injection method could apply. Anode solution is selected in accordance with sample solubility. General use of anode solution contain methanol as solvent. When the sample like a long chain hydrocarbon have poor solubility in methanol, anode solution containing chloroform or hexanol or toluene is used. 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 (Honeywell)
  Cathode solution : Hydranal coulomat CG (Honeywell)

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. Parameter.

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 hydrocarbons.

Sample Apparatus Cell Reagent Sample
Size (g)
Water
(μg)
Water Content
(ppm)
Statistics Results
Heptane AQ Standard AG 1.0418 35.6 34.2 Avg. 32.8 ppm
      CG 1.0617 34.4 32.4 SD 1.2 ppm
        1.0936 34.8 31.8 RSD 3.8 %
                 
    Fritless AG 1.1425 36.8 32.2 Avg. 31.5 ppm
        1.0688 33.1 31.0 SD 0.6 ppm
        1.0431 32.6 31.3 RSD 2.0 %
Chloroform AQ Standard AG 2.9461 88.1 29.9 Avg. 30.7 ppm
      CG 2.9798 93.0 31.2 SD 0.7 ppm
        2.9071 89.9 30.9 RSD 2.2 %
                 
    Fritless AG 2.7729 84.6 30.5 Avg. 30.2 ppm
        2.9253 85.8 29.3 SD 0.8 ppm
        2.9486 90.7 30.8 RSD 2.6 %
Cyclohexane AQ Standard AG 1.5958 61.9 38.8 Avg. 38.0 ppm
      CG 1.5791 59.0 37.4 SD 0.7 ppm
        1.5795 59.9 37.9 RSD 1.9 %
                 
    Fritless AG 1.6039 60.2 37.5 Avg. 37.4 ppm
        1.5384 57.7 37.5 SD 0.2 ppm
        1.6157 60.1 37.2 RSD 0.5 %
Isooctane AQ Standard AG 1.32027 63.7 48.2 Avg. 48.6 ppm
      CG 1.47262 71.8 48.8 SD 0.3 ppm
        1.43564 69.9 48.7 RSD 0.7 %
                 
    Fritless AG 1.43916 68.0 47.2 Avg. 47.3 ppm
        1.42384 66.2 46.5 SD 0.9 ppm
        1.44880 69.9 48.2 RSD 1.8 %

5. Note

(1) Use dried syringe and syringe vial at sampling for prevention of contamination by atmospheric water.
(2) To measure 100 µg or less water detection, make sure stability of blanking. Low and stable background value is important factor for trace level of water measurement.
(3) Select anode solution according to the solubility of the sample. For example, Hydranal Coulomat AG-H and Oil are suitable for long chain hydrocarbons and oils.
(4) The optimized electrolysis control for fritless cell of AQ series released after 2009 improves the measurement accuracy of fritless cell. It can be used with the evaporator as well. Suitable reagent for fritless cell is required. For example, Hydranal coulomat AG and AG-Oven are compatible with fritless cell.

Keywords: Karl Fischer, Coulometric titration, Direct injection, Hydrocarbon, Fritless cell
Hiranuma aquacounter aq-300 coulometric karl fischer titratorHiranuma aquacounter coulometric karl fischer titrator moico-a19Water contents

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