Karl Fischer Titrator

HIRANUMA APPLICATION DATA

Watercontents

Data No.

KF8Jun.6.
2017

Oil products – Fuel oil

1. Abstract
Water content of oil products 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－
Generally the fuel oil does not interfere the Karl Fischer reaction and direct injection method could apply.
Suitable anode solution is selected for dissolving oil samples.
It is known that some of the oil additives interfere Karl Fischer reaction. In that case, azeotropic distillation
method with Oil evaporator is appropriate. Water is separated from oil sample by distillation and introduced toelectrolytic cell with carrier gas.

2. Apparatus and Reagents(1) Apparatus
Titrator：

Karl Fischer Coulometric titrator

AQ-2200A

Evaporator：

Oil Evaporator

EV-2000L

Electrolytic cell：Standard Cell

(2) Reagents for direct injection methodAnode solution：

Hydranal coulomat AG-H / Oil

Cathode solution：

Hydranal coulomat CG(3) Reagents for azeotropic distillation method
Anode solution：

Hydranal coulomat AG (for general use, nonhalogenated)

Cathode solution：

Hydranal coulomat CG

Distillation solvent：

Dehydrated toluene

Carrier gas：

Nitrogen gas

3. Procedure
3.1. Direct injection method(1) Fill 100 mL of anode solution and one ampoule of cathode solution into the electrolytic cell as shownin 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.
Anode solution

Cathode solution

Fig.3.1. Preparation of the reagents.
Note(1) Do not touch the tip of needle toanode solution.
(2) When injecting, set the tip ofneedle as below figure.

(3) Before pulling out the needle,
draw alittle

airdripping of sample.

Fig.3.2. Injection of sample.

toprevent3.2. Azeotropic distillation method(1) Fill 100 mL of anode solution and one ampoule of cathode solution into the electrolytic cell as shownin Fig.3.1.
(2) Start blanking to attain stable background.
(3) Connect electrolytic cell and evaporation chamber with tube. Flow carrier gas with 50 mL/min.
(4) Fill 5 mL of distillation solvent in evaporation chamber and heat the chamber at 120 C.
(5) Keep blanking to attain stable background with carrier gas flowing into electrolytic cell.
(6) Wash the syringe with sample.
(7) Draw the sample into syringe and then weigh the syringe.
(8) Inject sample from rubber septum of distillation chamber as shown in Fig.3.3 and Fig.3.4.
(9) Start titration. Measurement parameter is shown in Table 4.2.
(10) Weigh the syringe again and then set the difference of weight to sample size.

Fig.3.3. Schematic diagram of azeotropic distillation method.
Note(1) Do not touch the tip of needle todistillation solvent level.
(2) When injecting, set the tip of needle asbelow figure.

(3) If air is drawn at inside of evaporationchamber, distillation solvent would beinvolved. When drawing air, do it after
pulling out the needle from evaporationchamber to prevent weighing error.

Fig.3.4. Sample injection into evaporation chamber.

4. Parameters and results
Table 4.1 Parameters for direct injection method
Condition File
Cal ModeInterval Time
Current
S.TimerBlank Value
Unit Mode
Auto Interval
Minimum Count
Back Ground
Sample Size Input
Cell Type

0:Sample weight (net)
X=(H2O-BLANK)/SIZE
20SLOW00
AUTO05ON
Every TimeStandardsecminuggug

Table 4.2 Parameters for azeotropic distillation method
Condition File
Cal ModeInterval Time
Current
Min.Timer
Blank Value
Unit Mode
Auto Interval
Minimum Count
Back Ground
Sample Size Input
Cell Type

0:Sample weight (net)
X=(H2O-BLANK)/SIZE
40
SLOW
50
AUTO05ON
Every Time
Standardsecminuggug

Table 4.3 Results of water content measurement in Oil products
SampleSize (g)water(μg)

WatercontentAGCG

2.12682.20442.1970

82.8
83.0
77.6

39.0 ppm
37.7
35.3

StandardAGCG

2.0054
1.9829
1.9999

132.3
122.3
130.4

66.0 ppm
61.7
65.2AQ+EV-L

StandardAGCG

0.95290.25090.493815482.0
3911.37982.01.6248 %1.55891.6164

AQ

StandardAG-HCG

9.50009.5402
9.6370

398.8
388.0
398.1

42.0 ppm
40.7
41.3

SampleApparatus

Cell

Reagent

Gasoline

AQ+EV-L

Standard

Heavy oil A

AQ+EV-L

Heavy oil C

Aviation fuel5. Note
(1) Use dried syringe and syringe vial for preventive of contamination by atmospheric water.
(2) To measure 100 µg or less water detection, make sure stability of blanking. Low and stable backgroundvalue is important factor for trace level of water measurement.
(3) 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 with direct injection method.
Note : these reagents does not correspond to Fritless cell.