HIRANUMA APPLICATION DATA

Karl Fischer Titrator

Watercontents

Data No.

KF7

Nov.28.
2018

Nitriles

1. Abstract
Water content of Nitriles 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・HSO4CH32RN・HI → I2 ＋ 2RN ＋ 2H＋ ＋ 2e－Nitriles 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 has poor solubility in methanol, anode solution containing
chloroform or hexanol or toluene is used.

2. Apparatus and Reagents(1) Apparatus
Titrator：

Hiranuma Karl Fischer Coulometric titrator

Electrolytic cell：Standard Cell

AQ-series

Fritless Cell (No cathode solution required)(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 shownin Fig.3.1. When fritless cell is used, cathode solution is not necessary.
(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.

Cathode solution

Anode solution

Fig.3.1. Preparation of the reagents. (Standard Cell)
Note(1) Do not touch the tip of needle to anodesolution.
(2) When injecting, set the tip of needle asbelow figure.

(3) Before pulling out the needle, draw alittle air to prevent dripping of sample.

Fig.3.2. Injection of sample.

4. Parameters and results
Table 4.1. Parameter.
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)/SIZE20
SLOW00AUTO
05ON
Every Time
Standard / Fritless

secminµggµg

Table 4.2. Results of water content measurement in nitriles.
SampleCellSample
size (g)Water(μg)

Water content(ppm)

Acetonitrile

Standard

1.5175

151.1

99.6

1.5675

158.5

101.1

1.5602

151.5

97.1

1.5305

153.7

100.4

1.4616

147.1

100.6

1.5896

156.4

98.4

0.78380

255.4

325.8

0.77352

253.0

327.1

0.97904

318.0

324.8

0.95859

312.6

326.1

0.87339

283.5

324.6

0.95782

311.6

325.3

Fritless

3-Ethoxypropionitrile

Standard

Fritless

Statistics result

Avg.
SDRSD

99.3
2.0%

Avg.
SDRSD

99.8ppm

Avg.
SDRSD

325.9 ppm

Avg.
SDRSD

325.3 ppm

ppm

2.0 ppm

1.2 ppm
1.2%

1.2 ppm
0.4%

0.8 ppm
0.2%

5. Note(1) Use dried syringe and syringe vial in Fig.5.1 for preventive of contamination by atmospheric water.

(2) To measure 100 µg or less water detection, make sure stability of blanking. Low and stablebackground 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 Hydranal coulomat Oil are suitable for long chain hydrocarbons and oil samples.
(4) The optimized electrolysis control for fritless cell of AQ series released after 2009 improves themeasurement 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 fritlesscell.
Load the sample.

Syringe*Standard accessory

Drying tube filledwith molecular sieves
PTFE-laminatedSilicon septum
Vial
air

SampleFig.5.1. Draw the sample from syringe vial.
Keywords：Karl Fischer, Coulometric titration, Direct injection, Nitrille, Fritless cell