HIRANUMA APPLICATION DATA

Karl Fischer Titrator

Watercontents

Data No.

KF6

Nov.29.
2018

Amines

1. Abstract
Water content of amines 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－The amines change anode solution pH to basic. In the case of an amine with stronger basicity thanbenzylamine (pKa = 9.34 1)) as a guideline, there are such effects as the end point becomes unclear. Therefore,
when measuring a strongly basic amine, add a neutralizing agent to the anode solution beforehand to suppress
the influence of undesirable effect caused by adding the sample. This application introduces an example for thewater determination in cyclohexylamine(liquid), diethanolamine(liquid) and imidazole(solid).
Reference
1) H. K. Hall, J. Am. Chem. Soc. (1957) 79 5441.

2. Apparatus and Reagents(1) ApparatusTitrator：

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)

Neutralizing agent：

Benzoic acid

3. Procedure
3.1. Measurement of liquid sample(1) Add 10 g of benzoic acid and 100 mL of anode solution in anode compartment of titration cell asshown in Fig.3.1. Add one ampoule of cathode solution into the cathode compartment. When fritlesscell is used, cathode solution is not necessary. Stir the anode solution to dissolve benzoic acid.
(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.
.

3.2. Measurement of solid sample(1) Add 10 g of benzoic acid and 100 mL of anode solution in anode compartment of titration cell asshown in Fig.3.1. Add one ampoule of cathode solution into the cathode compartment. Stir the anodesolution to dissolve benzoic acid.
(2) Start blanking to attain stable background.
(3) Put a sample container, powder funnel and spoon on the balance. Record its read (S1 [g]).
(4) Open the glass stopper of titration cell lid to introduce the sample with powder funnel as shown inFig.3.3.
(5) Start titration. Measurement parameter is shown in Table 4.1.
(6) Weigh the sample container, powder funnel and spoon again and record its read (S2 [g]). The
difference of (S1-S2 [g]) is set as sample size.
(7) Blank measurement is also performed with same procedure except for sample addition.
Anode solution

Cathode 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 liquid sample.

.

Fig.3.3. Addition of solid sample.

4. Parameters and results
Table 4.1. Parameters
Condition File
Cal ModeInterval Time
Current
S.Timer *Blank Value
Unit Mode
Auto Interval
Minimum Count
Back Ground
Sample Size Input
Cell Type0:Sample weight (net)
X=(H2O-BLANK)/SIZE20
SLOW00
AUTO
05ON
Every Time
Standard / Fritlesssecminµggµg* Dissolving time for solid sample set on S.Timer.

Table 4.2. Results of water content measurement in amines
CellSample
size (g)Water(µg)

Water content(%)

Standard0.1742

235.50.1352

Avg.

0.1350%+ Benzoic acid0.1790

239.5

0.1338SD

0.0011%/ CG

0.1941263.8

0.1359

RSD

0.8

%

0.2232307.1

0.1376Avg.

0.1367%0.2694366.1

0.1359SD

0.0009%0.2305315.00.1367

RSD

0.6

%

0.2465478.1

0.1940Avg.

0.1923%0.2877557.8

0.1939SD

0.0029%0.2340442.3

0.1890

RSD

1.5

%

0.2361476.8

0.2019Avg.

0.2020%0.2473505.00.2042SD

0.0022%0.2696538.9

0.1999

RSD

1.1

%

0.4219643.7

0.1526Avg.

0.1524%0.6296964.0

0.1531

SD0.0008%

0.3946597.7

0.1515RSD

0.5%

0.2336371.5

0.1590Avg.

0.1586%

0.3491547.7

0.1569

SD0.0015%

0.2551

407.60.1598

RSD

0.9%Sample

Reagent

Cyclohexylamine

AGAG

Fritless+ Benzoic acid

Diethanolamine

AGStandard/ CGAG

Imidazole

AG

Fritless

Standard/ CGAG

Fritless

Statistics result

5. Note(1) When the side reaction of amine cannot be suppressed even though you use neutralizing agent,phenomena such as unstable blanking or undetectable endpoint can be obtained. In that case, it may be
improved by reducing the amount of sample or replacing titration solvent with new one.
(2) Since aromatic amines react with methanol to form water, it is necessary to use reagent for ketone.
(3) 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.

Keywords：Karl Fischer, Coulometric titration, Amine.