HIRANUMA APPLICATION DATA

Watercontents

Karl Fischer Titrator

Data No. KF19

Feb. 10,
2021

Sugars – KF Volumetry, granulated sugar
Factor standardization with water standard

1. Abstract
Water contents of granulated sugar could be determined by Karl Fischer volumetric titrator. In volumetrictitration, titrant have a factor which means the amount to react with water per 1 mL of titrant. The factor is
pre-determined before sample measurement and water content of sample is calculated from the consumed
titrant volume by sample measurement.
This application introduces an example for the water determination in granulated sugar. Due to the low watercontent of this sample, a relatively large amount of sample must be added, but the solubility in methanol astitration solvent is not sufficient. Sugars have tendency to dissolve in formamide. Therefore a mixed solvent offormamide and methanol was chosen as the titration solvent. To make it easier to dissolve the sample, thetitration cell was heated to 45 C using an outer chamber for flowing warm water.
Since the water content of the granulated sugar is often a few hundred ppm, the titrant with low factor value,as 1 mg/mL was used. When pure water is used as the standard material of factor standardization for low factor
titrant, the amount of pure water added should be as small as 10 to 20 mg, which makes accurate addition andweighing difficult. Therefore, water standard material which is the solution containing 1 % of water sealed inglass ampoule is used for the factor standardization.

2. Apparatus and Reagents(1) Apparatus
Titrator：

Karl Fischer Volumetric titrator

AQV-series

Titration cell：

Titration cell with cooling chamber

P/N D327510-1* This cell could not fit to the stirrer of AQV-300.

：：

less than 12 mm outer diameter of leg
Glass, 10 mL

Titrant：

HYDRANAL Composite 1 (Honeywell)

Methanol：

HYDRANAL Methanol (Honeywell)

Formamide：

HYDRANAL Formamide dry (Honeywell)Titration solvent：

Mixed solvent of methanol and formamide at a volume ratio of 1: 2

Standard material：

Water standard 10 (certificate of analysis : 10.00 mg/g)

Powder funnel
Syringe(2) Reagents* Equivalent product can be substituted these reagents.
(3) OtherHeating device：

Temperature-controlled bath with circulation function* Commercial item3. Procedure
3.1 Factor standardization(1) Fill 50 mL of titration solvent into the titration cell as shown in Fig.3.1.
(2) Circulate 45 C water in the outer chamber of the titration cell with using a temperature-controlled
bath, to heat the titration solvent.
(3) Start blanking to attain stable background.
(4) Open an ampoule of water standard 10 and collect the contents in a syringe. To prevent injury when
opening the ampoule, handle it according to the instructions of standard material.
To make easier to collect, it is helpful to use packing box of standard material to stand the ampoule asshown by an example in Fig.3.2.
(4) Put the syringe on the balance. Record its read (S1 [g]).
(5) Inject sample from rubber septum of titration cell as shown in Fig.3.3.
(6) Start titration. Measurement parameter is shown in Table 4.1.
(7) Weigh the syringe again and record its read (S2 [g]). The difference of (S1-S2 [g]) is set as samplesize.
Titration solvent

Outer chamber→ OUT
Circulated warm water← IN

Fig.3.1 Preparation of the reagents

Fig.3.2 Example of water standard ampoule and its packing box.

Note(1) Do not touch the tip of needle to titration
solvent.
(2) When injecting, set the tip of needle as below
figure. The diagonally cut surface of the needle
tip faces downward.

(3) Before pulling out the needle, draw a little air toprevent dripping of sample.

Fig.3.3. Injection of sample.
3.2. Sample measurement(1) Fill 50 mL of titration solvent into the titration cell as shown in Fig.3.1.
(2) Circulate 45 C water in the outer chamber of the titration cell with using a temperature-controlled
bath, to heat the titration solvent.
(3) Start blanking to attain stable background.
(4) Put a sample container, powder funnel and spatula on the balance. Record its read (S1 [g]).
(5) Open the glass stopper of titration cell lid to introduce the sample with powder funnel as shown inFig.3.4.
(6) Start titration. Measurement parameter is shown in Table 4.2.
(7) Weigh the sample container, powder funnel and spatula again and record its read (S2 [g]). The
difference of (S1-S2 [g]) is set as sample size.
＊ If the sample adheres to the spatula or funnel, include these in the tare of balance.

Fig.3.4 Introduction of sample with powder funnel

4. Parameters and results
Table 4.1 Parameters of factor standardization

Table 4.2 Parameters of sample measurement

Item
Cal ModeItem
Cal Mode

8:KF Factor(By Standard)Interval Time
30 secMax Volume
20 mL
Min Feed Vol.
0.01 mL
S.Timer0 min
KF Buret No.
1STD H2O Conc.
1.000 %KF Speed(OUT)
24 mL/min
KF Speed(IN)24 mL/min
Back Ground
ONSample Size Input
Every TimeBlank Value
0 mL
E.P Detection
mVSolvent
FMC.P Level
150 mV
E.P Level
4Auto Interval
0 gAuto Input
OFFInterval Time
Max Volume
Min Feed Vol.
S.Timer
KF Factor
KF Buret No.
KF Speed(OUT)
KF Speed(IN)Back Ground
Sample Size Input
Blank Value
Unit ModeE.P Detection
Solvent
C.P Level
E.P Level
Auto Interval

0:Sample weight (net)
30 sec20 mL
0.01 mL
10 min1.0853 mg/mL
124 mL/min
24 mL/minONEvery Time
0 mL
AUTOmV
FM
150 mV40 g

Table 4.3 Results of factor standardization

SampleWaterstandard
10 mg/g

SampleGranulatedsugar

5. NoteMeas.
No.
12345Sample
size(g)
0.87491.09431.06971.0814
1.0263BG(mL)
0.020
0.036
0.052
0.054
0.050

Titrant
volume(mL)
8.13
10.11
9.87
9.97
9.54

Factor(mg/mL)1.07881.08631.08951.09061.0815

Statistic result
Avg.
SDRSD

1.0853 mg/mL
0.0051 mg/mL
0.47 %

Table 4.4 Results of water content measurement in granulated sugar
SampleTitrant
Water
Meas.
BG
Water
size
volumecontent
Statistic result
No.
(mL)
(mg)
(g)
(mL)
(ppm)
1
3.1130 0.096
0.81
0.775
249.0 Avg.
239.2 ppm
2
3.1342 0.130
0.81
0.738
235.5 SD
9.2 ppm
3
3.1568 0.119
0.82
0.761
241.1 RSD
3.86 %
46.2303 0.121
1.48
1.475
236.7
56.2351 0.132
1.56
1.550
248.6
66.2127 0.136
1.42
1.394
224.4

(1) The blanking might become unstable when time has passed since the solvents of methanol andformamide were mixed. The cause could be due to the ammonia generated by mixing these solvents.
Adding 3 g of benzoic acid to 50 mL of the titration solvent improves the unstable state of blanking.
(2) In the measurement of granulated sugar, the dissolution time of the sample was set to 10 minutes in theparameter “S-Timer”. If the sample becomes difficult to dissolve due to repeated measurements,replace it with a new solvent. In this report, the titration solvent was replaced with a new one every 3
sample measurements.
(3) In the measurement of this report, the measurement condition “Background” is set to ON forbackground correction. The background is the consumed volume of KF titrant to keep the titrant
solvent anhydrous during blanking. With this function, the amount of titrant consumed by thebackground is subtracted from the measurement result.
The reasons for using the background correction in this report are as follows:
In the measurement of this report, the experimental conditions are such that the blanking is relatively
less stable than in the normal measurement, and about 0.01 mL/min of KF titrant is consumed inblanking. This is due to the following experimental conditions.
(i) Low factor of KF titrant(ii) Formamide-containing titration solvent(iii) Heating of titration solvent
Since one measurement takes about 10 minutes to measure the sample, the volume of KF titrant
consumed to maintain the anhydrous state during the measurement is about 0.1 mL. The amount of KF
titrant consumed by sample measurement is approximately 1 mL, and the background has a large effecton the measurement results, so the correction is required.
Keywords：Karl Fischer, Volumetric titration, Granulated sugar, Formamide, Heating