HIRANUMA APPLICATION DATA

Watercontents

Karl Fischer Titrator

Data No. KF22

Apr. 13,2022

Drugs and Medicines – KF Volumetry Back-Titration
Japanese Pharmacopoeia – Suitability test

1. Abstract
Water contents of drugs and medicines could be determined by Karl Fischer volumetric titrator. In
volumetric titration, the titrant have a factor which means the ability to react with how many milligrams ofwater per 1 mL of titrant. Factor is pre-determined before sample measurement and water content of sample iscalculated from consumed titrant volume within sample measurement.
There are two methods in KF volumetric titration, forward-titration and back-titration. Forward-titration isused in general. However, some of the sample should be measured by back-titration method according toPharmacopeias.
In this report, the suitability test of Japanese Pharmacopoeia Eighteenth Edition was performed for
dextromethorphan hydrobromide monohydrate, also introduced in Application Data No. 11, with back -titration
method. Please refer to Application Data No. 11 for the factor determination of titrants procedure and therepeatability of measurement results for dextromethorphan hydrobromide monohydrate.
Reference
1) Japanese Pharmacopoeia Eighteenth Edition

2. Apparatus and Reagents(1) Apparatus
Titrator：

Karl Fischer Volumetric titrator

Additional Buret：

1 unitTitration cell：Standard cell without drain valve

Sampler：

Syringe

AQV-series

Powder funnel (Outer diameter of leg less than 12 mm)(2) ReagentsKF Titrant：

AQUALYTE KF3 (HIRANUMA)
An alternative if it is difficult to prepare
HYDRANAL Composit 5 (Honeywell)

Water-in-methanol solution：

2 mg/mL, prepared from reagent grade methanol and DI water：HYDRANAL Methanol Dry (Honeywell)

Measurement sample：

Dextromethorphan Hydrobromide Monohydrate (Guaranteed reagent)Standard material：

AQUALYTE Water Standard 10 (Assay: 10.06 mg/g, HIRANUMA)

Titration solvent(3) Sample

An alternative if it is difficult to prepare
HYDRANAL Water Standard 10 (Honeywell)3. Procedure
3.1. Blank test measurement by forward-titration(1) Fill 40 mL of titration solvent into the titration cell.
(2) Start blanking to attain stable background.
(3) Open the stopper of titration cell lid and introduce the funnel. Without adding the sample, leave tostand for the same amount of time as it takes to add the sample in section 3.2, then attach the stopper.
(4) Start blank test with forward-titration. Measurement parameter is shown in Table 4.1.
(5) Set the result of titrant volume obtained in the blank test as the blank value for the measurement
conditions of the sample.
3.2. Procedure for suitability test
(1) Fill 40 mL of titration solvent into the titration cell.
(2) Start blanking to attain stable background.
(3) Put a sample container, powder funnel and spoon on the balance. Record its read (Size 1 [g]).
(4) Open the glass stopper of titration cell lid to introduce the sample with powder funnel as shown inFig.3.1. The addition amount is adjusted so that the detected water (mg) is within 5 to 30 mgH 2O.
(5) Start titration. First, 10 mL of KF titrant is dispensed into the cell and then titrated withwater-in-methanol solution. Measurement parameter is shown in Table 4.2. Set the factors determined
preliminarily for the KF titrant and the water-in-methanol solution.
(6) Weigh the sample container, powder funnel and spoon again and record its read (Size 2 [g]). The
difference of (Size 1-Size 2 [g]) is set as sample size.
(7) After measurement of the sample is finished, the device, setting parameters, and reagents are usedwithout change, and the water standard is measured subsequently. Wash the syringe with the water
standard and draw it into syringe. Then, weigh the syringe and record its read (Size 1 [g]).
(8) Open the glass stopper of titration cell lid to introduce the water standard. The injection amount isadjusted so that the detected water (mg) is 50 to 100 % of that of the sample measurement. Weigh thesyringe again (Size 2 [g]). The difference of (Size 1-Size 2 [g]) is set as sample size.
(9) Repeat the measurement of the water standard 5 times.

Fig.3.1 Introduction of sample with powder funnel

3.3 Analysis of suitability test result(1) Prepare the value required for analysis from measurement result.
M: Determined water in the sample measurement result (mgH2O)⇒ Initial water content determined for sample (mgH2O)

M1-X: Amount of added water in the water standard measurement (mgH2O),“X” indicates the number of water standard measurement
Added amount of water standard (g) × Water assay of water standard (mgH 2O/g)⇒ Amount of water added (mgH2O)

M2-X: Amount of found water in the water standard measurement result (mgH2O),“X” indicates the number of water standard measurement⇒Amount of water found (mgH2O)(2) Plot as follows using spreadsheet software.
x-axisy-axis
M1-1
M + M 2-1
M1-1 + M 1-2
M + M 2-1 + M 2-2
M 1-1 + M 1-2 + M 1-3
M + M 2-1 + M 2-2 + M 2-3
M 1-1 + M 1-2 + M 1-3 + M 1-4
M + M 2-1 + M 2-2 + M 2-3 + M 2-4
M 1-1 + M 1-2 + M 1-3 + M 1-4 + M 1-5
M + M 2-1 + M 2-2 + M 2-3 + M 2-4 + M 2-5(3) Create a regression line for the plots and find the following values.
b : Slope of regression linea : y-axis interceptd : x-axis intercept(4) The percentage errors e1 (%) and e2 (%) are calculated from the following formulae.
e1 = {(a－M)／M} × 100
e2 = {(|d|－M)／M} × 100(5) From the following formula, calculate the water recovery rate r (%) for each of the 5 measurements ofthe water standard, and calculate the average water recovery rate R (%).
r (%) = (M2-X／M1-X) × 100

4. Parameters and results
Table 4.1 Parameters for blank test by forward-titration method
Item
Cal Mode
13:Auto input blank value mode
Interval Time
30 secMax Volume
20 mL
Min Feed Vol.
0.01 mL
S.Timer
0 min

Item
KF Buret No.
KF Speed(OUT)
KF Speed(IN)Back GroundE.P Detection
C.P Level
E.P Level
Auto Input

124 mL/min
24 mL/min
OFFuA
150 uA
200 uAOFF

Table 4.2 Parameters for sample measurement by back-titration method
Item
Cal Mode
11:Back tit1(Fixed KFreagent disp)
Interval Time
30 secMax Volume
20 mL
Min Feed Vol.
0.01 mL
S.Timer
1 min
KF Factor
2.9263 mg/mL
KF Buret No.
1
KF Disp.Vol.
10 mL
KF Timer
1 min
MeOH Factor
2.0279 mg/mL
MeOH Buret No.
2
MeOH Disp.Vol.
0 mL
MeOH Timer
0 min

Item
KF Speed(OUT)
24 mL/min
KF Speed(IN)24 mL/min
MeOH Speed(OUT)
24 mL/min
MeOH Speed(IN)24 mL/min
Back Ground
OFFSample Size Input Every TimeBlank Value
0.01 mL
Unit Mode
AUTO
E.P Detection
uA
C.P Level
150 uA
E.P Level
200 uA
Auto Interval
0g

Fig.4.1 Measurement result of the sample

Fig.4.2 Example of measurement results of the water standard

Table 4.3 Results of suitability test procedure
Meas.
No.
12
1
1
2
3
4
5

SampleBlank test
SampleWater standard

Meas.
Time
0:00:40
0:00:36
0:07:33
0:10:54
0:14:20
0:17:54
0:20:48
0:21:16

SampleTitrant
size (g) volume (mL)
0.01
0.01
0.20569.43
0.770810.56
0.92489.82
0.877210.03
0.96009.61
0.9512
9.65

Water(mg)10.111
7.819
9.320
8.894
9.746
9.665

Water
Statistic resultcontent (%)
Avg.
0.01 mL
4.9178＊ M = 10.111 mg
1.0144Avg.
1.0135 %1.0078SD
0.0033 %1.0139RSD
0.32 %
1.0152
1.0161

Table 4.4 Values used for regression line of suitability test

SampleSampleWater
standard

Meas.
No.

Samplesize (g)Added water
M 1-X(mgH2 O)

Found water
M 2-X(mgH2 O)1123
45

0.20560.77080.92480.87720.96000.9512

7.754
9.303
8.825
9.658
9.569

10.111
7.819
9.320
8.894
9.746
9.665

x-axisCumulative
added water(mgH2 O)
7.754
17.05825.88235.54045.109y-axisM + Cumulative
found water(mgH2 O)
17.93027.25036.14445.89055.555

Fig.4.3 Result of calculated regression line

Percentage
recovery
r (%)

100.8
100.2
100.8
100.9
101.0

Table 4.5 Result of suitability test for Japanese Pharmacopoeia
ItemResultStandardCompliant

Found water of sample M (mgH2O)

10.1115～30 mgH2O

OK

Average percent recovery R (%)

100.7

97.5～102.5 %OKy-axis intercept a (mgH2O)

10.088--Slope of regression line b

1.008

0.975～1.025

OK

x-axis intercept d (mgH2O)-10.013--

Percentage error |e 1| (%)

0.2

2.5 % or lessOK

Percentage error |e 2| (%)

1.0

2.5 % or lessOK

5. NoteA few things note for performing the suitability test
(1) In the suitability test, it is necessary to measure the water standard 5 times in succession withoutchanging the titration solvent after measuring the sample. On the other hand, in back-titration, the KF
titrant is dispensed and then titrated with water-in-methanol solution, so the increased amount of liquidin the cell per measurement is larger than forward-titration. The upper limit of the liquid volume in thestandard cell is 150 mL. In this report, the titration solvent to be added to the cell at first was reduced
to 40 mL so that the upper limit of the liquid volume was not exceeded during the suitability test.
In the standard cell, the minimum amount of titration solvent to add at first is 30 mL. If the liquidvolume exceeds the upper limit of cell during suitability test, use an optional cell with a capacity of
200 mL (P/N: D327512-1 etc.).
(2) Since the water standard is a liquid, it is collected in a syringe and usually injected into the cellthrough a rubber septum. By injecting through a rubber septum, the liquid sample can be added without
the outside air introduced to the cell during the injection.
In this report, since the sample of dextromethorphan hydrobromide monohydrate is a solid state, it
requires to open the stopper of the cell for adding it. The method of adding the water standard in thesuitability test is also performed in same procedure with the sample.

Keywords：Karl Fischer, Volumetric titration, Back titration, Pharmacopeia, Suitability test, Dextromethorphanhydrobromide monohydrate,