HIRANUMA APPLICATION DATA

Detergents・Bath additives・
Cosmetics

Automatic Titrator

Data No.

C1

Jun. 30,
2020

Determination of anion surfactant
in detergent

1. Abstract
The determination method of anion surfactant uses a cation surfactant, with an opposite charge, as thetitrant. The end point is the point at which the charge becomes neutral due to the reaction between the anion
and the cation. Benzethonium chloride is used as the cation standard solution.
This report introduces an example of determination of anion surfactant, sodium alkylbenzene sulfonate, indetergent by potentiometric titration using a surfactant electrode as an indicator electrode.

2. Configuration of instruments and reagents(1) Configuration of instruments
Main unit:

Hiranuma Automatic Titrator COM series

Electrodes:

Surfactant electrodeSU-091

Reference electrodeRE-201Z(2) Reagents
Titrant:

0.004 mol/L Benzethonium chloride standard solution
Dissolve 0.896 g of benzethonium chloride in DI water and prepare
500 mL solution.

3. Measurement procedure(1) Take 5 g of sample and accurately weigh it then record the reading of balance.
(2) Dissolve the sample with DI water and transfer into 500 mL volumetric flask to prepare 500 mL ofsample solution.
(3) Take 10 mL of sample solution into 100 mL beaker with volumetric pipette.
(4) Add 50 mL of DI water.
(5) Immerse electrodes and start titration with 0.004 mol/L benzethonium chloride standard solution.

4. Measurement conditions and results
Example of titration condition
Cndt No.
MethodBuret No.
Amp No.
D. Unit
S-Timer
C.P. mLT Timer
D.P. mLEnd Sens
Over mL
Max.Vol.

1Auto12mV
300001000.5
10secmLsec
mL
mL
mL

Constant No.
SizeBlank
Molarity
Factor
K ※1L ※2

14.9985 g0 mL
0.004 mol/L
0.9595348
0.02Mode No.
Pre Int
Del KDel Sens
Int TimeInt Sens
Brt Speed
Pulse

210
5010
3240

sec
mV
sec
mV

Unit%
Formula(D-B)*K*F*M/(S*L*10)
Digits3※1 Set the molecular weight "348" for coefficient K to convert it as concentration of sodium dodecylbenzene
sulfonate.
※2 Dilution ratio of sample solution. Prepare 500 mL of sample solution with dissolving 5 g of sample and take 10mL aliquot of prepared solution.

Measurement results

Meas.
No.

Size(g)12
3

Example of titration curve

4.9985

Titrant
volume (mL)

Conc.
(%)

Statistic calculation

5.427

7.251

Avg.

7.27%

5.435

7.261

SD

0.019

%

5.454

7.287

RSD

0.26%

5. Note(1) Electrode
Depending on the type of sample, as the titration progresses, deposits may form on the electrodes and thepotential may become unstable. In that case, it is effective to reduce the sampling amount in order to suppress
the generation of deposits on the electrode.
(2) Standardization of benzethonium chloride
Standardizing the benzethonium chloride standard solution enables more accurate measurement. The
standardization method for benzethonium chloride is described below. The procedure is to standardize it withsodium dodecyl sulfate as a standard solution, whose purity was previously determined by neutralization
titration. (Refer to application data C11 for details of the standardization method)
Keywords: Anionic surfactant, Surfactant electrode, Sodium alkylbenzene sulfonate, Benzethonium chloride*Some measurement would not be possible depending on optional configuration of system.