| HIRANUMA APPLICATION DATA | Automatic Titrator | Data No. | C1 | Jun.30,2020 |
| Detergents・Bath additives・Cosmetics | Determination of anion surfactant in detergent |
1.Abstract
The determination method of anion surfactant uses a cation surfactant with an opposite charge as the titrant. 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 in detergent 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 electrode SU-091 Reference electrode RE-201Z |
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| (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 of sample 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
Examples of titration conditions
Measurement results
| Meas.No. | Size (g) | Titrant volume (mL) | Conc. (%) |
|---|---|---|---|
| 1 | 5.427 | 7.251 | |
| 2 | 4.9985 | 5.435 | 7.261 |
| 3 | 5.454 | 7.287 | |
| Statistic calculation |
Average | 7.27 % | |
| SD | 0.019 % | ||
| RSD | 0.26 % | ||
Examples of titration curve
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5. Note
(1) Electrode
Depending on the type of sample, as the titration progresses, deposits may form on the electrodes and the potential 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 with sodium 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.
