Determination of the pH in detergents and soaps (10 percent solution): Guide according to ASTM D1172 and ISO 4316
The pH value of detergents and soaps is a decisive quality parameter in terms of product performance and skin compatibility. The pH value of a detergent has a direct influence on the formation of foam, the dirt-dissolving power, the effect on textiles or surfaces and the compatibility with the skin of the consumer. Therefore, the pH determination of detergents and soaps is an indispensable part of routine quality control.
According to international standards, the pH value of detergents and soaps is usually measured using a 10 percent aqueous solution (10 g sample / 100 ml water). This concentration corresponds to the typical application conditions of the product and ensures comparable results between different products. In this article, we will explain how the pH determination is carried out with a 10 percent solution, which standards apply and which services Nano-Test offers in this area.
Why is a 10 percent solution used?
Detergent and soaps can be concentrated or viscous in their pure form so that pH measurement is not possible. In addition, the pH of the product may change when diluted (especially with low buffering capacity formulations). Therefore, the norms stipulate that the measurement is carried out at a certain dilution ratio.
A 10 percent solution is the most widely used reference concentration in the industry. This ratio offers both a scenario close to the practical application of the product and improved reproducibility between different laboratories. Especially with soaps, problems such as increased viscosity and clogging of the electrodes can occur at high concentrations, which is why a 10 percent dilution ensures optimal measurement conditions.
Relevant International Norms
The most important standards used as a reference for pH determination in detergents and soaps are as follows:
| Standard | Title | Scope |
|---|---|---|
| ASTM D1172 | Standard Guide for PH of Queous Solutions of Soaps and Detergents | Standard Guide to the Preparation and PH Determination of Aqueous Solutions of Soaps and Detergents |
| ISO 4316 | Surfactants - Determination of the pH of aqueous solutions - Potentiometric method | Determination of the pH of aqueous surfactant solutions by potentiometric method |
| TS 6365 EN 1262 | Surfactants – pH determination | Turkish standard for pH determination in surfactants |
| GB/T 13531.1 | pH determination in cosmetics/detergents | Chinese standard for pH determination in cosmetics and detergents |
ASTM D1172 describes in detail the preparation methods for soaps and detergents, while ISO 4316 defines the framework for the potentiometric method applicable to all products with surfactants.
Method for pH determination with a 10 percent solution
The procedure carried out in accordance with ASTM D1172 and ISO 4316 includes the following steps:
1. Sample Preparation and Production of the Solution
- Weighing: 10 ± 0.05 g of the sample is weighed on an analysis scale.
- Dissolve: The sample is transferred to a 100 ml Erlenmeyer flask and filled with approx. 60-70 ml Carbon dioxide-free pure water.
- Mixing: The sample is mixed on a magnetic stirrer or in an ultrasonic bath until completely dissolved. If necessary, a slight heating (40°C maximum) can be done.
- Fill: After the solution has cooled to room temperature, it is filled to 100 ml with pure water.
2. Calibration of the pH meter
- The pH meter is calibrated with at least two-point calibration before measurement.
- As a rule, PH-4.00-, 7.00- and 10.00- buffer solutions are used for the calibration.
- Calibration must be done at measuring temperature (usually 25 ± 1 °C).
- The glass electrode is rinsed with pure water before and after calibration and slightly dabbed (not rubbed) with blotting paper.
3. Measurement
- The 10 percent solution produced is transferred to a clean beaker.
- The pH electrode is immersed in the solution and gently stirred with a magnetic stirrer.
- You wait until the value has stabilized (usually 30-60 seconds).
- The result is recorded with an accuracy of 0.1 pH units.
- The measurement is repeated at least twice and the mean of the results is formed.
4. Temperature Correction
The pH measurement depends on the temperature. ASTM D1172 and ISO 4316 recommend the measurement at 25 ± 1 °C. The temperature difference is automatically corrected when using pH meters with automatic temperature compensation (ATC).
Expected pH ranges depending on product type
The pH values of detergents and soaps vary depending on the intended use:
| Product type | Typical pH range (10% solution) | Scope of application |
|---|---|---|
| Solid Soap (Classic) | 9,0 – 10,5 | Hand and Body Cleaning |
| Liquid soap | 5,5 – 8,5 | Hand cleansing, for sensitive skin |
| Shampoo (baby) | 5,5 – 7,0 | Eye-friendly, gentle formula |
| Detergent | 9,0 – 11,0 | Textile cleaning, dirt solution |
| Dishwashing liquid | 7,0 – 9,0 | Fat solution, contact with hands |
| Surface cleaner | 10,0 – 12,0 | Industrial cleaning, disinfection |
GLP compliant pH determination services with nano test
For manufacturers of cleaning agents and soaps, the pH determination forms the basis for both the product quality and the compliance with legal regulations. Nano-Test is a reliable solution partner for the detergent industry with its GLP-compliant analysis services in this area.
Description of Nano-Test Services
NANO-TEST offers the PH determination service for washing and soap products with a 10 percent solution. Our analyzes are carried out in full compliance with the ASTM D1172, ISO 4316 and TS 6365 EN 1262 standards.
Our service process:
- Sample preparation: Weigh, dissolve and dilute according to ASTM D1172.
- Potentiometric measurement: Measurement with high-precision pH meters and calibrated electrodes.
- Calibration: Two- or three-point calibration with certified buffer solutions.
- Temperature Control: Measurement at 25 ± 1°C, automatic temperature compensation.
- Report: Measurement results are provided along with standard deviation and repeatability data.
All of our analyzes are presented as GLP-compliant reports that have a test approval and where data integrity (ALCOA+ principles) is guaranteed.
Advantages of the Nano-Test pH determination service:
- Accredited infrastructure: Internationally recognized test reports with ISO/IEC 17025 accreditation.
- Standard conformity: Complete conformity with ASTM D1172, ISO 4316 and the corresponding national standards.
- Fast Results: Reporting within 2-3 business days for standard pH analyses.
- Comprehensive Scope: All product types including solid soap, liquid soap, shampoo, detergent and surface cleaner.
- Specialist team: A team with experience in analytical chemistry and the legal regulations for cleaning products.
The pH determination of detergents and cleaning agents is a decisive step of quality control for the performance, stability and skin compatibility of the product. Potentiometric measurement with a 10 percent solution delivers internationally recognized, reliable results when performed in accordance with ASTM D1172 and ISO 4316 standards.
With its accredited laboratory infrastructure, its specialist staff and its GLP-compliant processes, NANO-TEST comprehensively meets the requirements of detergent and soap manufacturers for pH determination. Collaborate with Nano-Test to increase the quality of your products and accelerate their market launch.