What Is pH?
pH determination measures the degree of acidity or alkalinity of a cosmetic product in an aqueous medium. For directly measurable products, the specimen is used as is; for solid or viscous products, measurement is made on a solution or suspension prepared with water at the ratio defined in the standard.
Purpose of pH
The purpose is to verify the product is within the target pH range for skin compatibility, stability and preservative efficacy. pH directly determines preservative effectiveness and is the earliest indicator of formulation degradation.
Which Products Is pH Applied To?
- Creams, lotions and emulsions
- Shampoos and shower gels
- Facial cleansing products
- Hair dye and styling products
- Oral care products
In Which Sectors Is pH Used?
Standards Related to pH
- TS EN ISO 4316 (surface active agents — determination of pH of aqueous solutions)
- ISO 18811 (parameters monitored in stability studies)
- TS EN ISO 22716 (good manufacturing practices)
pH Conditions
- Temperature
- Measurement temperature is recorded; pH depends on temperature
- Sample preparation
- Directly, or as an aqueous solution/suspension at the ratio defined in the standard
- Calibration
- Multi-point calibration with traceable buffer solutions before measurement
Equipment for pH
- pH meter and suitable electrode
- Certified buffer solutions
- Temperature probe
- Magnetic stirrer and analytical balance
Sample Requirements for pH
- A representative specimen; homogenisation is required for multi-phase products
- Specimen temperature must be equilibrated before measurement
- The measurement method (direct/solution) is determined by the formulation
- A separate specimen for each time point in a stability study
Duration of pH
The measurement itself is short and usually completed the same day. If monitored as part of a stability study, the duration depends on the study's schedule.
pH Procedure
- 1The pH meter is calibrated with traceable buffer solutions.
- 2The specimen is homogenised and its temperature equilibrated.
- 3For products that cannot be measured directly, a solution or suspension is prepared at the defined ratio.
- 4The electrode is immersed in the specimen and held until the reading stabilises.
- 5pH and measurement temperature are recorded together.
- 6The measurement is repeated and averaged.
pH Acceptance Criteria
The acceptance criterion is the pH range in the product specification. (EC) 1223/2009 also defines restrictions and warning requirements under Annex III for certain product types with high or low pH, such as hair straighteners and pre-waxing products.
Evaluation of Results
A pH value given without the measurement temperature is incomplete; the same product reads differently at a different temperature. In a stability study, the trend in pH is more informative than a single value: a steadily falling pH points to a chemical change in the formulation.
pH Report
- Specimen identification and preparation method
- Measurement temperature
- Calibration information
- Individual measurements and average pH
- Comparison against the specification range
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- (EC) 1223/2009 Cosmetic Products Regulation Annex III
Kozmetik Testleri — What Does This Testing Field Cover?
The section below describes the field that the pH test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Cosmetics testing shows that a product stays microbiologically safe throughout its use, delivers the performance it claims and contains no restricted substances. There is NO PRODUCT APPROVAL in this family: no authority approves a cosmetic product; responsibility rests entirely with the manufacturer and with the responsible person established in the EU.
This responsibility model shapes how the field works. Before the product is placed on the market a product information file (PIF) is prepared, a safety assessment (CPSR) is carried out and notification is completed. Inspection comes afterwards and asks for the file; if the file is incomplete the product is withdrawn from the market. Test reports form the evidence base of that file.
On the microbiological side there are two different questions and each is answered by a separate test. The CURRENT microbiological quality of the product is measured by enumeration and testing for specified microorganisms. The EFFECTIVENESS of the preservative system is examined by deliberately inoculating the product with microorganisms (challenge test): can the product resist repeated contamination throughout its use? A jar of cream is touched by a finger at every use; the preservative system must cope with that.
On the performance side, claim substantiation studies are carried out. For sunscreens, determination of SPF and UVA protection and measurement of water resistance are mandatory and are the basis of the value declared on the label. Evidence is also produced by in vivo or in vitro methods for claims such as moisturisation, appearance of wrinkles, hair care and colour retention.
On the chemical side, banned and restricted substances are screened: heavy metals, prohibited colorants, preservative concentrations, UV filter levels and contaminants such as nitrosamines. Products containing nanomaterials carry a separate notification obligation.
The BAN ON ANIMAL TESTING is the most defining constraint of the field. Animal testing cannot be carried out on finished products or ingredients, and a product tested on animals cannot be placed on the market. Alternative in vitro methods (reconstructed human skin models, cell culture based tests) are therefore at the centre of the field, and toxicological assessment rests largely on existing data, read-across approaches and in vitro results.
Stability and packaging compatibility studies determine shelf life and the period after opening (PAO). The interaction of the product with its packaging is also assessed: an active substance may migrate into the packaging, and substances that should not be present may pass from the packaging into the product.
On the process side, good manufacturing practice is demonstrated through ISO 22716; this is separate from product testing but a mandatory part of the file.
Method groups in this field
Microbiological quality
Enumeration of aerobic mesophilic bacteria, yeasts and moulds; testing for Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and E. coli.
Preservative efficacy
Resistance of the preservative system to repeated contamination by challenge test (ISO 11930).
Sun protection
In vivo SPF determination, in vitro UVA protection determination, water resistance and critical wavelength measurements.
Chemical analysis
Heavy metals, banned and restricted substances, quantification of preservatives and UV filters, contaminant screening.
Safety assessment
In vitro irritation and sensitisation methods, toxicological risk assessment, exposure calculations.
Stability and compatibility
Real-time and accelerated stability, packaging compatibility, PAO determination, sensory and physicochemical monitoring.
Commonly confused in this field
- There is NO CE marking on cosmetics; conformity is demonstrated through the PIF, the safety assessment and notification.
- The responsible person must be established in the EU; unless the exporter arranges this, the product cannot be placed on the market.
- Microbiological quality and preservative efficacy are different tests; a product that comes out clean may still have a weak preservative system.
- The animal testing ban covers ingredients too; animal test data generated for another market creates a problem of use.
- An SPF claim must be supported by measurement; a formulation change requires a new measurement.
- A change of packaging may require the stability and compatibility studies to be repeated.
Which decisions these results support
- The product information file and the safety assessment
- Verification of the preservative system design
- Substantiation of SPF and efficacy claims
- Determining shelf life and the period after opening
- Compliance with destination market restrictions for export
Related Tests
Frequently Asked Questions About pH
We heard skin pH is 5.5 — should our product match that?
Not necessarily. The skin surface is acidic and many care products are formulated close to it, but cleansers, hair products and some products with active ingredients are, by function, at a different pH. What matters is the product's safety and stability.
Is pH measured in oil-based products?
pH is not a meaningful parameter in water-free products and is not measured. In that case, stating the justification for not measuring it in the file is sufficient.