The physicochemical parameters of a product, such as pH, viscosity, density and color, play an important role in the safety assessment of a product.

To obtain a detailed product specification report for conducting a safety assessment, several physicochemical laboratory tests are required. These tests provide information on the properties of the product and are used to assess the stability, safety and suitability of the product.

The analyses done for the product specification report, including the required sample sizes, are:

1. pH measurement

Purpose of test:
The pH value of a product indicates whether a formulation is acidic, neutral or basic. This is an essential parameter, especially for cosmetic and pharmaceutical products, as it affects skin compatibility and stability. Too high or too low a pH can cause skin irritation or affect the efficacy of active ingredients.

Test method:
The pH is measured with a calibrated pH meter, dissolving the sample in a suitable solution or diluting it if necessary. The test is performed according to standardized methods, such as ISO 4316 (for aqueous solutions) or ISO 787-9 (for suspensions and emulsions).

Why is it important?

• The pH determines the acidity or alkalinity of the product and affects skin compatibility.
• The wrong pH can lead to skin irritation, allergic reactions or disruption of the skin barrier.
• Products for the face and sensitive areas should be within a skin-friendly pH range (usually between 4.5 and 7.0).
• Extreme pH values (e.g., below 3.5 or above 8.5) may require additional toxicological evaluations.

Relevance to the CPSR:
The safety reviewer checks that the pH is appropriate for the intended use (e.g., facial care, body care or eye products) and compares it with scientific data on skin tolerance.

Sample amount required:
25 g/mL

2. Viscosity test

Purpose of Test:
The viscosity of a product determines how thick or thin it flows. It is critical for emulsions, gels, lotions and liquid products because it affects the application, use experience and stability of the product. Too high a viscosity can reduce lubricity, while too low a viscosity can lead to undesirable fluidity.

Test method:
Viscosity is measured using a viscometer, such as a rotational viscometer (e.g. Brookfield Viscometer) or a capillary viscometer, depending on the nature of the product. The measurement is carried out at a standardized temperature to minimize variability.

Why is it important?

• Viscosity determines the application and safety of the product.
• Too low viscosity can lead to uncontrolled application, for example, in eye creams or lotions, increasing the risk of irritation.
• Excessively high viscosity can affect the release behavior of active ingredients, thus affecting the product’s performance.
• Certain formulations require a specific viscosity to ensure stability and efficacy.

Relevance to the CPSR:
The safety assessor evaluates whether the viscosity corresponds to the product category and whether there are risks in normal use.

Sample amount needed:
100 g/mL

3. Density measurement

Purpose of Test:
The density of a product is defined as the mass per unit volume and is an important parameter for quality control and dosage calculations. It influences the choice of packaging and the distribution of the product in the bottle or tube. Density testing is especially relevant for liquid and semi-liquid formulations.

Testing method:
Density is determined by weighing a known volume of the sample at a controlled temperature. This is often performed using a pycnometer or a digital densitometer according to standardized methods such as ISO 2811-1.

Why is it important?

• The density helps determine the dosage amount per application, which is relevant for exposure calculations.
• It contributes to the stability assessment of the product. Changes in density may indicate phase separation or segregation.
• It influences packaging choices and may play a role in risk assessment of inhalation of fine sprays or aerosols.

Relevance to the CPSR:
The safety assessor uses the density value in exposure calculations to determine how much of a product gets onto the skin or into the respiratory tract and whether it is within safe limits.

Sample amount needed:
100 g/mL

4. Color Analysis

Purpose of Test:
The color of a product is an important parameter for aesthetics and brand consistency. Color analyses are performed to determine the exact hue, intensity and uniformity of a product to ensure batch consistency. Deviations in color may indicate instability or quality problems.

Testing method:
The color is analyzed with a spectrophotometer or colorimeter, which measures the reflection or transmission of light through the sample. This can be compared to a standard reference to ensure consistency.

Why is it important?

• Color consistency is an indicator of product stability. Discoloration may indicate oxidation or degradation of ingredients.
• It is relevant for the assessment of pigments and dyes, which are covered by specific regulations (e.g. approved CI numbers in Annex IV of EC 1223/2009).
• Undesirable color changes may indicate microbial growth or chemical degradation.

Relevance to the CPSR:
The safety reviewer verifies that the dyes used are safe and permitted and that no unexpected reactions occur during product storage that could compromise the safety of the product.

Sample amount needed:
50 g/mL